Article

Review of assistive strategies in powered lower-limb orthoses and exoskeletons

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Abstract

Starting from the early research in the 1960s, especially in the last two decades, orthoses and exoskeletons have been significantly developed. They are designed in different architectures to assist their users’ movements. The research literature has been more prolific on lower-limb devices: a main reason is that they address a basic but fundamental motion task, walking. Leg exoskeletons are simpler to design, compared to upper-limb counterparts, but still have particular cognitive and physical requirements from the emerging human–robot interaction systems. In the state of the art, different control strategies and approaches can be easily found: it is still a challenge to develop an assistive strategy which makes the exoskeleton supply efficient and natural assistance. So, this paper aims to provide a systematic overview of the assistive strategies utilized by active locomotion–augmentation orthoses and exoskeletons. Based on the literature collected from Web of Science and Scopus, we have studied the main robotic devices with a focus on the way they are controlled to deliver assistance; the relevant validations are as well investigated, in particular experimentations with human in the loop. Finally current trends and major challenges in the development of an assistive strategy are concluded and discussed.

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... In addition, they propose using this technology in a prototype orthosis called ATLAS, designed for children. The ATLAS device consists of two electric motors, four elastic elements (springs), linear rigid guides, adjustable rigid mechanisms, and torque sensors controlled by torque and position through a variable control (ARES) [23,[52][53][54]. ...
... tion, they propose using this technology in a prototype orthosis called ATLAS, designed for children. The ATLAS device consists of two electric motors, four elastic elements (springs), linear rigid guides, adjustable rigid mechanisms, and torque sensors controlled by torque and position through a variable control (ARES) [23,[52][53][54]. The same year proposed an active knee orthosis driven by a custom rotary serial elastic actuator (SEA). ...
... Torque and impedance controls are implemented to ensure safe patient interaction and enable new rehabilitation strategies. In addition, control algorithms have been built and implemented through the development of impedance control, which is integrated a PI position controller in cascade with the torque controller, where the external position controller determines the desired torque according to the position and velocity errors as well as the impedance parameters [23,[49][50][51][52][53][54]. Also, they have developed and used robust control algorithms applying PI, PD, PID control laws, or robust adaptive control algorithms to validate the feasibility of the orthosis and developed a fuzzy controller to perform walking assistance experiments [23,31,32,39,42,44,64]. ...
Article
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The use of specialized devices, such as orthopedic devices, has become indispensable in the lives of people with disabilities since ancient times. The primary purpose of such devices is to perform activities and solve problems that afflict their bearers in any extremity of their body. One of the most recurrent problems occurs in the lower extremities regarding mobility and autonomy. In addition, the use of orthopedic devices is considered a tool to lighten the repetitive and heavy rehabilitation work of physiotherapists while improving the patient’s recovery efficiency. A significant challenge is that a great variety of these devices are similar in their design and manufacture, complicating their application in rehabilitation processes. For these reasons, this article aims to provide an overview of the features and considerations made in the architecture of orthosis designs, emphasizing lower extremity orthoses for the case of knee joint analysis. A literature review of active and passive knee orthoses manufactured from the 1970s to the present was carried out, considering aspects such as manufacturing materials, mechanical systems, types of actuators, and control strategies. This review shows that the designs and development of orthoses have been abundant in these devices for lower limbs. Based on the literature collected, we have studied the main robotic devices focusing on the characteristics of design, manufacturing, and control systems to assist in human locomotion and support in rehabilitation processes.
... Exoskeleton control paradigms can be roughly divided into two categories: trajectory-based and trajectory-free approaches [8]. Trajectory-based control paradigms [9] track This work is supported by the South Carolina Translational Research Improving Musculoskeletal Health Faculty Development Award. ...
... glv@clemson.edu) (Corresponding author: Ge Lv) predefined kinematic trajectories, which does not encourage active user participation [8] nor promote user-friendly humanexoskeleton interaction [10] as individual's gaits are confined to specific patterns. Although some control paradigms are trajectory-free, they are specifically designed for dedicated tasks such as sit-to-stand [11] or stair ascent [12], where the proposed control methods cannot be easily translated into other locomotor tasks. ...
... As one example, human muscle activation can be measured via Electromyography (EMG) sensors and used as real-time sensory feedback for control design to assist a weak person's lower-limb motion or improve the accuracy of humanmachine interface [15]. However, performance of EMG sensors is suspectable to measurement noises, placement of electrodes, and sweating [8]. Energy shaping methods [16], [17] enable exoskeletons to provide task-invariant assistance by reducing the user's perceived body weight. ...
Conference Paper
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Task-invariant approaches are desirable in exoskeleton control design as they have the potential of providing consistent assistance across locomotor tasks. Different from traditional trajectory-tracking approaches that are specific to tasks and users, task-invariant control approaches do not replicate normative joint kinematics, which could eliminate the need for task detection and allow more flexibility for human users. In this paper, we propose a task-invariant control paradigm for lower-limb exoskeletons to alter the human user's centroidal momentum, i.e., a sum of projected limb momenta onto the human's center of mass. We design a virtual reference model based on human user's self-selected gaits to provide a reference centroidal momentum for the exoskeleton to track and make it adaptable to changes in gait patterns. Mathematically, the proposed approach reduces the control design problem into a lower-dimensional space. With the number of actuators being greater than the dimension of the centroidal momentum vector, we can guarantee the existence of a centroidal momentum shaping law for underactuated systems through optimization. Simulation results on a human-like biped show that the proposed shaping strategy can produce beneficial results on assisting human locomotion, such as metabolic cost reduction.
... Currently, robots are widely used in industrial automation [1], healthcare system [2], space exploration [3], agriculture [4], underwater exploration [5], food pre-post-processing applications [6], manufacturing technology [7,8], military application [9], human power assistance and rehabilitation applications [10][11][12]. Industry 4 Smart factory technology heavily relies on robots [13]. ...
... At any given moment the potential energy of a rigid body depends on its position Eqn. (10)- (11) and the kinetic energy of the rigid body depends on the velocity Eqn. (12)- (13). ...
... In Eqn. (11), is the total number of links. ...
Preprint
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For higher degrees of freedom robot, mass matrix, Coriolis and centrifugal force and gravity matrix are computationally heavy and require a long time to execute. Due to the sequential structure of the programs, multicore processors cannot boost performance. High processing power is required to maintain a higher sampling rate. Neural network-based control is a great approach for developing a parallel equivalent model of a sequential model. In this paper, Deep learning algorithm-based controller is designed for 7 degrees of freedom exoskeleton robot. A total of 49 densely connected neurons are arranged in four layers to estimate joint torque requirements for tracking trajectories. For training, the deep neural network analytical model-based data generation technique is presented. A PD controller is added to handle prediction errors. Since a deep learning network has a parallel structure, using a multicore CPU/GPU can significantly improve controller performance. Simulation results show very high trajectory tracking accuracies.
... The joint has many applications, such as in a bionic robot [1][2][3], robot arm [4][5][6] and assisted exoskeleton robot [7,8], etc. As the actuator, the robot joint is desired to have high torque output and low weight, thus high torque density is required. ...
... The teeth number and modulus should be determined considering the diameter. The relationship between teeth number, modulus and gear diameter is shown in Equations (6)- (8). ...
Article
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In many robotic applications, the joint is required to have a small volume, low weight and high torque output. In this paper, based on the finite element analysis (FEA), a 36-slot 40-pole outer rotor surface-mounted permanent magnet (OR-SPM) motor with concentrated winding is designed for the exoskeleton robot. The fractional slot concentrated winding (FSCW) is employed to reduce end winding height, leading better portability. Since the motor is relatively flat, the 3D end effect is critical to the electromagnetic performances. Special attention is paid to 3D end effect during the multi-objective optimization of the OR–SPM motor. In order to increase the ending torque output, the planetary reducer is located between OR–SPM motor and load, and then system level optimization covering motor and reducer is carried out to achieve best torque output. In addition, the force impendence control method with parameter self-adaptive capability is proposed to improve user experience of the exoskeleton robot, where the key parameters in the algorithm vary according to different actions of the exoskeleton. In addition, the inertia of load is calculated using the parameter identification based on least squares method. Finally, the prototype of the joint is fabricated and tested to validate the above FEA results and control method. The user experience of the exoskeleton robot is also covered.
... Based on the considered literature, physiological sensors are the sensor type less used for LM decoding. These results support the ones reported in [1,14,15]. Although EMG signals may allow recognizing the user's motion intention faster due to their anticipatory ability (about 100 ms before the muscle contraction [14]), EMG-based approaches have been left behind since EMG sensing is prone to fade during long-term use as a result of (i) movements between the skin and the electrodes; (ii) temperature variations; and (iii) sweating [7,12,13,32,33,55,56]. ...
... These phenomena can cause an incorrect identification of the user's LM. Moreover, according to [14,15], the use of EMG signals to decode LMs of pathological users (such as stroke patients) is prone to provide low accuracies due to the muscular activities of pathological users, which may vary across time and during the execution of the LMs as a result of fatigue. For this reason, the target population should be included during the algorithms' training [14]. ...
Article
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Understanding how to seamlessly adapt the assistance of lower-limb wearable assistive devices (active orthosis (AOs) and exoskeletons) to human locomotion modes (LMs) is challenging. Several algorithms and sensors have been explored to recognize and predict the users’ LMs. Nevertheless, it is not yet clear which are the most used and effective sensor and classifier configurations in AOs/exoskeletons and how these devices’ control is adapted according to the decoded LMs. To explore these aspects, we performed a systematic review by electronic search in Scopus and Web of Science databases, including published studies from 1 January 2010 to 31 August 2022. Sixteen studies were included and scored with 84.7 ± 8.7% quality. Decoding focused on level-ground walking along with ascent/descent stairs tasks performed by healthy subjects. Time-domain raw data from inertial measurement unit sensors were the most used data. Different classifiers were employed considering the LMs to decode (accuracy above 90% for all tasks). Five studies have adapted the assistance of AOs/exoskeletons attending to the decoded LM, in which only one study predicted the new LM before its occurrence. Future research is encouraged to develop decoding tools considering data from people with lower-limb impairments walking at self-selected speeds while performing daily LMs with AOs/exoskeletons.
... In general, lower limb exoskeletons with sensor-guided (user-volitional) control strategies are commonly designed to provide assistance at either the hip or the ankle joints [1]. Different exoskeleton control strategies exist, with the most common strategies employing either motion or torque-based control [2,3]. Torque-based control is the most common method for providing partial assistance to a user to improve performance during movement [3] and could be applied to compensate for changes in gait due to aging [4]. ...
... Lower limb exoskeletons might differ in their anticipated functional use, ranging from full movement support to negating the impact of heavy loads or providing targeted assistance. However, almost all functions provide a torque on the limb that is transferred from a motor to a joint in the body [2,3]. As the motors, power sources and attachments themselves can be heavy; an overarching design goal is that the exoskeleton be capable of offsetting the impact of its own added mass to the greatest extent possible [15,26]. ...
Article
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To improve exoskeleton designs, it is crucial to understand the effects of the placement of such added mass on a broad spectrum of users. Most prior studies on the effects of added mass on gait have analyzed young adults using discrete point analysis. This study quantifies the changes in gait characteristics of young and middle-aged adults in response to added mass across the whole gait cycle using statistical parametric mapping. Fourteen middle-aged and fourteen younger adults walked during 60 s treadmill trials under nine different loading conditions. The conditions represented full-factorial combinations of low (+3.6 lb), medium (+5.4 lb), and high (+10.8 lb) mass amounts at the thighs and pelvis. Joint kinematics, kinetics and muscle activations were evaluated. The young and middle-aged adults had different responses to added mass. Under pelvis loading, middle-aged adults did not adopt the same kinematic responses as younger adults. With thigh loading, middle-aged adults generally increased knee joint muscle activity around heel strike, which could have a negative impact on joint loading. Overall, as age may impact the user's response to an exoskeleton, designers should aim to include sensors to directly monitor user response and adaptive control approaches that account for these differences.
... Structured literature reviews inform identification of current limitations in service literature, and development of research agendas to facilitate future research within the field . Although multiple reviews of exoskeleton research have been conducted to date, these reviews focused upon users from clinical or non-role contexts , Hill et al., 2017, Yan et al., 2015 or addressed development of exoskeleton design, power and control mechanisms , Gopura et al., 2016, Yang et al., 2008. By contrast, this review will focus specifically on roles within a service value chain, in either a single-or multi-actor role context. ...
... Although multiple reviews of exoskeleton research have been conducted to date, these reviews focused upon users from clinical or non-role contexts , Hill et al., 2017, Yan et al., 2015 or addressed development of exoskeleton design, power and control mechanisms , Gopura et al., 2016, Yang et al., 2008. By contrast, this review will focus specifically on roles within a service value chain, in either a single-or multi-actor role context. ...
Article
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Purpose Exoskeletons are characterized as wearable, mechanical orthoses that augment the physical performance of the wearer, enhance productivity and employee well-being when used in value producing contexts. However, limited research involving exoskeleton usage by service employees in frontline contexts has been undertaken within service research. The purpose of this paper is to provide an overview of exoskeleton research undertaken within the context of value-producing roles, introduce exoskeletons conceptually to the service research domain, provide new conceptualizations of service exchange interactions involving physically augmented service actors and propose future avenues of exoskeleton research in alignment with key service theories. Design/methodology/approach A multi-disciplinary structured literature review based on the preferred reporting items for systematic reviews and meta-analyses method was undertaken across a variety of literature fields. A final selection of n = 25 papers was selected for analysis from an initial sample of N = 3,537. Given the emergent nature of exoskeleton research and the variety of methodology types used between literature fields, a thematic analysis approach was used for analysing identified papers. Findings The literature review identified four main themes within role-focused exoskeleton research. These themes informed proposals for future exoskeleton research with respect to key service theories and typologies. The findings demonstrate that the presence of an exoskeleton changes the behaviours and interactions of service employees. The augmented social presence AugSP typology is conceptualized to explain the influences of human enhancement technologies (HETs) within service actor interactions. Originality/value This research introduces the AugSP typology to conceptualize the impacts that exoskeletons and HETs impose within technologically mediated service interactions and provides a service-specific definition of exoskeleton technology to guide future service research involving the technology.
... Development in wearable powered exoskeletons offers a potential solution to traditional rehabilitation challenges [18,19]. An exoskeleton, also known as a wearable robot, is a mechanical system worn by humans to augment, complement or substitute the function of the wearer's limbs [20]. ...
Article
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Background Soft, wearable, powered exoskeletons are novel devices that may assist rehabilitation, allowing users to walk further or carry out activities of daily living. However, soft robotic exoskeletons, and the more commonly used rigid exoskeletons, are not widely adopted clinically. The available evidence highlights a disconnect between the needs of exoskeleton users and the engineers designing devices. This review aimed to explore the literature on physiotherapist and patient perspectives of the longer-standing, and therefore greater evidenced, rigid exoskeleton limitations. It then offered potential solutions to these limitations, including soft robotics, from an engineering standpoint. Methods A state-of-the-art review was carried out which included both qualitative and quantitative research papers regarding patient and/or physiotherapist perspectives of rigid exoskeletons. Papers were themed and themes formed the review’s framework. Results Six main themes regarding the limitations of soft exoskeletons were important to physiotherapists and patients: safety; a one-size-fits approach; ease of device use; weight and placement of device; cost of device; and, specific to patients only, appearance of the device. Potential soft-robotics solutions to address these limitations were offered, including compliant actuators, sensors, suit attachments fitting to user’s body, and the use of control algorithms. Conclusions It is evident that current exoskeletons are not meeting the needs of their users. Solutions to the limitations offered may inform device development. However, the solutions are not infallible and thus further research and development is required.
... This is the case of dynamic trajectory adjustments based on impedance control strategies [32]. Exhaustive reviews about control strategies used in assistance exoskeletons were presented in [33][34][35], where the use of predefined trajectories based on healthy people's gait was identified as a trend. ...
Article
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This paper presents a mechatronics design of a gait-assistance exoskeleton for therapy in children with Duchenne muscular dystrophy (DMD). This type of muscular dystrophy is a severe condition that causes muscle wasting, which results in a progressive loss of mobility. Clinical studies have shown the benefits of physical therapy in prolonging the mobility of patients with DMD. However, the therapy sessions are exhaustive activities executed by highly qualified rehabilitation personnel, which makes providing appropriate treatment for every patient difficult. This paper develops a mechatronics design of a gait-assistance exoskeleton to automate therapy sessions. The exoskeleton design uses adaptable mechanisms to adjust the device to the patient’s needs and includes the design of a series-elastic actuator to reduce the effects of nonalignment of the rotation axis between the exoskeleton and the patient. A mathematical dynamic hybrid model of the exoskeleton and a child’s body is developed using anthropometry of a population of six-year-old children. The hybrid model is used to design a nonlinear control strategy, which uses differential geometry to perform feedback linearization and to guarantee stable reference tracking. The proposed control law is numerically validated in a simulation to evaluate the control system’s performance and robustness under parameter variation during therapy with trajectory-tracking routines.
... Alternatively, passive designs, in which energy is collected and returned during the gait cycle, do not require any power source 45 . System-level advances in both exoskeleton types have led to their increased commercial presence, to informative clinical investigations and to a better understanding of how exoskeletons influence biological processes [46][47][48][49][50][51] . ...
Article
Exoskeletons can augment the performance of unimpaired users and restore movement in individuals with gait impairments. Knowledge of how users interact with wearable devices and of the physiology of locomotion have informed the design of rigid and soft exoskeletons that can specifically target a single joint or a single activity. In this Review, we highlight the main advances of the past two decades in exoskeleton technology and in the development of lower-extremity exoskeletons for locomotor assistance, discuss research needs for such wearable robots and the clinical requirements for exoskeleton-assisted gait rehabilitation, and outline the main clinical challenges and opportunities for exoskeleton technology. This Review highlights technological advances in exoskeleton technology from the past two decades, and challenges and opportunities in the exoskeleton-assisted rehabilitation of gait.
... The versatile hip exoskeleton is a typical type of versatile lower-limb exoskeleton that can enhance the capability of wearers in both cyclical locomotion (walking, running, upstairs, downstairs, etc.) and acyclic locomotion (sitting down, standing up, lifting, squatting, etc.) [2]. Numerous hip exoskeleton prototypes have been presented and refined [3]. ...
Article
Full-text available
An adaptive switching controller based on dynamic zero moment point for versatile hip exoskeleton is proposed in this work. The linear finite hysteretic state machine is designed to recognize hybrid motion phases. The torque planning strategy based on dynamic zero moment point is deployed to obtain assistant torque adaptively under different locomotion. Experiments are carried out to verify the performance of the controller, confirming the stability and accuracy of the motion phase recognition, which also demonstrates excellent kinematic performance. The net metabolic rate (NMR) can be reduced by 6.93% while wearing the versatile hip exoskeleton walking. The integrated surface electromyography (sEMG) can be reduced by 54.8% while wearing the exoskeleton lifting objects. Compared with existing research, the performance of the proposed controller has significant advantages. The proposed controller is capable of multiple types of locomotion including flat walking, stair climbing, and lifting heavy objects with low complexity and energy consumption.
... [2] The RoboKnee: an exoskeleton for enhancing ... [3] Clinical effectiveness and safety … [4] A review of lower limb exoskeleton assistive devices for sitto-stand and gait motion. [5] Review of assistive strategies ... [6] Handyman to hardiman. [7] Assistive devices of human knee joint. ...
... Several of these devices have been developed for different uses such as augmentation of human physical capabilities, gait rehabilitation, and walking assistance [1]. In the context of locomotion assistance, diverse control strategies have been implemented, with no real consensus towards the one that should be adopted [2]. Despite this variability in control approaches, the corresponding implementations can often be hierarchized in three levels: (i) the high-level layer determines the type of locomotion task (e.g. ...
Conference Paper
Lower-limb exoskeletons are robotic devices that can provide assistance to human locomotion. Since they are expected to be used in ecological environments, their control strategy should handle different kinds of daily-life situations. Taking inspiration from the human neuromuscular system – and particularly from the so-called motor primitives – may help in adapting the type of delivered assistance to different locomotion tasks. In this work, we validated the combination of simplified primitives and a musculoskeletal model for assisting healthy subjects with a hip exoskeleton. This framework showed adaptation to the user’s gait for different slope inclinations, although its effects on the subject’s speed and their perceived effort showed no significant improvement compared to wearing the device in transparent mode.
... Control strategy Yan et al. (2015) identiőed seven main control strategies implemented by full lower-limb exoskeletons, depending on their end application: ...
Thesis
In the recent years, advancements in robotics-related fields accompanied the development of exoskeletal devices that enhance the physical capabilities of the wearer, or assist impaired individuals in performing specific body movements. In particular, assistive lower-limb exoskeletons can be proposed to impaired people as a possible alternative to wheelchairs, or as rehabilitation medical devices. However, the intention detection interfaces are often based on basic solutions that lack intuitiveness, partly monopolize the use of hands, or prevent seamless transitions between the available activity modes. In this context, this doctoral work investigates natural and intuitive movement- based solutions to robustly detect motion intentions in a marketed assistive lower-limb exoskeleton. It focuses on walking-related intentions – namely gait initiation, gait termination, and steering – and evaluates novel implementations of high-level controllers based on acceleration and angular velocity signals recorded from upper-body-worn Inertial Measurement Units. Signals from these sensors can be analyzed, so that descriptive features of the exhibited movements are extracted, and serve as inputs to a classification architecture: they can either be compared to training data in a supervised learning approach, or to empirically derived thresholds. Experimental results of these algorithms indicate that the developed methods could be a viable alternative for intention detection in medical lower-limb exoskeletons, and could greatly enhance their usability.
... The cluster is guided by reviews on subjects including lower-limb robotics [44]; actuation, sensory, and control systems of lower-extremity exoskeletons and rehabilitation orthoses [45]; BMI training in chronic stroke patients [46]; and soft robotic gloves [47]. Among the top 15 most frequently cited articles, 12 focused on robotic exoskeletons and orthoses, and Yan [50] reviewed the assistive strategies utilized by active locomotion augmentation orthoses and exoskeletons; the other 3 studied mechanisms and control strategies for lower-limb rehabilitation [11,48,49]. ...
Article
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Rehabilitation robots, as representative advanced modern rehabilitation devices, are automatically operated machines used for improving the motor functions of patients. Research on rehabilitation robots is typically multidisciplinary research involving technical engineering, clinical medicine, neural science, and other disciplines. Understanding the emerging trends and high-impact publications is important for providing an overview of rehabilitation robot research for interested researchers. Bibliometric analysis is the use of statistical methods to analyze publications over a period of time, which can provide visual insights into the relationships between studies and their publications. In this study, we used “rehabilitation robot *” as a topic term to collect 3527 papers from Web of Science in 127 subject categories published between 2000 and 2019. Rehabilitation robot research has increased rapidly over the past 20 years, 10 key clusters of which were analyzed in this narrative review: improving functional ability after stroke, spinal cord injury, universal haptic drive, robotic-assisted treadmill therapy, treadmill training, increasing productivity, custom-designed haptic training, physical treatment strategies, arm movement therapy, and rehabilitation robotics. Based on this database, we constructed co-citation and co-occurrence networks that were characterized by betweenness centrality values of more than 0.08 and citation bursts with strengths of more than 23, thereby visualizing the emerging trends in the research of rehabilitation robots.
... √ [23] Control algorithms, mechanical architecture, sensors, control systems and validation with users of exoskeleton for people with lower-limb muscular weakness and disabilities. ...
Article
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Wearableassistive devices such as passive exoskeletonhavebeen recognized as one of the effective solutions to assist people inindustrialwork, rehabilitation, elderly care, military and sports. Thedesign and development of a passive exoskeletonthat emphasizes on satisfying and fulfilling users’ requirements and users’ experience areessential to ensure the device remains competitive in the global market. Agood user experience of using an exoskeletonstimulates users’ satisfaction, as contemporary users are not only considering basic functional features but alsofascinated by perception values such as aesthetics and enjoyment. Themain purpose of this article is to review the critical factors that are influencing user experience before, during and after utilizing a passive exoskeleton. The authors had searched relevant articles from academic databases such as Google Scholar, Scopus and Web of Science as well as free Google search for the publicationperiod from 2001to 2021. Several search keywords were used such as ‘passive exoskeleton +user experience’, ‘passive exoskeleton + industry’, ‘passive exoskeleton + rehabilitation’, ‘passive exoskeleton + military’, ‘passive exoskeleton + sports’,‘passive exoskeleton + sit-stand’, and passive exoskeleton + walking’. This online search found that a total of 236 articles related to the application of passive exoskeleton in the area of industry, rehabilitation, military and sports. Out of this, 81 articles were identified as significant references and examined thoroughly to prepare the essence of this paper. Based on thesearticles, the authors revealed that the engineering design, usability, flexibility, safety and ergonomics, aesthetics, accessibility, purchase cost, after-sales service and sustainability are the critical factorsthatare influencing user experience whenemployingpassive exoskeleton.
... Also, some lower limb exoskeletons and exosuits are designed for performance augmentation by providing loadcarrying capacity or assisting lower limb work [12][13][14]. These mentioned powered exoskeletons have been effective in clinical, industrial and military applications [15][16][17]; however, the main limitations are high cost, bulk, weight, and power demand (limited battery capacity and operation time) which limit their accessibility and usability for the general population. ...
Conference Paper
Mobility assistive devices, such as canes, crutches or walkers, are used to aid in the mobility of those affected by a lower limb impairment or disability. Although proven effective, the main shortcoming of these devices is the underutilization of lower limb muscles, which can decrease muscle mass and function of the lower limbs. Powered wearable devices for mobility assistance, such as exoskeletons or exosuits, have been developed and evolved over the past few decades; however, they are generally expensive, bulky, heavy, and power-demanding. A new approach to assist lower limb motions using upper limb muscles was conceptualized and tested using the Work-sharing of Upper Lower Limbs (WULL) device. This device creates external mechanical pathways to transfer upper limb joint motion or force to the lower limb joints. It provides a selfregulated and self-powered means to assist lower limbs during ambulatory movements using upper limb muscles. The experimental validation of the proposed concept was conducted through a pilot study which showed the kinematics coupling between the paired joints of upper and lower limbs, and the reduction in the lower limb muscle work (electromyography) during several ambulatory movements (e.g., sit to stand and step up) using upper limb muscles. The presented preliminary results support only the feasibility of the proposed concept (WULL), which warrants further investigation to validate its efficacy and effectiveness through a larger sample size study involving gait and identify optimal upper-lower limb joint pairing strategies.
... Fully powered exoskeletons provide external power for locomotion. Motion can be controlled based on impedance control to follow a predefined trajectory [76], [77], so even severely paralyzed patients with no residual function in the legs can use them for walking. For individuals with residual muscle function "assist as needed" control approaches are available [76]. ...
Thesis
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Mobility is a basic human need, and the ability to walk plays a key role. Unfortunately, this ability is severely limited for people with lower extremity impairments. While many still have the ability to walk in spite of muscular or neurological deficits, the effort required for walking, as well as the fear of falling, are often so dominant that bipedal locomotion is largely abandoned in everyday life. The vision of this work is to help mobilize these people in everyday life by intelligently redistributing the kinetic energy available from their residual muscle function, to enable safe and functional motion. In the present work, the following hypotheses were investigated: A modular, computer-controlled orthotic system provides functional support in mobility activities of daily life for people with lower limb impairments, without applying net positive power from external energy sources. Users will integrate such a system into their activities of daily life. By adding an energy-storing hip module, the user group for such a system can be extended to more severely affected people, who cannot benefit from a solution that only controls the knee joint. Energy recuperation at the hip joint will improve their ability to walk. A modular, computer-controlled orthotic system that brings a portion of these individuals closer to this vision is presented and evaluated. The development of the system was based on the assumption that, even without motor support, external energy sources or complex control algorithms, a high level of functionality can be achieved to support activities of daily life. Depending on their severity of muscular deficits, subjects were either stabilized solely by an orthosis with a computer-controlled knee joint, or if necessary additionally supported by a hip module. The goal of the fitting was to efficiently use the kinetic energy provided by the user, while ensuring the user is always the highest level control entity of the system. This can be achieved with a system behavior that is predictable for the user in every situation. Differences between individual users pose a major challenge in this regard. This includes both the different physiological conditions of the users, and the operating conditions for the support system, which depend on the daily habits of the individual users. Both aspects were considered in this work. Since the most important function of an orthotic knee joint is stabilization in stance phase, an adaptive damper was incorporated to control the knee joint. Hip musculature and hip motion play an essential role in forward propulsion during walking. Therefore, the possibility for elastic energy recuperation was provided by the hip joint, to ensure beneficial use of energy coming from the remaining musculature or from compensatory movements. Both components were evaluated with human subjects in clinical studies. In the case of the knee joint, an extended in-home use study was conducted, focused on the use of the system in everyday life, as well as the loads that occurred during this use. It was shown that the system was well accepted and used intensively by all subjects. The loads observed justify the robust design of the system. The control of the knee joint was perceived as intuitive, and seven out of eight users wanted to use the device in everyday life, even after the study. For the system that includes an additional hip joint, the focus was on determining energy storage characteristics, to ensure optimal energy recuperation for the user. For this purpose, data from several subjects using various systems with different energy storage properties were analyzed. Results showed significant adaptability by the test subjects. After a short familiarization phase, movement sequences were already adjusted to the different system properties, to ensure optimal use of the energy storage provided. For the hip joint control, good results were achieved with a simple control paradigm, in which the hip behaved like a spring with a variable neutral position. However, all users reported that the prototype hip joint used in the study was perceived as too large and heavy, and therefore not suitable for use in everyday life. In the course of the studies it was shown that through dissipative movement control of the knee joint by an adaptive damper, a significant improvement in function and an everyday benefit for the users could be achieved. The described knee joint system is now commercially available. The high adaptability of the subjects to different characteristics of the hip support system, as well as the functionality that could be achieved with a simple spring behavior, reveal potential for a simplified version of this system. Taking these findings into account for further development of the orthotic hip joint, it should also be possible in the future to provide high-quality functional care to people with severely limited hip function.
... Yan et al. [50] mentioned that a single-joint type can be divided into three groups, namely, hip, knee and ankle, which are used for specific individual parts. The functions of these joints are completely different [51]. ...
Article
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Lower extremity robotic exoskeletons (LEEX) can not only improve the ability of the human body but also provide healing treatment for people with lower extremity dysfunction. There are a wide range of application needs and development prospects in the military, industry, medical treatment, consumption and other fields, which has aroused widespread concern in society. This paper attempts to review LEEX technical development. First, the history of LEEX is briefly traced. Second, based on existing research, LEEX is classified according to auxiliary body parts, structural forms, functions and fields, and typical LEEX prototypes and products are introduced. Then, the latest key technologies are analyzed and summarized, and the research contents, such as bionic structure and driving characteristics, human–robot interaction (HRI) and intent-awareness, intelligent control strategy, and evaluation method of power-assisted walking efficiency, are described in detail. Finally, existing LEEX problems and challenges are analyzed, a future development trend is proposed, and a multidisciplinary development direction of the key technology is provided.
... Nota-se que há 38 patentes de "modelo de utilidade" dentre as 493 disponíveis sobre a tecnologia supracitada. A patente selecionada descreve um suporte para membros inferiores, que é um equipamento estratégico para a prevenção da úlceras por pressão (YAN et al., 2015), favorecendo uma recuperação mais rápida de pacientes que requerem um número aumentado de dias no leito, evitando ainda complicações importantes, como a Trombose Venosa Profunda (TVP), que pode levar ao surgimento do Tromboembolismo Pulmonar (TEP), que por sua vez se caracteriza como uma patologia com alto potencial de morbidade. Ademais, a tecnologia escolhida se trata de um modelo de utilidade de fácil replicação, de origem chinesa, publicada em 01 de janeiro de 2014, com proteção apenas na China, e livre para replicação no Brasil. ...
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As patentes, que trazem consigo a descrição de variadas tecnologias, são capazes de representar o status do desenvolvimento financeiro e tecnológico de uma nação. A utilização de informações patentárias ainda é incipiente no Brasil, e estes documentos praticamente não são utilizados para solucionar os problemas presentes na maioria das organizações. O foco do presente trabalho foi utilizar a ferramenta computacional Patent2net, um software livre de mineração de patentes, para extrair da base Espacenet documentos patentários para solução de problemas presentes no cotidiano do atendimento hospitalar. Neste experimento, foram eleitos quatro temas considerados de maior relevância para a maioria dos hospitais: 1 – dificuldades na execução do banho de pacientes acamados; 2 – problemas na realização de drenagem de conteúdo gástrico; 3 – elevada incidência de úlceras por pressão; 4 – dificuldades na realização da higiene oral de pacientes intubados ou com difícil acesso à cavidade oral. Buscou-se identificar patentes livres para reprodução no Brasil e com potencial de frugalidade, ou seja, inclusivas e com baixo custo de reprodução. Por meio deste estudo tecnométrico, foram identificadas patentes que podem auxiliar no atendimento de pacientes que apresentam as necessidades listadas, alocados em unidades críticas de centros hospitalares.
... Due to the underdevelopment of sensing, material and control technologies, the idea of exoskeleton did not attract too much attentions before 2000, but the latest two decades witnessed a vigorous growth in the studies of exoskeleton [6]. Depending on the assistive strategy, exoskeletons may actuate single or multiple joints, including specific joints, upper and lower extremities, or even a full body [7]. More specifically for assisting lower limb locomotion, many famous exoskeletons, such as BLEEX [8] and HULC [9] for strength augmentation, LOPES [10] and C-ALEX [11] for patient rehabilitation, and ReWalk [12] and HAL [13] for locomotion assistance, have been proposed. ...
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Exoskeleton is a promising technology to enhance the mobility of aged and disabled people. With comfortable human–exoskeleton interaction, mechanical and control designers aim at accurately tracking a desired trajectory, while saving the wearer’s energy expenditure is the preference from the viewpoint of biomechanics. Given all of these effects, we propose a new model, consisting of the swing dynamics of both human and robot’s lower extremities coupled by damped springs representing elastic and viscous properties of band and human tissue. With the coupling coefficients identified with an experimental platform, the analytical model yields consistent results compared with an experimental exoskeleton, especially in the prediction of the interactive forces. Further analyses are then performed based on this validated model, revealing the influences of desired trajectory, mass ratio, misalignment, coupling points, health condition and band tightness on the human–exoskeleton coupling dynamics. It is found that introducing gravity compensation and tuning the feedback gain improve the tracking accuracy, but hardly change the interactive force. The most comfortable interaction requires a healthy wearer coupled with a lightweight exoskeleton without any misalignment, but properly changing the trajectory, coupling points and tightness can partly reduce the interactive forces if the ideal condition is unachievable.
... Control strategies are crucial to the efficacy of assistive devices [7]. Imposing a predefined trajectory using a trajectory controller can suppress the user's motor contributions which is shown to be disruptive to the motor rehabilitation of individuals who can still partially contribute to the motion [8]. ...
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An ultra-robust accurate gait phase estimator is developed by training a time-delay neural network (D67) on data collected from the hip and knee joint angles of 14 participants walking on a treadmill and overground. Collected data include normal gait at speeds ranging from 0.1m/s to 1.9m/s and conditions such as long stride, short stride, asymmetric walking, stop-start, and abrupt speed changes. Spatial analysis of our method indicates an average RMSE of 1.74±0.23% and 2.35±0.52% of gait phase on test participants in the treadmill and overground walking, respectively. The temporal analysis reveals that D67 detects heel-strike events with an average MAE of 1.70±0.54% and 2.74±0.92% of step duration on test participants in the treadmill and overground walking, respectively. Both spatial and temporal performances are uniform across participants and gait conditions. Further analyses indicate the robustness of the D67 to smooth and abrupt speed changes, limping, variation of stride length, and sudden start or stop of walking. The performance of the D67 is also compared to the state-of-the-art techniques confirming the superior and comparable performance of the D67 to techniques without and with a ground contact sensor, respectively. The estimator is finally tested on a participant walking with an active exoskeleton, demonstrating the robustness of D67 in interaction with an exoskeleton without being trained on any data from the test subject with or without an exoskeleton.
... The joint needs the high torque and slow velocity of the hip flexion/extension (HFE) joints during sitting-to-standing, whereas it needs a high velocity with small torque for walking and running [12,13]. To satisfy the requirement of high torque This work was supported in part by the National Key R&D Program of China (2020YFC2007804), the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (19KJA180009), the Natural Science Foundation of Jiangsu Province (BK20191424), the Jiangsu Frontier Leading assistance for sitting-to-standing, most exoskeletons have been designed using high-reduce radio transmission or high-power motors [14][15][16]. This design will inevitably increase the inertia and weight. ...
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To overcome the different requirements of torque-velocity characteristics for walking, running, stand-to-sit, sit-to-stand, and climbing stairs, we propose a novel concept for actuator design, namely, a series elastic actuator with two-motor variable speed transmission. The two-motor variable speed transmission can be adjusted in real-time to realize variable torque-velocity characteristics. A novel lightweight wearable hip exoskeleton driven by a series elastic actuator with two-motor variable speed transmission, named SoochowExo, has been developed in this paper for use in the elderly population. The weight of the whole hip exoskeleton is 2.85 kg (excluding batteries), including two actuators and the frame. The proposed hip exoskeleton can match the weight of the state-of-the-art hip exoskeleton while offering suitable torque and velocity for sitting-to-standing, walking, running on level ground, and climbing stairs. The benchtop tests and the preliminary human subject tests further confirm the design.
... Notice that this device is only a single example of several automatic mobilizing devices which can contribute to the continued rehabilitation of extremities [13,14]. ...
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Robot-assisted rehabilitation is an exciting field which aims to incorporate relevant developments in robotics related to rehabilitation with the intention of defining new methodologies for intervening problems related to muscular, neuromuscular, and osseous diseases. In this study, a systematic and comprehensive literature analysis is conducted to identify the contribution of artificial intelligence applied on robotic devices for motor rehabilitation, highlighting its relation with the rehabilitation cycle, and clarifying the prospective research directions in the development of more autonomous rehabilitation procedures. Considering this main goal, a summarized definition of general rehabilitation techniques is established. Then, such definition is particularized for technological-aided rehabilitating medical treatments implementing artificial intelligence methods, identifying the sections included within the process and the associated interaction degrees. This generic definition is analyzed using the current literature in muscle-skeletal treatment robotics as reference framework. This analysis considers the components and sections included in rehabilitation sequence. This review also describes a more in-depth description of the principal categories for classifying therapeutic robotic devices, including descriptions of the main past and present outcomes for each class of medical robotics for rehabilitation. The existing challenges and open options to develop more efficient autonomous (with the application of diverse artificial intelligence approaches) rehabilitating procedures are discoursed. Besides, taking into account this comprehensive review, a sequence of technical requires which must be taken into consideration when designing, developing and implementing autonomous robotic devices aimed to contribute to rehabilitation medical systems are deliberated. A brief description of the application of artificial intelligence and autonomous medical rehabilitation treatment is analyzed in terms of the exciting technical challenges and the ethical compromises that such a treatment option implies. © 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.
... Shi et al. [2] reviewed and critically evaluated the research progress in human gait analysis and systematically summarised developments in the mechanical design and control of lower limb rehabilitation exoskeleton robots. The advantages and disadvantages of the theory and technology used in prototypes and products have also been compared and summarised [16]. These reviews focused on the design and control of the systems; however, they did not provide much detail on human-robot coordinate control. ...
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As a wearable and intelligent system, a lower limb exoskeleton rehabilitation robot can provide auxiliary rehabilitation training for patients with lower limb walking impairment/loss and address the existing problem of insufficient medical resources. One of the main elements of such a human—robot coupling system is a control system to ensure human—robot coordination. This review aims to summarise the development of human—robot coordination control and the associated research achievements and provide insight into the research challenges in promoting innovative design in such control systems. The patients’ functional disorders and clinical rehabilitation needs regarding lower limbs are analysed in detail, forming the basis for the human—robot coordination of lower limb rehabilitation robots. Then, human—robot coordination is discussed in terms of three aspects: modelling, perception and control. Based on the reviewed research, the demand for robotic rehabilitation, modelling for human—robot coupling systems with new structures and assessment methods with different etiologies based on multi-mode sensors are discussed in detail, suggesting development directions of human—robot coordination and providing a reference for relevant research.
... The reason is that it limits the human's voluntary efforts and necessary gait variation for balance control [11]. For those who still have motor control ability, such as individuals post-stroke, torque or impedance/admittance control combined with a finite-state machine is commonly used [6], [12]. ...
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Powered exoskeletons are promising devices to improve the walking patterns of people with neurological impairments. Providing personalized external assistance though is challenging due to uncertainties and the time-varying nature of human-robot interaction. Recently, human-in-the-loop (HIL) optimization has been investigated for providing assistance to minimize energetic expenditure, usually quantified by metabolic cost. However, this full-body global effect evaluation may not directly reflect the local functions of the targeted joint(s). This makes it difficult to assess the direct effect when robotic assistance is provided. In addition, the HIL optimization method usually does not take into account local joint trajectories, a consideration that is important in imposing healthy joint movements and gait patterns for individuals with lower limb motor deficits. In this paper, we propose a model-free reinforcement learning (RL)-based control framework to achieve a normative range of motion and gait pattern of the hip joint during walking. Our RL-based control provides personalized assistance torque profile by heuristically manipulating three control parameters for hip flexion and extension, respectively, during walking. A least square policy iteration was devised to optimize a cost function associated with control efforts and hip joint trajectory errors by tuning the control parameters. To evaluate the performance of the design approach, a compression sleeve was used to constrain the hip joint of unimpaired human participants to simulate motor deficits. The proposed RL control successfully achieved the desired goal of enlarging the hip joint's range of motion in three participants walking on a treadmill.
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As a wearable robot, an exoskeleton provides a direct transfer of mechanical power to assist or augment the wearer’s movement with an anthropomorphic configuration. When an exoskeleton is used to facilitate the wearer’s movement, a motion generation process often plays an important role in high-level control. One of the main challenges in this area is to generate in real time a reference trajectory that is parallel with human intention and can adapt to different situations. In this paper, we first describe a novel motion modeling method based on probabilistic movement primitive (ProMP) for a lower limb exoskeleton, which is a new and powerful representative tool for generating motion trajectories. To adapt the trajectory to different situations when the exoskeleton is used by different wearers, we propose a novel motion learning scheme based on black-box optimization (BBO) PIBB combined with ProMP. The motion model is first learned by ProMP offline, which can generate reference trajectories for use by exoskeleton controllers online. PIBB is adopted to learn and update the model for online trajectory generation, which provides the capability of adaptation of the system and eliminates the effects of uncertainties. Simulations and experiments involving six subjects using the lower limb exoskeleton HEXO demonstrate the effectiveness of the proposed methods.
Chapter
It is very important to improve the working stability and wearing comfort for the lower limb exoskeleton system, so as to increase the rehabilitation effect of patients with lower limb injuries. However, due to the complex structure of the lower limb exoskeleton, there are uncertain disturbances in the system. Traditional control methods cannot meet the requirements of dynamic response and robustness, since there are still many shortcomings in the safety and compliance of the lower limb exoskeleton for rehabilitation wearing. In this paper, an impedance synovial control strategy for the exoskeleton of the lower limbs is proposed. The safety of contact force is considered, and the impedance controller is combined with the improved integral terminal synovial controller (ITSMC) to reduce system’s errors, and to ensure system’s rapidity. The proposed method reduces the impedance trajectory tracking error by 90% to the conventional linear synovial control (LSMC). The stability is analyzed by a Lyapunov function. The simulation results show that the combination of the synovial controller and impedance controller has superior performances, and the entire system has a good trajectory tracking effect.KeywordsLower-limb exoskeletonImpedance controlSynovial controlTrajectory tracking
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Due to the ever-increasing proportion of older people in the total population and the growing awareness of the importance of protecting workers against physical overload during long-time hard work, the idea of supporting exoskeletons progressed from high-tech fiction to almost commercialized products within the last six decades. Sensors, as part of the perception layer, play a crucial role in enhancing the functionality of exoskeletons by providing as accurate real-time data as possible to generate reliable input data for the control layer. The result of the processed sensor data is the information about current limb position, movement intension, and needed support. With the help of this review article, we want to clarify which criteria for sensors used in exoskeletons are important and how standard sensor types, such as kinematic and kinetic sensors, are used in lower limb exoskeletons. We also want to outline the possibilities and limitations of special medical signal sensors detecting, e.g., brain or muscle signals to improve data perception at the human–machine interface. A topic-based literature and product research was done to gain the best possible overview of the newest developments, research results, and products in the field. The paper provides an extensive overview of sensor criteria that need to be considered for the use of sensors in exoskeletons, as well as a collection of sensors and their placement used in current exoskeleton products. Additionally, the article points out several types of sensors detecting physiological or environmental signals that might be beneficial for future exoskeleton developments.
Chapter
A key element of any mechatronics system is in its interaction with the environment within which it operates, and as such sensors and the processing of sensor data play a major role in the operation of such systems. Indeed, in many mechatronics applications from manufacturing to assistive technologies, and increasingly within EcoMechatronics, the role of the embedded sensors is key not only to the operation of an individual device, but also as a source of information impacting upon the wider environment within which that device is operating. In this chapter, the nature of sensing and sensor technology is considered in relation to mechatronic, and particularly EcoMechatronic, applications along with the means by which the resulting data may be analysed and interpreted, illustrated by examples drawn from wearable robotic technologies in particular.
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With the increase of the elderly population, the assistive technology for their walking has been needed. Although some walking support devices have shown positive effects, they still have problems for easy to suit it by oneself. In this study, it is aimed to develop a new walking assist device which can be used for hemiplegia and has feasibility of adjustment for assisting power without any actuators. As a first step, a motion transmission mechanism between lower limbs has been proposed and implemented as a prototype. The basic function and effects of motion transmission from unaffected side to affected side without any control are verified through the experiments using the prototype with a simple biped leg model. In addition, it is confirmed that the variation of attachment positions of transmission mechanism on the bipedal model offers the adjustability of transmitted torque. And, it is verified that the attachment of the proposed mechanism on the biped model has the positive effects on the periodicity and stability of the gait motion. As a future work, it is needed to redesign a motion transmission mechanism which suits for the actual human leg and its motion with the safety and the consideration for the load to the unaffected limb.
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Manually carrying loads for a long distance and duration is highly physically demanding for humans but commonly required in outdoor activities. With the rapid growth and advancement of wearable robotics, many explorations have been conducted to design and evaluate robotic systems, aiming to enhance human capacity and/or endurance in load carriage tasks. In this paper, state-of-the-art robotic load carriage assistive devices are systematically reviewed regarding the mechanisms and their performances in experimental evaluation. Methods and strategies of assisting load carriage are analyzed and the existing devices are categorized into four classes: (1) reducing inertial force of the load, (2) transferring load weight to the ground, (3) assisting human joints, and (4) integration of transferring load weight and assisting human joints. The efficacy of different mechanism designs and assisting strategies are discussed from both engineering and biomechanical perspectives. Based on these analyses, challenges in the current studies and further efforts required in developing better assistive devices are discussed to provide insights for future studies.
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Bowden-cable-actuated soft exoskeleton robots are known for their light weight and flexibility of power transmission during rehabilitation training or movement assistance for humans. However, friction-induced nonlinearity of the Bowden transmission cable and gearbox backlash pose great challenges forprecise tracking control of the exoskeleton robot. In this paper, we proposed the design of a learning-based repetitive controller which could compensate for the non-linearcable friction and gearbox backlash in an iterative manner. Unlike most of the previous control schemes, the presented controller does not require apriori knowledge or intensive modeling of the friction and backlash inside the exoskeleton transmission system. Instead, it uses the iterative learning control (ILC)to adaptively update the reference trajectory so that theoutput hysteresis caused by friction and backlashis minimized. In particular, a digital phase-lead compensator wasdesigned and integrated with the ILC to address the issue of backlash delay and improve the stability and tracking performance. Experimental results showed an average of seveniterations for the convergence of learningand a 91.1% reduction in the RMS tracking error (~1.37 deg) compared withthe conventional PD control. The proposed controller design offers promising options for the realization of lightweight, wearable exoskeletons with high tracking accuracies.
Conference Paper
An accurate real-time gait phase estimator for normal and asymmetric gait is developed by training and testing a time-delay neural network on gait data collected from six participants during treadmill walking. The trained model can generate smooth and highly accurate predictions of the gait phase with a root mean square error of less than 3.48% and 4.31% in normal and asymmetric gait, respectively. The coefficient of determination between the estimated and target phase is greater than 99% for all subjects with both normal and asymmetric gait. The proposed gait estimator also exhibits precise heel-strike event detection with an RMSE of 2.56% and 3.70% in normal and asymmetric gait, respectively. A spatial impedance controller is then employed and tested based on the estimated gait phase of a new participant. Obtained results confirm that the controller provided assistance in coordination with the user's motion both in normal and asymmetric gait conditions. The estimated gait phase is compared in the case of walking without and with the exoskeleton in passive and active modes, indicating persistent accuracy of the gait phase estimator regardless of the walking conditions.
Conference Paper
Volitional movement from users of assistive lower limb exoskeletons may be exploited to increase the controlled variability in the movements of a human-exoskeleton system. This may in turn allow these devices to handle the variability encountered in the terrain of everyday life. This study aimed to investigate the degree to which users can volitionally influence step length, when using an assistive exoskeleton designed for users with spinal cord injury (SCI) running a fixed robotic exoskeleton trajectory. An experiment was conducted to investigate the accessible range of step lengths when five able-bodied participants and one participant with SCI piloted a user-balanced exoskeleton. Participants were asked to take steps as large as possible ("large") and as small as possible ("small"), with the able-bodied individuals asked to minimise use of their leg muscles, with step length of each step measured. Surface electromyography (sEMG) data were collected on major leg muscles of the able-bodied subjects to monitor their muscle activities with a novel processing method introduced to facilitate discussion in the context of users with SCI. The results demonstrate that a user can intentionally manipulate the resulting step length, with every participant having significantly different large and small step sizes (p < 0.05). However, large variations were observed between individuals in terms of absolute step lengths and difference between large and small steps. Moreover, the range of step length (normalised by the leg length) ranged from 0.237 to 0.375 for the able-bodied subjects and 0.245 for the individual with SCI. Although positive correlation was present between the sEMG data and resulting step lengths, the result was not statistically significant (p > 0.05).
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In this paper, an active fault-tolerant control scheme is proposed for a lower limb exoskeleton, based on hybrid backstepping nonsingular fast terminal integral type sliding mode control and impedance control. To increase the robustness of the sliding mode controller and to eliminate the chattering, a nonsingular fast terminal integral type sliding surface is used, which ensures finite time convergence and high tracking accuracy. The backstepping term of this controller guarantees global stability based on Lyapunov stability criterion, and the impedance control reduces the interaction forces between the user and the robot. This controller employs a third order super twisting sliding mode observer for detecting, isolating ad estimating sensor and actuator faults. Motion stability based on zero moment point criterion is achieved by trajectory planning of waist joint. Furthermore, the highest level of stability, minimum error in tracking the desired joint trajectories, minimum interaction force between the user and the robot, and maximum system capability to handle the effect of faults are realized by optimizing the parameters of the desired trajectories, the controller and the observer, using harmony search algorithm. Simulation results for the proposed controller are compared with the results obtained from adaptive nonsingular fast terminal integral type sliding mode control, as well as conventional sliding mode control, which confirm the outperformance of the proposed control scheme.
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In this study, we focused on the design and control of a single DoF laterally supported knee exoskeleton robot designed to improve the load-carrying and strength capacity of healthy individuals, especially soldiers and workers. First, a nonlinear second-order differential model of the robotic knee orthosis was produced. Then, a single degree of freedom exoskeleton robot was designed and manufactured. An interactive motion control method based on the relative angle measurement principle between the knee joint of the user and the exo-suit knee joint was proposed. The user’s knee joint motion is detected via an IMU sensor, and a controller was provided to allow the exo-suit to track the human knee joint in synchrony. In this study, a conventional PID, SMC, and moving surface SMC controllers were designed, and the controllers’ performance were tested in real-time experiments. The maximum tracking errors in the PID, SMC, and MSMC controllers were 2.631 ∘ , 1.578 ∘ , and 1.289 ∘ , respectively, and the average tracking time errors were 0.10, 0.08, and 0.06 s, respectively. In addition, the designed and produced knee orthosis weighs 2.5 kg, making it one of the lightest and most compact designs for use by healthy individuals. The knee orthosis was made of steel, and thus it is very durable for use in all kinds of terrain conditions (military, industrial, etc.). Experimental findings about the proposed design and control method are analyzed in the results and discussion section.
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Even with proper lifting techniques, fatigue can cause many debilitating injuries. Exoskeleton lumbar support devices help prevent these injuries for workers and improve their overall performance. In this article, we present a study on the performance of a semiactive lower back support exoskeleton. The device is powered by a spring–damper mechanism that utilizes a magnetorheological fluid to add a resistive force to the hip joint. The braking force of the device showed a range between 100 and 900 N depending on the compression stroke, coil current, and actuation speed. Muscle activation of the latissimus dorsi, erector spinae, and gluteus maximus was reduced. The analysis based on a biomechanical model showed a power reduction of 40% at the hip joint in the bending phase, and a total reduction of 20% during the entire lifting cycle. The automatic control system using only embedded sensors showed successful and stable functioning but had excessive delays in the activation of the device.
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Reference trajectory generation and trajectory tracking in the presence of uncertainties and disturbances are among the most challenging topics in the realm of exoskeletons. Central pattern generation (CPG) is one of the trajectory design methods for walking robots, which acts as a limit cycle and produces smooth and rhythmic trajectories by rapid cancelation of the effects of exogenous disturbances. In this paper, the reference trajectories of robot joints are designed by combining modified Hopfield oscillators, which allows adjusting the frequency and amplitude of walking. For online modification of the reference joint trajectories, feedback error signal from zero-moment point (ZMP) criterion and error signal of impedance filter are used. To counteract the adverse effects of uncertainties and exogenous disturbances and to achieve high trajectory tracking performance, dynamic adaptive fast terminal sliding mode control strategy (DAFTSMC) is applied, which provides chattering-free control signals and demonstrates finite-time convergence rate, as well as high robustness against uncertainties and disturbances with unknown range. Moreover, the robot’s maximum walking stability based on the ZMP criterion is achieved through the proper movement of the waist joint. Additionally, control parameters, oscillator gains, and their connections are optimized to ensure the highest performance. Finally, the performance of the proposed method is compared with two other control schemes: conventional sliding mode control (SMC) and CPG-based hybrid SMC. The obtained results show the superiority of the proposed approach.
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Lower limb exoskeletons (LLE) have been successfully used in robotic-assisted rehabilitation to reduce the burden of locomotor impairment of disabled people. However, the design limitations of LLE mechanisms, such as the lack of kinematic compatibility relative to the user’s joints and the use of high stiff or heavy actuators, limit the outcomes of treatment and increase the risk of injury. To address these shortcomings, in this work we present the design of the MRKneeExo, a highly backdrivable and kinematically compatible active knee exoskeleton. The powertrain of the system is composed of a BLDC 70 W motor associated with a harmonic drive gearbox and a customized magneto-rheological (MR) clutch. To improve kinematic compatibility with the user’s knee, a crossed four-bar linkage mechanism (FBLM) was optimally designed to follow the trajectory of the instant center of rotation (ICR) of the knee projected in the parasagittal plane where the joint is placed. The MR clutch is used to decouple the motor-reducer from the FBLM, thus enabling high backdrivability. The results showed a small error (<3 mm) between the FBLM and the knee ICR. Furthermore, the MR clutch allowed for low back-drive torque (1.28 N m) compared to the torque to back-drive the motor-reducer (18.51 N m). This paper is presented in a framework that can be generalized to support the design of other knee exoskeletons.
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The design and control of an active ankle-foot rehabilitation orthotic system that was designed as a wearable and portable rehabilitation and walking assistive tool is presented. This device can measure and assist the six degree of freedoms (DOFs) movement of the human ankle joint by using a Stewart platform mechanism, which can adapt to the displacement of the rotation axis during the movement of a human foot. The estimation method of an instantaneous rotation axis of ankle-foot motion is also proposed. In this paper, the motion measurement and motion control performance of the developed assistive device is evaluated. Static and dynamic motion measurement and motion reproduction performance verification experiments are conducted. The experimental results showed that the developed assistive device is enough for measuring and controlling the human ankle-foot motion.
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By analysing the dynamic principles of the human gait, an economic gait-control analysis is performed, and passive elements are included to increase the energy efficiency in the motion control of active orthoses. Traditional orthoses use position patterns from the clinical gait analyses (CGAs) of healthy people, which are then de-normalized and adjusted to each user. These orthoses maintain a very rigid gait, and their energy cost is very high, reducing the autonomy of the user. First, to take advantage of the inherent dynamics of the legs, a state machine pattern with different gains in each state is applied to reduce the actuator energy consumption. Next, different passive elements, such as springs and brakes in the joints, are analysed to further reduce energy consumption. After an off-line parameter optimization and a heuristic improvement with genetic algorithms, a reduction in energy consumption of 16.8% is obtained by applying a state machine control pattern, and a reduction of 18.9% is obtained by using passive elements. Finally, by combining both strategies, a more natural gait is obtained, and energy consumption is reduced by 24.6% compared with a pure CGA pattern.
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Application fields of micromachined devices are growing very rapidly due to the continuous improvement of three dimensional technologies of micro-fabrication. In particular, applications of micromachined sensors to monitor gas and liquid flows hold immense potential because of their valuable characteristics (e. g., low energy consumption, relatively good accuracy, the ability to measure very small flow, and small size). Moreover, the feedback provided by integrating microflow sensors to micro mass flow controllers is essential to deliver accurately set target small flows. This paper is a review of some application areas in the biomedical field of micromachined flow sensors, such as blood flow, respiratory monitoring, and drug delivery among others. Particular attention is dedicated to the description of the measurement principles utilized in early and current research. Finally, some observations about characteristics and issues of these devices are also reported.
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In this paper, we are interested in the characteristics of a knee joint when the knee extension motion was assisted by a powered knee orthosis using a muscular stiffness force feedback. For this purpose, we developed the powered knee orthosis with an artificial pneumatic actuator, which is intended for the assistance and the enhancement of muscular activities of lower limbs. The objective of this study was to confirm the effectiveness of the powered knee orthosis that generated a knee extension torque in the motion related to a knee joint. Twenty healthy subjects participated in this study and their lower limb muscular activities were measured to identify the effectiveness of the powered knee orthosis during sit-to-stand (STS) and squat motion. The muscular activities between with and without assistance of knee extension motion were compared and analyzed for the assistance characteristics of the powered knee orthosis. To generate the knee extension torque, the knee orthosis was controlled using muscular stiffness force (MSF) feedback that is controlled by muscular activities of the vastus intermedius muscle that mainly related to the knee extension motion. For analysis of muscular activities, the surface electromyography of the muscles related to the knee extension motion, i.e., RF, vastus lateralis, vastus medialis and vastus intermedius muscles in lower limbs of the right side were recorded and biodex dynamometer was used to measure the maximal concentric isokinetic strength of the knee extensors. The experimental result showed that muscular activities in lower limbs with the assistance of the powered knee orthosis was reduced by 25.62% in rectus femoris muscle and 29.82% in biceps femoris muscle, respectively and knee extension torque of an knee joint wearing knee orthosis was increased by 17.68% in averaged peak torque. Based on the effectiveness of the powered knee orthosis, weaken elder people may have benefited from the knee extension motion augmented by the powered knee orthosis during activity of daily living, e.g., stair ascent.
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Neuroprosthetic technology and robotic exoskeletons are being developed to facilitate stepping, reduce muscle efforts, and promote motor recovery. Nevertheless, the guidance forces of an exoskeleton may influence the sensory inputs, sensorimotor interactions and resulting muscle activity patterns during stepping. The aim of this study was to report the muscle activation patterns in a sample of intact and injured subjects while walking with a robotic exoskeleton and, in particular, to quantify the level of muscle activity during assisted gait. We recorded electromyographic (EMG) activity of different leg and arm muscles during overground walking in an exoskeleton in six healthy individuals and four spinal cord injury (SCI) participants. In SCI patients, EMG activity of the upper limb muscles was augmented while activation of leg muscles was typically small. Contrary to our expectations, however, in neurologically intact subjects, EMG activity of leg muscles was similar or even larger during exoskeleton-assisted walking compared to normal overground walking. In addition, significant variations in the EMG waveforms were found across different walking conditions. The most variable pattern was observed in the hamstring muscles. Overall, the results are consistent with a non-linear reorganization of the locomotor output when using the robotic stepping devices. The findings may contribute to our understanding of human-machine interactions and adaptation of locomotor activity patterns.
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The large interest in utilising fibre Bragg grating (FBG) strain sensors for minimally invasive surgery (MIS) applications to replace conventional electrical tactile sensors has grown in the past few years. FBG strain sensors offer the advantages of optical fibre sensors, such as high sensitivity, immunity to electromagnetic noise, electrical passivity and chemical inertness, but are not limited by phase discontinuity or intensity fluctuations. FBG sensors feature a wavelength-encoding sensing signal that enables distributed sensing that utilises fewer connections. In addition, their flexibility and lightness allow easy insertion into needles and catheters, thus enabling localised measurements inside tissues and blood. Two types of FBG tactile sensors have been emphasised in the literature: single-point and array FBG tactile sensors. This paper describes the current design, development and research of the optical fibre tactile techniques that are based on FBGs to enhance the performance of MIS procedures in general. Providing MIS or microsurgery surgeons with accurate and precise measurements and control of the contact forces during tissues manipulation will benefit both surgeons and patients.
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The potential of lower-limb exoskeletons and powered orthoses in gait assistance applications for patients with locomotive disorders would have a terrific impact in the society of the near future. This paper presents the development and main features of a lower limb exoskeleton being developed as an active orthosis to allow a quadriplegic child to walk. As the patient is not able to move any of her limbs, the device will produce her basic motions in everyday-life activities: stand up, sit down, and walk stably. Synergic biarticular actuation in the ankle, compliance controller based on the force measured by insoles at the feet and the definition of parameterized hip and foot trajectories that allow to choose the characteristics of gait are some of the new features included in this prototype. Experiments validate the improved performance of gait based on the proposed approach.
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The pattern transfer process consists of two steps: lithographic resist patterning and the subsequent etching of the underlying material. Etching is often divided into two classes, wet etching and plasma etching. The isotropic etching front proceeds as a spherical wave from all points open to the etchant. Anisotropic processes are spatially directional, but there are two completely different usages of the term anisotropic etching: anisotropic wet etching and anisotropic plasma etching. Wet etching mechanisms fall into two major categories: metal etching by electron transfer, and insulator etching by acid-base reaction. Deep reactive ion etching (DRIE) is an extension of reactive ion etching (RIE) to make deep structures with high etch rate. Non-masked wet etching removes for instance diffusion mask oxide after diffusion, and similarly, mask nitrides are removed in H3PO4 or concentrated HF. Many solid state laser and magnetic materials are etched by ion beam etching. anisotropic media; sputter etching
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A walking assistance machine using a flexible shaft was developed. A combination of the flexible shaft with a worm gear was successfully adopted on this machine to develop its appearance simple and its size compact. This machine is controlled with a hybrid-control system both torque and angle at ankle and knee joints. In this system, the torsion spring constant of the flexible shaft is taken into account to the control power and the rotating angle of the motor. To expand the area of where an equipped parson can walk with the machine, a self-contained system which controlled with SH-4 microcomputer and actuators which consisted of motors and gears were put in the small backpack, and Lithium-ion battery was utilized. Therefore, the equipped parson can freely walk both in and out of doors.
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The Berkeley Lower Extremity Exoskeleton is the first functional energetically autonomous load carrying human exoskeleton and was demonstrated at U.C. Berkeley, walking at the average speed of 0.9 m/s (2 mph) while carrying a 34 kg (75 lb) payload. The original published controller, called the BLEEX Sensitivity Amplification Controller, was based on positive feedback and was designed to increase the closed loop system sensitivity to its wearer’s forces and torques without any direct measurement from the wearer. This controller was successful at allowing natural and unobstructed load support for the pilot. This article presents an improved control scheme we call “hybrid” BLEEX control that adds robustness to changing BLEEX backpack payload. The walking gait cycle is divided into stance control and swing control phases. Position control is used for the BLEEX stance leg (including the torso and backpack) and a sensitivity amplification controller is used for the swing leg. The controller is also designed to smoothly transition between these two schemes as the pilot walks. With hybrid control, the controller does not require a good model of the BLEEX torso and payload, which is difficult to obtain and subject to change as payload is added and removed. As a tradeoff, the position control used in this method requires the human to wear seven inclinometers to measure human limb and torso angles. These additional sensors require careful design to securely fasten them to the human and increase the time to don and doff BLEEX.
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There are several tactile receptors in the tissue of human fingers. In this study we calculate in detail the deformation of finger tissue when a finger comes into contact with a rigid plate using a FE (finite element) model to clarify the reason for the precise location of the receptors. The FE model is constructed using measured geometry and material properties. As a result, we found that the strain energy is concentrated at the tactile receptor locations. When a frictional force is applied, the stress/strain is concentrated near the edge of the contact area. By calculating the stress/strain distribution using models with/without epidermal ridges/papillae, we found that the shape of the epidermal ridges/papillae influences the stress/strain distribution near the tactile receptors.
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We propose a framework of realizing natural assist behavior with a walking assist suit inspired by human interaction. We look at the human interaction as a behavior of synchronization action, which is a common phenomenon in walking assist between human. To achieve this human-like walking assist, synchronization based control is adopted and applied to a walking assist suit. We use neural oscillators to entrain and synchronize the assist suit’s motion with that of human user. To determine the validity and feasibility, walking experiments have conducted with a 4-DOF walking assist suit. The results showed the validity of using synchronization based control for walking assist suit.
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A Powered Knee Orthosis (PKO) was developed for the elderly and patients with disordered gait to regain normal walking. In order to enhance the PKO performance and reduce system complexity especially for people with muscle weakness in their knee joints, an algorithm named HIP-KNEE control is proposed. This algorithm is based on the analysis of kinematic gait model, and the desired knee joint angle (KNEE) is estimated from the measurements of hip joint angle (HIP). The relationship between HIP and KNEE is modeled as a polynomial, which can be easily implemented to an embedded controller for real-time control. This control method is suitable to subjects with good function in hip joint, and it can provide help in walking without special training. An Inertia Measurement Units (IMU) is used for obtaining HIP input, and integrated with a footswitch for checking the heel condition; the gait assistance performance can be further improved.
Conference Paper
In this research, we propose a novel ankle-foot assist device for rehabilitation. This device uses a Stewart platform mechanism to measure and assist the movements of a human ankle joint in six DOF. The Stewart platform mechanism adapts to the displacement of the rotation axis of a human ankle joint during the movement of a human foot. In this study, check the accuracy of motion measurement of this device and the performance of motion control of this assist device by conducting static measurement and motion reproduction experiments. The translation error and The rotation error were less than 0.5 [mm] and 0.6 [deg] respectively. The mean reproducibility of all subjects was 0.98 These experimental results show the validity of our proposed assist device.
Conference Paper
A prototype active Ankle Foot Orthosis has been developed to control and assist plantar flexion and dorsiflexion using an innovative series elastic actuator integrated into a standard passive AFO. A motor controls the moment arm (Insertion Point Eccentricity Control or IPEC) of a pretensioned spring, and though the magnitude of the spring force remains relatively constant, the changing moment arm produces torque about the ankle. The IPEC AFO is able to provide 3.51 Nm about the ankle in dorsiflexion and 3.88 Nm in plantar flexion with a spring modulus of 3110 N/m and an initial tension of 77 N. The torque was sufficient to prevent toe-drag during swing phase. This technology may benefit users with drop-foot or other ankle disorders, including those who have suffered stroke or spinal cord injury.
Conference Paper
We propose an adaptive walking assistance strategy to control an exoskeleton robot. In our proposed framework, we explicitly consider the following: 1) the diversity of user motions (style) and 2) the interactions among a user, a robot, and an environment. To spatially coordinate a wide variety of user motions and robot behaviors, we estimated style parameters from observed user movements. To temporally coordinate the interactions among the user, the robot, and the environment, we synchronized the phases of these three systems with a coupled oscillator model. The estimated style parameters and the phase of the user motion can be used to predict future user movements. We investigated how movement prediction and phase synchronization can be beneficial to control an exoskeleton robot. To evaluate our adaptive walking assistance strategy, we developed simulated user and exoskeleton models. The physical interactions among the user, the exoskeleton, and the ground models are introduced in the simulated system. We show that the necessary torque for the user walking movement was reduced around 40% by using our proposed method to control the exoskeleton model.
Conference Paper
Many kinds of power assist device have been developed, and are driven with various actuators such as an electric motor, a hydraulic cylinder and so on. By using the exoskeleton, a high generated torque actuator can be introduced. An assist performance of these devices becomes high. On the other hand, a realization of exoskeleton which has the same D.O.F of a human is not easy from considerations about a size and strength of device. In this study, the power assist wear for lower limb is developed. The developed wear is like trousers. A human can be assisted by just wearing trousers on which the pneumatic soft actuators are put. The pneumatic soft actuator has a high power weight ratio, and has a light weight. These features contribute to realize the simple structure which is like clothes. In this paper, the structure of power assist wear is discussed, and the application of power assist wear to assist going up and down stairs are described.
Conference Paper
Achieving coordination between a lower-limb exoskeleton and its user is challenging because walking is a dynamic process that involves multiple, precisely timed muscle activations. Electromyographical (EMG) feedback, in spite of its drawbacks, provides an avenue for assistance by enabling users to reduce the level of muscle activation required for walking. As an alternative to direct EMG feedback, we present a method for exoskeleton control based on learning the activation pattern of specific muscles during cyclic movements. Using the example of pendular leg motion, the torque profile of one muscle group (hip flexors) is learned in a two-step process. First, the estimated torque profile is indexed to the phase of the swing movement using an adaptive frequency oscillator (AFO). The profile is then encoded using linear weighted regression. In the algorithm's assistive mode, the learned profile is reconstructed by means of the AFO and without need for additional EMG input. The reconstructed profile is converted into a torque profile to be physically delivered by the exoskeleton. We tested our method on a single-actuator exoskeleton that assists the hip joint during stationary leg swing. The learning and assistance functions were built on top of an admittance controller that enhances the exoskeleton's mechanical transparency. Initial tests showed a high level of coordination, i.e. simultaneous positive work, between the subjects' hip flexor torque and the exoskeleton's assistive torque. This result opens the door for future studies to test the users' ability to reduce their muscle activation in proportion to the assistance delivered by the exoskeleton.
Conference Paper
The Body Extender is a whole-body exoskeleton designed to operate in unknown and difficult environments, for instance in disaster areas. The Body Extender allows the wearing operator to increase its force while maintaining a high level of perception. The present work describes a novel control system for the Body Extender. We designed the control loop in such a way the interaction forces are perceived as a fraction of the overall external forces. These percentages can be decided at design time as a trade-off between sensitivity and force extension. To reali