Article

# An Abdominal Phantom With Tunable Stiffness Nodules and Force Sensing Capability for Palpation Training

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

## Abstract

Robotic phantoms enable advanced physical examination training before using human patients. In this article, we present an abdominal phantom for palpation training with controllable stiffness liver nodules that can also sense palpation forces. The coupled sensing and actuation approach is achieved by pneumatic control of positive-granular jammed nodules for tunable stiffness. Soft sensing is done using the variation of internal pressure of the nodules under external forces. This article makes original contributions to extend the linear region of the neo-Hookean characteristic of the mechanical behavior of the nodules by 140% compared to no-jamming conditions and to propose a method using the organ level controllable nodules as sensors to estimate palpation position and force with a root-mean-square error of 4% and 6.5%, respectively. Compared to conventional soft sensors, the method allows the phantom to sense with no interference to the simulated physiological conditions when providing quantified feedback to trainees, and to enable training following current bare-hand examination protocols without the need to wear data gloves to collect data.

## No full-text available

... Recent developments in the fields of robotic hardware, sensing, and machine learning have led to great progress in robotic applications in various areas [1], [2], [3]. Recent advances in Robotics have led to progress in various areas and naturally raised the demand for fully-autonomous, longlasting and self-evolving robots [4], keeping human efforts further out of the loop. ...
... In task (c), when a forbidden zone is presented (c 1 ), the robot is required to pick a ramp (c 2 ) and place it in the zone (c 3 ) to allow drawing circuit through the zone (c 4 ). In task (d), the electrodes of the robot and the power source are in the opposite position, the robot needs to connect a pair of electrode first (d 1 ), then pick a ramp (d 2 ) and place on the drawn circuit (d 3 ) to connect the rest electrodes without shortcircuiting the power source (d 4 ) pose is obtained by T pick = argmax V pick , the partial crop with size c, ψ (s t [T pick ]) ∈ R c×c×d centered around T pick is transformed by ξ and cross-correlated with the feature map φ (s t ) according to (3). The pixel-wise placing state value can then be obtained by V place ∈ R H×W ×k = softmax (Q place (ξ | s t , T pick )). ...
Preprint
Full-text available
Robots with the ability to actively acquire power from surroundings will be greatly beneficial for long-term autonomy and to survive in uncertain environments. In this work, we present a robot capable of drawing circuits with conductive ink while also rearranging the visual world to receive maximum energy from a power source. A range of circuit drawing tasks is designed to simulate real-world scenarios, including avoiding physical obstacles and regions that would discontinue drawn circuits. We adopt the state-of-the-art Transporter networks for pick-and-place manipulation from visual observation. We conduct experiments in both simulation and real-world settings, and our results show that, with a small number of demonstrations, the robot learns to rearrange the placement of objects (removing obstacles and bridging areas unsuitable for drawing) and to connect a power source with a minimum amount of conductive ink. As autonomous robots become more present, in our houses and other planets, our proposed method brings a novel way for machines to keep themselves functional by rearranging their surroundings to create their own electric circuits.
... Previous studies exploring pneumatic actuation within soft tactile sensors have applied this to reactive grasping (McInroe et al., 2018), shape identification (Huang et al., 2019;Xiang et al., 2019), estimating tissue elastic modulus (Gubenko et al., 2017) and an explorative capsule capable of self-locomotion (Hinitt et al., 2015). Variable effective stiffness tactile sensors have also been applied to emulate nodules inside phantom organs to assist with medical diagnosis training (He et al., 2020b). ...
... Optics-based tactile sensing is common across soft actuated sensors, as all electrical components can be physically separated from the tactile membrane (Shimonomura, 2019). Among the pneumatically actuated tactile sensors referenced above, only He et al. (2020a) and He et al. (2020b) use pneumatic variations as the primary form of sensing; all other studies chose to implement optics-based tactile sensing. These studies have focused on detecting surface or bulk features of the stimulus that they are sensing, where heterogeneity in the depth of the stimulus remains under-exploited as a tactile cue. ...
Article
Full-text available
Soft tactile sensors are an attractive solution when robotic systems must interact with delicate objects in unstructured and obscured environments, such as most medical robotics applications. The soft nature of such a system increases both comfort and safety, while the addition of simultaneous soft active actuation provides additional features and can also improve the sensing range. This paper presents the development of a compact soft tactile sensor which is able to measure the profile of objects and, through an integrated pneumatic system, actuate and change the effective stiffness of its tactile contact surface. We report experimental results which demonstrate the sensor’s ability to detect lumps on the surface of objects or embedded within a silicone matrix. These results show the potential of this approach as a versatile method of tactile sensing with potential application in medical diagnosis.
... Unlike soft sensors with fixed features, where the material properties are only characterised as the parameter to determine absolute sensor responses 18 , the proposed tunable stiffness sensor determines the sensing model based on the physical property. This active sensing framework is demonstrated by exploring the inherited sensing characteristics with pressurised fluid 19 , where significant sensing characteristics and stiffness change is exhibited during inflation. ...
Article
Full-text available
The stiffness of a soft robot with structural cavities can be regulated by controlling the pressure of a fluid to render predictable changes in mechanical properties. When the soft robot interacts with the environment, the mediating fluid can also be considered an inherent information pathway for sensing. This approach to using structural tuning to improve the efficacy of a sensing task with specific states has not yet been well studied. A tunable stiffness soft sensor also renders task-relevant contact dynamics in soft robotic manipulation tasks. This paper proposes a type of adaptive soft sensor that can be directly 3D printed and controlled using pneumatic pressure. The tunability of such a sensor helps to adjust the sensing characteristics to better capturing specific tactile features, demonstrated by detecting texture with different frequencies. We present the design, modelling, Finite Element Simulation, and experimental characterisation of a single unit of such a tunable stiffness sensor. How the sensing characteristics are affected by adjusting its stiffness is studied in depth. In additional to the tunability, the results show such type of adaptive sensors exhibit good sensitivity (up to 2.6 [KPa/N]), high sensor repeatability (average std < 0.008 [KPa/N]), low hysteresis (< 6%), and good manufacturing repeatability (average std = 0.0662[KPa/N]).
... Stanley and Okamura [16] proposed a surface display that can change geometry by programming the pressure of the inflating layer and granular jamming stiffening layer. He et al. [17] implemented positive pressure granular jamming in simulating tunable stiffness liver tumors and used the nodules as soft sensors [18]. A similar granular jamming idea to create a configurable object with stiffness control can be found in [19], where a programmable soft 3D object is presented. ...
Conference Paper
A patient would contract surface muscles as a reaction called muscle guarding when experiencing discomfort and pain during physical palpation. This reaction carries important information about an affected location. Training physicians to regulate palpation forces to elicit just enough muscle guarding is a challenge using real patients. Tunable stiffness mechanisms enabled by soft robotics can be effectively integrated into medical simulator designs for effective clinical education. In this paper, we propose a controllable stiffness muscle layer to simulate guarding for abdominal palpation training. Designs with soft, fine and rigid granular jamming, stretchable and non-stretchable layer jamming mechanisms were tested and evaluated as methods to create controllable stiffness muscle. User studies have been carried out on 10 naive participants to differentiate the guarding and non-guarding abdomen with the proposed jamming mechanisms. Muscle samples made of ground coffee (fine granular jamming) and latex layers (stretchable layer jamming) show good usability in simulating abdomen with different stiffness with average success detection rate over 70% for both tested palpation gestures (single finger and multiple fingers) after short pretraining.
Article
In order to analyze the value of contrast-enhanced ultrasound (CEUS) combined with functional magnetic resonance imaging (fMRI) in the early differential diagnosis of liver nodular lesions, the authors studied the value of MRI in liver nodular lesions. A total of 82 patients with liver nodular lesions admitted to the hospital were selected for retrospective analysis; all of them underwent CEUS and fMRI examinations, and taking a biopsy or postoperative pathological examination results as the gold standard, the diagnostic value of CEUS, fMRI single item, and the two combined examinations for liver nodular lesions was analyzed by four-table. The biopsy or postoperative pathological examination results showed that a total of 88 lesions were detected in 82 patients, including 51 patients with benign lesions, with 54 lesions, and 31 patients with malignant lesions, with 34 lesions. Taking biopsy or pathological examination results as the gold standard, the four-table analysis CEUS had a sensitivity of 79.63%, a specificity of 82.35%, an accuracy of 80.68%, and a Kappa value of 0.603 for diagnosing benign and malignant liver nodular lesions. The sensitivity of fMRI in diagnosing benign and malignant liver nodular lesions was 83.33%, the specificity was 85.29%, the accuracy was 84.09%, and the Kappa value was 0.672; the combined sensitivity of the two in the diagnosis of benign and malignant liver nodular lesions was 94.44%, the specificity was 91.18%, the accuracy was 93.18%, and the Kappa value was 0.856, both of which were superior to single detection, and the difference in accuracy was statistically significant ( χ 2 = 5.683, P < 0.05 ). CEUS and fMRI have a certain value in the differential diagnosis of liver nodular lesions; the combination of the two can improve the diagnostic sensitivity and accuracy, and has more clinical application value.
Article
Full-text available
Tactile hands-only training is particularly important for medical palpation. Generally, equipment for palpation training is expensive, static, or provides too few study cases to practice on. We have therefore developed a novel haptic surface concept for palpation training, using ferrogranular jamming. The concept's design consists of a tactile field spanning 260 x 160 mm, and uses ferromagnetic granules to alter shape, position, and hardness of palpable irregularities. Granules are enclosed in a compliant vacuum-sealed chamber connected to a pneumatic system. A variety of geometric shapes (output) can be obtained by manipulating and arranging granules with permanent magnets. The tactile hardness of the palpable output can be controlled by adjusting the chamber's vacuum level. A psychophysical experiment (N 28) investigated how people interact with the palpable surface and evaluated the proposed concept. Untrained participants characterized irregularities with different position, form, and hardness through palpation, and their performance was evaluated. A baseline (no irregularity) was compared to three irregularity conditions: two circular shapes with different hardness (Hard Lump and Soft Lump), and an Annulus shape. 100% of participants correctly identified an irregularity in the three irregularity conditions, whereas 78.6% correctly identified baseline. Overall agreement between participants was high (κ 0.723). The Intersection over Union (IoU) for participants sketched outline over the actual shape was IoU Mdn 79.3% for Soft Lump, IoU Mdn 68.8% for Annulus, and IoU Mdn 76.7% for Hard Lump. The distance from actual to drawn center was Mdn 6.4 mm (Soft Lump), Mdn 5.3 mm (Annulus), and Mdn 7.4 mm (Hard Lump), which are small distances compared to the size of the field. The participants subjectively evaluated Soft Lump to be significantly softer than Hard Lump and Annulus. Moreover, 71% of participants thought they improved their palpation skills throughout the experiment. Together, these results show that the concept can render irregularities with different position, form, and hardness, and that users are able to locate and characterize these through palpation. Participants experienced an improvement in palpation skills throughout the experiment, which indicates the concepts feasibility as a palpation training device.
Article
Full-text available
Soft fingertips have shown significant adaptability for grasping a wide range of object shapes thanks to elasticity. This ability can be enhanced to grasp soft, delicate objects by adding touch sensing. However, in these cases, the complete restraint and robustness of the grasps have proved to be challenging, as the exertion of additional forces on the fragile object can result in damage. This paper presents a novel soft fingertip design for delicate objects based on the concept of embedded air cavities, which allow the dual ability of adaptive sensing and active shape changing. The pressurized air cavities act as soft tactile sensors to control gripper position from internal pressure variation; and active fingertip deformation is achieved by applying positive pressure to these cavities, which then enable a delicate object to be kept securely in position, despite externally applied forces, by form closure. We demonstrate this improved grasping capability by comparing the displacement of grasped delicate objects exposed to high-speed motions. Results show that passive soft fingertips fail to restrain fragile objects at accelerations as low as ${0.1 m/s^{2}}$ , in contrast, with the proposed fingertips, delicate objects are completely secure even at accelerations of more than ${5 m/s^{2}}$ .
Article
Full-text available
This paper presents the development of a wearable Fingertip Haptic Device (FHD) that can provide cutaneous feedback via a Variable Compliance Platform (VCP). The FHD includes an inertial measurement unit, which tracks the motion of the user’s finger while its haptic functionality relies on two parameters: pressure in the VCP and its linear displacement towards the fingertip. The combination of these two features results in various conditions of the FHD, which emulate the remote object or surface stiffness properties. Such a device can be used in tele-operation, including virtual reality applications, where rendering the level of stiffness of different physical or virtual materials could provide a more realistic haptic perception to the user. The FHD stiffness representation is characterised in terms of resulting pressure and force applied to the fingertip created through the relationship of the two functional parameters – pressure and displacement of the VCP. The FHD was tested in a series of user studies to assess its potential to create a user perception of the object’s variable stiffness. The viability of the FHD as a haptic device has been further confirmed by interfacing the users with a virtual environment. The developed virtual environment task required the users to follow a virtual path, identify objects of different hardness on the path and navigate away from “no-go” zones. The task was performed with and without the use of the variable compliance on the FHD. The results showed improved performance with the presence of the variable compliance provided by the FHD in all assessed categories and particularly in the ability to identify correctly between objects of different hardness.
Article
Full-text available
This paper presents experimental evidence for the existence of a set of unique force modulation strategies during manual soft tissue palpation to locate hard abnormalities such as tumors. We explore the active probing strategies of defined local areas and outline the role of force control. In addition, we investigate whether the applied force depends on the non-homogeneity of the soft tissue. Experimental results on manual palpation of soft silicone phantoms show that humans have a well defined force control pattern of probing that is used independently of the non-homogeneity of the soft tissue. We observed that the modulations of lateral forces are distributed around the mean frequency of 22.3 Hz. Furthermore, we found that the applied normal pressure during probing can be modeled using a second order reactive autoregressive model. These mathematical abstractions were implemented and validated for the autonomous palpation for different stiffness parameters using a robotic probe with a rigid spherical indentation tip. The results show that the autonomous robotic palpation strategy abstracted from human demonstrations is capable of not only detecting the embedded nodules, but also enhancing the stiffness perception compared to static indentation of the probe.
Article
Full-text available
Because of their continuous and natural motion, fluidically powered soft actuators have shown potential in a range of robotic applications, including prosthetics and orthotics. Despite these advantages, robots using these actuators require stretchable sensors that can be embedded in their bodies for sophisticated functions. Presently, stretchable sensors usually rely on the electrical properties of materials and composites for measuring a signal; many of these sensors suffer from hysteresis, fabrication complexity, chemical safety and environmental instability, and material incompatibility with soft actuators. Many of these issues are solved if the optical properties of materials are used for signal transduction. We report the use of stretchable optical waveguides for strain sensing in a prosthetic hand. These optoelectronic strain sensors are easy to fabricate, are chemically inert, and demonstrate low hysteresis and high precision in their output signals. As a demonstration of their potential, the photonic strain sensors were used as curvature, elongation, and force sensors integrated into a fiber-reinforced soft prosthetic hand. The optoelectronically innervated prosthetic hand was used to conduct various active sensation experiments inspired by the capabilities of a real hand. Our final demonstration used the prosthesis to feel the shape and softness of three tomatoes and select the ripe one.
Article
Full-text available
When people are asked to palpate a novel soft object to discern its physical properties such as texture, elasticity, and even non-homogeneity, they not only regulate probing behaviors, but also the co-contraction level of antagonistic muscles to control the mechanical impedance of fingers. It is suspected that such behavior tries to enhance haptic perception by regulating the function of mechanoreceptors at different depths of the fingertips and proprioceptive sensors such as tendon and spindle sensors located in muscles. In this paper, we designed and fabricated a novel two-degree of freedom variable stiffness indentation probe to investigate whether the regulation of internal stiffness, indentation, and probe sweeping velocity (PSV) variables affect the accuracy of the depth estimation of stiff inclusions in an artificial silicon phantom using information gain metrics. Our experimental results provide new insights into not only the biological phenomena of haptic perception but also new opportunities to design and control soft robotic probes.
Article
Full-text available
The excellent compliance and large range of motion of soft actuators controlled by fluid pressure has lead to strong interest in applying devices of this type for biomimetic and human-robot interaction applications. However, in contrast to soft actuators fabricated from stretchable silicone materials, conventional technologies for position sensing are typically rigid or bulky and are not ideal for integration into soft robotic devices. Therefore, in order to facilitate the use of soft pneumatic actuators in applications where position sensing or closed loop control is required, a soft pneumatic bending actuator with an integrated carbon nanotube position sensor has been developed. The integrated carbon nanotube position sensor presented in this work is flexible and well suited to measuring the large displacements frequently encountered in soft robotics. The sensor is produced by a simple soft lithography process during the fabrication of the soft pneumatic actuator, with a greater than 30% resistance change between the relaxed state and the maximum displacement position. It is anticipated that integrated resistive position sensors using a similar design will be useful in a wide range of soft robotic systems.
Article
Full-text available
The large expansion of the robotic field in the last decades has created a growing interest in the research and development of tactile sensing solutions for robot hand and body integration. Piezoresistive composites are one of the most widely employed materials for this purpose, combining simple and low cost preparation with high flexibility and conformability to surfaces, low power consumption, and the use of simple read-out electronics. This work provides a review on the different type of composite materials, classified according to the conduction mechanism and analyzing the physics behind it. In particular piezoresistors, strain gauges, percolative and quantum tunnelling devices are reviewed here, with a perspective overview on the most used filler types and polymeric matrices. A description of the state-of-the-art of the tactile sensor solutions from the point of view of the architecture, the design and the performance is also reviewed, with a perspective outlook on the main promising applications.
Article
Full-text available
Capacitive technology allows building sensors that are small, compact and have high sensitivity. For this reason it has been widely adopted in robotics. In a previous work we presented a compliant skin system based on capacitive technology consisting of triangular modules interconnected to form a system of sensors that can be deployed on non-flat surfaces. This solution has been successfully adopted to cover various humanoid robots. The main limitation of this and all the approaches based on capacitive technology is that they require to embed a deformable dielectric layer (usually made using an elastomer) covered by a conductive layer. This complicates the production process considerably, introduces hysteresis and limits the durability of the sensors due to ageing and mechanical stress. In this paper we describe a novel solution in which the dielectric is made using a thin layer of 3D fabric which is glued to conductive and protective layers using techniques adopted in the clothing industry. As such, the sensor is easier to produce and has better mechanical properties. Furthermore, the sensor proposed in this paper embeds transducers for thermal compensation of the pressure measurements. We report experimental analysis that demonstrates that the sensor has good properties in terms of sensitivity and resolution. Remarkably we show that the sensor has very low hysteresis and effectively allows compensating drifts due to temperature variations.
Article
Full-text available
Compact ultrasound technology has facilitated growth in point-of-care uses in many specialties. This review includes videos demonstrating the use of ultrasonography to guide central venous access, detect pneumothorax, detect evidence of hemorrhage after trauma, and screen for abdominal aortic aneurysm.
Article
Full-text available
The most effective screening for prostate cancer combines the prostate specific antigen blood test with the digital rectal examination (DRE). In performing a DRE, two sequential tasks are completed: (task a) palpating the prostate to identify abnormalities and (task b) linking identified abnormalities to a disease diagnosis. At present, clinicians find too few abnormalities and have variable rates of detection, due in part to the inadequacy of training simulators. The Virginia Prostate Examination Simulator (VPES) was designed, built, and tested to address the inadequacies of current simulators by incorporating the design requirements of the basic elements of accurate anatomy, multiple and reconfigurable scenarios of graded difficulty, and technique and performance feedback. We compared the training effectiveness of the VPES with two commercial simulators in an experiment of 36 medical and nurse practitioner students. Results indicate each type of training simulator-improved abilities, in general. Upon closer analysis, however, the following key patterns emerge: 1) Across all types of training, more deficiencies lie in skill-based rather than rule-based decision making, which improves only for VPES trainees; 2) only VPES training transfers both to other simulators and previously unencountered scenarios; 3) visual feedback may increase the number of abnormalities reported yet hinder the ability to discriminate; and 4) applied finger pressure did not correlate with the ability to identify abnormalities.
Article
Full-text available
Simulation for medical and healthcare applications, although still in a relatively nascent stage of development, already has a history that can inform the process of further research and dissemination. The development of mannequin simulators used for education, training, and research is reviewed, tracing the motivations, evolution to commercial availability, and efforts toward assessment of efficacy of those for teaching cardiopulmonary resuscitation, cardiology skills, anaesthesia clinical skills, and crisis management. A brief overview of procedural simulators and part-task trainers is also presented, contrasting the two domains and suggesting that a thorough history of the 20+ types of simulator technologies would provide a useful overview and perspective. There has been relatively little cross fertilisation of ideas and methods between the two simulator domains. Enhanced interaction between investigators and integration of simulation technologies would be beneficial for the dissemination of the concepts and their applications.
Article
Full-text available
Physical examination (PEx) skills are declining among medical trainees, yet many institutions are not teaching these systematically and effectively. Many variables contribute to effective teaching: teachers' confidence in their clinical skills, ability to demonstrate and assess these skills; availability of suitable patients; trainee attitude and fatigue; belief that institutions do not value clinical teachers. Finally, the relevance and significance of a systematic exam must be demonstrated or the teaching degenerates into a 'show-and-tell' exercise. This paper describes twelve practical teaching tips that can be used to promote high quality PEx teaching in 5 minutes or 45 minutes. TEACHING TIPS: (1) Diagnostic hypotheses should guide reflective exam; (2) Teachers with the best clinical skills should be recruited; (3) A longitudinal and systematic curriculum can tailor teaching to multiple learner levels (4) Integration of simulation and bedside teaching can maximise learning; (5) Bedside detective work and games make learning fun; (6) The 6-step approach to teach procedures can be adopted to teach PEx; (7) Clinical teaching at the bedside should be increased; (8) Linking basic sciences to clinical findings will demonstrate relevance; (9) Since assessment drives learning, clinical skills should be systematically assessed; (10) Staff development can target improvement of teachers' clinical skills for effective teaching; (11) Technology should be used to study utility of clinical signs; (12) Institutions should elevate the importance of clinical skills teaching and recognize and reward teachers. PEx is important in patient-physician interactions, a valuable contributor to accurate clinical diagnosis and can be taught effectively using practical tips. To reverse the trend of deficient clinical skills, precision of clinical findings should be studied and exam manoeuvres that do not contribute to diagnosis discarded; institutions should value clinical skills teaching, appoint and fund core faculty to teach and provide staff development to improve teaching skills.
Article
Full-text available
The purpose of this study was to evaluate the potential value of MR elastography (MRE) in the characterization of solid liver tumors. Forty-four liver tumors (14 metastatic lesions, 12 hepatocellular carcinomas, nine hemangiomas, five cholangiocarcinomas, three cases of focal nodular hyperplasia, and one hepatic adenoma) were evaluated with MRE. MRE was performed with a 1.5-T system with a modified phase-contrast gradient-echo sequence to collect axial wave images sensitized along the through-plane motion direction. The tumors were identified on T2- and T1-weighted and gadolinium-enhanced T1-weighted images, and the MRE images were obtained through the tumor. A stiffness map (elastogram) was generated in an automated process consisting of an inversion algorithm. The mean shear stiffness of the tumor was calculated with a manually specified region of interest over the tumor in the stiffness map. The stiffness value of tumor-free hepatic parenchyma was calculated. Statistical analysis was performed on the stiffness values for differentiation of normal liver, fibrotic liver, benign tumors, and malignant tumors. Malignant liver tumors had significantly greater mean shear stiffness than benign tumors (10.1 kPa vs 2.7 kPa, p < 0.001), fibrotic liver (10.1 kPa vs 5.9 kPa, p < 0.001), and normal liver (10.1 kPa vs 2.3 kPa, p < 0.001). Fibrotic livers had stiffness values overlapping both the benign and the malignant tumors. A cutoff value of 5 kPa accurately differentiated malignant tumors from benign tumors and normal liver parenchyma in this preliminary investigation. MR elastography is a promising noninvasive technique for assessing solid liver tumors. Use of MRE may lead to new quantitative tissue characterization parameters for differentiating benign and malignant liver tumors.
Article
Side effects caused by excessive contact pressure such as discomfort and pressure sores are commonly complained by patients wearing orthoses. These problems leading to low patient compliance decrease the effectiveness of the device. To mitigate side effects, this study describes the design and fabrication of a soft sensor skin with strategically placed 12 sensor units for static contact pressure measurement beneath a hand and wrist orthosis. A Finite Element Model was built to simulate the pressure on the hand of a subject and sensor specifications were obtained from the result to guide the design. By testing the fabricated soft sensor skin on the subject, contact pressure between 0.012 MPa and 0.046 MPa was detected, revealing the maximum pressure at the thumb metacarpophalangeal joint which was the same location of the highest pressure of simulation. In this paper, a new fabrication method combining etching and multi-material additive manufacture was introduced to produce multiple sensor units as a whole. Furthermore, a novel fish-scale structure as the connection among sensors was introduced to stabilize sensor units and reinforce the soft skin. Experimental analysis reported that the sensor signal is repeatable, and the fish-scale structure facilitates baseline resuming of sensor signal during relaxation.
Article
Recent work has begun to explore the design of biologically inspired soft robots composed of soft, stretchable materials for applications including the handling of delicate materials and safe interaction with humans. However, the solid-state sensors traditionally used in robotics are unable to capture the high-dimensional deformations of soft systems. Embedded soft resistive sensors have the potential to address this challenge. However, both the soft sensors—and the encasing dynamical system—often exhibit nonlinear time-variant behavior, which makes them difficult to model. In addition, the problems of sensor design, placement, and fabrication require a great deal of human input and previous knowledge. Drawing inspiration from the human perceptive system, we created a synthetic analog. Our synthetic system builds models using a redundant and unstructured sensor topology embedded in a soft actuator, a vision-based motion capture system for ground truth, and a general machine learning approach. This allows us to model an unknown soft actuated system. We demonstrate that the proposed approach is able to model the kinematics of a soft continuum actuator in real time while being robust to sensor nonlinearities and drift. In addition, we show how the same system can estimate the applied forces while interacting with external objects. The role of action in perception is also presented. This approach enables the development of force and deformation models for soft robotic systems, which can be useful for a variety of applications, including human-robot interaction, soft orthotics, and wearable robotics.
Conference Paper
Medical manikins play an essential role in the training process of physicians. Currently, most available simu-lators for abdominal palpation training do not contain control-lable organs for dynamic simulations. In this paper, we present a soft robotics controllable liver that can simulate various liver diseases and symptoms for effective and realistic palpation training. The tumors in the liver model are designed based on granular jamming with positive pressure, which converts the fluid-like impalpable particles to a solid-like tumor state by applying low positive pressure on the membrane. Through inflation, the tumor size, liver stiffness, and liver size can be controlled from normal liver state to various abnormalities including enlarged liver, cirrhotic liver, and multiple cancerous and malignant tumors. Mechanical tests have been conducted in the study to evaluate the liver design and the role of positive pressure granular jamming in tumor simulations.
Article
There is increasing interest in the use of soft materials in robotic applications ranging from wearable devices to soft grippers. While soft structures provide a number of favorable properties to robotic systems, sensing of large deformable soft structures is still a considerable challenge; sensors must not inhibit the mechanical properties of the soft body, and the potential infinite degree-of-freedom deformations mean that there is an intrinsically limited resolution of the sensing receptors. An approach to address these challenges using a conductive thermoplastic elastomer is proposed. This allows sensory strain information to be gained from deforming structures without disturbing the dynamics of the system enabling coverage of large soft surfaces. In this article, a theoretical framework is developed, which provides a set of design principles to optimize and characterize sensor implementation, allowing maximum information about location, posture, and shape of the object to be determined. The proposed approach has been tested experimentally for the case study of the universal gripper; investigating how a sensorized gripper can allow a robot to identify grasped objects to enable improved gripping and manipulation performance.
Article
Soft pneumatic grippers always have characteristics of simple structure, good compliance, and natural motion, which make them have a wide range of applications. Nevertheless, there is a significant challenge that sensors used for detecting gripper’s force and deformation are asked for having good deformability and simple structure, and doing not limit gripper’s behavior. Based on the requirements, a novel pneumatic soft sensor (PSS) is designed and manufactured in this paper. It is composed of a sensing body and a pressure sensor. The sensing body is made of silicon rubber, and has a simple structure and fabrication process. Due to the characteristic of silicon rubber, it can be easily embedded into a soft gripper without restricting its behavior. According to the inner pressure of sensing body, PSS can measure contact force and curvature by building relation models of pressure vs. contact force and pressure vs. curvature, and its measurement accuracy is tested by a large of experiments. The results validate the effectiveness and reliability of PSS. Finally, a novel soft pneumatic finger with two air chambers is designed and fabricated. One of air chambers named inflated air chamber is used for actuating the finger, and another is called sensing air chamber with the function of PSS. Each air chamber has a pressure sensor for measuring inner pressure. The sensing air chamber makes the finger have a self-sensing ability, which has been verified by several tests.
Article
Elastic instability for the inflation and deflation of a thin-walled spherical rubber balloon is examined within the framework of finite pseudo-elasticity. When a spherical rubber balloon is inflated, it is subject to a complex deformation after a pressure maximum has been obtained. One part of the balloon is lightly stretched while the remainder becomes highly stretched. So an aspherical deformation is observed after the initial spherical inflation. A pseudo-elastic strain energy function including a damage variable which may model the loading, unloading and reloading of rubber is used. The balloon is idealized as an elastic membrane and the inflation, deflation and re-inflation of the balloon is described in detail. Instability of solutions is discussed through energy comparison. Furthermore, the effect of temperature is discussed with a thermohyperelastic model and the residual strain is analyzed with a pseudo-elastic strain energy function including a residual strain variable.
Conference Paper
The shortage of physicians afflicting developed countries encourages engineers and doctors to collaborate towards the development of telemedicine. In particular, robotic systems have the potential for helping doctors making examination. A very common examination that can be the goal of a robotic system is palpation. Most of the robotics systems that have been developed for palpation present interesting features such as integrating augmented reality environments or allowing for hand free interaction. In this paper we present a novel palpation system that allows us to perform virtual palpation of real objects by means of a haptic and an augmented reality feedback. This system features an encountered-type haptic interface in which the haptic feedback is calculated by a collision detection algorithm that is based on online recording of the surface to be touched. The system allows the users to remove their hand from the haptic interface end-effector that follows the user’s hand thanks to the tracking performed by a Leap Motion. We show that the system provides a natural interaction during the contact-non contact switch, a suitable force during indentation, and it allows to discriminate objects within the body through the haptic channel.
Article
Jamming--the mechanism by which granular media can transition between liquid-like and solid-like states-has recently been demonstrated as a variable strength and stiffness mechanism in a range of applications. As a low-cost and simple means for achieving tunable mechanical properties, jamming has been used in systems ranging from architectural to medical ones. This thesis explores the utility of jamming for robotic manipulation applications, both at a fundamental level of understanding how granular properties affect the performance of jammed systems, and at a more applied level of designing functional robotic components. Specifically, the purpose of this thesis was to enable engineers to design jammable robotic systems in a principled manner. Three parallel yet related studies were conducted to work towards this goal. First, an experimental analysis was conducted to determine whether the bulk shear strength of granular systems can be correlated with grain properties-such as ones concerning shape, size distribution, and surface texture-extracted from 2D silhouettes of grains. Second, a novel medium composed of a mixture of hard and soft spheres was proposed to achieve variable strength and stiffness properties as a function of confining pressure; experimental analysis was conducted on this system with not only varying confining pressures but also varying mixing ratios of hard and soft spheres. Finally, the design and analysis of a novel jammable robotic manipulator-with the goal of maximizing both the strength and articulation of the system-is presented.
Article
It has been known for many years that deformation results in softening of rubber and that the initial stress-strain curve determined during the first deformation is unique and cannot be retraced. Further the effect of repeated deformation is to cause rubber asymptotically to approach a steady state with a constant or equilibrium stress-strain curve. Softening in this way occurs in vulcanizates either with or without fillers although the effect appears to be much more pronounced in vulcanizates containing high proportions of reinforcing fillers. After the hardness test the simple extension stress-strain test is the test most widely used by rubber technologists. The conventional stress-strain curve is obtained on samples which have not been previously deformed and for design purpose the unique value of stiffness given by this curve may be of little significance. Thus it appears that the values of stress—strain properties determined after “conditioning” cycles of deformation would be of more practical use than the unique value obtained in the conventional test. In recent years much interest has been shown in the factors responsible for this softening behavior particularly in regard to the implications of the loss of the stiffening action of reinforcing fillers on the mechanism of reinforcement.
Article
The combination of particle jamming and pneumatics allows the simultaneous control of shape and mechanical properties in a tactile display. A hollow silicone membrane is molded into an array of thin cells, each filled with coffee grounds such that adjusting the vacuum level in any individual cell rapidly switches it between flexible and rigid states. The array clamps over a pressure-regulated air chamber with internal mechanisms designed to pin the nodes between cells at any given height. Various sequences of cell vacuuming, node pinning, and chamber pressurization allow the surface to balloon into a variety of shapes. Experiments were performed to expand existing physical models of jamming at the inter-particle level to define the rheological characteristics of jammed systems from a macroscopic perspective, relevant to force-displacement interactions that would be experienced by human users. Force-displacement data show that a jammed cell in compression fits a Maxwell model and a cell deflected in the center while supported only at the edges fits a Zener model, each with stiffness and damping parameters that increase at higher levels of applied vacuum. This provides framework to tune and control the mechanical properties of a jamming.
Article
A haptic device using flexible sheets for virtual training of abdominal palpation is proposed, mainly focusing on light and deep palpation. This device forms a semicylinder using two boards with rounded corners and two layered flexible sheets made of rubber. The device imitates the form of an abdomen. A trainee doctor touches and pushes everywhere of the upper sheet directly with his/her fingers and palm or single hand and both hands, regarding it as a virtual abdomen. Pulling the lower sheet lengthwise varies the softness of the sheet: the stretched sheet feels hard and the loose sheet feels soft. The trainee doctor can feel different softness of abdomens by pushing the device. Pulling the upper sheet in waistline direction depresses the centre of the device between the boards like a saddle. Stretching and loosening the upper sheet simulates up-and-down movement of an abdomen due to breathing. As a result, the trainee doctor can experience virtual abdominal palpation in the similar way as real palpation. The softness and depression at the centre of the device are measured for different tensions of the upper and lower sheets, and are compared with the measured softness and up-and-down movement due to breathing of real abdomens. A skilled physician evaluates that the device can present different softness in the range of softness of real abdomens and that the up-and-down movement of the device resembles that of real abdomens due to breathing. The empirical and sensory criterion of the physician is ascertained quantitatively using the device: he pushes abdomens until he feels the same reaction force, regardless of their softness.
Article
This paper presents a novel “layer jamming” mechanism that can achieve variable stiffness. The layer jamming mechanism exploits the friction present between layers of thin material, which can be controlled by a confining pressure. Due to the mechanism's hollow geometry, compact size, and light weight, it is well suited for various minimally invasive surgery applications, where stiffness change is required. This paper describes the concept, the mathematical model, and a tubular snake-like manipulator prototype. Various characteristics of layer jamming, such as stiffness and yield strength, are studied both theoretically and experimentally.
Article
We describe the design, fabrication, and calibration of a highly compliant artificial skin sensor. The sensor consists of multilayered mircochannels in an elastomer matrix filled with a conductive liquid, capable of detecting multiaxis strains and contact pressure. A novel manufacturing method comprised of layered molding and casting processes is demonstrated to fabricate the multilayered soft sensor circuit. Silicone rubber layers with channel patterns, cast with 3-D printed molds, are bonded to create embedded microchannels, and a conductive liquid is injected into the microchannels. The channel dimensions are 200 $\mu{\rm m}$ (width) $\times\,$300 $\mu{\rm m}$ (height). The size of the sensor is 25 mm $\times\,$25 mm, and the thickness is approximately 3.5 mm. The prototype is tested with a materials tester and showed linearity in strain sensing and nonlinearity in pressure sensing. The sensor signal is repeatable in both cases. The characteristic modulus of the skin prototype is approximately 63 kPa. The sensor is functional up to strains of approximately 250%.
Article
Passive haptics, also known as tactile augmentation, denotes the use of a physical counterpart to a virtual environment to provide tactile feedback. Employing passive haptics can result in more realistic touch sensations than those from active force feedback, especially for rigid contacts. However, changes in the virtual environment would necessitate modifications of the physical counterparts. In recent work space warping has been proposed as one solution to overcome this limitation. In this technique virtual space is distorted such that a variety of virtual models can be mapped onto one single physical object. In this paper, we propose as an extension adaptive space warping; we show how this technique can be employed in a mixed-reality surgical training simulator in order to map different virtual patients onto one physical anatomical model. We developed methods to warp different organ geometries onto one physical mock-up, to handle different mechanical behaviors of the virtual patients, and to allow interactive modifications of the virtual structures, while the physical counterparts remain unchanged. Various practical examples underline the wide applicability of our approach. To the best of our knowledge this is the first practical usage of such a technique in the specific context of interactive medical training.
Many attempts have been made to reproduce theoretically the stress-strain curves obtained from experiments on the isothermal deformation of highly elastic 'rubberlike' materials. The existence of a strain-energy function has usually been postulated, and the simplifications appropriate to the assumptions of isotropy and incompressibility have been exploited. However, the usual practice of writing the strain energy as a function of two independent strain invariants has, in general, the effect of complicating the associated mathematical analysis (this is particularly evident in relation to the calculation of instantaneous moduli of elasticity) and, consequently, the basic elegance and simplicity of isotropic elasticity is sacrificed. Furthermore, recently proposed special forms of the strain-energy function are rather complicated functions of two invariants. The purpose of this paper is, while making full use of the inherent simplicity of isotropic elasticity, to construct a strain-energy function which: (i) provides an adequate representation of the mechanical response of rubberlike solids, and (ii) is simple enough to be amenable to mathematical analysis. A strain-energy function which is a linear combination of strain invariants defined by φ (α)=(a1α+a2α+a3α-3)/α is proposed; and the principal stretches a1,a2 and a3 are used as independent variables subject to the incompressibility constraint a1a2a3=1. Principal axes techniques are used where appropriate. An excellent agreement between this theory and the experimental data from simple tension, pure shear and equibiaxial tension tests is demonstrated. It is also shown that the present theory has certain repercussions in respect of the constitutive inequality proposed by Hill (1968a, 1970b).
Conference Paper
A novel magnetic type tactile sensor is proposed. This sensor can measure a three-axis force vector and detect a slip. The structure is simple, and this sensor consists of two layers, an elastic layer and a substrate layer. The elastic layer is made of an elastic material and has a cylindrical permanent magnet. The substrate layer is a glass epoxy board and has four GMR(giant magneto resistance) elements and four chip inductors. Each element outputs voltages as to a magnetic flux density when the elastic layer deforms by a contact. A force vector and a slip detection are calculated from these outputs. Laboratory experiments demonstrate the effectiveness of this tactile sensor.
Conference Paper
The aim of this study is the development of a human-friendly tactile sensor for measuring softness, sliminess, smoothness, and so on. We have proposed active tactile sensing method using balloon expansion. A balloon is contacted with an object and expanded by using fluid. Tactile information is evaluated by measuring the expansion process. In this paper, we developed a sensor system using syringe. It is a compact system and can ensure enough safety for human body tissues in safe contact, using no electric power, and sterilization. Pressure changes and volume changes of the balloon can be measured together in the balloon expansion. First, overview of the developed sensor system is presented. Next, composition of the sensor system and the sensing process are presented. Then, experiments using the developed sensor are conducted on samples with different stiffness and surface conditions. Features extracted from sensor outputs indicate that the sensor can know the difference both the stiffness and surface condition. The results show the validity of the proposed sensor system.
Conference Paper
We explain when, and why, solder-based phase change materials (PCMs) are best-suited as a means to modify a robotic mechanism's kinematic and elastomechanic behavior. The preceding refers to mechanisms that possess joints which may be thermally locked and unlocked via a material phase change within the joint. Different combinations of locked and unlocked joints can yield several one-DOF mechanisms states. One actuator may be used to control motion allowed by a first state, then a new combination of locked/unlocked joints may be set and the actuator then controls motion allowed by the new state. Compared to other thermo-rheological fluids, solders yield joints with the (i) highest strength and stiffness, (ii) fastest lock/unlock speed, and (iii) lowest lock/unlock power. Herein, we cover physics-based design insights that provide understanding of how solder-based material properties and joint design dominate/limit joint performance characteristics. First order models are used to demonstrate selection of suitable PCMs and how to set initial joint geometry prior to fine tuning via detailed models/experiments. The insights and models are discussed in the context of a joint for a crawling robot that uses a single spooler motor and three solder-locking joints to crawl and steer.
Article
Despite the potential utility of clinical breast examination (CBE), doctors' palpation skills are often inadequate and difficult to train. CBE sensitivity ranges from 39-59%, in part because current training does not effectively teach tactile skills. To address CBE training limitations, we developed a breast examination training model with 15 dynamically controlled lumps, set to desired hardness within underlying rib and muscle structures, in a silicone breast. In an experiment of 48 medical students, training with the dynamic model increased lump detection by 1.35 lumps compared to 0.60 lumps for a traditional breast model (P=0.008), reduced false positives by -0.70 lumps compared to +0.42 lumps (P=0.0277), and demonstrated skill transfer with a 1.17 lump detection improvement on the traditional device compared to only a 0.17 lump detection improvement by traditional device trainees on the dynamic device (P<0.001). Findings demonstrate the advantage of the dynamic model over conventional models in training CBE tactile skills.
Bates' guide to physical examination and history-taking
• L Bickley
• P Szilagyi
L. Bickley and P. Szilagyi, Bates' guide to physical examination and history-taking, 12th ed. Philadelphia : Wolters Kluwer, 2012, vol. 13.
Virtual reality training for the diagnosis of prostate cancer
• G Burdea
• G Patounakis
• V Popescu
• R E Weiss
G. Burdea, G. Patounakis, V. Popescu, and R. E. Weiss, "Virtual reality training for the diagnosis of prostate cancer," Ieee 1998 Virtual Reality Annual International Symposium, Proceedings, vol. 46, no. 10, pp. 190-197, 1998.
Elasticity versus hyperelasticity considerations in quasistatic modeling of a soft finger-like robotic appendage for real-time position and force estimation
• A Shiva
• Y Noh
• J Fra
• A Ataka
• H Wrdemann
• H Hauser
• I D Walker
• T Nanayakkara
• K Althoefer
A. Shiva, S. H. Sadati, Y. Noh, J. Fra, A. Ataka, H. Wrdemann, H. Hauser, I. D. Walker, T. Nanayakkara, and K. Althoefer, "Elasticity versus hyperelasticity considerations in quasistatic modeling of a soft finger-like robotic appendage for real-time position and force estimation," Soft Robotics, vol. 6, no. 2, pp. 228-249, 2019, pMID: 30702390.
Nonlinear solid mechanics ii
• A G Holzapfel
A. G. Holzapfel, "Nonlinear solid mechanics ii," 2000.
ser. Prentice Hall information and system science series
• L Ljung
L. Ljung, System identification : theory for the user, 2nd ed., ser. Prentice Hall information and system science series. Upper Saddle River, N.J. ; London: Prentice Hall, 1998.