[Show abstract][Hide abstract] ABSTRACT: In this paper we propose a full upper limb exoskeleton for motor rehabilitation of reaching, grasping and releasing in post-stroke patients. The presented system takes into account the hand pre-shaping for object affordability and it is driven by patient's intentional control through a self-paced asynchronous Motor Imagery based Brain Computer Interface (MI-BCI).
The developed antropomorphic eight DoFs exoskeleton (two DoFs for the hand, two for the wrist and four for the arm) allows full support of the manipulation activity at the level of single upper limb joint.
In this study, we show the feasibility of the proposed system through experimental rehabilitation sessions conducted with three chronic post-stroke patients.
Results show the potential of the proposed system for being introduced in a rehabilitation protocol.
[Show abstract][Hide abstract] ABSTRACT: This paper presents a myoelectric control of an arm exoskeleton designed for rehabilitation. A four-musclesbased NeuroMusculoSkeletal (NMS) model was implemented and optimized using genetic algorithms to adapt the model to different subjects. The NMS model is able to predict the
shoulder and elbow torques which are used by the control algorithm to ensure a minimal force of interaction.
The accuracy of the method is assessed through validation experiments conducted with two healthy subjects performing free movements along the pseudo-sagittal plane. The experiments show promising results for our approach showing its potential for being introduced in a rehabilitation protocol.
[Show abstract][Hide abstract] ABSTRACT: This paper presents a novel electromyography (EMG)-driven hand exoskeleton for bilateral rehabilitation of grasping in stroke. The developed hand exoskeleton was designed with two distinctive features: (a) kinematics with intrinsic adaptability to patient's hand size, (b) free-palm and free-fingertip design, preserving the residual sensory perceptual capability of touch during assistance in grasping of real objects. In the envisaged bilateral training strategy, the patient's non paretic hand acted as guidance for the paretic hand in grasping tasks. Grasping force exerted by the non paretic hand was estimated in real-time from EMG signals, and then replicated as robotic assistance for the paretic hand by means of the hand-exoskeleton. Estimation of the grasping force through EMG allowed to perform rehabilitation exercises with any, non sensorized, graspable objects. This paper presents the system design, development, and experimental evaluation. Experiments were performed within a group of 6 healthy subjects and 2 chronic stroke patients, executing robotic-assisted grasping tasks. Results related to performance in estimation and modulation of the robotic assistance, and to the outcomes of the pilot rehabilitation sessions with stroke patients, positively support validity of the proposed approach for application in stroke rehabilitation.
[Show abstract][Hide abstract] ABSTRACT: In haptic interaction, friction caused by slip on the fingertip is a key factor for manual manipulation as well as exploration of texture and shape. From the moment of contact, the friction contains vertical and tangential skin deformations and vibrations, not all of which have been simultaneously supported by previous portable/wearable haptic devices. We propose a portable haptic device that has the ability to present skin deformation and vibration with two degrees of freedom by using two types of motors: a voice coil motor (VCM) for vertical motion and vibration, and direct current motors for tangential skin stretch. The VCM also achieves encounter-type haptic interactions. A combination of these motions encompasses most cutaneous cues for realistic friction.
[Show abstract][Hide abstract] ABSTRACT: This paper describes the interaction torque control of the Rehab-Exos, an upper-limb robotic exoskeleton with direct torque joint sensors for interaction in Virtual Environments and rehabilitation. The control architecture consists in a centralized torque control and separated optimal torque observers for each joint of the exoskeleton. The optimal observer is a full-state Kalman filter providing the estimates of both internal and external torques acting on the joints and overcoming most of the issues due to the noise in the torque sensor signals. The centralized torque control is based on a full dynamics model of the exoskeleton, calculates the kinematics and dynamics of the system and estimates the feed-forward contribution for the compensation of dynamic loads measured by joint torque sensors. Experimental tests have been carried out to validate the desired torque tracking in haptic interaction tasks.
[Show abstract][Hide abstract] ABSTRACT: This work presents the development and the preliminary experimental assessment of a novel EMG-driven robotic hand exoskeleton for bilateral active training of grasp motion in stroke. The system allows to control the grasping force required to lift a real object with an impaired hand, through the active guidance provided by a hand active exoskeleton, whose force is modulated by the EMG readings acquired on the opposite unimpaired arm. To estimate the grasping force, the system makes use of surface EMG recordings during grasping, developed on the opposite unimpaired arm, and of a neural network to classify the information. The design, integration and experimental characterization of the system during the grasp of two cylindrical objects is presented. The experimental results show that an optimal force tracking of the interaction force with the object can be achieved.
[Show abstract][Hide abstract] ABSTRACT: The Beaming project recreates, virtually, a real environment; using immersive VR, remote participants can visit the virtual model and interact with the people in the real environment. The real environment doesn't need extensive equipment and can be a space such as an office or meeting room, domestic environment, or social space.
No preview · Article · Nov 2012 · IEEE Computer Graphics and Applications
[Show abstract][Hide abstract] ABSTRACT: Although telerehabilitation systems represent one of the most technologically appealing clinical solutions for the immediate future, they still present limitations that prevent their standardization. Here we propose an integrated approach that includes three key and novel factors: (a) fully immersive virtual environments, including virtual body representation and ownership; (b) multimodal interaction with remote people and virtual objects including haptic interaction; and (c) a physical representation of the patient at the hospital through embodiment agents (e.g., as a physical robot). The importance of secure and rapid communication between the nodes is also stressed and an example implemented solution is described. Finally, we discuss the proposed approach with reference to the existing literature and systems.
Full-text · Article · Jul 2012 · Frontiers in Neurology
[Show abstract][Hide abstract] ABSTRACT: This paper deals with a model-based control strategy implemented on an encountered haptic interface developed for the simulation of ball catching tasks. A dynamical model of a reference device has been developed and validated by experimental results. This model was applied to increase the control performance and to simulate realistic impacts. The control strategy to generate the haptic interface trajectories consistent with the simulation of ballistic motion of virtual objects has been defined. At the impact instant the perceptively correct kinetic energy is transferred from the device end-effector to the user hand adopting a velocity scaling rule. Experimental results confirm control accuracy in fast dynamics trajectory tracking.
[Show abstract][Hide abstract] ABSTRACT: This paper investigates the illusory perception of movement induced through visuo-proprioceptive signals and the possibility of control the illusory movement itself through motor imagery.
[Show abstract][Hide abstract] ABSTRACT: This paper presents the development of an interaction-torque control architecture for a rehabilitation exoskeleton (RehabExos) with flexible joints equipped with internal torque sensors. The architecture consists of an outer control loop, which is based on the kineto-statics of the RehabExos, and on four identical-independent inner full-state joint-torque controllers (IJTFC). The considered IJTFC demonstrate good stability, responsiveness and accuracy in tracking the desired torques generated by the outer controller. Comparison with other control strategies available from the literature is shown via analytical and experimental results, which highlight the improved performances of the proposed IJTFC method in controlling the RehabExos robot.
[Show abstract][Hide abstract] ABSTRACT: This paper presents a novel method based on screw theory for the analysis of position accuracy in spatial parallel manipulators with revolute joint clearances. The method is general, and can tackle with an arbitrary pose error function, expressed as a quadratic function of the end-effector displacement.The method performs a maximization of the pose error function, based on a 2-step computational procedure. The first computational step is analytical and leads to a sub-optimal estimate of the maximum pose error. This analytical solution represents the exact maximum pose error for the calculus of the angular accuracy in the special case of fully translational parallel mechanisms. The second computational step is numerical, and starting from the previous solution, can converge to the exact maximum pose error in a limited number of iterations.The relevance of the method is demonstrated through some application examples, where the worst-case angular and linear position accuracy in translating fully parallel manipulators is determined. As a further contribution, this paper shows how the position accuracy due to joint clearances in parallel manipulators is strictly dependent of the mechanism pose and its association to kinematic isotropy.
No preview · Article · Dec 2011 · Mechanism and Machine Theory
[Show abstract][Hide abstract] ABSTRACT: Tangential skin displacement at the fingertip is an effective means of communicating direction or displaying static friction in haptic application. A tactile device capable of stretching the skin of the fingerpad can be mounted directly on the fingertip or embedded in haptic interfaces and hand-held devices. In both cases low weight and small dimensions are important requirements. We have developed a miniaturized tactile device capable of displaying tangential skin displacement in two directions. The actuation for the device is realized by SMA wires, in order to reduce bulk and weight, and the displacements are measured by optical sensors. The performance of the device has been verified experimentally.
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to understand the integration of cutaneous and kinesthetic sensory modalities in haptic perception of shape orientation. A specific robotic apparatus was employed to simulate the exploration of virtual surfaces by active touch with two fingers, with kinesthetic only, cutaneous only and combined sensory feedback. The cutaneous feedback was capable of displaying the local surface orientation at the contact point, through a small plate indenting the fingerpad at contact. A psychophysics test was conducted with SDT methodology on 6 subjects to assess the discrimination threshold of angle perception between two parallel surfaces, with three sensory modalities and two shape sizes. Results show that the cutaneous sensor modality is not affected by size of shape, but kinesthetic performance is decreasing with smaller size. Cutaneous and kinesthetic sensory cues are integrated according to a Bayesian model, so that the combined sensory stimulation always performs better than single modalities alone.
Full-text · Article · Dec 2010 · Brain research bulletin
[Show abstract][Hide abstract] ABSTRACT: In this paper, we present the mechanical design of a new fMRI compatible haptic interface with 3DOFs, based on electrical DC actuation, for the study of brain mechanisms of human motor control. The 1DOF manipulator, which was evaluated successfully on the compatibility with fRMI environment in the preliminary experiments, was extended to the implementation of a 3DOFs parallel manipulator with 3- UPU kinematics. Kinematic properties were studied in different configurations to select the stroke of the prismatic joint and the radius difference between the moving platform and the base. Due to the dimensional constraints imposed by the fMRI environment, the choice of the dimensions and the adopted mechanical solution was a result of an optimization process presented in this work. A further optimization of the mechanical design was then conducted in order to reduce the torque requested to the actuators for gravity compensation and improve the mechanical stiffness with elastic compliance of the manipulator. The final design resulted in a system capable of satisfying all the environment and user requirements.
[Show abstract][Hide abstract] ABSTRACT: A new prototype of portable device for haptic interaction with virtual environments is presented. It is a lightweight interface for the fingertips, designed for providing cutaneous feedback and displaying the contact Â¿ non contact transition in highly immersive virtual environments. The second version of the interface features a force sensor for controlling the force on the fingertip during contact, assuring a better haptic feedback. In this paper the kinematics, the mechanical design and the improved control system are described. The device has been mounted on a kinesthetic haptic interface which tracks its position: in this configuration, the overall system can provide both cutaneous and kinesthetic feedback and improve the fidelity of the haptic interaction. Finally the performance of the cutaneous device in a task of contour following has been evaluated.
[Show abstract][Hide abstract] ABSTRACT: A linear-quadratic-Gaussian regulator is proposed for the torque control of flexible robotic joints with built-in torque sensor. The regulator requires the joint-torque sensor information only and features: (1) a Kalman filter that, beside reducing the noise and evaluating the derivative of the torque sensor measure, is able to estimate all the external and internal torques acting on the joint; 2) a controller that optimizes system stability, responsiveness, accuracy and effort. The regulator is implemented on a flexible joint of a rehabilitation exoskeleton. Simulation and experimental results are provided which demonstrate regulator performance and efficacy.
[Show abstract][Hide abstract] ABSTRACT: A new portable device for haptic interaction with virtual environments is presented. It is a lightweight interface for the fingertips, designed for providing cutaneous feedback and displaying the contact - non contact transition in highly immersive virtual environments. In this paper the kinematics, the mechanical design and the control system are described. The device has been mounted on a kinesthetic haptic interface which tracks its position: the overall system can provide both cutaneous and kinesthetic feedback. Finally the performance of the portable device in a simple task of shape exploration has been evaluated and compared to a kinesthetic haptic interface.
[Show abstract][Hide abstract] ABSTRACT: This paper deals with the development of a novel exoskeleton for the robotic rehabilitation of upper extremities. The system is based on modular custom-designed actuation groups implementing high reduction ratios and redundant position measurement for securing patient safety, and joint torque sensing for guaranteeing system performance and providing application flexibility. Experimental results of the special component prototypes are reported which confirm the validity of the developed actuation groups and the potentials of the proposed exoskeleton architecture.