Ludovic Dovat

HandCARE : A Cable-Actuated Rehabilitation System to Train Hand Function After Stroke

We have developed a robotic interface to train hand and finger function. HandCARE is a Cable-actuated rehabilitation system, in which each finger is attached to an instrumented cable loop allowing force control and a predominantly linear displacement. The device, whose designed is based on biomechanical measurements, can assist the subject in opening and closing movements and can be adapted to accommodate various hand shapes and finger sizes. Main features of the interface include a differential sensing system, and a clutch system which allows independent movement of the five fingers with only one actuator. The device is safe, easily transportable, and offers multiple training possibilities. This paper presents the biomechanical measurements carried out to determine the requirements for a finger rehabilitation device, and the design and characterization of the complete system.

A Haptic Knob for Rehabilitation of Hand Function

This paper describes a novel two-degree-of-freedom robotic interface to train opening/closing of the hand and knob manipulation. The mechanical design, based on two parallelogram structures holding an exchangeable button, offers the possibility to adapt the interface to various hand sizes and finger orientations, as well as to right-handed or left-handed subjects. The interaction with the subject is measured by means of position encoders and four force sensors located close to the output measuring grasping and insertion forces. Various knobs can be mounted on the interface, including a cone mechanism to train a complete opening movement from a strongly contracted and closed hand to a large opened position. We describe the design based on measured biomechanics, the redundant safety mechanisms as well as the actuation and control architecture. Preliminary experiments show the performance of this interface and some of the possibilities it offers for the rehabilitation of hand function.

Effects of a robot-assisted training of grasp and pronation/supination in chronic stroke: a pilot study

BackgroundRehabilitation of hand function is challenging, and only few studies have investigated robot-assisted rehabilitation focusing on distal joints of the upper limb. This paper investigates the feasibility of using the HapticKnob, a table-top end-effector device, for robot-assisted rehabilitation of grasping and forearm pronation/supination, two important functions for activities of daily living involving the hand, and which are often impaired in chronic stroke patients. It evaluates the effectiveness of this device for improving hand function and the transfer of improvement to arm function.MethodsA single group of fifteen chronic stroke patients with impaired arm and hand functions (Fugl-Meyer motor assessment scale (FM) 10-45/66) participated in a 6-week 3-hours/week rehabilitation program with the HapticKnob. Outcome measures consisted primarily of the FM and Motricity Index (MI) and their respective subsections related to distal and proximal arm function, and were assessed at the beginning, end of treatment and in a 6-weeks follow-up.ResultsThirteen subjects successfully completed robot-assisted therapy, with significantly improved hand and arm motor functions, demonstrated by an average 3.00 points increase on the FM and 4.55 on the MI at the completion of the therapy (4.85 FM and 6.84 MI six weeks post-therapy). Improvements were observed both in distal and proximal components of the clinical scales at the completion of the study (2.00 FM wrist/hand, 2.55 FM shoulder/elbow, 2.23 MI hand and 4.23 MI shoulder/elbow). In addition, improvements in hand function were observed, as measured by the Motor Assessment Scale, grip force, and a decrease in arm muscle spasticity. These results were confirmed by motion data collected by the robot.ConclusionsThe results of this study show the feasibility of this robot-assisted therapy with patients presenting a large range of impairment levels. A significant homogeneous improvement in both hand and arm function was observed, which was maintained 6 weeks after end of the therapy.

A 2-DOF fMRI compatible haptic interface to investigate the neural control of arm movements

This paper describes a two-degrees-of-freedom haptic interface to investigate the brain mechanisms of human motor control, which is capable of safely and gently interacting with human arm motion during functional magnetic resonance imaging (fMRI). A hydrostatic transmission separates the interface into a master and an MR compatible slave system, allowing the placement of all interfering components outside the electromagnetic shield of the MR room. The transmission mirrors force and motion of the master actuators on the slave system placed close to the MR scanner. The parallel architecture takes advantage of the linear MR compatible actuators and allows human subjects to perform reaching movements comfortably in the small workspace limited by the dimensions of the MR scanner and the biomechanics of the arm. The kinematic structure of the slave interface was optimized with respect to the available space and types of movements to be investigated. Materials were chosen based on their MR compatibility, their stiffness and weight. The interaction force with the subject is measured over two optical force sensors, located close to the output of the interface. Two shielded optoelectronic encoders measure the extension of the slave hydraulic pistons. Detailed tests demonstrated the fMRI compatibility even during movement of the interface

A Haptic Knob for Rehabilitation of Stroke Patients

The strong impairment of motor functions in stroke survivors affects daily activities such as eating, manipulating objects or writing. Our goal is to induce long lasting improvements in such tasks by having patients perform systematic exercises using haptic interfaces. This paper describes a novel two-degrees-of-freedom interface which we have developed to help stroke patients gradually recover the ability to open and close the hand and manipulate knobs. Different solutions are studied and a design consisting of two parallelogram structures interacting with the fingers is proposed. The mechanical design offers the possibility to adapt the interface to various hand sizes and finger orientations, and to right or left-handed subjects. Design kinematics as well as actuation and system control are described. Several knobs are proposed to interact with patients, especially a cone mechanism to train a complete opening movement from a strongly contracted and closed hand to a large opened position. The interaction force with the subject is measured over four force sensors located close to the output of the interface. A preliminary study has been performed to evaluate the performances of the haptic interface

Rehabilitation of grasping and forearm pronation/supination with the Haptic Knob

This paper investigates robot-assisted rehabilitation after stroke using the Haptic Knob, a 2 degree-of-freedom end-effector based robotic device to train grasping and wrist pronation/supination. Nine chronic stroke subjects trained over a period of 6 weeks, with 3 one-hour sessions of robot-assisted therapy per week, consisting of two exercises requiring active participation promoted by therapeutic games. Results of standard clinical assessments demonstrate the positive effects of robot-assisted therapy with the Haptic Knob. Subjects improved by a mean of 4.3 points in the Fugl-Meyer assessment scale, together with a decrease in hand impairments such as abnormal muscle tone frequently observed in stroke subjects. Significant improvements were also observed in motor function of the upper arm as a result of the robot-assisted therapy, suggesting homogeneous improvement of upper limb function as a result of distal training.

Development of a Robot-Assisted Rehabilitation Therapy to train Hand Function for Activities of Daily Living

This paper presents the evaluation of a new two degree-of-freedom robotic interface, and the development of exercises to train movements and force control of wrist and hand. The Haptic Knob has two actuated parallelogram structures with a knob at the output, to interact with the fingers in a way to simulate grasping/releasing, in combination with pronation/supination movements of the forearm. Motivating game-like exercises have been designed according to a functional approach, where fundamental hand function required in activities of daily living (ADL) can be trained, while the device provides assistive or resistive forces. Preliminary testing has been performed with healthy subjects and three chronic stroke patients. Subjects found the exercises to be comfortable, and the robotic interface offers adequate range of motion and forces. A study with a group of chronic stroke patients will be conducted during the next months to determine the potential benefit of a therapy using our robotic equipment.

A Cable Driven Robotic System to Train Finger Function After Stroke

This paper presents a novel robotic interface to train intrinsic finger movements. The mechanical design, base on a cable system interacting with the fingers, offers the possibility of adapting the interface to accommodate various hand sizes and finger orientation. A main feature of the device is a clutch system, which consists of five clutches, one for each finger, that can be switched to three different modes: ( rest mode: the fingers are mechanically maintained at a fixed position, (ii) passive (from the view of the interface) mode: the finger is free to move along the path defined by the cable, and (iii) active mode: the force generated by the motor is applied to the finger.) With this mechanism, it is possible to train hand muscle function using only one actuator. The interaction wit the subject is measured by means of a position encoder an five force sensors located close to the output. We describe the human-oriented design of our underactuated robotic interface based on measured biomechanics. We detail the redundant safety mechanisms, the actuation, sensing and control system and report the performance and preliminary results obtained with this interface.

A technique to train finger coordination and independence after stroke.

Purpose. Finger coordination and independence are often impaired in stroke survivors, preventing them from performing activities of daily living. We have developed a technique using a robotic interface, the HandCARE, to train these functions. Method. The Hand Cable-Actuated REhabilitation (CARE) system can assist the subject in opening and closing movements of the hand, and can be adapted to accommodate various hand sizes and finger shapes. Results. Two game-like exercises have been developed, which use a motivating approach to promote recovery of finger coordination and independence. Mathematical measures have been implemented to evaluate these functions. This technique is validated with two post-stroke subjects who practiced for 20 minutes twice a week during eight weeks. Conclusions. The results show significant improvements in finger coordination, force modulation as well as finger independence.

Post-stroke training of a pick and place activity in a virtual environment

Picking up and moving small objects is one of the impaired functions stroke survivors most desire to recover. Indeed, this action is involved in many activities of daily living and is often difficult for stroke patients who have problems in (i) grasping the object, (ii) lifting the hand, and (iii) producing a straight trajectory. We have developed a ldquopick & placerdquo exercise using motivational feedback to promote recovery of these functions. This exercise consists of moving an object within a virtual environment where different parameters can be modified to increase the level of difficulty, e.g. a virtual obstacle can be placed in the middle of the workspace which forces the subject to lift the hand in order to reach a target position. The virtual environment is rendered by a Delta workstation that can accurately measure positions and generate forces. To evaluate the training with the ldquopick & placerdquo exercise, three post-stroke subjects practiced twice a week during eight weeks with the setup. The results show a significant decrease in time required to perform the task for the three subjects, while the movements become straighter with training.