Andreas Wege

Development and control of a hand exoskeleton for rehabilitation of hand injuries

Hand injuries are a frequent problem. The great amount of hand injuries is not only a problem for the affected people but economic consequences follow because rehabilitation takes a long time. Physical therapy after an operation is associated with high personnel expenses. To improve therapy results and reduce cost of rehabilitation a hand exoskeleton was developed. The hand exoskeleton was specifically designed to accomplish requirements of medical applications. For research on control algorithms and rehabilitation programs a prototype supporting all four degrees of freedom of one finger was build. The device can be easily attached and also be adjusted to deformed and scarred hands. In view of the fact that a lot of hand injuries affect only one finger, this prototype could already be functional in physical therapy. This paper presents the construction and the control system of the hand exoskeleton and possible applications in therapy of hand injuries. For the position control a PID controller was implemented and evaluated. The resulting control system allows following of recorded trajectories with sufficient accuracy.

Application of EMG signals for controlling exoskeleton robots.

Abstract Exoskeleton robots are mechanical constructions attached to human body parts, containing actuators for influencing human motion. One important application area for exoskeletons is human motion support, for example, for disabled people, including rehabilitation training, and for force enhancement in healthy subjects. This paper surveys two exoskeleton systems developed in our laboratory. The first system is a lower-extremity exoskeleton with one actuated degree of freedom in the knee joint. This system was designed for motion support in disabled people. The second system is an exoskeleton for a human hand with 16 actuated joints, four for each finger. This hand exoskeleton will be used in rehabilitation training after hand surgeries. The application of EMG signals for motion control is presented. An overview of the design and control methods, and first experimental results for the leg exoskeleton are reported.

Mechanical design and motion control of a hand exoskeleton for rehabilitation

Hand injuries are a frequent problem. The great amount of hand injuries is not only a problem for the affected people but economic consequences follow because rehabilitation takes a long time. To improve therapy results and reduce cost of rehabilitation a hand exoskeleton was developed. For research on control algorithms and rehabilitation programs a prototype supporting all four degrees of freedom of one finger was built (s. Fig. 1). In view of the fact that a lot of hand injuries affect only one finger, this prototype could already be functional in physical therapy. A robust sliding mode controller was proposed for motion control of the hand exoskeleton. The performance of the controller was evaluated for step response. In a second experiment varied forces where applied during the sensor was set to hold a constant position. Finally the controller was set to follow a complete trajectory.

Force Control Strategy for a Hand Exoskeleton Based on Sliding Mode Position Control

This paper presents a force-based control mode for a hand exoskeleton. This device has been developed with focus on support of the rehabilitation process after hand injuries or strokes. As the device is designed for the later use on patients, which have limited hand mobility, fast undesired movements have to be averted. Safety precautions in the hardware and software design of the system must be taken to ensure this. The construction allows controlling motions of the finger joints. However, due to friction in gears and mechanical construction, it is not possible to move finger joints within the construction without help of actuators. Therefore force sensors are integrated into the construction to sense force exchanged between human and exoskeleton. These allow the human to control the movements of the hand exoskeleton, which is useful to teach new trajectories or can be used for diagnostic purposes. The force control scheme presented in this paper uses the force sensor values to generate a trajectory which is executed by a position control loop based on sliding mode control

Development and Control of a Hand Exoskeleton for Rehabilitation

Hand injuries are a frequent problem. The great amount of hand injuries is not only a problem for the affected people but economic consequences follow because rehabilitation takes a long time. To improve therapy results and reduce cost of rehabilitation a hand exoskeleton was developed. For research on control algorithms and rehabilitation programs a prototype supporting all four degrees of freedom of one finger was build (s. Fig. 1). In view of the fact that a lot of hand injuries affect only one finger, this prototype could already be functional in physical therapy. A robust sliding mode controller was proposed for motion control of the hand exoskeleton. The performance of the proposed controller was verified in real experiments and compared to that of traditional PID controller.

Research on Exoskeletons at the TU Berlin

We present an overview of the work devoted to exoskeletons which has been performed for the last seven years at TU Berlin. Three different types of exoskeleton devices have been developed: hand and finger exoskeletons for rehabilitation, a leg exoskeleton for motion support, and an arm exoskeleton for multimodal human-computer interaction. The research has been focused on different types of control strategies and algorithms as well as on the implementation of applications. The main part of this work is devoted to using electrical muscle signals for the control systems. We present the concepts for design and application, review the main algorithms and show experimental results and first experience with applications.

Robust Motion Control for Fully Actuated Robots Using Sliding Mode (Robuste Regelung der Bewegung von vollaktuierten Robotern im Gleitmodus)

Summary In the paper the application of known theory for sliding mode control (SMC) to robust motion control for fully actuated robots is considered. In the presented approach the advantages of SMC like robustness and simplicity of the control law are used. At the same time, the main disadvantage of the SMC — chattering — is avoided or at least reduced. Two controllers based on this approach — a controller working in sliding mode (SM) and its approximation with high gain PID-controller — are presented. For the SM-controller a stability proof is given. Both controllers are applicable to a wide class of robots and can be designed without knowledge of the system model. The performances of both controllers are demonstrated in real experiments with a manipulator, inverted pendulum and hand exoskeleton.