Chapter 5 - Disturbance observer applications in rehabilitation robotics: an overview

Abstract

Numerous robotic devices have been developed for patient rehabilitation and physical assistance. Developing efficient and safe control algorithms for having seamless interaction between these robotic devices and the patients is of crucial importance for restoration of motion in both upper and lower extremities. A prevalent challenge in control of rehabilitation robotic devices is the simultaneous presence of disturbances, which degrade the performance of the control system, and persistent human inputs during human–robot interaction that might act as disturbances on the rehabilitation wearable robot. Furthermore, in any application where the human and the robotic device are interacting with each other, measuring the interaction forces becomes of crucial importance for guaranteeing the performance and safety of the rehabilitation robot control system. However, there are certain drawbacks when force sensors are employed in the rehabilitation robot control system such as their narrow bandwidths and increase in the rehabilitation system cost. A recent cost-effective alternative to inclusion of force sensors in the rehabilitation robotic device is based on sensorless force estimation, whereby the forces due to the human–robot interaction are estimated using disturbance observers. As an alternative for force/torque sensors, disturbance observers can provide the robot control system with information about the patient–robot interaction forces as well as unknown disturbances. This chapter presents a detailed overview of disturbance observer applications in rehabilitation robotics for upper/lower extremity rehabilitation and telerehabilitation, while underscoring the practical challenges that are associated with the application of disturbance observers to rehabilitation robot control systems.