Parameters estimation for an upper-extremity rehabilitation robot using force-sensorless method

Rehabilitation is an important healing process to restore range of motion of joint and strength of muscle. Furthermore, robots are applied to increase the efficiency of the rehabilitation process. The basic functions of a rehabilitation robot are assistance and resistance modes. In both functions, gravity and friction compensation are the essential elements for controller design of each mode. The estimation of gravity and friction of the robots and human arms is importance for gravity and friction compensation. Therefore, this paper proposes a method to estimate gravity, friction, and inertia of the robots and human arms by using the adaptive concept of the Reaction Torque Observer. The estimated gravity, friction and inertia can be used for controller design of both assistance mode and resistance mode of the rehabilitation robots. This method can be used to identify the gravity term of the robot and human arm with high accuracy when compared other methods. The friction also can be identified using this method. However, estimation of the robot inertia appears to be having an error of 69.075%.