Adaptive robust force control by disturbance observer

The authors present a robust force control which adapts to wide parameter variances. The disturbances and the parameter variations of motors and the environment are compensated by the force-based disturbance observer discussed. The force controller is based on the controller of the second derivative of a force. In order to realize stable force control for a wide variation of stiffness, identification control based on the least-squares method is introduced. The parameters of the force controller and the disturbance observer are adjusted according to the identified stiffness. Simulation and experimental results show that the adaptive system works well to stabilize force response