Control of Hydraulic Manipulator System Using Disturbance Observer.

This paper proposes an alternative control algorithm for a hydraulic manipulator using disturbance observers. The hydraulic actuators of the manipulator are velocity-controlled by a proportional type flow-control valve. We first model the actuator, which has a disturbance and a time delay in its input, using a discrete-time state space representation. Then we design a disturbance observer for the model with a time delay of n sampling periods in its input. The total control system is synthesized using the observer so that the disturbance to the system is eliminated. The resultant control system is robust against the disturbances to the system, such as mechanical friction and variation of the load of the actuator. Simulation results illustrate the effectiveness of the observer. Finally the proposed method is applied to a hydraulic manipulator with three degrees of freedom and the experimental results demonstrate the validity of the proposed control system.