Abstract
In this paper, a compensation method of disturbances using a disturbance observer is proposed for a force control of a pneumatic robot manipulator. The generated torque by a pneumatic actuator can be estimated based on the pressure signals. The inner torque control system is constructed by feeding back the generated torque to improve the dynamic characteristics of the actuator. In order to reduce the influence of disturbances comprising friction torque, parameter variations of plant and environment and so on, the reaction torque control system is constructed with a disturbance observer which estimates the disturbances based on the reference input to the inner torque control system and the reaction torque sensed with a force sensor. Further, to control the reaction torque without a force sensor, we construct the reaction torque estimation observer using the generated torque, the nominal friction torque and the angular velocity. In the above reaction torque control system, the estimated reaction torque is used instead of the sensed torque, so that the force sensorless torque control system can be constructed. From some simulations and experiments, it is confirmed that the proposed control system is effective to improve the robustness for the friction torque and the parameter change of object in the force control of a pneumatic robot manipulator.
