Realtime performance analysis of different combinations of fuzzy–PID and bias controllers for a two degree of freedom electrohydraulic parallel manipulator

• Development of a 2 DOF electrohydraulic motion simulator as a parallel manipulator.
• Control of heave, pitch and combined heave and pitch motion of the parallel manipulator.
• Design of PID, fuzzy–PID, self-tuning fuzzy–PID and self-tuning fuzzy–PID with bias controllers.
• Use of different combinations of fuzzy–PID and bias controllers for study of real time control performance.
• Best control response found for the self-tuning fuzzy–PID with bias controller.

A two degree of freedom (2 DOF) parallel manipulator in the form of an electrohydraulic motion simulator platform is developed. Pose (heave and pitch) of the platform is achieved by means of two double acting single rod industrial grade hydraulic cylinders. The cylinders are actuated by low cost proportional valves having 15% deadband and 15 Hz natural frequency. The heave motion and the combination of heave and pitch motion of the platform are controlled by a real time controller. Different types of controller, namely proportional integral derivative (PID), hybrid fuzzy–PID, self-tuning fuzzy–PID and self-tuning fuzzy–PID with bias are designed. The real time control performances of the controllers are studied for step and sinusoidal demands of the piston. In order to achieve the required performance of the controller, suitable values for the control parameters are tuned for each controller. It is found that the self-tuning fuzzy–PID with bias controller shows the best control response compared to other controllers for control of the heave, pitch and combined heave and pitch motion.