In this study, the position control of an electro-hydraulic and electro-pneumatic servosystem under the variations of inertia and external loads has been studied. For this purpose, the Time Delay Control(TDC) was applied to the servosystems and stability analysis was made. New experimental apparatus were made in order to experiment characteristics of the controller. The apparatus was newly included a pneumatic clutch/brake in order to decouple external loads from the motions of driving actuator.
The controller was applied to the electro-hydraulic servosystem and following controls were performed. These were step and regulation response under variation of inertia and external loads, tracking response of ramp and arbitrary input under variation of inertia and external loads.
The results of experiments show that TDC controller achieves a fast and accurate control under inertial variations over wide range of up to about 30 times the design value, and large external loads. The comparative study with a well-tuned PID control shows that the system with TDC is faster and more accurate.
When TDC was applied to hydraulic system with saturating actuator, the windup phenomena appeared. This phenomenon caused excessive overshoot and oscillation. The effectiveness of the anti-windup technique has been shown with experimental results.
The controller was applied to the electro-pneumatic servosystem and following controls were performed. These were step response under inertial variation, substantial external and frictional loads. The results of experiments show that TDC controller achieves an accurate control under inertial variations and external loads. The comparative study with a state feedback control shows that the system with TDC is more accurate.
