This thesis is concerned with the design of a digital electrohydraulic servomechanism and the position control of an electrohydraulic servo motor system under parameter variation.
Digital electrohydraulic servomechanism for educational experiments has been designed and constructed; the experiments include performance tests of hydraulic components, and static and dynamic performance tests of hydraulic servo systems such as servovalve-motor combination, servovalve-cylinder combination, load simulator system, etc.
For the position control of the servovalve-motor combination, a cascade control is proposed to design a robust controller for fast and accurate control of the system; the casacde control utilizes an inner pressure control loop. It is shown experimentally that cascade control algorithm is robust and effective in attaining fast and accurate position control of the system under hydraulic supply pressure variation. It is also shown that transient response of the cascade control system can be improved when system inertia varies.
