Design and Implementation of a 2DOF Robust controller for Servo-Hydraulic Table

Because of high accuracy and low weight-to-force ratio, servo hydraulic systems are widely used in various branches of industry. Simultaneous improvement of accuracy and time response are among ever increasing needs for these systems. Rapid movement commands to hydraulic actuator excite attached mechanical components and consequently produce undesired vibrations. Recommended solution to overcome the above mentioned problem is to design and implement advanced controller which takes into consideration the high frequency uncertainties. In this research a two-degree-of–freedom (2DOF) position controller has been design and implemented for undesirable vibration regulation and robust performance achievement on a servo hydraulic table. In this regard various elements of the system are modeled and then the servo hydraulic table nominal system and uncertainty are identified using grey-box method. The 2DOF robust controller is designed using general H∞ framework and analyzed by structured singular value, Mu. The feedback block of controller is used to reduce the effect of uncertainty, measurement noises and reject disturbances, whereas the forward controller shapes the command signals to improve the performance. The designed controller has been implemented on the servo hydraulic test rig in order to track sine and trapezoid position command signals. It has been observed the controller has a more accurate performance and faster time response than the common robust controller with just one feedback block. Extensive experimental results of the developed controller indicate robust performance and acceptable response to disturbance and measurement noise rejection in the defined uncertainty range.