Mixed Sensitivity H? Controller Design for Force Tracking Control of Electro-Hydraulic Servo System

The paper presents the mixed sensitivity H¥ controller design for force tracking control of EHSS (Electro-Hydraulic Servo System). The system is inherently nonlinear and includes hard non linearity like relationship between pressure and flow rate that effect system dynamics and deteriorate the nominal behavior of the system. To cope with such nonlinear function and improve the system performances, a mixed sensitivity H¥ controller is designed using MIXSYN tool in MATLAB. The nonlinear model of EHSS is first linearized into 2nd order LTI (Linear Time Invariant) model and H¥ controller is designed. The weighting filters are included to improve the performance of system. The MATLAB function MAGSHAPE is used to tune the weight functions so that desirable gain and phase margin could be achieved. Simulation results on linear and nonlinear system show the better force tracking as compared to other robust control techniques. The proposed technique is found robust in the presence of disturbance.