Abstract: Addressing on the uncertainty problems resulting from the parametric perturbation and the modeling error existing in the electric servo mechanism, the robust control technology for a class of electric servo mechanism used to drive the load with large inertia and low stiffness in aircrafts is researched via μ synthesis theory. For this class of electric servo mechanism, modeling according to one-DOF system will bring about big deviation. In order solving the problem, its two-DOF mathematic model is built by analyzing the dynamic characteristic of thrust vector control electric servo mechanism. Aiming at the performance requirements of controlled plant in position command tracking and torque disturbance restraint, the μ synthesis controller is designed by managing parametric perturbation and modeling error, whereas an optimization design method of weighting functions is put forward. The closed-loop system with μ synthesis controller in the normal case and the positive & negative perturbations is simulated by using MATLAB software, and its control performances are researched and compared with the performances of H∞ controller. The simulation results show that for this class of servo mechanism, the μ synthesis controller can effectively improve the conservative results of H∞ controller with condition of selecting the same weighting functions, and can make the closed-loop system not only have preferable performance robustness but also satisfy the requirements of dynamic performance targets for controlling system. The proposed optimization design method of weighting functions is good for the application of robust control technology in engineering field.

Key words: Disturbance restraint, Electric servo mechanism, Large inertia and low stiffness load, Robust control, Thrust vector control, μ synthesis