Robust Tracking Control of Mechanical Servo Systems with Inertial Parameters Varying in a Large Range

When implementing different tasks, mechanical servo systems must adapt to various working loads with different weight or inertia, which may lead to the remarkable varying of servo system´s inertial parameters. However, for such cases, motion control methods at present such as PD control and disturbance observer based robust control design, may exhibit instability or tracking performance´s decline. For the problems mentioned above, a novel nonlinear control scheme, for which the varying range of inertial parameters was supposedly known, was presented. The nonlinear controller is composed of two parts: the PD control design for the reference model system, and the sliding mode control of the mechanical plant. The sliding mode technique was used for servo system to achieve robust stability and guaranteed transient response, and the boundary layer control was adopted to avoid chattering introduced by control switching. The servo system´s global stability is proved by using Lyapunov´s direct method, and the transient performance is analyzed. Computer simulation results developed for a DC motor servo system show the effectiveness of the proposed method