A Novel Motion Control Design Approach Based On Active Disturbance Rejection

A new digital control solution to motion control problems is proposed. It is based on a unique active disturbance rejection concept, where the disturbances are estimated using an extended state observer (ESO) and compensated in each sampling period. The dynamic compensation reduces the motion system to approximately a double integrator which can be easily controlled using a nonlinear proportional-derivative controller. The proposed Active Disturbance-Rejection Controller (ADRC) consists of the ESO and the nonlinear PD controller and is designed without an explicit mathematical model of the plant. Hence the controller is inherently robust against plant variations. Through simulation, frequency response analysis, and hardware tests, it is shown that the proposed approach is superior to the current PID based technology. It stands out especially in handling set point change, large inertia and friction variations, and external torque disturbance, all of which is seen as “disturbance” by ADRC and is actively compensated. The improvement in transient response and steady state error is also quite evident.