Mechanical resonance suppression method based on active disturbance rejection control in two-mass servo system

A method for suppressing the mechanical resonance of servo drives in a two-mass system coupled with a flexible shaft is proposed. Active disturbance rejection control considers the disturbance component of all torques, except for the torque of the moment of inertia of the drive motor, as the total disturbance, which is estimated using an extended state observer. In this paper, we use reduced-order active disturbance rejection control (RADRC) based on a reduced-order extended state observer to lower the order of the observer's gain. RADRC can reduce the order and thus increase the observer’s bandwidth. In addition, by lowering the moment of inertia of the drive motor used in the observer, the observer’s bandwidth can be increased, and the stability of the servo system can be ensured. The speed controller uses only the P controller to reduce the magnitude of the overshoot for the step response. To accurately reflect the system, the proposed method was designed in the discrete time domain. As a result, the proposed method can reliably suppress vibrations caused by the resonance of the mechanical system. Simulations and experiments on a 1.1 kW surface-mounted permanent magnet synchronous motor confirmed the effectiveness of the proposed method.