A servo-drive with an integral disturbance observer filter. Part 2: Position control

The paper brings second part of an analysis and synthesis of servo-drives with integral low-pass disturbance observer (DO) filters. The loop established by extending a stabilizing PD-controller by a binomial noise attenuation filter and by a disturbance reconstruction and compensation is devoted to the position control. The dominant loop dynamics represented by an inertial mass is approximated by a second-order integrator. The torque generator dynamics, together with the processing and communication delays are approximated by a dead-time. The solution proposed is compared with a DO based solution using binomial filters both in the disturbance reconstruction and in the stabilizing feedback (DO-FPID) and with a traditional cascaded P-PI structure without additional filters. The output position is considered to be measured by an incremental encoder. Impact of the filter parameters and of the sampling period on the resulting control performance are being explored. The solution using combination of both basic types of low-pass filters shows a significantly improved loop performance.