A servo-drive with an integral disturbance observer filter. Part 1: Speed control

The paper analyses a speed servo-drive with integral low-pass filters applied in the disturbance observer (DO) and in a stabilizing loop with a P-controller. The dominant loop dynamics represented by an inertial mass is approximated by a first-order model. The torque generator dynamics, together with the processing and communication delays are approximated by a dead-time. Two compared approaches focus on reconstruction and compensation of external load disturbances by integral low-pass filters implemented by discrete-time finite-impulse-response (FIR) filters. One of them uses as a disturbance-observer input the generated control signal. The second one has the measured output position at its input. This 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 and compared with a DO using binomial filter and the traditional IP control without an additional filtration.