Physical constraint-based assessment of acceleration control

The paper is concerned with the acceleration control used by the servo systems to make their behavior robust against load torque and parameter variations. After demonstrating that the Torque Disturbance Observer (TDO) is equivalent to a particular acceleration control, the robustness of a servo system endowed with TDO is analyzed. Then it is shown that the deliberate set-up of a Feedback Acceleration Control (FAC) offers the designer more chances and theoretically brings the robustness of a servo system up to infinite. In practice, the physical constraint on the peak value of the servo current limits the achievable robustness. Taking into account such a constraint, it is proved that, compared to TDO, a suitable design of FAC improves the robustness of a servo system of the ratio between the rated values of peak and dc servo current. Simulation results illustrating the torque disturbance rejection and the current response for the two schemes are reported.