Robustness comparison of control schemes with disturbance observer and with acceleration control loop

In this paper, we analyze performances of a servo control system with acceleration control loop inside of a speed control loop. We evaluate robustness of such a system in comparison to robustness of a robust control system by using a disturbance observer. The results suggest that robustness against the system´s parameters variations is superior in the case of servo control with an acceleration control loop included. Additionally, disturbance suppression is much higher (-50 dB attenuation compared to -20 dB) even at low gain of the acceleration control loop and with the low bandwidth acceleration sensor used. The system´s response and its robustness against the disturbances are studied in dependence of the acceleration control loop´s gain and of the bandwidth of an acceleration sensor. Simulation examples are shown