Stability, gain and sampling time of discrete time acceleration control loop

Servo control is realized by position, speed and current control loops. To further improve the robustness of the servomechanism, acceleration control in the minor loop of a speed control loop was effectively proposed. However, the necessary gain of acceleration control loop and necessary bandwidth of acceleration sensing has not been studied and no practical guidelines for the design of acceleration control loop were given. In this paper, the authors present the guidelines to design the acceleration control loop and analyze stability and damping of the acceleration control loop realized in discrete time. Conditions for the gain and sampling time to achieve stable and non-vibrational response are given. It is shown that short sampling time is crucial to realize sufficient gain and damping of acceleration control loop. Influence of current control loop to the acceleration control loop's response is also studied. It is shown that difference in the bandwidths of current control and acceleration sensing is indispensable for nonvibrational response.