Active damping in precision equipment using piezo

In this paper, the rotational vibration in the linearly actuated precision machines with low damping is discussed. This so called Rocking mode is e.g. caused by the compliance in the guiding system of a linear actuator and leads to a long settling time of the end-effector. Another problem occurs when a feedback motion controller is applied to the plant. Complex poles present in the loop transfer that are close to the imaginary axis due to low damping, are destabilized by a relatively small gain. A possible solution is actively damping the resonance frequencies. By flattening the resonance peaks, the bandwidth of the system can increase without the danger of instability. In turn, this allows for higher integral gain in the motion control algorithm.