Vibration Control with Phase Compensation of Tip Acceleration in a Flexible Slewing Arm

Abstract

To suppress harmful parasitic vibrations in feedback control loop of a robot arm or flexible structures, a standard framework is based on sensor-actuator collocated configurations. In the case where the inertia on the load side is small, the sensor on the drive side may never detect vibration, and an effective design scheme is required to be developed which make use of remote sensors spatially separated from the actuator. It is well known that such a system is non-minimum phase and hard to design trade-offs between high nominal performance and robustness against some plant perturbations. This paper presents an approach to noncollocated vibration control using tip acceleration in a flexible slewing arm. The rigid body model of the arm is employed as a nominal model, and a tuning rule of the time delay in the phase compensator for vibration suppression is proposed focusing on the IMC (Internal model control) structure. The measured tip acceleration is provided with a phase compensator that consists of a time delay and bandpass filter for the vibration modes to be damped, and the dead time is designed so that the loop transfer function is around the positive real axis at the resonance frequency. This makes the Nyquist plot of the loop transfer function move away from the critical point, -1, to improve the disturbance suppression performance, and the performance deterioration is less likely to occur due to the uncertainty of the resonance frequency. Simulation and experimental study illustrate that effective vibration suppression is performed by using a tip accelerometer under disturbances and tip mass perturbations.