Experimental demonstration of input preconditioning for residual vibration suppression using low-pass FIR digital filters

A method for suppressing residual vibrations in flexible systems is presented and experimentally demonstrated. The proposed method is based on the preconditioning of the inputs to the system using conventional low-pass FIR digital filters. Several classes of FIR filters such as: a) Parks-McClellan; b) window-based method (using Chebyshev window); and c) constrained least squares method, are shown to demonstrate excellent vibration suppression when they are properly designed while they introduce minimum possible delay. In order to ensure maximally robust behavior, the filter stop band is selected to cover all possible variations of the system dynamic parameters. The proposed method does not require modeling of the flexible system, can be used in a variety of systems exhibiting vibrations, is independent of the guidance function, is simple to implement in practical applications and robust to variations of the system dynamic parameters. The method is experimentally verified using a flexible aluminum beam attached at the end-effector of a robot manipulator. The beam is rotated, using one joint of the manipulator, from an initial to a final position. During this motion, vibrations of the beam are excited due to inertial forces. It is shown that the preconditioned inputs to the flexible system induce very little amount of residual vibrations compared to the inputs with no preconditioning.