Dynamic modelling and vibration suppression of a slewing structure utilizing piezoelectric sensors and actuators

This paper presents preliminary modelling and vibration suppression experiment results for the USAF Phillips Laboratory's Planar Articulating Controls Experiment (PACE) test bed. PACE is a two-link flexible multi-body experiment constrained to move over the surface of a large granite table. In this paper, an approximate analytical dynamic model of a single slewing flexible body with surface bonded piezoelectric sensors and actuators is developed using Hamilton's principle with discretization by the assumed mode method. After conversion to modal co-ordinates, damping is added to the model by including experimental damping measurements. The model is then converted to state-space form for the purpose of control design. The model is verified by comparison of simulated and experimental open loop frequency response data. Both decentralized and centralized controllers are designed for vibration suppression of a single arm of the PACE test bed. The controllers presented in this paper include: a positive position feedback (PPF) controller for controlling the first mode of vibration, a decentralized controller which uses three independent PPF filters for suppressing the first three modes of vibration, and a multiple-input, multiple-output (MIMO) linear quadratic Gaussian (LQG) design. The experiments include both analog and digital implementations of these controllers. Experimental open and closed loop time responses from slew tests are presented as well as open and closed loop frequency response data taken with the PACE arm in a cantilevered state. Significant vibration suppression is achieved using all three controller designs. (C) 1996 Academic Press Limited