An experimental investigation into active damage control systems using positive position feedback for AVC

Abstract

This work discusses the use of Positive Position Feedback (PPF) for Active Vibration Control as part of an Active Damage Control System (ADCS). Vibration control increases the fatigue life of a structure and decreases the in-plane stresses that can cause delamination in a composite. PPF is a collocated direct-output feedback control method that increases the effective damping in a structure. A simply-supported beam was used as the testbed which used strain gages as the sensing element and piezoelectric ceramics as the actuator.

Initial investigations into sampled-data systems using PPF are presented. The issues addressed are: stability of the sampled system, the effects of the sampling rate on the system, and degradation from predicted analog performance. A digital design procedure for the tuning filters in the Z-plane is suggested if the sampling rate to be used is known. If the sampling rate varies significantly, to avoid redesigning the filters for each new sampling rate, they should be designed in the continuous-time and transformed to the Z-plane. The Tustin transformation was found to adequately map the poles and zeros of the compensator to the Z-plane for digital control.

Experimental implementation of PPF on a simply-supported beam resulted in vibration suppression of three modes with a S180 controller. The beam was subjected to both a single-frequency harmonic disturbance and a broadband harmonic disturbance. One, two, and three-mode controllers were designed with disturbance suppression up to 15dB achieved.