Optimal placement of flat piezoceramic actuators for feedforward systems under the influence of real-time hardware delays

Abstract

Active vibration control (AVC) systems have been investigated for several decades now. Many researchers have shown that an optimal actuator placement results in an improved performance of the AVC system.In the case of a broadband disturbance, feedback systems are very often used to control plate structures. Detailed optimisation routines for feedback systems that incorporate not only the optimisation of the actuator placement but also the controller design (e.g. feedback gains, H∞-controller) can be found in the literature. Yet, in the case of a feedforward control design for a broadband disturbance, special aspects like causality and coherence limit the performance of an AVC system. The linear quadratic optimal control theory (LQOCT) is very often used to calculate the optimal actuator voltages for the placement of actuators in a feedforward control system. However, the LQOCT completely neglects the causality constraint of a real-time applicable feedforward control system.The aim of this work is to study the influence of analogue and digital signal processing delays on the actuator placement in a feedforward control system under broadband excitation and to improve the predicted performance of an AVC system with optimised actuator placements. Therefore, a pre-design tool is used to optimise the actuator placement and it is shown that the actuator placement changes significantly by the integration of the signal processing delays into the pre-design tool. Due to their frequent use in smart structures piezoelectric patch actuators are used in this study. Furthermore, the optimised actuator placement is used for an experiment with a feedforward controller and shows an improved performance of 3.2dB in the averaged error signal spectrum over a frequency range from 22.5Hz up to 600Hz compared to the actuator placed without signal processing delays.