The influence of temperature on PZT sensors & actuators for active vibration control of flexible structures

In real operating environments, flexible structures exhibiting dynamic oscillations such as aircraft and spacecraft can experience large changes in temperature during their normal operating cycle, typically in the range -70 to 80 degrees Celsius. The use of piezoelectric actuators and sensors to control these dynamic oscillations have been widely explored at constant temperature, although only limited studies have been conducted on the effect that varying temperature has on the active control of flexible structures.

The objective of this research is to study the influence of PZT sensors and actuators for vibration control of flexible structures where nonlinearities in piezoelectric and structural material properties change as the system temperatures vary significantly with time. This involved the development of a set of data based parameters that enabled the accurate modelling of a nonlinear flexible system in which its dynamics are actively controlled via the use of piezoelectric sensors and actuators. These parameters determined the design of a control scheme to actively control the system over a large range of operating temperatures, and give an optimised control performance throughout its operating regime.

The work reported in this thesis describes selected methods for rapidly examining a number of the more common nonlinear properties of PZT associated with vibration control. An extensive numerical and experimental investigation is performed which shows that when used in active vibration control applications, the variations in PZT properties with temperature can ultimately affect the ability of the piezoelectric actuator and sensors to suppress vibration in flexible structures.

Accurate simulation models of the lightweight piezo-actuated cantilevered structures were developed to evaluate the performance of a number of common vibration control schemes subject to significant temperature variations. This research was then extended to an innovative scaled wing-type structure subjected to temperature variations. A suitable adaptive self-tuning control scheme was developed and investigated numerically and experimentally, illustrating the benefit of adaptive control in this instance. The adaptive control technique was shown numerically and experimentally to provide improved settling times and damping ratios over equivalent fixed gain controllers for the class of structures investigated where limited control authority exists.

The experimental investigation of PZT sensors and actuators has provided further understanding of the nonlinear behaviour of various light, flexible structures where temperature effects on the system dynamics and control are significant. This research has unveiled previously unreported nonlinearities and has expanded on traditional nonlinearities. These results can assist with the detailed design of applications involving PZT sensors and actuators in for example the aerospace and automotive industries.