Year

2008

Degree Name

Doctor of Philosophy

Department

School of Mechanical, Materials and Mechatronic Engineering

Abstract

Actuators based on conducting polymers are promising new devices, given their unique combination of low-voltage activation, high peak stresses and strains, bio-compatibility and manufacturability down to the micro-scale. Trilayer benders are laminated conducting polymer actuators that produce a bending motion, with self-contained operability in both air and liquid environments, but their dynamic behaviour has not been fully characterised and few positional control systems developed. To help enable the use of these actuators in functional devices, this thesis systematically characterises and models the bending displacement and then applies this information to develop a positional control system. The displacement of the actuator tip has been characterised in terms of step displacement and as a function of frequency for a range of actuator geometries, external loadings and operating conditions. System identification techniques are used to identify empirical transfer function models from the actuator frequency response, which are shown to accurately simulate time-domain displacement for step and dynamic voltage inputs and can be applied to all the tested actuator configurations. A second model is derived and validated, which links the resonant frequency to the mechanical properties of the trilayer bender actuator. The transfer function model is then used to develop an inversion-based positional control system, which is shown to significantly improve the displacement speed and positioning ability without the use of a feedback sensor. The understanding and control of conducting polymer trilayer actuators has been increased as a result of this work, improving their potential for use in functional devices.

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