Conducting polymer trilayers are attractive for use in functional devices, given low actuation voltages, operation in air
and potentially useful stresses and strains; however, their dynamic behavior must be understood from an engineering
perspective before they can be effectively incorporated into a design. As a step towards the identification of the actuator
dynamics, frequency response analysis has been performed to identify the magnitude and phase shift of displacement in
response to a sinusoidal voltage input. The low damping of the trilayer operating in air and the use of a laser
displacement sensor has allowed the frequency response to be continuously identified up to 100Hz, demonstrating a
resonant peak at 80Hz for a 10mm long actuator. Two linear transfer function models have been fitted to the frequency
response of the trilayer displacement (i) a 3rd order model to represent the dynamics below 20Hz and (ii) a higher
complexity 6th order model to also include the resonant peak. In response to a random input signal, the 3rd order model
coarsely follows the experimental identified displacement, while the 6th order model is able to fully simulate the real
trilayer movement. Step responses have also been obtained for the 3rd and 6th order transfer functions, with both models
capable of following the first 4 seconds of experimental displacement. The application of empirical transfer function
models will facilitate accurate simulation and analysis of trilayer displacement, and will lead to the design of accurate
positional control systems.
Trilayer polypyrrole benders are capable of generating voltages and currents when applied with an external force or
displacement, demonstrating potential as mechanical sensors. Previous work has identified the effects of dopant and
electrolyte on the sensor output, and a 'deformation induced ion flux' model was proposed. The current work aims to
identify the change in sensor response with input amplitude and bender geometry as a function of frequency. The
current and charge output from the trilayer benders were found to increase proportionally with input displacement and
bender strain for multiple input frequencies, indicating linearity. Sensitivities of the current and charge output have also
been calculated in response to strain, and are found to increase as the volume of the conducting polymer is increased.
Some guidelines for sensor geometry are then suggested, using the identified sensitivities as a guide.
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