Active Vibration Isolation Using a Dielectric Electro-Active Polymer Actuator

Dielectric Electro-Active Polymer (DEAP) devices consist of a dielectric polymer sandwiched between two electrodes. This paper describes the use of a tubular DEAP actuator for active vibration isolation. First, the quasi-static and dynamic characteristics of the actuator are discussed. These involve the voltage-strain-force behaviour of the actuator. It is seen that the actuator is inherently non-linear, involving an approximately quadratic relationship between excitation and extension under given loading conditions. In a control context, this can be compensated for either by driving the actuator about some d.c. off-set excitation in a quasi-linear manner, or by including a linearization component within the control. Next, issues concerning the frequency response over a wide range of frequency are considered. Internal resonances exist in the actuator, which limit the bandwidth over which it can be used for active control. The actuator has significant internal damping. The potential for active vibration isolation is then explored. The dynamic performance is limited by the potential bandwidth, the maximum force that can be generated and the maximum range of movement, together with the inherent nonlinearity. Performance for harmonic disturbances is investigated within an adaptive feedforward control scheme. Experimental results are presented. Good attenuation of the excitation frequency is achieved but compensation is required to get good attenuation of higher harmonics introduced by the actuator nonlinearity. Isolation in response to a band-limited random input is then demonstrated, with attenuation of 19dB being achieved over a frequency range from 2-8 Hz.