Research And Development Of A Resonant Force Sensor Based On IPMC

Ion-exchange Polymer-Metal Composites (IPMC) is a type of electro-deformation smart material. Because IPMC performance is similar to biologic muscle, it is named as artificial muscle. Such material has a lot of advantages, such as light weight, good flexibility and can be cut into arbitrary size, shape and so on. Strips of these composites can undergo large bending and flapping displacement if a electric field is imposed across their thickness, conversely by bending the composite strip, either quasi-statically or dynamically, a voltage is produced across the thickness of the strip. So IPMC are emerging materials used to realize motion actuators and sensors.In this paper a novel force sensor, based on ionic polymer metal composites (IPMC), is presented. The system has DC sensing capabilities and is able to work in the range of a few millinewtons. An IPMC strip is activated in a beam fixed/simply-supported configuration. The beam is tightened at the simply-supported end by a force. This influences the natural resonant frequency of the beam; the value of the resonant frequency is used in the proposed system to estimate the force applied in the axial direction.The Euler-Bernoulli beam theory was used to model the behaviour of the active IPMC-based beam and hence to estimate the dependence of the beam resonant frequency on the external applied axial force. An experimental set-up was realized to investigate the predicted system behaviour. The results obtained show a very good agreement between theoretical predictions and observed behaviour. Through the experimental analysis, a sensor readout device is built using phase-locked loop principle. A PLL is adopted to force the IPMC into resonant conditions. The voltage control signal that drives the VCO in the PLL is used to estimate the oscillating frequency and hence the external axial load.