Development of velocity sensor using ionic polymer-metal composites

'Soft' sensing system is extremely important for advanced applications of Ionic Polymer-Metal Composite (IPMC) actuators. because conventional 'solid' sensors may be cause to cancel the flexibility of IPMC. One possible sensor would be IPMC itself. IPMC can also utilized as a sensor, because an electric potential will be generated across the composite when the strip was bent suddenly. In this paper, we investigate a relationship between the sensor output and dynamic deformations, and showed that a velocity of deformation was in proportion to a sensor output voltage. We assumed that electrical charges of each capacitor. which was defined by an electrical equivalent circuit model for IPMC. were generated proportionately to the velocity of deformation. This hypothesis was confirmed by comparison between simulations results and the experimental results. Two velocity-sensing systems were also developed. One is a 3-DOF tactile sensor that has four IPMC sensor modules combined in cross shape and can detect both a velocity and a direction of the motion of center tip. The experimental results showed the amount of the velocity and the direction of the motion could be estimated by calculating four outputs of each sensor modules. Another is a patterned IPMC strip that has both actuator and sensor functions. This strip can sense a velocity of bending motion made by the actuator part. The experimental result showed that the sensor output followed closely the velocity, of the bending motion.