Self-sensing Behavior of IPMCs

Changes in the impedance of an IPMC may be used to create a self-sensing actuating device [Park et al. (2008)]. An advantage of such a device is that the deformation estimation is an intrinsic property of the actuator, i.e. there is no need to equip separate senors as it can function as a coexisting sensor. The capacitance and the resistance of an IPMC are caused by structural featmes of the Pt electrode particles, such as the space between each particle and the density of the particles. The internal electrical characteristics of the IPMC, especially the resistance and capacitance of the electrodes, are changed with the mechanical deformation of the IPMC. When an IPMC is bent, one electrode surface becomes concave (+), and the other convex (-). 

22 Experimental results on feedback bending control with force monitoring (a) Estimated tip displacement based on the integrated PVDF bending sensor alone (b) output of the PVDF force sensor (c) estimated tip displacement based on both integrated sensors, in comparison with the laser sensor measurement. Reprinted from [Chen et al. (2008)1 with permission from Elsevier, Copyright 2008. 

Therefore a difference in the resistivity of both electrodes due to expansion and contraction can be observed. This mechanical deformation can change the total impedance of the IPMC during bending, and if the change is detectable, the deformation of the IPMC can be easily calculated. 

As discussed before, in case of a conventional Pt IPMC, during bending, the convex electrode resistivity increases at the same time, the concave electrode resistivity decreases, but not that significantly. At the same time, it has been reported that the same thing does not necessarily hold true for Cu-Pt electrodes. Resistance measurements have showed that copper-coated membranes display an opposite phenomenon compared with the platinum-coated materials. When actuated by appl3ung a voltage, the re- 

In this chapter, we extend and apply the results on EAP materials and models to a few device and robotic applications. A robotic fish propelled by an IPMC caudal fin is first considered in Section 9.1. The use of IPMC for low-frequency energy harvesters is studied in Section 9.2. The design of an IPMC-enabled valveless pump is discussed in Section 9.3. We then present a novel micropump actuated by conjugated polymer petals, supported by both analytical and experimental results. Finally, in Section 9.5 we investigate the design, prototyping, and control of a robotic finger powered by dielectric elastomer actuators. 

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