Ionic electroactive polymers (IEAPs), particularly ionic polymer-metal composites (IPMCs) and carbon-polymer composites (CPCs), bend when a voltage is applied on their electrodes, and conversely, they generate an electrical signal when subjected to a mechanical bending. In this work we study and compare the capabilities of IPMC and CPC actuators and sensors in closedloop control applications. We propose and realize an integrated IEAP sensor-actuator design, characterize its performance using three different materials, and compare the results. The design consists of two short IEAP actuators and one sensor mechanically coupled together in a parallel configuration, and an attached rigid extension significantly longer than the IEAPs. This allows the device to be compliant, simple to construct, lightweight, easy to miniaturize, and functionally similar to a one-degree-of-freedom rotational joint. For control design and accurate position sensing in feedback experiments, we adapt physics-based and control-oriented models of actuation and sensing dynamics, and perform experiments to identify their parameters. In performance characterization, both model-based ¥ H control and proportional-integral control are explored. System responses to step inputs, sinusoids, and random references are measured, and long-duration sinusoidal tracking experiments are performed. The results show that, while IEAP position sensing is stable for only a limited time-span, H ∞ control significantly improves the performance of the device.

Active sensing methods of ionic polymer metal composite (IPMC) Abstract-Ionic polymer-metal composites (IPMCs) are soft transducers that bend in response to low-voltage input, and generate voltage in response to deformations. Their potential applications include compliant locomotion systems, small-scale robotics, energy harvesting and biomedical instrumentation. The materials are inherently compliant, simple to shape, simple to miniaturize and simple to integrate into a system. Compared to actuation, IPMC sensing has not been intensively studied. The existing reports focus on the sensing phenomenon, but provide insufficient characterization for implementation purposes. This work aims to address this gap by studying and comparing the frequency responses and noise dynamics of different IPMC active sensing signals, i.e. voltage, charge and current. These characteristics are experimentally identified by mechanically exciting IPMC samples, and simultaneously measuring the respective signals and material deformations. The results provide a systematic comparison between different implementations of active sensing with IPMCs, and give insights into their strengths and limitations.

Ionic polymer–metal composites (IPMC) are smart material transducers that bend in response to low-voltage stimuli and generate voltage in response to bending. IPMCs are mechanically compliant, simple in construction, and easy to cut into desired shape. This allows the designing of novel sensing and actuation systems, e.g., for soft and bio-inspired robotics. IPMC sensing can be implemented in multiple ways, resulting in significantly different sensing characteristics. This paper will review the methods and research efforts to use IPMCs as deformation sensors. We will address efforts to model the IPMC sensing phenomenon, and implementation and characteristics of different IPMC sensing methods. Proposed sensing methods are divided into active sensing, passive sensing, and self-sensing actuation (SSA), whereas the active sensing methods measure one of IPMC-generated voltage, charge, or current; passive methods measure variations in IPMC impedances, or use it in capacitive sensor element circuit, and SSA methods implement simultaneous sensing and actuation on the same IPMC sample. Frequency ranges for reliable sensing vary among the methods, and no single method has been demonstrated to be effective for sensing in the full spectrum of IPMC actuation capabilities, i.e., from DC to ∼100 Hz. However, this limitation can be overcome by combining several sensing methods.

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An ionic polymer-metal composite (IPMC) is an electroactive material that bends when electrically stimulated and generates electric current when bent. In this paper we investigate a coupled IPMC sensor-actuator using both the sensing and actuation properties of these electroactive materials. We describe the design of a coupled IPMC sensor-actuator, the feedback controller and the experimental evaluation of the system. Experimental results show the feasibility of closed-loop control of IPMC actuator with a mechanically coupled IPMC sensor.