Electro-Mechanical Analysis of a DEAP Actuator Coupled to a Negative-Rate Bias Spring Mechanism

This paper presents the design and analysis of a Negative-rate Bias Spring (NBS) paired with a Dielectric Electro-Active Polymer (DEAP). A NBS is a bi-stable mechanism with a negative slope region between its two stable configurations. The objective of this work is to demonstrate the increased stroke output of a DEAP actuator when biased by such a bistable mechanism. Possible devices that could use this actuation technology are lightweight, miniature pumps and valves. First, the NBS is mechanically tested and its bi-stable behavior is observed along with the negative slope region between the stable configurations. Then the NBS is coupled with a circular DEAP actuator (to provide the bias force) and is experimentally tested under a variety of loading conditions with a focus on the force and stroke capabilities. The stroke output of the device was approximately 1mm for a range of electrical loading rates (0.1Hz, 1Hz, and 10Hz). The measured force and stroke are then correlated to the force vs. displacement data observed during the mechanical characterization experiments. Additionally, the force vs. displacement behavior of the NBS-DEAP is analytically modeled and showed good comparison with the results.