A Portable Real-Time Test Bench for Dielectric Elastomer Actuators

Abstract

Recently, a significant amount of research has been devoted to soft robots. Artificial muscles belong to the most important components of soft robots. Dielectric elastomer actuators (DEAs) represent the technology that comes closest to the capabilities of a natural muscle, making them the best candidates for artificial muscles in robotics and prosthetics applications. To develop these applications, an analysis of DEAs in a test bench must be possible. It is important that the environmental conditions are known, and all components are specified, which is not the case in most publications. This paper focuses on the development of a real-time test bench for DEAs which provides environmental conditions and all components that are specified. Its goal is to open up the research field of dielectric elastomer actuators or soft robots. The stacked DEA used is powered by a high-voltage amplifier, which can be controlled via a real-time block diagram environment together with a data acquisition (DAQ) device. The response of the actuator is measured with a laser triangulation sensor. Furthermore, information about the applied voltage, the operating current, the temperature, and the humidity are collected. It was demonstrated that the selected laser sensor is a suitable device for this application. Moreover, it was shown that the selected high-voltage amplifier is adequate to power a DEA. However, the DAQ is not fast enough to measure the actuator current. It was demonstrated that housing keeps environmental conditions constant, is transportable, and offers the flexibility to investigate different DEAs.

Modelling and simulation of a commercially available dielectric elastomer actuator

“…On the one hand, the measurement data used for the fitting exhibits more noise. The signal has a fluctuation of 4.7 µm [61]. On the other hand, the GKV model in equation (10) assumes that the induced stress is constant.…”

“…The use of a second actuator for the creep experiments had setup-related reasons. The second actuator was permanently mounted in its test bench [61] to avoid errors arising from different actuator positions under the laser sensor during various measurements. An effort was made to keep the influence on the identification, optimisation, and subsequent validation processes as low as possible by using a second actuator of the same type and taking into account the slightly different dimensions between the two actuators (compare tables S3, S5, S9 and S10 in the supplementary materials).…”

“…Another explanation could be that the model does not consider the electrical characteristics of the DEA or the test bench. Due to the presence of a current limiting resistor [61] and its feeding line, electrode and connection resistances (combined to a series resistance), the DEA itself is a low-pass filter whose cutoff frequency is around 40 Hz, but may be even lower as the series resistance of the DEA is not known. The fact that the sine and triangle profiles give better results is probably due to the fact that the viscoelastic effects are reduced by the slower deformation speed due to the continuous slope [26].…”

“…Here, the measured deformation value corresponded directly to the change in height ∆z. The setup described in [61] was used to record the data and deformation values of the DEA are to be considered with a resolution of 0.15 µm and an accuracy of 19.4 µm. After the experiment, the data was processed with MATLAB.…”