Position Control of the Dielectric Elastomer Actuator Based on Fractional Derivatives in Modelling and Control

Timi Karner,Janez Gotlih

doi:10.3390/act10010018

Abstract

Successful control of a dielectric elastomer actuator (DEA) can be a challenging task, especially if no overshoot is desired. The work presents the first use of the PIλDμ control for a dielectric elastomer actuator to eliminate the overshoot. The mathematical model of the dielectric elastomer was established using the fractional Kelvin-Voigt model. Step responses are first tested in the Laplace domain, which gave the most satisfactory results. However, they did not represent the real model. It cannot have negative force acting on the dielectric elastomer actuator. Simulations in Matlab/Simulink were performed to obtain more realistic responses, where output of the PIλDμ controller was limited. Initial parameters for a PID control were obtained by the Wang–Juang–Chan algorithm for the first order plus death time function approximation to the step response of the model, and reused as the basis for the PIλDμ actuator control. A quasi-anti-windup method was introduced to the final control algorithm. Step responses of the PID and the PIλDμ in different domains were verified by simulation and validated by experiments. Experiments proved that the fractional calculus PIλDμ step responses exceeded performance of the basic PID controller for DEA in terms of response time, settling time, and overshoot elimination.

Highlights

Soft actuators are actuators whose performance tries to mimic the behavior of a biological muscle
5.5 times and was nearly domain can handle fractional orders since derivative is translated into multiplication place domain can handle fractional orders since derivative is translated into multiinated in comparison to its PID counterpart, as can be seen in Table
The main objective was to eliminate the overshoot and make the response as fast as possible for the dielectric elastomer actuator (DEA), which was modeled as fractional plant

Summary

Introduction

Soft actuators are actuators whose performance tries to mimic the behavior of a biological muscle. A biological muscle performs only two simple motions: contraction and relaxation. Even though this movement seems very simple, the reality is quite the opposite. Muscle fibers are a compound of myofibrils, of which the basics are sarcomeres. A sarcomere has two parts: myosin filaments and actin filaments. They interact with each other with the help of Ca2+ ions. The presence of Ca2+ ions contracts the muscle fiber by δL, whereby the duration of the contraction depends on the amount of these ions [1]. If A is measured over time, one can obtain power P = F · δL/δt generated by the contraction of a muscle

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Conclusion