Disturbance compensation-based output feedback adaptive control for shape memory alloy actuator system

Xiaoguang Li,Jianda Han,Bi Zhang,Xingang Zhao,Daohui Zhang

doi:10.1177/1729881421993998

Abstract

Shape memory alloy (SMA) has been utilized as the material of smart actuators due to the miniaturization and lightweight. However, the nonlinearity and hysteresis of SMA material seriously affect the precise control. In this article, a novel disturbance compensation-based adaptive control scheme is developed to improve the control performance of SMA actuator system. Firstly, the nominal model is constructed based on the physical process. Next, an estimator is developed to online update not only the unmeasured system states but also the total disturbance. Then, the novel adaptive controller, which is composed of the nominal control law and the compensation control law, is designed. Finally, the proposed scheme is evaluated in the SMA experimental setup. The comparison results have demonstrated that the proposed control method can track reference trajectory accurately, reject load variations and stochastic disturbances timely, and exhibit satisfactory robust stability. The proposed control scheme is system independent and has some potential in other types of SMA-actuated systems.

Highlights

Shape memory alloy (SMA) is an active material that can recover to its original shape and size when the temperature applied exceeds the certain threshold values
This article proposed a disturbance compensation-based output feedback adaptive controller (DC-OFAC) scheme to accomplish the precise control of SMA actuator system
Austenite start temperature (As) nominal model (NM)-based state estimation technique is developed to achieve the estimation of unmeasured states and the total disturbance

Summary

Introduction

Shape memory alloy (SMA) is an active material that can recover to its original shape and size when the temperature applied exceeds the certain threshold values. According to the variable sublayer model,[12] when SMA is completely in the austenite phase, the relationship can be described as sA 1⁄4 EA Á e ð6Þ where sA is the stress, EA is the austenite Young’s modulus, and e is the strain of the alloy. We will turn to an estimator to estimate the unmeasured states and the total disturbance of SMA actuator system in this subsection. The actual control law u can be constructed as follows u 1⁄4 unm þ udcc unm 1⁄4 1=gsð^x1Þða_ a À c3ðz[3] À ~x3ÞÞ ð32Þ udcc 1⁄4 À^x4=gsð^x1Þ where unm is designed to deal with the inherent nonlinear dynamic characteristics of the system, and udcc is designed to cope with the total disturbance, and guarantee the robust stability. It is concluded that all the signals in the closedloop system are convergent, and the controlled system is stable under reasonable conditions

Experimental results

À RMSENMSE

À JeDCÀOFAC

Conclusion