A fuzzy PID-controlled SMA actuator for a two-DOF joint
Shi Zhenyun, Wang Tianmiao, Liu Da
*
, Ma Chen, Yuan Xiangnan
Robotic Laboratory, Beihang University, Beijing 100191, China
Received 7 April 2013; revised 29 April 2013; accepted 30 May 2013
Available online 28 February 2014
KEYWORDS
Fuzzy PID control;
Mechanical Joint;
Self-sensing;
Shape memory alloy;
Smart structure
Abstract Shape memory alloy (SMA) actuator is a potential advanced component for servo-
systems of aerospace vehicles and aircraft. This paper presents a joint with two degrees of freedom
(DOF) and a mobility range close to ±60 when driven by SMA triple wires. The fuzzy
proportional-integral-derivative (PID)-controlled actuator drive was designed using antagonistic
SMA triple wires, and the resistance feedback signal made a closed loop. Experiments showed that,
with the driving responding frequency increasing, the overstress became harder to be avoided at the
position under the maximum friction force. Furthermore, the hysteresis gap between the heating
and cooling paths of the strain-to-resistance curve expanded under this condition. A fuzzy logic
control was considered as a solution, and the curves of the wires were then modeled by fitting
polynomials so that the measured resistance was used directly to determine the control signal.
Accurate control was demonstrated through the step response, and the experimental results showed
that under the fuzzy PID-control program, the mean absolute error (MAE) of the rotation angle
was about 3.147. In addition, the investigation of the external interference to the system proved
the controllable maximum output.
ª 2014 Production and hosting by Elsevier Ltd. on behalf of CSAA & BUAA.
1. Introduction
Shape memory alloy (SMA) is a metal that exhibits a crystal
transition up to or below a critical temperature that causes it
alternate between the austenite phase and the martensite
phase. In the martensite phase, SMA is soft and has inelastic
straining
1
; however, in the austenite phase, the structure can
contract back to its original shape, with an elastic modulus
of roughly 100 GPa. Moreover, the maximum recoverable
strain is more than 5% of the original length, even under some
obstructions. With the growing demands for miniature
applications, SMA actuators have been used in miniature
mechanical devices due to their simple designs and high
power-to-weight ratios.
In aerospace systems, SMA actuators can be developed as
important components for future space vehicles and aircraft.
For space vehicles, SMA actuators can be applied in advanced
servo-systems, such as thrust vector adjusting systems for
satellite attitude control and manipulators of manned or
unmanned space vehicles. Recently, a prototype SMA actu-
ated locking device was developed for satellites.
2
In another
hand, SMA actuators also show their potential to be applied
in aircraft, such as servo-systems of smart aircraft to change
aerodynamic shapes
3
and controlling systems of rudders of
missiles. The Boeing Company applied for a patent which
*
Corresponding author. Tel.: +86 10 82339507.
E-mail addresses: shichong1983623@hotmail.com (Z. Shi), drliuda@
aliyun.com (D. Liu).
Peer review under responsibility of Editorial Committee of CJA.
Production and hosting by Elsevier
Chinese Journal of Aeronautics, (2014),27(2): 453–460
Chinese Society of Aeronautics and Astronautics
& Beihang University
Chinese Journal of Aeronautics
cja@buaa.edu.cn
www.sciencedirect.com
1000-9361 ª 2014 Production and hosting by Elsevier Ltd. on behalf of CSAA & BUAA.
http://dx.doi.org/10.1016/j.cja.2014.02.015