Nonlinear Control of a Shape Memory Alloy Actuated Manipulator

2002 ◽  
Vol 124 (4) ◽  
pp. 566-575 ◽  
Author(s):  
Mohammad H. Elahinia ◽  
Hashem Ashrafiuon
Keyword(s):  
Robust Control ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Control Algorithm ◽  
Weighted Average ◽  
Nonlinear Behavior ◽  
Variable Structure ◽  
Open Loop ◽  
Nonlinear Robust Control ◽  
Nonlinear Robust

This paper presents a nonlinear, robust control algorithm for accurate positioning of a single degree of freedom rotary manipulator actuated by Shape Memory Alloy (SMA). A model for an SMA actuated manipulator is presented. The model includes nonlinear dynamics of the manipulator, a constitutive model of Shape Memory Alloy, and electrical and heat transfer behavior of SMA wire. This model is used for open and closed loop motion simulations of the manipulator. Experiments are presented that show results similar to both closed and open loop simulation results. Due to modeling uncertainty and nonlinear behavior of the system, classic control methods such as Proportional-Integral-Derivative control are not able to present fast and accurate performance. Hence a nonlinear, robust control algorithm is presented based on Variable Structure Control. This algorithm is a control gain switching technique based on the weighted average of position and velocity feedbacks. This method has been designed through simulation and tested experimentally. Results show fast, accurate, and robust performance of the control system. Computer simulation and experimental results for different stabilization and tracking situations are also presented.

Development of a Shape Memory Alloy (SMA) Based Assistive Hand

2015 ◽  
Vol 1115 ◽  
pp. 454-457 ◽  
Author(s):  
Alala M. Ba Hamid ◽  
Mohatashem R. Makhdoomi ◽  
Tanveer Saleh ◽  
Moinul Bhuiyan
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Sensory System ◽  
Open Loop ◽  
Rehabilitation Robotics ◽  
Robotic Hand ◽  
After Effect ◽  
Conventional Structure ◽  
Force Mechanism ◽  
Gripping Force

In Malaysia, every year approximately 40000 people suffer from stroke and many of them become immobilized as an after effect. Rehabilitation robotics to assist disabled people has drawn significant attention by the researchers recently. This project also aims to contribute to this field. This paper presents a Shape Memory Alloy (SMA) actuated wearable assistive robotic hand for grasping. The proposed design is compact and sufficiently light to be used as an assistive hand. It is a joint less structure, has the potential because the human skeleton and joint replace the robot’s conventional structure. This design has been implemented on index and thumb fingers to enable grasping. Shape memory alloy springs and bias force mechanism are used for purpose of hand’s flexion and extension. This paper describes the mechatronic design of the wearable hand, experimental study of actuation unit and sensory system. Open loop experiments are conducted to understand the hand characterization and grip force provided by index finger. Current, temperature, extension and contraction of shape memory alloy springs are reported. This mechanism requires approximately 2A current for the SMA to actuate which provides maximum of 1.6N of gripping force. Conducted experiments show promising results that encourage further developments.

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