Variable structure control of shape memory alloy actuators

A fast, accurate and robust position controller is proposed for a planar three degree of freedom robot arm actuated by rotary Shape Memory Alloy actuators and servomotors. Servomotors are used to actuate the first link and the gripper, while the remaining two links are actuated by a combination of shape memory alloy wires and pulleys. Initially, a model of the robot arm is developed for theoretical controller development. The model combines robot kinematics and dynamics with the SMA wire heat convection, constitutive law, and phase transformation equations. The model is then used to develop several nonlinear position controllers based on the Variable Structure Control, also called sliding mode control. The controller development is of an evolutionary nature starting from a simple switching control based only on position feedback and then adding velocity and integral feedbacks, respectively. Several simulations of the proposed controllers are presented. Several experiments have been performed with a desktop prototype of the robot arm. The experimental results verify the effective and accurate performance of the controllers despite significant modeling inaccuracies and parameter uncertainties.

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Indirect Intelligent Sliding Mode Control Using Hysteretic Recurrent Neural Networks With Application to a Shape Memory Alloy Actuated Beam

Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation and Control of Adaptive Systems; Structural Health Monitoring ◽

10.1115/smasis2012-7930 ◽

2012 ◽

Author(s):

Jennifer C. Hannen ◽

Gregory D. Buckner

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

Sliding Mode ◽

Variable Structure ◽

Superior Performance ◽

Flexible Beam ◽

Single Input Single Output ◽

Structure Control ◽

Single Output ◽

Parameter Variations

This paper presents the development of an indirect intelligent sliding mode controller (IISMC) for shape memory alloy (SMA) actuators. The controller manipulates applied voltage, enabling temperature control in one or more SMA tendons, which are offset to produce bending in a flexible beam tip. Hysteresis compensation is achieved using a hysteretic recurrent neural network (HRNN), which maps the nonlinear, hysteretic relationships between SMA temperatures and bending angle. Incorporating this HRNN into a variable structure control architecture provides robustness to model uncertainties and parameter variations. Single input, single output and multivariable implementations of this control strategy are presented. Controller performance is evaluated using a flexible beam deflected by single and antagonistic SMA tendons. Experimental results demonstrate precise tracking of a variety of reference trajectories for both configurations, with superior performance compared to an optimized PI controller for each system. Additionally, the IISMC demonstrates robustness to parameter variations and disturbances.

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A shape memory alloy spring-based actuator with stiffness and position controllability

Proceedings of the Institution of Mechanical Engineers Part I Journal of Systems and Control Engineering ◽

10.1177/2041304110394570 ◽

2011 ◽

Vol 225 (7) ◽

pp. 902-917 ◽

Cited By ~ 11

Author(s):

A Hadi ◽

A Yousefi-Koma ◽

M Elahinia ◽

M M Moghaddam ◽

A Ghazavi

Keyword(s):

Boundary Layer ◽

Shape Memory Alloy ◽

Shape Memory ◽

Environmental Changes ◽

Control Method ◽

Variable Structure ◽

External Loading ◽

Positioning Accuracy ◽

Structure Control ◽

Stiffness Control

In this paper, a one-degree-of-freedom actuator that is based on shape memory alloy (SMA) springs is developed and tested. The use of SMA springs allows a larger actuation workspace and controllable stiffness than SMA wires. It is shown that the actuator demonstrates a good positioning accuracy in addition to a higher level of stiffness control. A strategy based on the variable structure control method is implemented for simultaneous displacement and stiffness control. It is shown that the actuator’s position is always kept within a boundary layer defined around the desired position while a preferred stiffness is also obtained in the actuator. Such an actuator could be used to develop flexible mechanical systems which need to adapt to environmental changes in the form of external loading variation.

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SHAPE MEMORY ALLOY ACTUATED MICRO-FLOW EFFECTORS FOR VORTEX MANIPULATION

Transactions of the Canadian Society for Mechanical Engineering ◽

10.1139/tcsme-2007-0002 ◽

2007 ◽

Vol 31 (1) ◽

pp. 19-38

Author(s):

F.C. Wong ◽

C.A. Rabbath ◽

N. Hamel ◽

D. Corriveau ◽

N. Léchevin ◽

...

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

Dynamic Performance ◽

Variable Structure ◽

Control Law ◽

Supersonic Wind Tunnel ◽

Structure Control ◽

Micro Flow ◽

Actuation Systems ◽

Force Displacement

Smart structures are seen as an enabling technology for designing innovative control actuation systems for future missiles. In this study, the feasibility of employing shape memory alloy (SMA)-actuated micro-flow effectors to control the vortex shedding behaviour that produces side forces on slender body missiles is examined. Supersonic wind tunnel tests were performed on a slender finless missile equipped with static micro-flow effectors on a conical nose to determine suitable configurations that could generate significant side forces. Shape memory alloy actuators for the flow effector were developed using numerical techniques and validated experimentally. Matching the force-displacement characteristics of the SMA actuator to the micro-flow effector force-displacement requirement was accomplished by a compliant transmission mechanism. The dynamic performance of the micro-flow effector was assured with a two-step variable structure control law. Closed-loop test results showed that the control law was capable of providing effective displacement control up to 1.0 Hz.

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Design, Modeling and Control of a New Robotic Module Actuated by Shape Memory Alloy Springs

Volume 1: Active Materials, Mechanics and Behavior; Modeling, Simulation and Control ◽

10.1115/smasis2009-1293 ◽

2009 ◽

Author(s):

Alireza Hadi ◽

Mohammad Elahinia ◽

Asadollah Ghazavi ◽

Majid M. Moghadam

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

Variable Structure ◽

Robotic Systems ◽

Modeling And Control ◽

Modular Systems ◽

Structure Control ◽

Spring Type ◽

Sma Spring ◽

And Control

Modular robotic systems provide attractive benefits in the form of re-configurable robots that can change and adapt for special tasks. Self-reconfigurable is re-configurable robot with the ability to change their framework for different missions. One way to increase robots capabilities and to achieve self-configurable robots is to develop small, powerful and dexterous modules. In this paper, a new mechanism which uses Shape Memory Alloy (SMA) spring actuators is applied to develop a robotic module. Among the proposed modular systems until now, shape memory alloys especially the spring type are rarely used as actuators. The proposed mechanism is based on antagonistic application of SMA springs which provide faster actuation response. It is shown that the module mechanism is suitable for developing modular robotic systems, such as mobile robots, snake robots, and legged robots. The design of mechanical and electrical hardware of the module in addition to the sensing and actuating system is done talented in an optimum space. The same extendable modules communicate through a common bus in order to develop a distributed system. Consequently a proper module is presented to be applied in different robotic systems. Moreover, an effective non-linear control strategy which is variable structure control is applied for controlling the position of the module. Benefits and suitability of this controller for the module different configurations is verified using simulations and experiments.

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