An accurately controlled antagonistic shape memory alloy actuator with self-sensing

Area of Science:

• Materials Science
• Robotics
• Control Systems Engineering

Background:

• Miniaturization trends drive demand for advanced actuators.
• Shape memory alloy (SMA) actuators offer high energy density and self-sensing capabilities.
• Existing SMA actuators face challenges in precise control due to hysteresis.

Purpose of the Study:

• To design and demonstrate a self-sensing controlled actuator drive using antagonistic SMA wire pairs.
• To develop a control strategy that compensates for SMA hysteresis.
• To validate the actuator's performance through experimental testing.

Main Methods:

• Antagonistic SMA wire pairs were employed in the actuator design.
• Polynomial fitting was used to model strain-to-resistance curves, minimizing hysteresis.
• A hysteresis model of strain to duty cycle difference was implemented for compensation.
• Step response and sinusoidal tracking tests were conducted to evaluate control accuracy.

Main Results:

• The control program reduced the root-mean-square error to 1.093%.
• The system demonstrated accurate control for step and sinusoidal inputs.
• The estimated limited bandwidth of the actuator is 0.15 Hz.

Conclusions:

• The developed self-sensing actuator drive effectively compensates for SMA hysteresis.
• The combination control program achieves precise actuator control.
• The actuator design shows potential for implementation in multi-degree-of-freedom instruments.