Shape memory alloys (SMA), in particular nickel–titanium alloy (or nitinol), have been used as actuators in some astronautic, aeronautic and industrial applications. The future will see more SMA application if less energy is required for actuation. This paper presents the design and experimental results of control of an SMA actuator using pulse width modulation (PWM) to reduce the energy consumption by the SMA actuator. A SMA wire test stand is used in this research. Open-loop testing of the SMA wire actuator is conducted to study the effect of the PWM parameters. Based on test results and parameter analysis of the pulse width (PW) modulator, a PW modulator is designed to modulate a proportional plus derivative (PD) controller. Experiments demonstrate that control of the SMA actuator using PWM effectively saves actuation energy while maintaining the same control accuracy as compared to continuous PD control. PWM also demonstrates robustness to external disturbances. A comparison with a pulse width pulse frequency modulator is also presented.

https://iopscience.iop.org/article/10.1088/0964-1726/12/5/007/pdf

Control of shape memory alloy actuator using pulse width modulation

In this paper, we present an artificial muscle actuator based on a dielectric elastomer called the “multistacked actuator.” The actuator is made from a new material, the synthetic elastomer, developed by the authors. The proposed actuator is configured with multiple stacked synthetic elastomer films coated with compliant electrodes on both sides. This design enables the actuator to generate rectilinear motion with high force density. In addition, the actuators can be fabricated in various geometries to meet the requirements of the applications. We develop a pulsewidth-modulated proportional-integral-derivative (PWM-PID) feedback controller based on the high-voltage switching circuit and implemented it to drive the proposed actuator. Finally, the performance of the actuator is evaluated via experiments.

Fabrication and Control of Rectilinear Artificial Muscle Actuator

A new bending mode multimorph actuator was designed and fabricated successfully by a multiple screen printing process. Unlike the conventional bimorph actuator in which the bend occurs in the thickness direction, the bend in the multimorph actuator occurs in the widthwise direction because of synchronistical deformation of each single monolithic layer in the multilayer structure. The theoretical analysis and experimental measurements were conducted to study the performance of this type of actuator, and a comparison was made with the conventional bimorph actuator. Larger displacement, higher resonance frequency, and much larger blocking force could be achieved with the multimorph actuator than with a bimorph actuator of similar dimensions. The multimorph actuator presented in this paper provides a valuable alternative for actuator applications beyond those available with the popular bimorph and longitudinal multilayer actuators.

Y. Zhao

Papers

A power air-jet actuator with piezotranslator drive stage

Optimization of a bimorph piezotranslator device for electro-pneumatic power conversion

Pulse width modulated reinforced piezo air jet actuators