Abstract
The shape memory alloy (SMA) actuator is widely used in aerospace, medical and robot fields because of its advantages of low driving voltage, large driving force, no noise and high-power–weight ratio. Therefore, it is of great significance to establish the theoretical model of the SMA actuator and analyze the driving characteristics of the SMA actuator. On the basis of summarizing the constitutive model of the shape memory alloy spring, the phase transformation dynamics model of SMA including the minor hysteresis loop is established using the Duhem model in this paper, and the theoretical models of the bias and differential SMA spring actuator are established. At the same time, a PID position controller including anti-saturation and anti-overheating functions is proposed to control the position of the SMA actuator. Finally, the position control simulation model of the SMA spring actuator is established and simulated. Simulation results show that the position of the SMA actuator can be well controlled by using the model and control method established in this paper.
Highlights
Based on the thermodynamic constitutive model proposed by Liang and Rogers, they established the force displacement relationship of the shape memory alloy (SMA) coil spring [27]
OnOn thisthis basis, the thetheoretical models of bias differential spring actuators are established, which oretical models of bias andand differential spring actuators are established, which lays lays a foundation for theoretical the theoretical analysis of electrothermal characteristics of a foundation for the analysis of electrothermal drivedrive characteristics of SMA
For the SMA actuator, if the driving current I is given, the temperature of SMA in the heating process can be determined by Equation (23) above, and the temperature is substituted into the phase transformation kinetics model of SMA to obtain the martensite content of the SMA material at the current temperature, and the output force and displacement of the SMA spring can be calculated according to the thermodynamics model of the SMA spring
Summary
Based on the thermodynamic constitutive model proposed by Liang and Rogers, they established the force displacement relationship of the SMA coil spring [27]. In the process of practical application, SMA materials do not have complete martensite or austenite transformation in many cases At this time, the hysteresis loop formed by the relationship curve between the martensite content and temperature is called minor hysteresis loop. The Duhem model is used to establish the phase transformation dynamic model of the SMA spring under an incomplete phase transformation On this basis, according to the constitutive model of the SMA material, the theoretical models of bias and differential. The modeling process of the SMA spring actuator is introduced, including the constitutive model of the shape memory alloy, the phase transformation dynamic model, the spring thermodynamic model and the SMA spring actuator model.
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