Thermal characteristic modeling and validation of giant magnetostrictive actuator based on dual-flow-channel cooling structure

Giant magnetostrictive actuators (GMAs) usually have the problem of significant temperature change caused by power losses under pulse width modulation (PWM) excitation. It leads to thermal deformation and a decrease in the magnetostriction coefficient, which degrades their performance of position control. This paper introduces a novel dual-flow-channel (DFC) cooling structure that includes outer and inner flow channels. Flow grooves are machined into the magnetic sleeve to form the outer flow channel in conjunction with the shell, while the inner flow channel immerses the giant magnetostrictive material (GMM) rod. DFC cooling structure achieves efficient heat dissipation for GMA while preserving its original volume and maintaining good sealing. A thermal analytical model of GMA, based on the lumped-parameter thermal network (LPTN), is employed to achieve rapid and accurate prediction of thermal characteristics. Based on the Jordan loss model, the GMM loss model under sinusoidal excitation was improved to develop a GMM loss model under PWM excitation. A prototype of GMA was designed and machined, and its thermal characteristics were tested. The experimental results show that, under ambient conditions of 20 °C, with a current amplitude of 5 A, a PWM frequency of 50 Hz, and a coolant flow rate of 0.5 L/min, the final temperature of the GMA with the DFC cooling structure decreased from 45 °C to 23.5 °CC. The relative errors between the analytical and experimental results were <11% under different conditions, validating the accuracy of the proposed analytical model. This study provides important theoretical support for the investigation of thermal deformation in GMAs under PWM excitation.