Design and Evaluation of a Series Elastic Actuator Based on Parallel Springs

This paper proposes a Series Elastic Actuator aimed at reducing the impact forces on joints during specific movements to prevent damage to the mechanical structure from excessive external forces during machine operation. The SEA uses a planar structure with input and output terminals coupled through a spring, featuring a compact axial design. The output torque is modeled based on the actuator's dynamics to determine the torque-deflection relationship. The accuracy of the torque estimation model is studied by comparing the estimated torque with the torque measured by a torque sensor. The model's estimated RMSE value is 0.3302 Nm, the maximum error is 0.9837 Nm, and the standard deviation is 0.1990 Nm. The results indicate that the model can effectively estimate the output torque of the proposed SEA. Additionally, the actuator's open-loop frequency response was tested to study its response to input signals of different frequencies. The open-loop amplitude response and phase response graphs of the system were plotted, showing that the system's amplitude attenuated to -3 dB at an input signal frequency of 1.67 Hz, and the reasons for this phenomenon were analyzed.