Robot joint module based on universal joint configuration driven by SMA wires

Abstract

Modular robots can adapt to different production needs and working conditions. However, the complexity of structures and the choice of driving modes limit the development of modularization. In this paper, a robot joint module with a universal joint configuration driven by shape memory alloy (SMA) wires is proposed, which has 2-DOFs. For lightweight, the main body of the module is made of polylactic acid materials. SMA wires are used as the actuator due to the advantages of large output displacement, high mass-to-energy ratio, and low activation voltage. Adopting antagonistically arranged SMA wires and bias springs combination method increases the recovery speed and driving angles. A locking device is creatively proposed to avoid the influence of self-biasing spring compression. The detailed kinematic model of the module is established. A proportional integral differential controller is used to precisely control module movements, and the attitude angle sensor is used as the monitoring device. Through the maximum rotation angles and trajectory tracking movement experiments, the module is tested comprehensively, and the results show that the module has good movement characteristics and control precision. In addition, analyzing the tracking performance of the module in the time domain shows that the module has a relatively fast tracking speed. This module is beneficial to the research of configurations, actuators, and controls of modular robots.