Electrothermal Twisted and Coiled Polymer Artificial Muscles and Their Applications in Soft Robotics

Electrothermal polymer artificial muscles are increasingly popular in soft robotics due to their high load‐to‐weight ratio and cost‐effectiveness. However, current control strategies for these actuators mostly rely on traditional proportional integral derivative (PID) control or single‐dimensional closed‐loop control. These methods can mitigate the adverse effects of the inherent hysteresis, nonlinearity, and temperature–force angle coupling of these actuators somewhat, but fail to effectively meet the precision requirements of specialized applications. To address these challenges, a temperature self‐sensing‐driven hierarchical closed‐loop fractional‐order proportional integral derivative (FOPID) control scheme is designed. It leverages nickel wire's resistance‐temperature characteristics for real‐time temperature self‐sensing, eliminating the need for external sensors; its hierarchical structure prioritizes temperature control followed by angle regulation to mitigate coupling effects; and the FOPID controller outperforms traditional PID with smaller overshoot and faster convergence to manage nonlinearity. Based on this control scheme, an artificial muscle is fabricated using polyethylene and silver‐plated nylon (PE@SPN). To enhance deformation and output force, single PE@SPN fibers are combined in series–parallel to form composite artificial muscles. A rehabilitation manipulator is developed based on these composite artificial muscles, with a closed‐loop control algorithm implemented via temperature self‐sensing and FOPID as the core control strategy, demonstrating the engineering application value of PE@SPN artificial muscles.