A standardized SMA modular actuator enabled by ultrasonic welding technique and an integrated control system

Abstract Shape memory alloys (SMAs) are widely used in soft robotics owing to their compact structure, high power-to-weight ratio, and reversible deformation. However, most existing SMA actuators still rely on manual assembly and lack standardization, which undermines reliability and scalability. Although resistance-feedback and drive–sense approaches have been reported in the literature, many solutions are not systematically integrated into standardized actuator modules and often involve trade-offs in sensing precision, sampling rate, or manufacturability, thereby hindering high-precision control in complex environments. To bridge these gaps, we present a universal SMA actuator module–termed the enhanced smart modular structure (eSMS)–based on ultrasonic welding (USW) technology and an integrated drive–sense-control system. Using the USW technique, the module achieves high fastening force (12.58 N/wire), consistent wire length and tension, and lightweight joints, resulting in a 183% improvement in cycle life. The integrated circuit operates at low voltage (7.4 V) and high current (up to 8.4 A), and enables high-precision resistance self-sensing (error <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo>&lt;</mml:mo> <mml:mn>0.28</mml:mn> <mml:mi mathvariant="normal">%</mml:mi> </mml:mrow> </mml:math> ) at a driving frequency of 100 Hz, markedly improving real-time control. Experimental results show that, under vision-based feedback control, the eSMS module exhibits robust bidirectional motion, high positioning accuracy (error <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo>&lt;</mml:mo> <mml:mn>3.64</mml:mn> <mml:msup> <mml:mstyle scriptlevel="0"/> <mml:mrow> <mml:mo>∘</mml:mo> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> ), and rapid response. The proposed approach enhances the reliability and precision of SMA systems, shortens development cycles, and reduces manufacturing errors, offering a practical pathway toward standardized SMA actuator production with promising applications in biomimetic robotics, flexible gripping systems, and wearable devices.