Modular Actuator for Multimodal Proprioceptive and Kinesthetic Feedback of Robotic Hands

This study addresses the challenge of implementing proprioceptive and kinesthetic (PK) feedback in robotic hands, essential for grasping and manipulation tasks in unstructured environments. We developed a compact modular actuator featuring a low-module, high-transmission-ratio multistage gear mechanism that measures 25 × 10 × 24 mm, weighs only 10 grams, and maintains moderate backdrivability. The actuator provides multimodal PK feedback, capturing position, velocity, current, and torque data, which are critical for performing various grasping and manipulation tasks. To enable precise motion and force control, we introduced a new adaptive velocity estimator and a simplified Reaction Torque Observer (RTOB). Comprehensive experiments demonstrated the actuator's ability to accurately detect surface shape, roughness, and stiffness of target objects, eliminating the need for additional sensors or space. Experimental results confirmed the actuator's precision, achieving measurement errors of 5.8 mrad for position, 0.19 rad/s for velocity, and 0.011 N·m for torque. These findings highlight the actuator's ability to leverage proprioceptive information, significantly enhancing the functionality and adaptability of robotic hands in diverse and dynamic scenarios.