A Robotic Finger With a 4-Bar Linkage-Based Compact and Continuously Variable Active Transmission

This letter presents a practical design implementation of 4-bar linkage-based compact and continuously variable active transmission (CCVAT) specifically tailored for the form factor of a robotic finger. The proposed CCVAT aims to solve the two major limitations of conventional linkage-based continuously variable transmission: increased inertia and complexities associated with miniaturization. To counter these limitations, our design incorporates a custom flexible shaft within the joint of the robotic finger, enhancing its adaptability and operational efficiency. In addition, we proposed a cascaded control architecture, combining a disturbance-observer-based low-level controller and a mid-level controller responsible for managing both the transmission ratio and flexion angle of the system. Finally, the feasibility of the prototype was evaluated by conducting several experiments.