A Humanoid Finger Joint Based on Two-way Shape Memory Alloy and Electrostatic Clutch*

A humanoid finger joint based on two-way shape memory alloy (SMA) and electrostatic clutch technology is introduced in this paper. The two-way SMA and electrostatic clutch are symmetrically arranged on both sides of the deflection module as the main actuation and locking mechanisms. An elastic pre-stretching module is connected to the end of the movable film in the electrostatic clutch, enabling the finger joint to achieve antagonistic bidirectional deflection. In addition, the design also includes a 3D-integrated printed rigid support with a hinge, ensuring stability and flexibility. The performance of each module and the entire finger joint is studied through experiments. The results show that the maximum force of the designed pre-stretching module can reach 1.7 N, with a displacement of 20 mm. The maximum adsorption friction force of the electrostatic adsorption module at 5000 V (10 Hz) is 0.54 N, and the maximum end actuation force of the two-way SMA module at 45 ℃ is 0.87 N. In addition, by precisely controlling the actuation voltage of the two-way SMA and electrostatic clutch, large-scale movement and stable locking of the finger joints can be achieved, and the designed module deflection angle can reach 8.2°. The entire design is simple and lightweight, providing an efficient and precise solution for the design of robot finger joints.