Manipulator Equipped With Differential Wrist Mechanism to Combine the Torque of Two Motors to Increase Fingertip Force and Wrist Torque

A lightweight and high-output manipulator is introduced in this letter. The manipulator comprises two parts: a robot hand part and a wrist part. The total weight of the robot hand part is approximately 450 g, and its size is almost the same as that of a human hand. Furthermore, a design concept of a differential mechanism is presented in this letter. In contrast to traditional mechanisms, in which the movement of a single motor corresponds to a single module, the proposed differential mechanism can superimpose the output forces of multiple motors and act on the movement of single or multiple modules; consequently, the output force is doubled, the low-power requirement of the motor, which drives the robot hand as the end effector to rotate around the wrist, is met, and the driving force amplification mechanism amplifies the gripping force of the fingers. The proposed differential mechanism is incorporated in the wrist part. The robot hand part is responsible for the fast grasping of objects. The wrist part is responsible for increasing the output force of the fingers to ensure a firm grasp. In addition, it enables the robot hand to rotate around the wrist. It takes 0.32 s for the fingers to transition from moving to touching the object. It takes approximately 0.9 s to grasp the object firmly, and the output force of the fingertips can reach 25.5 N. The robot hand can rotate 135$^\circ$ around the wrist, and the rotation speed is 118 deg/s.