(2) The wrist of the wrist robot is located at the front end of the arm and is the part that connects the end effector (such as the claw). Structurally, the wrist must be very compact and lightweight to reduce the moment of inertia and heavy moment at the end of the manipulator; it is often made of hard aluminum alloy and often uses a separate section. The drive member (motor) is placed on the rear arm, and in terms of motion, the wrist joint can have three rotations around three mutually perpendicular axes (Fig. 1). But depending on the homework, the degree of freedom of the wrist