Highly integrated spherical wrist with decoupled three degrees of freedom

To improve integration and flexibility of space robot wrist, a 3-DOF decoupled spherical wrist with independent kinematic chains was proposed. The structure of double universal joints and double hemispheres was employed to guarantee compactness and flexibility of the spherical wrist. The transmission relationship of three motions and the workspace of the wrist were analyzed, the structure design of the 3-DOF decoupled spherical wrist was finished, the forward and inverse kinematics and Jacobian matrix of the spherical wrist were derived, the characteristics of motion decoupling and structure decoupling were investigated, and the motion transitive relation between the working space and the joint space was established. The experimental platform of the 3-DOF decoupled spherical wrist was established, the posture motion experiments of pitch, yaw and rotation were conducted, along with the verification experiment of motion trajectory of the wrist end. The study results show that the decoupled motions of the 3-DOF spherical wrist are flexible and smooth, posture angles can be adjusted in large range, and accurate trajectory tracking can be realized.