2-DOF Spherical Parallel Mechanism Capable of Biaxial Swing Motion with Active Arc Sliders

Most articulated robots comprise multiple joints and links that control the position and posture of the end effector. The kinematic pair arrangement determines characteristics such as output force. The link configurations can be classified as serial link and parallel link mechanisms. A typical parallel link mechanism is the spherical parallel mechanism (SPM), designed to ensure that the end effector has only rotational degrees of freedom. However, the kinematic pair arrangement has not been sufficiently examined in two degrees of freedom (2-DOF) SPMs. Herein, we present a basic design method for the proposed 2-DOF SPM curved biaxial swing mechanism, with inputs comprising arc sliders. The swinging area of the passive link was small, and infinite rotation around a certain axis was achieved without collision or transfer to a singular posture. Using the kinematics of this mechanism, we clarified the linear roll output and non-linear pitch output. Moreover, we fabricated a prototype and measured its basic drive characteristics. The results revealed that the output performance was greatly dependent on the rotation angle, high movable range in the roll axis, and low movable range in the pitch axis.