Implementations and Controls of a 3-DOF Parallel Link Joint Module

In this paper, a parallel link joint module (PLJM) is developed to achieve three degree-of-freedom (DOF) joint motions with respect to a fixed center of rotation. The proposed 3-DOF spatial PLJM is configured with three linear screw actuators, a base platform, a movable platform, a central bar, and seven ball joints. Due to similar motion characteristics, the PLJM can be used to construct 3-DOF joints of humanoid robots such as hip, ankle, and shoulder joints. Meanwhile, the motions of neck, waist, and wrists can be also constructed using the PLJM. In addition to parallel kinematics mechanism features, the linear screw actuator based PLJM also provides power saving benefits. That is, the PLJM only consumes energy when the PLJM works. As a consequence, humanoid robots constructed using the PLJM may provide longer service time when compared to rotary based joints. Structurally, a PLJM is desired as the connection of a 3-DOF joint and a follower limb; therefore, the PLJM may simplify the mechanical structure of humanoid robots. In addition to the PLJM design, the kinematics, trajectory controls, and interactive sensor integrations are implemented in this paper. Several interesting experiments are demonstrated to verify our approaches.