Study on the mechanism and kinematics of a hybrid robot for blowout preventer assembly

A hybrid robot is proposed in this paper, which is used for the automatic assembly of a blowout preventer to prevent the oil blowout. The hybrid robot has three components, which are waist component, parallel mechanism component and wrist component. And the parallel mechanism component is mainly in charge of the transport of the blowout preventer with high speed by actuating the end-effector. The parallel mechanism component is actually a parallelogram structure with special configuration of linkages' length. The parallelogram structure can enhance the load capacity and rigidity of the robot. And it also can enlarge the motion displacement of the end-effector. In order to establish the kinematic model of the hybrid robot by Denabit-Hartenberg (D-H) law, an equivalent mechanism with serial structure is proposed to replace the parallel mechanism based on the analysis of the law of motion of the parallel mechanism. The formulations of the joints' angles of the equivalent mechanism have been presented in this paper. And meanwhile the relationship between the drive capability of the parallel mechanism and the length of the linkage has been demonstrated, which is helpful for the designing and workspace analysis of the robot. The correctness of these analyses has been verified by the simulation of the workspace.