Guohua Cui, Jian Liu, Haiqiang Zhang, and Dan Zhang
Redundant actuated, parallel manipulator, FSW robot, Jacobian matrix, kinematic, mechanical modelNomenclatureB-xyz the absolute coordinate system attached to the fixed platform of the parallel manipulator
A novel 1T2R three-degree of freedom cable-driven redundant actuated parallel manipulator, 2-SPR-UPR, is presented here, and it can be applied as the main feed manipulator of the friction stir welding (FSW) robot. The degree of freedom of the 2-SPR-UPR parallel manipulator was analysed using screw theory. Driving and constraint Jacobian matrices were established by adopting the re- ciprocal screw method. The mapping relation between the moving platform and the driving joint velocity speed was derived, and then the homogeneous dimensional Jacobian matrix was obtained. The Jacobian matrix of cable-driven was also formulated consid- ering the motion characteristics of the cable mechanism, and the complete homogeneous dimensional Jacobian matrix of redundant actuated parallel manipulator was ultimately acquired. The kine- matics dexterity and stiffness indexes were introduced. Through some numerical examples, the workspace and distribution curves of kinematic dexterity and stiffness were evaluated and the optimum region based on kinematic dexterity was demonstrated. Applying the manipulator to the FSW, the mechanical model of the cable mechanism was established, and the dynamic statics simulation of the whole machine was carried out. The results show that the redundant actuated parallel manipulator has much better dexterity and stiffness than the 2-SPR-UPR parallel manipulator, and it can be well applied to a multi-axis FSW robot.
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