Design of Multimode 2R2T Parallel Mechanism for the Position and Orientation Adjustment of the Track Platform
The annular track platform is the operation reference of the in-service operation and maintenance equipment for the hollow flange bolt inspection of the nuclear main pump.The rapid and accurate adjustment of its position and orientation is the core element to ensure the efficient detection of hollow bolt defects.The position and orientation adjustment requirements of the annular track platform are analyzed from the viewpoint of geometric tolerance and force balance.Based on the theory of position and orientation characteristic set,a novel multi-mode 2R2T redundant parallel mechanism based on coaxial and coplanar U-U configuration is synthesized.Especially,it can realize the 3R2T posture adjustment of levelness and concentricity through switching changeable modes,including planar two-axis rotation(2R)and planar motion(2T1R).The mechanism of motion mode switching is analyzed,and the motion mode switchingcan be realized through stiffening the motion pair of the branch chain and changing the position and orientation of the branch chain.The track platform is supported by SPS redundant branch chain to ensure the force balance and force operation during the mechanism position and orientation adjustment.The orderly adjustment steps of the position and orientation of the annular track platform are described.Through the desired compliant branch chain module formed by the vacuum suction cup,the branch chain motion pair and the terminal quick clamp,the mechanism branch chain can be quickly installed,switched and disassembled.
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