Error Compensation Strategy Of A 4-DoF Pose-Adjustment Parallel Mechanism

Aiming at developing pose-adjusting equipment for aircraft assemblage with large-scale component docking,this thesis carries out error compensation strategy of a 4 degree-of-freedom(Do F)parallel mechanism,referred to as Pa Quad,which is devided into 4 parts: inverse position and velocity mapping modeling,error modeling and verification,accuracy analysis and estimation,kinematic calibration.Details can be concluded as follow.1.Inverse position analysis and velocity mapping modeling.Based on the layout of Pa Quad,closed-loop vector method is utilized,and the inverse position model of Pa Quad is established.The velocity mapping model of Pa Quad is then formulated with the aid of screw theory.2.Error mapping modeling and verification.Resorting to screw theory,the geometric error model of Pa Quad is formulated by considering all possible geometric errors.And a novel validation method through simulation in Solid Works? software is proposed.By introducing geometric errors to the nominal vitural prototype,the formulated error model is proved to be accurate.3.Accuracy analysis and estimation.Sensitivity analysis of all geometric errors is carried out based upon sensitivity coefficient method.Assembling technology is proposed to especially pay attention to the geometric errors having greater influence on the pose accuracy of Pa Quad.Meanwhile,the values of geometric errors can be measured.On the basis of interval theory,the impact from geometric errors to the pose accuracy of physical prototype is estimated,which provides theoretical foundation for simplifying parameter identification model.4.Kinematic calibration.With the results from the accuracy estimation,error identification model of Pa Quad resorting to laser tracker measurement is formulated.Semi-practical simulation in Solid Works? software is implemented to validate the error identification model.Calibration experiments are carried out after that.It is shown from the experiment that the three maximum angular deviations decrease from 0.197°,0.522°and 2.098°to 0.027°,0.046°and 0.521 ° respectively within the prescribed workspace,which verifies the effectiveness of the proposed calibration procedure.The above-mentioned research provides theoretical and technological support for the application of Pa Quad parallel mechanism in aircraft assemblage for large-scale component docking.