Research On Error And Reliability Of Precision Alignment Platform For Giant Laser Device

Bottom loading LRU module of giant laser device has many characteristics,such as variety,large size,heavy weight and high requirement for cleanliness.And the installation space of LRU module is narrow and the visual range is small.How to achieve precise installation and calibration of bottom loading LRU module has become a technical problem in the world.According to the installation and calibration task of LRU module in the construction project of a giant laser device in China,a precision calibration platform with spatial six-degree-of-freedom adjustment function is designed.The precision calibration platform is composed of a 3-PSR/PSS 3-DOF redundant parallel mechanism and a 4-PRP 3-DOF redundant parallel mechanism in series.The main contents of this paper are as follows:By analyzing the institutional requirements of the Installation process of the bottom loading LRU module of the giant laser fusion device,a precision calibration platform is proposed,which is composed of a 3-PSR/PSS 3-DOF redundant parallel mechanism(horizontal adjustment unit)and a 4-PRP planar 3-DOF redundant parallel mechanism(planar adjustment unit).The structure of the platform is introduced in detail,and then,the degrees of freedom of these two functional units are calculated respectively based on the helix theory.The inverse displacement analysis model of horizontal adjustment unit is obtained by using analytic method,and the forward displacement analysis model of horizontal adjustment unit is obtained by using Newton's iteration method.For the plane adjustment unit,the forward/inverse displacement analysis model is obtained by using analytic method.Then,the position,velocity and acceleration of the two functional units are simulated by using ADAMS and MATLAB software respectively.By comparing the results,the correctness of kinematics model of mechanism is verified.Mathematical models for error analysis of horizontal adjustment unit and plane adjustment unit are established by using matrix differential method.Through the single error analysis of each error source,the main error sources affecting the terminal position and attitude errors of two functional units and the most affected motion components are found respectively.It provides a reference basis for the accuracy allocation of the mechanism in actual manufacturing.By using mechanism parameter identification method which based on least square method,the structural parameter errors of two functional units are identified,and the experimental steps are designed to verify the correctness of this recognition method.According to the identified mechanism parameter errors,the joint space compensation method is used to compensate the errors of these two functional units.The error curves before and after compensation are compared to verify the validity of the compensation method.According to the position errors of the upper and lower hinges,the length errors of the connecting rod of the horizontal adjustment unit,and the position errors of the upper slider and the rotating bearing of the Plane adjustment unit,the motion reliability models of two functional units are established by using Monte Carlo method respectively.Totally,six motion reliability values are solved.Using MATLAB software to calculate the motion reliability of mechanism in different positions and postures,and the results show that the two functional units of the precision calibration platform have very high motion reliability.The results of reliability analysis and error analysis of precision calibration platform are mutually validated.It is instructive to the accuracy allocation of mechanism in manufacturing and assembling.