Kinematic Modeling And Calibration Method Of Satellite Attitude Simulator

Satellites are often needed in precision industries such as aerospace,maritime transportation,and navigation to accomplish various tasks,where the terminal attitude accuracy of satellites is crucial to the performance of satellites.The construction of the kinematic model of the satellite attitude simulator and the high-precision calibration of the parameters are the key ways to improve the attitude accuracy of the satellite attitude simulator.This paper focuses on the following aspects of related research:(1)Construction of forward and reverse kinematic models.The satellite attitude simulator adopts a six-degree-of-freedom orthogonal plus three-tandem mechanism.In order to obtain the high-precision real-time end attitude of this mechanism,this paper adopts the D-H modeling method to build the coordinate system of each motion branch based on the initial coordinate system,and derive the attitude conversion relationship from the initial coordinate system to the end coordinate system,so as to establish the forward kinematic model and reveal the motion law of this mechanism;meanwhile,the algebraic method is used to solve each initial variable in the inverse direction to determine the inverse kinematic model.The verification of the forward and inverse kinematic models is also completed by comparing the 3D models.This method is applicable to the acquisition of the end position of the simulator and the inverse solution of the initial state.(2)Kinematic error analysis and calibration model building.The main error sources are analyzed in detail,i.e.,external errors and errors in kinematic geometric parameters.Based on the mechanical structure and kinematic model of the motion mechanism,the main error sources are identified and the 12 main parameters affecting the calibration results are analyzed.The control variable method is used to analyze the degree of influence of the error sources on the accuracy of the final end position parameters when only one transformation quantity is constantly changing.Further,the single-point-based calibration model and the distance-based calibration model are established respectively according to the error analysis to reduce the loss of accuracy of calibration results caused by too many parameters.(3)Research on the calibration method of kinematic geometric parameters.Two calibration schemes are proposed to address the accuracy of parameter calibration:a single-point calibration model combined with a uniformly selected 60 sets of spatial positional data,and a simulation using the L-M algorithm to verify that the accuracy of the spatial X,Y and Z coordinate values is better than 10 μm,which significantly improves the parameter calibration accuracy.In addition,a statistical Monte Carlo algorithm is used to further verify the correctness and feasibility of the scheme;the calibration method based on the distance calibration model combined with the errorsensitive direction-based selection of 60 sets of spatial positional data is validated by the L-M algorithm,and the results show that the accuracy of the spatial X,Y and Z coordinate values is better than 7.7 μm.The calibration results are compared with those of the previous scheme,and the comparison results show that this scheme is further effective in improving the parameter calibration accuracy,indicating that this calibration scheme is suitable for the calibration study of satellite attitude simulator parameters.(4)Experimental calibration of kinematic geometry parameters and analysis of the results.Based on the feasibility of the calibration scheme at the theoretical level,the Leica laser tracker is used as an external high-precision attitude measurement instrument to complete the experimental verification of the scheme.During the experiments,the tracker follows the simulator’s motion in real time and dynamically measures its end-position information,which is then brought into the proposed calibration scheme and analyzed.The results show that the calibration results are better than 13 μm in spatial X,Y and Z directions due to the influence of the environment and temperature of the experimental site,and the experimental error is larger than the theoretical one,but the overall error is within a reasonable and effective range,which meets the calibration requirements.