Research On The Influence Of Mobile Platform Error On The Accuracy Of Linear Laser 3D Measurement

In recent years,the requirements for online dimensional measurement accuracy in automated production have continuously improved.As a 3D visual measurement technology widely used in practical production,line laser 3D measurement has become an important issue that needs to be resolved urgently to effectively improve the accuracy of line laser 3D measurement systems.The accuracy of line laser 3D measurement not only depends on the accuracy of the line laser 3D camera itself,but also is closely related to the mobile platform error of the line laser 3D measurement system.Therefore,the following research work has been carried out to explore the impact of mobile platform errors on the accuracy of line laser 3D measurement.In this thesis,21 geometric errors of a typical three axis mobile platform are determined by analyzing the geometric error parameters of the platform.According to the modeling process of multibody system theory,this thesis establishes the topological structure of a three-axis mobile platform,sets each coordinate system of the three-axis mobile platform according to its topological structure,and then uses the homogeneous coordinate transformation method to derive the coordinate transformation matrix between each coordinate system.Finally,a comprehensive geometric error model of the three-axis mobile platform is established.By comparing the geometric error measurement methods of different three axis mobile platforms,this thesis proposes to use the nine line measurement method to measure and calculate the geometric error of the three axis mobile platform.However,the traditional nine line measurement method has two shortcomings: ignoring the angular deviation caused by the misalignment of the coordinate axes of the measurement coordinate system and the platform coordinate system,as well as the accumulation of errors during the identification and calculation process,Therefore,this thesis will use the least square method to preprocess the straightness error data and add measurement items to optimize the identification matrix.The simulation results show that the improved method has higher identification accuracy and better stability of the calculation results.According to the laser triangulation measurement principle of 3D cameras,this thesis obtains a mathematical model of the impact of 3D camera’s single degree of freedom pose error on the measurement results by analyzing the impact of each degree of freedom pose error on the measurement results separately.Then,combined with the mathematical model of the impact of each single degree of freedom error,a mathematical model of the comprehensive impact of 3D camera’s six degrees of freedom pose error on its final measurement results is established.Finally,this thesis designed two sets of experiments.The first set of experiments verified the effectiveness of the three-axis mobile platform error model by comparing the mobile platform error data before and after compensation using the three-axis mobile platform error model;The second group of experiments verified the effectiveness of the 3D camera measurement error model by comparing the camera measurement error data before and after compensation using the 3D camera measurement error model.