Research On Key Techniques In Multi-Sensor High Precision Measurement Based On CMM

As the development of society and the growth in living standard,especially in aerospace,precise manufacturing and dissemination of the value of quantity,demands in precision and efficiency of measuring workpieces increase,which brings up a new challenge for measuring techniques.How to get the coordinates from complex geometries more accurate is always the goal of researchers.When measuring an object with only one sensor,the precision of results and the efficiency could not meet the requirement any more,however,measuring systems with multiple sensors could obtain the information of measured objects more accurate,more efficient and more holistic.If a multi-sensor measuring system is chosen,it is critical to process the data and to fuse the data.Here,the paper is regarding to studies on a multi-sensor integrated measuring system with a video camera,a tactile probe and a confocal sensor.The paper includes:1.Calibrations of all sensors in the integrated coordinate measuring system.A five-point method is adopted to calibrate the tactile probe.A new high precision calibration board with circle arrays is designed and manufactured,which is utilized to calibrate the video camera.And an angle gauge method is proposed to obtain the squareness error between the optical axis of the confocal sensor and the xy stage of the machine,but it is influenced by many factors such as the angles of the angle gauge on the working stage.In order to avoid these factors,a modified one is present,which will be easier to calibrate the confocal sensor.2.As the registration of sensors is realized by using intersection points of several geometry features,sample strategies for the determination of the equations of the features is analyzed with a definite function,and the errors of intersection points are explained with definite functions as well,then the parameters that affect the accuracy of intersection points will be clearly known.3.Standards with these feature of intersection points being applied to registering the multiple sensors,based on the results of the registration,a composite standard is designed,which consist of a cone and a cylinder with a coaxial symmetry axis,also a corresponding measuring method is present.By comparing all the results,some problems are found,which will give a suggestion to a new method of registration.4.Considering the defects in multi-sensor registrations by using standards of intersection points,a multi-step method is proposed to fuse multiple sensor in the integrated coordinate measuring system.This method has abandon the concept of intersection points in registration of multiple sensors,it is realized by different sensors measuring different features between who a constant distance exists.By using this method,the error in the registration of multiple sensors by a sphere is calibrated as well.And a verification of the suquareness of the x-axis and y-axis of the machine based on the multi-step method is conducted.