Design Of Passive Laser Tracker And Measurement Of Location Errors Between 2d Rotary Stage Axes

Laser tracker has become the main method of detecting motion accuracy of high-end equipment such as industrial robots and CNC machine tools.However,at present,laser tracker is too expensive to adapt to the development of Chinese industry.Therefore,it is necessary to develop an instrument for measuring spatial position and motion accuracy which has a relatively simple principle and can still meet the requirements of manufacturing equipment.At the same time,the 2D rotary stage is one of the main moving parts of the laser tracker,which is widely used in the field of mechanical manufacturing and measurement.In addition to the inherent errors of each rotary axis,the location errors between the two axes are important factors limiting the precision of the 2D rotary stage.The existing methods for measuring location errors of rotary axes usually use many parameters and complex mathematical models of which the test processes are complex and influenced easily by many factors.In this paper,a passive laser tracker is developed,which consists of a 2D rotary stage,a telescopic mechanism and a laser interferometer.The passive laser tracker is connected to the measured equipment by a magnetic traction device,and the measured equipment drives the tracker to move synchronously,so as to realize the real-time measurement of space position and reduce the development cost of laser tracker.The mathematical model of 2D rotary stage with inter-axis location errors is established by using multi-body system theory,and the specific effects of verticality and intersection errors on the pointing accuracy of the rotary stage are analyzed.Based on the principle of two-face system test,a method for measuring the intersection error of a 2D rotary stage is proposed,and the two-mirror method is used to measure the verticality error.Furthermore,in order to measure the errors between axes of 2D rotary stage more conveniently and accurately,a new method for measuring verticality and intersection errors of rotary axes based on laser is proposed.A laser diode is assembled on the end of the 2D rotary stage’s pitch axis,and a PSD is used to test trajectories of laser spots.The relative location errors between the two axes are separated by comparing the center coordinates of the two trajectories when the azimuth axis is located at two different positions.Two kinds of measurement methods are used to test the location errors between the two axes of the 2D rotary stage,and the test differences of intersection error and verticality error are less than 4 μm and 1 arcsec respectively.