On Position And Orientation Measurement Technics Of FAST’s Feed Cabin By Laser Tracker

FAST is the abbreviation of Five hundred meters Aperture Spherical radio Telescope,which is so far the largest single caliber radio telescope in the world.Feed cabin is one of the core components of radio telescope and is also the installation platform of payloads such as feed receivers.Feed cabin is a system related to structure,measurement,control and other related technologies and integrated of optical,mechanical and electronic functions.Due to the huge space span,it is difficult to establish a high-precision rigid connection between the receiver and the reflector,which makes it difficult to achieve high-precision positioning and tracking of the feed.Centered on the position and orientation measurement of the FAST Feed cabin,the large size coaxial measurement method of the cabin,the calibration of Stewart Mechanism,methods of position and orientation measurement of the calibration and other key theories and technologies are studied in this paper.The main work and innovation points of this paper are as follows:1.The method of measuring large coaxiality with a laser tracker at the construction site is proposed.Based on the coaxiality measurement of the FAST feedbox star frame,by using the laser tracker,the measurement of coaxial axial deviation is transformed into the measurement of the angle between the datum axis and the normal of end surface.The measuring process and results show that this method possesses simplicity and good accuracy,the angle between the datum axis and the normal of end face is 0.094° which is superior to the design demand 0.2°.2.A calibration method of Stewart Mechanism is proposed by analyzing its structure performance and parameter model.To realize the accurate positioning of the feed cabin,it is needed to overcome the processing and the assembly error,the measurement error,the rigidity deformation and the external disturbance coupling influence.By analyzing the structure,performance,parameter model and simulation of Stewart,the calibration method is determined.By analyzing the boundary conditions and simulation conditions in Simulink model,the ADAMS model is used to simulate the dynamics of the feed cabin,the Simulink model is used to simulate the control system of the feed cabin and finally the ADAMS-Simulink joint simulation is realized.At last,the laser tracker measurement system is employed to measure,process data and analyze error,and the precision calibration of the Stewart institutions is realized.3.Three methods of Stewart attitude measurement are designed.A single laser tracker measurement method,digital industrial photogrammetry method and three laser tracker combination measurement method are studied.By analyzing three kinds of measurement system principle,measurement process,pose solution and so on,compare three kinds of pose Advantages and disadvantages of the measurement method: a single laser tracker measurement method easy to use,digital industrial photogrammetry method set flexible,three laser tracker joint measurement method is high efficiency.