Research On The Laser Tracking Control System Based On Spherical Coordinate

Laser Tracking System(LTS), known as a new method of coordinate measurement, is firstly used in robot-performance calibration and developed in recent years. LTS is based on laser interferometer, a useful tool with the highest precision in large displacement measurement. And with the advantages of high accuracy, non-contact and dynamic measurement for large working volume, LTS is the most potential way of coordinate measurement.Based on principle of spherical coordinate, a flexible 3D coordinate measuring system using one-station laser tracking interferometer has been developed. This dissertation focuses on the study of laser tracking control system, which is one of the key parts of the LTS. The main works of this dissertation are as following:1) The measuring theory and general design of the LTS is firstly discussed, including the optical diagram of laser tracking interferometer, laser tracking mechanism, the hardware circuit and the motor selection.2) According to the real structure and optical path, an ideal mathematic model of the LTS is established, the coordinate expression of a common target point in the researching area is derived, and two error model concerning the misalignment of base points is also analyzed.3) The control project of the LTS using DSP and FPGA is designed. TMS320F2812, used as the main processor, is programmed to achieve communication with two piece of FPGA and the host computer, and also to control of servo motor.4) Using Verilog HDL, FPGA on signal acquisition board is programmed to obtain A/D signal, and FPGA on tracking control board to process grating ruler signal, generate clock and turn parallel data to serial ones.5) The tuning process of the servo drive system guarantees the basic function of the LTS. According to the real structure and optical path, the variable for motor controlling is obtained from the PSD bias signal.6) Integral-separated digital PID motor controller based on traditional reliable PID algorithm is designed. Combined with feedback grating signal, the speed and rotating direction is well controlled.