Design of Closed Loop Control Circuitry for Precision Laser Tracking System

Abstract: Laser tracking detection, a systematic technology which includes optics, laser, precision mechanism, motion control and integrated electronics, is widely used in industrial and aerospace measurement because of its large scale, high accuracy and fast. The tracking performance, control accuracy, stability and response speed of the precision 2 D.O.F. servo mechanism have great impact on the performance of the whole system. Thus research on this common key technology is of great importance to laser tracking system. The research involved in this dissertation is based on the very subsystem consisted of 2 circular inductosyns, 2 DC torque motors and a 2 D.O.F. rotational platform.A high precision angular measurement circuit for inductosyn has been designed and demonstrated according to analysis of the principle and error sources. The accuracy and robustness of this part is guaranteed by precision exciting source, analog filters and EMC shielding.The hardware of the precision servo system has also been implemented with DSP and FPGA, for the need of fast response, high accuracy and the rapidness of acquisition for the tracking error signals. The hardware is featured as flexible, stable and fast response.The code of the hardware platform has been developed. The nonlinear PID control algorithm has been designed and the model of DC torque motor has been derived. The differential equations of the controller is also been derived by Bilinear Transformation.Finally, sufficient experiments and tests have been carried out to the angular measurement system, response characteristics and closed loop accuracy of the control system. Tests indicated that the angular resolutions reached to 1.76 second and 0.88 second, with±1 pulse steady ripple and±5.3 second positioning accuracy…
Key words: inductosyn; angular measurement; motion control; PID control algorithm; DC torque motor

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