Design And Implementation On A High-precision Scanning Control System

The microwave radiometer is the core of the meteorological satellite. To get highquality images from meteorological satellites and realize accurate observation on ground or atmospheric, it is indispensable to design a high-precision scanning control system. The scanning and drive control technology of microwave radiometers is a focus in this paper. Its primary mission is to design a platform of scanning control systems based on permanent magnet synchronous motor, and ensure that the platform rotates steadily. The selection of hardware is according to models of the design organization. The working condition of the developed control system is close to real situation in space. High-precision speed control of the big inertia rotor is put into use in the article, which is for a specific range. A double closed-loop control strategy of current and speed is adopted.A new design method of the scanning control system is put forward based on a Freescale microcontroller. With the PMSM as servo driven mechanism, the resolver as position measuring element, and Hall element as detecting element of the cycle, highprecision control of a high inertia rotor is implemented.At first, the development and current situation of the scanning control system is introduced about microwave radiometers, then the overall design scheme is proposed,including the hardware selection of the system.Secondly, the system model is established, and the performance of the system is analyzed, then the test whether the system performance meets the system design index or not in theory is accomplished. Due to adopt a double closed-loop control strategy of current and speed, It is necessary to design the parameters of the PID controllers of the double closed-loop. Then the simulation of the system is accomplished in the software Matlab. The simulation verifies the feasibility of the scanning control scheme, and the steady speed precision of the rotor meets the design index.Again, the hardware and software design of the scanning control system is done. The method of sine wave half-bridge drive is used to drive PMSM. The way of the long period sampling and big rotor inertia to restrain the disturbance,which is caused by shaft friction and motor torque fluctuation,is applied. In the aspect of hardware design, the drive and control circuit based on Freescale MC56F8027 MCU has been done, and 21 high-precision resolving of the angle position is used, with double AD2S80 A chips as the calculation of rotating transformers. In the aspect of hardware design, the CW10.4 compiler is applied to compile and debug software program. The program of current sampling, the angular position detection, sine wave control, RS485 communication and PID control is compiled in assembly and C language.Finally, A PC interface is designed in C+ + Builder studio. Then the speed test of the ground turntable is done. The results of experiment show that the system design scheme is feasible and meet design indexes.