Design Of High Precision Angle Measuring System Of Digital Close Loop Excitation Power

Inertial technology which is based on inertial device is the key technology innavigation and guidance. Inertial device mainly consists of gyroscope andaccelerometer. Turntable is the most commonly used equipment for calibration andtesting the precision of inertial device. Turntable angle measurement system is a keypart of the turntable control system, the precision of excitation power directly affects theprecision of angle measurement system. This paper mainly discussed the design schemeand the the specific circuit of the direct digital synthesizer excitation power, which isbased on the open loop excitation power supply using direct digital synthesizertechnology and the close loop analog excitation power using analog filter.First of all, the design scheme of digital close loop excitation power supply and therealization principle and hardware circuit is discussed. Compared with the open loopdirect digital synthesis excitation power supply and filtering analog excitation power, ahigh precision digital excitation power supply using high precision phase and amplitudecontrol method is put forward. This part mainly contain the analysis and selectionscheme of microprocessor of digital close loop excitation power supply, FPGAminimum system design for digital control core, DA conversion circuit design based onAD569, the derive of band-pass filter transfer function, selection of the actual circuitparameters, design of rectifying circuit and the zero crossing comparison circuit as thefeedback circuit, design of AD module which converted the analog voltage value to adigital signal, design of serial port module and FLASH memory chip to store the initialvalue of amplitude and phase of digital closed loop excitation power.Secondly, the program of digital close loop excitation power supply inside theFPGA chip is designed. This part mainly contain the design of the direct digital outputphase-detector based on high speed counter, the design of AD conversion control circuitand mean filtering algorithm, the design of ROM unit using macro function moduleprovided by QuartusII software to stores sine waves, the design of phase and amplitudeadjustment module, the design of PLL and frequency division circuit and data cacheunit.Finally, according to the function of digital close loop excitation power supplymodule, the model of controlling system is established and suitable digital controllermeeting the requirements is designed. The phase and amplitude of closed-loop systemare proportional closed-loop system model, the controller is the integral controller. Inthe closed-loop phase control system, the phase coarse and fine adjustment module isdesigned to adjust the phase. In the closed-loop amplitude control system, controllable multiplier module is designed to adjust the amplitude of the output signal. In order to setthe initial value of the phase and amplitude control system, DW8051microcontroller istransplanted into FPGA chip and the program to communicate with the upper computeris written.