Design And Research Of Micro Fiber Optic Gyro Strapdown IMU

This thesis mainly introduces the study and design for the small volume strapdown Inertial Measuring Unit (IMU) using a new developed fiber optic gyro (FOG). The system is composed of 3-axis integrated FOG unit, three quartz flexible accelerometers, DSP signal processing circuit (including pulse counter from V/F transferring circuit), V/F transferring circuit itself, power amplifying electric board, electric source module and mechanical frame. The operating theory is: the three fiber coils of the 3-axis integrated FOG unit and the three quartz flexible accelerometers are fixed to a three-dimensional bracket, yielding angular velocity and linear acceleration signals, and the DSP achieves attitude, navigation and auto pilot algorithm solution, then executing order is given to fulfill the flight control by driving servo system through power amplifying circuit. Among those above, the power amplifying board, in the charge of another company, after combined debugging with the small volume inertial measuring strapdown set discussed in this thesis, will be delivered together with the latter as a whole to the headquarter for the realization of the missile’s control and guiding system.The 3-axis integrated FOG unit is made up of 3-axis integrated optic part and FOG’s signal processing circuit. The former has three sensing fiber coils fixed to a unique three-dimensional bracket, using one light source. The latter includes high-power SLD (super luminant diode) driving circuit and FPGA circuit, producing digital signal in direct ratio to the angular velocity.The output signal from the three quartz flexible accelerometers is changed into pulse by V/F transferring circuit, then into digital signal by counter in the DSP signal processing circuit, which can be accessed by DSP to process algorithm solution.The DSP signal processing circuit includes DSP digital signal processor, FPGA, UART, interface ARINC429, parallel interface module, and A/D & D/A converter and storage. FPGA achieves logic control function among the DSP periphery chips, and builds three routes V/F counter modules and frequency sample counter of Doppler Radar. Interface ARINC429 mainly carries out the communication with the aerocraft’s arm-control system. Serial interface RS422 accomplishes the output of the digital signal. Optional output modes and storage capacity are available according to the declaration of the system. Multi-channel A/D sampling function covers the binding parameters of the analogue arm-control system, the emulating signals of the gyros and accelerators, and the temperature inside the gyros and the inner integrated unit. Related software is somewhat the hardcore of the whole system, involves data sampling, system self-examine, temperature compensation around null, and serial communication. The software is written in C language, and is modular, legible, transplantable, easy for maintenance.