Design Of Accelerometer All Digital Force Feedback Loop

Accelerometer is used widely in the field of astronavigation, aviation and voyage for it is one of the main inertial components for inertial navigation system, as it will effect the whole system badly, the demand for its performance state is higher and higher. High-accuracy pendulum accelerometer should form a closed loop measure system with the force feedback loop, while the nature of the force feedback loop will influence the output of the accelerometer importantly. So there are important significations to do research on the accelerometer force feedback loop to improve the accelerometer output precision and the system stability. All-digital, high-density and miniaturized will be the develop direction for the force feedback loop as the quick development for new technique in different fields. This paper does some research on the Fluid Pendulous Accelerometer (FPA) force feedback loop base on the engineering practice.The development history and present status of the accelerometer and its force feedback loop is described firstly, then the operating principle of the FPA and the force feedback loop applied moment way are analyzed in detail, the binary width impulse force feedback loop is confirmed as the design scheme. The digital controller is designed on the base of the design and the simulation for the control system.On the realization of the hardware circuit, ARM microprocessor is used as the signal processor to achieve the digitalization of force feedback loop. The signal demodulator, the accelerometer r information resolve and the output of control signal are realized by the microprocessor. Compared to the former design scheme, it simplified the circuit and reduced the power consumption. On the real design of the hardware circuit, the sample circuit, the process circuit and the moment current flow generator are designed on the result of the system analysis. And the constant-current source errors are analyzed in detail considering its influence for the system precision.The real time embedded operation systemμC/OSII is transplanted according to the systematic requirement, and the sampling program, demodulation program, accelerometer resolve program and the control algorithm are completed under that operation system, the under sampling demodulation is adopted for the signal demodulation, which could simplified the demodulation algorithm.At the end of the paper, the whole system is tested, and the design scheme is certified. The system accuracy and the stability is improved compare to the former design scheme.