Research And Design Of Digital Algorithm For Gyro Drive System

Micro-Electro-Mechanical System(MEMS)Gyroscopes have broad applications and development prospects in the fields of aviation,aerospace and navigation for its advantages of small size and low power consumption.MEMS gyroscopes driving system generally adopts closed-loop control.There are two main types of gyroscopes closed-loop driving system,one is analog closed-loop driving system,the other is digital closed-loop driving system.Within it there are also two types of control,one is phase control and the other is amplitude control.Analog closed-loop driving system mainly uses discrete analog components to implement its closed-loop circuit.The analog components will age and decay over time,this causes the analog component’s parameters to deviate from its original value and this will affect the performance and even the functioning of the gyroscopes.Phase-locked loop is an important part of the closed-loop driving system that controls phase,and the loop filter in phase-locked loop is to maintain the stability of the loop.The loop filter of analog phaselocked loop is very difficult to design because the analog components building the loop filter may suffer from temperature change and components aging.Whereas,the loop filter of digital phase-locked loop has to use huge number of standard cells to implement large delay that is needed by the loop filter which results in large wastage of chip area.Automatic gain control is also an important module of the closed-loop driving system that controls amplitude.Automatic gain control has to take care of a wide range of signal amplification,so if implemented using analog circuits will inevitably result in high power consumption because the internal operationl amplifier has to be designed to have high gain and large bandwidth.To solve the above shortcomings,this thesis proposes a digital closed-loop driving system based on digital phase-locked loop and digital automatic gain control.Using digital circuits to implement the control function and the phase-locked loop has the advantages of fixed codings,fixed parameters and fixed responses which will not be affected by temperature change or components aging.Hence,this can solve the temperature change and components aging problems faced by the analog circuits and analog phased-locked loop.The digital loop filter in this thesis uses a reversible counter to replace the huge number of standard cells to implement the required large delay,this not only make the design simpler but also reduce the large wastage of chip area.Digital automatic gain control uses simple combinational logic circuits and shifting of digital bits to represent the wide range of signal amplification,so the high power,high gain,large bandwidth operational amplification will not be needed.This makes the design simple and does not consume much power.The MEMS gyroscope digital closed-loop driving system is simulated and verified on modelsim platform and is realized on Xilinx FPGA.Experimental results show that linearity of-74.375 dB and bias stability of 43.659°/h are achieved.