Design And Implementation Of Simu Data Acquisition System Based On FPGA

With the development of navigation technology,the navigation computer,i.e.,the core of navigation information processing,is supposed to perform better.In order to meet the requirement of strong operation ability,high precision,good reliability,small volume and low power for navigation computer,FPGA + DSP scheme is used in this paper after analyzing some exsisting methods for the navigation computer.The main task of this paper is to design the data acquisition system of Strapdown Inertial Measurement Unit(SIMU),including hardware platform and software system.The SIMU used in this paper consists of three laser gyroscopes and three quartz flexible accelerometers,in which the laser gyroscopes have integrated the temperature sensors.FPGA is responsible for data acquisiting,timing control and serial communication,and DSP focuses on navigation calculation.Through the analysis of laser gyroscope output signal,the front and back state contrast method is used to make four-subdivision,direction sensing and reversible counting for AB phase of the gyroscopes.As the laser gyroscope is easily affected by wide range of temperature change,it is necessary to acquire the temperature signal of the gyroscope as the benchmark of temperature compensation.Temperature signal is an analog quantity,which needs to be converted into digital quantity through AD chip LTC1867.In view of the latch-up effect of laser gyroscope,this scheme adopts the FIR filter to filter the dithered signal.The I/F conversion circuit has been integrated into SIMU,so that the positive and negative pulse signal output by the accelerometer can be directly counted reversible by FPGA.The gyro,accelerometer and temperature signal after pre-processing in the FPGA are transmitted to the DSP through the EMIF interface for navigation calculation,and then the speed,position,attitude and other navigation information can be obtained.In the process of navigation calculation,there exists the finite rotation non-commutative error according to Picard method,so it can only work in low-dynamic environment.The equivalent rotation vector method is compensated the non-commutative error,so that it can work in highly-dynamic environment.In order to lighten the workload of DSP and make it concentrate on navigation calculation,the navigation result is transmitted to the central computer by FPGA through the 422 serial port.After the debugging of hardware circuit and the simulation of software system,the combination of laser gyroscope and accelerometer are calibrated on the three-axis turntable.Finally,a large numbers of static navigation experiment s are carried out on the turntable to verify the rationality of the design and stability of operate.