Realizing Gyro-free Strap Down Inertial Navigation System Algorithm Based On DSP

Gyro-free Strap down Inertial Navigation System (GFSINS) gives up gyroes, andcalculates angular velocity by the output of gyro-free inertial measurement unit, which isformed by only accelerometers. It has a low cost, long life, low power consumption, and needno start-up time.So it is suitable for large overload, large angular velocity, and shorter voyagecarrier.Accelerometer configuration mode and angular velocity solution method is the focus ofgyro-free inertial research. In this paper, typical configuration modes are compared, and anine accelerometer configuration mode determined, which accelerometer quantity isappropriate, and output of it has angular velocity redundancy. At the same time, typicalsolution methods of angular velocity are compared. And through simulation experiments,analysis is made to find the pros and cons of each. On this basis, propose an EKF filtersolution method. EKF filter model is derived and simulation experiment is made. Simulationresults show that this method has obvious inhibiting effect of angular divergence and canimprove systerm accuracy.In order to ensure navigation and precision of GFSINS, we must reduce the system error.Main error source of GFSINS system is the accelerometer output of gyro-free inertialmeasurement unit, including accelerometer measurement error and installation error in thetooling process. For the accelerometer measurement error, given the gravity field twelveposition roll test and three-axis rotation test program, to make calibration of the errorcoefficient of static and dynamic; For accelerometer installation errors, design a calibrationprogram of the installation location error and mounting direction error. Finally, gives theaccelerometer output compensation, and makes verification experiment. The program canaccurately calibrate the error, and effectively compensate for the accelerometer output error.In the process of achieving GFSINS, it need very large amount of computation, andrequires high-precision, real-time. So design of DSP-based GFSINS systems is introduced inthe paper, including data acquisition and processing circuit and PC interface. After the overallsystem design, chip and the module selection, connection between the circuit modules,hardware system has been achieved. And then software programming is done, which includesinterrupt service routines, data transmission, the navigation solution part and other.Furthermore, a PC software program is designed, In VC++6.0, using MSComm serial portcontrol. Then data transmission between PC and DSP is achieved.