Design And Implementation Of Intergrated Positioning System Based On Strapdown Inertial Navigation

In recent years,various applications based on location services have developed rapidly.These applications put forward higher requirements for the accuracy and continuity of location information.GNSS(Global Navigation Satellite System)has the problems of weak anti-jamming ability and low output frequency,while the inertial navigation system has high autonomy and fast sampling frequency,but its accuracy is poor in the long run.The combination of the two can achieve complementary advantages.The precision of inertial navigation depends on the inertial devices,and the cost of high-precision inertial devices which are commonly used in the military-industrial complex is high;In the field of centimeter positioning of civil urban vehicles,the cost needs to be controlled to achieve large-scale application.Based on the strapdown inertial navigation,the thesis designs and implements a low-cost and high-precision integrated positioning system for vehicle applications under the two positioning modes of GNSS:pseudo-range single point and RTK(Real-Time Kinematic).Firstly,the integrated positioning system model based on speed,position and heading angle is designed by loose combination method,and simulation results show that the algorithm can effectively suppress the long-term divergence of inertial navigation.Secondly,the integrated positioning system is designed by using pseudo-range single point which is at meter-level.According to whether the vehicle is stationary and whether GNSS is effective,four states can be divided in the system.The static detection method proposed in this thesis and vehicle incomplete constraint are used to compensate the error of the system in different states.Then,the hardware of IMU381 and NEO-M8T is designed,meanwhile,the software of inertial navigation module,satellite positioning module,fusion filter module and results output module is designed and realized.Then,in order to achieve centimeter-level positioning accuracy,the integrated positioning system in RTK mode is designed and implemented.Aiming at the problem that the ambiguity is difficult to be fixed after the signal is unlocked in RTK,a method of detecting urban complex scenes and an auxiliary solution strategy are proposed in the thesis.The inertial navigation results are used as the initial value of RTK solution in each epoch,so as to accelerate the ambiguity fixed speed when vehicles passing through complex scenes such as bridges and tunnels in urban.In addition,according to the standard deviation of RTK position and velocity,a dynamic adjustment method of the observation noise parameters in the fusion filter is designed,and then the software design and implementation of the integrated positioning system are carried out.Finally,the two systems in this thesis are tested in the urban environment.The tests show that the two integrated positioning systems can achieve meter-level and centimeter-level positioning accuracy respectively,and can still achieve high-frequency and effective positioning results when GNSS is invalid.Moreover,the auxiliary solution strategy can effectively shorten the time of the first fixed solution after the vehicle passes through the bridge and other complex scenes.