Design Of Outdoor Integrated Positioning System Based On AHRS And GNSS

Low-cost positioning system is widely used in agriculture,military,aerial photography and other fields.However,with the gradual diversification of carrier types and application scenarios,the early single positioning system is limited by its own limitations and can't meet the needs well.Combined positioning system can solve this problem and has become a research hotspot.This paper summarizes the development of GNSS(Global Navigation Satellite System)positioning system and AHRS(Attitude Heading Reference System)positioning system,analyzes the shortcomings of some traditional integrated positioning technologies,and designs and implements an integrated positioning system based on attitude reference system and global navigation satellite system.The system uses motion sensor ICM-42688-P,geomagnetic kit RM3100 and positioning module ATGM332D-5N as on-chip sensors,which has the advantages of small volume,low power consumption and low cost.Firstly,this paper designs an algorithm for multi-sensor fusion to solve the position information for the combined positioning system.The algorithm uses rotation matrix,Butterworth low-pass filter and Haversine formula to process the sensor information,and uses Kalman filter for multi-sensor information fusion,which makes the advantages of AHRS and GNSS subsystems complement each other,meets the requirements of short-term positioning and long-term positioning,and can overcome some shortcomings of traditional GPS / MEMS(Micro-Electro-Mechanical System),GPS / odometer and other schemes.At the same time,the algorithm can be easily transplanted to the system using accelerometer,gyroscope,magnetometer and GNSS module,and has certain universality.Then it introduces the hardware selection,device characteristics,circuit design and prototype of the lower computer realized in this paper.The performance of the selected sensor can well meet the requirements of the system.Then it introduces the data acquisition task,attitude calculation task,position information calculation task based on multi-sensor information fusion algorithm and data transmission task for communication between upper and lower computers.The lower computer program uses Free RTOS for multi task management and scheduling,which has good stability.Then the upper computer software designed in this paper is introduced.The upper computer is developed based on Qt platform and adopts modular design method.It is divided into two modules: interface display layer and communication bottom layer.In the communication bottom layer module,e CAL is introduced as the inter process communication middleware to improve the data processing and distribution ability of the communication bottom layer.The interface display layer cooperates with the communication bottom layer to realize the functions of real-time displaying the output data of the lower computer,querying or setting the parameters of the lower computer.Finally,the static experiment and two dynamic experiments designed to test the performance of the system are introduced.The experimental results verify the reliability of the algorithm,the rationality of hardware design and the stability of the system.It is proved that the system has high positioning accuracy under outdoor conditions and has good application prospects in civil fields.