Research On GNSS/INS Integrated Navigation System Of Field Road Vehicle In Hilly Area

The field roads in hilly area are narrow,winding and undulating.Conventional vehicles are difficult to drive on the roads,making the transportation of agricultural materials and products become a serious problem for agricultural production in hilly area.At the present stage,most of the agricultural materials are transported by motorcycles,carts,tricycles,etc.These modes of transport have some problems,such as high labor intensity and low efficiency.In addition,the labor force in hilly area is seriously lacking.These factors seriously affect the development of agriculture in hilly area.Hilly area urgently needs a highly automated field road vehicle,which can reduce people's labor intensity.This paper research on the GNSS/INS integrated navigation of the vehicle based on the characteristics of the vehicle driving on the hilly area field roads to realize the automatic driving of the vehicle.The main research includes these:(1)The whole scheme of the GNSS/INS integrated navigation system for field road vehicle.According to the respective characteristics and complementary characteristics of the inertial navigation system(INS)and the global navigation satellite system(GNSS),combining with the practical application requirements of the vehicle driving on field roads in hilly area,a real time kinematic(RTK)GNSS navigation system an INS inertial navigation sensor combined with a three-axis accelerometer and a single-axis are selected,and GNSS/INS integrated navigation was designed.Fuzzy neural network control is used as an automatic driving control strategy.(2)The attitude calculation of vehicle and the error model of GNSS/INS integrated navigation system.Based on the analysis of the attitude calculation's coordinate system and attitude calculation algorithms,the vehicle's attitude calculation is deduced.According to the analysis of output information and error's generation principles of GNSS and INS,the state error equations and observation error equations of the GNSS/INS integrated navigation system are deduced.(3)Using Kalman filter to fuse the information of GNSS/INS integrated navigation system.According to the characteristics of the output information of GNSS/INS integrated navigation system,indirect Kalman filter is selected for information fusion.An improved method for estimating the adaptive factor is used to improve the Kalman filter's adaptive capability.Using Matlab for simulation analysis,the result shows that the Kalman filter can fuse the output data of GNSS and INS well and obtain a more accurate and reliable navigation information.(4)Fuzzy neural network control strategy for the automatic driving vehicle.According to the motion model of the field road vehicle,a five-layer fuzzy neural network controller with three input and one output is designed.The input parameters include lateral deviation,heading deviation and path curvature.The output parameter is the turning angle of vehicle.The fuzzy neural network's learning algorithm is designed,and the inertial term is used to improve the convergence speed of the fuzzy neural network.The offline training of fuzzy neural network is completed by Matlab,and test data is used to test the learning effect.The test result shows that the fuzzy neural network has a good control effect.(5)Experiment on field roads in hilly area.Using the vehicle designed by our research team to do experiment repeatedly on field roads in hilly area to verify the feasibility of GNSS/INS integrated navigation system.The result of experiment shows that the GNSS/INS integrated navigation system has good control accuracy when the vehicle is driving by itself automatically on a conventional field road.In the east direction,the maximum deviation is 8.9 cm and the average deviation is 4.6 cm.In the north direction,the maximum deviation is 11.9 cm and the average deviation is 4.9 cm.In the skyward direction,the maximum deviation is 17.3 cm and the average deviation is 6.8 cm.When the vehicle's GNSS signal is covered by vegetation for a short time,the vehicle has a slight offset,but it can still travel along the planned road.It shows the GNSS/INS integrated navigation system has a good anti-interference ability.