| The real-time kinematic technology,is a difference method for real-time processing of carrier phase observations of two measurement stations,it can be real-time access to centimeter-level positioning solution and has strong operational,wide range of applications and other advantages.The current mature RTK technology has hundreds of thousands of costs at every turn,so the applications of RTK positioning technology in the agricultural is not used widely.With the country's strong support for agriculture,agricultural automation and intelligence technology will be rapid development.Obtaining high precision positioning solution is the basis for realizing automatic navigation of farmland vehicle.The research takes the practical application of farmland navigation as the primary purpose.It is mainly based on Piksi positioning module of Swift Company in the United States.At first,experiment is designed for precision analysis.Later,some improvements have been made to some hardware such as radio stations and antennas according to the project requirements.Then using filtering algorithm to deal with the data.Finally the Piksi RTK system was successfully applied to farmland tractors.The main conclusions are as follows:(1)Piksi module is a high cost-effective positioning module,its RTK static horizontal positioning accuracy can be accurate to 1 cm.When using the Piksi module,it is necessary to take full account of the surrounding environment,and tall buildings can not be nearby.The console control software can save the six types of data in three formats,and fully meet the user's needs.The Piksi module data read directly by the serial port,the data has been encrypted by Swift's specific SBP binary protocol,if you do not use the console software can not directly access latitude and longitude data.When building an RTK system,the base station location information needs to be set by the console software and sent to the rover.(2)The conversion of spatial coordinates and navigation plane coordinates satisfies the requirements of accuracy analysis.The Piksi RTK system static accuracy was analyzed by the standard deviation(?),circular error probable(CEP),root mean square error(RMS),2 times mean square error 2DRMS index.Single Piksi module point positioning accuracy(2drms,95%)is about 8 m,the RTK static accuracy(2drms,95%)is about 1.5 cm.Design of dynamic dual-track experiment verify the feasibility of using linear fitting method for dynamic linear accuracy,when the flow station is linearly moving at an average speed of 0.4 m/s to 2.3 m/s,the positioning accuracy obtained by fitting is about 1.5 cm.Using the difference between the distance of measured point to the fitting center and the fitting radius evaluate the positioning accuracy of the circular motion,it was found that the accuracy of linear motion at 0.4 m/s-1.6 m/s is also about 1.5 cm.Considering the point-to-point problem in the actual application process,the measurement error obtained by the fitting analysis is small and the true dynamic accuracy of Piksi RTK is about 3 cm-5 cm after a preliminary judgment.(3)The 3DR digital radio of the Piksi RTK system is less power and the transmission distance is limited,the actual transmission distance is about 300 m-400 m in an open environment.The Canadian P900 radio and GSM gain antenna replace the system's own antenna and radio,the transmission distance is about 1 km in the presence of buildings in the campus and 3.5 km in an open environment.As the transmission distance increases,the positioning accuracy of the improved Piksi RTK system is declining.Using the least squares interpolation verify the relationship between the transmission distance and the accuracy,it is found that the transmission distance will drop to the sub-meter level after more than 3.2 km.(4)The data processing model is established by Kalman filter.The static and dynamic positioning accuracy within the transmission distance can be doubled after filtering.Within 1 km from the base station after filtering,the static positioning accuracy is about 1 cm,it meets the two requirements of the subject about transmission distance and accuracy.The dynamic Kalman filter model has a good correction effect on data under the linear motion trajectory,the dynamic error after filtering is about 1 cm-3 cm.(5)The improved Piksi RTK system is applied to the agricultural tractor.The trajectory of the RTK data is better than that of the tractor.Using the fixed point of the map as the base station method to solve the accuracy of the problem in the practical application.According to farmland experiment analysis,the dynamic accuracy of the Piksi RTK system in farmland vehicle navigation is about 2 cm-6 cm,compared with the dynamic simulation experiment analysis,the accuracy is basically the same,and the precision after filtering is about 1 cm-3 cm.Indicating that Piksi RTK system can meet the requirements of automatic navigation of farm vehicles,it has a wide application prospect in the field of precision positioning of agricultural machinery... |
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