Research On Deflection Angle Measurement System Of Tractor Guide Wheel Based On GNSS/INS

The accuracy and stability of the measurement of the deflection angle of the tractor guide wheel directly affect the accuracy and stability of the tractor’s automatic navigation operation.At present,tractors mainly use traditional angle sensors to measure the deflection angle of the tractor guide wheel,but the steering process of the tractor is very complicated.The measurement of the deflection angle of the guide wheel by the traditional angle sensor cannot meet the needs of high accuracy,high stabilit y and simplified installation and commissioning in actual production.Therefore,this paper proposes a tractor steering wheel deflection angle measurement system based on the Global Navigation Satellite System(GNSS)and Inertial Navigation System(INS)to measure the real-time dynamic angle of the tractor steering wheel In order to solve the problem of angle sensor accuracy,stability,simplified installation and debugging and GNSS short-term information loss.Theoretically analyze the principles of GNSS a nd INS and Kalman,extended Kalman and unscented Kalman filter algorithms,design bench tests and filter the test results,and determine the optimality with accuracy,stability and delay time as the evaluation criteria The filtering algorithm finally appli ed the GNSS/INS-based tractor steering wheel deflection angle measurement system to the automatic navigation system for field trials.This article is based on the national key research and development plan project-agricultural machinery operation Beidou automatic navigation control technology and device project.The specific research content and results are as follows:(1)In order to solve the problem that GNSS is prone to short-term signal loss and the increase of INS system iteration error increases ove r time,which cannot guarantee the long-term accurate driving of the automatic navigation system,this paper proposes the basic system with INS as the tractor test platform,GNSS GNSS/INS tractor steering wheel deflection angle measurement system composed of auxiliary systems.(2)Three GNSS/INS-based tractor deflection angle measurement systems based on large-angle right deviation,large-angle left deviation,and S-shaped curve driving were designed and tested.Carry out Kalman,Extended Kalman and Tracele ss Kalman filtering on the test results of the bench respectively.The degree of deviation between the filtered curve and the angle sensor measurement curve is used as the accuracy criterion of the filtering algorithm,and the smoothness of the filtering c urve is regarded as the stability assessment of the filtering algorithm The standard compares and analyzes the three filter curves and the real measurement curve of the angle sensor,and finally determines that the unscented Kalman filter is the optimal fi lter algorithm as the built-in algorithm of the automatic navigation system for field trials.(3)According to the GNSS and INS-based tractor steering wheel deflection angle measurement system proposed in this paper,the steering performance test test and straight line automatic navigation performance test test under two conditions of asphalt pavement and farmland environment are designed.Through the steering performance test test,the accuracy,stability and delay time of the steering wheel deflection angle measurement system proposed in this paper when measuring fixed angles of 1°,5° and 15° are tested;through the straight line automatic navigation performance test test,the steering wheel is analyzed The application effect of the deflection angle measurement system when the tractor is performing linear automatic navigation.The test results of the linear automatic navigation performance test show that under the condition of asphalt pavement,the average lateral deviation is 0.102 cm,the standard deviation is 0.371 cm,the maximum lateral deviation is 1.755 cm,the linear automatic navigation system error is 1.045cm(2σ);farmland environmental conditions The average value of the lower lateral deviation is 0.687 cm,the standard deviation is 0.498 cm,the max imum lateral deviation is 1.852 cm,and the error of the linear automatic navigation system is 2.107cm(2σ).Therefore,the deflection angle measurement system of tractor guide wheel based on GNSS and INS proposed in this paper solves the problems of diffic ult installation of angle sensor,difficult calibration and easy damage of angle sensor due to mechanical connection,loss of GNSS signal in a short time,and error of INS system increases with time The problem of increased error can be applied to automati c navigation systems for navigation operations.