Wheel steering angle measurement method of agricultural machinery based on GNSS heading differential and MEMS gyroscope

Objective  To replace the link-type wheel angle sensor which is complicated to install, a method for measuring the front wheel angle of agricultural machinery was designed.

Method  GNSS antenna was used to measure the course and speed information, and MEMS gyroscope was used to measure the combined rotation speed of the tractor body and wheel. The differential difference between MEMS gyroscope and GNSS heading was calculated to obtain the wheel rotation rate. The self-adaptive Kalman filter was designed to fuse and correct the information, and wheel steering angle was obtained. Performance verification and field application test were conducted.

Result  The performance of the wheel angle measurement method designed in this paper was verified by comparing its measurement result with that of the link-type wheel angle sensor. When the course deviations of the tractor were 2.5 and 1.5 m respectively, the mean absolute errors (MAE) of the new measurement method were 1.13° and 0.87° respectively, the root mean square errors (RMSE) were 0.90° and 0.68° respectively, and the on-line times were 29.4 and 23.5 s respectively. When the method was used with the tractor navigating at the speed of 4 km/h in the field, the MAE was 0.44°, and the RMSE was 0.87°, which could meet the requirements of tractor operation on dry land.

Conclusion  The measurement method based on GNSS heading differential and MEMS gyroscope has equivalent measurement performance with the link-type wheel angle sensor. This measurement method can be used to replace wheel angle sensor for the navigation of low speed agricultural machinery.