基于GPS和陀螺仪的水稻插秧机自动导航设计(11)

基于GPS和陀螺仪的水稻插秧机自动导航设计

Y.Nagasaka et al./Computers and Electronics in Agriculture43(2004)223–234233 paddy?elds are innately slippery.However,as can be seen in Fig.10,there is a correlation between steering angle and yaw angle,which leads to deviation from the desired path.GPS data have a latency of about70ms and the automated system also has a latency that is a function of mechanical delay,calculation time and data transfer time.It should,therefore, be possible to improve the precision of the operation if the automated rice transplanter is controlled based on vehicle dynamics on soft ground.

In this experiment,conventional mat-type rice seedlings were used,with two persons supplying seedlings to the rice transplanter at the edge of the?eld.At the headland,it took about60s to turn and realign to the next desired path.Planting the experimental plot took 15min.

4.Conclusion

An automated rice transplanter was developed and autonomous guidance operation was conducted.In this study,the position data that was in?uenced by the inclination of the vehicle was corrected by FOG sensors data.FOG drift was corrected by comparing the deviation of lateral direction calculated using the yaw angle and vehicle speed with the deviation calculated using GPS data.The maximum deviation from the desired straight path is12cm and deviation is5.5cm at0.7m/s operating speed after correcting for the yaw angle offset.This is only enough accuracy for rice transplanting operations,and it is not accurate enough for spraying and mechanical weeding operations after rice transplanting. Since it is necessary to drive an autonomous vehicle between the crop row to make spraying and mechanical weeding operations,the maximum deviation must be reduced less than5cm. In this study,a simple proportional controller was used for steering control.However,for more precise operations,it is necessary to analyze the vehicle dynamics in the paddy?elds and to evaluate and improve the steering controller.Since the manual-operating speed of a rice transplanter is usually around1m/s,it is also necessary to evaluate the control algorithm at speeds of more than1m/s.

At the headland,there was more than a10cm deviation from the desired path at the beginning of the operation.As the vehicle traveled along the wheel track when moving backward,the turning circle diameter must have been the same as the distance to the following operating path.It is necessary to evaluate the turn control algorithms.

Rice transplanting operation requires someone to supply the seedlings.It was necessary to supply seedlings every200m in this experiment.This poses a problem for making ef?cient operations and for establishing fully autonomous rice transplanting operations in larger paddy?elds.This,however,is solved when long mat type hydroponic seedlings (Tasaka,1998)are used.This would require a seedling supply every30ares for a six-row rice transplanter so more ef?cient operations could be made.

Acknowledgements

This research project was supported by the Ministry of Agriculture,Forestry and Fisheries of Japan.

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