基于GPS和陀螺仪的水稻插秧机自动导航设计(7)

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 Agriculture 43(2004)223–234

229(a)(b)

C

C

Fig.6.Planed desired path (the quotient is the ?eld width divided by the operation width).(a)The quotient is even;(b)the quotient is odd.

side of the entrance.The desired path is set up so that the distance from side CD to the ?rst path and that from side AB to the last path are equal.While the vehicle is moving to the operation starting point,the moving path is set at a distance of 30cm from the last desired operating path.Fig.6shows the desired path planned before operation.

2.5.Straight drive

In paddy ?elds,it is thought that the paddy ground is more ?imsy than upland ?elds.There are several papers about steering control in upland ?elds.O’Connor et al.(1996)used a steering controller based on a set of linear motion equations.Cho and Lee (2000)used a fuzzy controller for an autonomous operation for an orchard speed sprayer.Kise et al.(2002)developed an optimal steering controller and they obtained good curved-path guidance results.Inoue et al.(1997)developed an adaptive steering controller correcting steering system delay.Most of them analyzed vehicle dynamics and made a dynamic model,then decided the control parameters.

However little research has been done regarding vehicle dynamics (Weise et al.,2000)in paddy ?elds.The authors could not make a dynamic model at this time due to the soil conditions which were not constant,making it is dif?cult to ?x the parameters.So in this study,the authors used a simple proportional controller for steering control before evaluating effectiveness of the advanced controllers in such loose-ground like paddy ?elds.

The rice transplanter must be driven along the desired path.The steering is set to follow as closely as possible to the desired path.The steering angle δaim is given as Eq.(6),where the deviation from the target line is d and the yaw angle is ψ.The value of K p1,K p2is determined according to the vehicle speed.

δaim =K p1d +K p2ψ(6)In this study,the steering control parameters were obtained experimentally.K p1is 0.636and K p2is ?0.604at a speed of 0.7m/s.The steering speed is proportional to the difference between the target steering angle and actual angle,and is controlled by the pulse width mod-ulation (PWM).The GPS data quality indicator was monitored while the rice transplanter traveled automatically.If the radio link between the GPS base station and GPS rover station was lost for any reason,the clutch is released and the operation is interrupted.The engine

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