基于GPS和陀螺仪的水稻插秧机自动导航设计(6)

基于GPS和陀螺仪的水稻插秧机自动导航设计

228Y.Nagasaka et al./Computers and Electronics in Agriculture 43(2004)

223–234

Fig.5.Correction of initial yaw angle offset and drift.

The deviation of lateral direction d is obtained by integrating both sides.d =

vψd t (3)The deviation of lateral direction for a de?nite period of time measured by the RTKGPS is d GPS .For the discrete data value,the deviation of lateral direction d Gyro estimated by the vehicle speed and the yaw angle is expressed as Eq.(4).In this equation,the yaw angle at a point of time i is ψ(i ),the vehicle speed,measured by GPS,is v (i ),n is the time after starting the calculation and t s is the sampling interval.

d Gyro =n/t s

i =0v(i)ψ(i)(4)

When the distance is l n ,the offset of yaw angle ψoffset is calculated as Eq.(5).In this equation,the authors assume that d GPS and d Gyro are suf?ciently smaller than l n .ψoffset =arctan d Gyro l n ?arctan d GPS l n ～=d Gyro ?d GPS l n

(5)d Gyro is calculated at a point 35–40m after starting operation.The condition of the paddy ground is ?at in this interval,and thus,stabilizes the motion of the vehicle.If the interval is longer,the calculated results are in?uenced by the vehicle sideslip and the error is inte-grated.So,in this study,l n is 5m and ψoffset is calculated at a point 35–40m after starting operation.The initial offset and the FOG sensor drift were corrected for every operation path before starting.

2.4.Path planning

Before starting operation,the computer must create a desired path,along which the rice transplanter travels.In this study,the paddy ?eld was assumed to be rectangular.The four corners:A,B,C,and D,in the ?eld were measured beforehand.The sowing width of a six-row rice transplanter is 1.8m.Since a paddy ?eld usually has only one entrance,the desired path depends on the width of the ?eld.

When the quotient (the ?eld width divided by the sowing width of 1.8m)is an even number,the automated rice transplanter starts operating near the entrance.The desired path is set up so that the distance from side AB to the ?rst path and that from side CD to the last path are equal.When the quotient is an odd number,it starts operating at the opposite

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