Studies on Automatic Tillage with Crab-steering Vehicle (II)

Method for Detcting Field-end

Abstract

It is indispensable for the automatization of field machine to detect the end of field. This may be solved, in paddy field, by detecting levee. The infrared opto-electric sensor of reflection type which is attached on the head of a vehile in downward reclined posture senses the reflection from side slope of levee. Output voltage of the sensor is processed by a micro processor. The process method is as follows. The output voltage is sampled at certin interval(V_n) and the difference V_n-V_n-1 is calculated. Thd index I_n=V_n·|V_n-V_n-1| and the the mean I_n=(I_n+I_n-1)/2 are obtained, and In is one after another compared with the level k·I_n (k; coefficient). If I_n exceeds the level, a command is signalled to stop the vehicle.
In this paper, above-mentioned method was presented together with the output voltage changes of sensor scanning model field and levees of various cross sections and practical field. The results of field tests with the trial detecting device mounted on a vehicle were discussed.
The region of sensor heights and angles that levee could be detected was indicated by three curved borders in the represented graph taking height and angle in both axes. Three borders are defined by the relation of sensor height or angle to the dimension of levee cross section, and the characteristics of the sensor. The stop positions in the same combination of sensorr height and angle were measured on 9 types of levee. The combination that minimized the standard deviation of measured values was 30cm in sensor height and 30deg in sensor angle or 40cm and 45deg. If the sensor is set in that combinatin, the stop position of the vehicle will not differ so much for any type of levee.