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Automatic guidance of tractors in the mechnized farming practice has taken the attention of Agricultural engineers.For this to be truly practical on the farm,it should be econoical,simple to operate,and entirely contained on the vehicle.Steering automation has been implemented successfully on agricultural vehicles on the basis of analoge-type components,i.e.sensors, controllers,and actuator elements.Different types of steering system such as:leader-cable, laser conrolled, radio-operated,and contactor type have been developed for automatic guidance.The present study was aimed to develop a reliable,versatile and easy to maintain system to fit the economy and technology level of farmers for hill side range developent.The proposed system featured a pair of sensors located along the length of the tractor.The output signals from the opto-couplers operated by sensors,were led into the central conrol unit.The final output signal , indicative of left-turn or right-turn comand,was introduced to a hydraulic motor (actuator) by a solenoid valve.The actuator could then rotate the steering wheel shaft in the desired direction.The system was successfully tested on four different sites with average slope of 11-14% using a chiesel seeder, two bottom mounted moldboard plow, three bottom mounted moldboard plow and without hitching any implements behind the tractor.Plots of the contour line height of each test track Y versus the actual elevation of 14 equally spaced points along each track X produced the following relationships:
Y=1.009X-0.930 3 bottom mounted moldboard plow
Y=1.000X-0.002 2 bottom mounted moldboard plow
Y=0.999X+0.011 chiesel seeder
Y=0.999X+0.014 tractor with no implement
Indicating a reasonably acceptable perforance.