Machine Vision and Soil Trace-based Guidance-Assistance System for Farm Tractors in Soil Preparation Operations

The main objective of this study was to develop a guidance-assistance system for agricultural vehicles in land preparation and tilling operations. The proposed system is a potential replacement for markers on the implement toolbar. The new automatic steering system controls the vehicle path based on the trace of the previous tilling operation on the field. Hough transform method was adapted to process forward view images of the tractor captured by a digital camera. For traces coinciding with center line of the images no correction is necessary, otherwise the relative position of the trace with respect to image center line would be an indication of the need for steering wheel adjustment. The proposed system was evaluated at various conditions including three illumination levels, previous plant residue levels (9, 24 and 50%) and soil surfaces tilled by one of the three implements (plow, subsoiler and row-crop plant furrow opener). For each test accuracy of algorithm was determined and Line Prediction Error (LPE) was calculated by the algorithm. Tests were conducted in field at three forward speeds; 4, 7.5 and 11 km h-1 and three steering angles; 10o, 16o and 20.5o. Distance error (DE) and response time (RT) for each forward speed and steering angle was measured and compared. Results indicated that various illumination and residue levels have not distorted the output of the system proposed (LPE was limited to ±1.72 cm). Response time was decreased for increasing forward speed and steering angle. Effect of forward speed on DE was significant whereas effect of steering angle on DE was not significant (0.05p).