Guidance of cable drawn implements

Abstract

A combined analytical and experimental approach was used to develop the equations of motion of a 1/6 scale cable drawn model disk harrow. The lateral deviation was found to be a linear combination of the lateral force applied to it and of the angle of the disk with respect to the centerline. The turn rate was directly proportional to the applied turning moment. A computer simulation model based on these equations was written and validated. Simulations showed the equations of motion could accurately model the path of an implement subjected to disturbance loads. Rolling coulters and a movable hitch were evaluated as possible steering methods with rolling coulters being selected for further development. The equations of motion were linearized and simplified and used to predict the behavior of a coulter steering system. The steering system was implemented and PID control parameters were selected based on the ultimate period method developed by Ziegler and Nichols. The system could steer the disk along a straight line with an accuracy of (plus or minus)$0.5 cm.