Design and Development of an Automatic Steering System for Agricultural Towed Implements

While an auto steered tractor can improve the overall accuracy and efficiency of an operation, for operations that involve towing an implement, a significant portion of the efficiency reduction comes from uncontrolled motions of the towed implement. Therefore, there is a crucial need to study auto steering system for towed implement as well. In this study different requirements of an auto steering system for a towed implement were developed and studied. In this study the guiding performance of two local positioning sensors (Tactile and Ultrasonic sensors) under similar conditions were studied for reading different trajectories at different traveling speed. Furthermore, a fuzzy logic control algorithm was developed to continually generate correction steering signals and keep the tractor and towed implement within a certain boundary of the reference trajectory. Finally, the designed controller was implemented in a hardware-in-loop (HIL) system to analyze the performance of the controller in real world conditions. The result of this study showed that although the local guidance sensors could locate the tractor or towed implement positions with respect to plant rows accurately, limitations to the performance of sensors were also observed in certain conditions. Sensors were prone to various noises and digital filters were required to apply to collected data. Data analysis showed that at lower speeds (less than 1.79 m/s) the accuracy of sensors was ?2 cm or better. The fuzzy logic controller improved the trajectory tracking accuracy at slow speeds (1-5 m/s) for following non-complex trajectories while no major improvements were achieved for complex trajectories at these speeds. Therefore, the controller had an acceptable accuracy following straight trajectory with negligible deviations at slow speeds. Moreover, experimental results showed that the hydraulic cylinder followed the controller signals with sufficient accuracy. During the experiment the angular displacements remained in the range of ?10? and never hit the constraint of maximum achievable angle, which was ?30?. The satisfactory results showed that the designed automatic steering control system has a good tracking performance with a fast response, thus meeting the navigation control requirement of agricultural equipment to a certain extent