TRAJECTORY CONTROL AND ITS APPLICATION TO APPROACH A TARGET: PART II. TARGET APPROACH EXPERIMENTS

A positioning method using a simple laser sensor was developed and employed for navigation to a target. The laser sensor scans existing reflectors and measures their directions and positions using a triangulation method. After calibration, the accuracy of distance measurement was around 10 cm. A control system that steers an autonomous vehicle following a human-operated tractor was also developed. Experiments regarding the application of the laser sensor confirmed that an experimental autonomous tractor could follow a leading human-operated tractor without collision. However, the autonomous tractor tended to take shortcuts due to feedback. Automatic fertilizer refilling experiments were conducted using an autonomous vehicle equipped with a broadcast fertilizer distributor. The laser positioning method was used to locate the fertilizer supplier. Results of the field experiment showed that the trajectory control algorithm proposed in Part I could guide the vehicle with satisfactory accuracy for refilling. The main factor contributing to navigation error was the limit of the steering angle of the front wheels.