Guidance control of agricultural vehicles at high field speeds

The main objective of this study was to develop an automated agricultural v ehicle guidance system capable of controlling the vehicle during high-speed agricultural field operations. The posture sensor used in the study was a kinematic differential Global Positioning System (GPS) receiver Experimenta l frequency response tests were used to develop models of steering equipmen t and vehicle dynamics. Classical feedback control was developed based on t hese models. Guidance controller effectiveness was evaluated with experimen tal step response tests. Frequency response tests of vehicle dynamics showe d that the transfer function relating vehicle lateral deviation to steering angle was a double integrator The dynamics of the automatic steering were within the same frequency range as desired vehicle dynamics. Guidance contr oller design had to compensate for both vehicle and steering equipment dyna mics. When the GPS sensor was mounted above the front axle of the vehicle, guidance control to within 16 cm of the desired path was demonstrated at sp eeds up to 6.8 m/s. Moving the sensor rearward to a more practical location added phase lag to the system, and guidance control was less effective.