Trajectory tracking is one of the key technologies for high-precision agriculture and has been the research focus by a large number of academics. In order to design a simple trajectory tracking control scheme, an adaptive sliding mode control based on lateral deviation is proposed. To reduce the chattering phenomenon, an adjustable parameter associated with the sliding surface and system error is introduced, by which the forward gain value can be regulated with the state change. According to the established tractor model, the desired front wheel angle can be obtained as the output of the sliding mode controller. A modified Smith predictor structure based two degree of freedom control scheme is designed to follow the desired front wheel angle. The effectiveness of the designed trajectory tracking control system is demonstrated by simulations, especially the performance of preventing chattering phenomenon.

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Trajectory tracking is one of the key technologies for tractor automatic navigation. Its main purpose is to adjust the steering mechanism of the tractor to follow the planned trajectory. Thus, in this paper a trajectory tracking control system is designed for an agricultural tractor with the electric power steering mechanism. A DC brush motor is added on the steering column of the tractor and the hardware circuits for the steering controller are designed to control the front wheel angel. The three degrees of freedom model of the tractor is established, and a trajectory tracking control system is proposed including a fuzzy sliding mode controller and a steering angle tracking controller designed according to the internal mode control and minimized sensitivity theory. The effectiveness of the designed trajectory tracking control system is demonstrated by simulation analyses in reference to the planed trajectory.