On the System-bias Reduction for Autonomous Tractor Tracking Controls

Since the new century, high-precision sensors and high-performance controllers have ushered in high-speed development, which provides the necessary conditions for the realization of tractor self-driving system. In practical control algorithms, the tractor’s actual trajectories often show a one-sided bias in a straight-line tracking task. This phenomenon relates to asymmetry in tractor structure, in-run bias in sensors and actuators, and uncertainties in tractor model. In this paper, a control system aims to eliminate the system-bias of tractor is proposed. On the basis of ordinary tracking algorithms, the bias of heading angle is compensated and an additional PID controller is integrated to eliminate the lateral bias. Based on the Dongfeng tractor DF1004-2, this paper establishes experimental platform, equipped with controllers, sensors, actuators and other ancillary equipment. The control algorithm proposed in this paper is verified. The experimental results in a real farm field show that the tractor control system designed in this paper has robust stability and high precision, the steady-state lateral absolutely error is 85% within 5cm and 60% within 3cm, and the system bias is reduced close to zero which meets the normal operation requirements of autonomous tractors.