A Kinematic Model and Trajectory Tracking Control of Tractor-Aircraft System Based on Front Wheel Angle Compensation

The traditional kinematic model of the tractor-aircraft system exhibits insufficient accuracy under low-speed taxiing towing conditions, resulting in significant trajectory tracking control errors and slow responses, which is difficult to meet the stringent requirements for trajectory accuracy and safety for the new departure mode. To improve the accuracy of the kinematic model and the performance of trajectory tracking, this study proposes a kinematic model compensation method based on a front wheel steering angle compensation function of the tractor. Taking the Weihai Guangtai AM210 rodless tractor and the B737-800 aircraft as research objects, a traditional kinematic model of the tractor-aircraft system is first established. Then, the traditional kinematic model and the Trucksim vehicle model are subjected to open-loop joint simulation and comparative analysis. The trajectory deviations between these two models are compensated by introducing a compensation function. Meanwhile, a trajectory tracking controller for the tractor-aircraft system based on nonlinear model predictive control (NMPC) is designed. Taking the double-shifting line condition as the reference trajectory, a closed-loop joint simulation model utilizing MATLAB/Simulink and Trucksim is built, and the trajectory simulation comparison and analysis between the NMPC controller and the traditional proportional-integral-derivative control trajectory tracking controller are conducted to verify the superiority of the NMPC controller. The tracking performance of the NMPC controller based on the traditional and compensated kinematic models is further evaluated at tractor speeds of 2 m/s and 4 m/s respectively, and the influence of different initial deviations on the trajectory tracking performance of the tractor-aircraft system is analyzed. The simulation results show that the NMPC controller based on the compensated kinematic model can reduce the peak tracking error by 61.93% and 41.63%, and the root mean square errors by 56.14% and 37.69%, at tractor speeds of 2 m/s and 4 m/s, respectively. Under the condition of existing initial deviations, the trajectory tracking controller based on NMPC can enable the system to correct the initial deviations (lateral deviation of 0.5 to 1 m and heading angle deviation of 0.05 to 0.1 rad) within 30 s without overshoot.