Backstepping variable structure control for tractor-aircraft system

The problem of enhancing tractor-aircraft system path tracking and stability through controlling tractor steering angles is addressed. Considering the nonlinearity associated with the articulated angle between tractor and aircraft, a nonlinear 3DOF traction system dynamic model combining with steering system is established. To cope with the variation of aircraft parameters, tractor steering controllers are designed for the extended system based on constructive backstepping variable structure control method, and boundary layer method is adopted to modify the controllers. The simulation results show that front steering controller achieves path tracking successfully. When the articulation angle is too large, additional rear steering controller can greatly improves the system stability. And the controllers have the ability of restricting the outer disturbance and parameter perturbations.