Lateral control of UAVs: Trajectory tracking via Higher-Order Sliding Modes

Nonlinear sliding mode approach is developed in this paper for lateral control of UAVs. The enabling guidance and control has achieved good performance with different flight conditions and evasive maneuvers. The proposed strategy can recover from large track errors without effecting the saturation constraints on the control input. The structure of guidance and flight control system is designed in a two loop configuration. The main contribution of this work is the development of new guidance scheme in which inner loop dynamics are also considered during the derivation of outer guidance loop for robust lateral control and never forcing unsuitable commands. HOSM (Higher-Order Sliding Mode) Real Twisting Algorithm is used because of relative degree 2 constraint, which maintains S and S = 0. The outer loop for guidance uses heading error angle, lateral track error and bank (roll) angle φ for the control law and PD controller is used in the inner loop. The designed guidance control system´s robustness and performance is verified via computer simulations using high fidelity nonlinear 6-degrees-of-freedom (6-dof) Yak-54 UAV model under different scenarios, with small and large track errors and in the presence of wind disturbances.