UAV trajectory tracking and formation flight guidance based on feedback linearization and sliding mode observer

This paper proposes a guidance law design for trajectory tracking of a leader UAV and formation flight of pursuer UAVs. According to nonlinear kinematics for both problems, the feedback linearization theory has ben used. Therefore, using this theory, the nonlinear problem has been transferred to a linear one and using the linear control theory the control parameters has been determined to achieve the desired performance. In the trajectory tracking problem, assuming a constant velocity leader, a change of the independent variable from the time to the downrange has been performed and the problem is transferred to a single-input single-output control problem, consequently, the controller is designed. In the formation flight problem, assuming pursuers with the bounded controllable velocity, we have a two-input two-output nonlinear system. Supposing no communications between pursuers and the leader, a second order sliding mode observer is utilized to estimate the required states in formation flight controller. Results show that the settling time of trajectory tracking error of the proposed nonlinear guidance law is almost 30% better than the nonlinear trajectory tracking controller based on the proportional navigation guidance law. Also, the designed formation flight has a good performance in controlling the formation flight. Also, the sliding mode observer is able to estimate the leader states even in the presence of noise.