A linear quadratic tracker for VTOL-UAV trajectory control with multivariable constraints

A guidance controller that takes into account the constraints on the control amplitude and the control rate for trajectory tracking of Bombardier's CL-327 VTOL-UAV is addressed. With references given by a trajectory generator over a receding horizon, a discrete linear quadratic tracker (LQT) is designed. The constraints are considered using a sequential quadratic programming (SQP) algorithm which computes a feasible reference, the closest as possible to the desired reference, that ensures the control does not induce constraint violations. By doing so, the performance and stability proven in the linear analysis are still valid. The performance of this controller is compared to a linear quadratic regulator, which is similar to a PID output feedback controller. The LQT controller with the SQP algorithm gives tight path following in the presence of constant wind or gusts, as it ensures high disturbance rejection in hover flight.