LQ Servo control design with Kalman filter for a quadrotor UAV

This paper deals with reference signal tracking control of a quadrotor UAV (Unmanned Aerial Vehicle). Before controller design, a nonlinear simulation model is needed, to be the base of design and the first testbed for the resulted controllers. The next step should be the linearization of the nonlinear model in hovering mode, and the reduction of the resulted linear model. The reduced linear model is controllable and observable. The control goal was to track a spatial trajectory with the helicopter center of gravity. For this purpose, an LQ Servo controller (with double integrator) was designed, augmented with a Kalman filter state observer. The resultant controller provided good tracking performance for a slowly varying reference signal, also on the nonlinear model! After the transient response, the tracking error was below 1 cm which provides safe handling even in indoor applications. The time of transients was approximately 4 seconds which is acceptable

Loop shifting and non-conservative qLPV design

As an extension of the robust H∞ theory, the time domain design based on linear matrix inequalities (LMI) is a conceptually simple and efficient framework to obtain qLPV controllers. However, the constructed scheduling variables are not always suitable for an efficient implementation. This paper investigates the possibility of constructing the scheduling block of a qLPV controller explicitly, i.e., in the form of a linear fractional transformation (LFT). It is shown here that if both the primary and dual multiplier LMI equations lead to maximal indefinite subspaces and a coupling condition holds, the problem can be solved and a constructive algorithm results to build the desired scheduling variables