Quadcopters are inherently nonlinear systems but can be linearized over a small range of pitch and roll angles therefore allowing the use of standard linear feedback controllers to minimize steady state errors and improve tracking performance. However, these controllers are usually subjected to saturations in order to keep the system in the linear region. The nonlinearities arising from these saturations are generally not acceptable since they can lead to long settling times and poor transients. In this thesis we discuss and implement an Explicit Reference Governor (ERG) which re-shapes the XY-references to the system when constraint violations may occur in order to maintain stability. This is done by creating upper bounds on the value of a Lyapunov function from system constraints. These bounds are then enforced by changing the velocity of the reference command. This ERG is preferable due to its low computation times and because it provides a consistent closed-form control law that can be used to modify any stabilizing control law. The theory of the ERG is presented along with the nonlinear and linear models of the Quadcopter in which the constraints of the system are established. The ERG is then implemented in a simulation platform of the Quadcopter and is tested and compared to the Quadcopter model with and without saturations. The implemented ERG improved the settling time of the system by 25% compared to the saturated system and was able to stay within the allowable limits unlike the unsaturated system.
Advisor: Professor Mario Sznaier
Professor Mario Sznaier
Professor Bahram Shafai
Professor Rifat Sipahi