Generic modeling and control of unbalanced multirotor UAVs

In the past two decades, the increasing incorporation of Multirotor Unmanned Aerial Vehicles (MUAVs) in both civilian and military applications has made necessary the development of numerous MUAV configurations with different features and capabilities to suit various missions. This article proposes a generic nonlinear mathematical model and an adaptive control strategy for unbalanced MUAV configurations, where the vehicle's center of gravity is assumed to be arbitrarily positioned. The model is composed of two parts: the MUAV dynamics model, and the MUAV mapping matrices. To define the structure and the values of these mapping matrices for any MUAV configuration, two novel MUAV classification methods together with a new set of MUAV geometric descriptive parameters are introduced. Subsequently, a configuration-adaptive controller that adapts to the MUAV configuration types is developed, and applied through nonlinear simulations to three different MUAV configurations: a quadcopter, a hexacopter, and a tilting-rotors bicopter. The simulation results showed the effectiveness of the generic approach adopted as a design and analysis tool for designers/researchers to easily model, control, simulate and compare different MUAV configurations for a particular application, and as a step towards a universal control methodology for MUAVs.