Optimized Thrust Allocation of Variable-pitch Propellers Quadrotor Control: A Comparative Study on Flip Maneuver

Variable-pitch propellers quadrotors possess nonlinear algebraic relations between force/moment of the system and thrust factors of the rotor dynamics. The nonlinear relations make the thrust allocation a challenging topic in overall control design. The state-dependent Riccati equation (SDRE) is selected as a controller for regulation task in fully coupled six degree-of-freedom (DoF) mode. Common designs of the SDRE fail to deliver a fully coupled six-DoF control due to under-actuation. Virtual constraints are used to deliver a position and orientation control in a cascade design. Within the structure of the SDRE, four thrust allocation methods are proposed to compute the thrust factors based on the output results of control system. Practical implementation has been the main reason to generate such allocations. The use of Mean Value Theorem makes it possible to find an implementable formalism for thrust factors since they can be categorized as non-affine systems. Agile and aggressive maneuver is one of the application of the variable-pitch propellers quadrotors; so, flip maneuver is studied to highlight the advantages of the thrust allocation methods. Analysis of the four methods and comparisons are carried out to present the advantages and disadvantages of the proposed structures.