A Uniform Control Allocation Method for Distributed Electric Propulsion Aircraft using Iterative-based Approach and Coordinate Transformation

This paper presents a novel control allocation method which can be used in all flight modes for Distributed Electric Propulsion (DEP) Vertical Takeoff and Landing (VTOL) aircraft. Since the multiple sets of tiltable propulsors of this type of aircraft would cause nonlinearity in the control effective model and add extra constraints to the model, a constant control allocation matrix can not be directly applied as in the case of quadrotors. To deal with the difficulties, a cascade two-step allocation method is proposed so that the constraints on the same propulsion sets can be naturally satisfied. Based on this, an iterative allocation method based on coordinate transformation is developed to adapt the unique geometry of the propulsors, the nonlinearity problem is then solved by breaking the control effective model into two subsystems, and the nonlinear problem can be iteratively solved from two linear system. Coordinate transformation is also introduced into the allocation to deal with the constantly changing geometry of the propulsors so that the method can work in all flight modes. Finally, the proposed method is implemented in our self-developed platform to carry out simulations and experiments, the results show our method is well suited to the unique features of this type of aircraft in all the flight modes.