Optimal Performance Trim Procedure for Multirotor Vertical Takeoff and Landing Vehicles

Abstract

The present paper proposes a general approach capable of determining the set of trim commands, aerodynamic control surface actuation, and/or engine thrust regulation that allow specific trimmed steady-state flight conditions of nonconventional vertical takeoff and landing vehicles under given performance constraints. Exploiting the peculiarity of these vehicles to have redundant controls, namely more controls than those strictly required to define steady-state flight conditions, their trim problem is recast into a constrained minimization of a cost function. This approach is of particular interest in that it allows the identification of control settings for multirotor vehicles that, at the same time, guarantee trimmed flight conditions and optimization of selected target functions such as, for instance, performance or noise emission. The proposed approach is numerically applied to quadcopter and hexacopter configurations for three flight conditions (level forward flight, climb, and coordinate turn), and three strategies of trim by different trim variables (rotor angular velocity, blade collective pitch, and combination of angular velocity and blade collective pitch). The effect of the introduced cost function is investigated, comparing the outcomes of minimum control effort and minimum torque strategies. The results achieved demonstrate the capability of the proposed algorithm to exploit redundant controls of multirotor vehicles for identifying selected optimal trim operative conditions.