Exploring an effective method of thrust allocation for solar-powered UAV with multiple propellers

Designing a solar-powered unmanned aerial vehicle (UAV) should center on its energy. As the majority of solar-powered UAVs have distributive propulsion systems, the optimization of their thrust allocation may effectively enhance the efficiency of the propeller and energy utilization. When the function from thrust to propeller efficiency is a convex one, the maximum allocation of the sum of propeller efficiency can be approximately converted into the two-norm minimum allocation of thrust, which can be achieved with the pseudo-inverse method. Taking the minimization of the error of the pseudo-instruction as one of optimization objectives, we obtain the mixed optimization objective. Then we use the fixed point method to achieve the mixed optimization objective. As the attenuation and hysteresis of the propeller may increase the error of the pseudo-instruction, we use the dynamic gain to compensate for the dynamic characteristics of the propeller. Finally we simulate the thrust allocation of the solar-powered UAV and the compensation for the propeller's dynamic characteristics. The simulation results, given in Tables 1 through 4 and Figs. 4, 5, 7 and 8, and their comparison show preliminarily that: (1) compared with the pseudo-inverse method, the fixed point method can not only reduce the error of pseudo-instruction but also effectively achieve maximum energy efficiency of the propulsion system; (2) the dynamic gain compensation can effectively reduce the adverse influence of the propeller's dynamic characteristics on the thrust allocation.