Abstract:
Aerodynamic optimizations of small rotors for use on a quadrotor vehicle are presented using both axial and forward flight blade element momentum theory to calculate the vehicle performance over a typical intelligence, surveillance, and reconnaissance (ISR) mission. Total energy required is minimized by allowing the rotor chord distribution, twist distribution, and hover rotational speed to vary subject to several geometric and performance constraints. The global minimum of the objective function is found using the non-gradient-based genetic algorithm NSGA-II. The main design case is a typical ISR mission consisting of a one kilometer forward flight segment at four meters per second, a five minute hover segment, and another one kilometer forward flight segment at four meters per second. Rotors are optimized for several maximum allowable chord values and compared to previous optimization results of rotors optimized for a hover mission. Both the hover condition and forward flight condition limits of the objective function are examined using rotor optimizations. Results show that compared to a hover-optimized rotor, the ISR-optimized rotor performs the ISR mission using three and one-half percent less total energy, while constraining the maximum allowable chord length during the ISR optimization resulted in up to a nine and one-half percent energy penalty compared to the unconstrained case.