Design Methodology for Small-Scale Unmanned Quadrotors

The increasing usage of low-Reynolds-number (10,000-100,000 tip Reynolds number) scale quadrotors for civilian and military applications provides the impetus for the development of reliable design methodologies. At present, there is limited understanding of how to accurately size quadrotor components for a specific mission. These components include the rotors, motors, speed controllers, batteries, and airframe. However, empirical relationships may be derived for these components based on manufacturer data. The present research identifies the key factors driving vehicle weight and provides a framework for implementing these factors in a micro air vehicle design tool. Starting from basic rotor parameters (such as radius, solidity, and airfoil section) and an initial gross takeoff weight estimate, a blade element momentum theory framework coupled with computational-fluid-dynamics-generated sectional airfoil tables provides an acceptable estimate of low-Reynolds-number rotor power and torque for required thrust. The aerodynamic power and torque along with desired flight time and speed drive the weights of the quadrotor components. The proposed sizing tool has been validated against a series of existing quadrotors with 30-1000 g gross takeoff weights. Current results show that individual weight groups can be predicted generally within a +/- 10% deviation and the gross takeoff weight of each vehicle is predicted within a +/- 4% variation.