Hover performance of a cycloidal rotor for a micro air vehicle

In recent years, interest has been growing in a new class of very small flight vehicles called micro air vehicles (MAVs). Hover capability is highly desirable with respect to the mission requirements of these vehicles. Due to the small size of MAVs and the low Reynolds number regime in which they operate, scaling down conventional rotorcraft configurations to the MAV scale may not yield optimum performance. Unconventional vehicle configurations can be explored to realize high endurance hover capable MAVs. This paper investigates the hover performance of a small-scale cycloidal rotor to determine its viability for use in a micro air vehicle. A 6 inch diameter prototype rotor was constructed and tested to determine the effects of number of blades, blade pitch angle, and rotational speed on thrust output and power requirements. Pressure distribution was measured to obtain insight into the downwash and flow through the rotor. An analytical model, using a combination of vertical axis wind turbine theory and an indicial solution for the aerodynamic response was developed to predict rotor performance, and was validated with the experiments. The performance of the cycloidal rotor was compared to that of a conventional rotor of the same diameter in terms of power loading. Based on the analytical model and the experimental results, a conceptual design of an MAV utilizing cycloidal propulsion was developed. The conceptual cyclo-MAV utilizes two cycloidal rotors, providing thrust, propulsion, and control. Complete vehicle weight is envisaged to be 240 g, with two three-bladed rotors of six inches diameter.