Empirical Characterization of a Highperformance Exteriorrotor Type Brushless DC Motor and Drive Recently, brushless motors with especially high torque densities have been developed for applications in autonomous aerial vehicles (i.e. drones), which usually employ exterior rotortype geometries (ERBLDC motors). These motors are promising for other applications, such as humanoids and wearable robots; however, the emerging companies that produce motors for drone applications do not typically provide adequate technical specifications that would permit their general use across roboticsxe2x80x93for example, the specifications are often tested in unrealistic forced convection environments, or are dronespecific, such as thrust efficiency. Furthermore, the high magnetic pole count in many ERBLDC motors restricts the brushless drives able to efficiently commutate these motors at speeds needed for lightlygeared operation. This paper provides an empirical characterization of a popular ERBLDC motor and a new brushless drive, which includes efficiencies of the motor across different power regimes, identification of the motor transfer function coefficients, thermal response properties, and closed loop control performance in the time and frequency domains. The intent of this work is to serve as a benchmark and reference for other researchers seeking to utilize these exciting and emerging motor geometries.

Motorpropeller Matching of Aerial Propulsion Systems for Direct Aerialaquatic Operation Electric aerial propulsion systems are commonly used for many smallscale unmanned aerial vehicles (UAVs), providing a light and powerful method of generating thrust. In the emerging area of aerialaquatic vehicles, most existing prototypes rely on such systems to propel themselves in both air and water. As the density of water is three orders of magnitude larger than that of air, a spinning aerodynamic body in the medium will experience significantly higher torque at the same speed. This results in aerial propulsion systems to be heavily mismatched underwater, as the required torque is higher than the drive torque that a typical aerial motor can provide. Here, an indepth investigation of such offdesign operation is conducted. Based on numerical simulation, we identify the feasible operating range of such systems and present an evaluation framework that identifies a motorpropeller combination from a component database that maximises underwater performance while ensuring aerial thrust requirements are met.