Design of Test Benches for the Hovering Performance of Nano-Rotors

Abstract

With the reduction of rotor diameter and motor size, the hovering performance measurement becomes a challenge for rotary wing Nano Air Vehicles (NAVs). Conventional test benches for Micro Aerial Vehicles fail to measure some characteristics of Nano Air Vehicles. In this paper, five test benches with highly sensitive mechanisms were successively designed in order to measure the thrust and torque of nano-rotors simultaneously and respond to the change of variables rapidly with sufficient accuracy. A commercial micro brushless motor and a micro rotor were studied experimentally and computationally at a low Reynolds range from 4,000 to 19,000. Computational and experimental comparisons were carried out and the performance of the test benches was discussed. The analysis suggests that the thrust coefficients measured by each test bench vary little from each other, while the power coefficients present significant differences. Then the hovering performance of the micro rotor and power efficiency of the motor were studied. Degradation of motor efficiency and rotor figure of merit are observed with size reduction associated with NAV applications. [1][2][3][4][5]. At present, more complicated battlefield environments or civilian security situations force soldiers to implement MAVs in urban missions. Therefore, an ever-present need has emerged to improve MAV capabilities, enabling the timely collection of comprehensive intelligence information, particularly on the ground in urban terrain. However, current MAVs are too large to provide situational awareness to the users; consequently, even smaller Unmanned Air Vehicles (UAVs) are required to allow reconnaissance inside buildings, penetration of narrow entries and transmission of data without being detected. Therefore, NAVs [6] were proposed to fulfil such missions. Referring to the definition proposed by DARPA, a NAV is defined as a UAV whose maximum dimension should not exceed 3 inches (7.5 cm) and maximum weight should be less than 10 g. Because of the special requirement of this kind of aerial vehicle, it should be able to autonomously enter buildings, stare, spot targets and transmit data at a fairly low speed or hovering mode. Hence, compared with the conventional MAV, a NAV not only has a smaller size but also the requirement of a low-speed flight and hovering ability. Furthermore, it is expected that NAVs should have an endurance of 20 minutes to complete a recognition mission within a range of less than 1 km. Consequently, the propulsion efficiency becomes a quite important parameter for NAV design. In addition, hovering performance is always a bottleneck for the design of small unmanned air vehicles as a result of the degradation of the aerodynamic performance at low Reynolds numbers. Thus, the hovering performance of NAVs was investigated in this paper. NOMENCLATUREPresently, two concepts are predominately studied in the design of NAVs [7][8][9]. One is the rotary wing; the other is the flapping wing. Previous studies have shown that the rotary-wing conce...

A Framework for Characterizing Flapping Wing Systems

“…Flapping wing unmanned aerial vehicles (UAVs) are a potential solution to the limited flight envelopes of existing fixed and rotary wing UAVs. Current systems are generally restricted to either high-speed forward flight, requiring a runway to take off or land (fixed wing) [1,2], or low-speed flight capable of hover and vertical take off and landing (VTOL), but these are inefficient over extended distances (rotary wing) [3]. Systems in nature are capable of performing both low-speed and hovering manoeuvres, as well as high-speed, efficient flight in a single system.…”

Propulsion performance investigation of bio-inspired nano rotor base on fluid–structure interaction

“…At such a low Reynolds number, the aerodynamic performance of the nano rotor degrades and the figure of merit (FM) of the nano rotor drops as a result. 4 Liu et al 5 measure the hovering performance of the propeller U-80 with diameter of 8 cm. Results show that the FM of the propeller is about 0.45 which is far lower than that of the full-scale helicopter.…”

“…4 Liu et al. 5 measure the hovering performance of the propeller U-80 with diameter of 8 cm. Results show that the FM of the propeller is about 0.45 which is far lower than that of the full-scale helicopter.…”