Experimental Methods for Multi-Propeller Noise Characterisation

ABSTRACT

Multi-rotor/propeller systems, such as those found on eVTOL and DEP aircraft, produce significant levels of tonal noise governed by the acoustic interference and aerodynamic interactions between neighbouring rotors. This presentation reports experimental far-field noise of a multi-propeller system using two methodologies, in which the relative phase between propellers is either held constant or varied at a constant rate. Rotation speeds were precisely controlled in both configurations to resolve the phase-dependent noise modulation. The measured far-field noise is compared against a low-order model based on Hanson’s tonal noise formulation with reasonable agreement, although some discrepancies reveal additional noise potentially associated with aerodynamic interactions and not represented in the acoustic model.

Mr. Yi Zilei (Christopher) is a final-year PhD student in aerospace engineering at the University of Bristol. His project focuses on experimental noise characterisation of multi-propeller systems in non-axial inflows, with a sideline in low- to mid-fidelity numerical modelling. He works within the Aerodynamics and Aeroacoustics Research Group (A2RG) under the supervision of Dr Esmaeel Masoudi and Prof. Mahdi Azarpeyvand.

From Bio-Inspiration to Mission-Capable Flight: Development of Insect-Inspired Flapping-Wing Micro Air Vehicles

ABSTRACT

Flapping-wing micro air vehicles offer several distinctive advantages at small scales, including high aerodynamic efficiency, agile manoeuvrability, relatively low acoustic signatures, and enhanced tolerance to collisions. Their practical development, however, remains challenging because of the complexity of flapping mechanisms and flight-control systems, as well as limitations in structural durability, payload capacity, and onboard sensing. This talk presents the development of a series of insect-inspired tailless flapping-wing micro air vehicles, progressing from fundamental mechanism design to mission-capable flying prototypes.

The presentation introduces the wing-rotation and clap-and-fling mechanisms used for thrust generation, together with wing-stroke-plane modulation for independent roll, pitch, and yaw control. It also discusses the integration of a customized PX4-based autopilot, control allocation, controller-gain and filter tuning, and experimental flight validation. Key developments include stable first-person-view flight, altitude and position hold, rapid maneuvering and stabilization, enhanced low-vibration gearboxes, passive ceiling perching, detachable camera payloads, payload deployment, and flight endurance of up to approximately ten minutes. The effects of wing materials and flapping kinematics on audible noise are also examined.

The talk concludes by outlining ongoing efforts to develop smaller, quieter, and more autonomous platforms through lightweight sensing, obstacle avoidance, navigation in GPS-denied environments, improved tolerance to wind-gust disturbances, advanced fabrication methods, and tighter integration of mechanical and electronic systems.

Dr. Nguyen Quoc Viet joined TL@NUS in September 2012. He received his PhD in Aerospace and Mechanical Engineering in 2008 and subsequently conducted postdoctoral research at Konkuk University in South Korea. His research interests include the development of bio-inspired flapping-wing aerial vehicles, indoor flight navigation and control, and bio-inspired robotic systems.