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Relative rotor phasing for multicopter vibratory load minimisation

Part of: Written Paper Prizes 2023

Published online by Cambridge University Press:  21 October 2021

R. Niemiec Open the ORCID record for R. Niemiec [Opens in a new window] ,
F. Gandhi  and
N. Kopyt
R. Niemiec*
Affiliation:
Center for Mobility with Vertical Lift, Rensselaer Polytechnic Institute, Troy, NY, USA
F. Gandhi*
Affiliation:
Principal Investigator
N. Kopyt
Affiliation:
Center for Mobility with Vertical Lift, Rensselaer Polytechnic Institute, Troy, NY, USA
*
Emails: niemir2@rpi.edu; fgandhi@rpi.edu
Emails: niemir2@rpi.edu; fgandhi@rpi.edu
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Abstract

This study focuses on vibration reduction for quadcopters and octocopters with elastic, two-bladed, fixed-speed, variable-pitch rotors through the use of relative rotor phasing. The study defines phase modes such as a pitch phase mode with relative phasing between the front and aft rotors, a roll phase mode with relative phasing between the left and right rotors, and a differential phase mode with relative phasing between the clockwise and counter-clockwise spinning rotors for both the quadcopter and the octocopter, as well as additional higher harmonic phase modes for the octocopter. Parametric studies on individual phase modes indicate that, for the quadcopter in forward flight, the pitch and roll phase modes can almost entirely eliminate the 2/rev vibratory forces (at the aircraft level), but the 2/rev vibratory moments cannot be minimised at the same time. By simultaneously using multiple phase modes, a Pareto front can be generated and a solution selected based on the relative emphasis on force or moment vibration reduction. For the octocopter, it was observed that individual higher harmonic modes (specifically the 2c or 2s modes) could almost entirely eliminate both the 2/rev vibratory forces and moments, simultaneously. Compared with vibration levels in forward flight that might, on average, be expected if the rotors were randomly phased, a 62% reduction of a composite vibration index can be achieved on a quadcopter, and complete elimination of vibration was achievable on an octocopter, with appropriate rotor phasing.

Keywords

MulticopterElectric Vertical Takeoff and LandingeVTOLVibration
Type
Research Article
Information
The Aeronautical Journal , Volume 126 , Issue 1298 , April 2022 , pp. 710 - 729
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Copyright
© The Author(s), 2021. Published by Cambridge University Press on behalf of Royal Aeronautical Society

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