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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Update on Electric Motor Noise

Electric motors like those used in concept Advanced Air Mobility vehicles generate noise relevant to the acoustic profile of those vehicles. This work presents ongoing efforts to study, understand, and predict the noise generated by these types of motors. Efforts to perform experimental and simulation investigations of motor vibration modes are presented. Then recent acoustic measurements of operating motors and the resonant tones they generate is discussed. Lastly an update of ongoing efforts to measure real world vehicles is provided.

Electric motor noise↗
NASA NTRS2018

Electric Motor Noise from Small Quadcopters: Source Characteristics - Part II

The increased interest in electric motors for propulsion systems has driven interest in quantifying the contribution of electric motor noise to the overall sound levels and possible human annoyance of the propulsion system. This work presents acoustic measurements of electric motors used for small quadcopters to quantify the sound produced by a number of outrunning motors with different types of controllers. Results are presented for loaded and unloaded motors as installed and uninstalled configurations. Motor resonance frequencies were measured and computed. Current probe measurements showed that the supply current from the controllers contained significant harmonic content for the conventional and sinewave controllers. Acoustic results showed motor noise is typically radiated at frequencies near the mode 2 vibration frequency at roughly 5000 Hz. Electric motor noise was evident in the spectra produced by many of the motor-controller combinations for motors loaded with propellers with levels often greater than those for the motor alone due to increase in the stator magnetic flux density with increased current. An installed configuration produced increases in acoustic radiation over that of the uninstalled motor in a frequency range near the mode 1 vibration frequency near 1200 Hz. A companion paper (Part I - Acoustic Measurements), focuses on source identification using a phased array and directivity characteristics for a baseline configuration.

Motor Resonance Frequencies↗
NASA NTRSDate not supplied

An Initial Vibro-Acoustic Model for Predicting Electric Motor Noise

A system-level tool to predict electric motor noise, suitable for trade studies of eVTOL and UAM aircraft, does not exist. This work describes the ongoing effort to develop such a tool. It utilizes a 3 phase prediction routine that models the electro-magnetic interactions of the electric motor, the resulting structural vibrations of the motor rotor, and finally the acoustic propagation generated by those structural vibrations.

Electric Motor Noise↗
NASA NTRS2018

Electric Motor Noise from Small Quadcopters: Part II - Source Characteristics

The increased interest in electric motors for aircraft propulsion systems has driven interest in quantifying the contribution of electric motor noise to the overall sound levels and possibly human annoyance of the propulsion system. This work presents acoustic measurements of electric motors used for small quadcopters to quantify the sound produced by a number of outrunner motors with different types of controllers. Results are presented for loaded and unloaded motors as well as installed and uninstalled configurations. Motor resonance frequencies were measured and computed. Current probe measurements showed significant harmonic content in the supply current from the controllers for both the conventional and sinewave controllers. Acoustic results showed motor noise is typically radiated at frequencies near that for azimuthal vibration mode number 2 of the rotor which occurs at roughly 5000 Hz. Electric motor noise was evident in the spectra produced by many of the motor-controller combinations for motors loaded with propellers with levels often greater than those for the motor alone due to increases in the stator magnetic flux density with increased current. An installed quadcopter configuration produced increases in acoustic radiation over that of the uninstalled motor in a frequency range near the 1200 Hz azimuthal vibration mode 1 of the rotor.

Henderson, Brenda↗
NASA NTRS2018

Update on Electric Motor Noise Measurements and Predictions

Results from recent acoustic and vibration experiments with small electric motors are presented. The results are compared with finite element analysis and analytical predictions. The relevance of electric motor noise to the overall noise produced by small quadcopters is highlighted. Progress toward quiet loading approaches is discussed.

Electric Motor Noise↗
NASA NTRS2018

Electric Motor Noise from Small Quadcopters: Part 1 - Acoustic Measurements

There is increased interest in using electric motors to drive propulsors across a range of small air vehicle classes. Applications include both vertical lift and conventional takeoff and landing systems for Small Unmanned Aircraft Systems. Mission profiles call for integrating these systems into urban airspaces exposing populated areas to new noise sources. In addition to the propulsor noise from rotors and propellers, electric motors are expected to contribute to the overall sound levels and possibly human annoyance. This work presents acoustic measurements of electric motors used for small quadcopters to characterize the sound and identify sources with and without a propeller. Free field microphone measurements were used to determine directivity and a phased microphone array was used to identify sound sources. A companion paper (Part II - Source Characteristics and Prediction) compares the far field results with current probe measurements of the signal driving the motor, the structural response of the motor case, and describes prediction methods of electric motor noise.

Electric Propulsion↗
NASA NTRS2018

Electric Motor Noise for Small Quadcopters: Part I - Acoustic Measurements

There is increased interest in using electric motors to drive propulsors across a range of small air vehicle classes. Applications include both vertical lift and conventional takeoff and landing systems for Small Unmanned Aircraft Systems. Mission profiles call for integrating these systems into urban airspaces exposing populated areas to new noise sources. In addition to the propulsor noise from rotors and propellers, electric motors are expected to contribute to the overall sound levels and possibly human annoyance. This work presents acoustic measurements of electric motors used for small quadcopters to characterize the sound and identify sources with and without a propeller. Free field microphone measurements were used to determine directivity and a phased microphone array was used to identify sound sources. A companion paper (Part II – Source Characteristics and Prediction) compares the far field results with current probe measurements of the signal driving the motor, the structural response of the motor case, and describes prediction methods of electric motor noise.

Aircraft Noise↗
NASA NTRSDate not supplied

Surface Vibration Measurement and Analysis for UAM/UAS Electric Motor Noise

Urban Air Mobility vehicles are an emerging class of vertical lift vehicles using electric motors to drive multiple rotors for lift. The outrunner electric motors that are commonly used, may be capable of generating noise that could contribute to the vehicle’s overall noise profile and could generate cabin noise. Understanding and predicting the noise requires more knowledge of the rotor vibrations and eventually a model to predict the frequencies of those vibrations. This work presents a measurement of the rotor vibrations of two different small-scale motors. Two techniques to measure the surface vibration were used. The displacement spectra are compared with acoustic measurements. A finite element analysis model is used to predict the rotor resonance frequencies. The predicted frequencies are in fair agreement with the experimentally observed vibration frequencies, but requires further work to understand discrepancies.

Electric Motor Noise↗
NASA NTRSDate not supplied

Preliminary Analysis of Moog SureFly Electric Motor Noise Measurements

The results of acoustics measurements on the installed and unloaded axial-flux electric motor used on the Moog SureFly® vehicle are presented and compared to previous ground run-up measurements for the vehicle. The directivity of the motor was found to be significantly different than that obtained for much smaller 2 – 4 kW radial flux motors tested previously in the Acoustic Test Laboratory at NASA Glenn. Significant radiation occurred at shaft orders between 17 and 20 and at order 30. Peak radiation levels occurred near the highest speeds expected for the vehicle. There was an indication that some of the tones appearing in the spectra obtained in the previous ground run-up test were associated with the motor.

Urban Air Mobility↗
NASA NTRS2018

Electric Motor Noise Testing

A brief update of the progress towards RVLT Milestone L490 Initial acoustic model for kW class electric motors. A quiet loading device has been created that will allow for acoustic testing of a motor with different loads applied. Testing has also begun on a larger motor, the Scorpion SII-4020. Description of the installation of this motor as well as initial measurements reported. These include acoustic spectra and beamforming for source localization.

Cluts, Jordan↗
NASA NTRSDate not supplied

Progress on Electric Motor Noise Modeling

Progress toward the development of a motor noise model for system type studies is presented. The presentation focuses on efforts to model the motor shell vibrations and the resulting acoustic radiation. Finite element and experimental modal analysis results for a 4 kW motor are presented and compared. An analytical model for the acoustic radiation is presented.

Urban Air Mobility↗
NASA NTRSDate not supplied

Acoustic Measurements for the Moog S-250 Vehicle in Hover

Acoustic measurements for hover conditions and electric motor noise tests were conducted for the Moog S-250 research aircraft, an RPM-controlled quadcopter-type Urban Air Mobility (UAM) vehicle with four sets of contra-rotating rotors. The objectives of the study included determining the minimum far-field distance, the noise characteristics, and the potential for electric motor noise to contribute to the overall acoustic radiation for the full-scale UAM vehicle. Acoustic data for full-scale aircraft are critical for determining the impact of these vehicles on the surrounding communities. The results showed the far-field was reached by 8.1 single rotor diameters or 2.7 vehicle diameters as defined by the longest tip-to-tip rotor dimension for the vehicle. In hover, the peak acoustic radiation occurred at a declination angle of roughly 29° below the midplane between the upper and lower rotors. The lowest acoustic levels occurred below the aircraft. The electric motor noise studies, conducted with the rotors removed, showed motor noise radiated at shaft orders 17 – 20, whereas rotor noise covered the range of 2 – 24 shaft orders. There was some evidence that electric motor noise was present in previous ground run-up measurements.

Urban Air Mobility Noise↗
NASA NTRSDate not supplied

Moog SureFly® Hover Test Update

An update on the Moog SureFly vehicle acoustic hover test is presented. The intent of the effort was to acquire data that will be used to identify the acoustic far-field for the vehicle and the importance of electric motor noise relative to other sound sources for hover. The data will also be available to assess sound levels for future vertiports. The flights were completed in June 2022 at the Cincinnati Municipal Airport – Lunken Field.

jet noise↗
NASA NTRSDate not supplied

Development and Validation of an Initial Electric Motor Rotor Vibration Model

An overview of the development of a low fidelity prediction tool for electric motor rotor resonant modes and frequencies. These predictions are useful for the prediction of UAM motor noise during the design phase. Finite Element Analysis of motor rotors has led to the development of a parameterized model to predict these modes shapes. This has in turn allowed to a curve-fit based model from parametric sweeps. These curves can predict resonant frequencies and shapes for 1-5kW class motors without running a simulation.

acoustics↗