Discussion on “Acoustic noise and vibration of rotating electric machines” and the lectures “Evolution and significance of noise specifications” by D.D. Stephen and “Noise from electrical machines—the community and the worker” by R.J. Davies

1970 ◽  
Vol 117 (1) ◽  
pp. 127
Keyword(s):  
Acoustic Noise ◽  
Electric Machines ◽  
Electrical Machines ◽  
Noise And Vibration

Commercialization of Active Isolation for Jet Aircraft

1997 ◽  
Author(s):  
Steve C. Southward ◽  
Douglas E. Ivers ◽  
Geoff C. Nicholson
Keyword(s):  
Control System ◽  
Vibration Control ◽  
Acoustic Noise ◽  
Development Program ◽  
Flight Test ◽  
Test Time ◽  
Vibration Source ◽  
Noise And Vibration ◽  
Transmission Path ◽  
Active Isolation

Abstract Active Noise and Vibration Control (ANVC) technology is a proven solution for noise and vibration problems in aircraft. The challenges in commercializing this solution range from the development issues of choosing the best actuation, sensor, and control technology to obtaining sufficient flight test time and satisfying FAA requirements. This paper examines significant case histories in the progression of the Lord active vibration control program from conception to market. Throughout the development program, several important discoveries were made regarding the performance, reliability, and economics of Active Isolation Systems (AIS) in jet aircraft. First, practical speaker-based solutions cannot achieve global acoustic noise cancellation for engine tones above about 200 Hz. A comparatively small array of structural actuators placed in the dominant transmission path, such as in or near the engine mounts, are capable of global cancellation in the cabin up to at least 500 Hz. Second, the performance is generally better when cabin microphones are used as error sensor inputs because the AIS control system can compensate for flanking paths better than if accelerometers are used as error sensors. Third, when the actuators are placed in the dominant transmission path and close to the vibration source, the control system will simultaneously achieve global acoustic noise reduction in the cabin and vibration reduction in the aircraft structure without affecting the engine casing vibration levels.

Measurement and Analysis of Torque Ripple in Inverter Driven Electric Machines

2021 ◽  
Vol 263 (6) ◽  
pp. 227-235
Author(s):  
Mitchell Marks
Keyword(s):  
Best Practices ◽  
Torque Ripple ◽  
Electric Machines ◽  
Slow Speed ◽  
Noise And Vibration ◽  
Torque Response ◽  
Measurement And Analysis ◽  
Method Of Measurement ◽  
Different Sources ◽  
Speed Method

Torque ripple in electric machines can create both noise and vibration. While torque ripple is often well understood theoretically, it is much more difficult to accurately predict and measure. Often torque ripple is measured as a function of magnets and slot interaction at extremely low speed, but this can only be extrapolated to understand its implications for noise and vibration and is not useful for understanding torque response during dynamic scenarios like a change in load. The slow speed method of measurement also neglects possible switching effects on the torque profile. This paper will explore challenges in measuring the different sources of torque ripple and give an alternative method to measure torque ripple at higher speeds and also dynamically. This will include best practices and examples.

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