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Autotracking: Examples of Order Tracking Measurements Without Using a Tacho Probe

Brüel & Kjaer Sound and Vibration Measurement A/S-Svend Gade, Thorkild Find Pedersen, Henrik Herlufsen, Hans Konstantin-Hansen
  • Technical Paper
  • 2007-08-0031
Published 2007-05-23 by Society of Automotive Engineers of Japan in Japan
When analyzing the behavior of rotating or reciprocating machines, it is often necessary to estimate and track the phases and magnitudes of harmonic orders of the fundamental frequency of the machine. The fundamental frequency is typically measured using dedicated sensors, e.g., proximity probes of photo-sensors that require direct access to the rotation parts of the machine, which can be difficult. In this paper the autotracking method where the fundamental frequency is extracted from the measured vibration/or acoustic signals is described. Hereby the need for a dedicated tacho probe is avoided. The method is founded by Bayesian statistics, where the posterior distribution of the fundamental frequency is computed conditioned on the measured data and a harmonic model of the signal. Limited prior knowledge is required for initialization. A number of application examples are included in the paper: Vibration signal from a Drivetrain and Turbocharger, sound signal from a HATS placed inside a DaimlerChrylser SmartCar and finally sound & vibrations signal from the engine compartment of a Volvo S60.
 

The Use of Order Tracking in Vibro-Acoustic Measurements: A Novel Approach Eliminating the Tacho Probe

Brüel & Kjaer Sound Vibration Measurement A/S-Svend Gade, Thorkild Find Pedersen, Henrik Herlufsen, Hans Konstantin-Hansen
  • Technical Paper
  • 2006-08-0001
Published 2006-05-01 by Society of Automotive Engineers of Japan in Japan
When analyzing the behavior of rotating or reciprocating machines, it is often necessary to estimate and track the phases and magnitudes of harmonic orders of the fundamental frequency of the machine. The fundamental frequency is typically measured using dedicated sensors, e.g., proximity probes or photo-sensors that require direct access to the rotating parts of the machine, which can be difficult. In this paper we propose a new order tracking method where the fundamental frequency is extracted from the measured vibration and/or acoustic signals. Hereby the need for a dedicated tacho probe is avoided. Apart from the fundamental frequency, the method can also estimate the amplitude and phase of specified orders. The method is founded on Bayesian statistics, where the posterior distribution of the fundamental frequency is computed conditioned on the measured data and a harmonic model of the signal. Limited prior knowledge is required for initialization. The new method is tested on vibration signals from the drivetrain of a passenger car and is compared with two other order tracking methods: re-sampling based order tracking and…
 

Order Tracking in Vibro-acoustic Measurements:A Novel Approach Eliminating the Tacho Probe

Br¨uel & Kjær Sound & Vibration Measurement A/S-Thorkild Find Pedersen, Henrik Herlufsen, Hans Konstantin Hansen
Published 2005-05-16 by SAE International in United States
When analyzing the behavior of rotating or reciprocating machines, it is often necessary to estimate and track the phases and magnitudes of harmonic orders of the fundamental frequency of the machine. The fundamental frequency is typically measured using dedicated sensors, e.g., proximity probes or photo-sensors that require direct access to the rotating parts of the machine, which can be difficult. In this paper we propose a new order tracking method where the fundamental frequency is extracted from the measured vibration and/or acoustic signals. Hereby the need for a dedicated tacho probe is avoided. Apart from the fundamental frequency, the method can also estimate the amplitude and phase of specified orders. The method is founded on Bayesian statistics, where the posterior distribution of the fundamental frequency is computed conditioned on the measured data and a harmonic model of the signal. Limited prior knowledge is required for initialization. The new method is tested on vibration signals from the drivetrain of a passenger car and is compared with two other order tracking methods: re-sampling based order tracking and…
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Operating Deflection Patterns Under Non-Stationary Order Related Forces

Brüel & Kjær Sound & Vibration Measurement A/S-Mehdi Batel, Brian MacMillan, Henrik Herlufsen
Published 2003-05-05 by SAE International in United States
In this paper, an interesting structural dynamics technique is presented to represent an operating deflection pattern, under order related forcing loads. In this technique, the measurements are performed using the Phase Assigned Spectrum technique with the use of reference and roving response accelerometers. Rotating components in car engines generate cyclic excitation forces at the fundamental rotational frequency and its harmonics and sub-harmonic components. This excitation will result in structural resonances being excited by those particular orders, at specific rotational speeds.The paper discusses in general the use of Order Tracking analysis under non-stationary conditions, for the determination of order-tracked deflection shapes obtained by Phase Assigned Spectrum analysis. A Vold-Kalman Order Tracking analysis is also performed on the set of data for extraction of time order waveforms or Phase Assigned Orders.
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Frequency Domain Techniques for Operational Modal Analysis

Brüel & Kjaer Sound and Vibration Measurement A/S-Svend Gade, Nis B. Møller, Henrik Herlufsen, Hans Konstantin-Hansen
  • Technical Paper
  • 2002-08-0304
Published 2002-07-23 by Society of Automotive Engineers of Japan in Japan
Operational Modal Analysis, also known as Output Only Modal Analysis, has in the recent years, been used for extracting modal parameters of civil engineering structures and is now becoming popular for mechanical structures. The advantage of the method is that no artificial excitation needs to be applied to the structure, or force signals to be measured. In this paper, the non-parametric technique based Frequency Domain Decomposition (FDD), as well as the more elaborate Enhanced Frequency Domain Decomposition (EFDD) identification technique are discussed.The methods are illustrated by measurements on a passenger car in normal operating conditions in the Brüel & Kjaer laboratory.
 

Modal testing of mechanical structures subject to operational excitation forces

Brüel & Kjaer Sound and Vibration Measurement A/S-Svend Gade, Nis B. Møller, Henrik Herlufsen
Structural Vibrations Solutions ApS-Rune Brincker, Palle Andersen
  • Technical Paper
  • 2001-08-0002
Published 2001-05-23 by Society of Automotive Engineers of Japan in Japan
Operational Modal Analysis also known as Output Only Modal Analysis has in the recent years been used for extracting modal parameters of civil engineering structures and is now becoming popular for mechanical structures. The advantage of the method is that no artificial excitation need to be applied to the structure or force signals to be measured. All the parameter estimation is based upon the response signals, thereby minimizing the work of preparation for the test. This test case is a controlled lab set-up enabling different parameter estimation methods techniques to be used and compared to the Operational Modal Analysis. For Operational Modal Analysis two different estimation techniques are used: a non-parametric technique based on Frequency Domain Decomposition (FDD), and a parametric technique working on the raw data in time domain, a data-driven Stochastic Subspace Identification (SSI) algorithm. These are compared to other methods such as traditional Modal Analysis.
 

Order synthesis studies on sound quality using Vold-Kalman filtering

Brüel & Kjaer-Sven Gade, Henrik Herlufsen, Hans Konstantin-Hansen
Vold Solution Inc.-Håvard Vold
  • Technical Paper
  • 1999-08-0265
Published 1999-05-19 by Society of Automotive Engineers of Japan in Japan
In this paper an order synthesis study on sound quality using Vold-Kalman filtering is presented. This filter allows for the high-performance simultaneous tracking of orders in systems with multiple independent axles. Orders extracted as waveforms have no time delay (i.e., no phase bias) and may hence be used for playback, synthesis and tailoring. This paper gives an example, where a dominating order has been removed from a motor run-up signal. The original signal, the dominating order as well as the signal with the order removed have been studied in detail using various techniques such as FFT, 1/3 octave and loudness analysis.
 

New Analysis System for Combined Sound Quality Work and General Noise and Vibration Trouble Shooting

Brüel & Kjaer A/S-Svend Gade, Henrik Herlufsen, Poul Ladegaard
  • Technical Paper
  • 978112
Published 1997-05-21 by Society of Automotive Engineers of Japan in Japan
PULSE, the PC-based Multi-analyzer System Type 3560 from Brüel & Kjaer allows multiple analyzers to be defined in the same system, enabling measurements to be made in parallel, thus ensures consistency in the data to be analyzed between FFT analyzers and Real-time Digital Filter analyzers providing standardized octave and one-third octave analysis. Furthermore it allows a wide range of applications to be performed on the same software/hardware platform, such as Sound Quality, Order Tracking analysis, etc.As a result, PULSE enhances productivity in reduced testing time, reduced set-up and learning time, a wide application range and reduced reporting time.This paper will focus on the basic concepts in Sound Quality. It starts with some general comments on the present status of Sound Quality. After that a short description of all the steps in a Sound Quality optimization process is given. Finally, the application to produce trouble shooting and development is explained and the link between product design, manufacturing and quality control is highlighted.
 

New Pc and Ms-WindowsSt Based Multichannel Digital Order Tracking Analysis System

Brüel & Kjaer-Svend Gade, Henrik Herlufsen, Hans Konstantin-Hansen
  • Technical Paper
  • 968058
Published 1996-05-15 by Society of Automotive Engineers of Japan in Japan
A new multi-analyzing system, PULSE, the Brüel & Kjaer Multi-analyzer System Type 3560 was released on the 1st of January 1996.PULSE can be configured with up to 32 measurement channels, 64 signals and 8 analyzers, giving the possibility of for example simultaneous, FFT-baseband, FFT-zoom, 1/3 octave, Overall and Order Tracking analyses of the same or different signals.This paper will focus on Order Tracking Analysis applications.
 

Determination of Structural Damping Using the Impulse Response Function

Brüel & Kjær Denmark-Svend Gade, Henrik Herlufsen
Published 1991-05-01 by SAE International in United States
This paper shows how the impulse response of each individual resonance in a frequency response function is calculated via a series of weighting functions and then used for damping calculations.The technique is not new (1)* but previously it has been indicated (2, 3) that when using pseudo-random excitation, T > 2.5τ must be fulfilled in order to make accurate damping measurements, where T is the Fast Fourier Transform record length and τ is the decay constant of the damping.It is shown that tolerable damping estimates can be made even if the record length T is as small as 0.05τ. This is because the short record length produces an aliasing phenomena on the amplitude of the impulse response function only - not on the slope of the decay.
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