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Apparatus and method for analysing the condition of a machine having a rotating part

  • US 10,337,957 B2
  • Filed: 01/30/2013
  • Issued: 07/02/2019
  • Est. Priority Date: 01/30/2012
  • Status: Active Grant
First Claim
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1. A method for detecting an operating condition of a machine including a bearing associated with a shaft that rotates at a variable speed, the method comprising:

  • generating, by way of a position sensor applied to the machine, a position signal including position signal values indicative of a rotational position of the shaft;

    generating, by way of a vibration sensor applied to the machine, an analogue measurement signal responsive to mechanical vibrations emanating from the bearing during rotation of the shaft, said analogue measurement signal including a first vibration signal component dependent on said mechanical vibration, wherein the first vibration signal component includes a repetition frequency which depends on a speed of rotation of the shaft;

    sampling, by way of an analogue-to-digital converter, said analogue measurement signal;

    generating, from said sampling, a digital measurement data signal having a first sampling frequency;

    enveloping said digital measurement data signal, thereby generating an enveloped digital measurement data signal;

    recording a first time sequence of measurement sample values of said enveloped digital measurement data signal in a memory;

    recording a second time sequence of at least three consecutive position signal values of said position signal in said memory;

    generating a first momentary speed value based on a first recorded position signal value and a second recorded position signal value;

    recording the first momentary speed value in said memory so that the first momentary speed value is assigned to a first recorded measurement sample value between the first recorded position signal value and the second recorded position signal value;

    generating a second momentary speed value based on the second recorded position signal value and a third recorded position signal value;

    recording the second momentary speed value in said memory so that the second momentary speed value is assigned to a second recorded measurement sample value between the second recorded position signal value and the third recorded position signal value;

    generating a value indicative of a speed change based on a difference between said second momentary speed value and said first momentary speed value;

    generating, by interpolation, a first interpolated speed value indicative of a momentary speed of rotation of said shaft based on;

    said first momentary speed value,said value indicative of the speed change, anda time value, wherein said time value corresponds to a duration between said first recorded measurement sample value and a third recorded measurement sample value;

    wherein the generated first interpolated speed value is indicative of the rotational speed the shaft at a moment of detection of said third recorded measurement sample value;

    decimating said first time sequence of recorded measurement sample values based on said first interpolated speed value and based on further interpolates speed values, thereby generating a decimated enveloped digital measurement signal having a reduced sampling frequency;

    detecting incipient damage based on said decimated enveloped digital measurement signal; and

    outputting an indication of said operating condition based on the detected incipient damage.

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