Apparatus and method for analysing the condition of a machine having a rotating part
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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Abstract
An apparatus for analyzing the condition of a machine having a rotating part, includes:
- a first sensor for generating an analogue electric measurement signal;
- an analogue-to-digital converter for sampling the analogue electric measurement signal at an initial sampling frequency to generate a digital measurement data signal in response to the received analogue electric measurement signal;
- a device for generating a position signal having a sequence of position signal values for indicating momentary rotational positions of the rotating part; and
- a speed value generator for recording a time sequence of the position signal values such that there are angular distances and corresponding durations between at least three consecutive position signals, wherein
- the speed value generator establishes at least two momentary speed values based on the angular distances and corresponding durations, and
- further momentary speed values for the rotating part are established by interpolation between the two momentary speed values.
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Citations
12 Claims
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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:
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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, and a 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. 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:
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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; 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; 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; generating a value indicative of an acceleration based on a difference between said second momentary speed value and said first momentary speed value; generating, by interpolation, a plurality of interpolated momentary speed values indicative of momentary speeds of rotation based on; said first momentary speed value, said value indicative of the acceleration, and a plurality of time values based on said first sampling frequency; associating at least one of the plurality of interpolated momentary speed values with at least one of the corresponding recorded first time sequence of measurement sample values; decimating said first time sequence of recorded measurement sample values based on said association of the at least one of the plurality of interpolated momentary 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. - View Dependent Claims (11, 12)
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Specification