Imbalance measuring system and method

• US 4,608,650 A
• Filed: 08/09/1983
• Issued: 08/26/1986
• Est. Priority Date: 08/09/1983
• Status: Expired due to Term

• Current Assignee: Endevco Corporation (Illinois Tool Works Inc.)
• Original Assignee: Becton, Dickinson & Co
• Inventors: Kapadia, Nikul S.
• Primary Examiner(s): Lall, Parshotam S.
• Application Number:
  US06/521,725
• Time in Patent Office: 1,113 Days
• Field of Search: 364/508, 364/565, 364/566, 364/724, 364/179, 73/462, 73/468, 73/579, 73/583, 73/660
• US Class Current: 700/279
• CPC Class Codes: G01M 1/22 and converting vibrations due to imbalance into electric variables

Abstract

A vibration monitoring system analyzes tachometer signals of a rotating engine to ascertain the period of rotation from which sampling pulses at predetermined intervals can be generated. Sampled accelerometer data is processed by a nonrecursive tracking digital filter to determine peak velocity or displacement of rotating engine. In a different operating phase, apparatus determines the rotational location of the peak relative to an index or reference point on the rotating engine. The magnitude and location of the peak can be signaled for subsequent correction of the imbalance. The rotational velocity is monitored so that changes in velocity during a measurement invalidate the results and cause a repetition of the measurement cycles.

Claims

1. Apparatus to enable the balancing of the rotating component of complex machinery comprising:

(a) transducer means for detecting and singalling an imbalance condition in the rotating component;

(b) signalling means coupled to the rotating component for signalling frequency of rotation;

(c) sampling means coupled to said signlling means for generating a predetermined number of sampling pulses during each revolution of the rotating machinery;

(d) data acquisition means, coupled to said transducer means and said sampling means, operative in response to said sampling pulses for providing said predetermined number of data samples each revolution;

(e) analog to digital converting means for providing transducer signals in digital form;

(f) digital filtering means responsive to applied digitized data samples for creating signals representative of the magnitude of a parameter of imbalance of the rotating component; and

(g) storage and comparison means for recording the signals dreated in said digital filtering means for determining the signal of greatest magnitude and its time of occurrence;

wherein an imbalanced rotating component can be monitored during operation to determine the magnitude of the imbalance.

2. The apparatus of claim 1, above, further including magnitude determining means coupled to said data acquisition means for signalling the magnitude of a mass that is suitable to balance the rotating element.

3. The apparatus of claim 2, above, wherein said signalling means includes means for signalling an index location on the rotating component and further including

(e) locating means coupled to said data acquisition means, said sampling means and said signalling means for corresponding maximum imbalance representing signals to a location on the rotating component.

4. The apparatus of claim 3, above, wherein said magnitude determining means signals both the magnitude of the mass suitable to balance the rotating element and the placement of such a mass relative to the index location to achieve a balance condition.

5. In combination with transducer means to detect and signal vibration of a rotating component of a complex machine capable of generating a unique indexing signal and tachometer means for signallilng rotational frequency of the rotating component, apparatus for measuring the magnitude and location of vibration causing imbalance in the rotating machine at any of its normal operating frequencies comprising:

(a) sampling means coupled to the tachometer means for generating a predetermined number of sampling pulses per revolution of the rotating component;

(b) data acquisition means coupled to said sampling means and the transducer means, including digitizing and filter means for providing signals representative of the magnitude of imbalance caused vibration at the then current operating frequency; and

(c) position locating means including indexing means coupled to said data acquisition means and operable in response to the indexing signal for signalling the location of the point of maximum imbalance relative to an index location at the then current operating frequency;

whereby the magnitude and location of a compensating mass for correcting the imbalance condition can be determined during the normal operation of the machine at each operating frequency.

6. The apparatus of claim 5, further including storage and comparsion means coupled to said data acquisition means for storing a maximum value of imbalance magnitude, including data processing means for comparing a predetermined proportion of stored values with currently sampled values to record location information relative to a currently sampled value greater than said stored value, whereby on subsequent cycles, an average location can be derived.

7. The method of measuring and locating an imbalance in complex rotating machinery having means to signal an index location, comprising the steps of:

(a) measuring a vibration parameter during rotation at an operating frequency;

(b) filtering the measured vibration parameter to limit the measurement to a parameter at the frequency of rotation;

(c) determining the value of the filtered parameter;

(d) repeating the measuring, filtering and determining steps, signalling values greater than a predetermined percentage of a previously measured value;

(e) measuring the angular displacement from an index location at the instant of said signalled greater value during a revolution;

(f) accumulating and averaging signalled greater values over several revolutions;

(g) accumulating and averaging measured angular displacements over several revolutions;

(h) computing from averaged greater values a corresponding balancing mass magnitude which, if attached to the machinery at a selected location, determined by said accumulated, averaged angular displacements from the index mark, will substantially reduce the magnitude of the measured vibration parameter.

8. The method of claim 7 wherein said vibration parameter corresponds to velocity and wherein said predetermined percentage is 90%.

9. The method of measuring and locating an imbalance in rotating machinery having means to signal an index location, comprising the steps of:

(a) measuring the frequency of rotation;

(b) measuring a parameter related to unbalance;

(c) filtering said parameter though a nonrecursive digital tracking filter;

(d) determining and storing said parameter maximum value during an operating cycle;

(e) signalling parameter values in excess of 75% of measured maximum and the angular displacement from index mark corresponding thereto in a subsequent cycle;

(f) storing the angular dislacement quantity;

(g) repeating steps (e) and (f) for a predetermined number of samples;

(h) averaging the values of angular displacement from the index mark for the predetermined number of successive measurements;

(i) averaging successive signalled parameter values for the predetermined number of samples;

(j) corresponding said maximum average parameter value to a balancing mass magnitude;

(k) placing a balancing mass of said magnitude on the machinery at a location opposite to the measured average angular displacement from the index mark;

whereby the application of the balancing mass of the proper magnitude at the proper location substantially corrects the imbalance condition.

10. The method of claim 9 wherein said parameter is acceleration and further including the steps of integrating the measured acceleration to obtain signals representing velocity and correcting said location to account for phase shifts introduced by the measurement process and the data acquisition and processing equipment.