Removal of effects of asymptotically decaying DC bias from vibration waveform

A computer implemented method for processing time waveform machine vibration data that are indicative of operational characteristics of a machine, comprising:

• (a) accessing the time waveform machine vibration data from a memory or storage device, wherein the time waveform machine vibration data were measured on the machine over a period of time having a begin time and an end time;
• (b) fitting a polynomial or exponential equation to the time waveform machine vibration data;
• (c) calculating an asymptotically decaying DC bias component in the time waveform machine vibration data using the polynomial or exponential equation fitted in step (b);
• (d) subtracting the asymptotically decaying DC bias component from the time waveform machine vibration data;
• (e) performing a Fast Fourier Transform on the time waveform machine vibration data to generate a vibration spectrum that is devoid of spurious low frequency components that would otherwise be present in the vibration spectrum if the asymptotically decaying DC bias component had not been subtracted from the time waveform machine vibration data, which spurious low frequency components would be subject to misinterpretation by a technician as problems with the machine;
• and
• (f) displaying the vibration spectrum that is devoid of spurious low frequency components on a screen of a user interface device for viewing by the technician.

A computer implemented process for operating on time waveform machine vibration data that are indicative of operational characteristics of a machine, comprising:

• accessing the time waveform machine vibration data from a memory or storage device, wherein the time waveform machine vibration data were measured on a machine over a period of time having a begin time and an end time;
• selecting either a first method or a second method for determining an asymptotically decaying DC bias component in the time waveform vibration data, wherein the first method comprises:
• (a) determining an integer number M of waveform samples to be averaged;
• (b) deriving the asymptotically decaying DC bias component in the time waveform machine vibration data using a moving average of the M number of waveform samples;
• and
• (c) extrapolating the asymptotically decaying DC bias component from the begin time of the waveform back to an earlier time and from the end time of the waveform forward to a later time,
• and wherein the second method comprises:
• (d) fitting a polynomial or exponential equation to the time waveform machine vibration data;
• and
• (e) calculating the asymptotically decaying DC bias component using the polynomial or exponential equation fitted in step (d),
• performing either the first method or the second method to determine the asymptotically decaying DC bias component;
• subtracting the asymptotically decaying DC bias component from the time waveform machine vibration data;
• and
• performing a Fast Fourier Transform on the time waveform machine vibration data to generate a vibration spectrum that is devoid of spurious low frequency components that would otherwise be present in the vibration spectrum if the asymptotically decaying DC bias component had not been subtracted from the time waveform machine vibration data, which spurious low frequency components would be subject to misinterpretation by a technician as problems with the machine;
• and
• displaying the vibration spectrum that is devoid of spurious low frequency components on a screen of a user interface device for viewing by the technician.