Abstract:
An instrument for performing order analysis on a rotational machine. An input module receives periodic motion data, and machine characteristic data that is associated by time with the periodic motion data. A processor module receives the periodic motion data and the machine characteristic data, applies a Goertzel module to the periodic motion data and the machine characteristic data, and thereby creates an order data set comprising magnitude of machine characteristic data versus order of normalized periodic motion data.

Description:
FIELD 
       [0001]    This invention relates to the field of machine health, protection, and prediction. More particularly, this invention relates to order analysis for detecting machine condition. 
       INTRODUCTION 
       [0002]    Order analysis is used to analyze information, such as sound and vibration signals, that is gathered from equipment that has periodic movement. This includes rotating machine, such as turbines, motors, pumps, compressors, and so forth. It also includes machines repetitively move in some other periodically repeating manner, but which is not rotational, such as a box-folding machine. All such are generally referred to herein as machines. 
         [0003]    An “order,” as used in the term “order analysis,” is the frequency at which the machine is making its periodically repeating motion, such as rotating, normalized to a value of one. Thus, in one embodiment, the first order is merely the periodic motion, and additional orders are multiples of the periodic motion. The various orders are thus the harmonics of the periodic motion. Although it has been explained that these concepts apply to more than just rotating machines, the various descriptions provided herein will be given in regard to rotating machines, so as to not unduly encumber the language. 
         [0004]    Generally speaking then, order analysis is useful to determine the relationships that exist between the periodic motion and machine information, such as sound and vibration. Using order analysis, one can identify and isolate such sound and vibration patterns, and thereby determine a status of individual components of the machine. 
         [0005]    Many mechanical characteristics of machinery change with the periodic motion of the machine. Some mechanical conditions, such as resonance, can typically only be observed as the periodic motion approaches or passes the resonant speed. Thus, machine sound and vibration tests usually require a run-up or run-down test. Order analysis techniques enable one to analyze sound and vibration signals not only when the machine is operating at a steady periodic motion, but also when the periodic motion changes over time, by continually normalizing the periodic motion of the machine. 
         [0006]    Order analysis can be used to determine both the magnitude and phase of the sound and vibration data, for not only the base frequency but also the harmonics or higher orders of the signal. This information is useful to determine machine state. For example, an increase in the periodic motion frequency magnitude indicates an unbalance situation. Harmonics of the periodic motion frequency indicate other errors, such as misalignment. 
         [0007]    What is needed, therefore, is a system that more information in regard to the issues described above, at least in part. 
       SUMMARY 
       [0008]    The above and other needs are met by an instrument for performing order analysis on a machine. An input module receives periodic motion data, and machine characteristic data that is associated by time with the periodic motion data. A processor module receives the periodic motion data and the machine characteristic data, applies a Goertzel module to the periodic motion data and the machine characteristic data, and thereby creates an order data set comprising magnitude of machine characteristic data versus order of normalized periodic motion data. 
         [0009]    In various embodiments, the machine characteristic data includes vibrational data. In some embodiments, the machine characteristic data includes sound data. In some embodiments, the order data set further includes phase of machine characteristic data. Some embodiments include a display for presenting a representation of the order data set. In some embodiments, the representation of the order data set includes a graph of magnitude of machine characteristic data versus normalized periodic motion data. 
         [0010]    According to another aspect of the invention there is described a method for performing order analysis on a machine. Periodic motion data is received, along with machine characteristic data that is associated by time with the periodic motion data. A Goertzel module is applied to the periodic motion data and the machine characteristic data, thereby creating an order data set comprising magnitude of machine characteristic data versus order of normalized periodic motion data. 
         [0011]    According to yet another aspect of the invention there is described a non-transient, computer-readable medium containing a program for enabling a computer to perform order analysis on a rotational machine, by causing a processor of the computer to perform the following steps. Periodic motion data is received, along with machine characteristic data that is associated by time with the periodic motion data. A Goertzel module is applied to the periodic motion data and the machine characteristic data, thereby creating an order data set comprising magnitude of machine characteristic data versus order of normalized periodic motion data. 
     
    
     
       DRAWINGS 
         [0012]    Further advantages of the invention are apparent by reference to the detailed description when considered in conjunction with the figures, which are not to scale so as to more clearly show the details, wherein like reference numbers indicate like elements throughout the several views, and wherein: 
           [0013]      FIG. 1  is a functional block diagram of an order analysis system according to an embodiment of the present invention. 
           [0014]      FIG. 2  is a functional block diagram of a Goertzel module according to an embodiment of the present invention. 
           [0015]      FIG. 3  is a functional block diagram of a comb filter module according to an embodiment of the present invention. 
           [0016]      FIG. 4  is a graph of a frequency selective setting for the comb filter module according to an embodiment of the present invention. 
           [0017]      FIG. 5  is a graph of a harmonic bandwidth selective setting for the comb filter module according to an embodiment of the present invention. 
           [0018]      FIG. 6  is a graph of a time domain depiction and a frequency domain depiction of the application of a Hanning filter module according to an embodiment of the present invention. 
           [0019]      FIG. 7  is a graph of the magnitude and phase of an order of a periodic motion data set, with regions for alert and danger sections according to an embodiment of the present invention. 
       
    
    
     DESCRIPTION 
       [0020]    With reference now to  FIG. 1  there is depicted a functional block diagram of an order analysis system  100  according to an embodiment of the present invention, including a speed detection module  102 , a data sensing module  104 , an input  110 , a memory  112 , a measurement module  106 , an alarm module  108 , and a processor  114 . 
         [0021]    As used herein, the term “module” includes both hardware and software components. In some embodiments, the module is a custom piece of hardware with software embodied in firmware that is either not changeable or not readily changeable. In other embodiments the module is implemented predominantly in software that runs on general purpose computing system hardware. Some modules, as described below, always include special purpose hardware, such as sensors of various kinds, which are not typically included in general purpose computing system hardware. 
         [0022]    As introduced above, in some embodiments the order analysis system  100  is implemented in customized hardware. In alternate embodiments, the order analysis system  100  is implemented primarily in software that runs on a general purpose computing platform, with specialized equipment, as needed, to provide the speed and data sensing information. 
         [0023]    The speed detection module  102  uses speed information given by an external input for speed evaluation. Some embodiments include an external trigger input or a direct sensor input, such as a tachometer. In some embodiments the speed information is received as a digital signal, and in other embodiments the speed information is received as an analog signal and converted into a digital signal, such as by the speed detection module  102 . 
         [0024]    The data acquisition module  104  samples data from a sensor or raw signal sources, such as for sound data or vibration data. In some embodiments it converts an analog signal to a digital signal, if the data is not already provided in the digital domain. Subsequent processing of the sampled data is then accomplished in the digital domain. In some embodiments, preprocessing of some sort is performed on the data signal, as described in more detail hereafter. 
         [0025]    The speed and machine data are received such as through an input  110 , which in various embodiments takes the form of one or more of a USB, serial, parallel, or proprietary input. The data received from the periodic motion module  102  and the machine data module  104  is stored in a memory  112 , at least temporarily. For example, if post processing is to be performed on the data, then the memory  112  could hold the data for quite some time. However, if real time analysis is to be performed on the data, then it might just be buffered in the memory  112 . 
         [0026]    The measurement module  106  receives the periodic motion data  110  from the memory  112 , or in some embodiments, directly through the input  110  from the speed module  102  and the machine data module  104 . The measurement module  106  uses the periodic motion information  110  (which could be rotation) to perform a selective frequency extraction from the measured vibration input signal  112 . The different components (magnitude and phase) of the machine data signal  112  can be monitored directly or combined in various ways to produce new information. 
         [0027]    The monitoring and alarming module  108  monitors the output of the measurement module  106 , and compares the output to various standards and limits. When any of the standards or limits are violated, the alarm module  108  brings notice of such to a system operator, or otherwise outputs a signal with an indication of the particular violation, so that action can be taken in regard to the violation. In some embodiments the action is automatically implemented, and in other embodiments the action is manually implemented. 
         [0028]    The system  100  is generally under the control of the processor  114 . Also present in some embodiments of the system  100  is a user interface  116 , and a communication module  118 , such a network communication interface for communication between the system  100  and other computing systems. 
         [0029]    With reference now to  FIG. 2 , there is depicted a more detailed embodiment of the measuring module  106 , which is used to describe the signal processing that in one embodiment is used to detect the amplitudes and phases of the periodic motion frequencies and its harmonics and sub harmonics. 
         [0030]    The embodiment depicted in  FIG. 2  implements a Goertzel module. The specific module depicted in  FIG. 2  is a sliding or modified Goertzel module. In the present embodiment, the parameter settings of the Goertzel module  106  are continuously updated so as to adapt to new periodic motion frequencies, which is especially beneficial during machine ramp up and ramp down. 
         [0031]    The Goertzel module  106  as depicted in  FIG. 2  includes a comb filter  202 , a plurality of resonator blocks  204 , and a time domain windowing module  206 . In some embodiments, the comb filter  202  is implemented as depicted in  FIG. 3 . The comb filter  202  is applied in the time domain. The resonator blocks  204  then convert the time signal to the frequency domain, and the windowing  206  is performed in the frequency domain, instead of doing the windowing filtering in the time domain. 
         [0032]    In some embodiments the filter  202  has a transfer function of: 
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         [0033]    The filter  202  is not present in some embodiments, but in other embodiments it is set to be very frequency selective, as depicted in  FIG. 4 . In other embodiments the filter  202  is set so as to provide a specific bandwidth around the harmonics to be detected, as depicted in  FIG. 5 . Various embodiments according to the present invention use different types of comb filter  202  according to the needs of the measurement. For highly selective frequency extraction the comb filter  202 , in some embodiments, is set to the notch characteristic as depicted in  FIG. 4 . For band limited extraction with a larger number of windowing filters for sidebands, the comb filter  202 , in some embodiments, is set for band limiting, as depicted in  FIG. 5 . 
         [0034]    As depicted in  FIG. 2 , each resonator block  204  extracts a single frequency bin from an input signal coming from the comb filter  202 , if present. The resonator blocks  204  provide periodic motion frequency functionality, which is the starting point of an order analysis. The number of resonator blocks  204  needed for a single harmonic detection depends, in some embodiments, on the number of averages in frequency domain to be executed. In the embodiment as depicted in  FIG. 2 , five resonator blocks  204  are shown, but in other embodiments a different number of resonator blocks  204  could be implemented. After each measurement (where the number of measurement samples is configurable in some embodiments), new coefficients are calculated for the resonator blocks  204 . At any time that new data is available, the evaluation output is synchronized to the measurement cycles. 
         [0035]    In some embodiments, the windowing functionality  206  is accomplished in the frequency domain by cosine filters, such as the Hanning filter depicted in  FIG. 6 . Embodiments of the present invention, use the windowing function  206  for weighing the output from some number of resonator blocks  204 . This includes sideband bins in the result of the order analysis. For high speed gradients, this architecture helps to assure that the input data is in the observer range of the Goertzel module  106 . 
         [0036]    Various embodiments according to the present invention use a single Goertzel module  106  for each speed base or harmonic frequency part extraction. In such embodiments, each Goertzel module  106  can be independently configured or configured as a group. 
         [0037]    Thus, various embodiments of the present invention employ a Goertzel module  106  in the frequency domain for order analysis, such as in a protection and prediction system for rotating machines. By using the Goertzel module  106 , the resonator  204 , comb filter  202 , and window  206  parameters can be updated continuously to support fast and precise magnitude and phase information. Further, fast Fourier transforms use block processing, whereas a Goertzel module  106  only needs a flexible delay line, if a comb filter  202  is used. 
         [0038]    With reference now to  FIG. 7  there is depicted a graph of the magnitude and phase of an order of a periodic motion data set, with regions for alert and danger sections according to an embodiment of the present invention. 
         [0039]    The foregoing description of embodiments for this invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments are chosen and described in an effort to provide illustrations of the principles of the invention and its practical application, and to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.