Abstract:
A system comprises a remotely situated plurality of sensors that sense information; a locally situated workstation that receives the information from the remotely situated plurality of sensors in the form of a set of data; and a Fast Fourier Transform (FFT) analyzer interfaced with the plurality of sensors and workstation to receive information from the plurality of sensors in the form of time domain data points, to transform the data points into a lesser number of frequency domain data points to facilitate transmission as a set of data from the plurality of sensors to the locally situated workstation. Another system comprises a remotely situated sensor that senses information; a remotely situated data acquisition system interfaced with the sensor to receive data from the sensor; a Fast Fourier Transform (FFT) analyzer interfaced with the sensor in parallel with the data acquisition system to receive information from the sensor in the form of time domain data points and to transform the data points into a lesser number of frequency domain data points to facilitate transmission; and a locally situated workstation that receives the data from the data acquisition system, that receives the frequency domain data points from the FFT analyzer and that controls the sensor via input in response to the data and data points.A method comprises remotely monitoring an operating test object with a plurality of sensors to generate time domain data points; remotely transforming the time domain data points to frequency domain data points with a Fast Fourier Transform (FFT) analyzer; and transmitting the frequency domain data points to a local workstation.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a system and method for remotely acquiring and selecting data for monitoring and analysis.  
           [0002]    A remote data acquisition system can be used to acquire sensor data from a sensor attached to a test object. Transmission of sensor data from the remote data acquisition system is limited by bandwidth and speed of the communications link to the central control system. Increased separation of the remote data acquisition system from the central control system exacerbates the transmission bandwidth and speed problems.  
           [0003]    Another problem is that a remote data acquisition system may be located where only low speed analog phone line transmission is available. This further slows transmission of remotely acquired data.  
           [0004]    The problem of remote data transmission is more severe in the case of vibration data transmission. Generally, vibration data is sampled at at least twice a desired frequency. For example, if the desired frequency is 50 kHz, then the sampling frequency is at least 100 kHz. If the data acquisition system is sampling data from 200 sensors, then the data acquisition system is acquiring the data at a rate of at least 20 million data points per second. Sending data at this rate across the communication link may not be possible.  
           [0005]    Additionally, it would be advantageous for an operator working at a remote workstation to be able to communicate with a sensor central control system. An operator may desire to both view sensor data stored on a central control system and also control operation of the remote sensor.  
           [0006]    A system and method are needed to transmit large amounts of sampling data. Additionally, a system and method are needed that permit communication from a remote workstation.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    The present invention provides such a system and method. The system includes a FFT (Fast Fourier Transform) analyzer located at a remote location from a central control system. The method permits the compression of large amounts of data to facilitate transmission. The invention provides for back and forth communication between remote and local system architecture.  
           [0008]    In the invention, a system comprises a remotely situated plurality of sensors that sense information; a locally situated workstation that receives the information from the remotely situated plurality of sensors in the form of a set of data; and a Fast Fourier Transform (FFT) analyzer interfaced with the plurality of sensors and workstation to receive information from the plurality of sensors in the form of time domain data points, to transform the data points into a lesser number of frequency domain data points to facilitate transmission as a set of data from the plurality of sensors to the locally situated workstation.  
           [0009]    In an embodiment, a system comprises a remotely situated sensor that senses information; a remotely situated data acquisition system interfaced with the sensor to receive data from the sensor; a Fast Fourier Transform (FFT) analyzer interfaced with the sensor in parallel with the data acquisition system to receive information from the sensor in the form of time domain data points and to transform the data points into a lesser number of frequency domain data points to facilitate transmission; and a locally situated workstation that receives the data from the data acquisition system, that receives the frequency domain data points from the FFT analyzer and that controls the sensor via input in response to the data and data points.  
           [0010]    In another embodiment, a system comprises a remotely situated plurality of sensors that sense information; a data acquisition system for acquiring digitized sensor signals from the plurality of sensors; an interface device that converts the digitized sensor signals into an output data signal transmission stream; a transmission apparatus that transmits the output data signal transmission stream from the interface device; a local interface device situated remote from the sensors that receives the output data signal transmission stream from the transmission apparatus and converts the output data signal transmission stream into a digital central control system data input; a central control system that receives the digital central control system data input and sends the data input as a set of central processed data; a central processing transmission apparatus that relays the sent set of central processed data; a locally situated workstation that receives the sent set of central processed data from the central processing transmission apparatus; and a Fast Fourier Transform (FFT) analyzer interfaced with the plurality of sensors and workstation to receive information from the plurality of sensors in the form of time domain data points, to transform the data points into a lesser number of frequency domain data points that can be digitized by the interface device to facilitate transmission as a set of output data signal transmission stream from the plurality of sensors to the transmission apparatus.  
           [0011]    Additionally, the invention is a method comprising remotely monitoring an operating test object with a plurality of sensors to generate time domain data points; remotely transforming the time domain data points to frequency domain data points with a Fast Fourier Transform (FFT) analyzer; and transmitting the frequency domain data points to a local workstation.  
           [0012]    In another embodiment of the invention, a method comprises remotely monitoring an operating test object with a plurality of sensors to generate sensor signals; remotely digitizing the sensor signals; remotely converting the digitized sensor signals into an output data signal transmission stream; transmitting the output data signal transmission stream to a local interface device; converting the output data signal transmission stream at the local interface device into a digital central control system data input; sending the set of the central transmission processed data through a central processing transmission apparatus to a workstation; displaying the set of central transmission processed data at a workstation display wherein an operator views the processed data; selecting a sensor and inputting a selected sensor command according to the displayed set of central transmission processed data; transmitting the selected sensor command through the central processing transmission apparatus to a remote controlled switching apparatus; and selecting a sensor according to the selected sensor command in the remote controlled switching apparatus. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The following detailed description of the invention is presented in connection with the accompanying drawings wherein:  
         [0014]    [0014]FIG. 1 is a schematic view of a remote data acquisition, monitoring and control system;  
         [0015]    [0015]FIG. 2 illustrates a time domain display;  
         [0016]    [0016]FIG. 3 illustrates a frequency domain spectral display including an amplitude versus frequency plot;  
         [0017]    [0017]FIG. 4 is a spectral display of FIG. 3 further including a plurality of preselected harmonic peak limit levels;  
         [0018]    [0018]FIG. 5 illustrates a testing condition display wherein harmonic peak levels have exceeded at least one selected harmonic peak threshold level;  
         [0019]    [0019]FIG. 6 illustrates an octave band FFT display; and  
         [0020]    [0020]FIG. 7 illustrates a waterfall FFT display. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]    According to an aspect of the invention, a remote data acquisition system acquires sensor signals from a plurality of sensors. In this specification, the term “remote” means non-integrated with and “off site” from local system architecture. The system includes a remote controlled switching apparatus and an FFT apparatus located near the plurality of sensors. An operator can be seated at a workstation located at a distance from the remote controlled switching apparatus and FFT apparatus. The operator can remotely control the switching apparatus and the FFT apparatus display. In operation, the operator enters a selected sensor command into the workstation to select a sensor from the plurality of sensors. A selected sensor signal is transmitted to the FFT that transforms a number of time domain data points into a lesser number of frequency domain data points to facilitate transmission to the workstation and that can process the selected sensor signal into an FFT display.  
         [0022]    These and other features will become apparent from the drawings and following detailed discussion, which by way of example without limitation describe preferred embodiments of the invention. In the drawings, corresponding reference characters indicate corresponding parts throughout the several figures.  
         [0023]    In the drawings, FIG. 1 is a schematic view of a remote data acquisition, monitoring and control system  10 . The remote data acquisition, monitoring and control system  10  includes a plurality of sensors  12 A- 12 F, a remote data acquisition system  14 , a remote interface device  16 , a transmission apparatus  18 , a local interface device  20 , a central control system  22 , a central processing transmission apparatus  24 , a workstation  26 , a remote controlled switching apparatus  28  and a FFT (Fast Fourier Transform) apparatus  30 .  
         [0024]    The plurality of sensors  12 A- 12 F is attached or is located in the proximity of a test object  32 . The test object  32  includes any suitable object such as a steam turbine, a gas turbine, a generator, a heat recovery boiler, an aircraft engine, a gear unit or the like. The sensors  12 A- 12 F can be vibration sensors, temperature sensors, once per revolution sensors, strain measurement sensors, time code generators, voltage sensors, current sensors, watt meters, VAR meters, speed meters, pressure sensors, microphones, cameras or the like. A vibration sensor can comprise any suitable device such as an accelerometer, a proximity probe, a fiber optic accelerometer or the like. A temperature sensor can comprise any suitable sensor such as a thermocouple, a thermistor, an RTD, an infrared sensor or the like. A once per revolution sensor can comprise any suitable sensor such as a key phaser, a proximity probe or the like. A strain measurement sensor can comprise any suitable sensor such as a strain gauge, thermal strain system or the like.  
         [0025]    Sensors  12 A- 12 F include a signal conditioners  34 A- 34 F to provide a signal from each sensor  12 A- 12 F respectively. Each sensor  12 A- 12 F is connected by a lead wire  36 A- 36 F, respectively, to an analog-to-digital converter  38  of the remote data acquisition system  14 . The lead wires  36 A- 36 F carry a plurality of sensor signals  40 A- 40 F, respectively to the analog-to-digital converter  38 . The analog-to-digital converter  38  converts analog sensor signals  40 A- 40 F into a digitized sensor data signals  42 A- 42 F.  
         [0026]    The remote data acquisition system  14  includes a remote data acquisition system processing device  46  and a remote data acquisition storage device  44 . The remote data acquisition system processing device  46  or the data acquisition storage device  44  or both comprise any suitable device such as a. processor, microprocessor, computer, personal computer, controller or the like. The remote data acquisition system processing device  46  acquires digitized data signals  42 A- 42 F and the remote data acquisition storage device  44  can store the digitized sensor data signals  42 A- 42 F.  
         [0027]    A conduit  48  carries digitized sensor data signals  42 A- 42 F and analyzed data signals from the remote data acquisition system  14  to a remote interface device  16 . The remote interface device converts each digitized sensor data signal  42 A- 42 F and analyzed data signals into a remote output data signal transmission stream  50 . The transmission apparatus  18  carries the remote output data signal transmission stream  50  from the remote interface device  16  to the local interface device  20 . Conduit  48  is represented as structure in FIG. 1. However, the transmission apparatus  18  can comprise any suitable transmission link such as an internet connection, a digital subscriber line (DSL) connection, an interface bus connection, a wireless connection, a satellite connection or the like.  
         [0028]    The local interface device  20  receives the remote output data signal transmission stream  50  and converts the remote output data signal transmission stream  50  into a digital central control system data input  52 . A conduit  54  carries the digital central control system data input  52  from the local interface device  20  to the central control system  22 . The central control system  22  includes a central processing system  56 , a central storage device  58  and a central output device  60 . The central processing system  56 , the central storage device  58  or both can comprise any suitable device such as a processor, microprocessor, computer, personal computer, controller or the like. The central processing system  56  analyzes the digital central control system data input  52  and generates a set of central processed data  62 . The set of central processed data  62  includes data from each signal sensor  12 A- 12 F. The central storage device  58  can store the digital ¢ central control system data input  52  and the set of central processed data  62 . The central output device  60  sends the set of central processed data  62  through the central processing transmission apparatus  24  to workstation  26 . The central processing transmission apparatus  24  can include any suitable carrier such as an internet connection, a Local Area Network, a cable connection, a general-purpose interface bus (GPIP), a wireless connection, an ethernet connection or the like. The central output device  60  can transmit the set of central processed data  62  to additional workstations, for example, to workstation  26 A.  
         [0029]    Workstation  26  receives the set of central processed data  62 . The workstation  26  includes a display device  64 , a workstation processing device  66 , a workstation storage device  68 , a workstation output device  70 , a workstation input device  72 , and a workstation audio monitoring system  74 . The workstation processing device  66  can comprise any suitable device such as a computer, personal computer, laptop computer or the like. The workstation storage device  68  can store the set of central processed data  62 . The workstation storage device  68  can comprise any suitable device such as a hard disk, a writable CD, a flexible disk or the like. The workstation display device  64  comprises a suitable device such as a screen, LCD display, large screen display or the like. The workstation  26  output device  70  comprises a suitable device such as a plotter, a color printer, a printer, an e-mail message system or the like. The workstation audio monitoring system  74  comprises a suitable device such as a speaker  78 , surround sound system, earphones or the like. The workstation input device  72  comprises a suitable device such as a keyboard  80 , a mouse  82 , a wireless mouse  84  or the like.  
         [0030]    In the embodiment shown, central control system  22  includes an alarm apparatus  84  that generates an alarm trigger signal  86  whenever the digitized sensor data signal  42  exceeds a preset alarm level. The central processing transmission apparatus  24  carries the alarm trigger signal  86  from the central processing system  56  to the workstation  26 . An audio alarm system  88  in the workstation  26  transmits an audible and/or visual alarm to alert an operator  76 . The operator hears the audible alarm through the workstation audio monitoring system  74  and sees an alert message on the workstation display device  64 . Additionally, the operator  76  can observe sensor signal  40  exceeding a preset threshold alarm level.  
         [0031]    The operator  76  uses the workstation input device  72  to input a selected sensor command  90  to select a sensor signal  40 , for example  40 E, from the plurality of sensors  12 A- 12 F. The selected sensor command  90  can be transmitted in any suitable format such as a general purpose interface bus (GPIB). The selected sensor command  90  is transmitted from the workstation  26  through the central processing transmission apparatus  24  to the central control system  22 . From the central control system  22  the selected sensor command  90  travels through the local interface device  20 , through the transmission apparatus  18 , through the remote interface device  16  and through a control cable  92  to the remote controlled switching apparatus  28 . The remote controlled switching apparatus  28  receives the selected sensor command  90  and switches to the selected sensor signal  40 , for example,  40 E. In this example, sensor  12 E is the operator selected sensor. The sensor signal  40 E is connected through the remote controlled switching apparatus  28 , through a conduit  100  to the FFT apparatus  30 . The remote controlled switching apparatus  28  is able to individually select any one of the sensor signals  40 A- 40 F. Thus, the operator  76  can select any one of the sensor signals  40 A- 40 F to be sent to FFT apparatus  30 .  
         [0032]    The FFT apparatus  30  includes an FFT processing device  102  and an FFT memory device  104 . The FFT processing device  102  comprises a suitable device such as a processor, microprocessor, personal computer, controller or the like. The FFT processing device  102  performs a Fourier transform on the sensor signal (in this example  40 E). The Fourier transform changes the sensor signal  40 E from a time domain display to a frequency domain display.  
         [0033]    [0033]FIG. 2 illustrates a time domain display  110  that displays an amplitude  106  of the signal versus a time axis  108 . Typically, vibrational data is sampled at least twice a desired frequency. For example if 50 kHz is a desired frequency, then the sampling frequency is at least 100 kHz. Data acquisition system  14  may not be capable of a transmission rate for sending a 100 kHz sampled frequency through remote interface device  14  to the workstation  26 . In such an instance, the FFT advantageously transforms the time domain sensor  40 E signal to a transmittable frequency domain signal.  
         [0034]    [0034]FIG. 3 illustrates a type of FFT display  130  called a spectral frequency domain display  130 A. In this embodiment, FFT apparatus  30  transforms a time domain display  110  to a spectral frequency domain display  130 A. The spectral frequency domain display  130 A includes a spectral amplitude  114  versus frequency  116  display. The spectral frequency domain display  130 A, shows resonant peaks  118 A- 118 E. The frequency and amplitude of these resonant peaks  118 A- 118 E represents useful, easy to understand data to operator  76 .  
         [0035]    The spectral frequency domain display  130 A can be averaged to reduce any random noise components and to smooth the spectral frequency domain display. The spectral frequency domain display  130 A can be averaged with any suitable number of averages such as a 16, 32 or 64. The frequency domain display  130 A can be displayed in as few as 100 to 400 points of data. These 100 to 400 points or lines of data can be easily and quickly transmitted from an FFT output device  105  through a conduit  124 , through the remote interface device  16 , through transmission apparatus  18 , through local interface device  20 , through conduit  54 , through central control system  22 , through the central processing transmission apparatus  24  and to the workstation  26  (FIG. 1).  
         [0036]    Operator  76  can use workstation input device  72  to input an FFT control command  122  into workstation  26 . The FFT command  122  is transmitted to the FFT apparatus  30  through central processing transmission apparatus  24 , central control system  22 , local interface device  20 , transmission apparatus  18 , remote interface device  16 , and conduit  124  to the FFT apparatus  30 .  
         [0037]    The FFT control command  122  represents a suitable carrier such as a GPIB. Generally, the FFT control command  122  allows operator  76  to operate the FFT apparatus  30 . The control command  122  allows operator  76  to select FFT apparatus  30  functions and FFT displays  130  including a cursor  120  control, spectrum averaging, an octave display  130 B and a waterfall display  130 C. Operator  76  can view the FFT display  130  on display device  64  of workstation  26 . FIG. 3 illustrates an example of the operator  76  controlling the cursor  120  to be placed on resonant peak  118 A. Then the operator can read the amplitude  114  and frequency  116  of the resonant peak  118 A.  
         [0038]    [0038]FIG. 4 shows the spectral display  130 A of FIG. 3 including a plurality of preselected harmonic peak limit levels  132 A- 132 K. Additionally, FIG. 4 illustrates a first harmonic peak  134 A, a second harmonic peak  134 B, a third harmonic peak  134 C, a forth harmonic peak  134 D and a fifth harmonic peak  134 E.  
         [0039]    [0039]FIG. 5 shows a spectral display  130 D illustrating a circumstance where there have been vibrational changes in test object  32 . A comparison of the spectral display  130 A with the display  130 D, shows that resonant peak levels  118 A- 118 K have increased in amplitude  114 . Resonant peak levels  118 A- 118 H have exceeded preselected harmonic threshold levels  132 A- 132 H. In this instance, an operator  76  can recommend that testing be stopped. The test object  32  can then be inspected and repaired before additional damage can occur.  
         [0040]    A comparison of the spectral display  130 A (FIGS. 3 and 4) with  130 D (FIG. 5), shows an increase in number of harmonic peaks  134 A- 134 K. Spectral display  130 A shows 5 harmonic peaks  134 A- 134 E, while spectral display  130 D shows 11 harmonic peaks  134 A- 134 K. In this instance, an operator  76  can determine that a test should be terminated. For example, if a preselected threshold number of harmonic peaks is 7, an operator  76  will recommend termination of a test when the preselected maximum number of harmonic peaks  134 A- 134 K has been exceeded. The test object  32  can then be inspected and repaired before additional damage can occur.  
         [0041]    [0041]FIG. 6 illustrates another remotely selected FFT display  130 . The FFT display  130  includes octave band display  130 B provided by the FFT apparatus  30 . The octave band display  130 B includes a plot of amplitude  114  versus frequency  116  for a plurality of octave bands  136 A- 136 I. The frequency range specified by each octave band falls between two frequencies that have a ratio of 2:1. Typical center frequencies of octave bands  136 A- 136 I can comprise, for example, 31.5, 63, 125, 250, 500, 1000, 2000, 4000, and 8000 Hz. Fractional octave band analysis subdivides octave bands  136 A- 136 I. A ⅓ octave display comprises three bands per octave, a ⅙ octave display comprises 6 bands per octave, a {fraction (1/12)} octave display comprises 12 bands per octave, and a {fraction (1/24)} octave display comprises 24 bands per octave.  
         [0042]    [0042]FIG. 7 illustrates another remotely selected FFT display  130 . In this figure, FFT display  130  includes waterfall display  130 C, which includes a 3 dimensional graph showing a plurality of spectrum plots  130 E- 130 H. Each spectrum plot  130 E- 130 H comprises a plot of amplitude  114  versus frequency  116  in two directions. Additionally, each spectrum plot  130 E- 130 H is shown as a function of time  140  in a third direction.  
         [0043]    In the instance of FIG. 7, an operator  76  can selectively control sensor signal  40 A- 40 F that is applied to the FFT apparatus  30 , and additionally, the operator  76  can remotely control the FFT apparatus  30  and view the FFT display  130  on the workstation display device  64 . The operator  76  can use the workstation output device  70  to plot a hard copy of the FFT display  130  or can output the FFT display  130  by e-mail to another location.  
         [0044]    Additionally, the operator  76  can view the test object  32  with a sensor  12  that includes a camera. The camera can transmit an image of test object  32  through the remote data acquisition system  14  to the workstation display device  64  of workstation  26 . The camera can comprise any suitable device such as a web cam, video cam, digital camera and the like. A camera image can be transmitted from the remote data acquisition system  14  to the workstation  26  in any suitable format such as a streaming video, a snap shot or the like.  
         [0045]    In another illustration, an operator  76  listens to a sensor signal  40  using a workstation audio monitoring system  74 . For example, if sensor  12 F is a microphone, the operator can monitor the test object  32  for abnormal noises such as a knocking or buzzing noise. The audio signal  142  can be transmitted from the sensor  12 F to the workstation  26  in any suitable format such as real audio, MP3 or the like.  
         [0046]    While preferred embodiments of the invention have been described, the present invention is capable of variation and modification and therefore should not be limited to the precise details of the Examples. The invention includes changes and alterations that fall within the purview of the following claims.