Abstract:
A vehicle noise, vibration and harshness analysis tool according to the present invention comprises at least one sensor, each sensing a vibration or noise and generating a signal at a frequency related to the vibration or noise. A communication link with a vehicle is included to transmit data regarding the vehicle. A microprocessor system receives the signals generated by said at least one sensor and receives the vehicle data over said communication link. The microprocessor system conducts an analysis of the received sensor signals and vehicle data and identifies a vehicle component that is likely causing a vibration or noise. The microprocessor system also identifies the possible problems with the identified vehicle component. A user interface is also included with a display. The microprocessor system causes the display to list the likely vehicle components causing the vibration or noise and the possible problems with the components. The list of likely components and causes helps the technician quickly isolate and remedy the cause of the vibration or noise. The invention also discloses methods for balancing a driveshaft using analyzers according to the invention.

Description:
[0001]    This application claims the benefit of provisional application Ser. No. 60/343,798 to Calkins, which was filed on Dec. 27, 2001, but was erroneously given a filing date of Oct. 27, 2001 by the receiving office of the Patent and Trademark office. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates to vehicle testers and more particularly to a hand held noise, vibration and harshness tester for vehicles.  
           [0004]    2. Description of the Related Art  
           [0005]    Noise, vibration and harshness concerns are one of the top “No Trouble Found” (NTF) anomalies in the dealer and independent service environment. In many instances, a vehicle is brought in with noise and vibration complaints but using conventional means the dealership is unable to diagnose the cause. After an NTF diagnosis, the vehicle is returned to the owner without addressing the problem. The vehicle owner will often return the vehicle for additional service complaining of continued noise, vibration or harshness conditions. These returns for service can lead to customer dissatisfaction and increased dealer service costs.  
           [0006]    Various vibration analyzers have been developed for use with operating machinery to help detect machine fault conditions. For example, U.S. Pat. No. 9,965,819 to Piety, discloses a portable data collector and analyzer having multiple paths for performing multiple processing functions. The data collector has a sensor that is placed against a vibrating machine and creates a sensor signal that represents a measured property of an operating machine. The sensor signal is simultaneously sent to at least two processor channels that are connected in parallel, with each processor capable of performing different types of signal processing. The parallel processor channels work independently of each other to obtain results corresponding to a number of different tests. The data collector&#39;s parallel paths reduce the amount of time required to perform periodic maintenance surveys.  
           [0007]    Vibration analyzers have also been developed to test for vibrations in vehicle drivelines. For example, U.S. Pat. No. 5,955,674, to McGovern, discloses a heavy duty truck diagnostic vibration analyzing tool for measuring and characterizing the torsional vibration of a transmission output shaft in the truck&#39;s driveline. An electronic control unit and speed sensor cooperate to measure speed fluctuations occurring between the passing teeth of a rotating gear. These time measurements are then filtered using an order tracked band pass filter to isolate frequencies of interest. The results are then used to calculate a total torsional energy level, which is compared to a predetermined maximum amplitude. If the total energy exceeds the predetermined maximum, a driver-warning device is triggered.  
           [0008]    This tester has limited capabilities in that it only measures speed fluctuations by measuring passing teeth of rotating gears, which can limit its testing to driveline vibration testing. Further, it only alerts the driver of a problem, it does not predict a likely source of the vibration or what may be causing the vibration at its source.  
           [0009]    Vetronix Corporation (same assignee as the present application) has developed a vehicle “diagnostic toolset” tester, referred to as the Mastertech NVH Kit, which provides for a range of vehicle diagnostics. One of the elements of the diagnostic toolset is a noise and vibration analyzer that is designed to simplify the time required to isolate the cause of vehicle noise and vibrations. The components making up the analyzer include a diagnostic tester that controls all of the functions of the analyzer and provides the user interface. The analyzer software resides on a program card and processes two types of input data: vehicle serial data (RPM and vehicle speed) from the vehicle&#39;s diagnostic connector and vibration or noise data from an accelerometer or optional microphone. The tester computes the frequency spectrum of the sampled data and correlates that spectrum with frequencies associated with various vibration or noise sources as computed from the engine RPM and vehicle speed.  
           [0010]    Among the disadvantages of the Vetronix tester is that it requires multiple modules to perform its noise and vibration testing. Another disadvantage is that the tester is only capable of receiving a vibration or noise signal from one sensor, limiting its testing capabilities. Further, the tester does not generate outputs to assist in vibration analysis and is not capable of communicating over an RS232 cable with a personal computer or printer. The tester also has limited display abilities and while it can provide a potential source of the vibration or noise, it cannot predict what the cause of the vibration or noise may be.  
         SUMMARY OF THE INVENTION  
         [0011]    The present invention seeks to provide an improved Noise, vibration and harshness analyzers (“analyzer”) that is hand held, lightweight, portable and easy to use. It is designed to aid in the quick identification and isolation of noise, vibration and harshness faults in vehicles.  
           [0012]    An analyzer according to the present invention comprises at least one sensor, each sensing a vibration or noise and generating a signal at a frequency related to the vibration or noise. A communication link with a vehicle is included to transmit data regarding the vehicle. A microprocessor system receives the signals generated by said at least, one sensor and receives the vehicle data over said communication link. The microprocessor system conducts an analysis of the received sensor signals and vehicle data and identifies a vehicle component that is likely causing a vibration or noise. The microprocessor system also identifies the possible problems with the identified vehicle component. A user interface is also included with a display. The microprocessor system causes the display to list the likely vehicle components causing the vibration or noise and the possible problems with the components.  
           [0013]    The list of likely components and causes helps the technician quickly isolate and remedy the cause of the vibration or noise. For instance, if the analyzer display shows that the vibration corresponds to a first order wheel condition, the analyzer can than display a list of the probable causes of a first order wheel condition, such as tire or wheel imbalance, wheel hub runout, axle flange runout, or ring gear runout.  
           [0014]    The possible causes of a noise, vibration and harshness condition are narrowed down so that they can be remedied in a timely manner. The analyzer achieves this by a unique combination of inputs including vibration sensor data, vehicle serial data, technician input, and a diagnostic database, which, in combination, produce reliable diagnoses in a short amount of time.  
           [0015]    The present invention also discloses a method for determining if a driveshaft is balanced, which utilizes an analyzer according to the present invention. A first balance test in performed on an unmodified driveshaft. A second balance test is then performed on the same driveshaft with a test weight mounted to the driveshaft. The results of the first and second balance tests are analyzed to determine if the driveshaft is out of balance.  
           [0016]    In a similar test according to the invention uses three tests instead of two. A first balance test in performed on an unmodified driveshaft. The second test is performed with a test weight attached near the front of the driveshaft and a third test is performed with the weight attached near the rear of the driveshaft. The results of the first, second and third tests are analyzed to determine it the driveshaft is balanced.  
           [0017]    For both of these methods, the analyzer can also determine the size and location for a weight to be attached to the driveshaft to counter any driveshaft imbalance. The weight can be attached and the driveshaft can tested again to confirm that it is balanced.  
           [0018]    These and other further features and advantages of the invention would be apparent to those skilled in the art from the following detailed description, taking together with the accompanying drawings, in which: 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 is a perspective view of an analyzer according to the present invention;  
         [0020]    [0020]FIG. 2 is a block diagram of the an analyzer according to the present invention with interconnects to its attached devices and a vehicle;  
         [0021]    [0021]FIG. 3 is a block diagram of the circuitry of analyzer according to the present invention;  
         [0022]    [0022]FIG. 4 is a block diagram of the microprocessor subsystem circuitry in the analyzer of FIG. 3;  
         [0023]    [0023]FIG. 5 is a block diagram of the instrumentation subsystem circuitry in the analyzer of FIG. 3;  
         [0024]    [0024]FIG. 6 is a block diagram of the vehicle interface subsystem circuitry in the analyzer of FIG. 3;  
         [0025]    [0025]FIG. 7 is a block diagram of the user interface subsystem circuitry in the analyzer of FIG. 3;  
         [0026]    [0026]FIG. 8 is a block diagram of the power subsystem circuitry in the analyzer of FIG. 3;  
         [0027]    [0027]FIG. 9 is a frequency spectrum display for an analyzer according to the present invention;  
         [0028]    [0028]FIG. 10 is a bar chart display for an analyzer according to the present invention;  
         [0029]    [0029]FIG. 11 is a waterfall display for an analyzer according to the present invention;  
         [0030]    [0030]FIG. 12 is a principal component display for an analyzer according to the present invention;  
         [0031]    [0031]FIG. 13 is a block diagram of a single-plane driveshaft balancing system according to the present invention; and  
         [0032]    [0032]FIG. 14 is a block diagram of a dual-plane driveshaft balancing system according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0033]    [0033]FIG. 1 shows a perspective view of an analyzer  10  in accordance with the present invention with some of its peripheral components, which together function as a lightweight, high powered and portable noise/vibration analysis tool. The analyzer  10  is housed in a rugged plastic enclosure  12  that has a quarter-VGA LCD display  14  and a keypad  16  having keys disposed on the enclosure  12  around the bottom and sides of the LCD Display  14 . Many different keypads can be used with a preferred keypad having a hydrocarbon resistant membrane and 22 keys including 10 numeric keys, 4 cursor control keys, a HELP key, and a modifier key, (SHIFT) and miscellaneous keys.  
         [0034]    The top surface of the analyzer  10  has five connectors, although other embodiments of the invention can have more or fewer connectors. An on board diagnostics level II (OBD II) connector  18  is included to connect to an OBD II cable  20  to provide a communication link to a the J1962 data link connector (DLC) in OBD II compliant vehicles. Two input connectors  22   a ,  22   b  are included, each of which connects to a sensor. The sensor connectors  22   a ,  22   b  are preferably connected to any combination of two accelerometers  24  or two microphones  26 , or one accelerometer  24  and/or one microphone  26 . A connector  28  provides power to and receives a signal from a device connected to it, such as a remote trigger switch  30  or a photo tachometer  32 . The photo-tachometer  32  is described in more detail below. The remote trigger switch  30  allows pause and save functions of the analyzer  10  to be performed by a single actuation of the remote trigger. This allows the analyzer to be used for safe, single operator, road testing. An output connector  34  provides a signal to an inductive loop  36 , which is attached to a timing light  38  to control the flashing of the timing light.  
         [0035]    The bottom surface of the analyzer  10  includes two connectors, although other embodiments can more or fewer connectors. The first bottom connector  40  is an industry standard bi-directional RS232 communication port, which allows an RS232 cable  42  to be connected to the analyzer  10 . This allows the analyzer  10  to communicate with PC-based systems for download and analysis of data, and to interface with other RS232 compatible devices such as printers and display terminals. The analyzer&#39;s software can also be updated in the field via RS232 download from a PC.  
         [0036]    The second bottom connector  43  is a DC power connector that serves as a connection to a DC power cable that powers the analyzer  10 . A DC power connector and cable  44  can be connected to a standard vehicle cigarette lighter to provide DC power to the analyzer  10 . Alternatively, an AC/DC adapter and cable  46  can be plugged into a standard AC wall power socket to provide to convert standard AC power to DC power for the analyzer.  
         [0037]    [0037]FIG. 2 is an interface block diagram  50  showing some of the different devices that can be connected to an analyzer  52  according to the present invention. As described above, two input connectors allow different combinations of two accelerometers  54   a  and  54   b  or two microphones  56   a  and  56   b  to be connected to the analyzer  52 . The accelerometers  54   a ,  54   b  and/or microphones  56   a ,  56   b  can be mounted on a vehicle  58  or directed toward the vehicle to sense the vibration or noise frequency generated by various vehicle components.  
         [0038]    A serial data link is also established between the vehicle  58  and the analyzer  52  over an OBD II cable  60 , which is connected between the analyzer  52  as described above, and is connected to the vehicle  58  at its (DLC) connector  62 . Data from the vehicle&#39;s engine controller  64  and transmission controller  65  are transmitted to the analyzer  52  over the cable  60 . This data can include different information such as vehicle speed, engine revolutions per minute (RPM) and/or transmission RPM and the cable can also provide power from the vehicle  58  to the analyzer  52 .  
         [0039]    With OBD II compliant vehicles, the analyzer  52  can dynamically synchronize serial data coming across the DLC connector with the vibration input being measured by the accelerometers  54   a ,  54   b  or noise input from the microphones  56   a ,  56   b , in different combinations. This allows a user to view vibration or noise characteristics at various speeds, or during acceleration or deceleration. With non-OBD II complaint vehicles, the user inputs the vehicle speed and RPM into the analyzer  52  using the keyboard.  
         [0040]    The analyzer  52  can also communicate with RS232 devices such as a personal computer (PC)  68  or a printer  70  over an RS232 cable  71 . The analyzer  52  also provides outputs for a photo tachometer  72  and a strobe light  74 .  
         [0041]    [0041]FIG. 3 is a block diagram of the circuitry of an analyzer  80  according to the present invention, which can be generally divided into five subsystems which include the microprocessor subsystem  82 , instrumentation subsystem  84 , vehicle interface subsystem  86 , user interface subsystem  88 , and power subsystem  90 . Each of these subsystems is described below with reference to FIG. 3 and FIGS. 4-8.  
         [0042]    [0042]FIG. 4 shows a more detailed block diagram of the microprocessor subsystem  82 , which is the controlling component of the analyzer  80 , and centers on a microcontroller  92 . Many different microcontrollers can be used, with a preferred microcontroller  92  being a Motorola MC68331, which has a powerful 32-bit CPU32 core operating at 25 MHz and a complement of I/O devices integrated on chip, including serial communication and timing I/O.  
         [0043]    The microprocessor subsystem  82  also contains eight megabytes of flash electrically erasable programmable read only memory (EEPROM)  94  and one megabyte of static random access memory (RAM)  96 , although different types and different sizes of memory can also be used. The flash EEPROM  94  is segmented memory with one of the segments functioning as hardware protected “boot” segment. The boot segment contains all software necessary to communicate with a host computer (via RS232) and download application software to the other flash segments. This allows the analyzer  80  to be fully field reprogrammable. In addition to providing storage for the application software, the flash EEPROM  94  provides non-volatile storage for data that is collected during testing. This data can then be reviewed after the test, or uploaded to a PC for long-term storage.  
         [0044]    A thirty-two (32) megabyte CompactFlash memory device  99  is included which can store data under control of the microcontroller  92 . This memory device is removable and plugs into the CompactFlash connector  98 . The memory device  99  expands the analyzer&#39;s ability to store captured vibration and noise data. The memory device  99  can store up to 146 captured events, although memory devices with larger or smaller storage capabilities can also be used.  
         [0045]    The microprocessor subsystem  82  also provides an RS232 interface via a conventional universal asynchronous receiver transmitter (UART) chip  100  and an RS232 transceiver  102  that communicate with peripheral devices through an RS232 connector  101  (shown in FIG. 3). The UART chip  100  is capable of operating at all standard RS232 baud rates up to 115.2 (Kbps). It contains a FIFO register, which allows maximum communication speeds without putting an excessive load on the processor.  
         [0046]    The microprocessor subsystem  82  also includes a digital signal processor (DSP)  101  which conducts a Fourier transform of the signals from the accelerometers or microphones and generates a frequency spectrum. Many different DSPs can be used with a suitable DSP being the ADSP 2181. In other embodiments of a microprocessor subsystem  82  the Fourier transform can be conducted by the system software, although Fourier transforms conducted in DSPs are generally faster. A clock and calendar circuit  103  is included to generate accurate date and time information that can be used in the noise and vibration analysis. A battery cell  97  is also included to provide back-up power to the clock and calendar circuit  103  and RAM  96  in the event that power from the power subsystem  90  (shown in FIG. 3) is interrupted.  
         [0047]    [0047]FIG. 5 shows the instrumentation subsystem  84  in more detail. It generally consists of signal conditioning circuitry for the sensors, sampling circuitry, and driver circuitry for the photo-tachometer and timing light strobe signal. The analyzer  80  has two sensor inputs  104 ,  106  (shown in FIG. 3), each of which can support one accelerometer or one microphone input. Two accelerometer conditioning circuits  108   a ,  108   b  are included in the instrument subsystem  84  to support one or two accelerometers that could be connected to the sensor inputs  104 ,  106 . Two microphone conditioning circuits  110   a ,  110   b  are included to support the microphones that could be connected to the sensor inputs  104 ,  106 . The conditioning circuits can operate when one microphone and one accelerometer are connected, with only one of the accelerating conditioning circuits  108   a ,  108   b  and one of the microphone conditioning circuit  110   a ,  110   b  operating.  
         [0048]    Hardware low pass filters  112   a - d  are included at the outputs of the conditioning circuits  108   a ,  108   b ,  110   a  and  110   b , that filter out signals above the maximum frequency bands of interest for the analyzer. Filter  112   a  and  112   b  filter out signals above 1000 Hz (accelerometers) and filters  112   c  and  112   d  filter out signals above 8 KHz (microphones). For analysis in lower frequency bands, digital filters are implemented in software to lower the cut-off frequency of the low pass filters.  
         [0049]    The instrumentation subsystem can also include a sample and hold circuit  114  at the output of the low pass filters  112   a - d , which holds the outputs of the filters long enough to allow for a full analog to digital conversion of the signals at the outputs. An eight-channel, bi-polar analog-to-digital converter (ADC)  116  converts the signal from the sample and hold circuit  114  to digital representation of the signals. Many different ADCs can be used with the ADC  116  preferably having a 12-bit (11 bits +sign) resolution and is capable of sampling the input signals at rates of up to 500 Ksamples/second for a single channel. If two input channels are being processed simultaneously (e.g. two accelerometers), the ADC  116  can sample both channels at a rate of up to 50 Ksamples/second. The A/D channels that are not used for sampling the sensor signals can be used for monitoring other analyzer voltages for support of battery charging and self-test.  
         [0050]    The instrumentation subsystem  84  also contains a photo-tachometer interface circuit  118 , which drives a photo-tachometer  32  (shown in FIG. 1). The photo-tachometer  32  produces a pulsed signal to the microprocessor subsystem  82  that is used to make precise measurements of the speed and phase of a rotating object. The output of the interface circuit  118  is connected to the photo-tachometer connector  119  (shown in FIG. 3) and provides power to the photo-tachometer. The interface circuit  118  also receives signals from the photo-tachometer through the connector  119 . The interface circuit  118  is primarily used for driveshaft balancing, but it can also be used to analyze vibration based on other-rotating components.  
         [0051]    The instrumentation subsystem also includes a strobe light circuit  120  for driving a timing light  32  (shown in FIG. 1), with the output of the circuit  120  connected to a strobe output  121  (shown in FIG. 3.) The circuit  120  provides a signal under software and microcontroller control, in the form of a sequence of current pulses. This allows the signal to be synchronized to the frequency of any potential vibration source.  
         [0052]    [0052]FIG. 6 shows the vehicle interface subsystem  86 , which primarily provides the capability of communicating to the vehicle&#39;s engine controller and/or transmission controller  64 ,  65  (shown in FIG. 2) through a diagnostic link connector (DLC)  123  (shown in FIG. 3) for the purpose of obtaining real-time readings of the vehicle&#39;s speed, engine RPM and driveshaft RPM. For some vehicles, the vehicle interface subsystem reads calibration information from the vehicle controllers such as vehicle identification number (VIN), tire size and axle ratio. The hardware and software of the analyzer  80  supports all of the currently defined OBD II protocols as well as some future OBD II protocols, allowing it to communicate with any  1996  or later vehicle. A transceiver  122  is included to support International Standards Organization (ISO)  9141 - 2  communication on an ISO K-line signal line (bi-directional)  124  and an ISO L-line signal line (unidirectional)  126 . A controller area network (CAN) transceiver  128  and CAN controller  130  are included to support communication over the CAN+ and CAN− signal lines  132 ,  134 . A data link controller serial (DLCS)  136 , a queued bus interface controller (QBIC)  138  and a 41.6K Pulse Width Modulated (PWM) Transceiver  140  are included to support 10.4K VPW J1850 and 41.6K PWM J1850 communication over J1850+connector pin  142  and J1850− connector pin  144 .  
         [0053]    The vehicle interface subsystem  86  also contains provisions for an expansion board  146  and connectors  148 ,  149  for expanding the protocol support. In some cases, expansion can be accomplished simply by a field upgrade of the software, such as the addition of manufacturer specific variations of the OBD II protocols (e.g. SAE J2190). In other cases, expansion to new protocols requires additional hardware. The expansion connector  149  interfaces to the processor&#39;s buses and unused pins from the DLC connector  123  are routed to the expansion connector  148  allowing a hardware expansion board to be field installed.  
         [0054]    [0054]FIG. 7 shows the user interface subsystem  88 , which includes a keyboard interface  150  that provides the interface between the keyboard  154  and the microcontroller  92  (shown in FIG. 4). The keypad  154  contains 22 membrane keys, as described above in FIG. 1, each of which can be pressed alone or simultaneously with another key to modify its function. A speaker driver  152  is included that drives a speaker  156  with a signal from the microcontroller  92 . The speaker  156  provides an audio alert to signal a particular analyzer condition, such as a full buffer. A display controller  158  is coupled to the microcontroller bus and controls an LCD display  160  in response to commands it receives from the microcontroller  92 . The LCD display is preferably a quarter-VGA (320×240 pixels) LCD display with a 4.7″ diagonal viewing area and a cool cathode fluorescent lamp (CCFL) backlight that provides good readability under all lighting conditions. The display  160  provides full graphic capability allowing waveforms to be plotted as well as numerous fonts.  
         [0055]    [0055]FIG. 8 shows the power subsystem  90  in more detail. Under normal operation, a voltage is supplied to the power supply  159  from the vehicle under test, through the battery voltage pin  162  of the DLC connector  123 . Power can also be supplied from an alternate source via a standard power jack  164  on the analyzer  80 . This allows the analyzer  80  to be powered from the cigarette lighter in vehicles that do not have a DLC connector  123 , or from an AC/DC Adapter for benchtop operation (e.g. for upload of data to PC). Diode protection  166  is provided to eliminate problems if two power sources are connected simultaneously. The analyzer  80  also contains an internal battery pack  168  for operation when the power supply is not connected to an external power source. The battery pack  168  is charged whenever the NVH analyzer is operated from an external power source.  
         [0056]    In operation, the analyzer  80  can display test data at its LCD  160  in many different ways to display both real time and stored data, with the preferred LCD display  160  being updated at a minimum rate of 2 updates/second. Four different LCD displays according to the present invention are shown in FIGS. 9-12, although many other displays according to the invention can be displayed on the LCD.  
         [0057]    [0057]FIG. 9 shows a two-dimensional (2-D) frequency spectrum display  170  according to the present invention that displays real time spectral vibration or noise data. It displays a real time 2-D frequency spectrum of the vibration or noise data as amplitude versus frequency for a specified source of vibrations or noise (e.g. wheels).  
         [0058]    The display  170  shows a 62.5 Hz frequency spectrum along the horizontal scale  172  and the amplitude of these frequencies along the vertical scale  174 . Different frequency spectrums can be used for the horizontal scale including 125 Hz, 250 Hz, 500 Hz and 1000 Hz for viewing either the real time vibration data (accelerometers) or noise data (microphones). Addition frequency spectrums of 2000 Hz, 4000 Hz and 8000 Hz are also available for viewing noise data. A vibration/nois component identifier  176  is shown for the particular vehicle component being tested, in this case the wheels, and different displays can be shown for the vehicle&#39;s engine or driveline. A moveable cursor  178  identifies the magnitude and frequency of the vibration that is present at the current cursor position. In this case the cursor  178  is at the 15.25 Hz frequency, which has a magnitude of 0.025.  
         [0059]    [0059]FIG. 10 shows a three-dimensional (3-D) barchart display  180  according to the present invention that displays the amount of vibration energy associated with each vibrations source in a bar chart versus time format. The vibration or noise data are displayed in bars that reflect the engine  182 , driveline  184 , wheel  186 , and total  188  energy sampled. Eleven sequential time frames of this data are displayed for analysis and comparison, with the most recent time cycle displayed at the bottom of the barchart display. More or fewer time frames can be displayed and different vibration sources can be displayed.  
         [0060]    [0060]FIG. 11 shows a three-dimensional (3-D) waterfall display  190  according to the present invention that displays a 3-D version of the amplitude verses frequency display  170  shown in FIG. 9. Instead of a 2-D display, the display  190  includes multiple sequential time frames of vibration or noise data in a 3-D raster format. Different number of time frames can be displayed, with the display  190  having twenty one (21) sequential time frames. The most recent cycle is displayed at the bottom of the raster display. Just as in display  170  in FIG. 9, frequency bands of 62.5 Hz, 125 Hz, 250 Hz, 500 Hz and 1000 Hz are available for the horizontal scale  192 , for viewing real time spectral vibration data and noise data. Additional frequency bands of 2000 Hz, 4000 Hz and 8000 are used for noise data. The vertical scale  194  is for the amplitude of the frequency. A vibration component identifier  196  identifies the component being tested, in this case the wheels.  
         [0061]    [0061]FIG. 12 shows a principal component display  200  according to the present invention that includes a list  202  of the largest peaks in a particular frequency spectrum along with their frequency  204  and amplitude  206 . In the embodiment shown, up to six different frequencies can be displayed, although other numbers of frequencies can be displayed. The analyzer also compares the frequencies of these components with the characteristic frequencies associated with the vehicle&#39;s rotating components (e.g. wheels). If a match is found, the display  200  shows the probable source  207  of the vibration signal (e.g. 2 nd  Order Wheel). If a frequency does not match one of the vehicle&#39;s principal components, a “No match found” message  208  is displayed.  
         [0062]    The determination by the analyzer of whether or not a particular vibration or noise frequency matches one or more of the vehicle&#39;s principal components is partially controlled by the order cut parameter. This is a user-specified parameter that defines the acceptable frequency error for a match. For each of the vehicle&#39;s principal components, the analyzer displays a prioritized list of possible causes for the vibration (e.g. excessive tire or wheel runout).  
         [0063]    Each of the displays in FIGS. 9-12 also show data related to engine rotational speed  210 , vehicle speed  212 , driveshaft speed  214 , and photo-tachometer (when used)  216 . Each also includes the date  218 , time  220 , and vehicle identification number  222 . A sensor indentifier  224  is also included to show the type of sensor, in this case accelerometer, and which of the two input channels is receiving the sensor date, in this case channel A.  
         [0064]    The analyzer keyboard (shown in FIG. 1) contains a RUN/PAUSE key and when the analyzer is in the RUN mode, data is sampled from the sensors and data is being read from the vehicle. This data is saved in a circular buffer in RAM memory, with the buffer being capable of saving up to 30 seconds of data for two sensors. Pressing the RUN/PAUSE key while the analyzer is in the RUN mode causes the analyzer to change to the PAUSE mode. In the PAUSE mode, the data from the previous 30 seconds of testing can be analyzed and displayed in any of the four displays shown in FIGS. 9-12. The vibration/noise data is saved in the time domain allowing the replay of the spectral data to be performed for any frequency band. During the replay, the user can also change sensors, amplitude scales, system identifiers (engine, driveshaft, wheels) and filter mode. The SAVE key can be pressed to copy the captured data to the internal flash memory  94  or to the CompactFlash memory device  99  (both shown in FIG. 5). The NVH can save  24  events in the Flash memory  95  and  122  additional events in the 32 Mbyte CompactFlash device  99 .  
         [0065]    The software for the analyzer  10  is divided into the boot software and application software. The boot software is programmed at the factory and is considered a permanent part of the analyzer  10 . It is programmed into a hardware-protected segment of the Flash EEPROM  94  and requires a special programming fixture for update. The boot software provides all of the functions needed to support reprogramming of the remaining segments of the Flash EEPROM  94 . One such routine is power-on reset, which includes the logic necessary to initialize the hardware after a power-on reset. Another is the Real-Time operating system (RTOS) kernel, with is the software necessary to control the analyzer in the real-time environment of data acquisition, signal processing and user interface. Others are the communication routines, which include the software necessary to communicate with a PC via RS232 and to download blocks of data for programming the analyzer&#39;s remaining memory. Still others are the flash memory routines, which include the software necessary to read, erase and write blocks of Flash EEPROM memory.  
         [0066]    The application software performs all the application specific functions of the analyzer. It can be field upgraded, via an RS232 download from a PC, as new features and functions are added to the software. Some of the functions performed by the application software in different embodiments of the invention include: controlling the moding of the analyzer circuitry; controlling the sampling process; performing a Fast Fourier Transform (FFT) algorithm to convert data to the frequency domain; controlling communication with the vehicle&#39;s engine or transmission controller; correlating the vibration or noise frequencies with the characteristic frequencies for various vibration or noise sources; processing of all user inputs; outputting data to the LCD display, and providing an RS232 interface to other system components (e.g. printer or PC).  
         [0067]    The application software also provides the user interface, I/O and computation to perform single and dual plane driveshaft balancing, and provides an output to drive a strobe light at a frequency that is either manually controlled or controlled relative to engine or driveshaft RPM.  
         [0068]    In operation the analyzer  80  provides the user interfaces to the LCD Display  160  and speaker  156 . The analyzer also conditions the input signals from the sensors attached to the sensor A and sensor B inputs  104 ,  106 , samples these signals and converts them to the frequency domain. At the same time analyzer  80  communicates with the vehicle&#39;s engine and transmission controllers over the DLC connector using generic OBD II messaging and manufacturer-specific messaging, to obtain information to support testing. Calibration information, including vehicle identification number (VIN), Axle Ratio, and Tire Size, is available from the engine controller on some vehicles and can also be communicated to the analyzer over the DLC connector. For vehicles that do not support these parameters, the analyzer prompts the user to input them manually. The analyzer  80  contains a database that is used to decode the VIN number to determine the body, engine and drive configuration.  
         [0069]    The analyzer  80  also reads operational information from the vehicle&#39;s engine and transmission controllers including engine RPM, vehicle speed and transmission output shaft speed. This data is used by the analyzer to compute the characteristic frequencies associated with various noise or vibration sources. It then compares these frequencies with those computed from the sensors in order to assist with the isolation of the source of the vibration or noise.  
         [0070]    As described above, a strobe output  120  is provided that can be used to drive a timing light  38  (shown in FIG. 1). The analyzer&#39;s software synchronizes flashes of the timing light to a user-selected frequency or to the frequency of a user selected vibration source. This provides the service technician with a visual mechanism for isolating the source of a vibration. The flashes can also be synchronized to harmonics of the engine or driveshaft rotations as reported by the engine or transmission controller.  
         [0071]    As also described above, the analyzer  80  (shown in FIG. 3) provides new ways of displaying vibration-related data. On its LCD display  160  it graphically displays frequency and amplitude of vibration or noise energy. It displays probable cause diagnosis for vibrations caused by the engine, driveline, or tires/wheels and is not limited to display of only the three highest vibrations. It integrates frequency data calculated from the sensors with characteristic frequencies of vibrations of on-board components. These frequencies are calculated from real-time vehicle data read from the engine or transmission controller using any of a wide range of serial data, including the OBD II protocols.  
         [0072]    One of the functions performed by the analyzer is dynamic on-vehicle driveshaft balancing, both single-plane and dual-plane. FIG. 13 shows a block diagram of a system  230  for single-plane driveshaft balancing according to the present invention, showing the interconnections between the analyzer  232  and a vehicle  234 . The analyzer  232  controls the operation of the balancing analysis and provides the user interface. In the vehicle  234 , an engine/transmission controller  236  is connected to and controls the engine  237  and the transmission  238 . The analyzer  232  is connected to the engine/transmission controller  236  over a serial data cable  239 , through the diagnostic (DLC) connector  240 . Through this interface the analyzer  232  reads engine and driveshaft data from the vehicle&#39;s engine/transmission controller  236 . The serial data cable  239  also provides power to the analyzer  232 .  
         [0073]    For single-plane balancing, one accelerometer  242  is attached to the axle differential  244  of a driveshaft  250  to measure the amplitude and phase of the vibrations due to driveshaft rotation. The analyzer&#39;s photo-tachometer  246  is used to measure the driveshaft RPM and to provide a reference for the phase measurements of the accelerometer&#39;s vibration signals. Reflective tape  248  is attached to the driveshaft  250  and as the driveshaft  250  rotates, the light beam emitted from the photo-tachometer  246  reflects off of the reflective tape  248 . The reflection generates a pulse at the photo-tachometer  246  for every revolution that is transmitted to and measured by the analyzer  232 . The analyzer  232  uses the pulses to compute the driveshaft RPM and this RPM is validated by comparing it to the driveshaft RPM reported by the engine/transmission controller  236  via the serial data cable  239 . The time for each pulse is also saved for use in vibration phase calculations.  
         [0074]    During the balancing tests, the driveshaft  250  is run at a balancing speed specified by the test operator or by the driveshaft manufacturer. For some vehicle models, the analyzer  232  can control the engine RPM via an engine speed module  252 , which adjusts the RPM by controlling the signal that is output to the engine&#39;s idle speed control (ISC) solenoid (not shown). The ISC solenoid is normally controlled by the engine/transmission controller  236 , but for driveshaft balancing, it can be controlled by the analyzer  232 . With the analyzer  232  controlling the engine RPM and monitoring the driveshaft RPM, it performs closed-loop control of the driveshaft RPM in order to maintain the driveshaft rotation at a constant rate equal to the specified driveshaft balancing RPM.  
         [0075]    The analyzer  232 , samples and filters the accelerometer  242  signals to isolate the fundamental of the vibration frequency (the frequency of revolution of the driveshaft  250 ). The amplitudes of the filtered vibration signals are then measured, as are the phase angles between the photo-tachometer  246  reference and the peaks of the vibration signals. The center frequency of a bandpass filter is dynamically adjusted so that the filter matches the current value of the driveshaft RPM.  
         [0076]    For the single-plane driveshaft balancing procedure, this process is repeated three times with the driveshaft run at the same speed, and the amplitudes of the filtered vibration signals are measured along with the phase angles. The first balancing procedure determines a baseline test with the driveshaft  250  unmodified. The second procedure is conducted with a known “test weight”  254  added to the driveshaft  250 . Based on the analysis of the initial baseline measurements and of the effects of adding a test weight  254 , the analyzer  232  computes the size and position of a weight that is required to counter balance any vibrations that were present at the start of the test. The preferred location for mounting a counterbalance weight is to near the differential  242 . A third balancing procedure is conducted after a repair balance weight  255  has been added, to verify the repair.  
         [0077]    [0077]FIG. 14 shows a block diagram of a system  260  for dual-plane balancing according to the present invention. Many of the same devices and interconnects that are used in the system  230  of FIG. 13 are used in the system  260  and for these devices and interconnects the same reference numerals are used and they will not be described again herein. For a dual-plane balance system two accelerometers are used, one mounted on fixed surfaces at each end of the driveshaft. The first accelerometer  242  is attached to the differential as in the system  230  of FIG. 13. A second accelerometer  262  is attached to the transmission and like the first accelerometer  242 , it provides a sensor input to the analyzer  232 .  
         [0078]    The dual-plane driveshaft balancing procedure is an extension of the single-plane case and instead of three balancing procedures, it includes four. The first balancing procedure determines a baseline test with the driveshaft  250  unmodified. The second procedure is conducted with a known “test weight”  254  added to the coupler at front of the driveshaft  250 . A third balancing procedure is conducted with the test weight  254  from front shifted to the coupler at the rear of the driveshaft  250 . At the completion of the procedures performed with the test weight  254  attached to the driveshaft  250 , the analyzer  232  computes the amount of imbalance that was present in the driveshaft  250  at the beginning of the test. If that imbalance level is below a specified limit, then the driveshaft  250  is considered balanced and no further testing is required. If the calculated imbalance is above this limit, the analyzer  232  computes the size and position of front and rear counterbalance weights  255  that are required to counterbalance any vibrations that were present at the start of the test. The weights are preferably mounted to the driveshaft near the front and the rear of the driveshaft  250 . A fourth balancing procedure is conducted after a repair balance weight  255  has been added, to verify the repair.  
         [0079]    Different methods can used for attaching the balancing weight  255  to the driveshaft  250  such as attaching it directly to the driveshaft  250  or attaching it to the coupling flange that connects the driveshaft to the differential (or transmission). The weight  255  can be attached to the driveshaft using bands, hose clamps or spot-welding.  
         [0080]    For vehicles that have an appropriately designed coupling flange to connect the driveshaft to the differential, this coupler can be used for both attaching the test weight  254 , and for the permanent installation of the balancing weight  255 . The balancing weight  255  can be some combination of bolts, nuts and washers. In one case, referred to as nut balancing, the test weight  254  is a nut of known weight installed on a specified coupling bolt. As part of the test, the balancing solution is computed to direct the operator to install a balancing weight  255  that is a combination of nuts on specified bolts. This speeds up the balancing procedure and minimizes the likelihood of errors resulting from improperly installed balancing weights.  
         [0081]    Both the single-plane and dual plane driveshaft balancing systems provide support for a hard-copy printout of test results. An RS232 interface  266  is included to communicate with serial printer  268  that is provided to generate documentation for the driveshaft balance procedure.  
         [0082]    Although the present invention has been described in considerable detail with reference to certain preferred configurations thereof, other versions are possible. The analyzer can support other inputs and outputs and can display its captured data in many different ways. Other hardware and software components could also be used in other analyzer embodiments according to the present invention and the hardware components could be used in different ways. The analyzer can also be used to analyze noise or vibration in vehicle components beyond those described above and in systems other than vehicles Therefore, the spirit and scope of the present invention should not be limited to the preferred versions of the invention described above.