Patent Publication Number: US-6668220-B2

Title: Synchronous sampling of rotating elements in a fault detection system having audio analysis and method of using the same

Description:
The present application claims priority from provisional application, Serial No. 60/373,157, entitled “Synchronous Sampling of Rotating Elements in a Fault Detection System Having Audio Analysis and Method of Using the Same,” filed Apr. 17, 2002, which is commonly owned and incorporated herein by reference in its entirety. Moreover, this patent application is related to co-pending, commonly assigned patent application, Ser. No. 10/213,784, entitled “Fault Detection System Having Audio Analysis and Method of Using the Same,” filed concurrently herewith and incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention in general relates to the detection of faults in a vehicle and, more particularly, to synchronous sampling of rotating elements in a fault detection system having audio analysis and a method of using the same. 
     BACKGROUND OF THE INVENTION 
     A user of a vehicle may hear an unpleasant sound or feel a strange vibration while operating a vehicle. Most users of vehicles are not trained to know or recognize the source of such a sound or vibration and in many cases significant changes over longer periods of time are so subtle they go undetected. Many unpleasant sounds and strange vibrations are generated by faults of rotating elements in a vehicle such as the tires, the engine, the driveline, and the fan or blower of the heating, ventilation, and air-conditioning (HVAC) system. Accordingly, there is also a need for aiding the user of a vehicle to identify the source of unpleasant sounds or strange vibrations in the vehicle. 
     Various systems have been employed for detecting faults on a vehicle. Existing systems require dedicated sensors outside the cabin of a vehicle for each component on the vehicle. These sensors are susceptible to fault over time due to exposure to corrosive and other harsh environments. 
     In the past, systems have considered using an audio transducer located in close proximity to a component susceptible to a fault. Such systems, however, require multiple audio transducers if there is a desire to monitor multiple components. Additionally, these audio transducers are susceptive to interference from sounds and vibrations of other components. Furthermore, the sensors themselves may be susceptible to corrosion and other faults if they are located in harsh environments. 
     Accordingly, further improvements are needed to known systems for the monitoring of multiple components on a vehicle. It is, therefore, desirable to provide an improved procedure for detecting faults of rotating elements in a vehicle to overcome most, if not all, of the preceding problems. 
     BRIEF SUMMARY OF THE INVENTION 
     One aspect of the present invention provides a fault detection system for determining whether a fault exists with a rotating element of a vehicle. The system includes a transducer, a diagnosis sampler, a sensor, and a controller. The transducer may be a microphone located in the vehicle for converting sounds to an electrical signal. The electrical signal includes a noise component generated from the rotating element. The diagnosis sampler is connected to the transducer and provides a sample of the electrical signal from the transducer to the controller. The sensor obtains data relating to the rotating element. The controller has functional aspects such as a synchronous resample, a spectrum analysis, and a fault detect. The synchronous resample has the capability of synchronizing the sample of the electrical signal with the data from the sensor to form a synchronized envelope. The spectrum analysis has the capability of forming a spectra from the synchronized envelope or the electrical signal, where the spectra is associated with the noise component generated from the rotating element. The fault detect has the capability of determining (from the formed spectra) whether the fault exists with the rotating element. 
     Another aspect of the present invention provides for detecting a fault associated with a rotating element in a vehicle. This can include: sampling an electrical signal from a transducer in the vehicle where the electrical signal comprises a noise component generated from the rotating element; synchronizing the electrical signal with data from a sensor associated with the rotating element to form a synchronized envelope associated with the rotating element; forming a spectra from the synchronized envelope where the spectra is associated with the noise component generated from the rotating element; and determining (from the formed spectra) whether a fault exists with the rotating element. 
     A further aspect of the present invention provides for detecting a fault associated with a plurality of rotating elements in a vehicle. This can include: sampling an electrical signal from a transducer in the vehicle where the electrical signal comprises a plurality of noise components generated from the rotating elements; synchronizing the electrical signal with data from a plurality of sensors associated with the rotating elements to form a synchronized envelope associated with each rotating element; forming a plurality of spectra from the synchronized envelopes where each spectra is associated with one of the noise components generated from the rotating elements; and determining (from each of the plurality of formed spectra) whether a fault exists with one of the rotating elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a fault detection system according to one embodiment of the present invention; 
     FIGS. 2A-2E are exemplary spectra diagrams for various rotating elements on a vehicle; 
     FIG. 3 is a block diagram of another embodiment of a system incorporating the fault detection system of the present invention. 
    
    
     While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION 
     What is described is an improved system and procedure for detecting faults associated with rotating elements on a vehicle. To this end, in one embodiment there is a fault detection system for determining whether a fault exists with a rotating element of a vehicle. The system includes a transducer, a diagnosis sampler, a sensor, and a controller. The transducer may be a microphone located in the vehicle for converting sounds to an electrical signal. The electrical signal includes a noise component generated from the rotating element. The diagnosis sampler is connected to the transducer and provides a sample of the electrical signal from the transducer to the controller. The sensor obtains data relating to the rotating element. The controller has functional aspects such as a synchronous resample, a spectrum analysis, and a fault detect. The synchronous resample has the capability of synchronizing the sample of the electrical signal with the data from the sensor to form a synchronized envelope. The spectrum analysis has the capability of forming a spectra from the synchronized envelope of the electrical signal, where the spectra is associated with the noise component generated from the rotating element. The fault detect has the capability of determining (from the formed spectra) whether the fault exists with the rotating element. 
     Another embodiment of the present invention is a method for detecting a fault associated with a rotating element in a vehicle. The steps of the method include: sampling an electrical signal from a transducer in the vehicle where the electrical signal comprises a noise component generated from the rotating element; synchronizing the electrical signal with data from a sensor associated with the rotating element to form a synchronized envelope associated with the rotating element; forming a spectra from the synchronized envelope where the spectra is associated with the noise component generated from the rotating element; and determining (from the formed spectra) whether a fault exists with the rotating element. 
     A further embodiment of the present invention includes a method for detecting a fault associated with a plurality of rotating elements in a vehicle. This steps of this method include: sampling an electrical signal from a transducer in the vehicle where the electrical signal comprises a plurality of noise components generated from the rotating elements; synchronizing the electrical signal with data from a plurality of sensors associated with the rotating elements to form a synchronized envelope associated with each rotating element; forming a plurality of spectra from the synchronized envelopes where each spectra is associated with one of the noise components generated from the rotating elements; and determining (from each of the plurality of formed spectra) whether a fault exists with one of the rotating elements. 
     Now, turning to the drawings, an example use of a fault detection system for a vehicle will be explained. As will be explained in more detail below, the fault detection system samples the sound in a cabin of the vehicle and uses the sampled sound as a diagnostic tool for determining whether a fault exists with rotating elements in the vehicle. Referring to FIG. 1, in one embodiment, a fault detection system  20  generally has a transducer  22 , a diagnosis sampler  24 , and a controller  26 . The fault detection system  20  determines whether a fault or problem exists with one of a plurality of rotating elements  30   a ,  30   b ,  30   c  in the vehicle. Examples of rotating elements  30   a ,  30   b ,  30   c  in the vehicle include elements such as the tires, the engine, the driveline, and the fans or blower for the heating, ventilation, and air-conditioning (HVAC) system. 
     As discussed in more detail below, after analysis of the sampled sound, a signal representing a fault or problem may be transmitted by the controller  26  to an electronic control unit (ECU)  32 . The ECU  32  may then notify the user of the vehicle via a user display panel  34  that a fault or problem exists with a rotating element  30   a ,  30   b ,  30   c . Alternatively, or additionally, a digital signal representing the fault or problem may be transmitted via a wireless communication device  36  to a service center (shown in FIG.  3 ). 
     The transducer  22  may be a microphone located in the cabin of the vehicle. In one embodiment, the transducer  22  is a microphone used for hands-free voice calls through the wireless communication device  36 . The wireless communication device  36  is connected to the transducer  22  and to an audio speaker  38  within the cabin. The transducer  22  may also be a microphone used for communication with a remote service center for information and roadside assistance. Utilizing an existing microphone in the cabin provides the advantage of multi-tasking a single component in the vehicle. Alternatively, a separate dedicated transducer  22  may be installed in the vehicle. 
     The transducer  22  converts sounds in the cabin of the vehicle to an electrical signal  40 . In one embodiment, the electrical signal  40  from the transducer  22  is an analog signal. The diagnosis sampler  24  receives the electrical signal  40  from the transducer  22 . The purpose of the diagnosis sampler  24  is to sample the electrical signal  40  from the transducer  22  for input to the controller  26 . The diagnosis sampler  24  may be a separate integrated circuit from the controller  26 . Alternatively, the diagnosis sampler  24  may reside within the controller  26  and be an integral part of the input. The diagnosis sampler  24  allows the electrical signal  40  to be further analyzed by the controller  26 . 
     In one embodiment, the diagnosis sampler  24  takes samples of the electrical signal  40  and converts the electrical signal  40  to a format acceptable to the controller  26 . For example, if the controller  26  is a digital signal processor (DSP) controller, the electrical signal  40  is converted to a digital signal  42 . Accordingly, the diagnosis sampler  24  may include components such as an amplifier and an Analog to Digital (A/D) converter. The sampling rate should depend on the frequency limit of the transducer  22 . For example, in one embodiment, the sampling process would be at least double the highest frequency range of the transducer. This means that for a transducer  22  that can pick up sounds up to 6 kHz, the minimum sampling rate for the diagnosis sampler  24  is 12,000 samples per second. In most embodiments, the diagnosis sampler  24  should be about 16,000 samples per second and having a 12 bit resolution for each sample. 
     The diagnosis sampler  24  may be configured a number of different ways to sample the electrical signal  40  from the transducer  22 . In one embodiment, the diagnosis sampler  24  is configured to continuously sample the electrical signal  40  at select time intervals during the operation of the vehicle. In another embodiment, the diagnosis sampler  24  is configured to sample the electrical signal  40  in response to an instruction from the electronic control unit  32  or controller  26 . The instruction to sample the cabin sound could be sent when certain known conditions exist within the vehicle (i.e. when a rotating element is rotating at a certain rate). Furthermore, the diagnosis sampler  24  may be configured to sample the electrical signal  40  or be otherwise activated in response to an instruction from a service center (not shown) and/or the user of the vehicle. 
     The electrical signal  40  generated by the transducer  22  is a composite of sound components in the cabin of the vehicle. In one embodiment, the digital signal  42  generated by the diagnosis sampler  24  will also be a composite of sound components in the cabin of the vehicle. 
     One component of the sampled sound will be noise from rotating elements  30   a ,  30   b ,  30   c  of the vehicle. In some cases, the noise related to the actual rotation of rotating elements  30   a ,  30   b ,  30   c  will be much lower in frequency than the limits of the transducer  22 . For instance, if the transducer  22  is a microphone for hands-free voice calls or information/road-side assistance services, these microphones can only pick up sounds between the range of 400 Hz and 6 kHz. Accordingly, the transducer  22  may not directly pick up the noise related to the actual rotation of these rotating elements  30   a ,  30   b ,  30   c  if they are below 400 Hz. The noise associated with the rotation of a rotating element  30   a ,  30   b ,  30   c , however, will propagate to the structure of the vehicle (such as the chassis). Noise through the structure of the vehicle rings in response to forces generated by the rotating elements  30   a ,  30   b ,  30   c . It has been discovered that the ringing allows a transducer  22  with limited frequency response to detect the state of the rotating elements  30   a ,  30   b ,  30   c  even when the elements themselves are rotating slowly relative to the pass band of the audio system. 
     For example, as mentioned above, one of the rotating elements  30   a ,  30   b ,  30   c  on a vehicle may be the tires. A tire having a radius of 18 inches will rotate at 560 RPM at 60 MPH. This will cause a repetition rate of 9.3 Hz. Sounds at this frequency are too low for the microphone to pick up much less an audible frequency for a human ear (20 Hz-20 kHz). The tire assembly, however, is attached to the chassis of the vehicle. A 9.3 Hz frequency will generate a vibration to the chassis of the vehicle that will result in a higher frequency noise. The transducer  22  will pick up the higher frequency noise from the chassis caused by the rotating elements. 
     The vibration noise from the chassis is a composite of several other vibration noises caused from other sources of the vehicle. One aspect of the present invention is directed to associating a noise with a particular rotating element  30   a ,  30   b ,  30   c  from the composite of vibration noises and analyzing that noise to determine a fault or problem for the rotating element  30   a ,  30   b ,  30   c.    
     The controller  26  processes the digital signal  42  from the diagnosis sampler  24 . A suitable controller  26  for the present invention may includes a digital signal processor (DSP) controller or a Motorola MPC 5100. The controller  26  of the present invention preferably includes a number of functional blocks. In one embodiment, the controller has an envelope detect  44 , a synchronous resample  46 , a plurality of spectrum analyses  48   a ,  48   b ,  48   c , and a plurality of fault detects  50   a ,  50   b ,  50   c . These functional blocks may be microcoded signal processing steps that are programmed as operating instructions in the controller  26 . 
     The envelope detect  44  detects an envelope  52  from the digital signal  42  received from the diagnosis sampler  24 . The envelope  52  is generated to capture the peak amplitude values of signal bursts and rings. This can be accomplished by rectification of the digital signal  42  and low pass filtering. Both the rectification and the low pass filtering are done digitally. The rectification may be done by taking the absolute value of the digital signal  42 . The rectification process may be a mathematical absolute model or other digital representation known to those of ordinary skill in the art. 
     The rectified data is then applied to the low pass filter. The cutoff frequency used for the low pass filter is implementation specific. The cutoff frequency will typically depend on the size of the rotating element (such as the size of the rotating tire). It has been found, however, that each of the rotating elements in a vehicle come within a range of 5-100 pulses per second. In a cost efficient implementation, a suitable cutoff frequency for the low pass filtering may be selected between 200-400 Hz. Alternatively, separate low pass filtering may be implemented for each of the rotating elements. In any event, as will be discussed further, the monitoring and analysis of the envelope  52  of cabin sounds enables the detection of faults or problems with a particular rotating element in the vehicle. 
     Within the envelope  52  is a mixture of sounds from the cabin of the vehicle that were picked up by the transducer  22 . Some of these sounds may relate to possible problems of the vehicle and some may not relate to problems of the vehicle. The present invention includes a synchronous resample  46  to correlate and synchronize the noise associated with individual rotating elements  30   a ,  30   b ,  30   c  in the vehicle. 
     It has been discovered that the vibration noise from the chassis or other vehicle structure generated from the rotating elements  30   a ,  30   b ,  30   c  is closely related to the rotation of that element. Accordingly, knowing the rotation of an element  30   a ,  30   b ,  30   c  allows the controller  26  to synchronize the composite envelope  52  for further analysis of a particular rotating element  30   a ,  30   b ,  30   c.    
     To this end, the synchronous resample  46  receives sensor data  54   a ,  54   b ,  54   c  relating to each of the rotating elements  30   a ,  30   b ,  30   c . The sensor data  54   a ,  54   b ,  54   c  is used to synchronize the composite envelope signal  52  for a particular rotating element  30   a ,  30   b ,  30   c . The sensor data  54   a ,  54   b ,  54   c  is obtained from sensors  56   a ,  56   b ,  56   c , respectively, located at each of the rotating elements  30   a ,  30   b ,  30   c.    
     In one embodiment, the sensor data  54   a ,  54   b ,  54   c  is representative of the angular displacement of the rotating elements  30   a ,  30   b ,  30   c . There are a number of ways to measure the angular displacement of an element. In one embodiment, the sensors  56   a ,  56   b ,  56   c  measure a passing tooth  58   a ,  58   b ,  58   c , respectively, on a rotating wheel of the rotating element  30   a ,  30   b ,  30   c . For example, a sensor may measure a passing tooth on a rotating wheel attached to an engine&#39;s crankshaft. As the engine runs, the sensor typically generates a logic level signal that transitions when the sensor senses the tooth and a subsequent space. As the toothed wheel rotates, responsive to the combustion process in the running engine, the angular displacement signal will typically be a rectangular waveform responsive to angular velocity, or engine speed. The practice of using a toothed wheel on a crankshaft and other rotating elements is commonplace in the field of vehicle control. Of course, those skilled in the art will recognize many other, substantially equivalent, means and methods to measure angular displacement. 
     The sensor data  54   a ,  54   b ,  54   c  is provided to the synchronous resample  46 . The sensor data  54   a ,  54   b ,  54   c  is used to synchronize the composite envelope  52  to generate synchronized envelopes  60   a ,  60   b ,  60   c  associated with each rotating element  30   a ,  30   b ,  30   c . Accordingly, the synchronized envelope  60   a  relates to rotating element  30   a . The synchronized envelope  60   b  relates to rotating element  30   b . The synchronized envelope  60   c  relates to rotating element  30   c . Each synchronized envelope  60   a ,  60   b ,  60   c  is then further analyzed by a separate spectrum analysis functional block  48   a ,  48   b ,  48   c.    
     In one embodiment, the resample of the composite envelope  52  includes giving the envelope signal a new scale (sampling period). For example, the composite envelope  52  may have a sampling period of 16,000 samples per second. There is a need to resample this envelope at a different rate depending on the rate of the rotating elements  30   a ,  30   b ,  30   c . The synchronous resample  46  forms a synchronized envelope  60   a ,  60   b ,  60   c  depending on the rotating rate of the rotating elements from the sensors  56   a ,  56   b ,  56   c.    
     The rotating element  30   a  in one embodiment may be a tire on a vehicle. Associated with the tire is an anti-brake system (ABS) sensor  56   a  that can generate data that can be used to determine the rotational rate of the tire at a particular time. The ABS sensor  56   a  will transmit data  54   a  to the synchronous resample  46 . The synchronous resample  46  receives the data  54   a  from the ABS sensor  56   a . The ABS sensor data  54   a  is then used as the sampling clock to synchronize the composite envelope  52  to generate a tire synchronized envelope  60   a  for the tire spectrum analysis  48   a . The tire spectrum analysis  48   a  may then use the tire synchronized envelope  60   a  as described in more detail below. 
     Moreover, the rotating element  30   b  may be the engine of the vehicle (such as a V6 engine). Associated with the engine is a crankshaft position sensor  56   b  that can generate data that can be used to determine the rotational rate of the engine at a particular time. The crankshaft position sensor  56   b  will transmit data  54   b  to the synchronous resample  46 . The synchronous resample  46  receives the data  54   b  from the crankshaft position sensor  56   b . The crankshaft position sensor data  54   b  is then used as the sampling clock to synchronize the composite envelope  52  to generate an engine synchronized envelope  60   b  for the engine spectrum analysis  48   b . The engine spectrum analysis  48   b  may then use the engine synchronized envelope  60   b  as described in more detail below. 
     Furthermore, the rotating element  30   c  may be the driveline of the vehicle. Associated with the driveline is a vehicle speed sensor  56   c  that can generate data that can be used to determine the rotational rate of the driveline at a particular time. The vehicle speed sensor  56   c  will transmit data  54   c  to the synchronous resample  46 . The synchronous resample  46  receives the data  54   c  from the vehicle speed sensor  56   c . The vehicle speed sensor data  54   c  is then used as the sampling clock to synchronize the composite envelope  52  to generate a driveline synchronized envelope  60   c  for the driveline spectrum analysis  48   c . The driveline spectrum analysis  48   c  may then use the driveline synchronized envelope  60   c  as described in more detail below. 
     The present invention is not limited to analysis of the tires, engine and driveline but may include other types of rotating elements such as the fans or blowers in the HVAC. 
     Additionally, it is noted that the synchronous resample  46  aids in the analysis of vehicle cabin noise when the rotational rates of the rotating elements is changing over time. The frequency spectrum of the cabin sound will show many features related to the rotation of elements on the vehicle. As indicated earlier, rotating elements such as the tires, the engine, the driveline, and the HVAC blower lead to cabin noise. Most of the rotating elements in a vehicle vary in speed during the operation of the vehicle. If samples are taken at regular time intervals (regardless of vehicle operation), the time sampled spectrum will change as the rotational speed of the element changes. Synchronizing the composite envelope  52  with data  54   a ,  54   b ,  54   c  obtained from sensors  56   a ,  56   b ,  56   c  at the rotation elements  30   a ,  30   b ,  30   c  solves the problem of varying rotational speeds during operation. 
     There is a separate spectrum analysis function  48   a ,  48   b ,  48   c  performed for each rotating element  30   a ,  30   b ,  30   c  on the vehicle. In one embodiment, the spectrum analysis uses DSP based techniques and, in particular, uses the Fast Fourier Transform (FFT). FFT techniques, as applied to digitized data, provides a powerful method of signal analysis by having the ability to recognize weak signals of defined periodicity buried in a composite signal. 
     In one embodiment, the present invention uses FFT techniques to generate spectra that is “order” based as shown in FIGS. 2A-2E. The “orders” shown in the figures are defined as a sine wave cycle per revolution. It has been discovered that noise generated from rotating elements comes out at predictable orders. In other words, the amplitude of the noise is particularly predominating at certain cycles per revolution. This aids in determining whether a fault or problem exists with a particular rotating element  30   a ,  30   b ,  30   c.    
     For example, if the spectrum analysis  48   a  is designed to analyze tire faults, the spectrum analysis  48   a  may generate an “order” based spectra as shown in FIG.  2 A. Referring to FIG. 2A, a rotating tire has predictable peak amplitude spikes at orders 1-2-3-4. The peak amplitude decreases as the order increases until the harmonics are insignificant compared to systematic noise. The solid line amplitude spikes  102   a - 102   d  refer to amplitude spikes that are consistent with a rotating tire that does not have a fault or problem with balance or suspension looseness. The dashed line amplitude spikes  102   a ′- 102   d ′ refer to amplitude spikes that are consistent with a rotating tire that has a fault or problem with balance or suspension looseness. The amplitude spikes  102   a ′- 102   d ′ associated with a fault or problem are greater than the amplitude spikes  102   a - 102   d  associated with normal tire rotation. 
     If the spectrum analysis  48   b  is designed to analyze engine faults (such as a V6 engine), the spectrum analysis  48   b  may generate an “order” based spectra as shown in FIGS. 2B and 2C. Referring to FIG. 2B, an engine has predictable peak amplitude spikes at orders 1-2-3 when determining whether the engine has a balance problem. The peak amplitude decreases as the order increases until the harmonics are insignificant compared to systematic noise. The solid line amplitude spikes  104   a - 104   c  refer to amplitude spikes that are consistent with an engine that does not have a fault or problem with balance. The dashed line amplitude spikes  104   a ′- 104   c ′ refer to amplitude spikes that are consistent with an engine that has a fault or problem associated with engine balance. The amplitude spikes  104   a ′- 104   c ′ associated with a fault or problem are greater than the amplitude spikes  104   a - 104   c  associated with normal engine operation. 
     Referring to FIG. 2C, an engine also has predictable peak amplitude spikes at orders 3-4-9 when determining whether there is exhaust noise (such as a leaky muffler). The peak amplitude decreases as the order increases until the harmonics are insignificant compared to systematic noise. The solid line amplitude spikes  106   a - 106   c  refer to amplitude spikes that are consistent with an engine that does not have a fault or problem with exhaust noise. The dashed amplitude spikes  106   a ′- 106   c ′ refer to amplitude spikes that are consistent with an engine that has a fault or problem associated with exhaust noise. The amplitude spikes  106   a ′- 106   c ′ associated with a fault or problem are greater than the amplitude spikes  106   a - 106   c  associated with normal engine operation. 
     If the spectrum analysis  48   c  is designed to analyze driveline faults, the spectrum analysis  48   c  may generate an “order” based spectra as shown in FIGS. 2D and 2E. Referring to FIG. 2D, a driveline has predictable peak amplitude spikes at orders 1/n, 2/n, 3/n, where n is the numerical ratio of the gearing for the rear axle. The peak amplitude decreases as the order increases until the harmonics are insignificant compared to systematic noise. The solid line amplitude spikes  108   a - 108   c  refer to amplitude spikes that are consistent with a driveline that does not have a fault or problem with the axle alignment or differential noise. The dashed amplitude spikes  108   a ′- 108   c ′ refer to amplitude spikes that are consistent with a driveline that has a fault or problem associated with axle alignment or differential noise. The amplitude spikes  108   a ′- 108   c ′ associated with a fault or problem are greater than the amplitude spikes  108   a - 108   c  associated with normal driveline operation. 
     Referring to FIG. 2E, a driveline also has a predictable peak amplitude spikes at orders 1-2-3. The peak amplitude decreases as the order increases until the harmonics are insignificant compared to systematic noise. The solid line amplitude spikes  110   a - 110   c  refer to amplitude spikes that are consistent with a driveline that does not have a fault or problem with drive-shaft balance or a universal joint. The dashed amplitude spikes  110   a ′- 110   c ′ refer to amplitude spikes that are consistent with a driveline that has a fault or problem associated with the balance of the drive-shaft or the universal joint (such as the universal joint being loose). The amplitude spikes  110   a ′- 110   c ′ associated with a fault or problem are greater than the amplitude spikes  110   a - 110   c  associated with normal driveline operation. 
     Accordingly, the use of the spectrum analysis  48   a ,  48   b ,  48   c  provides the benefit of identifying and analyzing repeating signals. In sum, rotating elements on the vehicle have predictable repeating orders. By analyzing the amplitude spikes associated with these repeating orders, one can determine if a fault has occurred by comparing the current spectra with spectra known to represent a rotating element that is operating properly (without faults). 
     In one embodiment, the determination of whether a fault or problem exists is accomplished through a series of fault detects  50   a ,  50   b ,  50   c , associated with each rotating element  30   a ,  30   b ,  30   c . As indicated above, when analyzing the spectra of a particular rotating element on a vehicle, it has been discovered that a fault or problem can be detected if the peak amplitude is higher than its normal operation. Thus, in one embodiment, a predetermined threshold may be associated with each above-described condition. 
     The predetermined threshold can be implemented in a number of ways. For example, one embodiment includes an integration method to determine the area of the amplitude spikes for the spectra. A value for the predetermined threshold can be set that is slightly greater than the area of the amplitude spikes that would exist for a rotating element that is operating properly (without faults). In other words, the predetermined threshold should represent an acceptable value of the area of the amplitude spikes before a fault or problem is detected with a particular rotating element. If the area beneath the amplitude spikes (under analysis) is greater than the predetermined threshold, a fault exists with the rotating element. If the area beneath the amplitude spikes (under analysis) is less than the predetermined threshold, no fault exists with the rotating element. 
     In another embodiment, the predetermined threshold represents an acceptable maximum height for the amplitude spikes within the spectra. Here, the predetermined threshold is a maximum height (or value) slightly greater than a height of an amplitude spike that would exist for a rotating element that is operating properly (without faults). When the amplitude spikes (under analysis) are greater than the predetermined threshold, a fault exists with the rotating element. In either embodiment, a different predetermined threshold would need to be determined for each type of rotating element and for each type of problem that may possibly exist for that rotating element. The predetermined thresholds may be installed by the manufacturer and based on the type and design of the vehicle. The predetermined thresholds may also be determined from historical data on a fleet of vehicles of the same make and model of vehicle. 
     In sum, when the amplitude spikes are at or below a predetermined threshold, the vehicle is determined to have no faults or problems. However, when the amplitude spikes are above the predetermined threshold, the vehicle is determined to have a fault or problem. 
     It is noted that the predetermined thresholds described herein may vary based on the speed of the rotating element. Accordingly, in one implementation of the present invention, each fault detect  50   a ,  50   b ,  50   c  contains a look-up table that can be indexed by the current rotational speed of the rotating element  30   a ,  30   b ,  30   c . For this implementation, the fault detects  50   a ,  50   b ,  50   c  need to have access to the data received by the controller  26  from sensors  56   a ,  56   b ,  56   c.    
     In another implementation, the fault detects  50   a ,  50   b ,  50   c  include historical averages of acceptable amplitude spikes for a particular rotating element. For example, if the diagnosis sampler  24  is sampling the vehicle cabin at regular intervals during operation, a historical threshold average can be developed for each rotating element. In this embodiment, the controller  26  stores in memory the amplitude spikes for different rotational speeds of the rotating elements  30   a ,  30   b ,  30   c  to develop the historical threshold average. After an acceptable historical threshold average has been compiled, the fault detects  50   a ,  50   b ,  50   c  would then compare the existing amplitude spikes at a specific time to the historical threshold average at the existing rotational speed. If there was a sharp contrast between the existing amplitude spikes and the historical threshold average, then a fault or problem would be detected by the controller  26 . 
     If a fault or problem is determined by the controller  26 , a fault signal  62  may be provided to the user of the vehicle. In one embodiment, the fault signal  62  is provided to the electronic control unit (ECU)  32  of the vehicle. In this embodiment, the ECU  32  is connected to a user display panel that notifies the user of the vehicle that a fault or problem exists with a particular rotating element  30   a ,  30   b ,  30   c.    
     In another embodiment of the present invention, as shown in FIG. 3, the fault detection system  20  is used in connection with a Telematics system. The Telematics system includes a fault detection system  20  (within a vehicle  70 ) and a service center  80 . 
     The fault detection system  20  and the service center  80  may communicate with each other via wireless communications. The wireless communications are illustrated in FIG. 3 by communication arrows A and B. Communication arrow A may represent a communication by the user of the vehicle  70  asking the service center  80  for help in analyzing a problem with the vehicle  70 . Communication arrow A may also represent a communication by the fault detection system  20 . This communication could be a fault signal  62  generated by the controller  26 . Alternatively, the controller  26  may directly send the synchronized envelopes  60   a ,  60   b ,  60   c  or raw spectra data directly to the service center  80 . The service center  80  would then perform the fault detect functions. The advantage of this approach is that it allows the flexibility of changing the predetermined thresholds based on historical data from fleet studies on vehicles with the same make and model. 
     Communication arrow B may represent a communication by the service center  80  instructing or informing the user of the vehicle  70  of the type of fault or problem that may appear to exist with the vehicle  70 . In a further embodiment, the diagnosis sampler  24  may be configured to take a sample of the audio within the cabin of the vehicle on demand by the service center  80  through communication arrow B. 
     As shown in FIG. 3, in one embodiment, the communications A and B may be a cellular wireless communication that is sent through the public switched telephone network (PSTN)  82 , a cellular network  84 , and a base station antenna  86 . Those of ordinary skill in the art, having the benefit of this disclosure, will appreciate that many possible wireless communication methods may be used for communications between the vehicle  70  and the service center  80 . In one embodiment, the communications are via a cellular wireless communication such as AMPS, CDMA, GSM, or TDMA. The transmission between the vehicle  70  and the service center  80  may also be made by other wireless communications such as satellite communications. 
     Having the fault detection system  20  wirelessly connected to a service center  80  has several benefits as will be apparent from the following description. The user of a vehicle  70  having the fault detection system  20  may hear a noise or believes that the vehicle  70  is not responding properly. The user of the vehicle  70  may push a button in the vehicle  70  to establish a wireless communication with the service center  80 . The service center  80  receives the fault signals  62  from the vehicle  70  via the wireless communication device  36  (as shown in FIG.  1 ). The service center  80  may then look at the fault signals  62 . If there is a fault or problem, the service center  80  may inform the user of the vehicle  70  of the apparent problem. For example, it may appear from the fault signals  62  that there is a severe misalignment problem with the axle. The service center  80  may then instruct the user of the vehicle that the vehicle should be taken (or even towed) to a car facility immediately. Alternatively, it may appear from the fault signals  62  that there is a problem with the HVAC fan or blower. The service center  80  may then inform the user of the vehicle  70  that the problem does not appear to be serious but instruct the user to turn off the air conditioning. 
     The above description of the present invention is intended to be exemplary only and is not intended to limit the scope of any patent issuing from this application. The present invention is intended to be limited only by the scope and spirit of the following claims.