Patent Description:
A gas turbine engine typically includes a fan section, a compressor section, a combustor section, and a turbine section. Air moves into the engine through the fan section. Airfoil arrays in the compressor section rotate to compress the air, which is then mixed with fuel and combusted in the combustor section. The products of combustion are expanded to rotatably drive airfoil arrays in the turbine section. Rotating the airfoil arrays in the turbine section drives rotation of the fan and compressor sections. The compressor section and turbine section each have multiple stages of blades that rotate about a central axis and multiple stages of vanes that are stationary relative to the central axis.

Many relatively large turbine engines, including turbofan engines, may use magnetic speed sensors to measure the speed of rotating components for the purposes of control and fault detection. An air turbine starter (ATS) is an example of such machinery. An ATS is used to initiate gas turbine engine rotation. The ATS is typically mounted on the accessory gearbox which, in turn, is mounted on the engine or airframe. Active operation of the ATS may occur for a minute or so at the beginning of each flight cycle, along with occasional operation during engine maintenance activities. An ATS encounters large mechanical stresses while converting inlet air pressure into output torque for initiating engine rotation. Each start process causes wear on internal components, such as bearings, shafts, and gears. <CIT> relates to a shaft break detection system. <CIT> relates to a vibration detector. <CIT> relates to a gearbox condition monitoring system.

According to the invention, a method of monitoring a rotating component is provided in claim <NUM> and includes gathering an electrical signal from a sensor arranged adjacent a rotating component of an assembly. The electrical signal is transformed from a time domain into a frequency domain. The electrical signal is compared to an expected signal.

The method includes determining whether there is a fault in the assembly based on the comparison to the expected signal.

The method includes determining a portion of the assembly containing the fault based on the comparison to the expected signal.

In a further embodiment of any of the above, the method includes determining whether the fault corresponds to an issue with a gear system, shaft, or bearing.

In a further embodiment of any of the above, a component of the assembly is replaced or repaired when a fault is detected.

In a further embodiment of any of the above, the comparing step comprises comparing an amplitude of the electrical signal across several frequencies with the expected signal.

Any high amplitude pulses are removed from the electrical signal before the transforming step.

In a further embodiment of any of the above, the rotating component is a gear that has at least one tooth.

In a further embodiment of any of the above, the high amplitude pulses corresponds to at least one tooth passing the sensor.

In a further embodiment of any of the above, the gear has a plurality of teeth spaced about a circumference of the gear.

In a further embodiment of any of the above, the assembly is an air turbine starter.

In a further embodiment of any of the above, the gathering step comprises gathering data at a frequency of at least twice a top rotating frequency of the rotating component.

In a further embodiment of any of the above, the gathering step comprises gathering data at a frequency of at least about <NUM>.

In a further embodiment of any of the above, the gathering step comprises gathering an electrical signal from a speed range of the rotating component.

In a further embodiment of any of the above, the gathering step comprises gathering the electrical signal for a period of time corresponding to a startup of the component operating through all rotational speed conditions.

In a further embodiment of any of the above, the sensor is a magnetic speed sensor.

In a further embodiment of any of the above, the transforming step comprises performing a Fourier transform.

In another exemplary embodiment, a system for monitoring a rotating component includes a magnetic speed sensor arranged adjacent to a rotating component of an air turbine starter. A processor is configured to gather a signal from the magnetic speed sensor and transform the signal from a time domain into a frequency domain.

In a further embodiment of any of the above, the processor is configured to generate a plot of the signal in the frequency domain.

In a further embodiment of any of the above, the processor is configured to remove any high amplitude peaks in the signal before transforming the signal into the frequency domain.

The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings.

<FIG> shows an exemplary air turbine starter (ATS) <NUM> for a gas turbine engine. The ATS <NUM> may be mounted on an accessory gearbox which, in turn, is mounted on an engine or airframe. The engine may be a gas turbine engine, for example. Gas turbine engines are known, and may generally include a fan section, a compressor section, a combustor section and a turbine section, among other components. The gas turbine engine may be a two-spool turbofan gas turbine engine, a three-spool architecture, a direct drive turbofan, an industrial gas turbine (IGT), or any gas turbine engine as desired.

It should be appreciated that the present application is not limited to use in conjunction with a specific type of rotating machine. Thus, although the present application is, for convenience of explanation, depicted and described as being implemented in an air turbine starter, the present disclosure may be utilized elsewhere in a gas turbine engine, such as with the fan, high pressure compressor, low pressure compressor, gearbox, or other rotating components. This disclosure may also be implemented in numerous other machines including, but not limited to, a gas turbine engine, an auxiliary power unit, a turbo charger, a super charger, an air cycle machine, an alternator, an electric motor, an electric generator, an integrated constant speed drive generator and gearboxes of various types.

The example ATS <NUM> has a speed sensor <NUM> that measures a speed of a rotating component within the ATS <NUM>. In one example, the speed sensor <NUM> measures the speed of a gear assembly <NUM> (shown in <FIG>). A processing system <NUM> may be connected to the ATS <NUM> and/or the speed sensor <NUM> to collect data from the speed sensor <NUM>. In one example embodiment, the processing system <NUM> includes a portable computer and data acquisition system that is connected to the ATS <NUM> and/or speed sensor <NUM> between flights. In another example, the processing system <NUM> is on board the aircraft.

The processing system <NUM> may generally include a processor, which may be a dedicated microprocessor or another computing device. The processing system <NUM> may include memory associated with the processor. In some example embodiments, the memory includes computer-executable instructions that cause the processor to operate for purposes of processing electrical signal data. In some example embodiments, the memory contains information regarding various features or characteristics of the ATS <NUM>, such as a number of gear teeth and/or expected vibration behavior. In some embodiments, a first processing system is located on the aircraft, and calculates a speed of the ATS <NUM>, and a second processing system <NUM> is connected intermittently to calculate additional parameters.

<FIG> shows an exemplary gear system <NUM> within the ATS <NUM>. In this example, the gear system <NUM> is a planetary gear system having a sun gear <NUM>, planet gears <NUM>, and a ring gear <NUM> rotatable about a shaft. The ring gear <NUM> has one or more external teeth <NUM> extending radially outward from a surface of the ring gear <NUM>.

<FIG> shows a portion of the gear system <NUM>. The speed sensor <NUM> is arranged adjacent to the ring gear <NUM>. The speed sensor includes a magnet, and picks up on changes in the magnetic field when the teeth <NUM> pass by. In this example, the ring gear <NUM> has four teeth <NUM> equally spaced about the circumference of the ring gear <NUM>. Thus, the speed sensor <NUM> can determine the speed of rotation of the ring gear <NUM> by the number of times teeth <NUM> pass by. Although four teeth <NUM> are shown, rotating components with more or fewer teeth <NUM> may come within the scope of this disclosure. In some examples, the teeth <NUM> may be unequally spaced to help with tooth indexing. The sensor <NUM> gathers an electrical signal based on the changing magnetic fields of the gear surface <NUM> passing by, including teeth <NUM>. Output voltage from the sensor <NUM> is primarily a function of an air gap G between the tooth <NUM> or gear <NUM> and the sensor <NUM> and the surface speed of the gear <NUM>. As a result, the sensor <NUM> also responds to changes in distance between the surface <NUM> and the sensor <NUM>, such as passing teeth <NUM> and vibrations of the gear assembly <NUM>.

<FIG> is an example of the electrical signal as a result of teeth <NUM> passing the sensor <NUM>. This plot shows the output signal, or amplitude, in volts on the vertical axis over time in seconds on the horizontal axis. The large peaks <NUM> correspond to a tooth <NUM> passing the sensor <NUM>. In one example, the peaks <NUM> are greater than about <NUM> V. <FIG> is a portion of an example electrical signal <NUM> from the sensor <NUM> which shows undesirable signal content between teeth <NUM>, caused by a combination of vibration and electrical noise.

<FIG> is a portion of the electrical signal <NUM> over the ATS <NUM> startup cycle, where the tooth passing waveforms have been omitted using digital post-processing methods. In this example, it takes between about <NUM> and <NUM> seconds for the ATS <NUM> to ramp up from <NUM> RPM to a full speed. The digitally processed signal <NUM> reveals the amplitude of the noise signals <NUM> between the peaks <NUM>. Some of this noise <NUM> corresponds to vibration of the gear <NUM>. For example, as the ring gear <NUM> vibrates, the distance from the ring gear <NUM> to the sensor <NUM> varies, causing the shown varying amplitude in the signal <NUM>. The noise <NUM> is the signal with an amplitude less than the peaks <NUM>. In one example, the noise <NUM> has an amplitude of less than about <NUM> V. In a further example, the noise <NUM> has an amplitude of less than about <NUM> V.

<FIG> is a chart of the calculated speed of the ATS <NUM> in RPM over time. The plot is generated based on the detection of peaks <NUM> and the known space between the teeth <NUM>. This plot shows a start cycle for the ATS <NUM>. The speed of the ATS <NUM> starts at <NUM> RPM, and ramps up to about <NUM> RPM over a period ofbetween about <NUM> and <NUM> seconds. Some turbine starters or other rotating components may have a longer ramp up period and/or different operating speeds.

<FIG> is a three dimensional plot <NUM> of the electrical signal <NUM> in the frequency domain. The electrical signal of <FIG> shows amplitude and speed over time, respectively. Thus, both amplitude and speed are functions of time, and <FIG> show a time domain signal. This signal is transformed into the frequency domain to view the frequencies that make up the signal. In one example, a Fourier Transform is used to convert the time domain signal into the frequency domain. A Fourier Transform decomposes a function of time into frequencies. The transformation into the frequency domain may be done using the known Fast Fourier Transform (FFT) algorithm.

The plot of <FIG> shows the amplitude over time and across frequencies. The signal <NUM> must be gathered for all speeds of the ATS <NUM>. For the example ATS <NUM>, the ramp up period is about <NUM> seconds. Thus, <NUM> seconds of signal <NUM> must be gathered to collect data for all speeds of the ATS <NUM>. For other components, the component may go through all speeds in a shorter time, and thus a shorter time for the signal may be sufficient. The sensor <NUM> should be sampled at a rate of at least twice the frequency of the highest expected vibration frequency of the rotating components. This ensures sufficient data in the noise <NUM> of the signal <NUM> to provide meaningful information about vibrations of the ATS <NUM> in the frequency domain. In one example, the sensor <NUM> is sampled at a rate of at least about <NUM>. In a further example, the sensor <NUM> is sampled at a rate of at least about <NUM>. In some examples, the sensor <NUM> is sampled at a rate of between <NUM> and <NUM>,<NUM>.

The frequency data of plot <NUM> provides information about the ATS <NUM>. The various noise contributing sources in the plot <NUM> provide information about particular components within the ATS <NUM>. The components within an ATS <NUM> have expected vibration behaviors, and deviations from these behaviors within plot <NUM> may indicate faults or unacceptable wear in the ATS <NUM>. For example, there is a group of peaks <NUM> at a very low frequency, between about <NUM> and <NUM> for the entire length of the signal <NUM>. This group <NUM> corresponds to noise contributions from the ring gear <NUM>, bearings, and output shaft, based on the detected frequencies. A series of peaks <NUM> at about <NUM> may be indicative of system or sensor resonance, since they are all about the same frequency for the entire time signal and are not a function of rotational speed. A series of peaks <NUM> corresponds to the meshing of the planet gear <NUM> and the sun gear <NUM>. The series of peaks <NUM> corresponds to the meshing of the ring gear <NUM> and the planet gear <NUM>.

Based on any unexpected peaks, a fault or abnormality in the ATS <NUM> may be detected. In some examples, a fault may indicate a component failure, a fault may be a defect in the component, a fault may be an abnormality in the component, or a fault may indicate wear on the component that suggests it may fail. That is, a fault or unacceptable wear detected may predict a failure of a component in the ATS <NUM> before it occurs. Unexpected peaks are any that do not show up on a plot for a good ATS <NUM> that is known to have no faults or defects. The location of any unexpected peaks may indicate which component within the ATS <NUM> has a fault. For example, the plot <NUM> may reveal faults associated with the sun gear <NUM>, ring gear <NUM>, planet gear <NUM>, shaft <NUM>, or a bearing in the ATS <NUM>. The plot <NUM> is compared to an expected signal that would be based on a healthy ATS <NUM> with no defects. Each individual frequency is analyzed to identify any deviance from the expected signal.

<FIG> summarizes an example method <NUM> of monitoring a rotating component. A processing system <NUM> collects data, and in particular an electrical signal <NUM>, from the sensor <NUM> at <NUM>. In one example, this occurs between flights during engine maintenance. The processing system <NUM> may collect data while the component is running, or may collect data stored previously. In some examples, the processing system <NUM> removes high amplitude pulses from the signal <NUM> at <NUM>. These pulses correspond to the teeth <NUM> passing the sensor <NUM>, and are used to calculate speed. In addition to speed information, this signal <NUM> contains supplemental information regarding vibrations of the ATS <NUM>. The signal <NUM> is then transformed from the time domain to the frequency domain at <NUM>. According to the invention, the processing system <NUM> generates a three dimensional plot <NUM> of time, frequency, and amplitude at this step. In some embodiments, the system <NUM> may generate another type of plot that displays time, frequency, and amplitude, such as a two dimensional plot with varying colors indicating frequency or amplitude over time at <NUM>.

The frequency domain signal is then compared to an expected signal at <NUM>. The three dimensional plot <NUM> is analyzed to identify irregular or unexpected peaks in comparison with an expected signal at <NUM>. Irregular peaks in the plot <NUM> suggest a component is vibrating more than expected, which may indicate a fault in the component. The three dimensional plot <NUM> is further analyzed to identify which component may have a fault at <NUM>. Irregular peaks at particular times and frequencies may indicate a fault with a particular component within the ATS <NUM>. If a fault in a particular component is detected, the component or the entire ATS <NUM> may be replaced at <NUM>. Replacing a component may include repairing the component. This method provides a way to monitor health over time and to predict failures of the ATS <NUM>.

In one example, this method <NUM> is used during ground operations. For example, the method <NUM> may be performed by hooking the processing system <NUM>, such as a portable computer, to the sensor <NUM>, and starting up the ATS <NUM>. The portable computer then gathers and stores the electrical signal <NUM> generated by the sensor <NUM> for a period of time, such as <NUM>-<NUM> seconds. This method would be performed between flights as part of the engine maintenance. In another example, a data storage component is located on the aircraft that stores the electrical signal <NUM> gathered during a flight. This electrical signal data is then transferred to the processing system <NUM> after the flight, and the signal <NUM> is analyzed according to the above described method <NUM>. In another example, a processing system <NUM> is located on the aircraft in addition to the onboard data collection system. The processing system <NUM> may be either dedicated or integrated with control or diagnostic electronics on the aircraft. The signal <NUM> is analyzed at each usage of the component, or at regular intervals of usage, using this method <NUM>.

Known air turbine starters <NUM> encounter large mechanical stresses while initiating engine rotation. Each start process causes wear on internal components, such as bearings, shafts, and gears. Wear may result in failed engine starts, flight delays and/or flight cancellations. Known ATS maintenance methods include keeping track of the length of time and/or number of start cycles an ATS <NUM> has done, and replacing components after a certain number of operating hours. If an ATS component fails before the expiration time, it may not be caught until a failed engine start. The disclosed monitoring method <NUM> may predict the failure of the air turbine starter <NUM> and/or any components of the ATS <NUM>, and enables the premature replacement of the unit at a more conveniently scheduled time. The disclosed method of analyzing and monitoring a rotating component relies on the electrical signal generated by the existing speed sensors on the component, expanding the capabilities of existing sensor technology. The method monitors internal vibrations in the ATS, and enables operators to monitor individual components within the ATS without having to disassemble the ATS for inspection.

Claim 1:
A method of monitoring a rotating component, comprising:
gathering an electrical signal from a sensor arranged adjacent a rotating component of an assembly;
transforming the electrical signal from a time domain into a frequency domain; and
comparing the electrical signal to an expected signal;
determining whether there is a fault in the assembly based on the comparison to the expected signal;
determining a portion of the assembly containing the fault based on the comparison to the expected signal; and/or comprising determining whether the fault corresponds to an issue with a gear system, shaft, or bearing; and
wherein the rotating component is a gear having at least one tooth;
wherein the gathering step comprises gathering data at a frequency of at least about <NUM>; and/or wherein the gathering step comprises gathering an electrical signal from a speed range of the rotating component; and/or wherein the gathering step comprises gathering the electrical signal for a period of time corresponding to a startup of the component operating through all rotational speed conditions; and
creating a three-dimensional plot of the electrical signal including time, frequency and amplitude of the signal, and characterized by removing any amplitude pulses corresponding to a tooth passing the sensor from the electrical signal before the transforming step.