FAULT DETECTION TECHNIQUE FOR A BEARING

Systems and methods are provided for fault detection in a component of a machine during operation. Vibration data is acquired based on a vibration signal output from a sensor associated with the component. The vibration data is analyzed with at least two machine learning models to predict a condition of the component.

BACKGROUND

In vehicles, particularly work vehicles such as agricultural vehicles and construction vehicles, a bearing failure can cause significant collateral damage to other components. No symptoms may be evident with a failing bearing. Accordingly, it may be impractical to discover a problem prior to failure. For example, manual inspection of the bearing is not a routine maintenance activity and is labor intensive.

SUMMARY

In one implementation, a system is provided. The system includes a sensor configured to a signal indicative of a vibration within a component of a vehicle in operation. The system also includes a controller, which is configured to log vibration data corresponding to the signal received from the sensor, generate a first prediction of a health condition of the component with a first model based on the vibration data, generate a second prediction of the health condition of the component with a second model based on the vibration data, and output a health condition of the component based on the first prediction and the second prediction.

In another implementation, a method for a vehicle is provided. The method includes acquiring vibration data from a sensor associated with a component of the vehicle. The method also includes generating a first prediction of a health condition of the component with a first model based on the vibration data and generating a second prediction of the health condition of the component with a second model based on the vibration data. The method includes outputting the health condition of the component based on the first prediction and the second prediction.

In still another implementation, a non-transitory computer-readable storage medium having stored thereon computer-executable instructions is provided. The instructions, when executed by a processor, configure the processor to log vibration data from a sensor associated with a bearing of a hydrostatic motor. The instructions further configure the processor to generate a first prediction of a health condition of the bearing with a first model based on the vibration data and generate a second prediction of the health condition of the bearing with a second model based on the vibration data. The instructions further configure the processor to output the health condition of the bearing based on the first prediction and the second prediction.

DETAILED DESCRIPTION

As described above, a fault in a bearing, in a machine for example, cannot be readily identified prior to a failure event, which may cause damage to other components. There are often no symptoms of the fault during operation of the machine. In accordance with various implementations, a fault detection technique is described that provides a preliminary indication of a potential fault prior to failure. This technique functions while the machine is in operation. A sensor outputs vibration data for a component, such as a bearing. A controller analyzes the vibration data to determine a condition of the bearing. In one aspect, the analysis involves utilizing one or more machine learning models to predict the condition of the bearing. The vibration data is regularly acquired and analyzed while the machine is operated. An operator may be alerted when a predicted condition of the bearing indicates a potential fault. Accordingly, the component may be inspected, repaired, and/or replaced prior to a catastrophic failure that causes collateral damage to other components thereby increasing repair costs and machine downtime.

Referring initially toFIG. 1, a fault detection system100is illustrated. The system100may be included in or utilized by an agricultural vehicle110, such as a tractor, to monitor a component and identify a potential fault before a failure of the component occurs. According to an example, the monitored component can be a bearing122of a hydrostatic motor120of agricultural vehicle110. While the exemplary implementation ofFIG. 1is described with respect to agricultural vehicle110, it is to be appreciated the aspects described herein are applicable to other vehicles such as construction vehicles, or other machines having a bearing or other component similar to bearing122of hydrostatic motor, which may suffer similar faults.

A sensor140acquires vibration data associated with bearing122and streams the vibration data to a controller130for analysis to detect a potential fault. Controller130may include a microcontroller, a system-on-a-chip, an FPGA, or other logic circuitry. For instance, controller130may include a processor, a computer memory (e.g. a non-transitory computer-readable storage medium), and interfaces to acquire inputs and send signals to various components of system100. The memory may include computer-executable instructions that configure the processor to carry out the functions of controller130in system100. In some implementations, the controller130may be an electronic control unit such as an engine control unit (ECU) or the like. As such, the controller130may include a microcontroller, memory (e.g., SRAM, EEPROM, Flash, etc.), inputs (e.g., supply voltage, digital inputs, analog inputs), outputs (e.g., actuator inputs, logic outputs), communication interfaces (e.g., bus transceivers), and embedded software.

According to an example, controller130utilizes vibration data from sensor140to determine the health condition of bearing122. The controller130may utilize one or more machine learning models to predict the health condition based on the vibration data acquired by sensor140. For instance, according to one implementation, the controller130may utilize a first model and a second model that respectively predict health conditions of bearing122based on vibration data. The controller130may generate a hybrid condition of bearing122based in part on the two individual health predictions from the first model and the second model.

According to a further implementation, controller130may analyze the vibration data in dependence of the speed of the hydrostatic motor120(e.g. a rotational speed), which by extension is a speed associated with the bearing122. In addition to vibration data, controller130may also acquire speed data from tachometer150. The controller130may evaluate vibration data corresponding to a stable speed state of motor120. In another example, vibration data may be weighted based on speed data. For instance, vibration data may provide a weaker signal at low speeds and a stronger signal at high speeds. At either extreme, a possibility of false negatives (i.e., failing to detect faults) or false positives (i.e., detecting faults that do not exist) can be reduced by compensating for effects of high or low speed on vibration data.

A determined health condition, particularly a negative condition (e.g. a condition indicative of damage, pending failure, or other fault in need of attention), can be output via an operator interface160(e.g. an in-cab indicator or display). In other examples, the health condition may be transmitted to a remote system170to support remote monitoring and/or logging of the condition of bearing122. Still further, as described later, there may be temporal or speed dependencies for the predicted health condition. Accordingly, the output via the operator interface160may not be an instantaneous output of a prediction, but rather a processed output to account for time or speed conditions. For example, a temporal fusion of the predicted health condition over time may be applied before output is provided via operator interface160. In another implementation, a time average or a sliding window is utilized to smooth output over time.

Turning toFIG. 2, an exemplary implementation of a fault detection program200is illustrated. Fault detection program200may be implemented by computer-executable instructions executed by controller130. It is to be appreciated, however, that fault detection program200may be executed remotely from the agricultural vehicle110. For instance, speed and/or vibration data acquired at the agricultural vehicle110may be transmitted to another computing device (e.g. remote system170, a mobile device, or other computer separate from vehicle110) for analysis.

As shown inFIG. 2, fault detection program200includes an input module202that obtains speed data204and vibration data206. According to an example, input module202may log speed data204and vibration data206for a configurable period of time, T, at intervals, Q, where T and Q are parameters having time-based units such as seconds. In other words, input module202may log data for T seconds every Q seconds.

In another aspect, input module202may process the data for analysis. For example, input module202can detect a stable speed state of agricultural vehicle110based on speed data204and select a portion of vibration data204corresponding to the stable speed state for further analysis. That portion of vibration data204is evaluated by a first model208and a second model210. The first model208and the second model210respectively output a condition of a component (e.g. bearing122) based on the portion of vibration data204. In one example, the first model208may be a convolutional neural network and the second model210may be a threshold model. However, it is to be appreciated that alternative learning models may be utilized to provide independent determinations of the condition based on vibration data204.

The individual determinations by first model208and second model210may be combined and provided to output module212, which generates condition214output to a computing device (e.g. remote system, mobile device, etc.) or to an operator interface (e.g. in-cab display or indicator). Further, the output module212may refine the combined condition determination based on temporal and/or speed dependencies. The output module212, depending on the condition determined, may provide feedback to input module202to alter data collection. For instance, data may be logged more frequently if a deteriorating condition is detected.

FIG. 3illustrates a fault detection method300, which may be implemented by system100and/or program200. As shown inFIG. 3, method300includes two stages—an offline stage302and an online stage306. The offline stage302may occur prior to deployment of the system100and/or program200in agricultural vehicle110. The online stage306, for example, may be carried out during the operation of the agricultural vehicle110.

In the offline stage302, at step304, a first model and a second model are trained. The training process is described in greater detail below, but a result of this process includes trained first and second models capable of predicting the health condition based on vibration data.

After the models are trained, the online stage306of method300can be carried out. The online stage306may begin at step308where vibration and speed data is logged. In an example, logging may occur for T seconds in each interval, where an interval is Q seconds. The parameter Q may depend on a computational performance of a controller (e.g. controller130) and/or a health condition of a bearing (e.g. determined in a prior iteration).

At310, a stable speed detection step occurs. In some instances, vibration data may have more predictive ability when the agricultural vehicle is in a stable speed state. In one example, the speed and vibration data collected in step306may be divided into two subsets. In some examples, the two subsets may be of equal size. A mean speed for each subset is determined and an absolute value of a difference therebetween is compared to a threshold. If the difference is below the threshold, a stable speed state is detected and processing may continue. In some examples, further processing may be conducted with one of the two subsets, or the entire set may be utilized. In addition, an average of the vibration data may be calculated to verify a connection to the sensor. For instance, a zero average may indicate a problem with the sensor.

After detecting a stable speed and verifying vibration data, a health condition can be determined. At step312, the first model is employed to determine a first prediction based on the vibration data. At314, which may occur in parallel to step312, the second model is employed to determine a second prediction based on the vibration data. The first and second predictions can be combined to determine a health condition. For example, when the first and second predictions indicate no damage, then the combined health condition is also no damage. In another example, the first model may be a convolutional neural network and the second model may be a threshold model. According to this example, a low confidence situation may occur when the convolutional neural network indicates a condition other than no damage, but the threshold model indicates no damage. In this circumstance, the combined health condition can be output as the condition predicted by the convolution neural network, but with a low confidence disclaimer. Finally, in other permutations, the combined health condition can be a worst case between the first prediction and the second prediction.FIG. 8graphically illustrates exemplary rules for combining the predictions as described above.

After a combined health condition is determined, the condition may be refined at step316. For instance, a health condition may be refined based on observations of a temporal and/or speed dependency of the health condition. A rapid change of a health condition prediction over time is not physically meaningful and, generally, predictions that are more recent are more relevant. Accordingly, a temporal fusion technique can be applied to refine the health condition such that predictions that are more recent are given more weight. Mathematically, this technique can be represented by the following:

Further, it has been observed that vibration data at low speeds may provide a weak signature, which may lead to missed detections. At high speeds, the vibration data may provide a strong signature leading to false positives. Accordingly, the health condition may be refined to allocate a greater weight to vibration data that corresponds to a speed closer to a mean speed. Mathematically, this relationship can be represented by the following

After refinement, a maintenance decision may be output at320based on the health condition. For example, if light damage is predicted, replacement of the part may be scheduled soon. If heavy damage is predicted, the vehicle may be removed from service and repaired immediately. In addition, the health condition may be output to an operator via an operator interface as described above. To avoid a rapidly changing output to the operator, the operator interface may indicate the health condition after refinement instead of an instantaneous prediction.

In addition, at step318, data collection parameters may be updated. For example, the parameter Q may be modified based on a predicted health condition. If a change from no damage to light damage is detected, more frequent data collection may occur.

Turning toFIG. 4, a training method400for a model employable in the fault detection method ofFIG. 3, the fault detection program ofFIG. 2, or the fault detection system ofFIG. 1is depicted. At402, training data covering a set of classes is acquired. In an example, the training data may include vibration data corresponding to bearings having conditions matching prediction classes to be output by the model. For instance, the classes may include no damage, light damage, and heavy damage.

At step404, an envelope analysis is performed on the training data to generate respective envelope spectra for the training classes. Referring briefly toFIG. 7, an exemplary envelope spectrum700is shown. At406, one or more sub-bands are extracted from the envelope spectrum. For example, the sub-bands may correspond to a predefined number of frequency sub-bands centered at fault characteristic frequencies and harmonics. Referring again toFIG. 7, sub-bands702-714are extracted from envelope spectrum700. At408, vibration data (e.g. vibration amplitudes) within the extracted sub-bands are fed as input to a model for training.

Turning toFIG. 5, illustrated is an exemplary process for training a convolutional neural network (CNN). As shown inFIG. 5, the training process involves acquiring training data, performing an envelope analysis, and extracting characteristic sub-bands. With the training data, the CNN may be established according to a given set of network hyperparameters and then trained. The trained CNN may be tested with a validation dataset (e.g. via cross-validation). The hyperparameters may be tuned and/or optimized by iterations of the process until a desired performance is achieved. After training, the CNN may be deployed to process vibration data in near real-time from an operating motor.

FIG. 6illustrates an exemplary process for training a threshold model. As shown inFIG. 6, the training process involves acquiring training data, performing an envelope analysis, and extracting characteristic sub-bands. Subsequently, a parameter study is performed to identify one or more thresholds in the underlying data, depending on a number of classes in an output set. For instance, with three classes in the output set (e.g. no damage, light damage, and heavy damage), two thresholds may be established during training. A first threshold marks a transition between no damage and light damage. A second threshold indicates a change from light damage to heavy damage.

In accordance with an implementation, a system is described herein that includes a sensor configured to a signal indicative of a vibration within a component of vehicle in operation. The system further includes a controller. The controller is configured to: log vibration data corresponding to the signal received from the sensor; generate a first prediction of a health condition of the component with a first model based on the vibration data; generate a second prediction of the health condition of the component with a second model based on the vibration data; and output the health condition of the component based on the first prediction and the second prediction.

According to various examples, the first model is a convolutional neural network, the second model is a threshold model, and the component is a bearing of a hydrostatic motor. Moreover, the controller is further configured to acquire a speed signal indicative of a speed associated with the component and log speed data based on the speed signal together with the vibration data. In another example, the controller is further configured to analyze the speed data to detect a stable speed state, select a portion of the vibration data corresponding to the stable speed state, and process the portion of the vibration data selected with the first and second models. In another example, the controller is further configured to refine the health condition of the component according to at least one of a temporal dependency or a speed dependency of the vibration data. In yet another example, the controller is further configured to: acquire training data; generate an envelope spectrum based on the training data; extract one or more frequency sub-bands from the envelope spectrum, the one or more frequency sub-band being characteristic frequencies of faults; train the first model with input training data corresponding to the one or more frequency sub-bands; and train the second model with the input training data corresponding to the one or more frequency sub-bands. Still further, the controller can be configured to modify logging of vibration data based on the health condition output.

According to another implementation, a method for a vehicle is described. The method may include acquiring vibration data from a sensor associated with a component of the vehicle. The method may also include generating a first prediction of a health condition of the component with a first model based on the vibration data. Further, the method may include generating a second prediction of the health condition of the component with a second model based on the vibration data. The method may further include outputting the health condition of the component based on the first prediction and the second prediction.

In various example of the method, the first model is a convolutional neural network and the second model is a threshold model. The method may also include acquiring speed data associated with the component, determining a stable speed state of the component based on the speed data, selecting a portion of the vibration data corresponding to the stable speed state, and processing the portion of the vibration data selected with the first and second models. Moreover, the method can include refining the health condition of the component according to at least one of a temporal dependency or a speed dependency of the vibration data. Still further, the method may also include acquiring training data; generating an envelope spectrum based on the training data; identifying one or more sub-bands from the envelope spectrum that are relevant for fault detection; training the first model with portions of the training data corresponding to the one or more sub-bands identified; and training the second model with the portions of the training data corresponding to the one or more sub-bands identified.

In yet another implementation, a non-transitory, computer-readable storage medium is described. The computer-readable storage medium stores computer-executable instructions that, when executed by a processor, configure the processor to: log vibration data from a sensor associated with a bearing of a hydrostatic motor; generate a first prediction of a health condition of the bearing with a first model based on the vibration data; generate a second prediction of the health condition of the bearing with a second model based on the vibration data; and output the health condition of the bearing based on the first prediction and the second prediction.

According to various examples, the first model is a convolutional neural network and the second model is a threshold model. The computer-readable storage medium may also store instructions that configure the processor to: acquire speed data associated with a rotational speed of the hydrostatic motor; and log the speed data together with the vibration data. The computer-readable storage medium can further store instructions that configure the processor to: analyze the speed data to detect a stable speed state of the hydrostatic motor; select a portion of the vibration data corresponding to the stable speed state; and process the portion of the vibration data selected with the first and second models.

According to further examples, the computer-readable storage medium may store instructions that configure the processor to refine the health condition of the bearing according to at least one of a temporal dependency or a speed dependency of the vibration data. The medium can further store instructions that configure the processor to: acquire training data; generate an envelope spectrum based on the training data; identify one or more sub-bands from envelope spectrum indicative of faults in the bearing; train the first model with portions of the training data corresponding to the one or more sub-bands identified; and train the second model with portions of the training data corresponding to the one or more sub-bands identified. The computer-readable medium can further store computer-executable instructions that configure the processor to modify logging of vibration data based on the health condition output.

Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. Of course, those skilled in the art will recognize many modifications may be made to this configuration without departing from the scope or spirit of the claimed subject matter.

Also, although the disclosure has been shown and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art based upon a reading and understanding of this specification and the annexed drawings. The disclosure includes all such modifications and alterations and is limited only by the scope of the following claims. In particular regard to the various functions performed by the above described components (e.g., elements, resources, etc.), the terms used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (e.g., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary implementations of the disclosure.

In addition, while a particular feature of the disclosure may have been disclosed with respect to only one of several implementations, such features may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms “includes,” “having,” “has,” “with,” or variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.”