The invention relates generally to tire monitoring systems. More particularly, the invention relates to systems that predict or estimate conditions of a tire, such as wear and pressure. The invention is directed to a method of estimating conditions of a tire including tread depth or wear state, pressure and dual-tire mismatch by sensing vibrational data and analyzing the data with a machine learning technique.
Tires include various conditions that are beneficial to monitor and estimate, particularly as the tires age. Such conditions include tire wear, tire pressure, and mismatch of dual tires.
Tire wear plays an important role in vehicle factors such as safety, reliability, and performance. As the tire wears, the tread and loses material and directly affects such vehicle factors. As a result, it is desirable to monitor and/or measure the tread depth of a tire, which directly correlates to the amount of wear experienced by the tire. It is to be understood that for the purpose of convenience, the term “tread depth” shall be used, which indicates the degree of wear of the tire.
One approach to the monitoring and/or measurement of tread depth has been through the use of sensors disposed in the tire tread, which has been referred to as a direct method or approach. For example, a sensor is embedded in the tread, and as the tread depth decreases with tire wear, electrical properties of the sensor change, such as the electrical resistance. Some prior art techniques correlate the change in electrical properties to a loss of material from the tread, while other techniques correlate the change in electrical properties to a depth of material that remains on the tread. The direct approach to measuring tire depth from tire-mounted sensors has multiple challenges. Placing the sensors in an uncured or “green” tire to then be cured at high temperatures may cause damage to the sensors. In addition, sensor durability can prove to be an issue in meeting the millions of cycles requirement for tires. Moreover, the sensors in a direct measurement approach must be small enough not to cause any uniformity problems as the tire rotates at high speeds. Finally, the sensors can be expensive and add significantly to the cost of the tire.
Due to such challenges, alternative approaches have been developed, which involve prediction of tread depth over the life of the tire, including indirect estimations of the tread depth or tire wear state. These alternative approaches have experienced certain disadvantages in the prior art due to a lack of optimum prediction techniques, which reduces the accuracy and/or reliability of the tread depth or wear predictions. For example, many such techniques involve data or information that are not easily obtained or data that are not accurate under all driving conditions.
Regarding tire pressure, pneumatic tires are filled with air to a recommended inflation pressure. However, pneumatic tires are subject to air pressure losses due to puncture by nails and other sharp objects, temperature changes, and/or diffusion of air through the tire itself. Such pressure losses may lead to reduced fuel economy, tire life, and/or tire performance.
Tire pressure monitoring systems (TPMS) have been developed, which are automated systems that alert drivers and/or central systems when the air pressure in the vehicle tires drops below a predetermined level. Such systems often employ sensors in each tire that are expensive. Also, TPMS sensors may be difficult to install and may thus be installed improperly, which leads to inaccurate measurements by the sensors. Moreover, some sensors encounter reduced accuracy and/or reliability, which in turn undesirably reduces the pressure estimations generated by the system.
In addition, certain vehicles, such as heavy-duty vehicles, are equipped with dual tires, in which a pair of tires is mounted on each end of an axle, for a total of four tires on the axle. It is desirable for both tires in each pair to match one another to optimize the life and performance of the tires. For example, the tires should be of the same size, of the same outside diameter, have about the same inflation pressure and/or about the same tread depth. When both tires in each pair are not of the same size, are not of the same outside diameter, do not have about the same inflation pressure or do not have about the same tread depth, a mismatch occurs. Such mismatches are referred to as dual-tire mismatches, and may undesirably reduce the life and/or performance of one or both tires in the pair.
As a result, there is a need in the art for a method that accurately and reliably estimates conditions of a tire including tread depth, pressure and dual-tire mismatch.
According to an aspect of an exemplary embodiment of the invention, a method for estimating a condition of a tire is provided. The tire supports a vehicle and is mounted on a wheel, which is rotatably mounted on an axle. The method includes the steps of mounting a sensor on at least one of the tire, the wheel, the axle, and a component of the brake system. Vibrational data is measured with the sensor. The data from the sensor is transmitted to a processor. The data is processed in the processor and the processed data is normalized. At least one of the normalized data and pre-processed data is input into a machine learning model. A condition estimation for the tire is generated, which includes at least one of a tread depth of the tire, a pressure of the tire, and a dual tire mismatch.
The invention will be described by way of example and with reference to the accompanying drawings, in which:
Similar numerals refer to similar parts throughout the drawings.
“Axial” and “axially” means lines or directions that are parallel to the axis of rotation of the tire.
“CAN bus” or “CAN bus system” is an abbreviation for controller area network system, which is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other within a vehicle without a host computer. CAN bus is a message-based protocol, designed specifically for vehicle applications.
“Circumferential” means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction.
“Equatorial centerplane (CP)” means the plane perpendicular to the tire's axis of rotation and passing through the center of the tread.
“Footprint” means the contact patch or area of contact created by the tire tread with a flat surface as the tire rotates or rolls.
“Inboard side” means the side of the tire nearest the vehicle when the tire is mounted on a wheel and the wheel is mounted on the vehicle.
“Lateral” means an axial direction.
“Lateral edges” means a line tangent to the axially outermost tread contact patch or footprint of the tire as measured under normal load and tire inflation, the lines being parallel to the equatorial centerplane.
“Net contact area” means the total area of ground contacting tread elements between the lateral edges around the entire circumference of the tread of the tire divided by the gross area of the entire tread between the lateral edges.
“Outboard side” means the side of the tire farthest away from the vehicle when the tire is mounted on a wheel and the wheel is mounted on the vehicle.
“Radial” and “radially” means directions radially toward or away from the axis of rotation of the tire.
“Tread element” or “traction element” means a block element defined by a shape having adjacent grooves.
“Tread Arc Width” means the arc length of the tread of the tire as measured between the lateral edges of the tread.
An exemplary embodiment of the method of estimating tire conditions of the present invention is indicated at 10 and is shown in
With particular reference to
With additional reference to
Turning to
As shown in
Optionally, a second sensor 40 is mounted proximate the first sensor 38. The second sensor may be mounted to the wheel 32, the tire 12, the end 36 of the axle 18 inboardly of the wheel, or to a component of the vehicle brake system proximate the tire. The second sensor 40 may be mounted to an outboard or inboard surface of the wheel 32, to an internal or external surface of the tire 12, to an internal or external surface of the axle 18, or to a bracket attached to a disc foundation brake or a cam tube of a drum foundation brake. The second sensor 40 may be mounted to the same surface as the first sensor 38, or to a different surface that is near the surface on which the first sensor is mounted.
The second sensor 40 preferably is an acoustic sensor, which may be a microphone, or other known type of sensor for collecting acoustic signal data of the tire 12 and/or the wheel 32 as they rotate during operation of the vehicle 14. When the second sensor 40 is employed, the acoustic signal data from the acoustic sensor 40 yields vibrational data that supplements the vibrational data from the accelerometer 38.
The sensors 38 and 40 may be separate units, as shown, or may be integrated into a single unit. In addition, one or both of the sensors 38 and 40 may be integrated into a tire pressure monitoring system (TPMS) sensor, which is a sensor for measuring the temperature and pressure in the tire cavity 34, and which may be mounted to the innerliner 30 or to another component of the tire 12 or to the wheel 32.
With additional reference to
Referring to
Turning to
The processor 42 collects the data from the sensors 38, 40 and executes an analysis of the data. More particularly, with additional reference to
Referring now to
Once the vibration data 72 have been normalized, a power spectral density (PSD) 78 preferably is calculated, step 112, as the power spectral density for the data provide improved processing in the machine learning technique 74. It is to be understood that pre-processing of the vibration data 72 other than by calculation of the PSD 78 may be employed in step 112. Alternatively, depending on the vibration data 72, no pre-processing may be necessary and thus would not be employed. For the purpose of convenience, reference shall be made to the use of PSD data 78, with the understanding that step 112 may involve other pre-processing techniques or may not be performed.
The machine learning technique 74 includes inputting any PSD data 78 into a machine learning model 80, step 114. While a variety of machine learning models 80 may be employed, a first preferred model or technique is a deep learning model 82 and a second preferred model or technique is a support vector machine (SVM) algorithm or model 84. Deep learning 82 is a machine learning model or technique 80 that excels at analyzing unstructured data, including the vibration data 72 and any corresponding PSD data 78. Deep learning 82 employs algorithms that combine feature construction, modeling, and prediction into a single end-to-end system, and thus reduces unstructured data to an information-dense representation that is optimized for prediction.
A preferred technique for deep learning 82 in the method of estimating tire conditions 10 is a convolutional neural network (CNN) 86. The CNN 86 employs a multilayer neural network. The layers of the CNN 86 include an input layer, an output layer, and a hidden layer that includes multiple convolutional layers, pooling layers, fully connected layers and normalization layers. An example of an aspect of the CNN 86 is shown in
The support vector machine algorithm (SVM) 84 is an alternative machine learning model or technique 80. As shown in
Returning to
Identification (ID) information for the tire 12 may be provided in a memory unit of one or both of the sensors 38, 40 or may be stored in a separate unit, referred to as a tire ID tag. The tire ID information is transmitted to the processor 42 to enable correlation of the tire condition estimation 96 to the specific tire 12. Such tire identification enables the estimation 96 to be compared to data of historical conditions for the tire 12, step 120, to increase the fidelity or accuracy of the method 10.
For example, the storage means 58 (
To further increase the fidelity or accuracy of the method 10, additional inputs 98 may be employed. For example, weather conditions 98A may be obtained from the Internet 50 (
Optionally, the estimation 96 and/or the final predicted tread depth 130 may be classified based on the state of the vehicle 14, step 124. For example, the state of the vehicle 14 may be monitored. For example, in step 124, it may be determined if the vehicle 14 is moving, such as by obtaining a speedometer signal or a GPS calculation through the CAN bus. It may also be determined if the vehicle 14 is stationary and idling, or is stationary and running on its internal power unit, such as by obtaining engine engagement and brake engagement signals through the CAN bus. By classifying the estimation 96 and/or the final predicted tread depth 130 according to the additional criteria of the vehicle state, the accuracy of the estimation 96 and/or the final predicted tread depth 130 generated by the model 80 may be further increased.
Because the processor 42 may be electrically connected to other systems of the vehicle 14 through the CAN bus as described above, the final predicted tread depth 130 may be communicated to other control systems of the vehicle, such as an anti-lock braking system (ABS) and/or an electronic stability control system (ESC), to improve performance of such systems.
In addition, each final predicted tread depth 130 may be compared in the processor 42 to a predetermined limit. If the final predicted tread depth 130 does not satisfy the predetermined limit, a notice may be transmitted through the CAN bus or other control system to a display that is visible to an operator of the vehicle 14, to a hand-held device, such as an operator's smartphone, and/or to a remote management center. The method 10 thus may provide notice or a recommendation to a vehicle operator or a manager that one or more conditions of each tire 12 does not satisfy the predetermined limit, thereby enabling appropriate action to be taken.
Using tread depth as an example of a specific tire condition estimation 96, as shown in
Where ω is the vibration frequency, mt is the mass of the tread 22 and kt is a time-based constant. For a worn tire 12, a reduction in the mass of the tread mt causes an upward shift in vibration frequency ω.
Returning to
As described above, the estimation 96 preferably is correlated to tire identification information for each specific tire 12. Thus, when a vehicle 14 employs a dual-tire configuration with tires 12A and 12B as shown in
The machine learning model 80 employs the relationship between vibration frequency and pressure in step 114 to generate predictions 76 of pressure of the tire 12 in step 116. A resulting estimation 96 of tire pressure is output in step 118. Additional inputs 98 may be employed in the model 80 in step 122, and a comparison to historical conditions may be made in step 120 to obtain a final predicted tread depth 130, which may be classified based on the vehicle state in step 124. The resulting final predicted tread depth 130 thus is an accurate estimate that may be transmitted to the vehicle control systems and/or to the vehicle operator.
In step 126, the method of estimating tire conditions 10 may identify a pressure-related mismatch between dual tires 12A and 12B. More particularly, in step 126, a tire pressure estimation 96 for the first tire 12A is compared to a tire pressure estimation for the second tire 12B. If a difference in the estimations 96 exceeds a predetermined threshold, a mismatch notice may be generated and transmitted as described above. For example, if the pressure estimation 96 yields a difference that is greater than about 5 pounds per square inch between the first tire 12A and the second tire 12B, a pressure mismatch notice may be generated.
Optionally, the method of estimating tire conditions 10 may employ the vibrational data from the sensors 38, 40 to determine additional conditions of the tire 12, the wheel 32 and/or the vehicle 14. For example, the vibrational data from the sensors 38, 40 may be processed according to the steps described above to determine potential conditions including crown separation of one or more tires 12, irregular tire wear, flatspotting of the tires, imbalance of the wheels and/or tires, and/or potential brake component issues.
In this manner, the method of estimating tire conditions 10 of the present invention provides estimates 96 of conditions of the tire 12 by collecting vibrational data of the tire and/or the wheel 32 and analyzing the data with a machine learning technique 74. The method of estimating tire conditions 10 of the present invention accurately and reliably estimates conditions of the tire 12 including tread depth, pressure and dual-tire mismatch.
It is to be understood that the method of the above-described tire condition estimation system 10 may be altered or rearranged, or components or steps known to those skilled in the art omitted or added, without affecting the overall concept or operation of the invention. For example, the tire condition estimation system 10 finds application on any type of tire 12.
The invention has been described with reference to a preferred embodiment. Potential modifications and alterations will occur to others upon a reading and understanding of this description. It is to be understood that all such modifications and alterations are included in the scope of the invention as set forth in the appended claims, or the equivalents thereof.
Number | Date | Country | |
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62948880 | Dec 2019 | US |