The invention relates generally to tire monitoring systems. More particularly, the invention relates to systems that collect tire parameter data. The invention is directed to a system and method for estimating tire wear based upon multiple predictors to provide an accurate and reliable estimation.
Tire wear plays an important role in vehicle factors such as safety, reliability, and performance. Tread wear, which refers to the loss of material from the tread of the tire, directly affects such vehicle factors. As a result, it is desirable to monitor and/or measure the amount of tread wear experienced by a tire.
One approach to the monitoring and/or measurement of tread wear has been through the use of wear sensors disposed in the tire tread, which has been referred to a direct method or approach. The direct approach to measuring tire wear 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 wear sensors. In addition, sensor durability can prove to be an issue in meeting the millions of cycles requirement for tires. Moreover, wear sensors in a direct measurement approach must be small enough not to cause any uniformity problems as the tire rotates at high speeds. Finally, wear sensors can be costly and add significantly to the cost of the tire.
Due to such challenges, alternative approaches were developed, which involved prediction of tread wear over the life of the tire. These alternative approaches have experienced certain disadvantages in the prior art due to a lack of optimum prediction techniques, which in turn reduces the accuracy and/or reliability of the tread wear predictions.
As a result, there is a need in the art for a system and method that accurately and reliably estimates tire wear.
According to an aspect of an exemplary embodiment of the invention, a tire wear estimation system is provided. The system includes at least one tire that supports a vehicle. At least one sensor is affixed to the tire to generate a first predictor. A lookup table or a database stores data for a second predictor. One of the predictors includes at least one vehicle effect. A model receives the predictors and generates an estimated wear rate for the at least one tire.
According to another aspect of an exemplary embodiment of the invention, a method for estimating the wear of a tire supporting a vehicle is provided. The method includes providing at least one sensor that is affixed to the tire. A first predictor is generated from the at least one sensor. At least one of a lookup table and a database is provided to store data. A second predictor is generated from the lookup table or the database. One of the predictors includes at least one vehicle effect. The predictors are input into a model, and an estimated wear rate for the tire is generated with the model. The estimated wear rate is communicated to a vehicle operating system.
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.
“ANN” or “Artificial Neural Network” is an adaptive tool for non-linear statistical data modeling that changes its structure based on external or internal information that flows through a network during a learning phase. ANN neural networks are non-linear statistical data modeling tools used to model complex relationships between inputs and outputs or to find patterns in data.
“Aspect ratio” of the tire means the ratio of its section height (SH) to its section width (SW) multiplied by 100 percent for expression as a percentage.
“Asymmetric tread” means a tread that has a tread pattern not symmetrical about the center plane or equatorial plane EP of the tire.
“Axial” and “axially” means lines or directions that are parallel to the axis of rotation of the tire.
“CAN bus” is an abbreviation for controller area network.
“Chafer” is a narrow strip of material placed around the outside of a tire bead to protect the cord plies from wearing and cutting against the rim and distribute the flexing above the rim.
“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.
“Kalman Filter” is a set of mathematical equations that implement a predictor-corrector type estimator that is optimal in the sense that it minimizes the estimated error covariance when some presumed conditions are met.
“Lateral” means an axial direction.
“Lateral edges” means a line tangent to the axially outermost tread contact patch or footprint as measured under normal load and tire inflation, the lines being parallel to the equatorial centerplane.
“Luenberger Observer” is a state observer or estimation model. A “state observer” is a system that provide an estimate of the internal state of a given real system, from measurements of the input and output of the real system. It is typically computer-implemented, and provides the basis of many practical applications.
“MSE” is an abbreviation for mean square error, the error between and a measured signal and an estimated signal which the Kalman filter minimizes.
“Net contact area” means the total area of ground contacting tread elements between the lateral edges around the entire circumference of the tread divided by the gross area of the entire tread between the lateral edges.
“Non-directional tread” means a tread that has no preferred direction of forward travel and is not required to be positioned on a vehicle in a specific wheel position or positions to ensure that the tread pattern is aligned with the preferred direction of travel. Conversely, a directional tread pattern has a preferred direction of travel requiring specific wheel positioning.
“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.
“Piezoelectric Film Sensor” a device in the form of a film body that uses the piezoelectric effect actuated by a bending of the film body to measure pressure, acceleration, strain or force by converting them to an electrical charge.
“PSD” is power spectral density (a technical name synonymous with FFT (fast fourier transform).
“Radial” and “radially” means directions radially toward or away from the axis of rotation of the tire.
“Rib” means a circumferentially extending strip of rubber on the tread which is defined by at least one circumferential groove and either a second such groove or a lateral edge, the strip being laterally undivided by full-depth grooves.
“Sipe” means small slots molded into the tread elements of the tire that subdivide the tread surface and improve traction, sipes are generally narrow in width and close in the tires footprint as opposed to grooves that remain open in the tire's footprint.
“Tread element” or “traction element” means a rib or a block element defined by a shape having adjacent grooves.
“Tread Arc Width” means the arc length of the tread as measured between the lateral edges of the tread.
A first exemplary embodiment of the tire wear estimation system of the present invention is indicated at 50 in
The tires 12 are of conventional construction, and are mounted on a wheel 14. Each tire includes a pair of sidewalls 18 that extend to a circumferential tread 16, which wears from road abrasion with age. Each tire 12 preferably is equipped with a sensor or transducer 24 that is mounted to the tire for the purpose of detecting certain real-time tire parameters, such as tire pressure and temperature. The sensor 24 preferably also includes a tire identification (tire ID) for each specific tire 12, and transmits measured parameters and tire ID data to a remote processor, such as a processor integrated into the vehicle CAN bus, for analysis. The sensor 24 may be a tire pressure monitoring (TPMS) module or sensor, and is of a type commercially available. The sensor 24 preferably is affixed to an inner liner 22 of the tire 12 by suitable means such as adhesive. The sensor 24 may be of any known configuration, such as piezoelectric sensors that detect a pressure within a tire cavity 20.
The tire wear estimation system 50 and accompanying method attempts to overcome the challenges posed by prior art methods that measure the tire wear state through direct sensor measurements. As such, the subject system and method is referred herein as an “indirect” wear sensing system and method that estimates wear rate. The prior art direct approach to measuring tire wear state from tire mounted sensors has multiple challenges, which are described above. The tire wear estimation system 50 and accompanying method utilize an indirect approach, and avoid the problems attendant use of tire wear sensors mounted directly to the tire tread 16. The system 50 instead utilizes a tire wear estimation model that receives multiple input parameters to generate a high-accuracy estimation of the rate of tire wear.
Aspects of the tire wear estimation system 50 preferably are executed on a processor that is accessible through the vehicle CAN bus, which enables input of data from the sensor 24, as well as input of data from a lookup table or a database that is stored in a suitable storage medium and is in electronic communication with the processor. As shown in
A first one of the predictors 52 for the tire wear estimation system 50 includes vehicle effects 54. More particularly, one vehicle effect 54 is a wheel position 56 on the vehicle 10. The vehicle 10 includes four different wheel positions 56: driver side or left side front, passenger side or right side front, driver side or left side rear, and passenger side or right side rear. The tire 12 at each wheel position 56 experiences a different wear pattern, which leads to different tread wear. For example, as shown in
Referring to
Turning to
As shown in
The driver severity 66 takes into account the driving style of the driver of the vehicle 10. More aggressive driving, such as aggressive starts and stops, generates more frictional energy, which increases tire force and increases tread wear. As shown in
Returning to
A fourth one of the predictors 52 for the tire wear estimation system 50, as shown in
With reference again to
Other predictors 52 may optionally be employed in the tire wear estimation system 50. For example, tire pressure as sensed by the sensor 24 may be used as a predictor 52, as low pressure, known as under-inflation, and excessive pressure, known as over-inflation, may impact the wear rate of the tire 12. The roughness of the road driven by the vehicle 10 may impact tire wear, and may thus be employed as a predictor 52 and sensed by the sensor 24 and/or stored in the above-described storage medium. Also, scrubbing of the tires 12, which is a dragging of a tire in a lateral direction due to short turns or parking lot maneuvers, may accelerate tire wear, and may be sensed by the sensor 24 and used as a predictor 52.
Referring now to
Y=β
0+β1X1+β2X2+. . . +βPXP=∈,
We interpret βj as the average effect on Y of a one unit increase in Xi, holding all other predictors fixed.
The model fitting is done using stepwise regression, in turn using a forward selection technique, with p-value criteria. Regression subset selection is performed using a forward stepwise selection technique. In this technique, one starts with a model having no predictors, that is, the model is built with only the intercept. The independent variable with the lowest p-value or the highest F value is chosen, and the remaining variables are added one at a time to the existing model. The variable with the lowest significant p-value is selected. This step is repeated until the lowest p-value is greater than 0.05. To summarize, the procedure is to start with the most basic model, Y=β0 and add one predictor at a time until there is no statistically significant difference between adding one more predictor.
Of course, any suitable modeling technique known to those skilled in the art may be used without affecting the concept or operation of the invention. Once the estimated wear rate 60 is generated, it is communicated from the tire wear estimation system 50 to the vehicle operating systems, such as braking and stability control systems, through the vehicle CAN bus.
Turning to
A second exemplary embodiment of the tire wear estimation system of the present invention is indicated at 100 in
Such real-time measurements include changes in the physical attributes or characteristics of the tire, such as the stiffness of the tread 16. Real-time measurement and modeling of such physical attributes or characteristics may be accomplished through techniques known to those skilled in the art.
As shown in
Turning to
In this manner, the second embodiment of the wear estimation system 100 provides additional refinement and accuracy, as it adds the predictors 102 of real-time measurements of sensed conditions of the tire 12 to the estimation of the wear rate 60 that is generated by the first embodiment of the wear estimation system 50.
The present invention also includes a method of estimating the wear rate of a tire 12. The method includes steps in accordance with the description that is presented above and shown in
It is to be understood that the structure and method of the above-described tire wear estimation system 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.
The invention has been described with reference to preferred embodiments. 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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62475353 | Mar 2017 | US |
Number | Date | Country | |
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Parent | 15909288 | Mar 2018 | US |
Child | 18322866 | US |