EP1815212A1

EP1815212A1 - Determining travel surface characteristics by analyzing sensor waveforms

Info

Publication number: EP1815212A1
Application number: EP04822624A
Authority: EP
Inventors: Patrick Allan Tyndall
Original assignee: Michelin Recherche et Technique SA Switzerland; Michelin Recherche et Technique SA France; Societe de Technologie Michelin SAS
Current assignee: Michelin Recherche et Technique SA Switzerland; Michelin Recherche et Technique SA France; Societe de Technologie Michelin SAS
Priority date: 2004-11-15
Filing date: 2004-11-15
Publication date: 2007-08-08
Also published as: WO2006054976A1; CN101057122A

Abstract

Disclosed is a methodology for deriving data related to various selected tire and travel surface conditions. One or more sensors are mounted in association with one or more tires to be monitored. Signal waveforms generated through operation of the one or more sensors are analyzed in a manner similar to that of analyzing an electro-cardiogram taken from a human patient in order to determine selected characteristics of the travel or road surface over which the monitored tires are traversing. Analysis of the signal waveforms may involve analysis of a single waveform and/or comparison of paired waveforms originating for sensors associated with a single tire or paired tires.

Description

UNITED STATES PATENT APPLICATION

TITLE: DETERMINING TRAVEL SURFACE CHARACTERISTICS BY ANALYZING SENSOR WAVEFORMS

FIELD OF THE INVENTION

[0001] The present subject matter concerns travel or road surface condition-monitoring systems for use with vehicle tires. More particularly, the present subject matter concerns enhancements to such systems; especially methodology for identifying selected travel or road surface related conditions based, in part, on the nature of waveforms generated by associated tire sensors.

BACKGROUND OF THE INVENTION

[0002] The incorporation of electronic devices with pneumatic tire and wheel structures yields many practical advantages. Tire electronics may include sensors and other components for relaying tire identification parameters and also for obtaining information regarding various physical parameters of a tire, such as temperature, pressure, tread wear, number of tire revolutions, vehicle speed, etc. Such performance information may become useful in tire monitoring and warning systems, and may even potentially be employed with feedback systems to regulate proper tire parameters or vehicle systems operation and/or performance.

[0003] Yet another potential capability offered by electronics systems integrated with tire structures corresponds to asset tracking and performance characteristics for commercial as well as other type vehicular applications. Commercial truck fleets, aviation craft and earth mover/mining vehicles are all viable industries that could utilize the benefits of tire electronic systems and related information transmission. Radio frequency identification (RFED) tags can be utilized to provide unique identification for a given tire, enabling tracking abilities for a tire. Tire sensors can determine the distance each tire in a vehicle has traveled and thus aid in maintenance planning for such commercial systems.

[0004] One particular area of concern with regard to tire condition monitoring devices and systems and their associated sensors relates to methodologies for deriving the maximum possible data from tire sensors regarding tire and/or vehicle operation. Often these efforts have involved the use of a plurality of different types of variously combined and located sensors to obtain required information.

[0005] Example of such include tire pressure-monitoring applications wherein it may also be important or critical to track other tire or vehicle related parameters such as tire temperature, rotational speed, distance traveled, distances travel at particular speeds, and other parameters. In addition to these types of data that may be used for more or less historical record keeping, data may be collected and reported on a real time basis. With respect to tire pressure monitoring systems, real time reporting to a vehicle operator of a low- pressure condition may become of critical importance if the low-pressure condition becomes suddenly extreme upon occurrence of, for example, a "blow-out" which may affect directional control or stability of the vehicle especially if the vehicle is being operated at highway speeds.

[0006] In addition tire sensors may be actively employed in the real time control of certain functions of the vehicle. Examples of these functions may include anti-lock or anti¬ skid braking systems. In applying such tire sensor signals to real time control of vehicle function as well as other signaling aspects relating to vehicle operation, identification of varying travel or road surface conditions may become advantageous.

[0007] While various implementations of vehicle tire condition monitoring systems have been developed, and while various combinations of sensors have been provided using conventional technologies, no design has emerged that generally encompasses all of the desired characteristics as hereafter presented in accordance with the subject technology.

SUMMARY OF THE INVENTION

[0008] In view of the recognized features encountered in the prior art and addressed by the present subject matter, an improved methodology for deriving data related to various travel or road surface characteristics has been developed. It should be noted that although the principal portion of the remainder of the present disclosure may refer to the use of piezoelectric based sensors integrated with or mounted in or on a tire, such use is not intended to represent a specific limitation of the present technology as, in fact, other types of sensors may be employed in combination with signal processing methodologies as will be more fully described later. Moreover, it should be readily apparent to those of ordinary skill in the art that a data transmission and processing mechanism must be associated with the signals obtained from the various sensors such that data may be passed to and/or from the monitored tires for either concurrent or subsequent processing.

[0009] In an exemplary embodiment, a waveform generated by a tire sensor is examined and analyzed to determine a number of selected travel or road surface characteristics. In a manner somewhat analogous to an electro-cardiogram (EKG) performed on a human patient, the present technology proposes a similar analysis of the waveform produced by tire-associated sensors.

[0010] In further exemplary embodiments of the present technology, one or more tire- associated sensors may be mounted in or on one or more tires thereby providing one or more signals that may be analyzed to determine a plurality of travel or road surface related characteristics. Non-exhaustive examples of such include but are not limited to, sensors mounted on various inside surfaces of one or more tires associated with a vehicle including at the summit, i.e., on the inside liner in an area opposite the treads, on the inside of the sidewall of the tire, on the outside surface of the sidewall, and/or integrated into the structure of the tire itself.

[0011] With more specific reference to an exemplary embodiment of the present subject matter, a piezoelectric sensor, also referred to herein as a piezoelectric patch, may be secured in or on a vehicle tire. It has been demonstrated that piezoelectric tire sensors are extremely sensitive devices and will respond to virtually any force applied anywhere on a tire with which such a sensor may be associated. Selective analysis of the signals obtained from such sensors should, therefore, be able to provide a wealth of information.

[0012] Additional positive aspects of the use of piezoelectric sensors include the possibility of providing a dual function sensor in that the sensor may also be employed as a power source for operating various components that may be associated with the sensor. Such components may include, but are not limited to, elements such as a microprocessor, memory elements, data transmission and reception circuitry, and other elements or components as may be desired for any particular situation or installation.

[0013] Additional aspects of the present subject matter are set forth in, or will be apparent to, those of ordinary skill in the art from the detailed description herein. Also, it should be further appreciated that modifications and variations to the specifically illustrated, referred and discussed features and elements hereof may be practiced in various embodiments and uses of the present subject matter without departing from the spirit and scope of the subject matter. Variations may include, but are not limited to, substitution of equivalent means, features, or steps for those illustrated, referenced, or discussed, and the functional, operational, or positional reversal of various parts, features, steps, or the like.

[0014] Still further, it is to be understood that different embodiments, as well as different presently preferred embodiments, of the present subject matter may include various combinations or configurations of presently disclosed features, steps, or elements, or their equivalents (including combinations of features, parts, or steps or configurations thereof not expressly shown in the figures or stated in the detailed description of such figures). Additional embodiments of the present subject matter, not necessarily expressed in the summarized section, may include and incorporate various combinations of aspects of features, components, or steps referenced in the summarized objects above, and/or other features, components, or steps as otherwise discussed in this application. Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the remainder of the specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] A Ml and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

[0016] Figure 1 diagrammatically shows a tire profile that has been exaggerated in part to illustrate portions of a tire during rolling contact with a surface;

[0017] Figure 2 diagrammatically illustrates a representative signal produced by a tire sensor mounted in association with the tire of Figure 1 as it rolls in and out of contact with a surface; and

[0018] Figure 3 diagrammatically illustrates the combination of a tire and alternative locations for tire sensors.

[0019] Repeat use of reference characters throughout the present specification and appended drawings is intended to represent same or analogous features or elements of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] As discussed in the Summary of the Invention section, the present subject matter is particularly concerned with methodologies for deriving travel or road surface characteristic related data from sensors associated with tires. More particularly, the present subject matter recognizes that significant travel or road surface characteristic related data can be derived from an analysis of the waveforms generated by various tire sensors during the operation of vehicles to which such tires may be mounted as the tires flex under pressures applied to the tires during operation or movement as such tire encounters various travel or road surface conditions.

[0021] As will be more fully explained later, such flexing of the tires during operation produces, via associated sensors, a "signature" waveform that, when analyzed, may be used to reveal significant data regarding current tire and travel or road surface conditions. By analogy, it is well known that a doctor can analyze a patient's electro-cardiogram and discern many different conditions of the human heart as revealed in the heartbeat. Similarly, the signature of strain on the inside of a tire may be made use of as a rich source of information about the state of the tire as well as the surface over which the tire has come into contact.

[0022] It should be noted that each of the exemplary embodiments presented and discussed herein should not insinuate limitations of the present subject matter. Features or steps illustrated or described as part of one embodiment may be used in combination with aspects of another embodiment to yield yet further embodiments. Additionally, certain features may be interchanged with similar devices or features not expressly mentioned which perform the same or similar functions.

[0023] Reference will now be made in detail to the presently preferred embodiments of the subject tire flex signature analysis methodologies. Referring now to the drawings, Figure 1 diagrammatically illustrates a tire 10 mounted for rotation about an axis 20, in contact with a surface 30 such that the tire and surface contact produces a contact patch delineated by bracket 40.

[0024] As may be seen represented in Figure 1, the tire flex signature analysis of the present technology takes advantage of the fact that there are fundamentally four zones of different curvature within an inflated, loaded tire. A major portion of the tire is represented by area 2 and corresponds to that portion of the tire 10 that is neither currently in contact with the surface 30 nor being significantly flexed by way of being in close proximity to area 6. Area 6 corresponds to that portion of the tire that is in full contact with surface 30. Tire portions 4 and 8 correspond to transitional areas that, at vehicle stand still or during uniform motion, are substantially identical, but which become different in shape and extent under driving or braking conditions. In the context of the present discussion, transition zone 8, assuming the direction of tire rotation is that shown by arrow 26 may be considered an "entry" zone while transition zone 4 may be considered an "exit" zone and zone 6 may be considered a "contact" zone.

[0025] Referring now to Fig. 2, diagrammatically illustrated therein is a representation of a waveform or tire flex signature produced by an exemplary tire-associated sensor in accordance with the present technology. As a non-limiting example, the tire-associated sensor may be a piezoelectric sensor that may be self-powered or separately powered or may combine elements of both power-supplying forms to operate the sensor. Moreover, the waveform generating sensor may correspond to other available or yet to be developed sensors. As should be clear, the concepts associated with the present technology do not reside in the particular type of sensor employed but rather in the recognition that tire flex signature waveform analysis may be applied to a waveform generated by any suitable sensor and that significant tire and travel or road surface condition related data may be determined there from without reliance thereon, necessarily, of any one particular sensor type.

[0026] A principle concept of the present technology is to examine waveforms representing strain applied to a tire not only from the surface itself but also based on anomalies associated with the surface. By actually measuring the curvature in each of the four zones previously mentioned, as well as the size or extent of the zones based on the time signature, it is possible to determine many facts about the condition and use of a tire. Moreover, however, by analyzing waveforms generated during the actual contact period of the tire as represent by zone 6 and contact patch 40, various travel or road surface conditions may be identified.

[0027] As previously mentioned, it has been demonstrated that piezoelectric tire sensors are extremely sensitive devices and will respond to virtually any force applied anywhere on a tire with which such a sensor may be associated. Thus, while the use of such piezoelectric sensors is advantageous to the present technology, such use is not a limitation of the present subject matter.

[0028] Appropriate analysis of signals obtained from such sensors will yield many parameters of practical interest such as speed; loading; tire pressure; a condition of under pressure or overload (perhaps independently, since changes in stiffness are not identical to changes in deflection); tread wear (the thickness of the beam changes with wear, thus changing the location of the neutral plane and the stiffness of the beam); driving/braking torque (the footprint of entry and exit curvatures change); belt separation (the sensor is so sensitive it is responsive to nonuniformity anywhere in the tire, not just underneath the sensor); skidding (high-frequency components appear); longitudinal force; lateral force (particularly if a second sensor is installed laterally); hydroplaning; self-aligning torque; and camber.

[0029] Appropriate analysis of such signals will also yield many parameters of practical interest relating to travel or road surface conditions. Non-limiting examples of such conditions may include the presence of loose gravel or other debris on the surface and a determination of whether the tire is running in relatively deep water vs. a dry surface. The detection and classification of other travel or road surface characteristics may also be possible including, for example, ice and/or snow, potholes, protrusions and/or other hazards.

[0030] With further reference to Fig. 2, an exemplary waveform illustrates a signal produced by a sensor associated with a tire under a condition of uniform motion. As illustrated, as tire 10 rotates about axis 20 in the direction of arrow 26, a perturbation is produced in the waveform as the tire enters and leaves each of the previously identified four zones. For example, wave segment 22, and its repeating companion segment 24 corresponds to a signal produced by the portion of the tire that is currently out of contact with surface 30. Positive going pulse 84 represents the beginning of the entry zone 8, i.e. the transition between non-contacting tire segment 2 and the beginning of the fully contacting segment 6. Negative going pulse 82 represents the end of the entry zone 8 and the beginning of the contact zone 6. Waveform segment 62 corresponds to contact zone 6. Positive pulse 44 corresponds to the end of the contact zone 6 and the beginning of the exit zone 4. Negative going pulse 42 corresponds to the end of exit zone 4 and the beginning of the non-contact zone 2.

[0031] As is apparent from the Figure 2 waveform, in a steady state condition, the pulses representing the beginning and end of the respective entry zone 8 and exit zone 4 are substantially identical. Moreover, the spacing between the beginning and ending pulses of these zones are substantially identical. Analysis of the amplitude and time difference between the various pulses can result in determining such information as tire rotational speed, tire loading, pressure, over and under pressure conditions and other parameters as outlined previously. Under conditions of acceleration or deceleration, the previously substantially identical waveforms produced as the tire transitions through zones 4 and 8 will change as a result of a "damming up" or bulging effect due to the combined effects of any acceleration or deceleration and tire traction with the surface.

[0032] Referring now more specifically to the waveform segment 62 corresponding to contact zone 6. As illustrated in Figure 2, waveform segment 62 represents signals generated as a result of various travel or road surface anomalies like those previously mentioned. Various signal analysis methodologies including analog and/or digital techniques may be used to examine, for example, a high frequency component within the waveform segment 62 that may be indicative of the presence of a rough surface as exhibited by the presence of gravel or other particulate materials on the surface. On the other hand, a tire running in relatively deep water will behave differently at the edges of the contact patch 6. Such condition could be detected by analyzing the shape of the waveform corresponding to that generated at such contact patch edges.

[0033] With reference now to Figure 3, illustrated therein are several alternative locations where sensors may be mounted in, on or within a tire in accordance with the present technology. As illustrated in Figure 3, one or more sensors may be associated with tire 10 by mounting such sensors on the outside of the side wall as at 90, on the crown of the tire as at 92, on the inside of the sidewall as at 94, or physically embedded within the tire structure as illustrated by the dotted line rectangle at 96. Any, some or all of these locations might be used for sensor location in any one tire. Moreover, plural sensors may be arranged such that both linear and lateral forces may be more easily detected to obtain the widest possible range of discernable data. In addition, it is not a limitation of the present technology that all of plural sensors should be of the same type. To the contrary, plural types of sensors may be employed as desired or necessary to obtain individual flex signatures that may be more or less responsive to particular types of conditions.

[0034] It should also be kept in mind that one or more tire sensors may be associated with more than one tire associated with any one vehicle. There may be additional useful information obtained by comparing signals generated from different sensors on different tires or even different sensors on the same tire. For example, if signals from one tire indicated that such tire was traversing an icy patch while another tire on the same vehicle was not experiencing the same icing condition, signals might be generated to instruct vehicle traction control equipment to take such condition into consideration. Similarly differing control signals might be generated if tire signal analysis showed that one tire was experiencing some other condition from other tires on a vehicle, for example, being on a gravel surface or in water, mud or snow. The recognition of differences among travel or road surface conditions experienced by various tires on a single vehicle may prove to be significant to maintaining stable operation of such vehicle.

[0035] While the present subject matter has been described in detail with respect to specific embodiments thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing may readily produce alterations to, variations of, and equivalents to such embodiments. Accordingly, the scope of the present disclosure is by way of example rather than by way of limitation, and the subject disclosure does not preclude inclusion of such modifications, variations and/or additions to the present subject matter as would be readily apparent to one of ordinary skill in the art.

Claims

WHAT IS CLAIMED IS:

1. A method for determining selected travel surface condition related information, comprising the steps of: providing a tire having at least sidewall, summit and tread portions; associating one or more electronic signal producing sensors with the tire; monitoring the electronic signals produced by the one or more sensors; and analyzing selected characteristics of the electronic signals to determine selected travel surface condition related information.

2. The method of claim 1 wherein the step of associating comprises affixing one or more electronic signal producing sensors to one or more of an inside portion of the sidewall of the tire, an outside portion of the sidewall of the tire, and an inside portion of the summit of the tire.

3. The method of claim 1 wherein the step of associating comprises embedding one or more electronic signal producing sensors within the tire.

4. The method of claim 2 wherein the step of associating further comprises the step of embedding one or more electronic signal producing sensors within the tire.

5. The method of claim 1, further comprising the step of: rolling the tire over a surface whereby plural zones are established about the tire corresponding to at least a non-contact zone, an entry zone, a contact zone and an exit zone, wherein the step of monitor comprises monitor electronic signals produced as the tire traverses selected of the zones.

6. The method of claim 5 wherein the step of analyzing comprises analyzing electronic signals produced as the tire traverses the contact zone to determine characteristics of the surface over which the tire is traversing.

7. The method of claim 1, wherein the step of analyzing corresponds to determining information relating to one or more of loose gravel, ice, snow, water, pothole, protrusion, and road hazard.

8. A method for deteπnining selected travel surface related information from signals produced by one or more sensors associated with a tire, comprising the steps of: establishing a plurality of spatially diverse zones corresponding to diverse portions of a tire; monitoring signals associated with selected of the plurality of spatially diverse zones; and analyzing the signals to evaluate at least one characteristic of the travel surface.

9. The method of claim 8, wherein the step of analyzing comprises evaluating the frequency content of the signals.

10. The method of claim 8, wherein the step of analyzing comprises evaluating the extent of selected of the plurality of diverse zones.

11. A method of determining selected travel surface related information, comprising the steps of: providing one or more tires; associating one or more electronic signal producing sensors with the one or more tires; establishing a plurality of spatially diverse zones corresponding to diverse portions of the one or more tires; monitoring signals associated with selected of the plurality of spatially diverse zones; and analyzing the signals to evaluate at least one travel surface characteristic.

12. The method of claim 11 , wherein the step of associating comprises associating paired sensors with a single tire.

13. The method of claim 11 , wherein the step of associating comprises associating paired sensors with paired tires.

14. The method of claim 12, wherein the step of analyzing comprises analyzing differences between signals produced by a selected plurality of the plurality of electronic signal producing sensors.

15. The method of claim 13, wherein the step of analyzing comprises analyzing differences between signals produced by a selected plurality of selected of the plurality of electronic signal producing sensors.

16. The method of claim 12, wherein the step of analyzing corresponds to determining information relating to one or more of loose gravel, ice, snow, water, pothole, protrusion, and road hazard.

17. The method of claim 13, wherein the step of analyzing corresponds to determining information relating to one or more of loose gravel, ice, snow, water, pothole, protrusion, and road hazard.