Sensing device for tires and method for determining contact lengths

Abstract

An example sensing device includes: a deformable body configured to couple to an inner surface of a tire, the deformable body configured to deform between a neutral deformation outside of a contact zone of the tire and a contact zone deformation over the contact zone of the tire; an inner chamber defined by the deformable body between the deformable body and the inner surface of the tire; and a pressure sensor coupled to the deformable body, the pressure sensor configured to: measure a first change in pressure of the inner chamber when the deformable body deforms from the neutral deformation to the contact zone deformation; and measure a second change in pressure of the inner chamber when the deformable body deforms from the contact zone deformation to the neutral deformation.

Description

SENSING DEVICE FOR TIRES AND METHOD FOR DETERMINING CONTACT LENGTHSCROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority from US Application No. 63 / 666853, filed on July 2, 2024, the contents of which are incorporated herein by reference.FIELD

[0002] The specification relates generally to tire sensing technology, and more particularly to a sensing device for a tire and a method for determining a contact length.BACKGROUND

[0003] Current tire sensors often measure pressure and temperature and are typically placed at the valve stem of the tire. Other measurable quantities which may be useful for monitoring tire performance are the revolutions of the tire per unit time and the length of the patch of tire that is in contact with the road surface (i.e., the contact length of the tire).SUMMARY

[0004] According to an aspect of the present specification an example sensing device includes: a deformable body configured to couple to an inner surface of a tire, the deformable body configured to deform between a neutral deformation outside of a contact zone of the tire and a contact zone deformation over the contact zone of the tire; an inner chamber defined by the deformable body between the deformable body and the inner surface of the tire; and a pressure sensor coupled to the deformable body, the pressuresensor configured to: measure a first change in pressure of the inner chamber when the deformable body deforms from the neutral deformation to the contact zone deformation; and measure a second change in pressure of the inner chamber when the deformable body deforms from the contact zone deformation to the neutral deformation.

[0005] According to another aspect of the present specification, an example method includes: obtaining deformation data of a tire over a series of revolutions, the deformation data including, for each revolution: a first change in pressure of an inner chamber of a sensing device as a deformable body defining the inner chamber deforms from a neutral deformation to a contact zone deformation; and a second change in pressure of the inner chamber as the deformable body deforms from the contact zone deformation to the neutral deformation; determining a width of a contact zone curve based on a measure between the first change in pressure and the second change in pressure; determining a ratio of the width of the contact zone curve to a width of an overall cycle for one revolution; and determining a contact length of a contact zone of the tire based on the ratio.BRIEF DESCRIPTION OF DRAWINGS

[0006] Implementations are described with reference to the following figures, in which:

[0007] FIG. 1 depicts a schematic diagram of an example system for monitoring tires.

[0008] FIG. 2A depicts a schematic cross section of an example sensing device.

[0009] FIG. 2B depicts a block diagram of certain internal components of the sensing device of FIG. 2A.

[0010] FIG. 3 depicts a schematic diagram the deformation of the sensing device in a contact zone and outside the contact zone.

[0011] FIGS. 4A-C depict example graphs of pressure data obtained in the contact zone with different configurations of the sensing device.

[0012] FIG. 5 depicts a flowchart of an example method of determining a contact length.

[0013] FIG. 6 depicts an example graph of pressure data over time.

[0014] FIG. 7 depicts an example graph of time-shifted pressure data over a series of revolutions overlaid with one another.

[0015] FIG. 8 depicts an example graph of extracted maximum and minimum values, and baseline values of pressure data.

[0016] FIGS. 9A-C depict example graphs of contact patch length, temperature and speed over time.DETAILED DESCRIPTION

[0017] Tire data, such as temperature, pressure, and contact length, may be useful measurements to enable companies to monitor tire performance, lifetime, and driving conditions and to provide actionable feedback to ensure road safety and reduce downtime. Such information may be valuable to tire manufacturers and consumers, transportation and logistics companies, delivery services, automotive OEMs, government, GPS / mapping services, performance racing, and off-the-road tire industries like mining, agriculture, and the like.

[0018] FIG. 1 depicts a system 100 for monitoring tires. The system 100 includes at least one sensing device 104, of which two example sensing devices 104-1 and 104-2 (referred to generically as a sensing device 104 and collectively as the sensing devices 104; this nomenclature may also be used elsewhere herein) are depicted.

[0019] The sensing devices 104 are installed on a vehicle 108, and more particularly, in respective tires 112-1 and 112-2 of the vehicle 108. The vehicle 108 may be an automotive vehicle, such as a car, a truck, or the like, or may include other types of vehicles, such as a trailer, a plane, a wheelbarrow, a wagon, or other vehicle including load-bearing tires for monitoring the performance of said tires. The vehicle 108 may include four tires 112, or more tires (e.g., eighteen tires on a semi-trailer truck) or fewer tires (e.g., one tire on a wheelbarrow) in other examples.

[0020] The sensing devices 104 are generally applied to each tire 112, and hence the system 100 may include as many sensing devices 104 as tires 112 on the vehicle. In other examples, the sensing devices 104 may be applied to only some of the tires 112 (e.g., alternating tires or the like). The sensing devices 104 are generally configured to obtain tire data representing measured parameters of the tires 112. In particular, each sensing devices 104 may be installed in a tire cavity 110 of one of the tires 112, at an inner surface 116 of the tire 112, preferably along a radial centerline of the tire 112. Accordingly, the sensing device 104 may obtain tire data representing parameters within the tire cavity 110. For example, the sensing devices 104 may obtain temperature data representing the temperature of the tire cavity 110, pressure data representing an air pressure in the tire cavity 110, deformation data representing deformations of the tires 112, and the like. The sensing devices 104 may therefore include a plurality of sensors and may also be referred to as sensor arrangements and / or sensor assemblies including a plurality of individual sensors configured to obtain data measurements.

[0021] In particular, each sensing device 104 is configured to obtain tire data to allow a computing device to determine operational parameters about the corresponding tire 112,such as the number of revolutions per unit time, the contact length of the tire 112, the load on the tire 112, and the like. In some examples, the sensing device 104 may include a suitable processor or other computing device capable of determining the operational parameters of the tire 112, while in other examples, the sensing device 104 may send the tire data to a remote server 120 or other computing device to determine the operational parameters, which may be part of the system 100 or which may be an independent device interconnected with the system 100.

[0022] Thus, the sensing devices 104 are in communication with the server 120. In some examples, the sensing devices 104 may be in communication with a gateway device 122, a hub, or other device local to the vehicle 108 (e.g., via a Bluetooth Low Energy (BLE)) protocol, a custom low-power radio protocol, or similar. The gateway device 122 may communicate with the server 120 via one or more communication links, including wired and / or wireless communication links, combinations thereof, links, which may traverse one or more networks, including local area networks, wide-area networks, the internet, and the like to send the data to the server 120. In particular, the gateway device 122 may facilitate aggregation of the tire data from each of the tires 112 into vehicle data for the vehicle 108 to optimize data transmissions to the server 120. In other examples, each sensing device 104 may communicate directly with the server 120 via the one or more communication links.

[0023] The server 120 may generally be configured to analyze the vehicle and / or tire data, including data representing the environmental conditions experienced by the tires 112. The server 120 may use the vehicle data to determine the operational parameters as well as overall tire performance, including detecting wear and potential issues with the tires,load balancing, and the like. The server 120 may be any suitable server environment, including a series of cooperating servers, one or more cloud-based servers, and the like, and includes suitable processors and / or processing devices, memories or other suitable computer-readable storage mediums, communications interfaces, and the like to operate as described herein.

[0024] Accordingly, in operation, each of the sensing devices 104 may collect tire data about conditions experienced by its respective tire 112 over a series of rotations. The tire data may include deformation data, temperature data, pressure data, and the like. The server 120 may analyze the vehicle data (i.e., the aggregated tire data for each of the tires 112 of the vehicle 108) captured by the sensing devices 104 to determine tire performance. For example, the server 120 may use the deformation data to determine a contact length for each tire 112. The contact length, together with the pressure data, for example, may allow the server 120 to determine the load on each tire 112. The server 120 may further correlate the load on each of the tires 112 of the vehicle 108 to determine the load distribution between the tires 112 of the vehicle 108. The server 120 may aggregate the tire performance factors to determine a working condition assessment of each individual tire 112, as well as vehicle performance factors to determine a working condition assessment of the vehicle 108.

[0025] Referring to FIG. 2A, a schematic cross-sectional diagram of one of the sensing devices 104 coupled to the inner surface 116 of one of the tires 112 is depicted. The inner surface 116 to which the sensing device 104 is couples is illustrated in FIG. 2A as being flat for simplicity, however it will be understood that the sensing device 104 may be coupled to the inner surface 116 of the tire 112 at the natural curvature of the tire 112.

[0026] The sensing device 104 includes a body 200 defining an inner chamber 204. In the present example, the body 200 includes a substantially planar portion 208 and a wall 212 extending from a perimeter of the planar portion 208. Together, the planar portion 208 and the wall 212 form an approximately concave shape of the body 200 which defines the inner chamber 204. When the sensing device 104 is coupled to the inner surface 116 of the tire 112, the free end of the wall 212 may be coupled and sealed to (e.g., via a suitable adhesive) the inner surface 116, thereby enclosing the inner chamber 204. That is, the inner chamber 204 defines a space between the body 200 and the inner surface 116 of the tire 112 to which the sensing device 104 is coupled. In other examples, the sensing device 104 may further include a liner (not shown) enclosing the inner chamber 204 at the free end of the wall 212 which is further configured to adhere or otherwise couple to the inner surface 116 of the tire 112.

[0027] The planar portion 208 may be, for example, substantially circular, elliptical, rectangular, or another suitable shape or configuration. The planar portion 208 may be configured to be substantially planar to house or support an electronics module 216, including, for example, a printed circuit board (PCB) or other suitable structure configured to support the electronic, sensors, and other sensitive components of the sensing device 104. In particular, the planar portion 208 and / or the electronics module 216 may support a pressure sensor 220 configured to measure the air pressure within the inner chamber 204 to allow determination of a contact length of the tire 112 as described herein.

[0028] Accordingly, the body 200 is made of a deformable material, such as a polyurethane (PU), thermos-plastic polyurethane (TPU), vulcanized rubber, other soft plastic material, or other suitable deformable material. In particular, the body 200 may besufficiently firm so as to hold its shape to define and substantially maintain the inner chamber 204, while being sufficiently deformable and having a low enough stiffness to not impede the deformation of the tire 112 as the portion of the tire 112 having the sensing device 104 coupled thereto passes through the contact patch of the tire 112. In some examples, the sensing device 104 is installed on the tire 112 prior to pressurization of the tire 112, and accordingly, when the tire 112 is pressurized, the tire pressure will cause a compressive force on the sensing device 104. In such examples, the body 200 may be suitably structured and formed of a material allowing the sensing device 104 to withstand the tire pressure without collapsing the inner chamber 204.

[0029] In some examples, the body 200 may include a vent 224, allowing air to flow between the tire cavity 110 and the inner chamber 204, allowing an equilibration of pressures. In the present example, the vent 224 is provided in the wall 212 of the body 200. In other examples, the vent 224 may be omitted to define an enclosed space in the inner chamber 204 which is sealed from the tire cavity 110.

[0030] Thus, the vent 224 allows air to flow between the tire cavity 110 and the inner chamber 204, allowing the pressure to equilibrate and relieving the pressure from within the tire cavity 110 on the sensing device 104 to reduce risk of collapse of the sensing device 104.

[0031] FIG. 2B depicts a block diagram of certain internal components of the sensing device 104 in greater detail. In particular, the sensing device 104 includes a processor 250, a memory 254 and a communications interface 258.

[0032] The processor 250 may include a central processing unit (CPU), a microcontroller, a microprocessor, a processing core, a field-programmable gate array (FPGA), or similar.The processor 250 may include multiple cooperating processors. The processor 250 may cooperate with the memory 254 to realize the functionality described herein.

[0033] The memory 254 may include a combination of volatile (e.g., Random Access Memory or RAM) and non-volatile memory (e.g., read-only memory or ROM, Electrically Erasable Programmable Read Only Memory or EEPROM, flash memory). All or some of the memory 254 may be integrated with the processor 250. The memory stores applications, each including a plurality of computer-readable instructions executable by the processor 250. The execution of the instructions by the processor 250 configures the sensing device 104 to perform the actions discussed herein.

[0034] The sensing device 104 further includes the communications interface 258 interconnected with the processor 250. The communications interface 258 may be configured for wireless (e.g., satellite, radio frequency, Bluetooth, Wi-Fi, or other suitable communications protocols) or wired communications and may include suitable hardware (e.g., transmitters, receivers, network interface controllers, and the like) to allow the sensing device 104 to communicate with other computing devices such as the server 120 or an intermediary gateway or hub device 122. The specific components of the communications interface 258 are selected based on the types of communication links that the sensing device 154 communicates over.

[0035] The sensing device 104 also includes the pressure sensor 220. The pressure sensor 220 is configured to measure the air pressure of the air in the inner chamber 204 and is interconnected with the processor 250. In the example sensing device 104 illustrated in FIG. 2A, the pressure sensor 220 may be a differential pressure sensor configured to measure the pressure difference between the inner chamber 204 and thetire cavity 110. At equilibrium, the pressure difference is constant and may be zero in examples where the vent 224 is included to allow the pressure in the inner chamber 204 and the tire cavity 110 to equilibrate. When the body 200 of the sensing device 104 deforms, the pressure in the inner chamber 204 changes, causing variations in the differential pressure and providing a suitable data signal to enable the determination of the contact length, as described below in greater detail. In other examples, the pressure sensor 220 may be an absolute pressure sensor to measure the absolute air pressure of the air in the inner chamber 204 to similarly acquire a data signal representative of the deformations in the enabling the determination of the contact length.

[0036] In some examples, the sensing device 104 may also include other sensors, such as a temperature sensor 262 and a secondary pressure sensor 266, configured to measure the temperature and the pressure in the tire cavity 110, respectively. Other sensors are also contemplated. The sensing device 104 may also include a battery or energy harvesting unit (not shown). For example, the energy harvesting unit may include a thermo-electric generator, a piezo-electric generator, a micro-electro-mechanical system (MEMS) based energy harvester configured to harvest power from vibrations, or the like.

[0037] Referring to FIG. 3, a contact zone 300 is defined by the contact between a tire 112 and a road (or other surface) 302. This contact induces a deformation of the circular profile of the tire 112 in the contact zone 300. That is, the contact zone 300 of the tire 112 is deformed from the natural or neutral curvature of the tire 112. The contact zone 300 has a contact length L.

[0038] Similarly, the body 200 of the sensing device 104 experiences a neutral deformation 304 when outside the contact zone 300, i.e., when coupled at the neutral curvature of the tire 112. As the sensing device 104 passes through the contact zone 300, the portion of the tire 112 to which the sensing device 104 is coupled deforms and hence the sensing device 104 also experiences a contact zone deformation 308 in the contact zone 300. In particular, the contact zone deformation 308 changes the volume of the inner chamber 204, causing a change in pressure.

[0039] The pressure sensor 220 may be configured to monitor the pressure of the inner chamber 204 to provide a measure of the contact zone 300. Specifically, the pressure of the inner chamber 204 changes when the body 200 moves from the neutral deformation 304 to the contact zone deformation 308 and back. Accordingly, the pressure of the inner chamber 204 acts as a measure or representation of the deformation of the body 200 of the sensing device 104, and hence also represents the deformation of the tire 112. That is, the pressure of the inner chamber 204 as measured by the pressure sensor 220 functions as the deformation data for the tire 112.

[0040] As can be seen in FIG. 3, when the sensing device 104 experiences either the neutral deformation 304 or the contact zone deformation 308, the substantially planar portion 208 remains substantially planar, while the wall 212 enables the deformation of the body 200 and change in volume of the inner chamber 204. The planar portion 208 may therefore act to shield or protect the electronics module 216 and associated components from the deformations experienced by the remainder of the body 200. Thus, in some examples, the planar portion 208 may be formed of a stiffer or less deformable material than the wall 212 or may otherwise be reinforced by one or more ribs or otherstructural features. For example, the planar portion 208 may include a recess in which to receive the electronics module 216 and a removable and securable cover (e.g., secured via friction fit, screws or other suitable fasteners or the like) to allow access to the electronics module 216.

[0041] Depending on the size of the vent 224, air may flow between the tire cavity 110 and the inner chamber 204 at different rates, causing different pressure profiles detected by the pressure sensor 220 as the sensing device 104 moves from the neutral deformation 304 to the contact zone deformation 308 and returning to the neutral deformation 304.

[0042] For example, referring to FIGS. 4A-C schematic plots of the pressure signal as the sensing device 104 progresses through the contact zone 300 over a single revolution with different configurations of the vent 224 are depicted.

[0043] In FIG. 4A, the curve 400a plots the pressure signal, dP, with a relatively large vent 224, allowing the pressure difference between the inner chamber 204 and the tire cavity 110 to equilibrate within the time that the sensing device 104 is in the contact zone 300. In particular, the curve 404a represents the transition of the sensing device 104 through the contact zone 300. In this example, the pressure signal is measured as a pressure differential between the inner chamber 204 and the tire cavity 110. Accordingly, initially dP = 0 as the vent 224 enables equilibration between the inner chamber 204 and the tire cavity 110. As the sensing device 104 enters the contact zone 300, the volume of the inner chamber 204 is compressed and dP increases. As the sensing device 104 passes into the contact zone, the vent 224 equilibrates the pressure and returns dP to 0. That is, the inner chamber 204 has equilibrated with respect to the tire cavity 110. As the sensingdevice 104 emerges from the contact zone 300, the volume of the inner chamber 204 increases and the pressure dP decreases. As the vent 224 equilibrates the pressure between the inner chamber 204 and the tire cavity 110, the pressure dP returns to 0.

[0044] In FIG. 4B, the curve 400b plots the pressure signal, dP, with no vent. That is, the inner chamber 204 is sealed to the tire cavity 110. The curve 404b similarly represents the transition of the sensing device 104 through the contact zone 300. In this example, the pressure in the inner chamber 204 increases as the sensing device 104 enters the contact zone 300. The pressure is maintained as the sensing device 104 moves through the contact zone 300, and then decreases and returns to its original value when the sensing device 104 emerges from the contact zone 300.

[0045] In FIG. 4C, the curve 400c plots the pressure signal dP with a small vent 224 that leaks more slowly than the vent 224 which gives the curve 400a. The curve 404c similarly represents the transition of the sensing device 104 through the contact zone 300. The curve 400c is similar to the curve 400a, in that as the sensing device 104 enters the contact zone 300, the volume of the inner chamber 204 is compressed and dP increases. The pressure decreases as the vent 224 begins equilibrates the inner chamber 204 and the tire cavity 110, however the slower leaking vent 224 may not allow the inner chamber 204 and the tire cavity 110 to fully equilibrate for the differential pressure dP to return to 0 before the sensing device 104 leaves the contact zone 300. When the sensing device 104 leaves the contact zone 300, the volume of the inner chamber 204 still increases and causes a decrease in the pressure dP, which subsequently equilibrates via the vent 224 over a longer tail, relative to the curve 400a.

[0046] Since the curves 400 are based on the pressure detected in the inner chamber 204, the size of the inner chamber 204 may directly affect the amplitude of the signal. In particular, with the same deformation of the tire 112, a larger base area of the inner chamber 204 and a smaller height of the inner chamber 204 will result in a larger change in the volume of the inner chamber 204. Accordingly, the size of the signal may be tuned, for example by adjusting the height of the wall 212. That is, for the same base area of the planar portion 208, a smaller height of the wall 212 will result in a larger signal. Additionally, a larger base area (e.g., as substantially defined by the area of the planar portion 208) may average over the deformation of the tire 112, making the sensing device 104 less sensitive to the tread pattern on a tire 112. Accordingly, the base area of the sensing device 104 and / or the planar portion 208 of the body 200 may have at least one dimension which is greater than the length and / or width of the tread pattern (e.g., the pitch of a tread pattern and / or a width between grooves of a tread pattern) of the tire 112. Preferably, the base area may be at least twice or at least three times the width of an average tread pattern. For example, the sensing device 104 may have a diameter of about 45-65 mm, and preferably about 56 mm, and a height of about 5-10 mm, and preferably about 8 mm. Such dimensions for the sensing device 104 may be sufficient to average over the average pitch of a tread pattern and width between grooves of a tread pattern.

[0047] To enable the curves 400 to be obtained as a reasonable representation of the pressure signal in the inner chamber, the pressure sensor 220 may be configured to have a frequency of data acquisition to provide a reasonable dataset of the spectrum as the sensing device 104 passes through the contact zone 300. For example, data rates of about 3600 Hz or more may be suitable at typical driving speeds and tire diameters. Insome examples, if the tire diameter is known to be larger or smaller than a predefined range, the frequency of data acquisition may be adjusted accordingly. Similarly, in some examples, the gateway device 122 associated with the vehicle 108 may track the speed of the vehicle 108 (e.g., based on global positioning system (GPS) data, accelerometer data, or similar), and may communicate with the sensing device 104 to allow the processor 250 to control the rate of data acquisition of the pressure sensor 220 accordingly. That is, the selected frequency may be dependent on the tire rotation rate, with higher frequency rates for faster tire rotation. To achieve these data rates, a BLE system may be used to transmit the signal to the gateway device 122.

[0048] Turning now to FIG. 5, the functionality implemented by the sensing device 104 will be discussed in greater detail. FIG. 5 illustrates a method 500 of determining a contact length of a tire based on pressure data. The method 500 will be discussed in conjunction with its performance in the system 100. Some or all of the method 500 may be performed by the sensing device 104, by the server 120, by the gateway device 122 associated with the vehicle 108, by a client computing device in communication with the system 100, combinations of the above, and / or other suitable devices and / or systems.

[0049] At block 505, the sensing device 104 may store the predefined quantities of the tire 112 on which the sensing device 104 is installed, such as the radius of the tire 112. For example, the sensing device 104 may obtain the predefined quantities from the server 120, for example after installation and configuration by an operator or fleet manager of the vehicle 108, from the gateway device 122, for example after input by a user or operator of the vehicle 108, or the like. The predefined quantities may be stored in the memory 254. In other examples, other relevant predefined quantities may also be stored.

[0050] At block 510, the sensing device 104 obtains pressure measurements from the pressure sensor 220 representing the deformation data for the tire 112 over a series of revolutions over time. For example, the sensing device 104 may measure and record the deformation data over the length of a trip taken by the vehicle 108, from the time the vehicle 108 starts moving, until it ceases moving. In some examples, the sensing device 104 may send the pressure measurements to the server 120 in real-time, either directly, or via the gateway device 122 associated with the vehicle 108.

[0051] For example, referring to FIG. 6, an example plot 600 of the differential pressure signal dP as a function of time over a series of four revolutions is depicted. In this example, the sensing device 104 includes a vent, and hence the spectrum or curve 400a as illustrated in FIG. 4A is observed in the pressure signal. In particular, the curve 400a is observed in the pressure signal plot 600 each time the sensing device 104 passes through the contact zone 300, and hence the series of curves 400a correspond to revolutions of the tire 112.

[0052] Returning to FIG. 5, at block 515, the sensing device 104 and / or the server 120 is configured to determine the speed at which the tire is moving. In particular, each consecutive peak of the curve 400a represents a revolution of the tire 112, and accordingly, the frequency of the peaks multiplied by the radius of the tire 112 is proportional to the speed at which the tire 112 is moving. In other examples, if a different configuration of sensing device 104 is used, such as a sensing device 104 with no vent 224, the curve 400 may include another inflection point, maximum or minimum, or the like representing entry or exit of the sensing device 104 into or from the contact zone 300, the frequency of which may be multiplied by the radius to determine the speed at which thetire 112 is moving. That is, the server 120 may be configured to determine the width of an overall cycle for one revolution (i.e., between consecutive equivalent significant points) to determine the speed of the tire 112.

[0053] At block 520, the sensing device 104 and / or the server 120 is configured to determine a width of the spectrum or curve 400 representing the movement of the sensing device 104 through the contact zone 300 (i.e., the contact zone curve). For example, in example sensing devices 104 with a vent 224, the server 120 may determine a width (e.g., as represented by a time period) between the maximum and minimum values of a single iteration of the curve 400a or 400c. For example, the distance between the maximum and minimum values may be represented as td and corresponds to the sensing device 104 entering and leaving the contact zone 300. That is, the measure (i.e., time and / or distance) between the first change in pressure as the deformable body 200 deforms from the neutral deformation 304 to the contact zone deformation 308 and the second change in pressure as the deformable body 200 deforms between the contact zone deformation 308 to the neutral deformation 304 represents the width of the contact zone curve. Thus, the server 120 may isolate a single contact zone curve from the deformation data and determine the maximum and minimum values in the contact zone curve to measure the width of the contact zone curve. In some examples, the width may be determined as an average over each of the curves 400 over the data series obtained at block 510.

[0054] In other examples, when the sensing device 104 does not include a vent 224, the server 120 may identify the inflection points of the curve 400b as the endpoints for thesensing device 104 entering and exiting the contact zone 300 for use in determining the width td of the curve 400b.

[0055] At block 525, the sensing device 104 and / or the server 120 is configured to determine a ratio of the contact zone curve to the overall cycle (i.e., time or cycle for a full single revolution of the tire 112). Thus, for example, the time between successive peaks may be represented as tr corresponding to one rotation of the tire 112, and the time td represents the width of the contact zone curve 400, then the ratio td / tr represents the fraction of the circumference of the tire 112 that is in contact with the road. In other examples, width of the contact zone curve 400 may be expressed as an angular measurement, i.e., the contact angle of the tire 112, while the distance between successive peaks (or other suitable distinguishable points) represents a full rotation. The ratio between the contact zone curve and the overall cycle similarly represents the angular portion of a full rotation which corresponds to the contact length.

[0056] At block 530, the sensing device 104 and / or the server 120 is configured to determine the contact length L based on the ratio determined at block 525. In particular, the contact length may be given by equation 1 :

[0057] Where R is the radius of the tire 112.

[0058] FIG. 7 depicts a graph of the differential pressure data of an example sensing device 104 over about 8 hours, in which the individual contact zone curves are timeshifted and overlaid. As can be seen, over time there may be a small change in the amplitude of the signal which is related to the change in the temperature of the tire 112.The distance between the average maximum value and the average minimum value corresponds, in the present example, to a contact angle of about 17 degrees (i.e., 2 • 0.75(TT / 16) radians). The contact angle and the radius of the tire 112 may also allow the contact length to be determined. That is, the ratio of (td / tr) multiplied by 2TT provides a measure of the contact angle. In some examples, the contact angle may be extracted prior to multiplying by the radius R of the tire 112 for analysis of the contact angle separate from or in addition to the analysis of the contact length in determining the operational and working conditions of the tire 112 and / or the vehicle 108.

[0059] Referring to FIG. 8, in some examples, the raw output of the pressure sensor 220 may be used to extract maximum values, minimum values and an average baseline of the contact zone curves. From the maxima and minima of FIG. 8, the server 120 may extract the contact length over time, as depicted in FIG. 9A. The contact patch may be correlated to the temperature measurements (FIG. 9B) and the speed of the vehicle (FIG. 9C).

[0060] The server 120 may analyze the contact length for example for a single trip by correlating the contact length and the pressure data to determine the load on each tire 112, to determine the load distribution between the tires 112 of the vehicle 108, and the like. In some examples, the server 120 may analyze the contact length of the tires 112 of a vehicle 108 over time, for example, over numbers of trips to assess the long-term performance of the tires and overall working condition assessment of the tires. In some examples, if the working condition assessments meet a threshold condition, such as the load distribution for a given trip being sufficiently mis-balanced, then the server 120 may send an alert or notification to a client device of an operator of the vehicle 108. If the long-term working condition assessments of one or more of the tires 112 meets a threshold condition, such as the contact length for a certain percentage of the trips or under a certain load exceeding a threshold contact length, then the server 120 may issue a warning a notification to the client device of the vehicle operator, or to a client device of a fleet manager or the like to monitor the performance of the tires.

[0061] As described herein, a sensing device for tires includes a sensor array which can measure various properties of the tire, such as the pressure of the tire cavity, the temperature where the tire contacts the road, road noise, tread depth, and the like. The sensing device further defines an inner chamber whose volume changes with deformation of the tire at the location of the sensing device. Accordingly, the pressure of the inner chamber can be measured to provide a measure of the deformation of the tire, thereby allowing the contact length and the revolutions per unit time of the tire to be determined. Data may be collected and wirelessly transmitted to a remote server for analysis to extract actionable information on tire performance, lifetime, and driving conditions. For example, the contact length may be combined with load data, tire cavity pressure, rubber temperature, and the like, to determine load distributions, over- or under-inflation of tires leading to contact lengths outside a target range, leading to reduced or increased traction of the tires on the road surface, and the like.

[0062] The scope of the claims should not be limited by the embodiments set forth in the above examples but should be given the broadest interpretation consistent with the description as a whole.

Claims

CLAIMS1 . A sensing device comprising: a deformable body configured to couple to an inner surface of a tire, the deformable body configured to deform between a neutral deformation outside of a contact zone of the tire and a contact zone deformation over the contact zone of the tire; an inner chamber defined by the deformable body between the deformable body and the inner surface of the tire; and a pressure sensor coupled to the deformable body, the pressure sensor configured to: measure a first change in pressure of the inner chamber when the deformable body deforms from the neutral deformation to the contact zone deformation; and measure a second change in pressure of the inner chamber when the deformable body deforms from the contact zone deformation to the neutral deformation.

2. The sensing device of claim 1 , further comprising a vent in the deformable body, the vent configured to allow the inner chamber to equilibrate with an interior volume of the tire.

3. The sensing device of claim 1 , wherein the deformable body comprises a substantially planar surface; anda wall extending substantially perpendicular from a perimeter of the planar surface to define the inner chamber.

4. The sensing device of claim 1 , wherein the deformable body is coupled to the inner surface of the tire at a perimeter of the deformable body.

5. The sensing device of claim 1 , wherein the pressure sensor is a differential pressure sensor.

6. The sensing device of claim 1 , further comprising a processor configured to determine a contact length of the contact zone based on deformation data including the first change in pressure and the second change in pressure of the inner chamber.

7. The sensing device of claim 1 , further comprising a communications interface configured to communicate with a remote server to send deformation data including the first change in pressure and the second change in pressure for determining a contact length of the contact zone based on the deformation data.

8. The sensing device of claim 1 , wherein a base surface area of the deformable body is greater than a pitch of a tread pattern of the tire.

9. The sensing device of claim 1 , further comprising:a temperature sensor configured to measure the temperature of a tire cavity of the tire; and a secondary pressure sensor configured to measure an air pressure of the tire cavity.

10. A method comprising: obtaining deformation data of a tire over a series of revolutions, the deformation data including, for each revolution: a first change in pressure of an inner chamber of a sensing device as a deformable body defining the inner chamber deforms from a neutral deformation to a contact zone deformation; and a second change in pressure of the inner chamber as the deformable body deforms from the contact zone deformation to the neutral deformation; determining a width of a contact zone curve based on a measure between the first change in pressure and the second change in pressure; determining a ratio of the width of the contact zone curve to a width of an overall cycle for one revolution; and determining a contact length of a contact zone of the tire based on the ratio.11 . The method of claim 10, further comprising venting the inner chamber to equilibrate the inner chamber with a tire cavity of the tire.

12. The method of claim 11 , wherein determining the width of the contact zone comprises: isolating the contact zone curve representing a single revolution of the tire; detecting a maximum in the contact zone curve, the maximum corresponding to the first change in pressure; detecting a minimum in the deformation data, the minimum corresponding to the second change in pressure; and determining the measure between the maximum and the minimum as the width of the contact zone curve.

13. The method of claim 10, further comprising determining a speed of the tire based on the width of the overall cycle for one revolution.

14. The method of claim 10, further comprising sending, by the sensing device, the deformation data to a remote server.

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