Power efficient sensor unit and system for monitoring tire performance

Abstract

The present specification provides a sensor unit, computing device, system, and method for monitoring tire performance in a power efficient way. This system uses the sensor unit including a contact patch sensor and a microcontroller, a computing device, and a server to determine the tire wear and tire load of a tire. This method of monitoring tire load and tire wear improves over traditional methods by providing continuous monitoring in a power efficient operation.

Description

Docket No. P13305PC00POWER EFFICIENT SENSOR UNIT AND SYSTEM FOR MONITORING TIRE PERFORMANCECROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 722,624 entitled Power Efficient Measurement of Tire Load and Tire Wear, filed on November 20, 2024, the entire contents of which are incorporated herein by reference.FIELD

[0002] The present specification is directed to vehicle maintenance. More specifically, it pertains to tire monitoring and specifically a sensor unit for monitoring tire performance.BACKGROUND

[0003] Monitoring tire load and tire wear is essential for vehicle safety, fuel efficiency, and longevity. Poorly maintained tires can lead to accidents due to reduced traction, increased braking distances, and blowouts. Poorly maintained tires are replaced more often, which increases maintenance costs and the negative environmental impacts from frequent tire disposal. Additionally, improper tire load negatively impacts fuel efficiency by increasing rolling resistance, leading to higher fuel consumption and CO2emissions. Conventional methods for monitoring tire wear and load often involve costly equipment, battery life constraints, and vehicle downtime. Additionally, these methods are impractical for continuous monitoring applications. It is often difficult to obtain real-time readings while driving. Given these constraints, there is a need for an improved system to monitor tire conditions in real time, enhancing safety, efficiency, cost-effectiveness, and environmental benefits.SUMMARY

[0004] An aspect of the specification is directed to a sensor unit for monitoring tireDocket No. P13305PC00 performance. The sensor unit includes a contact patch sensor for detecting deformation of a tire, determining whether the deformation of a tire is above or below a threshold, and outputting a digital voltage signal when the deformation of a tire is above the threshold. The sensor unit further includes a microcontroller for operating in an inactive mode to reduce power consumption, operating in an active mode in response to a change in the digital voltage signal, recording a time when the digital voltage signal changes, and returning to the inactive mode after recording the time.

[0005] In one example, the contact patch sensor includes an accelerometer for detecting the deformation of a tire by measuring a centripetal acceleration, and for outputting the digital voltage signal when the centripetal acceleration is above the threshold.

[0006] In a further example, the sensor unit includes a wireless transmitter for conveying signal data. The signal data includes the recorded time from the microcontroller.

[0007] In a yet further example, the sensor unit includes a temperature sensor for measuring a temperature of the tire. The signal data includes the temperature of the tire.

[0008] In a further example, the sensor unit includes a pressure sensor for measuring a tire pressure. The signal data includes the tire pressure.

[0009] In another example, the sensor unit includes a battery for supplying power to the sensor unit.

[0010] In a further example, the microcontroller includes a timer for operating continuously in the active mode and the inactive mode. The recorded time is output from the timer.

[0011] In a further example, the contact patch sensor only outputs the digital voltage signal when the deformation of a tire is above or below the threshold for a filtering period.

[0012] Another aspect of the specification is directed to a computing device forDocket No. P13305PC00 monitoring tire performance. The computing device includes a wireless transmitter for receiving signal data which includes a start time and end time of the digital voltage signal from a sensor unit connected to a tire of a vehicle, outputting a digital voltage signal when a centripetal acceleration in the tire is above a threshold. The computing device further includes a processor for receiving the signal data from the wireless transmitter and computing a contact patch time based on the start time and end time of the digital voltage signal.

[0013] In one example, the computing device is positioned in or connected to the vehicle.

[0014] In a further example, the computing device is remote from the vehicle and receiving the signal data via a network.

[0015] In a further example, the computing device includes a global positioning system (GPS) device for measuring a velocity of the vehicle. The signal data includes the velocity of the vehicle.

[0016] In a further example, the processor computes a full tire revolution time based on the start time and end time.

[0017] In a further example, the processor determines an apparent circumference of the tire based on the velocity of the vehicle and the full tire revolution time.

[0018] In a further example, the processor computes the apparent circumference according:, .rvelocity of the vehicle apparent circumf erence = - j - . full tire revolution time

[0019] In a further example, the processor retrieves an initial apparent circumference of the tire stored in the memory at the computing device.

[0020] In a further example, the processor computes a tire wear based on an initial tire radius, the initial apparent circumference and the apparent circumference.Docket No. P13305PC00

[0021] In a further example, the processor computes the tire wear according to:Tire wear =. . . . . .. (initial apparent tire circumference- apparent tire circumference initial tire radius - . initial apparent tire circumference

[0022] In a further example, the processor is computing a contact angle based on the contact patch time and the full tire revolution time.

[0023] In a further example, the processor computes the contact angle according to:, , , „ „ contact patch time contact anqle = 2 / 7 - . full tire revolution time

[0024] In a further example, the processor determines a contact length based on the contact angle and a tire length stored in memory at the computing device.

[0025] In a further example, the processor computes the contact length according to: contact length = tire length X contact angle .

[0026] In a further example, the processor: retrieves a tire model data, a sensor location, and a weather data stored in the memory at the computing device; and computes a tire load based on the tire model data, the sensor location, the contact length, the tire wear, the weather, a temperature, and a tire pressure.

[0027] In a further example, the processor determines the tire load according to a function:Tire load= F(tire model data, sensor location, contact length, tire wear, weather, temperature)x tire pressure.

[0028] Another aspect of the specification is directed to a system for monitoring tire performance. The system includes a sensor unit including a contact patch sensor for measuring deformation of a tire, determining whether the deformation of a tire is above or below a threshold, and outputting a digital voltage signal when the deformation of a tire is above the threshold. The system further includes a microcontroller for operating in an inactive mode to reduce power consumption, operating in an active mode in response toDocket No. P13305PC00 a change in the digital voltage signal, recording a time when the digital voltage signal changes, and returning to the inactive mode after recording the time. The system further includes a wireless transmitter for conveying signal data. The signal data including the start time or end time. The system further includes a computing device including a wireless transmitter for receiving the signal data from the sensor unit and conveying the signal data over a network. The system further includes a server including a processor for receiving signal data via a network and computing a contact patch time based on the start and end time of a digital voltage signal.

[0029] In one example, the contact patch sensor includes an accelerometer for detecting the deformation of a tire by measuring a centripetal acceleration, and outputting the digital voltage signal when the centripetal acceleration is above the threshold.

[0030] Another aspect of the specification is directed to a method for monitoring tire performance using a sensor unit including a contact patch sensor and a microcontroller. The method further including detecting a deformation of a tire with the contact patch sensor, determining whether the deformation of a tire is above or below a threshold, and outputting a digital voltage signal from the contact patch sensor when the deformation of a tire is above the threshold. The method further including a microcontroller operating in an inactive mode to reduce power consumption, operating in an active mode in response to a change in the digital voltage signal and recording a time when the digital voltage signal changes, and the microcontroller returning to the inactive mode after recording the time.

[0031] In one example, the method where detecting the deformation of the tire with the contact patch sensor includes measuring a centripetal acceleration with an accelerometer, and outputting the digital voltage signal from the accelerometer when the centripetal acceleration is above the threshold.

[0032] In a further example, the method including conveying signal data using a wireless transmitter associated with the sensor unit. The signal data including theDocket No. P13305PC00 recorded time from the microcontroller.

[0033] In a further example, the method including measuring a temperature of the tire using a temperature sensor associated with the sensor unit. The signal data further including the temperature of the tire.

[0034] In a further example, the method including measuring a tire pressure using a pressure sensor associated with the sensor unit. The signal data further including the tire pressure.

[0035] In a further example, the method including supplying power to the sensor unit using a battery associated with the sensor unit.

[0036] In a further example, the method including operating a timer associated with the microcontroller continuously in the active mode and the inactive mode. The recorded time is output from the timer.

[0037] In a further example, the method including outputting the digital voltage signal from the contact patch sensor when the deformation of a tire is above or below the threshold for a filtering period.

[0038] In this specification, elements may be described as “configured to” perform one or more functions or “configured for” such functions. In general, an element that is configured to perform or configured for performing a function is enabled to perform the function, or is suitable for performing the function, or is adapted to perform the function, or is operable to perform the function, or is otherwise capable of performing the function.

[0039] It is understood that for the purpose of this specification, language of “at least one of X, Y, and Z” and one or more of X,Y and Z” can be construed as X only, Y only, Z only, or any combination of two or more items X, Y, and Z (e.g, XYZ, XY,YZ, ZZ, and the like). Similar logic can be applied for two or more items in any occurrence of “at least one ...” and “one or more ...” language.

[0040] The terms “about”, “substantially”, “essentially”, “approximately”, and the like,Docket No. P13305PC00 are defined as being “close to”, for example as understood by persons of skill in the art. In some implementations, the terms are understood to be “within 10%,” in other implementations, “within 5%”, in yet further implementations, “within 1 %”, and in yet further implementations “within 0.5%.

[0041] These together with other aspects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Embodiments are described with reference to the following figures.

[0043] Figure 1 is a block diagram depicting an example sensor unit for monitoring tire performance.

[0044] Figure 2 is a schematic diagram depicting the sensor unit of Figure 1 located in a tire.

[0045] Figure 3 is a block diagram depicting a method of monitoring tire performance using the sensor unit of Figure 1 .

[0046] Figure 4A is a schematic diagram depicting exemplary performance of the method of Figure 3.

[0047] Figure 4B is another schematic diagram depicting exemplary performance of the method of Figure 3.

[0048] Figure 4C is another schematic diagram depicting exemplary performance of the method of Figure 3.

[0049] Figure 4D is a schematic diagram depicting exemplary performance of block 324 of Figure 3.

[0050] Figure 5 is a schematic diagram depicting exemplary performance of theDocket No. P13305PC00 method of Figure 3.

[0051] Figure 6 is a schematic diagram depicting exemplary performance of block 316 of Figure 3.

[0052] Figure 7 is a schematic diagram depicting the effect of vehicle speed on accelerometer signal.

[0053] Figure 8 is a schematic diagram depicting the effect of large noise events on measured rotation times.

[0054] Figure 9 is a block diagram depicting a computing device to monitor tire performance.

[0055] Figure 10 is a schematic diagram depicting a method of monitoring tire performance.

[0056] Figure 11 is a block diagram depicting a system to monitor tire performance.DETAILED DESCRIPTIONDEFINITIONS

[0057] The following definitions are used herein:

[0058] “Contact Length” herein refers to a longitudinal measurement of the area where the tire touches the road surface.

[0059] Contact patch herein refers to the portion of the tire in contact with the road surface which deforms and becomes flat.

[0060] Tire Load herein refers to the amount of weight or force exerted on a tire by the vehicle, passengers, cargo, and other external factors.

[0061] Tire Wear herein refers to the loss of tire tread material due to friction between the tire and the road surface over time.SYSTEM AND METHODDocket No. P13305PC00

[0062] Critical to tire performance monitoring are tire load and tire wear. Tire load affects wear patterns, traction, and overall durability of tires. Overloaded or underloaded tires experience uneven stress distribution, leading to premature wear, reduced grip, and an increased risk of blowouts. Excessive tire wear not only compromises safety but also impacts fuel efficiency, as worn tires increase rolling resistance. Conventional methods for measuring these parameters often involve costly equipment or require vehicle downtime, which is impractical for large fleets or continuous monitoring applications. Given these concerns, there is a need for an advanced system to continuously track tire conditions, providing actionable data to improve tire management, efficiency, and performance.

[0063] The present invention will be described with respect to the figures herein.

[0064] Figure 1 depicts a diagram of a sensor unit 100 for monitoring tire performance, according to one example. The sensor unit 100 includes a contact patch sensor connected to a microcontroller 108 and configured to detect the deformation of a tire. In the example shown in Figure 1 the contact patch sensor includes an accelerometer 104, however, the contact patch sensor is not particularly limited to the accelerometer. In other embodiments, the contact patch sensor comprises a strain sensor, bend sensor, deformation sensor, displacement sensor, accelerometer, gyroscope, inertial measurement unit (I MU), or combinations thereof. The contact patch sensor in these forms detects or measures changes in a shape and position of the contact patch of the tire due to an external force. The external force can be compared against a threshold to determine if the force is above or below the threshold. For exemplary purposes, the sensor unit 100 will be described herein with respect to the accelerometer 104. Any description herein of the accelerometer 104 may be similarly applied to another type of the contact patch sensor.

[0065] The microcontroller 108 may be further connected to a wireless transmitter 112 and a memory 116. In addition to the accelerometer 104, the sensor unit 100 may include one or more supplementary sensors connected to the microcontroller. In the exampleDocket No. P13305PC00 shown in Figure 1 , the supplementary sensors include a pressure sensor 120 and a temperature sensor 124, however the supplementary sensor is not particularly limited.

[0066] The sensor unit 100 can include the accelerometer 104 which measures the centripetal acceleration at the tires. The accelerometer 104 may include a MEMS (Micro ElectroMechanical System) accelerometer, a piezoelectric accelerometer, a piezoresistive accelerometer, a capacitive accelerometer, an optical accelerometer, or a combination thereof, for measuring the centripetal acceleration in the tire.- The accelerometer 104 may include a timer and a clock to record times at the accelerometer 104.

[0067] The microcontroller 108 may comprise a central processing unit (CPU), a microprocessor, a processing core, a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), or a similar device capable of executing instructions. The microcontroller 108 is configured to communicate with the accelerometer 104. The microcontroller 108 may be connected to and cooperate with the memory 116 that stores instructions and data. The microcontroller 108 may include a timer for tracking the time. In some examples, the microcontroller 108 may include the battery of the sensor unit 100.

[0068] In examples where the sensor unit 100 includes a memory, the memory 116 may include a non-transitory machine-readable medium, such as an electronic, magnetic, optical, or other physical storage device that encodes the instructions. The medium may include, for example, random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory, a storage drive, an optical device, or similar. The memory may be connected to, or included in, the microcontroller 108.

[0069] In examples where the sensor unit 100 includes a wireless transmitter 112, which is configured to communicate with the microcontroller 108 and convey signal data. The wireless transmitter 112 may use one or more wireless communication protocolsDocket No. P13305PC00 including but not limited to Bluetooth and Bluetooth Low Energy technology, Wi-Fi, Radio, and Cellular systems. In some implementations, the wireless transmitter 112 may include an integrated or external antenna to facilitate signal transmission.

[0070] In the example shown in Figure 1 , the sensor unit 100 includes a pressure sensor 120 which measures the air pressure of the tire and sends the pressure data to the wireless transmitter 112. Pressure sensors can include strain gauge sensors, capacitive pressure sensors, piezoelectric pressure sensors, piezoresistive pressures sensors, optical pressure sensors, other MEMS sensors, or a combination thereof.

[0071] In the example shown in Figure 1 , the sensor unit 100 can also include the temperature sensor 124 which measures the temperature of the tire and sends the temperature data to the wireless transmitter 112. Temperature sensors can include thermocouple sensors, infrared sensors, semiconductor sensors, thermistor sensors, or a combination thereof.

[0072] The sensor unit 100 can further include a power source 128 to provide power supply to the sensor unit. The power source 128 can be a battery, wired power direct from the vehicle, or similar. In other examples, the power source 128 can be any kind of battery, high-voltage power source, any type of electric generator, a renewable energy power source, or any other kind of power source.

[0073] The sensor unit 100 is configured to be mounted to a tire of a vehicle. Figure 2 is a schematic diagram of a tire 202 including the sensor unit 100 of Figure 1 . The sensor unit 100 may be attachable to the interior surface of the inside of the tire or embeddable within the rubber of the tire. As the tire rotates, the sensor unit 100 also rotates in the direction of rotation R. Generally, the sensor unit 100 is positioned at a circumferential surface of the tire and is oriented so that the accelerometer 104 is sensitive to acceleration in the radial direction. In other embodiments, the sensor unit 100 may be placed at another location on the tire or also on the vehicle. In one example, the accelerometer 104 may be placed on a circumferential surface of the tire while the remaining components ofDocket No. P13305PC00 the sensor unit 100 may be located inside the vehicle. In another example, the accelerometer 104 may be located on the inner surface of the tire while the remaining components of the sensor unit 100 may be located inside the vehicle.

[0074] Figure 3 shows a method 300 for monitoring tire performance, according to one example. In the example shown in Figure 3, the method 300 is performed on the sensor unit 100.

[0075] Block 302 comprises operating in an inactive mode. In sensor unit 100 shown in Figure 1 , block 302 is performed by the microcontroller 108. The inactive mode is a low-power state in which the functionality of the microcontroller 108 is reduced. In the inactive mode, the microcontroller 108 may not be sending or receiving information wirelessly. In the inactive mode, the microcontroller 108 may ignore signals it receives. The microcontroller 108 may stop executing instructions and access to the memory 116 may be disabled in the inactive mode. Power to other components of the sensor unit 100 may be cut off in the inactive mode, including the memory 116, pressure sensor 120, and temperature sensor 124. In some examples, other components of the sensor unit 100 may become dormant when the microcontroller 108 is in the inactive mode. The inactive mode saves power consumption and battery life at sensor unit 100. The timer operates continuously while the microcontroller 108 is in the inactive mode, continuously counting up.

[0076] Block 304 comprises measuring the centripetal acceleration in a tire. In the sensor unit 100 shown in Figure 1 , block 304 is performed by the accelerometer 104 which measures the centripetal acceleration. Block 304 may be performed continuously throughout method 300, while other blocks are being performed. As shown in Figure 4A, the sensor unit 100 experiences centripetal acceleration when the tire rotates in the direction of rotation R, and the sensor unit 100 is located outside of the contact patch C. The contact patch C is the portion of the tire 202 which comes in contact with the road surface and deforms, becoming flat. There is a relationship between the length of the contact patch C, tire pressure, and load on the tire. As the load on a tire increases, theDocket No. P13305PC00 length of the contact patch C increases when the tire deforms in response to increased weight. An increase in the tire pressure also affects the contact patch C, because an increase in tire pressure inflates the tire causing the contact patch C to decrease in length. As shown in Figure 4B, the sensor unit 100 does not experience centripetal acceleration, or experiences decreased centripetal acceleration when in the contact patch C. After passing through the contact patch C, the sensor unit 100 experiences centripetal acceleration again, as depicted in Figure 4C. An example of the centripetal acceleration experienced by the sensor unit 100 is depicted by area 402 under the graph in Figure 4D. While the sensor unit 100 comes in contact with the contact patch C, the centripetal acceleration reduces to zero or near zero as the tire 202 deforms where the sensor unit 100 is located. This is depicted by area 404 in the graph shown in Figure 4D. Once the sensor unit 100 exits the contact patch C, the centripetal acceleration increases again, as depicted in area 406 in the graph in Figure 4D.

[0077] Block 308 comprises determining if the centripetal acceleration is above a threshold. In the sensor unit 100 of Figure 1 , block 308 is performed by the accelerometer 104 which compares the centripetal acceleration to a threshold. The threshold may be predetermined and retrieved from the memory 116 during performance of block 308. In some examples, the threshold may be predetermined by the user inputs and programmed into the accelerometer 104. In some examples, the microcontroller 108 can dynamically determine the threshold by analyzing inputs of speed, pressure, or temperature from the sensor unit 100 to determine the threshold. If the accelerometer 104 determines that the centripetal acceleration is above the threshold, the method 300 proceeds to block 316. If the accelerometer 104 determines that the centripetal acceleration is not above the threshold, the method 300 proceeds to block 312.

[0078] Block 312 comprises not outputting a digital voltage signal. Block 312 is performed when the centripetal acceleration is not above the threshold. In the sensor unit 100 of Figure 1 , block 312 is performed by the accelerometer 104. As shown in Figure 3, the accelerometer 104 determines that the centripetal acceleration is not above theDocket No. P13305PC00 threshold, then the accelerometer 104 does not output the digital voltage signal or stops outputting the digital voltage signal. In block 312, the accelerometer 104 continues to measure the centripetal acceleration as represented by block 304. After block 312 of the method 300, the next step is block 317 which is to determine if a change in the digital voltage signal is detected (block 317 is described in greater detail herein.).

[0079] Block 316 comprises outputting the digital voltage signal. In the example shown in Figure 3, block 316 is performed by the accelerometer 104 of sensor unit 100. Block 316 is performed when the centripetal acceleration is above the threshold. As shown in Figure 3, when the accelerometer 104 determines that centripetal acceleration is above the threshold, then the accelerometer 104 outputs the digital voltage signal to the microcontroller 108. The digital voltage signal from accelerometer 104 may be a binary voltage signal indicating whether the centripetal acceleration is above or below the threshold. The accelerometer 104 may process raw acceleration and convert the raw acceleration from an analog value into a digital voltage signal which has the acceleration encoded in a binary signal. Binary signals can be output as a first or second voltage for a low power signal received at the microcontroller 108, where the first voltage is lower than the second voltage. Acceleration above the threshold is output as the second voltage digital signal which is defined as binary input 1 , whereas acceleration below the threshold is output as the first voltage digital signal which is defined as binary input 0. The first voltage digital signal output by the accelerometer 104 can be zero voltage, which is the equivalent of no voltage input. In some examples the first voltage digital signal is output as negative voltage. In some examples, when the digital voltage signal changes from first voltage to second voltage or second voltage to first voltage occurs from accelerometer 104, the microcontroller 108 generates an interrupt request in response to the change in the voltage digital signal. In other examples the binary signal from accelerometer 104 may be output as on or off.

[0080] As part of block 316, the accelerometer 104 may also perform a noise filtering process where the accelerometer 104 is configured to only output the digital voltageDocket No. P13305PC00 signal when the centripetal acceleration is above the threshold for a filtering period. In some examples, the filtering period may be predetermined to a specific duration and retrieved from the memory 116 during performance of block 316. In some examples the filtering period is dynamically determined based on speed, pressure, or temperature data from sensor unit 100. In an embodiment when the filtering period is dynamically determined, the microcontroller 108 may compute speed based on data from accelerometer 104 or the speed may be received from a GPS or external computing device (as will be described herein with respect to figure 9). The microcontroller 108 may determine the filtering period based on the speed. The microcontroller 108 sends a signal to the accelerometer 104 to output the digital voltage signal when the centripetal acceleration is above the threshold for the filtering period. At higher speeds, the microcontroller 108 may request to reduce the filtering period and at lower speeds the microcontroller 108 may request to increase the filtering period. The microcontroller may obtain data from the pressure sensor 120 or the temperature sensor 124 to further adjust the average time it signals to the accelerometer 104.

[0081] Block 317 comprises detecting whether the digital voltage signal has changed. In sensor unit 100, block 317 is performed by the microcontroller 108 which receives the digital voltage signal from the accelerometer 104 and detects whether the digital voltage signal has stopped or started. If no change in the digital voltage signal is detected, the method 300 returns to block 302. If a change in the digital voltage signal is detected, the method 300 continues to block 318.

[0082] Block 318 comprises operating in an active mode. In the sensor unit 100 of Figure 1 , block 318 is performed by the microcontroller 108 which switches from the inactive mode to the active mode. The microcontroller 108 operates in the inactive mode until it detects a change in the digital voltage signal from the accelerometer 104, then the microcontroller 108 generates an interrupt request to start operating in the active mode. The microcontroller 108 is configured to operate in the active mode when the digital voltage signal starts or stops. The active mode may be characterized by higherDocket No. P13305PC00 functionality than the inactive mode, where the microcontroller 108 is not in a low-power state. In the active mode, the microcontroller 108 may consume more power than in the inactive mode. In the active mode, a Central Processing Unit (CPU) of the microcontroller 108 may be turned on. In the active mode, memory access at the CPU may be performed and the microcontroller 108 may process data. In the active mode, the microcontroller 108 may actively execute instructions, send data, and receive data from other components.

[0083] Block 320 comprises recording the time corresponding to the change in the digital voltage signal. In the sensor unit 100 illustrated at Figure 1 , block 320 is performed by the microcontroller 108. As shown in Figure 5 (described in greater detail herein), at the digital voltage signal change, the microcontroller 108 enters the active mode, and the timer connected to the microcontroller 108 records the time that the digital voltage signal stops or starts. The timer is configured to indicate the times when the microcontroller 108 switches to active mode and inactive mode. The times recorded at the timer may be saved in the memory 116. Repeated performance of the method 300 will produce a plurality of recorded times which can be used to calculate the time periods between the digital voltage signal changes.

[0084] Block 324 comprises outputting signal data. In the example shown in Figure 3, block 324 is performed by the microcontroller 108 which outputs the signal data to the wireless transmitter 112 for wireless transmission to a remote computer or server. The microcontroller 108 may output the signal data continuously in response to recording the time at block 320, or the microcontroller 108 may output the signal data periodically. In examples where the microcontroller 108 outputs the signal data periodically, after performing block 320 the microcontroller 108 may output signal data to the wireless transmitter 112 after a preset number of measurements has been recorded in the memory 116, or after a predetermined period. In a specific, non-limiting example, the microcontroller 108 records the time that the digital voltage signal stops or starts for one second in every minute. At block 320 the microcontroller 108 records the time that theDocket No. P13305PC00 digital voltage signal stops or starts for one second in a minute, then the microcontroller 108 does not record the time after the second is complete. Following the completion of a minute, the microcontroller 108 continues to operate at block 320 and records the time that the digital voltage signal stops or starts for one second in another minute. After the microcontroller 108 records the preset number of measurements, method 300 moves to block 324 and the microcontroller 108 outputs signal data to the wireless transmitter 112. The signal data includes the recorded times output from the timer of the microcontroller 108. The signal data may further include one or more of the centripetal acceleration, the digital voltage signal from the accelerometer 104, the temperature data from the temperature sensor 124, and the pressure data from the pressure sensor 120. During the performance of block 324, the microcontroller 108 continues to operate in active mode. After block 324, the method 300 returns to block 302, and the microcontroller 108 operates in inactive mode.

[0085] Figure 5 is a schematic diagram showing exemplary performance of the method 300 of Figure 3. When the centripetal acceleration is above the threshold, the accelerometer 104 outputs the digital voltage signal to the microcontroller 108. As shown in Graph 502, the accelerometer 104 outputs a raw acceleration, detecting when the centripetal acceleration is above and below the threshold. The threshold may be predetermined from user inputs. Graph 504 shows that when the accelerometer 104 detects the centripetal acceleration is above the threshold, the accelerometer 104 will return the digital voltage signal. At the point when the centripetal acceleration drops below the threshold, the accelerometer 104 does not output the digital voltage signal. The measurement process at the accelerometer 104 may be subject to significant noise caused by vibration or other forces in the vehicle. It is at this stage that the noise filtering process may be performed. As shown in Graph 506, the change in the digital voltage signal awakens the microcontroller 108 to operate in the active mode where the microcontroller 108 records the time of the change in the digital voltage signal. The interval between two consecutive recorded times is referred to herein as Tn. In theDocket No. P13305PC00 example shown in Figure 5, intervals where the digital voltage signal is above the threshold are depicted by n, T3, and TS, and intervals where the digital voltage signal is below the threshold are depicted by T2, T4, and T6.

[0086] Figure 6 shows one example of the noise filtering process which may be conducted at block 316 in the method 300 of Figure 3. In Figure 6, the noise filtering process is performed at the accelerometer 104. This noise filtering process may prevent noise in the contact patch C from complicating the digital voltage signal. As shown in Graph 602, the accelerometer 104 measures the centripetal acceleration of the tire and determines when the centripetal acceleration is above or below the threshold. As shown in Graph 604, the accelerometer 104 generates an unfiltered digital voltage when the centripetal acceleration is above the threshold. Graph 606 shows the noise filtering process employed by the accelerometer 104. The accelerometer 104 outputs a digital voltage signal with filter after filtering the unfiltered digital voltage. Only when the accelerometer 104 detects that the centripetal acceleration is above the threshold for the filtering period (Tfiiter), then the accelerometer 104 outputs the digital voltage signal with filter to the microcontroller 108. Thus, the beginning of the digital voltage signal is delayed by Tfiiter. Microcontroller 108 sends Tfiiter once the system starts up and Tfiiter is stored on a register in the accelerometer 104 until the microcontroller 108 returns an updated Tfiiter, then the updated Tfiiter is stored in a register of accelerometer 104. The duration of time when the accelerometer is not outputting the digital voltage signal is referred to herein as Tmeasured. In examples that use the noise filtering process, the microcontroller 108 subtracts the Tfiiter from Tmeasured to determine the contact patch time, herein referred to as Tcontact. Equation 1 shows one example of the calculation conducted at the microcontroller 108 to calculate Tcontact:^contact ^measured ^-filterEquation 1

[0087] The data may also be sensitive to noise when the accelerometer 104 is outsideDocket No. P13305PC00 the contact patch C, particularly at low tire speeds. To reduce the effects of noise outside the contact patch C, one or more of the following steps may be applied: the threshold may be lowered to overcome the noise outside the contact patch C, data collected when the vehicle is moving below a minimum speed may be ignored, the filtering process of Equation 1 may be applied, and the rotation time may be compared to a prior or subsequent rotation time. Figure 7 shows an example of how speed can affect the sensitivity of the accelerometer 104 to noise occurring outside of the contact patch C. As shown in Figure 7, slower acceleration which is sensitive to noise outside the contact patch C can result in drops in the centripetal acceleration which fall below the threshold. Faster acceleration, which is also subject to noise outside the contact patch C, also results in drops in the acceleration but these are less likely to fall below the threshold. In some examples, data collected at low speeds may be ignored since it is more prone to this type of noise. The minimum speed may be stored in the memory 116 or at an external computing device. In other examples, the noise filtering process of Equation 1 may be similarly applied to filter the noise outside the contact patch C. In these embodiments, only when the accelerometer 104 detects that the centripetal acceleration is below the threshold for the filtering period inner, does the accelerometer 104 stop outputting the digital voltage signal to the microcontroller 108. Then the microcontroller 108 subtracts Tfiiter from Tmeasured in order to determine when the contact patch time begins. However, in other embodiments, the miter is only applied to noise occurring in the contact patch, as described above with respect to Figure 6.

[0088] Figure 8 shows one example of the effects of noise on measured rotation times. In some examples, significant noise outside the contact patch C can be detected and removed using measurement of multiple consecutive tire revolutions. As shown in Graph 802 of Figure 8, the noise filtering process on the digital voltage signal resulting from a significant noise event, depicted as segment 803, in multiple consecutive rotations show variation in the tire rotational time, referred to as irotn. Graph 804 shows the filtered digital voltage including the significant noise event as shown by segment 803. The tireDocket No. P13305PC00 rotational times of Trot2 and Trots shown in Graph 804 are from significant noise events which do not accurately represent the duration of a tire rotation. As part of the noise filtering analysis, the microcontroller 108 retrieves data from the memory 116 about the characteristics of the vehicle. The microcontroller 108 or an external computing device (as will be described herein with respect to Figure 9) may analyze this data to predict the potential physical and non-physical behaviour of the vehicle, and compare it with the results of digital voltage signal to determine if the results are reasonable for the vehicle characteristics. An analysis of the rotational times of the tire during these multiple consecutive rotations can show variation in the measured speed over consecutive revolutions. These speed variations are almost always non-physical because speed changes of that magnitude would require impossible forces to happen. The analysis of the rotational times of the tire during these multiple consecutive rotations enables the removal of noise events through lowering the threshold as described by Figure 7, and combining tire rotational times like Trot2 and Trots shown in Graph 804 which are a result of significant noise events. In some examples, similar analyses can also be done for the contact patch time to remove noise.

[0089] Figure 9 depicts a diagram of a computing device 900 for monitoring tire performance. The computing device 900 comprises a wireless transmitter 904 which is in communication with the sensor unit 100 of Figure 1 . The wireless transmitter 904 is further connected to a processor 908 which is configured to determine the tire load and tire wear. The processor 908 may comprise instructions 912 and a memory 916. The computing device 900 may be located anywhere onboard the vehicle. The computing device 900 may comprise part of the vehicle’s onboard computing system. The computing device 900 may include a GPS (Global Positioning System) or GNSS (Global Navigation Satellite System) module 920. In some embodiments the computing device 900 may be connected to a battery or the battery of the vehicle for a power supply. In some examples the computing device 900 may be powered by solar energy or another renewable energy sources. In another example the computing device 900 may also be a portable electronicDocket No. P13305PC00 device such as a laptop or phone.

[0090] In the example shown in Figure 9, the computing device 900 comprises the wireless transmitter 904 which receives the signal data from the sensor unit 100. The wireless transmitter 904 may use one or more wireless communication protocols including but not limited to Bluetooth™ and Bluetooth™ Low Energy technology, Wi-Fi, Radio, and Cellular systems.

[0091] In the example shown in Figure 9, the computing device 900 comprises the processor 908 which is configured to receive the signal data from the wireless transmitter 904 and compute a tire performance metric from the signal data. The processor 908 may be implemented as one or more multi-core processors or a plurality of processors, and may include one or more graphics processing units (GPUs). The processor 908 may be programmed to determine a contact length and contact angle of the tire based on the signal data received from the wireless transmitter 904. Following this, the processor 908 may be programmed to determine the tire load using the contact length and signal data received by the wireless transmitter 904. Processor 908 may also be programmed to determine the tire wear from the signal data received from the wireless transmitter 904.

[0092] In the example shown in Figure 9, the computing device 900 comprises the instructions 912 executed by the processor 908. The instructions 912 include programming instructions which may be received and executed by the processor 908 to calculate the tire load and tire wear. Instructions may communicate with processor 908 and memory unit 916.

[0093] In the example shown in Figure 9, the computing device 900 comprises the memory 916 which communicates with the processor 908. The memory 916 communicated with the processor 608 so it may execute its programming instructions. The memory 916 may include volatile and non-volatile memory. Non-volatile memory can be based on any persistent memory technology, such as an Erasable Electronic Programmable Read Only Memory (“EEPROM”), flash memory, solid-state hard diskDocket No. P13305PC00(SSD), other type of hard-disk, or combinations of them. Volatile memory is based on any random-access memory (RAM) technology. Volatile memory can be based on a Double Data Rate (DDR) Synchronous Dynamic Random-Access Memory (SDRAM).

[0094] In the example shown in Figure 9, the computing device 900 comprises the GPS module 920 which is configured to measure the positioning and speed of the vehicle. GPS module 920 may provide location, time, weather, and velocity data from the vehicle via a satellite-based navigation system. GPS Module 920 may cross-reference the location of the vehicle with digital maps retrieved from the memory 116 which can include data on road networks, traffic data, speed limits, and road restrictions. The GPS Module 920 may include a Navigation GPS System, GPS Tracking System, Smart Vehicles GPS, other GPS systems, or a combination thereof.

[0095] In some examples, the computing device 900 further includes a user interface configured to receive user inputs and display information to a user.

[0096] Figure 10 depicts a method of a computing device for monitoring tire performance, according to one example. In the example shown in Figure 10, the method 1000 is performed at the computing device 900 which calculates one or more tire performance metrics. As described herein, the tire performance metric may include tire load, tire wear, and combinations thereof.

[0097] Block 1004 depicts receiving signal data. In the example shown in Figure 10, block 1004 is performed by the computing device 900 which receives signal data from the sensor unit 100 via the wireless transmitter 904. Block 1004 may occur in response to the wireless transmitter 112 outputting signal data at block 324 in Figure 3. Signal data received at block 1004 includes the recorded times. The signal data may further include the centripetal acceleration, the digital voltage signal, intervals Tn, temperature data, and pressure data. At block 1004, the signal data is sent to the processor 908. At part of block 1004 the signal data may be stored in the memory 916.

[0098] Block 1008 comprises determining the tire wear. In the example shown inDocket No. P13305PC00Figure 10, block 1008 can be performed by the processor 908. The tire wear, Wear, represents the tire gradually losing material over time from friction, and the material reduction results in the tire radius decreasing over time. The reduction in material results in the tire rotating faster relative to the vehicle speed. Tire wear is determined at the processor 908 using the signal data. Tire wear is determined by comparing a rotational rate of the tire, Trotation, with the speed of the vehicle, determined from signal data. An apparent circumference (Ca) of the tire is calculated using the speed of the vehicle (Vgps) determined from the GPS module. Equation 2 shows one example of the calculation conducted by the processor 908 to determine the apparent circumference Ca.Equation 2

[0099] In the example shown in Figure 10, the processor 908 may determine an initial apparent circumference (Ca,o) of the tire. When the tire is replaced, the initial apparent circumference can be determined from an initial accelerometer measurement. The apparent circumference, Ca, will decrease over time as tire wear occurs. When a new tire is installed, an initial tire radius is also measured or given based on manufacturer specifications. The processor 908 may recall stored tire data from the memory 916 to determine the tire wear using the initial tire radius (Ro) initial apparent circumference Ca,o, and the apparent circumference Ca. Equation 3 shows one example of the calculation conducted by the processor 908 to determine the tire wear (Wear).Equation 3

[0100] Block 1012 comprises determining the contact angle. In the example shown inDocket No. P13305PC00 figure 10, block 1012 is performed by the processor 908. At block 1012, the processor 908 determines the contact angle (Ocontact.) using the signal data obtained from the accelerometer 104 and the microcontroller 108. Equation 4 shows one example of the calculation conducted by the processor 908 to determine the contact angle Ocontact. The output of the change in the digital voltage signal determined by the microcontroller 108 may include the time differences between each digital voltage signal, resulting in an array of time differences between each digital voltage signal change. This array is defined from an interval which is the difference between the recorded times of digital voltage signal changes, defined as TI, where i is a number of interval changes that has been recorded. A further array is defined by a further interval which is the number of interval changes that has been recorded plus one, TI+I. The array of time differences can be used to determine the time spent in the contact patch (Tcontact) and a full tire revolution time (-[revolution). A full tire revolution time -[revolution is equal to time outside the contact patch added to the time inside the contact patch, or TI+I plus TI+2. The contact angle (Ocontact) may be calculated according to Equation 4 using the contact patch time (Tcontact) and the full tire revolution time (Trevolution).Equation 4The full revolution time (Trevolution) can also be determined from an average of multiple consecutive revolutions to improve precision.

[0101] Block 1016 comprises determining the contact length. At block 1016, the processor 908 determines the contact length (Lcontact). Equation 5 shows one example of the calculation conducted by the processor to determine the contact length Lcontact. The processor 908 may recall stored data from the memory 916 on each tire including a tire length (Rtire) and determines the contact length Lcontact using the contact angle (Ocontact).L contact ^tire^ contactEquation 5Docket No. P13305PC00

[0102] Block 1020 comprises determining the tire load. In the example shown in Figure 10, block 1020 can be performed by the processor 908. At block 1020, the processor 908 may determine the tire load. The processor 908 uses signal data including the tire pressure obtained from pressure sensor 120 to determine the tire load. Equation 6 shows one example function conducted by the processor 908 to determine the tire load. The tire load represents an area of the tire in contact with the road along with the tire pressure. The processor 908 can recall stored tire model data (tiremodei) from the memory 916 which can include a tire width (Wtire) and tire tread pattern, to determine the tire load. The processor 908 can also recall stored data on the location of sensor unit 100 including the position, orientation, and shape of the sensor unit 100, identified as Lsensor, to determine the tire load. In one example, the stored data can represent deviations from the ideal, including the sensor not being a point sensor, but having a significant size relative to measurement, any deviations from the rectangular model of the contact patch, and any non-zero rigidity of the tire side walls bearing a small amount of weight. The processor 908 can recall other data including the tire wear (Wear) a tire pressure (Ptire) and temperature (Ttire) to determine the tire load. The contact length Lcontact and the tire wear Wear can be used to give information on changes to the tire’s contact area shape. The processor 908 can recall weather data (Weather) including but not limited to the temperature, humidity, and precipitation from the GPS module 920 or the wireless transmitter 904 which communicates with a server to receive the data. The temperature Ttire can be obtained from the temperature sensor 124 and may be corrected based on the weather which may inform the tire material rigidity and the shape of the contact area. Block 1020 shows the processor 908 can determine the tire load based on one or more of the tire model data tiremodei, sensor location Lsensor, contact length Lcontact, tire wear Wear, Weather, temperature Ttire, and the tire pressure Ptire.Load ti emodel> ^sensor’ ^contact’ ^ear> Weather, T^ire, ^PtireEquation 6Docket No. P13305PC00

[0103] In examples where the computing device 900 includes a user interface, the method 1000 may further include outputting the tire performance metrics at the user interface.

[0104] Figure 11 depicts a diagram of a system for monitoring tire performance. The system 1100 includes the sensor unit 100 of Figure 1 connected to the computing device 900 of Figure 9. The system further includes a network 1104 configured to connect the computing device 900 to a server 1108 which is remote from the vehicle. The system 1100 may further include a computing device 1112 connected to the server 1108. The system 1100 may further include a computing device 1116 connected to the network 1104.

[0105] The network 1104 is configured to transfer signal data and tire performance metrics between the computing device 900 and the server 1108. In one example, the server 1108 may send and receive data on one or more tire performance metrics from the computing device 900. The server 1108 may receive GPS data from GPS module 920. GPS data from GPS module 920 may be analyzed along with tire performance metrics from computing device 900 to determine if there are driving routes that may impact tire wear differently. In some examples, the computing device 900 may assign a unique identifier to the data before sending it to the server 1108. The unique identifier comprises data associated with tire performance metrics. The unique identifier may comprise data associated with one or more tires. The server 1108 may send data back to the computing device 900 after processing the data. In another example, after processing the data at the server 1108, the data may be sent back to the computing device 900 to identify to the user that the tire is worn or that the tire load is too heavy. In some examples, the computing device 900 is configured to transmit signal data from sensor unit 100 to the server 1108. The server 1108 performs the method 1000 to determine tire performance characteristics. Examples of a network 1104 may include Local Area Network (LAN), Wireless network (wi-fi), Wide Area Network (WAN), and Personal Area Network (PAN). Network 1104 can include any wired and / or wireless network topology. Examples of wired network technologies may include ethernet (LAN) and powerline networking. ExamplesDocket No. P13305PC00 of wireless networks may include Wi-Fi, Bluetooth, and Zigbee & Z-Wave.

[0106] The server 1108 is located remotely from the vehicle. The server 1108 may perform the method 1000 depicted in Figure 10. The server 1108 may be equipped with a multi-core, high performance processor, memory, network interface, and storage system. Examples of server processors can include x86-Based, ARM-Based, RISC- Based, and GPU-Based processors. The server 1108 may be equipped with one or more databases for storing unique identifiers which comprise tire performance metrics and signal data. The server 1108 may be configured to determine the tire load and tire wear using the signal data from the sensor unit 100. In one example, the computing device 900 may send signal data, including the recorded times of digital voltage signal changes, to the server for processing. The server may receive signal data, determine the contact angle, determine the contact length, determine the tire load, and determine the tire wear, similar to the method 1000 described by Figure 10.

[0107] In the example shown in Figure 11 , the sensor unit 100 is connected to the computing device 900 and configured to convey the signal data to the server 1108 via the computing device 900 and the network 1104. In other examples, the computing device 900 is omitted, and the sensor unit 100 is configured to convey the signal data to the server 1108 via the network 1104.

[0108] The computing device 900 may perform the method of Figure 10. Computing device 900 may be connected to sensor unit 100 and the server 1108 via the network 1104. In the example shown in Figure 11 , the system 1100 comprises the computing device 1112 which is connected to the server 1108. The computing device 1112 may be configured to receive one or more of signal data and tire performance metrics from the server 1108. The computing device 1112 may be located anywhere. In one example the computing device 1112 may also be a portable electronic device such as a laptop or phone.

[0109] In the example shown in Figure 11 , the system 1100 comprises the computingDocket No. P13305PC00 device 1116 which is connected to the network 1104. The computing device 1116 may be configured to receive one or more of signal data and tire performance metrics from the network 1104. The computing device 1116 may be located anywhere. In one example the computing device 1116 may also be a portable electronic device such as a laptop or phone.

[0110] In view of the above, it will now be apparent that variant, combinations, and subsets of the foregoing embodiments are contemplated. It is to be appreciated by a person of skill in the art that the computing device 900 could be connected to multiple sensor units. For example, while Figure 9 was discussed above in relation to a single sensor unit associated with one tire, in other examples, the computing device 900 may receive signal data from a plurality of sensor units 100 associated with a plurality of tires. Similarly, the system of Figure 11 may include a plurality of sensor units associated with one or more vehicles and the server 1108 may be configured to receive signal data or tire performance metrics associated with a plurality of tires and / or a plurality of vehicles. A vehicle may have multiple tires and the method 300 can be applied to each of the tires.

[0111] It will now be apparent to a person of skill in the art that the present specification affords certain advantages over the prior art. For example, in the method 300, the microcontroller 108 remains in the inactive mode until it detects a change in the digital voltage signal. This allows that the microcontroller 108 can be in a low power state when it is in the inactive mode. This function can allow the sensor unit 100 to monitor tire wear continuously while it does not require an uninterrupted acquisition of data from the accelerometer 104. This can reduce the power supply needs of the sensor unit 100 and preserve battery life. By reducing the power supply requirements of the sensor unit 100, this can reduce the size of the battery in the sensor unit 100. This can provide a costsaving and more scalable solution for tire monitoring in vehicles. A reduction in power supply needs may also lead to a reduction in maintenance costs. In some examples, a sensor unit 100 and power supply can last for a longer time period than other tire performance systems, saving the user money on equipment and service charges toDocket No. P13305PC00 replace a tire performance monitoring system.

[0112] The sensor unit 100 with a power supply that lasts for a long time can enhance vehicle performance. In some examples, the system for monitoring tire performance can outlast the lifetime of the tire and vehicle, providing the user with regular data on the tire load and tire wear. This data can inform the user of important information on the lifespan and safety of their tires. In some examples, providing the user with tire load information may help avoid overloading and prevent tire blowouts due to excessive weight. Tire load data may inform the user of improper load distribution on the tires which can result in uneven wear and higher fuel consumption. Tire load data may be used to improve fuel efficiency by informing users when vehicle tires are overloaded. In some examples, commercial vehicles may use tire load data to ensure vehicles are in compliance with regulations and avoid overloading fines. In other examples, providing a user with tire wear data can provide enhanced vehicle safety through reducing skidding risks in wet or icy conditions. Uneven and overly worn tires may result in increased fuel consumption from loss of traction and resistance. Tire monitoring ensures even tire wear, reducing the frequency of replacements, which gives lower maintenance costs. Tire wear data may be used in conjunction with stored GPS data to analyze route seventy to determine whether different driving routes impacts tire wear more than others, which can result in maintenance cost reductions through choosing lower wear driving routes. Tire load and tire wear monitoring can result in positive environmental impacts. Less frequent tire replacements will reduce the quantity of tires used and disposed over a vehicle’s lifetime, resulting in a reduction in the rubber and microplastic pollution that occurs from tire disposal. Fuel efficiency benefits are obtained from proper tire loads and reduced tire wear. Higher fuel efficiency has reduced environmental impacts from the reduction in carbon emissions from fuel combustion and through lowering fuel consumption and demand.

[0113] The many features and advantages of the invention are apparent from the detailed specification and, thus, it is intended by the appended claims to cover all suchDocket No. P13305PC00 features and advantages of the invention that fall within the true spirit and scope of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

Claims

Docket No. P13305PC00CLAIMSWhat is claimed is:1 . A sensor unit for monitoring tire performance comprising: a contact patch sensor configured to: detect a deformation of a tire; determine whether the deformation of the tire is above or below a threshold; and output a digital voltage signal when the deformation of the tire is above the threshold; and a microcontroller configured to: operate in an inactive mode to reduce power consumption; operate in an active mode in response to a change in the digital voltage signal and record a time when the digital voltage signal changes; and return to the inactive mode after recording the time.

2. The sensor unit of claim 1 wherein the contact patch sensor comprises an accelerometer, wherein detecting the deformation of the tire comprises measuring a centripetal acceleration, and wherein the accelerometer is configured to output the digital voltage signal when the centripetal acceleration is above the threshold.

3. The sensor unit of claim 2 further comprising a wireless transmitter to convey signal data, the signal data comprising the recorded time from the microcontroller.Docket No. P13305PC004. The sensor unit of claim 2 further comprising a temperature sensor configured to measure a temperature of the tire, wherein the signal data further comprises the temperature of the tire.

5. The sensor unit of claim 2 further comprising a pressure sensor configured to measure a tire pressure, wherein the signal data further comprises the tire pressure.

6. The sensor unit of claim 2 further comprising a battery configured to supply power to the sensor unit.

7. The sensor unit of claim 2 where the microcontroller comprises a timer which is configured to operate continuously in the active mode and the inactive mode, wherein the recorded time is output from the timer.

8. The sensor unit of claim 2 where the accelerometer is configured to only output the digital voltage signal when the centripetal acceleration is above or below the threshold for a filtering period.

9. A computing device for monitoring tire performance, the computing device comprising: a wireless transmitter configured to receive signal data from a sensor unit connected to a tire of a vehicle and configured to output a digital voltage signal when a deformation of a tire is above a threshold, wherein the signal data comprises a start time and end time of the digital voltage signal; and a processor configured to receive the signal data from the wireless transmitter and compute a contact patch time based on the start time and end time of the digital voltage signal.Docket No. P13305PC0010. The computing device of claim 9, wherein the computing device is positioned in or connected to the vehicle.11 .The computing device of claim 9, wherein the computing device is remote from the vehicle and configured to receive the signal data via a network.

12. The computing device of claim 10 further comprising a global positioning system (GPS) device configured to measure a velocity of the vehicle; wherein the signal data further includes the velocity of the vehicle.

13. The computing device of claim 12, wherein the processor is further configured to compute a full tire revolution time based on the start time and end time.

14. The computing device of claim 13, wherein the processor is further configured to determine an apparent circumference of the tire based on the velocity of the vehicle and the full tire revolution time.

15. The computing device of claim 13, wherein the processor is configured to compute the apparent circumference according to: r velocity of the vehicle apparent circumf erence = - j - . full tire revolution time16. The computing device of claim 13, wherein the processor is configured to retrieve an initial apparent circumference of the tire stored in the memory at the computing device.

17. The computing device of claim 16, wherein the processor is further configured to compute a tire wear based on an initial tire radius, the initial apparent circumference and the apparent circumference.Docket No. P13305PC0018. The computing device of claim 17, wherein the processor is further configured to compute the tire wear according to:Tire wear =. ... i (initial apparent tire circumference- apparent tire circumference) initial tire radius - . initial apparent tire circumference19. The computing device of claim 13 wherein the processor is configured to compute a contact angle based on the contact patch time and the full tire revolution time.

20. The computing device of claim 19 wherein the processor is configured to compute the contact angle according to:, , , „ „ contact patch time contact anqle = 2 / 7 - . full tire revolution time21. The computing device of claim 20, wherein the processor is further configured to determine a contact length based on the contact angle and a tire length stored in memory at the computing device.

22. The computing device of claim 21 wherein the processor is further configured to compute the contact length according to: contact length = tire length X contact angle .

23. The computing device of claim 22, wherein the processor is further configured: retrieve a tire model data, a sensor location, and a weather data stored in the memory at the computing device; and compute a tire load based on the tire model data, the sensor location, the contact length, the tire wear, the weather, a temperature, and a tire pressure.Docket No. P13305PC0024. The computing device of claim 23, wherein the processor is further configured to determine the tire load according to a function:Tire load= F(tire model data, sensor location, contact length, tire wear, weather, temperature)x tire pressure.

25. A system for monitoring tire performance comprising: a sensor unit connected to a tire of a vehicle, the sensor unit including a contact patch sensor, a microcontroller, and a wireless transmitter; the contact patch sensor configured to: detect deformation of a tire; determine whether the deformation of the tire is above or below a threshold; and output a digital voltage signal when the deformation of the tire is above the threshold; the microcontroller configured to: operate in an inactive mode to reduce power consumption; operate in an active mode in response to the digital voltage signal starting or ending, and record a start time or end time of the digital voltage signal; and return to the inactive mode after recording the time. the wireless transmitter configured to convey signal data, the signal data comprising the start time or end time; a computing device connected with the vehicle, the computing device comprising a wireless transmitter configured to receive the signal data from the sensor unit and convey the signal data over a network; and a server comprising a processor and configured to receive the signal data via theDocket No. P13305PC00 network and compute a contact patch time based on the start time and end time of the digital voltage signal.

26. The sensor unit of claim 25 wherein the contact patch sensor comprises an accelerometer, wherein detecting the deformation of the tire comprises measuring a centripetal acceleration, and wherein the accelerometer is configured to output the digital voltage signal when the centripetal acceleration is above the threshold.

27. A method of monitoring tire performance using a sensor unit comprising a contact patch sensor and a microcontroller, the method comprising: detecting a deformation of a tire with the contact patch sensor; determining whether the deformation of a tire is above or below a threshold; outputting a digital voltage signal from the contact patch sensor when the deformation of a tire is above the threshold; operating the microcontroller in an inactive mode to reduce power consumption; operating the microcontroller in an active mode in response to a change in the digital voltage signal and recording a time when the digital voltage signal changes; and returning the microcontroller to the inactive mode after recording the time.

28. The method of claim 27 wherein detecting the deformation of the tire with the contact patch sensor comprises measuring a centripetal acceleration with an accelerometer, and outputting the digital voltage signal from the accelerometer when the centripetal acceleration is above the threshold.Docket No. P13305PC0029. The method of claim 28 further comprising conveying signal data using a wireless transmitter associated with the sensor unit, the signal data comprising the recorded time from the microcontroller.

30. The method of claim 28 further comprising measuring a temperature of the tire using a temperature sensor associated with the sensor unit, wherein the signal data further comprises the temperature of the tire.31 . The method of claim 28 further comprising measuring a tire pressure using a pressure sensor associated with the sensor unit, wherein the signal data further comprises the tire pressure.

32. The method of claim 28 further comprising supplying power to the sensor unit using a battery associated with the sensor unit.

33. The method of claim 28 further comprising operating a timer associated with the microcontroller continuously in the active mode and the inactive mode, wherein the recorded time is output from the timer.

34. The method of claim 28 further comprising only outputting the digital voltage signal from the accelerometer when the centripetal acceleration is above or below the threshold for a filtering period.

Images