FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
& THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
1. Title of the invention: DETERMINING CONTACT PATCH ANGLE OF TYRES
2. Applicant(s)
NAME NATIONALITY ADDRESS
CEAT LIMITED Indian RPG HOUSE, 463, Dr. Annie Besant Road, Worli, Mumbai - Maharashtra 400 030, India
3. Preamble to the description
COMPLETE SPECIFICATION
The following specification particularly describes the invention and the manner in which it
is to be performed.

TECHNICAL FIELD
[0001 ] The present subject matter relates, in general, to monitoring tyre of
a vehicle, in particular, to determining a contact patch length of the tyre of the vehicle.
BACKGROUND
[0002] Tyres play an important role in dynamics of a vehicle. Among
other things, they help in providing lateral, longitudinal & radial forces to the vehicle required for tracking, steering, traction and providing stability to the vehicle. Therefore, various parameters of the tyre are monitored so that the corrective measures, if required, may be taken.
[0003] Generally, the various parameters of a tyre are measured by sensors
installed on the tyre. To determine and measure the various parameters of the tyre, the contact patch length of the tyre needs to be determined. The contact patch length of the tyre is an area of the tyre that comes in contact with a surface on which the tyre is moving. The sensors come within the area of the contact patch once every rotation of the tyre. Determination of the contact patch length of the tyre in an accurate manner is desirable in order to measure the various parameters of the tyre of the vehicle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The detailed description is described with reference to the
accompanying figures. In the figures, the left-most digit of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference the same elements.

[0005] Figure 1 illustrates an environment 100 for determining contact
patch angle of a tyre, in accordance with an example implementation of the present subject matter;
[0006] Figures 2 illustrates a schematic diagram of system for determining
contact patch angle of a tyre, in accordance with another example of the present
subject matter.
[0007] Figure 3 illustrates examples of data points as recorded by a
sensing unit.
[0008] Figure 4 describes a method of determining contact patch angle of
a tyre, in an example implementation of the present subject matter.
DETAILED DESCRIPTION
[0009] Contact patch length is used for determining and monitoring
parameters of the tyre. For example, the length of the contact patch may indicate the loading of the vehicle. The pressure exerted on the tyres may be accurately determined by monitoring the contact patch length of the tyre. The contact patch length of the tyre may be determined by measuring a contact patch angle of the tyre. The contact patch angle is an angle formed at a center of the tyre by an area of the tyre which is in contact with the surface on which the tyre is rotating. Conventional techniques are often inaccurate in measuring the contact patch angle of the tyre. None of the conventional techniques offers techniques for precise measurement of the contact patch angle of the tyre.
[0010] According to an example implementation of the present subject
matter, techniques for accurately measuring the contact patch length of the tyre is described. According to the present subject matter, a first number of data points is detected by a sensing unit located on a tyre of the vehicle. The first number of data points is a total number of data points recorded in a full rotation of the tyre. Each of the data point is a measurement of a tyre parameter recorded by the sensing unit.

[0011] Further, a second number of data points out of the first number of
data points is ascertained. The second number of data points is a total number of data points recorded by the sensing unit when an area of the tyre containing the sensing unit comes in contact with the tyre. Thereafter, based on the first number of data points and the second number of data points, a contact patch angle of the tyre is computed. The contact patch angle is an angle formed at a center of the tyre by an area of the tyre which is in contact with the surface on which the tyre is rotating.
[0012] Thus, according to the present subject matter, after the contact
patch angle of the tyre is determined, the contact patch angle of the tyre can be used to determine the contact patch length of the tyre. The accurate determination of the contact patch angle and contact patch length results in accurate measurement of the parameters of the tyre. The contact patch length is also used in various algorithms, such as load determination algorithm, dynamic radius determination algorithm etc.
[0013] It should be noted that the description and the figures merely
illustrate the principles of the present subject matter along with examples described herein and, should not be construed as a limitation to the present subject matter. It is thus understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present subject matter. Moreover, all statements herein reciting principles, aspects, and implementations of the present subject matter, as well as specific examples thereof, are intended to encompass equivalents thereof.
[0014] Figure 1 illustrates an environment 100 for determining a contact
patch angle 102 of tyre 104, in accordance with an example implementation of the present subject matter. The environment 100 comprises a system 106 coupled with the sensing unit 108.
[0015] The system 106 comprises a data point determining engine 110 and
a contact patch monitoring engine 112. The data point determining engine 110 determines a first number of data points of a tyre of a vehicle. The first number of

data points may be measured by the sensing unit 108 in a full rotation of the tyre 104 and the measurements may be provided to the data point determination engine110. The first number of data points is a measurement of a tyre parameter recorded by the sensing unit 108. In an example, the data points may be a measure of pressure of the tyre at regular intervals. The measure of pressure of the tyre may be measured by the sensing unit 108. In an example, there may be 100 data points in a full rotation of the tyre 104.
[0016] Further, the data point determining engine 110 ascertain a second
number of data points out of the first number of data points. The second number of data points is a total number of data points recorded by the sensing unit 108 when an area of the tyre 104 containing the sensing unit 108 comes in contact with a surface on which the tyre 104 is rotating.
[0017] After the first number data points and the second number of data
points are determined, the contact patch monitoring engine 112 determines the contact patch angle 102 of the tyre 104. The contact patch angle 102 is formed at the center of the tyre 104. The contact patch encloses a contact patch length 114 of the tyre 104.
[0018] Figures 2 illustrates the system 106, in accordance with an example
of the present subject matter.
[0019] The system 106, among other things, includes a memory 202 and
engine(s) 206. The memory 202 may include any computer-readable medium including, for example, volatile memory (e.g., RAM), and/or non-volatile memory (e.g., erasable programmable read-only memory (EPROM), flash memory, etc.).
[0020] The system 106 is coupled the sensing unit 108. In an example, the
sensing unit 108 may comprise sensors, such as gyroscope, accelerometers, pressure sensors, temperature sensors etc. In an example, the sensing unit 108 may comprise an enclosure and the sensor may be coupled in the sensor assembly using a poke-yoke arrangement. For example, the sensor may have two or more fins which may couple with grooves in the enclosure of the sensor assembly. In an

example, the two or more fins may have different shape such that a specific fin fits into a specific groove. Thus, this arrangement ensures that the sensor is fitted in the sensor assembly in right orientation.
[0021] The engine(s) 206 may be implemented as a combination of
hardware and programming (for example, programmable instructions) to implement certain functionalities of the engine(s) 206, such determining contact patch angle. In examples described herein, such combinations of hardware and programming may be implemented in several different ways. For example, the programming for the engine(s) 206 may be processor executable instructions stored on a non-transitory machine-readable storage medium and the hardware for the engine(s) 206 may include a processing resource (for example, implemented as either a single processor or a combination of multiple processors), to execute such instructions. In the present examples, the machine-readable storage medium may store instructions that, when executed by the processing resource, implement engine(s) 206. In such examples, the system 106 may include a machine-readable storage medium storing the instructions and the processing resource to execute the instructions, or the machine-readable storage medium may be separate but accessible to the system 106 and the processing resource. In other examples, engine(s) 206 may be implemented by electronic circuitry. In an example, in addition to a data point determining engine 110, a contact patch monitoring engine 112, a load determination engine 208, and the engine(s) 206 may also comprise other engine(s) 210 that supplement functions of the system 106.
[0022] Data 212 serves, amongst other things, as a repository for storing
data that may be fetched, processed, received, or generated by the engine(s) 206. The data 212 comprises other data 214 corresponding to the other engine(s) 210. In the illustrated example, the data 212 of the system 106 also comprises data points data 216 and contact patch data 218.
[0023] In operation, the data point determining engine 110 determines the
first number data points of the tyre of the vehicle. As explained earlier, the first number of data points are measurements of tyre parameter as recoded by the

sensing unit 108. In an example, the parameter may be speed, acceleration, pressure of the tyre. Further, the data point determining engine 110 determines a second number of data points out of the first number of data points. The second number of data points are the number of data points recorded by the sensing unit 108 when a part of the tyre 104 containing the sensing unit 108 comes in contact with a surface on which the tyre is rotating. In an example, the first number of data points may be 100 while the second number of data points may be 10.
[0024] After the first number of data points and the second number of data
points are determined, the contact patch monitoring engine 112 determines a contact patch angle based on the first number of data points and the second number of data points. To determine the contact patch angle, the contact patch monitoring engine 112 divides 360 degrees by the first number of data points and thereafter multiply the result with the second number of data points.
[0025] As understood, the first number of data points is recorded for a full
rotation of the tyre, i.e., for 360 degrees of rotation of the tyre. In other words, the first number of data points is recorded for whole circumference (area) of the tyre. Dividing 360 degree by the first number of data points gives degree of tyre per number of data points. Thereafter, multiplying the second number of data points by degree of tyre per number of data points gives the contact patch angle of the tyre as the second number of data points corresponds to the measurements recorded for the area of tyre which is in contact with the surface.
[0026] Considering an example, if the first number of data points is 100
and the second number of data points is 10, the contact patch angle is determined as below:
Degree per number of data points=360/(100) first number of data points. Contact patch angle= 3.6 (Degree per number of data points) x 10(second
number of data points)
= 36 degrees.

[0027] In an example, the number of first data points and the number of
second data points may be stored in the data points data 216. The contact patch monitoring engine 112 may access the data points data 216 to retrieve the first number of data points and the second number of data points to calculate the contact patch angle. The contact patch angle may be stored in the contact patch length data 218.
[0028] The contact patch angle may be used by the load determination
engine 208 to determine a dynamic radius if a wheel to which the tyre is coupled. The dynamic radius of the wheel is indicative of change in real time radius of the wheel due applied load on the tyre. To determine the dynamic radius of the wheel, the load determination engine 208 determines a contact patch length of the tyre. The contact patch length can be determined by the contact patch angle. The load determination engine 208 divides the total circumferential length of the tyre by 360 to derive length per unit degree. Thereafter, the load determination engine 208 multiples the length per unit degree with the contact patch angle to determine the contact patch length of the tyre. In an example, the load determination engine 208 may access the contact patch data 218 to retrieve the contact patch angle of the tyre. The larger the contact patch length, the lesser would be the dynamic radius (more load), and the lesser is the contact patch length the larger would be the dynamic radius (less load).
[0029] Figure 3 shows an example of data points recorded by a sensing
unit. A contact patch angle of a tyre needs to be determined based on the data points. The data points captured by a sensing unit is shown on graph 302. A plurality of data points 304 between the points 306-1 and 306-2 indicates the first number of data points. Further, data points between the points 306-3 and 306-1 are the second number of data points that are recorded when an area of the tyre containing the sensing unit touches a surface. After, the first number of data points and the second number of data points are determined, the contact patch angle is determined based on the techniques as described above.

[0030] Figure 4 describes a method 400 of determining a contact patch
angle of a tyre in an example implementation of the present subject matter. The order in which the method 400 is described is not intended to be construed as a limitation, and any number of the described method blocks may be combined in any order to implement the method 400, or an alternative method.
[0031] At block 402, a first number of data points is determined by the
sensing unit. The first number of data points is a total number of data points recorded in a full rotation of the tyre, and wherein each of the data points is a measurement of a tyre parameter recorded by the sensing unit. In an example, the tyre parameter may be tyre pressure, tyre temperature, load on tyre, angle of the contact patch with centre of the tyre, etc.
[0032] At block 404, the second number of data points is ascertained out
of first number of data points. The second number of data points is a total number of data points recorded by the sensing unit when an area of the tyre containing the sensing unit comes in contact with a surface on which the tyre is rotating. The method thereafter proceeds to block 306.
[0033] At block 406, a contact patch angle is determined based on the
first number of the data points and the second number of data points. The contact patch angle is an angle formed at a center of the tyre which encloses an area of the tyre which is in contact with the surface on which the tyre is rotating. The contact patch angle may be thereafter used to calculate contact patch length and dynamic radius of the trye. Further, the contact patch length data may be provided to a load determination engine. The load determination engine may be contained within an electronic control unit of the vehicle and may use the contact patch length data to calculate the load exerted on the tryes of the vehicle.
[0034] Although implementations of ascertaining of a misalignment in
a tyre have been described in a language specific to structural features and/or applications, it is to be understood that the present subject matter is not limited to the specific features or applications described. Rather, the specific features and applications are disclosed as exemplary implementations.

I/We Claim:
1. A method comprising:
determining a first number of data points detected by a sensing unit located on a tyre of a vehicle, wherein the first number of data points is a total number of data points recorded in a full rotation of the tyre, and wherein each of the data points is a measurement of a tyre parameter recorded by the sensing unit;
ascertaining a second number of data points out of the first number of data points, wherein the second number of data points is a total number of data points recorded by the sensing unit when an area of the tyre containing the sensing unit comes in contact with a surface on which the tyre is rotating; and
computing, based on the first number of data points and the second number of data points, a contact patch angle of the tyre, the contact patch angle being an angle formed by an area of the tyre in contact with the surface on which the tyre is rotating with respect to the center of the tyre.
2. The method as claimed in claim 1, further comprising:
determining, based on the contact patch angle, a contact patch length, wherein the contact patch length is a length of the tyre which is in contact with the surface at an instance of time.
3. The method as claimed in claim 1, wherein the tyre parameter is an acceleration of the tyre.
4. The method as claimed in claim 2, further comprising:
providing the contact patch length to a load determination engine of an electronic control unit of the vehicle.
5. A system comprising:
a data point determining engine to:
determine a first number of data points of a tyre of a vehicle, wherein the first number of data points are total number of data points recorded in a

full rotation of the tyre, by a sensing unit attached to the tyre, wherein each of the data points is a measurement of a tyre parameter recorded by the sensing unit;
ascertain a second number of data points out of the first number of data points, wherein the second number of data points is a total number of data points recorded by the sensing unit when an area of the tyre containing the sensing unit comes in contact with a surface on which the tyre is rotating; and contact patch monitoring engine to:
compute, based on the first number of data points and the second number of data points, a contact patch angle of the tyre, the contact patch angle being an angle formed by an area of the tyre which is in contact with the surface on which the tyre is rotating with respect to the center of the tyre.
6. The system as claimed in claim 5, wherein the tyre parameter is one of a speed of the tyre, and pressure exerted on the tyre.
7. The system as claimed in claim 5, wherein the contact patch monitoring engine is to determine, based on the contact patch angle, a contact patch length, wherein the contact patch length is a length of the tyre which is in contact with the surface at an instance of time.
8. The system as claimed in claim 5, wherein the system further comprises
a load determination engine to:
determine, based on the contact patch length, a dynamic radius of the tyre of the vehicle, wherein the dynamic radius is a real time radius of a wheel on which the tyre is coupled; and
calculate, based on the dynamic radius, a load applied on the tyre of the vehicle.

9. The system as claimed in claim 5, wherein the sensing unit comprises:
an enclosure mounted on the tyre; and
sensors mounted in the enclosure wherein the sensors are mounted in the enclosure in a poke-yoke arrangement.
10. The system as claimed in claim 9, wherein the sensors are at least one of an
accelerometer, gyroscope, pressure sensor, and temperature sensor.