Method for improving data transmission by a wheel unit

Abstract

In this method of managing messages transmitted by radio waves per wheel unit (11) to an external electronic unit, "clear zones" are defined – in which the signal can be transmitted without alteration – and "shadow zones" – in which it risks being altered – and a specific transmission strategy is used that optimizes the number of messages in the clear zones. (Fig. 1)

Description

Title of the invention: DESCRIPTION: Method for improving data transmission by a wheel unit

[0001] The present invention relates to the field of electronic modules installed on the wheels of motor vehicles.

[0002] As is known in itself, the wheels of motor vehicles are frequently equipped with electronic modules commonly referred to as "wheel unit", forming part of a "TPMS" (Tire Pressure Monitoring System) type system which allows in particular the monitoring of tire pressure.

[0003] Each wheel unit typically includes various sensors, a microcontroller, a memory, a battery and means of communication with the outside by radio waves.

[0004] The wheel unit can thus transmit useful information to an external electronic unit, representing for example the condition of the tire, the angular position of the wheel, etc.

[0005] The external electronic unit can be the ECU (Electronic Control Unit: vehicle's on-board computer), or any other type of electronic terminal such as a smartphone (multifunction mobile phone).

[0006] Radio wave communication between the wheel unit and the external electronic unit can be disrupted by the presence of metallic or other masses located on board the vehicle: structural elements connecting the wheel to the vehicle, presence of passengers and / or luggage inside the vehicle, etc., creating what are commonly referred to as "black spots".

[0007] These disturbances may have the effect that for certain angular positions of the wheel, the messages transmitted by the wheel unit are not received and / or are truncated, and therefore not usable by the external electronic unit.

[0008] The present invention thus aims in particular to reduce this risk of alteration of the messages transmitted by the wheel unit.

[0009] This objective of the invention is achieved with a method for managing messages transmitted by radio waves from a wheel unit to an external electronic unit in which: - the wheel unit emits a signal at regular angular intervals of the wheel, and assigns a sequence number to each of these intervals, - The external electronic unit detects whether this signal is received or not, - The external electronic unit sends information representing this detection to the wheel unit, or stores this information. - the wheel unit or the external electronic unit deduces the angular intervals - designated as "clear zones" - in which the signal can be transmitted without alteration or with slight alteration, and those - designated as "shadow zones" - in which it risks being altered, - The wheel unit or the external electronic unit extracts a series of indices of angular intervals from clear areas, - the wheel unit or the external electronic unit calculates the common difference of the arithmetic sequence that has the most terms in said sequence, or whose terms correspond to angular intervals allowing optimization of the transmission power of said signal from the wheel unit to the external electronic unit, - the wheel unit emits messages periodically, the duration of the period being equal to the travel time of the wheel unit in each of said intervals, multiplied by said ratio.

[0010] Thanks to these characteristics, the probability of the wheel unit emitting its messages is increased when it is in a clear area, and the risks of alteration of its messages are thus reduced.

[0011] According to other optional features of the present invention, taken alone or in combination:

[0012] - the wheel unit calculates said period using the formula: p is the period of emission of successive messages by the wheel unit; r is the common difference of the arithmetic sequence with the most terms in the sequence of indices of the light zones, for a given number of message emissions; n is the total number of angular intervals; θ is the radius of the circular trajectory of the wheel unit; eta is the radial acceleration of the wheel unit;

[0013] - the external electronic unit evaluates the reception power of said signal, and sends to the wheel unit information representative of this power;

[0014] - for reason (r) we choose the one that allows us to obtain the best score of power transmitted by the wheel unit to the external electronic unit;

[0015] - when the wheel unit emits a signaling message ("broadcast advertisement") " in English), it uses a prime number of regular angular intervals: this allows the wheel unit to emit in different angular intervals from one wheel rotation to another, and therefore in particular not to continue emitting in light areas which would have become shadow areas due, for example, to the movement of masses inside the vehicle;

[0016] - when the wheel unit establishes and maintains a connection with the electronic unit externally, it uses a number of regular angular intervals that is not First: such a number having several divisors, it can be obtained by several arithmetic sequences with different common differences. For example, if we choose 48 regular angular intervals, which are divisible by 2, 3, 4, 6, 8, 12, 16, and 24, the wheel unit can perform 24 emissions per revolution (arithmetic sequence with a common difference of 2), or 16 emissions per revolution (arithmetic sequence with a common difference of 3), or 12 emissions per revolution (arithmetic sequence with a common difference of 4), or 8 emissions per revolution (arithmetic sequence with a common difference of 6), or 6 emissions per revolution (arithmetic sequence with a common difference of 8), or 4 emissions per revolution (arithmetic sequence with a common difference of 12), and so on. Thus, the algorithm can decide which is the best common difference, which will a priori be one of the integer divisors (if we consider that the connection is maintained "indefinitely"). More generally, the ideal is to choose a number that has enough integer divisors;

[0017] - the wheel unit uses common angular intervals for message transmission reporting and sending connection messages;

[0018] - the wheel unit uses distinct angular intervals for message transmission reporting and sending connection messages;

[0019] - the wheel unit adapts the power of said signal according to the ratio between the number of light areas and the number of shaded areas: this allows the electrical power to be consumed only as needed, and thus extends the battery life of the wheel unit;

[0020] - The wheel unit resets the process if too many messages are altered or lost.

[0021] Optionally, when the wheel unit establishes and maintains a connection with the external electronic unit, it can also be provided that the process restarts at the request of the external electronic unit (detection of change of passengers, mass... in the vehicle by means of non-TPMS functions such as weight detectors on the seats for seat belt reminders... or other similar functions).

[0022] The present invention also relates to a wheel unit comprising various sensors, a microcontroller, a memory, a battery and means of communication with the outside by radio waves, the microcontroller being duly programmed to implement the process described above.

[0023] Other features and advantages of the present invention will become apparent from the following description and from the examination of the attached [Fig.1] [Fig.1] which represents an assembly comprising a motor vehicle tire valve equipped with a wheel unit forming part of a TPMS type system.

[0024] Figure [Fig. 1] shows an inflation valve 1 of a motor vehicle tire, comprising a body 3 surmounted by a closing cap 5.

[0025] The body 3 comprises a tubular metal part, the end 7 of which opposite the cap is visible in [Fig.1], this tubular metal part being coated with a flexible material such as synthetic rubber.

[0026] This flexible coating has a groove or shoulder 9 to ensure that the valve is held inside an opening formed in a wheel rim of a motor vehicle (not shown): this is referred to as a "snap-in" type valve.

[0027] The end 7 of the tubular metal part visible in [Fig.1] is intended to open into the chamber defined by the rim and the tire of the motor vehicle, so as to allow the introduction or exit of air to and from this chamber.

[0028] A sensor assembly 11 - usually called a "wheel unit" - is fixed to the valve 3, for example at the end of the tubular metal part 7.

[0029] As is known in itself, this wheel unit 11 includes a pressure sensor inside the chamber defined by the rim and the tire, as well as an accelerometer, a temperature sensor, a microcontroller, a memory, means of communication with an external electronic unit such as the ECU of a motor vehicle and / or a smartphone, and a power supply battery for the whole.

[0030] Conventionally, communication with the ECU can be carried out by high frequencies (GHz and sub-GHz bands) in the direction from wheel unit to ECU, and by low frequencies in the opposite direction.

[0031] More recently, this communication with the ECU as well as with other external electronic units such as smartphones, can be carried out by Bluetooth® LE (“Low Energy”).

[0032] In practice, this communication between the wheel unit and an external electronic unit is disrupted by the presence of shadow zones, linked to the presence of metallic masses (vehicle structure, and in particular wheel / chassis connection) or others (presence of passengers, luggage inside the vehicle, etc.) which form a screen to the circulation of radio waves.

[0033] To limit this risk of disruption and the alteration that may result in the messages transmitted by the wheel unit to the external electronic unit, the following strategy is implemented.

[0034] While the wheel is turning, the wheel unit emits signals to the external electronic unit (ECU or smartphone for example) at regular time intervals.

[0035] Each of the angular positions of the wheel unit corresponding to these signal emissions can be known thanks to the accelerometer integrated into this wheel unit, by means of a synchronized emission localization (or LSE for "Location") type method by synchronized emission” in English), as described for example in patent application WO2012045917A1.

[0036] The external electronic unit checks whether or not it receives these signals, and / or analyzes the power of each of them, and sends back to the wheel unit information representative of this reception and / or this power.

[0037] It is also possible to consider that the wheel unit emits with a progressive power, and that only the minimum power which allowed detection by the external electronic unit is retained.

[0038] This information can be binary digital, of the type 0 if the power received by the external electronic unit is less than a predetermined threshold, and 1 if this power is greater than this threshold.

[0039] This information can also be analog, and indicate the effective power level of the signal received by the external electronic unit.

[0040] A relatively low power level received by the external electronic unit indicates that the wheel unit is in a shadow zone.

[0041] Conversely, a relatively high power level indicates that the wheel unit is in a clear zone.

[0042] The power of the signals used to perform this mapping of shadow and light areas is optimized, so as to limit the electrical consumption of the wheel unit: for example, the power to be used may be considered to be that which is just sufficient to obtain a ratio between the number of shadow areas and the number of light areas which is greater than a predetermined threshold.

[0043] The angular intervals swept by the wheel unit between the emissions of two consecutive signals are numbered by the wheel unit in the order in which they follow one another, as can be seen on the top line of Table 1 below: in this example, during one complete wheel rotation, eleven signals were emitted by the wheel unit, and the wheel unit swept eleven regular consecutive angular intervals, that is to say eleven sectors of the same angle.

[0044] [Tables 1] 1 2 3 4 5 6 7 8 9 10 11 1 1 1 0 0 Û 1 1 1 0 1

[0045] As can be seen on the lower line of this table, the wheel unit associates the information representing the power of the signal received by the external electronic unit, with each of the numbers (indices) of angle intervals concerned: in this example, the shaded areas are therefore the angular intervals 4, 5, 6, 10, and the light areas are the intervals 1, 2, 3, 7, 8, 9, 11.

[0046] The wheel unit then periodically emits, i.e. at regular time intervals, the messages to be transmitted to the external electronic unit.

[0047] The value of this period is chosen to be equal to the time it takes the wheel unit to travel through each of the angular intervals defined above or, in other words, the time taken by the wheel to sweep through each of the angular sectors corresponding to these intervals.

[0048] In concrete terms, this interframe period separating the transmission ("burst") of each message can be calculated using the following formula: 2w / 777 where: p = r- — ■ yRja p is the period of emission of successive messages by the wheel unit; r is the common difference of the arithmetic sequence with the most terms in the sequence of indices of the light areas, for a given number of message emissions; n is the total number of angular intervals; r is the radius of the circular trajectory of the wheel unit; eta is the radial acceleration of the wheel unit.

[0049] For example, if we want the wheel unit to emit six messages with the sequence of indices {1, 2, 3, 7, 8, 9, 11, 12, 13, 14, 18, 19, 20, ...} , the reason r will be 5, with a transmission index of 9 for the first message, 14 for the second, 19 for the third, etc., allowing us to reach 100% transmission success.

[0050] Alternatively, instead of using binary information of type 0 or 1 to characterize the shaded and light areas, we could associate with each angular interval a data representative of the power of the signal transmitted by the wheel unit to the external electronic unit.

[0051] In this case, we would choose for reason r the one which allows us to obtain the best score of powers transmitted by the wheel unit to the external electronic unit.

[0052] Such a score may, for example, consist of the sum of the powers emitted by the wheel unit in each angular interval, but any other method allowing these powers to be taken into account (rather than binary information of type 0 or 1 as indicated above) may be suitable.

[0053] Choosing an interframe as indicated above maximizes the probability that the wheel unit is in a clear area when it sends its messages to the external electronic unit.

[0054] The choice of a prime number for the number of angular intervals (eleven in the example above) is particularly suitable when the wheel unit sends a unidirectional signaling message (broadcast mode).

[0055] This allows the wheel unit to emit in different angular intervals from one wheel rotation to another, and thus not to continue emitting in clear areas which would have become shadow areas due, for example, to the movement of masses inside the vehicle.

[0056] On the other hand, in connected operating mode, i.e. with bidirectional communication between the wheel unit and the external electronic unit, it is preferable to use a number of angular intervals that is not a prime number, and is typically a multiple of 2 or 3, as illustrated by Table 2 below (twelve angular intervals in this particular case):

[0057] [Tables2] 1 2 3 4 5 6 7 8 9 10 11 12 1 1 0 0 0 1 1 1 0 0 1 1

[0058] If too many unidirectional reporting messages (broadcast mode) or bidirectional messages exchanged (connection mode) are altered or lost, the wheel unit may reset the process described above, and thus start again to establish a map of light and dark areas.

[0059] Advantageously, and as illustrated by Table 3 below, a common mapping can be used for the "broadcast" and "connection" modes: in this example, twenty-two angular intervals (numbered from 1 to 22 on the top line of the table) are used for bidirectional messages between the wheel unit and the external electronic unit ("connection" mode: light areas and shadow areas indicated respectively by the 0 and 1 of the middle line of the table), and eleven of these twenty-two angular intervals for unidirectional signaling messages ("broadcast" mode: light areas and shadow areas indicated respectively by the 0 and 1 of the bottom line of the table).

[0060] In the particular example illustrated by Table 3 below, the following rule has been chosen: the value 1 is assigned to an angular interval of signaling message emission when two consecutive intervals of connection message emission themselves have the value 1: such a rule is an example showing that it is not necessary to perform a mapping for each emission mode.

[0061] [Tables3] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 1 1 0 0 0 1 1 1 0 0 1 1 1 1 0 0 0 1 1 1 0 0 1 0 0 1 1 0 0 1 0

[0062] Conversely, in the embodiment illustrated by Table 4 below, mapping is performed for the "broadcast" mode (top two lines of the table), and another separate mapping for the "connection" mode (lower two lines of the table).

[0063] [Tables4] 1 2 3 4 5 S 7 8 9 10 11 1 1 1 0 0 0 1 1 0 1 1 2 3 4 5 6 7 8 9 10 11 12 1 1 0 û 0 1 1 1 0 0 1 1

[0064] In this embodiment, if it is observed that one of the two maps changes (for example following a modification of the mass distribution inside the vehicle), the other map can be redone.

[0065] Preferably, the mapping of the "connection" mode will only be redone if the mapping of the "broadcast" mode changes, because the establishment of the latter consumes significantly less electrical energy.

[0066] According to a possible variant, interesting in particular in the "connection" mode, especially in order to avoid storage and calculation on the wheel unit side), it can also be imagined that the mapping is done on the external electronic unit side thanks to the angular position information (the section index) which would be sent by the wheel unit.

[0067] In this variant, the mapping is done on the side of the external electronic unit which defines the inter-frame of the connection with the wheel unit.

[0068] In "broadcast" mode, the external electronic unit could send the mapping back to the wheel unit after the mapping step (so that it can be autonomous for the rest).

[0069] Naturally, the invention is described above by way of example. It is understood that a person skilled in the art is able to carry out different embodiments of the invention without departing from the scope of the invention.

Claims

Demands

1. A method for managing messages transmitted by radio waves from a wheel unit (11) to an external electronic unit, wherein: - the wheel unit (11) emits a signal at regular angular intervals of the wheel and assigns a sequence number to each of these intervals; - the external electronic unit detects whether this signal is received or not; - the external electronic unit sends the wheel unit information representative of this detection, or stores this information; - the wheel unit (11) or the external electronic unit deduces from this the angular intervals—designated as "clear zones"—in which the signal can be transmitted without alteration or with slight alteration, and those—designated as "shadow zones"—in which it risks being altered; - the wheel unit (11) or the external electronic unit extracts a sequence of indices of angular intervals of clear zones.- The wheel unit (11) or the external electronic unit calculates the common difference (r) of the arithmetic sequence that has the most terms in said sequence, or whose terms correspond to angular intervals allowing optimization of the transmission power of said signal from the wheel unit to the external electronic unit, - the wheel unit (11) emits messages periodically, the duration of the period being equal to the travel time of the wheel unit in each of said intervals, multiplied by said common difference (r).

2. A method according to claim 1, wherein the wheel unit (11) or the external electronic unit calculates said period using the formula: p - r • - ^Rlaou ' p is the period of emission of successive messages by the wheel unit ' r is the common difference of the arithmetic sequence with the most terms in the sequence of indices of the light areas, for a given number of message emissions' n is the total number of angular intervals R is the radius of the circular trajectory of the wheel unit, eta is the radial acceleration of the wheel unit.

3. A method according to claim 1, wherein the external electronic unit evaluates the reception power of said signal, and sends to the wheel unit information representative of this power.

4. Method according to claim 3, wherein the reason (r) is chosen which allows obtaining the best score of powers transmitted by the wheel unit to the external electronic unit.

5. A method according to any one of claims 1 to 4 wherein, when the wheel unit (11) emits a signaling message, it uses a prime number of regular angular intervals.

6. A method according to any one of the preceding claims wherein, when the wheel unit (11) establishes and maintains a connection with the external electronic unit, it uses a number of regular angular intervals that is not prime.

7. A method according to any one of the preceding claims in which the wheel unit (11) uses common angular intervals for the emission of signaling messages and the emission of connection messages.

8. A method according to any one of claims 1 to 7 wherein the wheel unit (11) uses distinct angular intervals for the emission of signaling messages and the emission of connection messages.

9. A method according to any one of the preceding claims in which the wheel unit (11) adapts the power of said signal according to the ratio between the number of clear areas and the number of shadow areas.

10. A method according to any one of the preceding claims wherein the wheel unit (11) resets the method if too many messages are corrupted or lost.

11. Wheel unit (11) comprising various sensors, a microcontroller, a memory, a battery and means of communication with the outside by radio waves, the microcontroller being duly programmed to implement the method according to any one of the preceding claims.

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