Communication method for pressure monitoring system
Through the communication method of automatically adjusting the radio frequency transmission power in the tire pressure monitoring system, the problem of excessive energy consumption in low-power communication mode is solved, the battery life is extended, and radio frequency power optimization data is provided.
Patent Information
- Application Number
- CN202410971715.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-07-20
- Filing Date
- 2024-07-19
- Publication Date
- 2025-01-21
AI Technical Summary
The existing tire pressure monitoring system (TPMS) has problems with excessive energy consumption in low-power communication mode, resulting in a shorter battery life.
A communication method is proposed to optimize the RF transmission power in "broadcast" mode by automatically adjusting the RF transmission power of the wheel unit, thereby determining the minimum RF power and limiting power consumption.
It effectively extends the service life of the wheel unit battery and provides RF power optimization data under different operating conditions for the optimization of future RF architecture.
Smart Images
Figure CN119329226A_ABST
Abstract
Description
[Technical field]
[0001] The invention relates to a communication method and in particular to a pressure monitoring system intended to measure the pressure in a motor vehicle tyre. [Background Technology]
[0002] Motor vehicle safety regulations require manufacturers to provide devices for monitoring tire pressure.
[0003] For this purpose, many pressure monitoring systems have been developed and put on the market in recent years.
[0004] As is well known, these pressure monitoring systems (usually indicated as "TPMS" ("Tire Pressure Monitoring System")) generally include: at least one wheel unit (including at least one pressure sensor), which is arranged inside a cavity defined by the tire and the rim of the vehicle's wheel; and a remote computing device, which communicates with the wheel unit via radio frequency, and these computing devices are generally located in an electronic computer of the vehicle's on-board electronic control unit (usually indicated as "ECU").
[0005] The wheel unit may be fixed inside the tread of the tire, or on an inflation valve of the tire mounted inside an orifice formed on the rim.
[0006] The wheel unit is usually powered by a non-rechargeable battery, which may have a service life of, for example, ten years.
[0007] The wheel unit and the ECU communicate via a radio frequency communication network. The wheel unit comprises a first transceiver device, and the ECU comprises a second transceiver device.
[0008] Radio frequency frames (commonly referred to as "RF frames") are transmitted by the wheel unit and received by the ECU in order to transmit pressure parameters relating in particular to the wheel.
[0009] RF communication Bluetooth Low Energy (commonly denoted "BLE") mode implementation enables short-range, two-way data exchange using UHF (ultra-high frequency) radio waves in the 2.4 GHz band.
[0010] Compared to "regular" The advantage of low power consumption is that it allows very little energy to be consumed when sending small amounts of data.
[0011] Can be used in "broadcast" mode Low power consumption, in this mode the wheel unit transmits periodic signals. The ECU analyses its environment by performing scans (called "scan requests") in very short periods of time to check whether these signals are emitted by the wheel unit. In other words, the wheel unit transmits an RF signal. The ECU confirms orderly reception or confirmation of the RF signal by returning an RF frame to the wheel unit. In practice, a communication search is performed between the wheel unit and the ECU.
[0012] Can be used in "Connect" mode Low power consumption, in this mode, the communication between the wheel unit and the ECU is correctly established after the "broadcast" mode. This connection mode can use RF frames to transmit pressure data.
[0013] This "connected mode" consumes a lot of energy. There are so-called "acknowledgement" mechanisms that are optimized based on the feedback loop of the receiver. Energy consumption of the wheel unit during low-power communication.
[0014] However, this type of mechanism does not exist for the "broadcast" mode, but in order to extend the battery life, it is necessary to reduce or optimize the energy consumption of the wheel unit regardless of which mode is used. [Summary of the invention]
[0015] The present invention proposes a method for A communication method for a low-power monitoring system solves this problem by optimizing the radio frequency transmission power of the wheel unit when the wheel unit is communicating in "broadcast" mode, thereby limiting its power consumption.
[0016] The invention relates to a communication method for a monitoring system comprising a wheel unit capable of performing measurements in a vehicle and an electronic control unit remote from the wheel unit. The wheel unit comprises a first radio frequency transceiver device intended to communicate via The low power communication communicates with a second radio frequency transceiver device provided on the electronic control unit to transmit the measurement results to the electronic control unit and establish a two-way communication between the wheel unit and the electronic control unit. The wheel unit can operate in a "broadcast" communication mode in which the wheel unit transmits a periodic signal of short duration to try to connect to the electronic control unit. The electronic control unit can confirm the periodic signal by transmitting a radio frequency signal frame to the wheel unit.
[0017] According to the invention, the method comprises the following steps: automatically adjusting the radio frequency transmission power of the wheel unit when the wheel unit is in a "broadcast" mode, during which the wheel unit transmits a signal with a variable radio frequency power in order to determine a minimum radio frequency power, starting from which the electronic control unit is able to confirm at least one radio frequency signal by transmitting a radio frequency signal frame to the wheel unit.
[0018] Therefore, the present invention proposes a method for A communication method for a low-power monitoring system can optimize the radio frequency transmission power of a wheel unit when the wheel unit is communicating in a "broadcast" mode, thereby limiting its power consumption and extending the service life of the battery (or battery cell).
[0019] The RF transmission power of the wheel unit is dynamically adjusted according to the receiving environment.
[0020] The radio frequency power data delivered by the wheel unit and obtained after each power optimization sequence may be periodically retrieved for processing in a set of networked servers (the "cloud") via an electronic control unit.
[0021] This information is very useful as it provides details on the RF power actually used and optimized to perform communications in a vehicle over the entire life cycle of the product and in all real operating situations (vehicle type, wheel type, weather scenarios, urban scenarios, highway, rural, etc.).
[0022] These data can be used in the future Optimize RF architecture in low-frequency wheel unit project.
[0023] In practice, starting from the actually useful power, it is possible to adjust the type of battery, the size of the antenna and indirectly the size of the housing that houses these elements.
[0024] As a variant, a maximum RF power threshold is defined. The wheel unit starts by transmitting RF signals with the maximum RF power threshold and then transmits RF signals while reducing the power of these RF signals until the electronic control unit is no longer able to decode the RF signals. The power of the last confirmed RF signal is limited by the wheel unit to the minimum RF power.
[0025] As a variant, a minimum RF power threshold is defined. The wheel unit starts by transmitting a RF signal having the minimum RF power threshold and then transmits RF signals while increasing the power of these RF signals until the electronic control unit confirms the first signal. The power of the first confirmed RF signal is limited by the wheel unit to the minimum RF power.
[0026] These automatic calibration modes have the advantage of being easy and fast to implement, thus limiting energy consumption. According to both variants, only the wheel unit performs actions to determine the minimum radio frequency power.
[0027] As a variant, a plurality of series of radio frequency signal transmissions are performed, including a first series with a radio frequency signal having a predefined maximum radio frequency power. Each subsequent series of transmissions is performed with a radio frequency signal having a reduced power level. For each series of transmissions, a plurality of radio frequency signals of the same power are transmitted at equidistant angular positions on the wheel for each rotation of the wheel. The wheel unit determines the success reception rate by statistical calculation and for a plurality of rotations of the wheel. A minimum power level is determined based on a predefined acceptable success reception rate.
[0028] As a variant, a plurality of series of radio frequency signal transmissions are performed, including a first series with a radio frequency signal having a predefined minimum radio frequency power. Each subsequent series of transmissions is performed with a radio frequency signal having an increasing power level. For each series of transmissions, a plurality of radio frequency signals of the same power are transmitted at equidistant angular positions on the wheel for each rotation of the wheel. The wheel unit determines the success reception rate by statistical calculation and for a plurality of rotations of the wheel. The minimum power level is determined based on the predefined acceptable success reception rate.
[0029] These variants may take into account non-reception areas that block the radio frequency signal and to which the electronic control unit cannot respond. For example, these non-reception areas are caused by elements of the vehicle, such as shock absorbers or body elements.
[0030] As a variant, the method comprises a calculation based on a dichotomy. min and the maximum power threshold S max According to the relationship P av =(S min +S max ) / 2 defines the average power level. The wheel unit is operated at an average power level P av The signal is transmitted and the reception of the signal by the electronic control unit is checked. If the electronic control unit receives the signal at an average power level P av The average power level of the transmitted signal is P av is considered as the new maximum power threshold S max If the ECU does not accept the average power level P av The average power level of the transmitted signal is regarded as the new minimum power threshold S min When S min and S max When they are equal, the minimum RF power is determined.
[0031] This variant allows for bisection-based convergence, thus improving the accuracy of the minimum power level.
[0032] As a variant, a maximum RF power threshold is defined. The wheel unit starts by transmitting RF signals with the maximum RF power threshold and then transmits RF signals while reducing the power of these RF signals until the electronic control unit is no longer able to decode the signals. The electronic control unit deactivates its ability to acknowledge RF signals in order to signal to the wheel unit that the power of the last received RF signal should be limited to the minimum RF power.
[0033] As a variant, a minimum RF power threshold is defined. The wheel unit starts by transmitting RF signals having the minimum RF power threshold and then transmits RF signals while increasing the power of these RF signals until the electronic control unit acknowledges the signal. The electronic control unit activates its ability to receive signals in order to signal to the wheel unit that the power of the RF signal acknowledged first should be limited to the minimum RF power.
[0034] These last two variants can increase the reliability of the method.
[0035] The wheel unit is mounted on the wheel of the vehicle and is designed to measure the pressure inside the tire.
[0036] The invention also relates to a vehicle comprising at least one monitoring system implementing a communication method as defined above. [Drawings]
[0037] [ Figure 1 ] Figure 1 is a schematic plan view of a motor vehicle comprising a TPMS monitoring system capable of implementing a communication method according to the invention. [Specific implementation method]
[0038] Figure 1 A motor vehicle 10 is shown, comprising an electronic control unit 12 and four wheels 14a, 14b, 14c, 14d, each wheel being equipped with a wheel unit 16a, 16b, 16c, 16d, respectively.
[0039] In order to avoid a lengthy description, only one wheel unit 16a is described below, wherein the four wheel units 16a, 16b, 16c, 16d have similar designs and operations.
[0040] An electronic control unit 12 (referred to as “ECU”) of the motor vehicle 10 includes an electronic computer and a memory (neither shown).
[0041] The electronic control unit 12 also includes a radio frequency receiver 20 .
[0042] The wheel unit 16 a includes a housing that encloses a computer 22 , a battery 24 , and a memory 26 .
[0043] Furthermore, the wheel unit 16a comprises a set of sensors 30 dedicated to measuring operating parameters of the wheel unit 16a.
[0044] This set of sensors 30 comprises a first temperature sensor capable of measuring a temperature parameter T, a second sensor of the accelerometer type capable of measuring the accelerations to which the wheel unit 16a is subjected, and a third pressure sensor capable of measuring the inflation pressure of the tire of the associated wheel 14a.
[0045] The measurements taken by this set of sensors 30 can be transmitted to the electronic control unit 12 of the motor vehicle 10 via messages transmitted by the transmitter 28 of the associated wheel unit 16 a .
[0046] The present invention relates to a communication method for a TPMS (Tire Pressure Monitoring System) pressure monitoring system, which pressure monitoring system generally includes: at least one wheel unit 16a, which is arranged inside a cavity defined by the tire and rim of a wheel 14a of a vehicle; and a remote computing device, which performs unidirectional or bidirectional radio frequency communication with the wheel unit 16a. These computing devices are generally located in an on-board electronic control unit 12 (generally referred to as "ECU") of the vehicle, and the electronic control unit 12 and the wheel unit 16a are appropriately programmed to implement the method according to the present invention.
[0047] The wheel unit 16 a may be secured inside the tread of a tire, or on an inflation valve of the tire mounted inside an aperture formed on the rim of the wheel 14 a of the vehicle 10 .
[0048] The wheel unit 16a of the tire is typically powered by a non-rechargeable battery 24 which may have a useful life of, for example, ten years.
[0049] The wheel unit 16a and the ECU 12 communicate via a radio frequency communication network. The wheel unit 16a comprises a first radio frequency transceiver device 28 and the ECU 12 comprises a second radio frequency transceiver device 20.
[0050] Radio frequency frames (commonly referred to as "RF frames") are transmitted by the wheel unit 16a and received by the ECU 12 to transmit pressure parameters associated with the wheel 14a.
[0051] RF communication Bluetooth Low Energy (commonly denoted "BLE") mode implementation enables short-range, two-way data exchange using UHF radio waves in the 2.4 GHz band.
[0052] The wheel unit 16a is capable of operating in two communication modes, namely a "broadcast" mode and a "connect" mode. In this "broadcast" mode, a short-duration periodic signal is transmitted by the wheel unit 16a to try to connect to the electronic control unit 12, and in this "connect" mode, a stable connection is established between the wheel unit 16a and the electronic control unit 12 in order to transmit pressure measurement results.
[0053] The "broadcast" mode is first used to try to establish an RF connection with the electronic control unit 12, and changes to the "connect" mode, which can exchange pressure information between the wheel unit 16a and the electronic control unit 12 via RF frames. There is a feedback loop in the "connect" mode, which can automatically adjust the power of the transmitted signal. This feedback loop is composed of Low power consumption BLE 5.0 standard is provided.
[0054] For the present invention, the "broadcast" communication mode is used. The "connect" mode is not used.
[0055] In the "broadcast" communication mode, a two-way communication is established between the wheel unit 16a and the electronic control unit 12. The electronic control unit 12 confirms the periodic signal by transmitting a radio frequency signal frame to the wheel unit 16a. In other words, the electronic control unit 12 confirms the orderly reception of the received signal by returning a specific radio frequency frame to the wheel unit 16a. This operation of transmitting a radio frequency signal frame is generally represented by the term "scan request".
[0056] The transmission power of the wheel unit 16 a is fixed and high to ensure that the electronic control unit 12 successfully receives the radio frequency.
[0057] When the electronic control unit 12 of the vehicle 10 is activated, the electronic control unit 12 of the monitoring system analyzes or scans its environment to try to connect to the wheel unit 16a. When the electronic control unit 12 picks up a signal transmitted by the wheel unit 16a, the electronic control unit 12 accepts or acknowledges the signal and signals the wheel unit 16a with the signal.
[0058] The vehicle 10 may be moving or stationary.
[0059] According to the present invention, the communication method for the pressure monitoring system includes the following steps: when the wheel unit 16a is in the "broadcast" mode, the RF transmission power of the wheel unit 16a is automatically adjusted. During the "broadcast" mode, the wheel unit 16a transmits a signal with variable RF power so as to determine the minimum RF power. Starting from the minimum RF power, the electronic control unit 12 is able to confirm at least one signal by transmitting a RF signal frame to the wheel unit 16a.
[0060] According to a variant, the wheel unit 16a operates in an automatic calibration mode in which it checks whether the electronic control unit 12 is able to read the messages transmitted by the wheel unit 16a. The wheel unit 16a operates autonomously with a minimum involvement of the electronic control unit 12, which merely acknowledges or does not acknowledge the messages transmitted by the wheel unit 16a.
[0061] According to a variant, a maximum RF power threshold is defined. The wheel unit 16a starts by transmitting a RF signal having this maximum RF power threshold and then transmits other RF signals while gradually reducing the power of these RF signals until the electronic control unit 12 is no longer able to decode the signal, which indicates that the power of the signal is insufficient to establish RF communication. The power of the last confirmed RF signal is then limited by the wheel unit 16a to the minimum RF power.
[0062] According to a variant, the step of determining the maximum radiofrequency power threshold is preceded by a check whether the known electronic control unit 12 responds to a signal transmitted at a defined nominal power.
[0063] For example, the maximum RF power threshold is +4dBm.
[0064] The wheel unit 16a operating in the "broadcast" mode starts by transmitting a radio frequency signal with a radio frequency power of +4 dBm. If the electronic control unit 12 acknowledges the signal, the power level of the subsequent radio frequency signal is reduced and is therefore less than +4 dBm.
[0065] The process stops when the transmission signal is no longer acknowledged by the electronic control unit 12. The wheel unit 16a then regards the previous signal as the signal with the minimum radio frequency power and stores the minimum radio frequency power value.
[0066] According to another variant, a minimum radio frequency power threshold is defined.
[0067] During the step of automatically adjusting the power, the wheel unit 16 a starts by transmitting radio frequency signals having a minimum radio frequency power threshold, and then transmits radio frequency signals while increasing the power of these radio frequency signals until the electronic control unit 12 acknowledges the first signal.
[0068] The power of the first confirmed RF signal is limited to the minimum RF power by the wheel unit 16a.
[0069] According to a variant, the step of determining the minimum radiofrequency power threshold is preceded by a check whether the known electronic control unit responds to a signal transmitted at a defined nominal power.
[0070] For example, the minimum RF power threshold is -4dBm.
[0071] The wheel unit 16a operating in the "broadcast" mode starts by transmitting a radio frequency signal with a radio frequency power of -4 dBm. If the electronic control unit 12 does not acknowledge the signal, the power level of the subsequent radio frequency signal is increased and is therefore greater than -4 dBm.
[0072] The process stops when the electronic control unit 12 confirms the first transmission signal. The wheel unit 16a then regards the first signal as a signal with minimum radio frequency power and stores the minimum radio frequency power value.
[0073] According to another variant, a plurality of series of transmissions are performed, including a first series with a radio frequency signal having a predefined maximum radio frequency power, for example +4 dBm.
[0074] Each subsequent series of transmissions is performed with a radio frequency signal having a gradually decreasing power level. For each series of transmissions, a plurality of radio frequency signals of equal power are transmitted at equidistant angles on the wheel 14a for each rotation of the wheel.
[0075] For example, during one rotation of the wheel 14a, three RF signals having the same content may be transmitted at the same power level every 120°.
[0076] The wheel unit 16a determines the successful reception rate by statistical calculation and for a number of rotations of the wheel 14a. The power level of the signal is then reduced for the next series of measurements.
[0077] The minimum power level is determined based on a predefined acceptable successful reception rate.
[0078] For example, if the electronic control unit 12 receives most of the signals when the maximum RF power is +4 dBm, the success rate is high and higher than the predefined acceptable successful reception rate.
[0079] A new series of RF signal transmissions are then performed at an RF power level less than +4dBm.
[0080] In the following series, the RF power is reduced until the success rate is no longer acceptable. The last series of RF power that results in an acceptable success reception rate is defined as the minimum RF power.
[0081] In practice, if the last series of measured signals results in a success rate below a predefined acceptable successful reception rate, and the second to last series of measured signals results in a success rate above a predefined acceptable successful reception rate, this series of signals is considered to define the minimum power level.
[0082] This variant makes it possible to take into account non-reception areas (also called "black spots") that block the radio frequency signal and to which the electronic control unit 12 cannot respond. These non-reception areas are caused, for example, by elements of the vehicle, such as shock absorbers or body elements.
[0083] As a variation, multiple series of transmissions are performed in a similar manner, including a first series with an RF signal having a predefined minimum RF power. Each subsequent series of transmissions is performed with RF signals with gradually increasing power levels. For each transmission series, multiple RF signals of the same power are transmitted at equidistant angles on the wheel 14a for each rotation of the wheel 14a. For example, during one rotation of the wheel 14a, three RF signals with the same content can be transmitted at the same power level every 120°. The wheel unit 16a determines the successful reception rate by statistical calculation and for multiple rotations of the wheel 14a. The wheel unit 16a determines the successful reception rate by statistical calculation and for multiple rotations of the wheel 14a. The minimum power level is determined based on the predefined acceptable successful reception rate.
[0084] According to another variant, the method comprises a calculation based on a bisection method. Defining a minimum power threshold S min and the maximum power threshold S max . Also according to the relationship P av =(S min +S max ) / 2 limits the average power level.
[0085] The wheel unit 16a operates at an average power level P av A signal is emitted and it is checked whether it is acknowledged by the electronic control unit 12 .
[0086] If the electronic control unit 12 determines that the average power level P av The average power level of the transmitted signal is P av is considered as the new maximum power threshold S max .
[0087] Otherwise, if the electronic control unit 12 does not confirm that the average power level P av The average power level of the transmitted signal is regarded as the new minimum power threshold S min .
[0088] As long as S min and S max If S is different, the algorithm is executed. min and S max When they are equal, the minimum RF power is determined. Therefore, the last maximum power threshold S max Considered as minimum RF power.
[0089] The above described variant is applicable when the wheel unit 16a is operated in the auto-calibration (or automatic) mode, the electronic control unit 12 merely confirms or de-confirms the signal.
[0090] According to another variant, the electronic control unit 12 takes the lead in defining the minimum radio frequency power.
[0091] The wheel unit 16a transmits the radio frequency signal at maximum power and reduces the power until the electronic control unit 12 deems the received field level to be within acceptable lower limits.
[0092] In other words, a maximum RF power threshold is defined.The wheel unit 16a starts by transmitting RF signals with the maximum RF power threshold and then transmits RF signals while reducing the power of these RF signals until the electronic control unit 12 can no longer decode or acknowledge the signals.
[0093] The power of the last signal acknowledged by the electronic control unit 12 is considered the minimum RF power. The electronic control unit 12 deactivates its ability to acknowledge signals in order to signal to the wheel unit 16a that the power of the last received RF signal should be limited to the minimum RF power.
[0094] Thereafter, the electronic control unit 12 ignores the received radio frequency frame. The wheel unit 16a knows that the electronic control unit 12 has not received the signal and therefore limits the minimum acceptable power level to the previous functional value.
[0095] According to another variant, the wheel unit 16 a does not start from the upper power limit, but starts by emitting a signal within the lower power limit until an acknowledgement from the electronic control unit 12 is detected.
[0096] In practice, a minimum RF power threshold is defined. The wheel unit 16a starts by transmitting the RF signal with the minimum RF power threshold and then transmits the following RF signals while increasing the power of these RF signals each time until the electronic control unit 12 acknowledges the signal.
[0097] Then, the electronic control unit 12 activates its capability of confirming the signal in order to signal the wheel unit 16a that the power of the first confirmed radio frequency signal should be limited to the minimum radio frequency power.
[0098] As a variant, a waiting time is provided after the electronic control unit 12 has failed to confirm the signal.
[0099] By way of example, the above-described variations are given for the case of wheel unit 16a.
[0100] As a variant, the radio frequency power data delivered by the wheel unit 16 a and obtained after each power optimization sequence may be retrieved periodically for processing in a set of networked servers (“the cloud”) via the electronic control unit 12 .
[0101] This information is very useful as it provides details on the RF power actually used and optimized to perform communications in a vehicle over the entire life cycle of the product and in all real operating situations (vehicle type, wheel type, weather scenarios, urban scenarios, highway, rural, etc.).
[0102] These data can be used in the future Optimize RF architecture in low-frequency wheel unit project.
[0103] In practice, starting from the actually useful power, it is possible to adjust the type of battery, the size of the antenna and indirectly the size of the housing that houses these elements.
Claims
1. A communication method for a monitoring system, the monitoring system comprising: a wheel unit (16a, 16b, 16c, 16d) capable of performing measurements in a vehicle (10); and an electronic control unit (12) remote from the wheel unit (16a, 16b, 16c, 16d), the wheel unit (16a, 16b, 16c, 16d) comprising a first radio frequency transceiver device (28) intended to communicate with the wheel unit via The electronic control unit (12) is configured to communicate with a second radio frequency transceiver device (20) provided in the electronic control unit (12) so as to enable short-range bidirectional data exchange using low-power ultra-high frequency radio waves so as to transmit measurement results to the electronic control unit (12) and to establish bidirectional communication between the wheel unit (16a, 16b, 16c, 16d) and the electronic control unit (12). The wheel unit (16a, 16b, 16c, 16d) is capable of operating in a "broadcast" communication mode in which the wheel unit transmits a short-duration periodic signal to attempt to connect to the electronic control unit (12). The electronic control unit (12) is capable of transmitting measurement results to the wheel unit (16a, 16b, 16c, 16d) and the electronic control unit (12). , 16b, 16c, 16d) transmits radio frequency signal frames to confirm these periodic signals, characterized in that the communication method includes the following steps: when the wheel unit (16a, 16b, 16c, 16d) is in a "broadcast" mode, the radio frequency transmission power of the wheel unit (16a, 16b, 16c, 16d) is automatically adjusted, during the "broadcast" mode, the wheel unit (16a, 16b, 16c, 16d) transmits a signal with variable radio frequency power to determine a minimum radio frequency power, starting from the minimum radio frequency power, the electronic control unit (12) is able to confirm at least one signal by transmitting a radio frequency signal frame to the wheel unit (16a, 16b, 16c, 16d).
2. The method according to claim 1, characterized in that A maximum radio frequency power threshold is defined, the wheel unit (16a, 16b, 16c, 16d) starts by transmitting a radio frequency signal having the maximum radio frequency power threshold, and then transmits radio frequency signals while reducing the power of these radio frequency signals until the electronic control unit (12) is no longer able to decode the radio frequency signal, and the power of the last confirmed radio frequency signal is defined by the wheel unit (16a, 16b, 16c, 16d) as the minimum radio frequency power.
3. The method according to claim 1, characterized in that A minimum radio frequency power threshold is defined, the wheel unit (16a, 16b, 16c, 16d) starts by transmitting a radio frequency signal having the minimum radio frequency power threshold, and then transmits radio frequency signals while increasing the power of these radio frequency signals until the electronic control unit (12) confirms a first radio frequency signal, the power of the first confirmed radio frequency signal being defined by the wheel unit (16a, 16b, 16c, 16d) as the minimum radio frequency power.
4. The method according to any one of claims 1 and 2, characterized in that A plurality of series of radio frequency signal transmissions are performed, including a first series of radio frequency signals having a predefined maximum radio frequency power, and each subsequent series of transmissions is performed using radio frequency signals with a reduced power level, wherein for each series of transmissions, a plurality of radio frequency signals of the same power are transmitted at equidistant angular positions on the wheel (14a, 14b, 14c, 14d) for each rotation of the wheel (14a, 14b, 14c, 14d), and the wheel unit (16a, 16b, 16c, 16d) determines a successful reception rate by statistical calculation and for multiple rotations of the wheel (14a, 14b, 14c, 14d), and determines the minimum power level based on a predefined acceptable successful reception rate.
5. The method according to any one of claims 1 and 3, characterized in that A plurality of series of radio frequency signal transmissions are performed, including a first series of radio frequency signals having a predefined minimum radio frequency power, and each subsequent series of transmissions is performed with radio frequency signals having increasing power levels, wherein for each series of transmissions, a plurality of radio frequency signals having the same power are transmitted at equidistant angular positions on the wheel (14a, 14b, 14c, 14d) for each rotation of the wheel (14a, 14b, 14c, 14d), and the wheel unit (16a, 16b, 16c, 16d) determines a successful reception rate by statistical calculation and for multiple rotations of the wheel (14a, 14b, 14c, 14d), and determines the minimum power level based on a predefined acceptable successful reception rate.
6. The method according to claim 1, characterized in that The method includes a calculation based on a dichotomy method, defining a minimum power threshold S min and the maximum power threshold S max , according to the relationship P av =(S min +S max ) / 2 limits the average power level P av The wheel unit (16a, 16b, 16c, 16d) transmits a signal at the average power level and checks the acceptance of the signal by the electronic control unit (12). If the electronic control unit (12) accepts the signal at the average power level P av The signal transmitted, the average power level P av is considered as the new maximum power threshold S max If the electronic control unit (12) does not accept the average power level P av The signal transmitted, the average power level is regarded as the new minimum power threshold S min , when S min and S max When they are equal, the minimum RF power is determined.
7. The method according to claim 1, characterized in that A maximum RF power threshold is defined, the wheel unit (16a, 16b, 16c, 16d) starts by transmitting RF signals having the maximum RF power threshold, and then transmits RF signals while reducing the power of these RF signals until the electronic control unit (12) is no longer able to decode the signal, the electronic control unit (12) deactivates its ability to confirm the signal in order to signal the wheel unit (16a, 16b, 16c, 16d) that the power of the last received RF signal should be limited to the minimum RF power.
8. The method according to claim 1, characterized in that A minimum radio frequency power threshold is defined, the wheel unit (16a, 16b, 16c, 16d) starts by transmitting a radio frequency signal having the minimum radio frequency power threshold, and then transmits radio frequency signals while increasing the power of these radio frequency signals until the electronic control unit (12) confirms the radio frequency signal, and the electronic control unit (12) activates its signal confirmation capability to signal the wheel unit (16a, 16b, 16c, 16d) that the power of the radio frequency signal first confirmed should be limited to the minimum radio frequency power.
9. The method according to any one of claims 1 to 7, characterized in that The wheel unit (16a, 16b, 16c, 16d) is mounted on a wheel (14a) of a vehicle (10) and is intended to monitor the pressure inside the tire.
10. A vehicle (10), characterized in that: The vehicle comprises at least one monitoring system implementing a communication method as defined in any one of claims 1 to 9.