Method for detecting vehicle movement

Abstract

The invention relates to a method for detecting a rotational movement of a body around an axis of rotation relative to a fixed structure, the body comprising a sensor intended to perform measurements on the body and having a first radio frequency transmitter / receiver intended to communicate with a second radio frequency transmitter / receiver provided on an electronic computer mounted on the fixed structure by means of a low energy Bluetooth® communication to transmit the measurements to the electronic computer, the sensor being capable of emitting (1) radio frequency signals and the electronic computer being capable of acknowledging receipt (2) of the radio frequency signals by transmitting a response signal to the sensor.The method includes a step (6) of detecting the rotational movement of the body by the sensor using the response signals transmitted by the electronic computer and a step (7) of adapting the periodicity of the radio frequency signals emitted by the sensor according to whether the body is rotating or not. Figure for the abstract: Figure 1.

Description

Title of the invention: Method for detecting the movement of a vehicle technical field

[0001] The present invention relates to a method for detecting the movement of a motor vehicle by means of a tire pressure monitoring system of said vehicle. Previous technique

[0002] Automotive safety legislation requires manufacturers to provide means for monitoring vehicle tire pressure.

[0003] To this end, several pressure monitoring systems have been developed and put on the market in recent years.

[0004] As is known in itself, these pressure monitoring systems, commonly referred to as "TPMS" (from the English "Tire Pressure Monitoring System"), typically include at least one wheel unit (including at least one pressure sensor) disposed inside the chamber defined by the tire and the rim of the wheel of a vehicle, and remote computing means communicating with this wheel unit by unidirectional or bidirectional radio frequencies, these computing means being generally located in the electronic computer of an on-board electronic central unit of the vehicle (commonly referred to as "ECU" for "Electronic Control Unit" in English).

[0005] Communication between the wheel unit and the ECU is carried out via a radio frequency communication network. The wheel unit includes a transmitter and the ECU includes a receiver.

[0006] A radio frequency frame, generally called an "RF frame", is emitted by the wheel unit and received by the ECU in order to transmit wheel pressure parameters.

[0007] Radio frequency communication is carried out using Bluetooth® Low Energy, (commonly referred to as "BLE" for "Bluetooth Low Energy" in English) allowing bidirectional exchange of data over short distances using UHF radio waves on the 2.4 GHz frequency band.

[0008] The advantage of Bluetooth® Low Energy compared to "classic" Bluetooth® is that it allows small amounts of data to be sent while consuming very little energy.

[0009] The wheel unit can be fixed inside the tread of the tire, or on the inflation valve of this tire, which is mounted inside an opening formed on the rim.

[0010] The tire wheel unit is typically powered by a non-rechargeable battery which can have a lifespan of ten years, for example.

[0011] It is known to use an accelerometer, a shock sensor, or a magnetic field sensor in pressure monitoring systems to detect vehicle movement. This movement detection optimizes the wheel unit's power consumption by limiting the number of radio frequency frame transmissions when the vehicle is stationary (in "parking" mode). This reduces the wheel unit's energy consumption, thereby extending battery life.

[0012] However, the addition of an accelerometer, a shock sensor or a terrestrial magnetic field sensor increases the complexity, weight and price of the wheel units of the pressure monitoring system.

[0013] This also results in more product references to manage. Description of the invention

[0014] The invention solves this problem by proposing a method for detecting the rotation of a body, in particular a wheel of a motor vehicle, making it possible to reduce the complexity and weight of the wheel units of the pressure monitoring system, by reducing the number of its components.

[0015] The invention relates to a method for detecting the rotational movement of a body around an axis of rotation relative to a fixed structure. The body comprises a sensor for taking measurements and includes a first radio frequency transmitter / receiver for communicating with a second radio frequency transmitter / receiver provided on an electronic computer mounted on the fixed structure, using low-energy Bluetooth® communication to transmit the measurements to the electronic computer. The sensor is capable of emitting radio frequency signals periodically, and the electronic computer is capable of acknowledging receipt of the radio frequency signals by transmitting a radio frequency response signal to the sensor.

[0016] According to the invention, the detection method comprises a step of detecting the rotational movement of the body by the sensor by means of the response signals transmitted by the electronic computer and a step of adapting the periodicity of the radio frequency signals emitted by the sensor according to the rotation or non-rotation of the body.

[0017] The invention thus provides a method for detecting the rotation of a body, in particular a wheel of a motor vehicle, making it possible to reduce the complexity and weight of the pressure monitoring system, by reducing the number of its components.

[0018] There are also fewer product references to manage.

[0019] The invention also makes it possible to reduce the energy consumption of the sensor and to increase battery life.

[0020] Alternatively, during the step of adapting the periodicity of the emitted signals, the sensor emits periodic radio frequency frames intended to be received by the electronic computer according to a first periodicity PI when the body is not rotating. The sensor emits periodic radio frequency frames according to a second periodicity P2 when the body is rotating, P2 being strictly greater than PI.

[0021] Alternatively, during the step of detecting the body's rotational movement, the sensor measures the intensity of the response signal emitted by the electronic computer. The body is considered to be rotating if a variation between two successive radio frequency response signals is detected; otherwise, the body is considered to be stationary.

[0022] Alternatively, the variation in intensity between two successive radio frequency response signals is considered significant if a detection threshold taking into account a margin of error is reached.

[0023] This allows a comparison to be made between two successive radio frequency response signals with a margin of error taking into account the accuracy of measurement, ambient noise, a vehicle parking next to it, the fluctuation between low energy Bluetooth channels, for example.

[0024] Alternatively, an average is taken over several measurements to filter the radio frequency signals.

[0025] This allows us to take into account that in "parking" mode, two successive radio frequency response signals may be different.

[0026] Alternatively, after detecting the rotation of the body, the sensor emits radio frequency frames with a second periodicity P2. The electronic control unit acknowledges receipt of the radio frequency frames with period P2 by transmitting a response signal to the sensor. The sensor measures the intensity of a succession of response signals emitted by the electronic control unit to determine a signal pattern. The rotation of the body is confirmed when the signal pattern is periodic. Otherwise, the wheel is considered stationary if the signal pattern is not periodic.

[0027] This makes the process more reliable and ensures that the body is rotating properly.

[0028] Alternatively, during the step of detecting the body's rotational movement, the sensor emits radio frequency frames, and the body's rotation is detected if the electronic computer acknowledges receipt of the radio frequency frames by transmitting a response signal to the sensor. The sensor emits radio frequency frames according to the second periodicity P2.

[0029] This variant provides a simpler method. Activation of the electronic calculator means that the body is rotating.

[0030] Alternatively, the step of detecting the rotational movement of the body is carried out with a sensor in "presence state" mode in which short periodic signals are transmitted by the sensor to allow a connection with the electronic control unit.

[0031] Alternatively, the detection method is a method for detecting the movement of a motor vehicle comprising a pressure monitoring system for measuring the pressure in a tire of one of the vehicle's wheels. The wheel includes a wheel unit capable of establishing low-energy Bluetooth® communication to transmit pressure measurements to an electronic control unit of the vehicle's central electronic unit.

[0032] The invention also relates to a motor vehicle implementing the detection method as defined above. Brief description of the drawings

[0033] [Fig. 1] The [Fig. 1] represents a diagram of a method for detecting the rotation of a vehicle wheel, according to a first embodiment of the invention;

[0034] [Fig.2] Fig.2 represents a diagram of a method for detecting rotation of a vehicle wheel, according to a second embodiment of the invention. Description of the implementation methods

[0035] The invention relates to a method for detecting a rotational movement of a body around an axis of rotation relative to a fixed structure, and more particularly of a vehicle wheel to determine whether the vehicle is moving or stopped ("parking mode").

[0036] The example below is given for a pressure monitoring system associated with a wheel of a vehicle but can also be applied to other monitoring or measurement systems associated with a rotating body which uses low energy Bluetooth® communication.

[0037] The vehicle includes a pressure monitoring system which is commonly referred to as "TPMS" (Tire Pressure Monitoring System), and which typically includes at least one wheel unit, comprising a pressure sensor, disposed inside the chamber defined by the tire and the rim of the vehicle wheel, and remote computing means communicating with this wheel unit by bidirectional radio frequencies, these computing means being generally located in the electronic computer of an on-board electronic central unit of the vehicle (commonly referred to as "ECU" for "Electronic Control Unit").

[0038] The wheel unit can be fixed inside the tread of the tire, or on the inflation valve of this tire, which is mounted inside an opening formed on the rim.

[0039] The tire wheel unit is typically powered by a non-re- battery rechargeable which can have a lifespan of ten years, for example.

[0040] Communication between the wheel unit and the electronic central unit is carried out via a radio frequency communication network. The wheel unit comprises a first radio frequency transmitter / receiver set and the electronic central unit comprises a second radio frequency transmitter / receiver set.

[0041] A radio frequency frame, generally called an "RF frame", is emitted by the wheel unit and received by the electronic central unit in order to transmit wheel pressure parameters.

[0042] Radio frequency communication is carried out using Bluetooth® Low Energy, (commonly referred to as "BLE" for Bluetooth® Low Energy in English) allowing bidirectional data exchange over short distances using UHF radio waves on the 2.4 GHz frequency band.

[0043] The wheel unit operates according to two communication modes, including a "presence state" mode in which short periodic signals are transmitted by the wheel unit to allow a connection with the electronic central unit, and a "connected" mode in which a stable connection is established between the wheel unit and the electronic central unit for the transmission of pressure measurements.

[0044] In "presence status" (or "advertising") communication mode, bidirectional communication is established between the wheel unit and the electronic control unit. The electronic control unit acknowledges the periodic signals by transmitting a frame of radio frequency signals to the wheel unit. In other words, the electronic control unit confirms successful reception of the received signal by returning a specific radio frequency frame to the wheel unit. This operation of transmitting radio frequency signal frames is commonly referred to as "scan-request".

[0045] The "presence state" mode is used first to try to establish a radio frequency connection with the electronic central unit and possibly switch to "connected" mode which allows pressure information to be exchanged by radio frequency frame between the wheel unit and the electronic central unit.

[0046] The "connected" mode is optional.

[0047] The transmission power of the wheel unit is fixed and high, to ensure a good radio frequency reception balance by the electronic central unit.

[0048] When the vehicle is started, the electronic control unit analyzes or scans its environment to search for a connection with the wheel unit. When the electronic control unit detects a signal transmitted by the wheel unit, it accepts (or acknowledges) this signal and notifies the wheel unit. More specifically, the wheel unit sends radio frequency frames.

[0049] According to the invention, the method for detecting the rotation of the vehicle wheel includes a step of detecting the rotational movement of the wheel by the wheel unit by means of radio frequency signals transmitted by the electronic central unit and received by the wheel unit and a step of adapting the periodicity of the radio frequency signals emitted by the wheel unit according to the movement of the wheel, i.e. the rotation or non-rotation of the wheel.

[0050] During the step of adapting the periodicity of the emitted signals, the wheel unit emits periodic radio frequency frames intended for reception by the electronic central unit according to a first periodicity PI when the wheel is not rotating. The wheel unit emits periodic radio frequency frames according to a second periodicity P2 when the wheel is rotating, P2 being strictly greater than PL. This saves energy when the vehicle is parked.

[0051] According to a first embodiment of the invention, during the step of detecting the rotational movement of the wheel, the wheel unit emits radio frequency frames and the central electronic unit acknowledges receipt (or acknowledges) of the radio frequency frames by transmitting a response signal to the wheel unit.

[0052] The wheel unit measures the intensity of the response signal emitted by the electronic central processing unit. The wheel on which the wheel unit is mounted is considered to be rotating if a change in intensity is detected between two successive radio frequency response signals; otherwise, the wheel is considered stationary. More precisely, it is the change in the signal strength indication (called "Received Signal Strength Indication" RSSI) that is analyzed by the wheel unit. The signal strength indication is available because it is required by the Bluetooth® Low Energy standard.

[0053] The wheel unit rotates, receives radio frequency response signals at different angles of the wheel, with a changing radio frequency link budget, which is not the case when the vehicle is in "parking" mode.

[0054] Thus, the wheel is considered stationary and the vehicle in "parking" mode if the variation between two successive radio frequency response signals is not significant, that is, if the signals have identical or nearly identical intensities, taking into account a margin of error. The wheel is considered to be rotating and the vehicle in motion if the variation between two successive response signals is significant. It is, in fact, the intensity of the electromagnetic field of the radio frequency signal received by the wheel unit that is measured. The wheel unit analyzes the level of radio frequency power it receives.

[0055] To deduce that the wheel is stationary, the comparison between two successive radio frequency response signals is carried out with a margin of error taking into account the accuracy of measurement, the surrounding noise, a vehicle parking next to it, the fluctuation between the low energy Bluetooth® channels, for example.

[0056] A detection threshold can be applied. A variation in intensity is then detected if this detection threshold is reached, in other words if the difference between two successive radio frequency response signals is sufficiently high, taking into account the previous parameters that may disturb and vary the radio frequency signal.

[0057] If the variation between two successive response signals is less than this detection threshold, the wheel is considered stationary.

[0058] Alternatively, since in "parking" mode two successive radio frequency response signals may be different, an average can be taken over several measurements over a determined period, i.e. over an identical wheel angle between each measurement, to allow the signal to be filtered.

[0059] According to the diagram in [Fig. 1] illustrating an example, the detection process includes a first step 1 during which the wheel unit emits radio frequency frames and a second step 2 during which the central electronic unit acknowledges receipt of the radio frequency frames by transmitting a response signal to the wheel unit, regardless of the communication mode ('presence state' mode or 'connected' mode).

[0060] The detection method includes a third step 3 during which the wheel unit measures the intensity or power of the response signal emitted by the electronic central unit.

[0061] According to a first result (referenced step 4), the wheel is considered stationary and the vehicle in "parking" mode (referenced step 5) if the variation between two successive response signals is not significant taking into account the margin of error.

[0062] According to a second result (referenced step 6), the wheel is considered to be rotating and the vehicle to be rolling if the variation between two successive response signals is significant by exceeding a detection threshold.

[0063] The detection method includes a fourth step 7 during which the wheel unit emits radio frequency frames according to the second periodicity P2, that is to say it increases the periodicity of the radio frequency frames.

[0064] The detection method includes a fifth step 8 during which the central electronic unit acknowledges receipt (acknowledges) of the radio frequency frames of period P2 by transmitting a response signal to the wheel unit.

[0065] The detection method includes a sixth step 9 during which the wheel unit measures the intensity of a series of response signals emitted by the electronic central unit to determine the shape of the signals. Wheel rotation, and therefore vehicle movement, is confirmed when the shape of the signals is periodic. In other words, the wheel unit analyzes the radio frequency power level it receives and identifies a (periodic) fingerprint, the signature of a relative rotation of the wheel.

[0066] Preferably, the rotation of the wheel and therefore the rolling of the vehicle are confirmed when the shape of the signals is sinusoidal.

[0067] The rotation of the wheel and therefore the rolling of the vehicle are schematically represented by result 10 of the diagram.

[0068] If the shape of the signals is not periodic, the wheel is considered stationary and the vehicle is in "parking" mode (step referenced 5).

[0069] The detection method includes a sixth step 11 during which the electronic central unit switches to rolling mode. The internal modes of the wheel unit are modified in order to optimize, in particular, its electrical consumption.

[0070] A delay step 12 can be added before looping back to the first step 1.

[0071] According to a second embodiment of the invention, during the step of detecting the rotational movement of the wheel, the wheel unit emits radio frequency frames, the rotation of the wheel being detected if the central electronic unit acknowledges receipt of the radio frequency frames by transmitting a response signal to the wheel unit.

[0072] If the vehicle was initially stationary, the wheel unit emitted radio frequency frames according to the first periodicity PL. The wheel unit increases the periodicity of the radio frequency frames according to the second periodicity P2 when the electronic central unit is activated.

[0073] On the contrary, if the vehicle was initially moving, the wheel unit emitted radio frequency frames according to the second periodicity P2. The wheel unit reduces the periodicity of the radio frequency frames according to the first periodicity PI when the electronic central unit becomes inactive.

[0074] In fact, when the vehicle is stationary, the electronic control unit is off. When the vehicle starts moving, the electronic control unit is switched on and begins responding to the wheel unit. This response allows the wheel unit to detect that the vehicle is moving.

[0075] According to the diagram in [Fig.2], the detection method includes a first step 13 during which the wheel unit emits radio frequency frames with a low periodicity PI when the vehicle is stationary (parking mode).

[0076] The detection method includes a second step 14 of determining the movement of the vehicle. If the vehicle is moving, the electronic central unit acknowledges receipt of the radio frequency frames from the wheel unit by transmitting a response signal to the wheel unit in a fourth step 15.

[0077] The wheel unit detects the response signal during a fifth step 16 and switches to rolling mode.

[0078] The periodicity of the radio frequency frames is increased according to the second periodicity P2 during a fifth step 17.

[0079] If the vehicle is stationary, a delay is applied during a sixth step 18 before to loop back to the first step 13.

Claims

Claims

1. A method for detecting a rotational movement of a body about an axis of rotation relative to a fixed structure, the body comprising a sensor for performing measurements on the body and comprising a first radio frequency transmitter / receiver for communicating with a second radio frequency transmitter / receiver provided on an electronic computer mounted on the fixed structure by means of low energy Bluetooth® communication to transmit the measurements to the electronic computer, the sensor being capable of transmitting radio frequency signals periodically and the electronic computer being capable of acknowledging receipt of the radio frequency signals by transmitting a radio frequency response signal to the sensor,characterized in that it comprises a step of detecting the rotational movement of the body by the sensor using the response signals transmitted by the electronic computer and a step of adapting the periodicity of the radiofrequency signals emitted by the sensor as a function of the rotation or non-rotation of the body.,

2. Detection method according to claim 1, characterized in that during the step of adapting the periodicity of the emitted signals, the sensor emits periodic radiofrequency frames intended to be received by the electronic computer according to a first periodicity PI when the body is not rotating, the sensor emitting periodic radiofrequency frames according to a second periodicity P2 when the body is rotating, P2 being strictly greater than PI.

3. Detection method according to any one of claims 1 or 2, characterized in that during the step of detecting the rotational movement of the body, the sensor measures the intensity of the response signal emitted by the electronic computer, the body being considered to be rotating if a variation in intensity is detected between two successive radiofrequency response signals, otherwise the body being considered to be immobile.

4. Detection method according to claim 3, characterized in that the variation in intensity between two successive radiofrequency response signals is considered significant if a detection threshold taking into account a margin of error is reached.

5. Detection method according to claim 3, characterized in that an average is carried out on several measurements to filter the radiofrequency signals.

6. Detection method according to any one of claims 3 to 5, characterized in that after detection of the rotation of the body, the sensor emits radiofrequency frames according to the second periodicity P2, the electronic computer acknowledging receipt of the radiofrequency frames of period P2 by transmitting a response signal to the sensor, the sensor measuring the intensity of a succession of response signals emitted by the electronic computer to determine a shape of the signals, the rotation of the body being confirmed when the shape of the signals is periodic, otherwise, the wheel being considered stationary if the shape of the signals is not periodic.

7. Detection method according to claim 2, characterized in that during the step of detecting the rotational movement of the body, the sensor emits radiofrequency frames, the rotation of the body being detected if the electronic computer acknowledges receipt of the radiofrequency frames by transmitting a response signal to the sensor, the sensor emitting radiofrequency frames according to the second periodicity P2.

8. Detection method according to claim 7, characterized in that the step of detecting the rotational movement of the body is carried out with a sensor in “presence state” mode in which short periodic signals are transmitted by the sensor to authorize a connection with the electronic computer.

9. Detection method according to any one of claims 1 to 8, characterized in that the detection method is a method for detecting the running of a motor vehicle comprising a pressure monitoring system intended to measure the pressure in a tire of a wheel of the vehicle, the wheel comprising a wheel unit capable of establishing low energy Bluetooth® communication to transmit pressure measurements to an electronic computer of a central electronic unit of the vehicle.

10. Motor vehicle characterized in that it implements the method of detecting a rotational movement of a body as defined according to any one of claims 1 to 9.

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