Method for assigning tire pressure monitoring units to the wheel positions of a vehicle

Description

[0001] The invention relates to a method for assigning tire pressure monitoring units of a tire pressure monitoring system of a vehicle to the various positions at which a wheel is mounted on the vehicle. The method is based on an assignment method having the features specified in the preamble of claim 1, as known, for example, from DE 10 2008 045 867 A1. Further tire pressure monitoring systems are known from DE102018218422 A1, US2015 / 054640 A1, US2009 / 066498 A1, JP2012144223 A, FR3075550 A1, and US9481216 B2.

[0002] Tire pressure monitoring units located in a vehicle's pneumatic tires transmit pressure data along with a characteristic identifier, which allows a central unit located on the vehicle to assign the tire pressure monitoring units and thus the pressure data they transmit to the individual wheels of the vehicle. Since a vehicle's tires, and thus the tire pressure monitoring units located within them, can be swapped or replaced, the central unit must reassign the characteristic identifiers to the respective wheel positions after each journey. This assignment can be performed using a statistical evaluation of the reception level.Signals from tire pressure monitoring units in vehicle tires that are located closer to a receiver of the evaluation unit are received on average over time with a higher reception level than signals from tire pressure monitoring units in vehicle tires that are further away.

[0003] In order for the central unit to be able to reliably assign tire pressure monitoring units to a wheel position, conventional tire pressure monitoring systems may need to receive a very large number of transmissions before a meaningful statistical evaluation is possible.

[0004] The object of the invention is therefore to show a way in which, in a system for monitoring tire pressure in vehicles, the number of transmissions required for assigning tire pressure monitoring units to the individual wheel positions of the vehicle can be reduced.

[0005] This object is achieved by a method having the features specified in claim 1. Advantageous developments of the invention are the subject of subclaims.

[0006] In a method according to the invention, a device that is movable relative to the vehicle, for example, a smartphone or a vehicle remote key, is used as an additional receiver. The device that is movable relative to the vehicle can then perform its own evaluation or pre-evaluation of the reception levels at which it received transmissions from the tire pressure monitoring devices, or simply communicate the reception levels at which it received transmissions from the tire pressure monitoring devices to the central unit. In this way, a central unit can more quickly and reliably assign the characteristic identifiers of the tire pressure monitoring units to the individual wheel positions of the vehicle.

[0007] Many vehicle owners already have a radio key or a smartphone, so that a method according to the invention allows for a faster assignment of tire pressure monitoring units to the wheel positions of a vehicle without additional hardware expenditure.

[0008] An advantageous development of the invention provides that the assignment process is initiated by unlocking the vehicle, and the central unit then instructs the tire pressure monitoring units to begin transmitting. This allows the tire pressure monitoring units to be assigned to the vehicle's wheel positions at a particularly early stage.

[0009] A further advantageous development of the invention provides that the central unit communicates with the tire pressure monitoring units via Bluetooth, in particular according to the industry standard Bluetooth low energy.

[0010] A further advantageous development of the invention provides that the central unit is connected to several receivers fixedly mounted on the vehicle. The more receivers connected to the central unit, the faster the location of the transmitting tire pressure monitoring unit relative to the receivers can be determined by evaluating the reception levels at each receiver, thus assigning it to a wheel position. Vehicles equipped with electronic locking systems typically have several receivers for signals from remote control keys. These receivers can also advantageously be used to receive signals from tire pressure monitoring devices.

[0011] A further advantageous development of the invention provides that the central unit locates the position of the device moving relative to the vehicle by evaluating the reception level of transmissions. For example, the central unit can thus determine whether the device is still moving relative to the vehicle or not. As long as the device is moving relative to the vehicle, it can naturally be assumed that the reception levels at which transmissions are received are constantly changing. However, even in this case, the relative relationships between the reception levels contain information that can be used to assign the tire pressure monitoring units to the wheel positions.For example, if the user of the vehicle is walking toward the vehicle, transmissions from tire pressure monitoring units mounted on wheels on the side of the vehicle facing the user are expected to be received at higher reception levels than transmissions from tire pressure monitoring units mounted on wheels on the side of the vehicle facing away from the user.

[0012] In general, for a vehicle with four wheels, one of the wheels, and thus one of the tire pressure monitoring devices, is always closest to the device that is moving relative to the vehicle. Consequently, the device usually receives transmissions from this tire pressure monitoring unit with the highest reception level. The vehicle wheel diagonally opposite this wheel is then usually the farthest away, so the lowest reception level is to be expected for this wheel. A simple analysis therefore shows that the tire pressure monitoring unit with the highest reception level is located diagonally opposite the tire pressure monitoring unit with the lowest reception level. Movement of the device relative to the vehicle can be quickly detected by a change in the reception level.

[0013] If the device that is mobile relative to the vehicle no longer moves relative to the vehicle, for example because the wearer of the device has taken a seat in the vehicle, the central unit can determine its position by evaluating the reception levels of the device's transmissions, particularly if the central unit is connected to several receivers fixed to the vehicle. Once the position of the device that is mobile relative to the vehicle has been determined, this device can be used like another receiver connected to the central unit.

[0014] A further advantageous development of the invention provides that the position of the device, which is movable relative to the vehicle, as well as the positions of the central unit are determined using GPS. In this way, the position of the device relative to the vehicle's central unit can be determined very quickly, so that this device can be used like an additional receiver connected to the central unit.

[0015] A further advantageous development of the invention provides that, when assigning the tire pressure monitoring units to the individual wheel positions of the vehicle, the central unit takes into account not only the reception levels of transmissions but also the transmission power with which the transmission in question was transmitted. If both the transmission power and the reception level are known, information about the distance between the transmitter and receiver can be determined, which simplifies the assignment. For example, the distance between the transmitter and receiver is, on average, approximately proportional to √(p S / p E , where p S is the transmission power and p E is the reception level.If the transmission power is also included in the evaluation of the reception levels, information about the distances of the individual tire pressure monitoring units to the receiver or receivers can be determined, which makes it easier to assign the tire pressure monitoring units to the individual wheel positions.

[0016] The transmission power can be explicitly specified in a transmission, for example, a data telegram. It is also possible for the central unit to communicate with the tire pressure monitoring units and specify the transmission power to each of them. If the device, which is movable relative to the vehicle, performs an evaluation or pre-evaluation of the reception levels, it can also take the transmission power into account by extracting it from the data telegrams or from a specification sent by the central unit.

[0017] A further advantageous development of the invention provides that the tire pressure monitoring units transmit signals with different transmission powers, for example, transmission powers that differ by a factor of 2 or more. In this way, the distance between the transmitter and receiver can be determined even more precisely by evaluating the transmission power and reception levels, since the reception level is a non-linear function of the transmission power. Typically, the relationship between reception level and transmission power is inversely proportional to the square of the distance between the receiver and transmitter, although this relationship can be impaired by shadowing and reflection effects.

[0018] It is possible for the individual tire pressure monitoring units to independently vary their transmission power and specify the respective transmission power in each transmission. However, it is generally more efficient for the central unit to communicate with the tire pressure monitoring units and, after receiving a transmission, instruct the tire pressure monitoring units to change the transmission power, particularly if the central unit specifies the transmission power at which a tire pressure monitoring unit should transmit. In this way, the central unit can, for example, cause only those tire pressure monitoring units that are not yet assigned to a wheel position to transmit at temporarily increased transmission power, for example, a transmission power increased by a factor of 2 or more, in particular a factor of 4 or more.Once a tire pressure monitoring unit is assigned to a wheel position, the central unit of this tire pressure monitoring unit can specify a minimum transmission power that is sufficient for reliable reception.

[0019] A further advantageous development of the invention provides for the use of the individual tire pressure monitoring units as additional receivers. By informing the central unit and the device movable relative to the vehicle of the reception level at which they received transmissions from other tire pressure monitoring units, the central unit can make an assignment even faster. The reception levels at which the tire pressure monitoring units received transmissions from other tire pressure monitoring units contain, particularly in combination with the associated transmission power, information about the distance between the respective tire pressure monitoring units.

[0020] A further advantageous development of the invention provides that the central unit also carries out a "time-of-flight" evaluation when assigning characteristic identifiers to the positions at which a wheel is mounted on the vehicle.

[0021] A "time-of-flight" evaluation can be performed within the framework of bidirectional communication, recording the time that elapses from the transmission of a signal by the central unit to the receipt of a response signal from the addressed tire pressure monitoring unit as "time-of-flight." Another possibility is to measure the time from the transmission of a signal to its receipt and evaluate it as "time-of-flight." For this purpose, the clocks of the tire pressure monitoring unit and the central unit are synchronized. For example, the central unit can then specify the exact time at which a transmission should begin to the tire pressure monitoring unit, or the tire pressure monitoring unit can specify the exact time at which transmission began in the transmission.

[0022] Through a "time-of-flight" analysis, the central unit receives information about the distance between the tire pressure monitoring unit and the central unit's receiver(s). The accuracy of this information can be improved through statistical analysis.

[0023] A further advantageous development of the invention provides that the central unit also performs an "angle-of-arrival" evaluation when assigning characteristic identifiers to the positions at which a wheel is mounted on the vehicle. In an "angle-of-arrival" evaluation, the direction of an incoming signal is determined by evaluating a phase shift that occurs between different antennas receiving the same transmission. This further accelerates the assignment of tire pressure monitoring devices to a vehicle's wheel positions.

Claims

1. A method of allocating tyre pressure monitoring units of a tyre pressure monitoring system of a vehicle to the various positions at which a respective wheel is mounted on the vehicle, wherein the tyre pressure monitoring units each contain a pressure sensor, a receiver and a transmitter, the transmitter sends data obtained from measurements of the pressure sensor together with a characteristic identifier of the tyre pressure monitoring unit, the tyre pressure monitoring system contains a central unit which receives transmissions from the tyre pressure monitoring units and, by evaluating reception levels, assigns the characteristic identifiers of the various tyre pressure monitoring units to one of the positions at which a respective wheel is mounted on the vehicle, characterised in that the transmissions from the tyre pressure monitoring units are also received by a device which is movable relative to the vehicle, preferably a radio key or a smartphone, the device, which is movable relative to the vehicle, transmits the reception levels with which the characteristic identifiers of tyre pressure monitoring units have been received or data obtained by evaluating the reception levels to the central unit, and the central unit also evaluates information received from the device moving relative to the vehicle in order to assign the characteristic identifier of the various tyre pressure monitoring units.

2. Method according to claim 1, characterised in that the central unit additionally takes into account the transmission power with which the received transmissions were transmitted when evaluating reception levels.

3. Method according to one of the preceding claims, characterised in that the central unit communicates with the tyre pressure monitoring units and specifies the transmission power of the tyre pressure monitoring units in each case.

4. Method according to one of the preceding claims, characterised in that the central unit locates the position of the device moving relative to the vehicle by evaluating the reception level of transmissions from the device.

5. Method according to one of the preceding claims, characterised in that the central unit is connected to a plurality of receivers arranged in a fixed position on the vehicle, preferably receivers for receiving signals from a radio key.

6. Method according to one of the preceding claims, characterised in that the position of the device movable relative to the vehicle and the positions of the central unit are determined by means of GPS.

7. Method according to one of the preceding claims, characterised in that the central unit also carries out a "time of flight" evaluation when assigning characteristic identifiers to the positions in which a wheel is mounted on the vehicle in each case.

8. Method according to one of the preceding claims, characterised in that the central unit also carries out an "angle of arrival" evaluation when assigning characteristic identifiers to the positions at which a respective wheel is mounted on the vehicle.

9. Method according to one of the preceding claims, characterised in that the tyre pressure monitoring units transmit data according to the Bluetooth industry standard.

10. Method according to one of the preceding claims, characterised in that the device, which is movable relative to the vehicle, carries out a preliminary evaluation or its own evaluation of the received levels in order to assign characteristic identifiers of the various tyre pressure monitoring units to a wheel position and transmits the result to the central unit.

11. Method according to one of the preceding claims, characterised in that the method is started by unlocking the vehicle and the central unit then instructs the tyre pressure monitoring units to commence their monitoring activity.