Method and device for locating wheels of a vehicle as well as a tire pressure monitoring system

Abstract

A method and a device locate wheels of a vehicle, according to which method at least one wheel has wheel electronics. In accordance with the method, a signal is received on the vehicle side by the wheel electronics, which signal allows conclusions to be drawn about a point in time at which the wheel assumed a first rotation angle position. The signal contains a plurality of packets. At least one time interval between the packets is determined, and at least one estimated value for the at least one time interval is provided on the basis of the at least one determined time interval.

Claims

1. A method for locating wheels of a vehicle and at least one of the wheels has wheel electronics, which comprises the following steps of: receiving a signal from the wheel electronics which permits conclusions about a time at which a wheel assumed a first rotary angle position, the signal containing a plurality of packets received with a delay; generating first rotary angle information based on the signal by determining the time at which the wheel assumed the first rotary angle position based on one of the plurality of packets; determining second rotary angle positions of the wheels by sensors, the sensors are each assigned to a specific position on the vehicle; generating second bits of rotary angle information based on the second rotary angle positions; comparing the first rotary angle information with the second bits of rotary angle information; determining the wheel assigned to the wheel electronics depending on the comparing step; determining, from the signal that has been received from the wheel electronics, at least one time interval between the plurality of packets in the signal that has been received from the wheel electronics; and generating at least one estimated value for the at least one time interval based on the at least one time interval determined from the signal received from the wheel electronics, wherein the at least one estimated value for the at least one time interval is a time period.

2. The method according to claim 1, wherein the wheel electronics execute the following steps: determining the first rotary angle position of the wheel assigned to the wheel electronics; and transmitting the signal which permits conclusions about the time at which the wheel assumed the first rotary angle position.

3. The method according to claim 1, wherein each of the packets has a number which indicates a rank assumed by the packets within a sequence of the plurality of packets, and a step of determining the time based on the at least one estimated value for the at least one time interval and the number of a packet is performed if a received signal does not contain a first packet.

4. The method according to claim 1, wherein the step of determining at least one time interval between the packets is executed several times, and determined time intervals are saved.

5. The method according to claim 4, which further comprises executing the method in a plurality of sequential periods, and only time intervals of most recent n periods are saved.

6. The method according to claim 4, wherein the step of generating the at least one estimated value includes the further step of forming at least one average from saved time intervals.

7. The method according to claim 1, wherein the step of generating the at least one estimated value comprises the further steps of: calculating a first product by multiplying the at least one time interval determined in a current period by a predetermined value which lies between 0 and 1; calculating a second product by multiplying an estimated value of a preceding period by one minus the predetermined value, wherein the preceding period directly precedes the current period in time; and calculating the estimated value of the current period by adding the first and second product.

8. The method according to claim 1, wherein the step of determining at least one time interval between the packets is only executed when a received signal contains all anticipated packets.

9. A device for locating wheels of a vehicle and at least one wheel has wheel electronics, the device comprising: a first reception unit for receiving a signal from the wheel electronics which permits conclusions about a time at which the wheel assumed a first rotary angle position; a first processing unit for generating first rotary angle information based on the signal; sensors being each assigned to a specific position on the vehicle; a second reception unit for receiving second rotary angle positions of the wheels measured by said sensors; a second processing unit for providing second bits of rotary angle information based on the second rotary angle positions; a comparison unit for comparing the first rotary angle information with the second bits of rotary angle information; a locating unit for locating the wheel assigned to the wheel electronics depending on a result of said comparison unit; said first reception unit being set up to receive the signal containing a plurality of packets which are received with a delay; said first processing unit being set up to determine the time at which the wheel assumed the first rotary angle position based on one of the plurality of packets; an interval-determining device configured for determining at least one time interval between the plurality of packets from the signal received from the wheel electronics; and an estimating apparatus for generating at least one estimated value for the at least one time interval based on the at least one time interval determined from the signal received from the wheel electronics, wherein the at least one estimated value for the at least one time interval is a time period.

10. A tire pressure monitoring system, comprising: a device according to claim 9.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) Additional advantages and details of embodiments of the present invention will be explained with reference to the figures. In the following:

(2) FIG. 1a shows a vehicle from the side;

(3) FIG. 1b shows a schematic representation of the vehicle from below in which essential elements of a tire pressure monitoring system are depicted;

(4) FIG. 2 shows a wheel equipped with wheel electronics;

(5) FIG. 3 shows a signal consisting of a plurality of packets;

(6) FIG. 4a shows an embodiment of a device according to the invention;

(7) FIG. 4b shows a sketch to explain the comparison and

(8) FIG. 5 shows method steps of an embodiment of a method according to the invention;

(9) FIG. 6 shows additional steps of an embodiment of a method according to the invention; and

(10) FIG. 7 shows additional steps of another embodiment of a method according to the invention.

DESCRIPTION OF THE INVENTION

(11) If not otherwise indicated, equivalent and equivalently-acting elements will be cited with the same reference signs in the following description.

(12) FIG. 1a shows a side view of a vehicle 1. The two wheels 2b and 2d can be seen. The same vehicle is shown again from below in FIG. 1b, wherein essential elements of a tire pressure monitoring system are drawn. The four wheels 2a to 2d each have wheel electronics 3a to 3d. The wheels 2a to 2d are each assigned sensors 4a to 4d arranged on the vehicle. These sensors can for example be ABS sensors or ESP sensors. The sensors 4a to 4d are connected to an embodiment of a device 5 according to the invention. This device is, inter alia, set up to receive signals from the wheel electronics 3a to 3d.

(13) FIG. 2 shows the wheel 2a once again in a side view, wherein it can be seen that the wheel electronics 3a rotate with the wheel when the wheel 2a rolls on the ground 6.

(14) The wheel unit 3a transmits a signal 7 which is shown in FIG. 3 and comprises the packets 7a, 7b and 7c. The wheel unit 3a transmits a plurality of packets because the reception unit arranged in the vehicle may not be able to receive one or more of the packets, for example due to shading from body parts. The time t is plotted on the bottom scale. At time t.sub.0, the wheel passes through the first rotary angle position. This can for example be the highest position on the wheel (0), or the middle of the tire footprint (180), or the point of entrance or point of exit into or out of the tire footprint. After a delay dt.sub.0, the first packet 7a is sent. The delay dt.sub.0 can be determined beforehand or during operation by the wheel electronics. At time t.sub.1, the packet 7a has been completely received by the vehicle. The interval between the first packet 7a and the second packet 7b is dt.sub.1, and the interval between the second packet 7b and the third packet 7c is dt.sub.2. The second packet 7b is completely received at time t.sub.2, and the packet 7c is completely received at time t.sub.3. The intervals between the packets dt.sub.1 and dt.sub.2 are measured continuously, and estimated values for these intervals are offered on their basis. The delay dt.sub.0 with reference to the clock of the wheel electronics is well known. dt.sub.0 can be adapted to any clock deviations from the relationship between the interval dt.sub.1 estimated by the vehicle in comparison to an interval well known by the wheel unit between the first and second packet with reference to the wheel electronics clock. Given a knowledge of the delay dt.sub.0 and the intervals dt.sub.1 and dt.sub.2 as well as the transmission durations for the packets 7a, 7b and 7c, the time at which the wheel assumed the first rotary angle position could be calculated retroactively for example from the receive time t.sub.3 of the third packet to the time t.sub.0. In order to infer t.sub.0 from t.sub.2, only the intervals dt.sub.0 and dt.sub.1 as well as the transmission durations of the packets 7a and 7b must be known. The invention is not restricted to a signal with three packets. Instead, any number of packets can be used as long as the number is at least two.

(15) The problem of the imprecision of clocks of wheel electronics will be illustrated with reference to the interval dt.sub.1.

(16) Conventional clocks have an imprecision of about 2 to 5%. In the following example, an imprecision of 5% will be assumed. Let us assume that the interval dt.sub.1 is 200 milliseconds, and the vehicle is moving at a speed of 150 km/h. A clock imprecision of 5% would then approximately correspond to an angle imprecision a of 75 degrees. This results from the following formula:
=imprecision in %*dt.sub.1*speed*360
tire circumference,

(17) wherein 2 m was assumed for the tire circumference. The angle imprecision of 75 causes locating to generally take longer which, in certain circumstances, may not even converge. In U.S. Pat. No. 8,332,104 B2 for example, the intervals dt.sub.1 and dt.sub.2 are permanently programmed in the vehicle control unit. They are therefore not regularly determined to provide current estimated values for the time intervals; accordingly, the just-described angle imprecisions arise in U.S. Pat. No. 8,332,104 B2 which cause the method to converge only slowly.

(18) FIG. 4a shows an embodiment of a device for locating wheels of a vehicle in which at least one wheel has wheel electronics. The shown device 8 comprises a first reception unit 9 for receiving a signal from the wheel electronics that permits conclusions about a time t.sub.0 at which the wheel assumed a first rotary angle position. The reception unit is set up to receive a signal consisting of a plurality of packets which are received at a delay. In addition, the device 8 has a first processing unit 10 to generate first rotary angle information based on the signal. This is set up to determine a time t.sub.0 at which the wheel assumed the first rotary angle position based on one of the plurality of packets. For this purpose, the first processing unit 10 is connected to an interval-determining device 11 for determining at least one time interval between the packets, and an estimating apparatus 12 for providing at least one estimated value for the at least one time interval based on the determined at least one time interval.

(19) Furthermore, the device 8 comprises a second reception unit 13 to receive rotary angle positions of the wheels measured by sensors which are each assigned to a specific position in the vehicle. These can be for example ABS sensors or ESP sensors. A second processing unit 14 provides second bits of rotary angle information based on the second rotary angle positions. This information can in particular be the times at which, from the perspective of the sensors, the assigned wheel assumed the second rotary angle position, which preferably corresponds to the first rotary angle position.

(20) A comparison unit 15 uses the first rotary angle information of the first processing unit 10 and the second bits of rotary angle information of the second processing unit 14, and compares them with each other. Depending on the result from the comparison unit 15, the locating unit 16 locates the wheel assigned to the wheel electronics.

(21) One embodiment of this comparison and locating will be explained further below with reference to FIG. 4b. At the top, the figure shows the wheel 2c with wheel electronics 3c which are currently in the first rotary angle position . The first rotary angle information indicates when the wheel electronics 3c were in the first rotary angle position . In the present example, the first rotary angle information accordingly corresponds to t.sub.0. In the middle of FIG. 4b, time bars are plotted for each of the four wheels 2a-2d. The bar B1 indicates that the wheel 2a was in the second rotary angle position at time t.sub.a. Accordingly, the bar B2 illustrates that the wheel 2b was in the second rotary angle position at time t.sub.b. The bars B3 and B4 correspond to the wheels 2c and 2d. At time t.sub.b, the wheel 2c assumed the second rotary angle position, whereas the wheel 2d was in this second rotary angle position at time t.sub.d.

(22) At the bottom in FIG. 4b, the wheels 2a-2d are depicted with their wheel electronics 3a-3d at time t.sub.0. At time t.sub.0, the wheel electronics 3a are still before the second rotary angle position .sub.1. Consequently, they pass through the second rotary angle position after t.sub.0, as illustrated by the bar B1. The wheel electronics 3b have already passed through the second rotary angle position .sub.2. From the perspective of the sensor which is permanently assigned to the corresponding position in the vehicle, the wheel electronics 3c are almost exactly in the second rotary angle position .sub.3 at time t.sub.0.

(23) At time t.sub.0, the wheel electronics t.sub.d have already passed through the second rotary angle position .sub.4 the longest.

(24) As can be seen in FIG. 4b, the time t.sub.c is closest to the time t.sub.0 so that, by means of a corresponding comparison, it can be concluded that the wheel electronics which transmitted the received signal are the wheel electronics 3c assigned to the wheel 2c. The deviations between t.sub.0 and t.sub.c can result in particular from measuring imprecisions. Accordingly, the wheel can be correspondingly located by comparing the first rotary angle information t.sub.0 with the second bits of rotary angle information t.sub.a-t.sub.d.

(25) FIG. 5 shows steps of an embodiment of a method according to the invention. In step S1, first a first rotary angle position of a wheel is determined, to which the wheel electronics are assigned. In step S2, a signal is then transmitted by the wheel electronics to a vehicle receiver which permits conclusions to be made about a time at which the wheel assumed the first rotary angle position. This signal is received in step S3.

(26) Based on the signal, first rotary angle information is generated in step S4. This step comprises determining the time at which the wheel assumed the first rotary angle position. One of the plurality of packets is used for this purpose. Second rotary angle positions of the wheels are determined in step S5 by sensors which are each assigned to a specific position in the vehicle. Based on these second bits of rotary angle positions, second bits of rotary angle information are provided (step S6). A comparison of the first rotary angle information with the second bits of rotary angle information then occurs in step S7 so that the wheel assigned to the wheel electronics can be located in step S8 depending on this comparison.

(27) FIG. 6 illustrates an embodiment of a routine which provides an estimated value for the method according to the invention. First, a time interval between the received packets is determined in step S9. In step S10, at least one estimated value is then provided for the at least one time interval based on the determined at least one time interval.

(28) With the assistance of this estimated value, the cited time can be generated in the step of generating based on the at least one estimated value for the least one time interval and the number of a packet.

(29) FIG. 7 shows another embodiment of a routine which provides an estimated value for the method according to the invention. First, a current time interval A.sub.t is determined in step S11 during the current period t. On the basis of this current time interval A.sub.t, the estimated value S.sub.t of the current period is determined in step S12 based on the following formula:
S.sub.tA.sub.t.Math.+S.sub.t-1.(1)
wherein A.sub.t, as already mentioned above, designates the current time interval in the current period, and S.sub.t designates the estimated value in the current period. S.sub.t-1 is the estimated value of the preceding period. symbolizes a value between 0 and 1. The current time interval in the current period A.sub.t, weighted as a correction factor for the estimated value of the preceding period S.sub.t-1, is used in the estimated value of the current period S.sub.t. Accordingly, only one estimated value, which is correspondingly updated, must be saved in each period.

(30) By means of the method according to the invention, each of the packets can be used in order to draw conclusions about the time at which the wheel assumed the first rotary angle position. The time intervals can be determined repeatedly so that deviations between the clocks of the wheel units and their imprecisions are compensated.

(31) In this manner, wheels of a vehicle can be located faster.

(32) The explanations made with reference to the figures are purely illustrative and are not to be interpreted restrictively.

(33) Numerous changes can be made to the described embodiments without departing from the scope of protection as defined in the accompanying claims.

LIST OF REFERENCE NUMBERS

(34) 1 Vehicle

(35) 2a to 2d Wheel

(36) 3a to 3d Wheel electronics

(37) 4a to 4d Sensor which is assigned to a specific position in the vehicle

(38) 5 Device for locating wheels of a vehicle

(39) 6 Ground

(40) 7 Signal

(41) 7a to 7c Packet

(42) t.sub.0 Time at which the wheel assumed the first rotary angle position

(43) t.sub.1 Receive time of the first packet

(44) t.sub.2 Receive time of the second packet

(45) t.sub.3 Receive time of the third packet

(46) dt.sub.0 Interval between t.sub.0 and the beginning of sending the first packet

(47) dt.sub.1 Interval between the first and second packet

(48) dt.sub.2 Interval between the second and third packet

(49) 8 Embodiment of a device according to the invention

(50) 9 First reception unit

(51) 10 First processing unit

(52) 11 Interval-determining device

(53) 12 Estimating apparatus

(54) 13 Second reception unit

(55) 14 Second processing unit

(56) 15 Comparison unit

(57) 16 Locating unit

(58) First rotary angle position

(59) .sub.1-.sub.4 Second rotary angle position

(60) B1-B4 Bars for depicting the time at which the corresponding wheel assumed the second rotary angle position

(61) t.sub.a-t.sub.d Second bits of rotary angle information

(62) S1 Determination of a first rotary angle position

(63) S2 Transmission of a signal

(64) S3 Reception of the signal

(65) S4 Generation of first rotary angle information

(66) S5 Determination of second rotary angle positions

(67) S6 Provision of second bits of rotary angle information

(68) S7 Comparison of the first rotary angle information with the second bits of rotary angle information

(69) S8 Locating

(70) S9 Determination of at least one time interval between the packets

(71) S10 Provision of at least one estimated value for the at least one time interval

(72) S11 Determination of at least one time interval between the packets

(73) S12 Provision of at least one estimated value for the at least one time interval