METHOD FOR DETERMINING THE POSITION OF WHEELS ON A VEHICLE

Description

State of the art

[0001] The invention relates to a method for determining the position of wheels on a vehicle by means of at least two acceleration sensors, wherein one is arranged on each of at least two wheels of the vehicle.

[0002] The invention further relates to a device for determining the position of wheels on a vehicle by means of acceleration sensors on the wheels of the vehicle, comprising at least two acceleration sensors, one of which is arranged on each of at least two wheels of the vehicle. Tire pressure monitoring systems, or TPMS systems, where TPMS stands for Tire Pressure Monitoring System, serve to monitor the tire pressure of motor vehicles in order to prevent accidents caused by incorrect tire pressure. Such systems are known from US 2016 / 297262 A1 and US 2014 / 167950 A1. Maintaining the optimal tire pressure for the specific vehicle reduces both fuel consumption and tire wear.Tire pressure monitoring systems can detect changes in tire pressure both actively, using electronic pressure sensors that transmit the pressure and identification wirelessly to a control unit at specific intervals, and passively, by monitoring changes in rolling circumference and characteristic vibration frequencies of the respective wheel. This requires knowing the position of each wheel on the vehicle. Disclosure of the invention

[0003] In one embodiment, the present invention provides a method for determining the position of wheels on a vehicle by means of at least two acceleration sensors, wherein one is arranged on each of at least two wheels of the vehicle. The process includes the following steps: calculating the rotation time of at least one of the at least two wheels based on a determined centrifugal force using the respective accelerometer; determining the tangential acceleration of the wheel using the respective accelerometer over a time interval that corresponds to at least half the rotation time; defining and / or adjusting the starting point of the time interval depending on the magnitude of the initial and / or final value of the tangential acceleration compared to the temporal position of an extremum of the tangential acceleration within the time interval; and determining the temporal position of the most recent extremum of the tangential acceleration within the time interval.wherein at least two temporal positions of the most recent extrema in different time intervals are determined by means of the steps, and wherein in a further step the position of the wheel on the vehicle is determined by comparing the at least two determined temporal positions with further predefined data.

[0004] In one embodiment, the present invention provides a device for determining the position of wheels on a vehicle, comprising at least two acceleration sensors, one of which is arranged on each of at least two wheels of the vehicle, a data provision device that provides further data from the at least two wheels, and an evaluation device that is connected to the acceleration sensors and the data provision device and that is configured to perform the following steps: calculating a rotation time of at least one of the at least two wheels based on a determined centrifugal force using data from the respective acceleration sensor; determining a tangential acceleration of the wheel using data from the respective acceleration sensor over a time interval that corresponds to at least half of the rotation time.Determining and / or adjusting the starting point of the time interval depending on the magnitude of the initial and / or final value of the tangential acceleration compared to the temporal position of an extremum of the tangential acceleration within the time interval; determining the temporal position of the most recent extremum of the tangential acceleration within the time interval; and wherein, by means of the steps, at least two temporal positions of most recent extrema in different time intervals are determined; and wherein the position of the wheel on the vehicle is determined by the evaluation unit through a comparison of the at least two determined temporal positions with further predefined data from the provisioning device.

[0005] One of the advantages gained is that the position of wheels on the vehicle can be determined in a simple, energy-efficient, fast and reliable way. For example, it can be determined whether a pressure measured by the TPMS was at the front left wheel or the rear right wheel.

[0006] Further features, advantages and further embodiments of the invention are described below or become apparent therein.

[0007] According to an advantageous embodiment of the invention, a new starting point for the time interval is defined based on a predetermined number of samples if the extremum, in the form of a maximum, does not lie within that time interval. This allows a suitable new starting point to be determined simply and reliably, thus increasing the probability of finding the most recent extremum of the tangential acceleration, in this case the maximum, within the time interval when the time position is re-determined. In particular, the most recent extremum, here the maximum, can be found with near certainty, i.e., with a high degree of probability, even with a single re-determination of the time position. A "sample" is generally understood to be a point in time at which a value, for example, an acceleration, is measured.

[0008] According to a further advantageous embodiment of the invention, in the case of an extremum in the form of a maximum, the new starting point in time is set, if the initial value is greater than the final value, as at least 1.525 times the number of samples and at most 1.725 times the number of samples, in particular 1.625 times the number of samples, and wherein the new starting point in time is set, if the initial value is less than the final value, as at least 0.4 times the number of samples and at most 0.6 times the number of samples, in particular 0.5 times the number of samples. This further increases the probability of finding the most recent extremum of the tangential acceleration, in this case the maximum of the tangential acceleration, in the next time interval of acceleration values ​​when re-determining the temporal position.

[0009] According to a further advantageous embodiment of the invention, in the case of a minimum, the new starting point in time is set to be between 1.1 and 1.3 times the number of samples, in particular 1.2 times the number of samples, if the initial value is greater than the final value, and between 0.6 and 0.8 times the number of samples, in particular 0.7 times the number of samples, if the initial value is less than the final value. This further increases the probability, even in the case of a minimum as an extremum, of finding the most recent extremum of the tangential acceleration, in this case the maximum of the tangential acceleration, in the next time interval of acceleration values ​​when re-determining the temporal position.

[0010] According to a further advantageous embodiment of the invention, the temporal position of the most recent extremum is determined using a fitted polynomial of at least the second degree. This enables a sufficiently accurate determination of the extremum while requiring minimal computational resources.

[0011] According to a further advantageous embodiment of the invention, the sampling frequency is determined based on the time interval. This allows the same number of samples, i.e., points in time at which acceleration data is determined, to be used flexibly for any length of time interval.

[0012] According to a further advantageous embodiment, the additional specified data are provided by another vehicle system, in particular an ABS system. This allows the respective wheel to be identified in a particularly simple manner by comparing, correlating, or otherwise analyzing the additional data with at least two specific temporal positions of the most recent extremum. To identify the position of a wheel, the described procedure is performed multiple times. Several temporal positions of the most recent extremum, especially the maximus, are determined within the respective time intervals and then transmitted to an evaluation unit or similar device for wheel identification.

[0013] According to a further advantageous embodiment of the invention, if the position of the wheel cannot be determined with a predetermined accuracy, the steps of the method are repeated. This improves the reliability in determining the position of the wheel on the vehicle.

[0014] According to a further advantageous embodiment of the invention, the quality of the polynomial fit is determined and, in particular, transferred to an evaluation unit. The advantage of this is that an additional parameter is available for evaluation, which can be used, for example, to determine whether it is necessary to re-record acceleration data, determine the extremum, etc.

[0015] According to a further advantageous embodiment of the invention, a correction is applied to the temporal position of the extremum, which depends on the period of a wheel revolution and on the radial and tangential acceleration of the wheel. In other words, the temporal position of the extremum undergoes a correction that depends on the period of a wheel revolution and the acceleration values ​​in the x- and z-directions. Thus, when the acceleration sensor on the rim is rotated, a correction is made to the temporal position of the most recent extremum, in this case the maximum, which overall improves the reliability and robustness of the method.

[0016] Further important features and advantages of the invention will become apparent from the dependent claims, the drawings, and the accompanying description of the figures based on the drawings.

[0017] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0018] Preferred embodiments and configurations of the invention are shown in the drawings and are explained in more detail in the following description, wherein identical reference numerals refer to identical or similar or functionally identical components or elements.

[0019] This is shown in schematic form Figure 1 shows a flowchart of a method according to an embodiment of the present invention; and Figure 2 shows a device according to an embodiment of the present invention.

[0020] Figure 1 shows in schematic form a flowchart of a method according to an embodiment of the present invention.

[0021] In Figure 1 Figure 1 shows a method for determining the position of a wheel on a vehicle using an acceleration sensor on the wheel.

[0022] After the procedure is started in step S0, the accelerations of the wheel are determined individually along the x- and z-directions using the sensor in a first step S1. The acceleration in the x-direction represents the tangential acceleration at the location of the accelerometer. The acceleration in the z-direction represents the radial acceleration at the location of the accelerometer. Based on the measured accelerations, the centrifugal acceleration can then be determined in a second step S2.

[0023] In the next step, S3, it is checked whether tire data is available for the respective wheel. Based on this data, the rotational speed and thus the rotation period can be determined. If this data is available, the corresponding rotation period can be determined in step S4b. If this tire data is not available, a corresponding rotation period is estimated or assumed according to step S4a.

[0024] The resulting rotation period now forms the starting point for determining the wheel's position. In the next step, S5, the tangential acceleration is measured for half the rotation period, and then, for the first time, an attempt is made to locate the temporal position of the most recent maximum in the acceleration data from the accelerometer, as described in step S6. In step S7, it is checked whether the temporal position of the most recent maximum could be determined. If the temporal position of the most recent maximum cannot be precisely determined, the following steps are performed.

[0025] The accelerometer, fixed to the rim, rotates with the wheel and, as previously described, outputs acceleration signals along the x-axis for tangential acceleration. These signals exhibit oscillatory behavior while the vehicle is in motion. This oscillating signal is induced by gravity. The part of the autolocation process that determines the wheel's rotational position calculates a specific point in time, the so-called lookback time. This is the temporal position of the most recent maximum in the accelerometer's acceleration data. This corresponds to the 3 o'clock or 9 o'clock position of the wheel. To determine this, the accelerometer outputs corresponding acceleration data at regular intervals during vehicle operation. This data is then analyzed to determine the lookback time.For this purpose, a sampling rate for the accelerometer data is adjusted, and sampling is performed over a period of time such that a time window of half a wheel revolution is sampled at a time. The sampling duration and frequency are determined by calculating the centrifugal force and subsequently the rotation period. The procedure for calculating the lookback time fits a first polynomial of at least the second degree, in particular the second degree, to the initial acceleration data. If a maximum acceleration is found in the data sampled over half a rotation period, or if a maximum acceleration is found within the fitted interval of the polynomial of at least the second degree, in particular the second degree, the lookback time is determined by examining the extreme values ​​of the fitted polynomial of at least the second degree, in particular the second degree.The fitting or adaptation of the polynomial of at least the second degree, in particular the second degree, as well as the extremum analysis to determine the lookback time, is summarized in step S6.

[0026] If no maximum is found in the data sampled over half a rotation period, or if no maximum is found within the fitted interval of the polynomial of at least the second degree, in particular the second degree, the accelerometer outputs data again. This query takes place in step S7.

[0027] The points in time from which new data are sampled to ensure a successful data fit—that is, to determine the temporal position of a maximum—can depend on various criteria listed below. In step S8, the number of samples S for a fit is specified. The points in time to be described are given as discrete values, counted from the first sample of the initial data sampling. In other words, a sampling process has multiple values ​​representing accelerations at discrete points in time, the "samples." For example, the time '20' means that this contains the data from the 20th sample, located 20 times after the first sample. This is particularly possible when a fixed sampling period is specified.

[0028] First, it is checked whether a minimum was modeled in step S10 or a maximum in step S20 during the initial fitting of the polynomial of at least the second degree, in particular the second degree. If a minimum was modeled according to step S10, it is checked whether the initial value of the fitting over half a rotation period is greater according to step S11 or less according to step S13 than the final value of the fitting over half a rotation period. If it is greater than the final value according to step S11, the number of S samples is resampled from the time of subsequent samples using the function 'Round Up (6 / 5*S)' according to step S12, and a polynomial of at least the second degree, in particular the second degree, is fitted again.

[0029] If, according to step S13, the initial value is smaller than the final value, the function 'RoundUp(7 / 10*S)' in step S14 re-samples the number of S samples from that point onward and refits them. If the first fitting modeled a maximum according to step S20, it is only in step S21 that a check is performed to see if the maximum lies within the first fitting. If this is not the case, a check is also performed to see if the initial value of the fitting over half a rotation period is greater (according to step S22) or less (according to step S24) than the final value of the fitting over half a wheel or rotation period.

[0030] If it is greater than the final value, according to step S23, the number of S samples is re-sampled from the time point onwards using the function 'RoundUp(13 / 8*S)' and re-fitted. If it is less than the final value, according to step S25, the number of S samples is re-sampled from the time point onwards using 'RoundUp(1 / 2*S)' and also re-fitted. For this purpose, acceleration data of the tangential acceleration over half a rotation period are recorded again according to step S30, analogous to step S5, and then, according to step S31, the autolocation procedure described above is performed again. In a further step S32, analogous to step S7, it is checked whether the temporal position of the most recent maximum could be determined with sufficient accuracy. If so, a correction of the determined temporal position of the extremum, here the maximum, is performed in step S33.This correction corresponds to . T ⋅ tan − 1 − a x a z 2 π , where T corresponds to the period of one wheel revolution, axe the tangential acceleration and az The radial acceleration. The procedure then ends according to step S34. Steps S0-S34 are collectively referred to as step S35. At least two steps, S35-1 and S35-2, are performed to determine at least two temporal positions of the most recent maximum. Based on the temporal positions of these two most recent maxima, the position of each wheel can then be determined in a further procedure, S40, which is independent of steps S0-S34.

[0031] The steps S35-1, S35-2, ..., S35-n, n>=2 can be performed continuously and / or periodically, for example with a period of 10 seconds.

[0032] In each of the cases S10-S25, particularly during the second fitting, the maximum will now lie within the fitting interval of the data, and the lookback time can be easily calculated by examining extreme values ​​according to step S31, analogous to S6. In this embodiment, the determined and corrected at least two lockback time value data points are subsequently sent to a receiver, which also receives ABS speed data from each of the wheels. At least two such data packets are processed and compared on the receiver, requiring at least two passes S0-S34, and thus the position of the wheels is identified (step S40).

[0033] Figure 2 shows a device according to an embodiment of the present invention.

[0034] In Figure 2 A schematic diagram shows a device for determining the position of wheels on a vehicle using an acceleration sensor on one wheel of the vehicle.

[0035] The device 1 comprises at least two acceleration sensors 2, one of which is arranged on each wheel of the vehicle, the vehicle having at least two wheels. Furthermore, the device 1 comprises a data provision unit 4, which provides additional data from the wheel, and an evaluation unit 3, which is connected to the acceleration sensors 2 and the data provision unit 4 and which is configured to perform the following steps. Calculating a revolution time of at least one of the at least two wheels based on a determined centrifugal force using data from the respective accelerometer 2, determining a tangential acceleration of the wheel using data from the respective accelerometer 2 over a time interval that corresponds to at least half the revolution time, defining and / or adjusting the starting point of the time interval depending on the magnitude of the initial and / or final value of the tangential acceleration compared to the temporal position of an extremum of the tangential acceleration in the time interval, and wherein at least two temporal positions of temporally most recent extrema in different time periods are determined by means of the steps and wherein the position of the wheel on the vehicle is determined by the evaluation unit by comparing the at least two determined temporal positions with further specified data of the provisioning device.

[0036] In summary, at least one embodiment of the present invention has at least one of the following features and / or enables at least one of the following advantages: Reliable and fast detection of the position of a wheel on the vehicle. Simple, energy-efficient and cost-effective implementation.

[0037] In other words, embodiments of the invention utilize acceleration data from accelerometers, which are, for example, mounted on each wheel rim, to determine the different rotational speeds of the wheels during a vehicle cornering. This is done, for example, by means of a correlation analysis with ABS speed data. A predetermined rotational angle position of the wheels, expressed as a point in time (the lookback time), is repeatedly determined from the acceleration data and repeatedly compared with the ABS speed data for each wheel. The less the compared values ​​vary in terms of difference, the more likely a wheel will be identified.

[0038] Although the present invention has been described using preferred embodiments, it is not limited to these, but can be modified in many ways.

Claims

1. Method for determining the position of wheels on a vehicle by means of at least two acceleration sensors, wherein one is arranged in each case on each of at least two wheels of the vehicle, comprising the steps of - calculating (S4a, S4b) a revolution time of at least one of the at least two wheels based on an ascertained centrifugal force by means of the respective acceleration sensor (2), - ascertaining (S5) a tangential acceleration of the wheel by means of the respective acceleration sensor (2) over a period of time which corresponds to at least half the revolution time, - determining (S6, S31) the temporal position of the temporally most recent extreme of the tangential acceleration in the period of time, and wherein at least two temporal positions of temporally most recent extremes in different periods of time are determined by means of the steps (S0-S34), and wherein in a further step (S40) the position of the wheel on the vehicle is effected by comparing the at least two determined temporal positions with further predefined data, characterized by - setting and / or adjusting (S10-S14, S20-S25) the start point of the period of time on the basis of the size of the starting value and / or end value of the tangential acceleration in comparison with the temporal position of an extreme of the tangential acceleration in the period of time.

2. Method according to Claim 1, wherein a new temporal start point for the period of time is defined on the basis of a predefined number of samples if the extreme in the form of a maximum is not in the period of time.

3. Method according to Claim 2, wherein, in the case of an extreme in the form of a maximum, the new temporal start point is set to be at least 1.525 times the number of samples and at most 1.725 times the number of samples, in particular 1.625 times the number of samples, if the starting value is greater than the end value, and wherein the new temporal start point is set to be at least 0.4 times the number of samples and at most 0.6 times the number of samples, in particular 0.5 times the number of samples, if the starting value is less than the end value.

4. Method according to one of Claims 1-3, wherein, in the case of a minimum, the new temporal start point is set to be between 1.1 times and 1.3 times the number of samples, in particular 1.2 times the number of samples, if the starting value is greater than the end value, and wherein the new temporal start point is set to be between 0.6 times and 0.8 times the number of samples, in particular 0.7 times the number of samples, if the starting value is less than the end value.

5. Method according to one of Claims 1-4, wherein the temporal position of the temporally most recent extreme is determined using an adapted at least second degree polynomial.

6. Method according to Claim 2, wherein the frequency of the samples is determined based on the period of time.

7. Method according to one of Claims 1-6, wherein the further predefined data are provided by a further vehicle system (4), in particular an ABS system.

8. Method according to one of Claims 1-7, wherein, if the position of the wheel cannot be determined with a predefined accuracy, the steps of the method are carried out again.

9. Method according to Claim 5, wherein the quality of the adaptation of the polynomial is ascertained and is in particular transferred to an evaluation device.

10. Method according to one of Claims 1-9, wherein a correction (S33) is carried out for the temporal position of the extreme, which correction is dependent on the period duration of a wheel revolution and on the radial and tangential acceleration of the wheel.

11. Apparatus (1) for determining the position of wheels on a vehicle by means of an acceleration sensor on a wheel of the vehicle, comprising at least two acceleration sensors (2), wherein one is arranged in each case on each of at least two wheels of the vehicle, a provision device (4) that provides further data relating to the at least two wheels, and an evaluation device (3) which is connected to the acceleration sensors (2) and the provision device (4) and is designed to carry out the following steps of: - calculating a revolution time of at least one of the at least two wheels based on an ascertained centrifugal force on the basis of data from the respective acceleration sensor (2), - ascertaining a tangential acceleration of the wheel on the basis of data from the respective acceleration sensor (2) over a period of time which corresponds to at least half the revolution time, - determining the temporal position of the temporally most recent extreme of the tangential acceleration in the period of time, and wherein at least two temporal positions of temporally most recent extremes in different periods of time are determined by means of the steps (S0-S34), and wherein the position of the wheel on the vehicle is effected by comparing the at least two determined temporal positions with further predefined data from the provision device (4) by way of the evaluation device (3), characterized by - setting and / or adjusting the start point of the period of time on the basis of the size of the starting value and / or end value of the tangential acceleration in comparison with the temporal position of an extreme of the tangential acceleration in the period of time.