Method for determining rotational speed and / or momentum derived from rotational speed, computer program product, data carrier, and computer device

Abstract

To advantageously improve the accuracy of determining actual signal values, particularly at low speeds.SOLUTION: A method for determining a rotational speed and / or momentum derived from the rotational speed using a rotational speed sensor, extrapolates or interpolates a corrected third signal value (ωp) at a selected reference time point depending on an assessed information age (TI) of a first signal value (ωm) evaluated at a first evaluation time point (ta) of the rotational speed sensor, and a second signal value (ωb) that temporally precedes the first signal value (ωm), and determines the rotational speed and / or momentum depending on the third signal value (ωp).SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for determining the rotational speed and / or the momentum derived from the rotational speed using a rotational speed sensor. The present invention also relates to a computer program product for implementing the above method when implemented on a computer device. Furthermore, the present invention relates to a data carrier provided with such a computer program product, and in particular to a computer device provided for implementing the above computer program product or the above method.

Background Art

[0002] Methods of the kind initially mentioned are known from the prior art. For example, this kind of method is used in a vehicle environment. That is, many functions implemented in an ABS / ESP controller use, as a main control variable, the difference between the circumferential speed of a vehicle wheel (ω·γ) and the speed (v Rad ) of the wheel center point of the wheel on the ground, or a variable based on speed, a so-called wheel slip. The circumferential speed of the wheel is typically determined by measuring the rotational speed using a rotational speed sensor. Similarly, methods are also known that aim to improve the accuracy when determining the vehicle speed using this kind of rotational speed sensor when the speed is low. For example, Patent Document 1 and Patent Document 2 each disclose a method for determining the vehicle speed by extrapolation during low-speed driving. In the latter disclosure, data of a plurality of vehicle wheels are merged.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

[0004] The method according to the invention having the constituent features of claim 1 extrapolates or interpolates a corrected third signal value at a selected reference point depending on the determined information age of a first signal value evaluated at a first evaluation point of a rotational speed sensor and a second signal value temporally preceding the first signal value, and determines a rotational speed and / or a momentum depending on the third signal value. The information age determines the actual validity point of the signal value that is temporally before the evaluation point, and particularly at low speeds, advantageously improves the accuracy in determining the actual signal value. In this regard, with respect to the usage example of determining the wheel circumferential speed of the vehicle wheels described at the beginning, since there is a certain delay between detection and evaluation in the present invention, if the vehicle decelerates, the actual wheel circumferential speed at the point in time when the selected signal value can be used is smaller than expected. Therefore, the method according to the invention avoids, or at least significantly reduces, systematic errors due to asynchronous signals when calculating wheel differential or wheel slip. In particular, in addition to the information age of the wheel circumferential speed, the information age of the speed of the wheel center point required to determine wheel slip is also considered. However, this consideration can be applied to any type of rotational speed measurement, that is, it can also be applied outside the vehicle environment. In order to at least reduce the errors generated in this way, according to the present invention, the information age is considered. That is, the point in time associated with the signal value is corrected to an earlier point in time, and the actual signal value is extrapolated or interpolated to the reference point. For this purpose, for example, a straight line is drawn between a preceding signal value (the validity point of which is known) and the signal value corrected in time now, and this straight line is extended to the evaluation point used as the reference point as far as possible. Particularly advantageous is that since there is usually always a delay between detection and evaluation (for example, due to the controller used), the method according to the invention can be used with the measurement pulses of a (magnetic) incremental encoder, but can also be used with any type of rotational speed sensor (such as an inductive type).

[0005] According to a further advantageous configuration of the invention, it is contemplated to determine the assumed validity time point of the first signal value from the difference between the first evaluation time point and the information age. By determining the validity time point, it is advantageous because it is ensured that if the signal value is used as a support point for extrapolation or interpolation, a correction time point is associated with the first signal value.

[0006] Particularly advantageously, it is contemplated to select the first evaluation time point as the reference time point. By selecting the evaluation time point, the advantage of performing extrapolation to a known time point is obtained. Thereby, an accurate signal value is associated with the evaluation time point.

[0007] According to a further advantageous configuration of the invention, it is contemplated to assess the information age depending on at least one parameter of the signal processing of the rotational speed sensor, in particular depending on the operating time of the incorporated signal filter and / or the signal transmission path. By considering this type of parameter, it is advantageous because it is ensured that the accuracy in assessing the information age is further improved.

[0008] Particularly advantageously, it is contemplated to assess the information age depending on at least one rotational speed-dependent parameter of the rotational speed sensor, in particular of an equiangular scan, and in particular depending on half of the time difference between the first signal value and the second signal value. By considering this type of parameter, it is advantageous because it is ensured that the accuracy in assessing the information age is further improved. In particular, this is considered in addition to the aforementioned parameters of the signal processing.

[0009] According to a further advantageous configuration of the invention, the information age is determined depending on at least one parameter of the control device used to evaluate the signal value, in particular depending on the expected value of the equal variance, depending on the determined measurement time, and / or depending on the measurement time determined in an equidistant evaluation raster using interval nesting to convert an equiangular scan into an equal-time evaluation by means of the control device. By taking into account this type of parameter, it is ensured that the accuracy in determining the information age is further improved, which is advantageous. In particular, this is taken into account in addition to the aforementioned parameters of the signal processing and / or the scan.

[0010] Particularly preferably, it is contemplated that the rotational speed sensor is formed in particular as a magnetic incremental encoder, and that as the signal value, the time interval between temporally adjacent measurement events of the incremental encoder, or a value derived therefrom, is used. In the case of this type of configuration of the rotational speed sensor, the advantages of the method according to the invention are particularly clearly evident. In particular, the incremental encoder has a plurality of sensor elements and one magnetic incremental encoder wheel. Preferably, as the measurement event, a predetermined signal value of one signal path is considered, in particular the zero crossing point of one signal path is considered, and / or the measurement event is determined depending on the signal paths of at least two sensor elements, in particular depending on the differential signal path of at least two of the plurality of sensor elements.

[0011] According to a further advantageous configuration of the invention, it is contemplated that the wheel peripheral speed is determined as the momentum. For example, the wheel peripheral speed of one wheel of a motor vehicle is particularly advantageously determined simply and accurately by the method according to the invention.

[0012] Particularly advantageously, extrapolation or interpolation is carried out linearly or using an n-th order polynomial, where n is an integer and > 1, and in particular it is contemplated to carry it out using a Savitzky-Golay-Filter. This is advantageous because the accuracy in implementing the method according to the invention is further improved.

[0013] A computer program product according to the invention for implementation on a computer device having the features of claim 10, when used as specified, is characterized in that it implements the method according to the invention. Thereby, the advantages already mentioned are obtained.

[0014] A data carrier according to the invention having the features of claim 11 is characterized in that a computer program product according to the invention is stored thereon.

[0015] A computer device having the features of claim 12 is characterized in that the computer device is provided, inter alia, for implementing the method according to the invention or for implementing a computer program product according to the invention. Also thereby, the advantages already mentioned above are obtained. Preferably, this computer device is a control device attached to a motor vehicle, in particular arranged inside the motor vehicle.

[0016] Further advantageous features and combinations of these features are apparent from the foregoing description and the claims. In the following, the invention will be explained in more detail with reference to the drawings.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Best Mode for Carrying Out the Invention

[0018] FIG. 1 shows a rotational speed sensor 1 known prior to the filing of the present application, such as one used to determine, for example, the wheel circumferential speed ω·r, where the wheel circumferential speed can be used as an input quantity for ABS control / ESP control as described at the beginning. The rotational speed sensor 1 detects the (measurement) events of an encoder or incremental encoder wheel 2 that rotates with the wheel, for example, detects a change in magnetic flux, and is formed to transmit to a computer device 3, which is a controller in this embodiment. On the other hand, the computer device 3 is formed to determine the time interval Δt(i) between the i-th event and the previous i-1-th event.

[0019] From the number of events N per rotation, the preset rolling radius r, and the measured time interval Δt, the computer device 3 determines the wheel circumferential speed ω m ·r = (2π·r) / N·1 / Δt. In principle, this is the average speed within the arc length s = (2π·r) / N between the said events.

[0020] For example, assuming that the wheel acceleration is constant, the determined wheel circumferential speed corresponds to the arithmetic mean value of the actual wheel circumferential speeds occurring for the two used events i and i-1. Therefore, in this case, the validity point of the speed information thus determined is exactly between the two events, but its availability point is at the detection point of event i.

[0021] Further delays typically occur between the availability time and the evaluation time based on a typical time synchronization evaluation of events within the controller, for example within an equidistant 5 - ms time raster. This delay can be represented as a probability variable evenly distributed within the corresponding interval, that is, for example, within the interval [0...5ms] (assuming a low speed with a maximum of one event per evaluation at least). If the speed is higher, multiple events occur per evaluation raster, and thus this evenly distributed interval is preferably shortened to the last event of note in the evaluation raster, even to a fraction.

[0022] At this time, the time difference between the evaluation time and the availability time is defined in this embodiment as the information age of the corresponding signal value of the event. Correspondingly, for the equiangular or equidistant scanning by the rotational speed sensor, the information age of the wheel circumferential speed has the two aforementioned speed - dependent components, that is, a deterministic component and a probabilistic component.

[0023] These basic relationships are illustrated in FIG. 2. For this reason, in FIG. 2, the relationships between the corresponding angular velocity ω and time t for event i and event i - 1 are plotted in the first angular acceleration - time graph. That is, for event i - 1, there is an angular velocity ω(i - 1) at time point t(i - 1), and for the next event (i) following with a time interval Δt(i), there is an angular velocity ω(i) at time point t(i).

[0024] However, what is measured (and evaluated) is, at this point, only the angular velocity ω associated with event i. m But in fact, this is valid at the availability time t before time point t(i). g and is evaluated at the evaluation time t after time point t(i). a and thus actually exists. In this regard, the difference Δ(t a - t g ) consisting of the availability time and the evaluation time corresponds to the information age T. i

[0025] Next, with reference to FIG. 3, an advantageous method for determining the rotational speed and / or the momentum derived from the rotational speed using a rotational speed sensor, in particular the aforementioned rotational speed sensor 1, will be described. For this purpose, FIG. 3 shows this method based on a flowchart. In particular, by this method, by taking into account the information age described above, it is guaranteed that at least a significant reduction in systematic errors when determining the corresponding quantity is achieved. The method is particularly implemented using the computer device 3.

[0026] In step S1, the method is started by detecting the first signal value of the rotational speed sensor and evaluating it at a first evaluation time point. At this time, the rotational speed sensor is preferably formed in particular as a magnetic incremental encoder, and in this case, as the signal value, the time interval between temporally adjacent measurement events of the incremental encoder or a value derived therefrom is used. As the momentum, in particular, as described above, the wheel peripheral speed, preferably the wheel center speed, and the wheel slip are also determined therefrom.

[0027] As described above, the corresponding signal value has a certain information age in any case. This information age is assessed in step S2. In particular, additionally, the corresponding information age of the signal values of other momenta, for example the wheel center speed, is assessed.

[0028] At this time, the wheel center speed, or, in other words, the speed v of the wheel center on the ground Rad undergoes different signal processing from the wheel peripheral speed ω·γ. That is, the wheel center speed is determined in the usual way by the conversion of the vehicle speed v from the vehicle center of gravity to each wheel center and the geometric projection in the wheel rolling direction. For the wheel center speed, it is typically assumed that the validity and the evaluation are simultaneous, and in particular, it is assumed that this is independent of the speed in the case where there is an information age. Fahrzeug Correspondingly, preferably, in particular, before calculating the wheel speed difference ω·γ - v

[0029] or the wheel slip, the measured wheel peripheral speed ω Rad m ​·The information age of γ and the wheel center speed v Rad The information age of Rad is evaluated, and the multiple speed signals used are considered in such a way that they are matched by subsequent extrapolation or interpolation. In this way, systematic errors in the resulting speed difference signal / wheel slip signal are avoided, especially when the wheel speed is low and there is wheel acceleration.

[0030] Starting with sensor detection of the corresponding physical quantities, each of these two signals under consideration passes through a signal processing channel until the point of common algorithmic evaluation, thereby reaching different information ages.

[0031] Wheel circumferential speed ω m ·In the case of γ, the information age consists, according to a specific example, of a speed-independent deterministic component caused by a signal filter, a speed-dependent deterministic component caused by equiangular scanning of an incremental encoder, and a speed-dependent probabilistic component. The speed-dependent probabilistic component occurs when the equiangular or equidistant incremental encoder scanning is converted to an equal-time evaluation in the controller with respect to the scanning speed.

[0032] Wheel center speed v Rad In the case of Rad , the information age is determined substantially by the group delay in the signal filter of the inertial sensor device on which the calculation of the vehicle speed depends, and should therefore be assumed to be deterministic, and in some cases should already be corrected and assumed to be particularly speed-independent.

[0033] Therefore, it is preferable to evaluate the information age depending on at least one parameter of the signal processing of the rotation speed sensor or the sensor device used each time, especially depending on the operating time of the incorporated signal filter and / or the signal transmission path. This speed-independent deterministic component of the information age results substantially directly from the specifications of the signal filter supported upstream, for example, a few milliseconds, typically 10 ms.

[0034] Alternatively or additionally, the information age is preferably determined as a function of at least one rotational speed-dependent parameter of the scanning of the rotational speed sensor, in particular of an equiangular scanning, and in particular as a function of half of the time difference between a first signal value and a second signal value temporally preceding the first signal value.

[0035] To determine the speed-dependent delay between the effectiveness and the availability of the wheel peripheral speed, it is preferably assumed that the wheel acceleration is constant between a plurality of events. At this time, for example, half of the measured time difference Δt / 2 between a plurality of events is assumed as the determined value for this component of the information age.

[0036] Alternatively or additionally, the information age is preferably determined as a function of at least one parameter of the control device used to evaluate the signal value, for example of the computer device 3, and in particular as a function of the measurement time determined as a function of the expected value of the equal variance, and / or as a function of the measurement time determined in an equidistant evaluation raster using interval nesting to convert the equiangular scanning into an equal-time evaluation by the control device.

[0037] Preferably, the speed-dependent probabilistic delay between the availability time and the evaluation time is measured. This succeeds when the controller determines the event time i using a continuous counter that functions as a clock. This is a normal case where it can also be read out at the evaluation time in the ABS / ESP controller. Therefore, the continuous counter is read out.

[0038] If the reading of the clock at the evaluation time is not set by the counter, it is preferable to use the expected value of the equal variance as the delay. Alternatively, at this time, assuming an equidistant evaluation raster, the evaluation deviation is further limited and determined using the event i probabilistically distributed therein and the interval nesting method.

[0039] If the information age is determined appropriately, then in step S3, depending on the determined information age of the first signal value of the rotation speed sensor and / or the determined information age of the corresponding signal value of another momentum, and also depending on a second signal value that temporally precedes the first signal value, one (or each one) corrected third signal value is extrapolated or interpolated at the selected (the same when considering the signal values of other momenta) reference time point.

[0040] Therefore, for each signal to be used, its final valid value is projected onto the evaluated value at the evaluation time point to be used in the next calculation by extrapolating / interpolating the immediately preceding signal path in consideration of its information age.

[0041] When this method is implemented for the first time, the signal value that temporally precedes is a value that has not been temporally corrected. This is because the information age could not be considered yet. As long as this is the case, the immediately preceding signal path required for extrapolation exists at the earliest after the second signal value, that is, in the third event.

[0042] In particular, the first evaluation time point is selected as each reference time point. Preferably, the extrapolation / interpolation is performed linearly or with an nth-order polynomial, where n is an integer and >1, and in particular, it is performed using a Savitzky-Golay filter. This is, therefore, in the first-mentioned case, in the form of a linear extrapolation of the final valid speed value, assuming a constant acceleration, for example, assuming the last evaluated acceleration, in consideration of the calculation cost in the controller, or in the second-mentioned case, by a higher-order polynomial extrapolation.

[0043] Figure 4 shows a corresponding example of this kind of linear extrapolation. Therein, the relationship between the corresponding angular velocity ω and time t for events i and i - 1 is plotted in a second angular acceleration - time graph. Therefore, as already pointed out and described with reference to Figure 2, the angular velocity ω associated with event i is used as the first signal value m is evaluated at the evaluation time point t a and this angular velocity is considered in its information age T IIn consideration, in this embodiment, it is projected onto the corresponding reference time point at the validity time point t g to project.

[0044] Now, the second signal value immediately preceding the angular velocity ω b is linked by a straight line to the first signal value corrected in time of the angular velocity ω m and this straight line is extended to the evaluation time point, and as a result, correspondingly, at the evaluation time point t a there exists a corrected third signal value of the angular velocity ω p .

[0045] In an alternative embodiment, the projection of the signal used can also be performed at a time point different from the evaluation time point, preferably an earlier time point, for example, also at the validity time point depending on the speed of the wheel peripheral speed. Thereby, it is preferable that the extrapolation time can be shortened, or interpolation can be performed instead of extrapolation, and as a result, the accuracy of the derived quantity can be improved thereafter.

[0046] Finally, in step S4, depending on the third signal value, or depending on the third signal value each time, the rotational speed and / or the momentum are determined, for example, as described above, the wheel slip is determined from the wheel peripheral speed and the wheel center speed. This method is preferably carried out continuously.

Explanation of Signs

[0047] 1 Rotational speed sensor 3 Control device T i Information age t a First evaluation time point t g Assumed validity time point of the first signal value ω m First signal value ω b Second signal value ω p Third signal value

Claims

1. 1. A method for determining a rotational speed and / or a momentum quantity derived from the rotational speed by means of a rotational speed sensor (1), comprising: the first evaluation time point (t ａ ) the first signal value (ω ｍ ) of the estimated information age (T I ) and the first signal value (ω ｍ A second signal value (ω) that precedes in time ｂ ) and the corrected third signal value (ω ｐ ) extrapolated or interpolated to a selected reference time point, - said third signal value (ω ｐ ) determining the number of rotations and / or the momentum in dependence on method.

2. The first evaluation time point (t ａ ) and the information age (T ｉ ) from the difference between the first signal value (ω ｍ ) at the expected time of effectiveness (t ｇ 2. The method of claim 1, further comprising determining

3. The first evaluation time point (t ａ 3. The method according to claim 1, further comprising the step of selecting:

4. The information age (T I 4. The method according to claim 1, further comprising: assessing the rotational speed of the rotational speed sensor (1) as a function of at least one parameter of the signal processing of the rotational speed sensor (1), in particular as a function of the operating time of an integrated signal filter and / or the signal transmission path.

5. The information age (T I 5. The method according to claim 1, further comprising: assessing the rotational speed of the rotational speed sensor (1) based on at least one rotational speed-dependent parameter, in particular of an equiangular scan, of the rotational speed sensor (1), in particular based on half the time difference between the first and second signal values.

6. The information age (T I 6. The method according to claim 1, further comprising: assessing the signal values ​​in dependence on at least one parameter of the control device (3) used for evaluating the signal values, in particular in dependence on a measurement time determined in dependence on an expectation value of equal variance and / or in dependence on a measurement time determined with an equidistant evaluation raster by means of interval nesting in order to convert an equiangular scan into an equal-time evaluation by the control device (3).

7. 7. The method according to claim 1, characterized in that the rotational speed sensor (1) is in particular designed as a magnetic incremental encoder and that the signal value used is the time interval between adjacent measurement events of the incremental encoder or a value derived therefrom.

8. 8. The method according to claim 1, further comprising determining the wheel peripheral speed as the momentum quantity.

9. 9. The method according to claim 1, wherein the extrapolation or interpolation is performed linearly or by means of a polynomial of degree n, where n is an integer and >1, in particular by means of a Savitsky-Golay filter.

10. 10. A computer program product for execution on a computing device, said computer program product performing a method according to any one of claims 1 to 9 when used as specified.

11. A data carrier comprising a computer program product according to claim 10.

12. A computer arrangement (3), in particular a control device, for a motor vehicle, characterized in that the computer arrangement (3) is arranged, inter alia, to implement a computer program product according to claim 10.

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