Method for ascertaining rotational speed and / or movement variable derived from rotational speed, computer program product, computer device

Abstract

To provide a method for ascertaining a rotational speed and / or a movement variable derived from a rotational speed, in particular wheel circumferential speed, using a rotational speed sensor (1) having a plurality of sensor elements (4) and an incremental generator wheel (2).SOLUTION: Time intervals between temporally adjacent measurement events of a rotational speed sensor (1) are ascertained, in particular continuously, wherein at least one estimated value for at least one duty cycle of a period including at least two of the measurement events, in particular a signal curve or a particular signal curve of the sensor elements (4), is ascertained depending on the ascertained time intervals. At least two of the time intervals are corrected depending on the estimated value, and the rotational speed and / or the movement variable are ascertained depending on the corrected time intervals.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, in particular the wheel circumferential speed, using a rotational speed sensor having a plurality of sensor elements and one incremental generator wheel. The present invention further relates to a computer program product for carrying out the above-described method when executed on a computer device. The present invention further relates to a computer device that is specially configured for carrying out the computer program product or the above-described method.

Background Art

[0002] Prior Art Methods of the type described at the beginning are known from the prior art. For example, such methods are used in the field of vehicles. Thus, many functions presented in an ABS / ESP control device require the wheel circumferential speed (ω·r) of the vehicle wheels as an input quantity. The wheel circumferential speed is typically determined by measuring the rotational speed using a rotational speed sensor. From German Patent Application Publication No. 102015213572, for example, there is known a method for operating such a rotational speed sensor, wherein the rotational speed sensor has a signal generator ring and a signal receiver, the signal generator ring has a plurality of magnet elements evenly distributed around the signal generator ring with alternating magnetic orientations, the signal receiver has a plurality of sensor elements for detecting the magnetic field of the magnet, generates information bits depending on the magnetic field strength detected by the sensor elements, and provides them as a rotational speed information signal. In order to increase the resolution of this rotational speed sensor, in particular, the output signals of three sensor elements of the rotational speed sensor are coupled to each other.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Means for Solving the Problem

[0004] Disclosure of the Invention The method according to the invention having the features described in claim 1 is characterized in that the time interval between temporally adjacent measurement events of a rotational speed sensor is specifically continuously determined, and depending on the determined time interval, at least one estimated value for at least one duty cycle of one period of at least two of a plurality of measurement events of one signal waveform or each signal waveform of a sensor element is specifically determined, at least two of the plurality of time intervals are corrected depending on the estimated value, and the rotational speed and / or momentum is specifically determined depending on the corrected time interval. Thereby, advantageously, the measurement accuracy of the rotational speed sensor is improved, and thereby, in particular as described at the beginning, the accuracy in detecting the wheel circumferential speed of a wheel of a motor vehicle is increased. The method can advantageously be used in the rotational speed sensor described at the beginning based on the detection of magnetic field strength, but is not limited thereto. Rather, the method can be used with any type of rotational speed sensor equipped with an increment generator. Preferably, the duty cycle is a value between 0 and 1 with respect to the length of the period and represents the relative and temporal position of a measurement event or measurement pulse within each period. In this case, to that extent, the present invention is based on the recognition that the duty cycle as the relative position of the measurement event actually deviates from its ideal value, in particular due to non-uniform sampling of the increment generator wheel, and the measurement accuracy is improved by taking into account the actual value of the duty cycle by the estimation according to the present invention. By the correction, the corrected time interval will correspond to the time interval of ideally uniform sampling of the increment generator wheel, in particular of one magnetic pole pair, and thereby, for example, systematic measurement errors in the wheel circumferential speed signal derived therefrom will be minimized. In particular, the estimated value is specifically continuously determined after a predetermined number of measurement events each. In particular, the measurement event is generated depending on at least one signal waveform of at least one of a plurality of sensor elements.In a specific example of a sine wave signal where a zero crossing of the signal waveform is detected as a measurement event, the estimated value has a target value of 1 / 2, where the "central" zero crossing is located with respect to one period of the sine wave signal, and the position of this zero crossing is thereby represented. Preferably, alternatively or additionally, the reciprocal of the difference is corrected, and the rotational speed and / or momentum are specified depending on the corrected reciprocal. In that case, the reciprocal is the frequency.

[0005] According to a preferred development of the invention, as a measurement event, a predetermined signal value of the signal waveform, in particular a zero crossing of the signal waveform, is considered. By considering the signal value, the measurement event is characterized particularly advantageously and simply. Preferably, when a predetermined signal value of each signal waveform is reached, at least one measurement event, in particular all measurement events, for example a zero crossing event, among the plurality of measurement events is generated.

[0006] Particularly preferably, the measurement event is specified depending on the signal waveforms of at least two of the plurality of sensor elements, in particular depending on the difference signal waveforms of at least two of the plurality of sensor elements. Thereby, the measurement event is specified particularly advantageously and robustly. For example, as a measurement event, a zero crossing of the corresponding signal waveform is considered.

[0007] According to a preferred development of the invention, at least one deviation value of the duty cycle from a predetermined ideal value and / or at least one reference value characterizing the duty cycle are specified depending on at least three consecutive time intervals, and the estimated value is specified depending on the deviation value and / or the reference value. By specifying and considering the deviation value and / or the reference value in this way, it is ensured that the estimated value is specified particularly advantageously and simply.

[0008] Particularly preferably, the specified deviation value or reference value is filtered using a discrete PT1 filter having a predetermined initial value and a predetermined amplification factor before the estimated value is specified. For filtering, in particular, at least one difference between two deviation values or reference values associated with consecutive time intervals is specified. By filtering the deviation value or reference value in this way, the advantage is obtained that the accuracy in specifying the estimated value is further improved.

[0009] According to a preferred development of the invention, at least one absolute value, in particular a plurality of absolute values, of the difference between two estimated values, deviation values, and / or reference values associated with consecutive time intervals is specified, and depending on one or more absolute values, it is specified whether the consecutive estimated values are converging. If convergence is identified, only then is the time interval corrected and / or the convergence rate is specified, and the time interval is weighted and corrected using the convergence rate. By specifying and taking into account the convergence, advantageously, it is ensured that the estimated value is specified robustly. If the estimated value is not converging, to that extent, in particular, the method is interrupted or the time interval is not corrected. Alternatively or additionally, in particular, a correction weighted using the convergence rate is carried out.

[0010] Particularly preferably, one absolute value, a plurality of absolute values, and / or the average value of a plurality of absolute values for identifying convergence is compared with a predetermined first threshold value, and in particular, when a predetermined number of absolute values or average values are below the threshold value, convergence is identified, and / or when at least one of the plurality of absolute values and / or average values exceeds a second predetermined threshold value higher than the first threshold value, and / or when at least one of the plurality of time intervals reaches at least a third predetermined threshold value, in particular when exceeding the third predetermined threshold value, the identified convergence is discarded. Thereby, the advantage is obtained that the actual convergence is correctly identified.

[0011] According to a preferred development of the invention, at least two signal waveforms are generated from the sensor signals of at least two sensor elements of each rotation speed sensor, in particular calculated to be different from each other, and consecutive measurement events are each associated with a different signal waveform, and for each of the signal waveforms, an estimated value for one duty cycle is determined respectively. Advantageously, this ensures that the signal waveforms are reliably distinguished from each other and that only estimated values that can be associated with the respective signal waveforms are determined.

[0012] Particularly preferably, at least one estimated value for at least one relative shift between two consecutive measurement events associated with different signal waveforms is determined, and depending on the estimated value, the time interval is corrected. By taking into account the shift estimated value, the advantage is obtained that the accuracy in correcting the time interval is further improved. The shift estimated value is, to that extent, further determined in addition to the duty cycle estimated value and is taken into account during the correction.

[0013] According to a preferred development of the invention, for each duty cycle, one convergence rate and / or deviation value from a predetermined ideal value for the estimated value are determined, and depending on the determined convergence rate and / or deviation value, one duty cycle is associated with one of at least two different signal waveforms respectively. Advantageously, this ensures that the corresponding estimated value and, thus, the underlying measurement event are correctly classified, i.e., associated with the correct signal waveform.

[0014] Particularly preferably, in particular by exchanging the estimated values, the duty cycle associated with the estimated value having a higher convergence rate and / or a smaller deviation value is associated with the first signal waveform, and the other duty cycle is associated with the second signal waveform respectively. This ensures that the estimated value and the underlying measurement event are particularly easily classified.

[0015] According to a preferred development of the invention, a measurement event associated with one of a plurality of signal waveforms is discarded if at least one of a plurality of time intervals falls below a fourth predetermined threshold. Advantageously, this ensures that, for example, a corresponding measurement event is ignored when a predetermined vehicle speed is exceeded, and at the same time the required measurement accuracy is guaranteed, thereby reducing the computational cost of the method when the predetermined threshold is exceeded.

[0016] Particularly preferably, the increment generator wheel is configured magnetically, and at least three sensor elements, in particular Hall sensors or magnetoresistive sensors, are arranged equidistantly in a row. As a first signal waveform, the difference between the sensor signals of two sensor elements, in particular two outer sensor elements, is generated. As a second signal waveform, the difference between one of the sensor signals of one of the plurality of sensor elements, in particular the central sensor element, and the average value of the sensor signals of two other sensor elements of the plurality of sensor elements, in particular two outer sensor elements, is generated. Thereby, the advantage is obtained that the accuracy in determining the momentum is further improved. In this regard, a virtual additional signal is generated between two measurement events. In particular, as corresponding signal values, one zero-crossing event each of a periodic signal waveform corresponding to the arc length of the magnetic pole pair, in particular the magnetic flux density, is assumed. For example, Hall sensor elements are used, and as measurement events, zero-crossings of the waveforms of the magnetic flux density of the sensor elements, that is, two zero-crossings per magnetic pole pair, are output. Then, in order to improve the accuracy, a so-called virtual and additional measurement event based on the difference signal of the Hall sensor elements is generated.

[0017] A computer program product according to the invention for execution on a computer device, having the features of claim 14, is characterized in that it implements the method according to the invention when used as prescribed. Thereby, the advantages described above are obtained. Preferably, a data carrier on which the computer program product according to the invention is stored is envisaged.

[0018] The computer device having the features according to claim 15 is characterized in that it is specially configured for implementing the method according to the present invention or for executing the computer program product according to the present invention. Also thereby, the advantages described above can be obtained. Preferably, the computer device is a control device associated with a motor vehicle, in particular arranged in a motor vehicle.

[0019] Further preferred features and combinations of features will become apparent from the above description and the claims. In the following, the present invention will be described in more detail based on the drawings.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0021] FIG. 1 shows a known rotational speed sensor 1 such as used for specifying, for example, the wheel peripheral speed ω·r, in which case this wheel peripheral speed ω·r can be used as an input quantity for ABS / ESP control as described at the beginning. The rotational speed sensor 1 is configured to detect (measurement) events, for example magnetic flux changes, of an encoder or an incremental generator wheel 2 rotating with the wheel and transmit them to a computer device 3, which in this embodiment is a control device. The computer device 3 itself is configured to specify the time interval Δt(i) between the i-th event and the preceding i−1-th event, in particular using a high-frequency counter (typically 10 MHz), and to estimate the current wheel rotational speed and the wheel peripheral speed derived from the wheel rotational speed depending on this time interval Δt(i).

[0022] Generally, a magnetic multi-pole wheel is used as the encoder or incremental generator wheel 2. In this case, the incremental generator utilizes a plurality of sensor elements 4, specifically, three sensor elements 4 arranged at equal intervals in a row (shown in the vertical direction in FIG. 1) in this embodiment. The sensor elements 4 are configured as Hall generators, AMR sensors, GMR sensors, and / or TMR sensors, and are configured to detect the magnetic field emerging from the incremental generator wheel 2, for example, in the tangential direction, and output a respective measured quantity, such as a Hall voltage, that depends on this magnetic field.

[0023] Correspondingly, measurement events transmitted to the computer device 3 are derived from the measured quantities of the sensor elements 4. For example, a signal zero crossing of the magnetic flux density is used as the measurement event. Thus, when the wheel moves, exactly two events are implemented for each magnetic pole pair having an arc length D of the incremental generator wheel 2. In this case, generally, in order to reduce the offset error of the zero position caused by, for example, temperature effects, the difference signal of the signals of two outer sensor elements 4, referred to as A and B in this embodiment (corresponding to the lower and upper sensor elements 4 in FIG. 1) among the plurality of sensor elements 4, is considered as the first signal waveform. The signal of the central sensor element 4, referred to as M in this embodiment (corresponding to the central sensor element 4 in FIG. 1), is used, for example, to identify the direction of rotation.

[0024] Ideally, each magnetic pole inside the magnetic pole pair has the same length, and the zero position of the difference signal also has no offset error. In that case, each event occurs with a spatial interval of D / 2 from each other. In reality, the relative position between the events, referred to as the duty cycle α, typically deviates from the ideal value of 1 / 2 by ±5% (i.e., the duty cycle is a value between 0 and 1).

[0025] In the case of the ideal incremental generator wheel 2, each magnetic pole pair has the same arc length D, that is, all magnetic pole pairs are uniformly distributed over the circumference of the encoder. In practice, pitch errors occur due to manufacturing, and such pitch errors typically are up to ±5% at most here as well. The periodically repeating pattern that results therefrom in the radial direction is learned and compensated for, in particular, by evaluating the event sequence inside the computer device 3, and the corresponding method is described, for example, in “Increasing signal accuracy of automotive wheel - speed sensors by on - line learning”, R. Schwarz, O. Nelles, P. Scheerer, and R. Isermann in American Control Conference, Albuquerque, New Mexico, 1997. Such possible mutual non - uniformity (pitch errors) of the magnetic pole pairs of the encoder wheel is preferably considered not to exist or to be sufficiently compensated for in the method described further below.

[0026] In particular, in recent developments in the field of parking automation, a higher resolution is required in the sense of an increase in the number of events per wheel rotation. In this case, an encoder wheel with significantly more magnetic pole pairs is not a good solution for technical and economic reasons. However, it is possible to increase the number of measurement events per magnetic pole pair, for example, by considering additional signal waveforms of the individual signals that are calculated with each other. In particular, the additional second signal waveform is derived from the zero - crossing of the difference signal of the central sensor element M and the signal average value of the two outer sensor elements A and B.

[0027] Here, the relative positions of four events per magnetic pole pair can be described using three independent quantities. In the following, for the sake of explanation, the existing duty cycle α (ideal value 1 / 2) of the measurement event of the first signal waveform, the duty cycle β (ideal value 1 / 2) of the measurement event of the second signal waveform, and the relative shift γ (ideal value 1 / 4) of the measurement events as the mutual shift between these signal waveforms are utilized. This is not intended to limit the present invention, and independent quantities selected by other methods can always be converted into these three selected quantities.

[0028] Generally, the statistical characteristics of the measurement event of the second signal waveform as the intermediate event deviate from the statistical characteristics of the measurement event of the first signal waveform as the standard event. For example, due to different combinations of measured quantities, the amplitude of the difference signal M - (A + B) / 2, which depends on the ratio of the sensor element interval d and the arc length D shown in FIG. 2, typically becomes smaller. Therefore, when locating the corresponding measurement event in time, for example, the sensitivity to the offset error at the zero position and / or the sensitivity to the tilt of the incremental generator with the sensor element 4 in the magnetic field of the incremental generator wheel 2 as the encoder is increased.

[0029] This appears in the form that the variation of β is larger than that of α in the measurement. (Obtained as a result of the spatial and temporal sampling of the magnetic field, where the spatial component is important) The accuracy of the geometric center position of the sensor element M also affects the duty cycle value β of the intermediate event.

[0030] These basic relationships are shown in FIG. 2. In FIG. 2 regarding this, the portion in the incremental generator wheel 2 as an encoder where the N poles N and the S poles S are alternately arranged is projected. Each one of these magnetic pole pairs has an arc length D. Below that, an exemplary waveform of the magnetic flux density B in the remote field of the encoder at three sensor elements A, M, and B when the encoder moves towards the right is plotted with respect to the encoder rotation angle φ in the corresponding diagram. In a further corresponding diagram, the utilized difference signals A - B and M - (A + B) / 2 described above are plotted with respect to the rotation angle φ. Each arc length D includes one corresponding period of the corresponding signal and thus two zero-crossing events for each of the signal waveforms.

[0031] In the following, a advantageous method for identifying the rotational speed and / or the momentum derived from the rotational speed, in particular using the rotational speed sensor 1 described above, will be described with reference to FIG. 3. In this regard, FIG. 3 shows this method based on a flowchart. In particular, according to this method, by taking into account the above-described deviation between the duty cycle and the corresponding ideal value of the duty cycle, it is guaranteed that the accuracy in identifying the corresponding quantity is improved. This method is particularly implemented using the computer device 3.

[0032] In step S1, the method is started by specifically and continuously determining the corresponding time intervals between temporally adjacent measurement events of the rotation speed sensor. As the measurement event, preferably a predetermined signal value of the signal waveform, particularly the zero crossing of the signal waveform, is considered. Particularly preferably, the measurement event is determined depending on the signal waveforms of at least two of the plurality of sensor elements, particularly depending on the difference signal waveform of at least two of the plurality of sensor elements. For example, the zero crossings of the two signal waveforms obtained from the correspondingly combined difference signals of sensor element 4, which were described with reference to FIGS. 1 and 2, are considered. However, in the case of the method according to the present invention, generally, it is sufficient to appropriately consider only one signal waveform, for example, only the first signal waveform as the difference signal between sensor elements A and B.

[0033] For example, at least three sensor elements, particularly Hall sensors or magnetoresistive sensors, are arranged equidistantly in a row as described in FIGS. 1 and 2. In this case, as the first signal waveform, the difference between the sensor signals of two sensor elements, particularly the two outer sensor elements, is generated, and as the second signal waveform, the difference between one of the sensor signals of one of the plurality of sensor elements, particularly the central sensor element, and the average value of the sensor signals of two other sensor elements of the plurality of sensor elements, particularly the two outer sensor elements, is generated. In this case, particularly, but not necessarily, the incremental generator wheel is configured magnetically. Therefore, the method can advantageously also be used in the case of optical sensing or in the case of other types of event transmission or measurement.

[0034] In the subsequent step S2, depending on the determined time interval, at least one estimated value for at least one duty cycle of one period including at least two of the plurality of measurement events of one signal waveform or each signal waveform of the sensor element is determined.

[0035] Referring to FIGS. 1 and 2, then, for example, from the measured time intervals of all measurement events identified by a rotational speed sensor, the relative positions of those measurement events inside the pole pair are estimated in the form of duty cycles α and β and a relative shift γ, and based on these, as will be described in detail below, the corresponding measurement events are classified based on the duty cycle estimates and their convergence rates, that is, they are associated with their respective signal waveforms.

[0036] FIG. 4 shows a corresponding example with respect to the rotational speed sensor 1 described above having three sensor elements 4. In this regard, FIG. 4 shows a first signal waveform and a second signal waveform plotted over a relatively wide range of the rotation angle φ, and thus, out of four different events per arc length D, two similar measurement events (of two consecutive arc lengths D or periods) are shown, and these measurement events, to that extent, are spaced D 1 , D 2 , D 3 , D 4 from each other. Further, here too, the duty cycle α of the measurement events of the first signal waveform as described above, the duty cycle β of the measurement events of the second signal waveform, and the relative shift γ are shown.

[0037] In the specific embodiment described with reference to FIGS. 1, 2, and 4, from the continuous sequence of the time intervals Δt(i) measured between measurement events, the relative positions of the events inside the arc length D of the pole pair are estimated. In this case, in the case where the resolution is doubled, that is, considering the second signal waveform, it is assumed that each pole pair is always characterized by four adjacent time intervals, that is, in particular, it is assumed that neither an excessive number of measurement events nor an excessive lack of measurement events are detected.

[0038] Preferably, for this purpose, at least one deviation value of the duty cycle from a predetermined ideal value and / or at least one reference value characterizing the duty cycle are determined depending on at least three consecutive time intervals, and an estimated value is determined depending on the deviation value and / or the reference value.

[0039] In the simplest case, only one signal waveform, for example, only the first signal waveform (A - B) in FIG. 2, is considered. In that case, in particular (first aspect), the duty cycle value

Number

Number

Number

[0040] Alternatively, first, the deviation from the ideal value

Number

Number

[0041] Subsequently, depending on this, the estimated value

Number

Number

[0042] Preferably, as described above, at least two signal waveforms from sensor signals calculated such that each of at least two sensor elements of the rotational speed sensor, particularly different from each other, are generated, consecutive measurement events are associated with different signal waveforms, and for each of the signal waveforms, an estimated value for one duty cycle is specified. In this case, preferably additionally, at least one estimated value for at least one relative shift between two consecutive measurement events associated with different signal waveforms is specified.

[0043] In a specific embodiment, particularly (first aspect), the duty cycle

Number

Number

Number

Number

Number

[0044] The corresponding procedure can be generalized accordingly to further increase the resolution. For example, particularly when eight events per arc length of one magnetic pole pair are assumed, four duty cycle values

Number

Number

[0045] Returning to the specific embodiments, in an alternative expression, first, the deviation from each ideal value [Number] is estimated (similarly, for example, it is also possible to generalize to the eight events described above): [Number]

[0046] Subsequently, depending on this, the estimated value [Number] is specified: [Number]

[0047] In particular, the specified deviation value or reference value is filtered using a discrete PT1 filter having a predetermined initialization value and a predetermined amplification factor before the estimated value is specified. For filtering, in particular, at least one difference between two deviation values or reference values associated with consecutive time intervals is specified.

[0048] In the simplest case, here too, only one signal waveform, for example, only the first signal waveform (A - B) in FIG. 2, is considered. In that case, preferably (second aspect), the deviation from the ideal value is, in particular, the initialization value [Number] filtered in the form of a discrete PT1 filter with a time constant τ and an amplification factor k (for example, k = 3%):

Number

[0049] In a specific embodiment, particularly (second aspect), for two signal waveforms, the deviation from the ideal value is particularly the initialization value

Number

Number

[0050] The advantageously enhanced estimation quality, particularly when the time interval measured as a result of the speed change varies, is provided by a further preferred calculation rule (third aspect), in which the reference value in the denominator is divided in half between the measured duration of the pole and two pole pairs formed by the poles preceding or following this pole, and based on this, the corresponding filtering is carried out.

[0051] In the simplest case, here too, only one signal waveform, for example, only the first signal waveform (A - B) in FIG. 2, is considered. It is as follows:

Number

[0052] In the case of a specific embodiment where two signal waveforms are considered, it is as follows (similarly, it is possible to generalize to, for example, the eight events described above):

Number

[0053] Particularly preferably, for each duty cycle, one convergence rate and / or deviation value from a predetermined ideal value with respect to the estimated value are specified, and one duty cycle is associated with one of at least two different signal waveforms depending on the specified convergence rate and / or deviation value. In particular, particularly by exchanging the estimated value, the duty cycle associated with the estimated value having a higher convergence rate and / or a smaller deviation value is associated with the first signal waveform, and each other duty cycle is associated with the second signal waveform.

[0054] For example, when the type of event is not known in a specific embodiment, associating the estimated duty cycle with the waveform is initially random. Here, for example, if the number of those below the threshold for identifying convergence is more than twice, one of the two duty cycle estimated values

Number

Number

[0055] Alternatively or additionally, the duty cycle estimated value closer to the ideal value of 1 / 2

Number

Number

[0056] It has been found that the initial random association of the estimated duty cycle to the event type during classification is incorrect (

Number

Number

[0057] Even when the event type is known, performing the corresponding classification based on statistical signal characteristics is still advantageous for validity checking and / or monitoring. The classification can similarly be applied and generalized to, for example, the eight events described above.

[0058] In particular, a measurement event associated with one of a plurality of signal waveforms is discarded if at least one of a plurality of time intervals is below a fourth predetermined threshold. Thus, in particular, the calculation of the momentum can be performed based only on the measurement events classified as such of the first signal waveform without explicitly using the measurement events of the second signal waveform. Advantageously, this reduces the calculation cost and / or signal noise in the calculated output signal.

[0059] Preferably, when the rotational speed sensor is used in an automobile wheel, for example, in the case of a very large time interval such as close to the stopped state of the wheel, the estimation is interrupted, thereby avoiding a special case of a reversal of the rotational direction where the assumption of four measurement events per magnetic pole pair may not apply in some cases. In particular, for example, for the purpose of temporarily reducing the computational load, or when a deterioration of the convergence condition is expected, such as in the case of a rapid speed change during use in an automobile or driving on an unpaved road, a provisional suspension of the estimation is carried out.

[0060] After the estimation is interrupted, particularly when close to the stopped state of the wheel as described above, in order to achieve a faster convergence of the estimated value in the case of a reversal of the rotational direction, preferably re-initialization is carried out.

[0061] Here, in step S3, depending on one or more estimated values, at least two of the plurality of time intervals are corrected, whereby the corrected time intervals will correspond to the ideally uniform sampling time intervals of the increment generator wheel related to one magnetic pole pair in FIGS. 1 and 2, and the systematic measurement error in the wheel peripheral speed signal derived therefrom will be minimized.

[0062] In the simplest case, here too, only one signal waveform, for example, only the first signal waveform (A - B) in FIG. 2, is considered. In that case, particularly the estimated value

Number

Number

Number

[0063] In a specific embodiment, similarly, the estimated value

Number

Number

[0064] In an alternative approximation when the deviation from the ideal value is sufficiently small, it is also possible to apply the correction only after the reciprocal of the time difference is formed, so that for subsequent speed estimation when only one signal waveform is considered, the following corrected pulse frequency sequence is used:

Number

[0065] Similarly, in a specific embodiment when two signal waveforms are considered, the following corrected pulse frequency sequence is used:

Number

[0066] Regarding the determination of momentum, especially the wheel rotation speed or the wheel peripheral speed, the advantage of a high-resolution increment generator is substantially limited to low rotation speeds. Due to the principle of the increment generator, the information sharpness of the rotation speed signal (the effective time point between two events and the time interval until it becomes available after the second event) increases inversely as the rotation speed decreases.

[0067] Doubling the assumed resolution in a specific embodiment halves the information sharpness of the rotational speed signal. This is important, for example, in rotational speed ranges where there is less than one event per 5 ms. The relative error, such as the still un-converged and thus un-corrected duty cycle of the second signal waveform (in the case of low rotational speeds), also has only a minor impact on the absolute accuracy of the rotational speed estimation.

[0068] For rotational speeds above this range, the halving of the information sharpness is negligible, and here, the possible accuracy drawbacks of the intermediate pulses as measurement events of the second signal waveform and the drawbacks of the computational cost that increases linearly with the number of events are more dominant.

[0069] Therefore, preferably, the estimation of the momentum is carried out without explicitly using the intermediate pulses classified as such in the case of relatively high rotational speeds as described above, that is, only for each second event and by accumulating the time differences measured over the intermediate pulses, it is carried out using the following alternative pulse frequency sequence:

Number

[0070] Particularly preferably, at least one absolute value of the difference between two estimated values, deviation values, and / or reference values associated with consecutive time intervals, in particular a plurality of absolute values, is further specified in advance. In particular, in that case, depending on one or more absolute values, it is specified whether the consecutive estimated values are converging, and the time interval is corrected only when convergence is identified. Alternatively or additionally, a convergence rate is specified and the time interval is weighted and corrected using the convergence rate.

[0071] In this case, preferably, one absolute value, a plurality of absolute values, and / or the average value of a plurality of absolute values for identifying convergence are compared with a predetermined first threshold value, and in particular, when a predetermined number of absolute values or the average value is below the threshold value, convergence is identified.

[0072] Alternatively or additionally, if at least one of a plurality of absolute values and / or average values exceeds a second predetermined threshold that is higher than a first threshold, and / or if at least one of a plurality of time intervals reaches at least a third predetermined threshold, particularly if it exceeds the third predetermined threshold, the identified convergence is discarded.

[0073] In the simplest case, here too, only one signal waveform, for example only the first signal waveform (A - B) in FIG. 2, is considered. In that case, particularly the estimated value change

Number

Number

[0074] In a specific embodiment where two signal waveforms are considered, particularly the estimated value change

Number

Number

[0075] As an embodiment with particularly low computational cost, preferably, each absolute value is compared with a threshold of, for example, 0.1%, and if it continuously falls below this threshold over, for example, 100 multi-pole magnets n, convergence is identified. Alternatively, for example, an average / filtering of the absolute values and a corresponding threshold comparison of the average values are assumed.

[0076] Preferably, the correction of the measured time interval is performed only using the converged estimated value as described above. Alternatively, it is assumed that the convergence rate is used for weighting and correction. The identified convergence is, also here in particular, discarded if the absolute value exceeds a second, higher threshold, for example 0.5%, e.g., if there is a large time difference (close to a stop state), or, e.g., due to an increase in signal noise when driving on an unpaved road.

[0077] Finally, in step S4, depending on the corrected time interval, the rotational speed and / or the momentum, e.g., the wheel peripheral speed, is determined as described above. Preferably, the method is carried out continuously.

[0078] In particular, for the determination, in addition to the correction of the duty cycle, further signal processing steps are carried out, such as, for example, the formation of the reciprocal, the correction of the pitch error, anti-aliasing filtering, the conversion of the sampling rate, the consideration of the number of multipole magnets per encoder and the wheel circumference. Preferably, first, the correction of the duty cycle according to the invention is carried out in combination with the formation of the reciprocal, and for all subsequent steps, preferably one of the pulse frequency sequences described above is used.

Claims

1. A method for determining the rotation speed and / or a momentum quantity derived therefrom, in particular the wheel peripheral speed, by means of a rotation speed sensor (1) having a number of sensor elements (4) and an increment generator wheel (2), comprising: the time intervals between adjacent measurement events of the rotation speed sensor (1) are determined, in particular continuously, at least one estimate for at least one duty cycle of a period in which at least two of the measurement events are included, in particular of the or each signal waveform of the sensor element (4), depending on the determined time interval; [0010] was identified, The estimated value [0025] at least two of the plurality of time intervals are corrected in dependence on A method in which the rotation speed and / or the momentum are determined depending on the corrected time interval.

2. As measurement events, certain signal values ​​of the signal waveform are considered, in particular zero crossings of the signal waveform. The method of claim 1.

3. a measurement event is determined depending on the signal waveforms of at least two sensor elements (4) of the plurality of sensor elements (4), in particular depending on a difference signal waveform of at least two sensor elements (4) of the plurality of sensor elements (4); The method according to claim 1 or 2.

4. at least one deviation of said duty cycle from a predetermined ideal value; [0030] and / or at least one reference value characterizing the duty cycle is determined in dependence on at least three consecutive time intervals, The deviation value [0045] and / or the estimated value in dependence on the reference value. [0050] is identified, 4. The method according to any one of claims 1 to 3.

5. The identified deviation value [006] Or the reference value is the estimated value [0070] is filtered using a discrete PT1 filter, in particular with a predetermined initialization value and a predetermined amplification factor, before being determined; For the filtering, two deviation values, which are in particular associated with successive time intervals, are used. [0080] or at least one difference in the reference value is identified; The method according to claim 4.

6. Two estimates associated with successive time intervals [0097] , standard deviation [0089] and / or at least one absolute value, in particular a number of absolute values, of the difference between the reference values ​​are determined, Successive estimates depending on said one or more absolute values. ##EQU00011## It is determined whether or not and / or the time interval is corrected only if convergence is identified; A convergence rate is determined, and the time interval is weighted and corrected using the convergence rate.

6. The method according to any one of claims 1 to 5.

7. comparing the absolute value, the plurality of absolute values, and / or an average of the plurality of absolute values ​​to a first predetermined threshold value to identify convergence; Convergence is identified, in particular when a predetermined number of absolute or average values ​​are below a threshold value; and / or the identified convergence is discarded if at least one of said plurality of absolute and / or average values ​​is above a second predetermined threshold value which is higher than said first threshold value and / or if at least one of said plurality of time intervals reaches at least a third predetermined threshold value, in particular if it is above a third predetermined threshold value; The method according to claim 6.

8. At least two signal waveforms are generated from the sensor signals of at least two sensor elements (4) of the rotational speed sensor (1), which are calculated in particular to be different from one another, Each successive measurement event corresponds to a different signal waveform. For each of the signal waveforms, an estimate for a respective one of the duty cycles ##EQU00012## is identified, 8. The method according to any one of claims 1 to 7.

9. At least one estimate for at least one relative offset between two measurement events associated with successive, respectively different, signal waveforms. ##EQU00013## was identified, The estimated value ##EQU00014## The time interval is corrected depending on 9. The method according to any one of claims 1 to 8.

10. The estimated value ##EQU00015## The convergence rate and / or deviation value of each of the duty cycles from a predetermined ideal value for ##EQU00016## was identified, The convergence rate and / or the deviation value determined ##EQU00017## Each duty cycle is associated with one of at least two different signal waveforms depending on 10. The method according to any one of claims 1 to 9.

11. In particular, the estimated [0018] By replacing [0019] The estimate with [0020] is associated with a first signal waveform, and the other duty cycle is associated with a second signal waveform; The method of claim 10.

12. a measurement event associated with one of the plurality of signal waveforms is discarded if at least one of the plurality of time intervals is below a fourth predetermined threshold.

12. The method according to any one of claims 1 to 11.

13. The increment generator wheel is configured to be magnetic; At least three sensor elements (4), in particular Hall sensors or magnetoresistive sensors, are arranged equidistantly in a row, A difference between the sensor signals of the two sensor elements (4), in particular the two outer sensor elements (4), is generated as a first signal waveform, a difference between one of the sensor signals of one of the plurality of sensor elements (4), in particular the central sensor element (4), and an average value of the sensor signals of two other sensor elements (4), in particular the two outer sensor elements (4), of the plurality of sensor elements (4) is generated as a second signal waveform; 13. The method according to any one of claims 1 to 12.

14. A computer program product for execution on a computing device (3), comprising: The computer program product, when used as specified, performs the method of any one of claims 1 to 13. A computer program product comprising:

15. A computer device (3), in particular a control device for a motor vehicle, comprising: The computer device (3) is specially configured to execute a computer program product according to claim 14. A computer device (3).

Images