Method for determining erroneous pulse signal in speed measurement of vehicle

Abstract

The invention relates to a method for ascertaining an erroneous pulse signal in a speed measurement of a vehicle, in particular a monorail vehicle, such as an electric bicycle, having a pulse-based speed sensor on a wheel, comprising the following steps: detecting a first, a second, a third and a fourth pulse signal by means of the pulse-based speed sensor, a first difference between the time of the second pulse signal and the time of the first pulse signal is determined, a second difference between the time of the third pulse signal and the time of the second pulse signal is determined, and a third difference between the time of the fourth pulse signal and the time of the third pulse signal is determined, based on a comparison of the at least one first difference and / or the second difference with at least one first threshold value. It is ascertained whether the third pulse signal is detected too early or too late, and the type of the third pulse signal is ascertained on the basis of at least one third difference and a comparison of the second difference with at least one second threshold value.

Description

Field of the Invention

[0001] The present invention relates to a method for obtaining an incorrect pulse signal in the speed measurement of a vehicle, in particular a monorail vehicle such as an electric bicycle.

[0002] The present invention also relates to a vehicle, in particular a monorail vehicle such as an electric bicycle, which has a pulse-based speed sensor on a wheel, wherein the vehicle is configured to obtain an incorrect pulse signal in the speed measurement of the vehicle.

[0003] Although generally applicable to vehicles, the present invention will be described based on an electric bicycle. Background Art

[0004] For vehicles, in particular monorail vehicles such as electric bicycles, it is known to measure the speed of the vehicle by means of a magnetic field sensor. For this purpose, a permanent magnet is fixed on the rear wheel. When riding, the wheel rotates, causing the magnet to rotate past the magnetic field sensor on the bicycle at regular intervals. The sensor can detect the passage of the magnet and output a pulse signal. Based on the wheel circumference and the time deviation between two pulses, the speed of the electric bicycle can be calculated.

[0005] During riding, magnetic interference from iron bridges, utility poles, or the electric drive unit of the bicycle may affect the detection device, resulting in additional incorrect pulses being measured, or the correct or valid pulses not being detected. This may cause the speed sensor to measure an incorrect speed.

[0006] In particular, an electric bicycle requires a persistent and accurate speed sensor because the drive assistance of an electric bicycle depends on the current speed. Summary of the Invention

[0007] In one embodiment, the present invention provides a method for obtaining an incorrect pulse signal in the speed measurement of a vehicle, in particular a monorail vehicle such as an electric bicycle, wherein the vehicle has a pulse-based speed sensor on a wheel, and the method includes the following steps:

[0008] Detecting first, second, third, and fourth pulse signals by means of the pulse-based speed sensor,

[0009] Determining a first difference between the time points of the second pulse signal and the first pulse signal, determining a second difference between the time points of the third pulse signal and the second pulse signal, and determining a third difference between the time points of the fourth pulse signal and the third pulse signal,

[0010] Based on at least one comparison of the first difference and / or the second difference with at least one first threshold, obtaining whether the third pulse signal is recognized too early or too late,

[0011] Based on at least one comparison of the third difference and the second difference with at least one second threshold value, the type of the third pulse signal is obtained.

[0012] In one embodiment, the present invention provides a vehicle, in particular a monorail vehicle, such as an electric bicycle, which has a pulse-based speed sensor on the wheel, and the vehicle is configured to obtain an incorrect pulse signal in the speed measurement of the vehicle, including:

[0013] A detection unit for detecting first, second, third, and fourth pulse signals by means of a pulse-based speed sensor,

[0014] A determination device configured to determine a first difference in the time points between the second pulse signal and the first pulse signal, determine a second difference in the time points between the third pulse signal and the second pulse signal, and determine a third difference in the time points between the fourth pulse signal and the third pulse signal,

[0015] A first obtaining unit configured to obtain whether the third pulse signal is recognized too early or too late based on at least one comparison of the first difference and / or the second difference with at least one first threshold value,

[0016] A second obtaining unit configured to obtain the type of the incorrect third pulse signal based on at least one comparison of the third difference and the second difference with at least one second threshold value.

[0017] One of the advantages achieved thereby is that it is possible to simply identify whether a pulse signal is incorrect. Incorrect pulse signals are in particular delayed or advanced pulse signals, or missing or additional pulse signals. Other advantages are that it is possible to obtain the type of the incorrect pulse signal, for example an early pulse signal or a missing pulse signal.

[0018] The term "type (Typ)" should be understood in a broad sense, particularly preferably in the claims and in the description, and refers to the category (Kategorie) of the pulse signal, which category describes the reason for the incorrect pulse signal. For example, the type may be an early pulse signal caused by an actual acceleration, or a pulse signal caused by an additional pulse.

[0019] Other features, advantages and further embodiments of the present invention will be described or revealed hereinafter.

[0020] According to an advantageous expansion scheme of the present invention, the vehicle has other speed sensors for obtaining an alternative speed. These other speed sensors can estimate the current speed based on the vehicle acceleration or measure the current speed based on a GPS system. One advantage of this is that the speed can be measured redundantly.

[0021] According to other advantageous developments of the invention, when the third pulse signal is recognized too early or too late, an alternative speed is used for speed measurement. If the pulse signal is determined too early or too late, it means that the vehicle may have an actual speed different from the speed measured by the pulse-based speed sensor. In this case, the alternative speed is switched to improve the accuracy of speed measurement.

[0022] According to other advantageous developments of the invention, the period during which the alternative speed is used for speed measurement is determined based on the type of the obtained pulse signal. Depending on the different types of pulse signals, the length of time during which the pulse-based speed sensor measures an incorrect speed signal varies. For example, for missing pulses, the pulse-based speed sensor will measure the correct speed again after two subsequent pulses. The advantage of this is that the alternative speed only needs to be used for a short period.

[0023] According to other advantageous developments of the invention, when two pulse signals (preferably five, especially ten pulse signals) are detected by the pulse-based speed sensor and the corresponding minimum speed is 5 km / h (preferably 10 km / h, especially 20 km / h), the determination of the difference is carried out. At low speeds and / or when the vehicle starts, it may not be accurate to determine whether the pulse signal is too early or too late. Therefore, a minimum speed can be defined, and from this speed onwards, whether the pulse signal is too early or too late is determined. The advantage of this is that the probability of incorrectly determining that the pulse signal is too early or too late is reduced.

[0024] According to an advantageous development of the invention, when the absolute value of the difference between the first difference and the second difference is less than a third threshold, it is determined whether the third pulse signal is recognized too early or too late. To determine whether the pulse signal is too early or too late, it can be required that the current speed is approximately constant, because rapid acceleration will change the pulse signal interval. If the difference between the time points of consecutive pulse signals is small enough, the acceleration is small and the speed is approximately constant. The advantage of this is that rapid acceleration will not distort the determination of whether the pulse signal is too early or too late.

[0025] According to an advantageous development of the invention, when two valid pulse signals (preferably five, especially ten valid pulse signals) are detected by the pulse-based speed sensor and the corresponding maximum speed is 20 km / h (preferably 10 km / h, especially 5 km / h), the determination of the difference is stopped. A valid pulse signal is a pulse signal that is neither recognized too early nor too late, and is neither an additional nor a missing pulse signal. If the vehicle speed is lower than the maximum speed, the determination of the difference can be stopped because the accuracy of this method decreases at low speeds. However, if a missing pulse signal is detected, that is, the measured speed may be lower than the actual speed, the determination of the difference can still be carried out. The advantage of this is that the pulse signal that is too early or too late can be determined more accurately.

[0026] According to an advantageous development of the invention, the determination of the difference is stopped when at least one of the following conditions exists:

[0027] The substitution speed is lower than a third threshold value,

[0028] the vehicle wheels are in a stationary state,

[0029] no pulse signal of the pulse-based speed sensor is detected for a determined time period.

[0030] Since the accuracy of this method may be low at low speeds, the determination of the difference can be stopped at low speeds. The advantage of this is that the pulse signals that are too early or too late can be obtained more accurately.

[0031] According to an advantageous expansion scheme of the present invention, at least one first threshold value and / or a second threshold value are set according to the speed of the vehicle. The advantage of this is that the pulse signals that are too early or too late can be reliably identified within a wide speed range.

[0032] Other important features and advantages will result from the dependent claims, the drawings and the corresponding figure legends.

[0033] It should be understood that the features described above and those to be described below can be used not only in the specified combinations, but also in other combinations or used alone, without departing from the scope of the present invention.

[0034] Preferred embodiments and implementation manners of the present invention are shown in the drawings and will be described in detail below. Description of the Drawings

[0035] The drawings show schematically:

[0036] Figure 1 method steps according to an implementation manner of the present invention;

[0037] Figure 2a - the speed change process of a pulse-based speed sensor according to an implementation manner of the present invention;

[0038] Figure 3 a flowchart according to an implementation manner of the present invention;

[0039] Figure 4 a vehicle according to an implementation manner of the present invention. Detailed Implementation Manner

[0040] Figure 1 Schematically shows method steps according to an implementation manner of the present invention.

[0041] In a first step S1, a pulse signal is detected by means of a pulse-based speed sensor on the vehicle wheels. The pulse signal corresponds to the rotation of a magnet on the vehicle wheels past the pulse-based speed sensor.

[0042] In other step S2, determine a first difference between the time points of the second pulse signal and the first pulse signal, a second difference between the time points of the third pulse signal and the second pulse signal, and a third difference between the time points of the fourth pulse signal and the third pulse signal.

[0043] In other step S3, based on at least one comparison of the first difference and / or the second difference with at least one first threshold, determine whether the third pulse signal is recognized too early or too late. This step can be performed when the vehicle reaches a specific minimum speed and the speed is approximately constant. If the following equation holds, the speed can be considered approximately constant:

[0044] Δt k ·(1 - p) < Δt k-1 <Δt k ·(1 + p)

[0045] Here:

[0046] Δtk: the second difference: the difference between the time points of the third pulse signal and the second pulse signal

[0047] Δtk - 1: the first difference: the difference between the time points of the second pulse signal and the first pulse signal

[0048] p: the allowable deviation, for example, 0.1

[0049] Therefore, if the first difference is within the tolerance interval of the allowable percentage deviation around the second difference, the pulse signals are recognized at regular intervals and the speed is approximately constant within three pulse signals.

[0050] At this time, based on the differences, it can be determined whether the third pulse signal is too early or too late according to the following equation:

[0051] Too early: Δt k-1 >Δt k ·(1 + p + )

[0052] Too late: Δt k-1 <Δt k ·(1 - p - )

[0053] Here:

[0054] p - , p + : the allowable deviation, for example, 0.1

[0055] If the first difference is greater than the second difference, the third pulse signal is recognized earlier than expected because the second and first differences are expected to be approximately equal at approximately constant speed. Similarly, if the first difference is less than the second difference, the third pulse signal is recognized too late.

[0056] If the pulse signal is recognized too early or too late according to step S3, the type of the third pulse signal can be obtained by comparing at least one of the third difference and the second difference with at least one second threshold in other step S4. The possible situations include:

[0057] A: Actual acceleration

[0058] B: Actual deceleration

[0059] C: The pulse signal is actually recognized too early

[0060] D: The pulse signal is actually recognized too late

[0061] E: An additional (false) pulse signal is recognized

[0062] F: The pulse signal is not recognized in the wrong way

[0063] If the third pulse signal is recognized too early, the possible types are A, C or E. If the third pulse signal is actually recognized too early, its interval from the fourth pulse signal is greater than expected. In particular, the first difference is greater than expected by a factor, and the third difference is less than expected by a factor, and the factors of both are the same. Therefore, if the following formula is satisfied, it can be obtained as case C:

[0064] Δt k-1 ·(1 + p + ) < Δt k+1

[0065] Here:

[0066] Δt k+1 : The third difference: the difference in time points between the fourth pulse signal and the third pulse signal

[0067] In addition, the ratio can also be checked. At a constant speed and with a pulse offset, Δt_(k - 1)·2 = Δt_k + Δt_(k + 1) is satisfied. The condition with an additional tolerance is obtained:

[0068] Δt k-1 ·2·(1 - p shift ) < Δt k + Δt k+1 < Δt k-1 ·2·(1 + p shift )

[0069] where p_shift is the allowable percentage deviation (e.g., 0.1 = 10%). A speed-dependent parameterization can also be used here.

[0070] However, if an additional (erroneous) pulse signal is recognized, the third difference is also smaller than expected because the additional pulse signal is recognized between two regular pulses. Therefore, the total time between two regular pulses (i.e., the sum of the second and third differences) should be within the tolerance interval of the first difference. Therefore, if the following equation is satisfied, an additional pulse signal of type E can be recognized:

[0071] Δt k-1 ·(1 - p add ) < Δt k +Δt k+1 <Δt k-1 ·(1 + p add )

[0072] Here:

[0073] p add : Allowable deviation, e.g., 0.1

[0074] If the above equations are not satisfied, it is case A, i.e., the actual acceleration of the vehicle during the detection of the pulse signal.

[0075] If the third pulse signal is recognized too late, it may be of type B, D, or F. If the third pulse signal is actually recognized too late, the interval between it and the fourth pulse signal is smaller than expected. In particular, the first difference is smaller than expected by a factor, and the third difference is larger than expected by the same factor. Therefore, if the following equation is satisfied, it can be recognized as case D:

[0076] Δt k-1 ·(1 - p - ) > Δt k+1

[0077] In addition, the ratio can also be checked. At a constant speed and with a pulse offset, Δt_(k - 1)·2 = Δt_k + Δt_(k + 1) is satisfied. The condition with an additional tolerance is obtained:

[0078] Δt k-1 ·2·(1 - p shift ) < Δt k +Δt k+1 <Δt k-1 ·2·(1 + p shift )

[0079] where p_shift is the allowable percentage deviation (typical value: 0.1 = 10%). Speed-dependent parameterization can also be used here.

[0080] However, if a pulse signal is missing (i.e., not recognized), the fourth pulse signal will not be recognized because one pulse signal is missing between two regular pulses. Therefore, the time between the two pulse signals before and after the missing pulse signal should be twice the interval between two regular pulses. Therefore, if the following equation is satisfied, a missing pulse signal of type F can be recognized:

[0081] Δt k > Δt k-1 *(2 - p miss )

[0082] Wherein:

[0083] p miss : Allowable deviation, such as 0.3

[0084] If the above equations are not satisfied, it is Case B, that is, the actual deceleration of the vehicle during the detection pulse signal.

[0085] Figure 2a -f shows the change process of the speed of the pulse - based speed sensor according to an embodiment of the present invention.

[0086] If an incorrect pulse signal is detected according to steps S1 to S4, the speed measured by the pulse - based speed sensor will be different from the actual speed of the vehicle.

[0087] Therefore, according to the type of the incorrect pulse signal, an alternative speed can be used to provide a continuously accurate speed calculation.

[0088] Figure 2a -f respectively shows the speed change processes of the pulse - based speed sensor 205 and the alternative speed sensor 204 for different types A to F of pulse signals. The x - axis 201 represents time in arbitrary units, and the y - axis 202 represents speed in arbitrary units. Four pulse signals t k-2 , t k-1 , t k , t k+1 203a, 203b, 203b, 203d, 203e are measured each time, where the pulse signal at the time point t k is detected too early or too late, Figure 2f except that one pulse signal is missing.

[0089] Figure 2a Shows the speed change process in the case of actual acceleration according to type A. All pulse signals are valid, neither detected too early nor too late. The pulse signal at the time point t k (marked 203c) is detected earlier than expected due to acceleration ( Figure 2a in the stage I between the time points t k-1 , t k ) and may be regarded as incorrect. In stage II ( Figure 2a in the time points t k , t k+1 , between), it is not yet possible to confirm whether the pulse - based speed 205 reflects the actual speed. Therefore, the alternative speed 204 is used in stage II. From stage III (Figure 2a at time point t in k+1 , t k+2, between), the pulse - based speed sensor 205 is reused.

[0090] Figure 2b Shows the speed change process under the actual deceleration of type B. In phases I.II ( Figure 2a at time point t in k-1 , t k , between), it is recognized that the second pulse signal is delayed. Therefore, from phase I.II to phase II ( Figure 2a at time point t in k , t k+1 , between), the alternative speed 204 is used. From phase III ( Figure 2a at time point t in k+1 , t k+2 , between), the pulse - based speed 205 can be reused.

[0091] Figure 2c Shows the speed change process under the case of prematurely recognized pulse signals of type C (i.e., wrongly prematurely recognized pulse signals). The pulse signal at time point t k , is recognized earlier than expected. Therefore, the speed curve of the pulse - based speed sensor 205 rises in the first time period in phase II.I ( Figure 2c at time point t in k , t k+1 between). In phase II.II ( Figure 2c at time point t in k , t k+1 between), no other pulse signals are detected. Therefore, the speed of the pulse - based speed sensor 205 drops until time point t k+1 . From time point t k+2 on, the pulse - based speed sensor 205 measures the correct speed again. Therefore, in phases II.I to III ( Figure 2c at time point t in k+1 , t k+2 between), the alternative speed 204 is used.

[0092] Figure 2d Shows the speed change process under the case of too - late recognition of pulse signals of type D. In phase I.II ( Figure 2d at time point t in k-1 , t k between, the second time period), no pulse signals are detected first. Therefore, the speed of the pulse - based speed sensor 205 drops first. At time point t k+1A regular pulse signal is detected, causing the speed obtained by the pulse-based speed sensor 205 to increase. During stage III.II ( Figure 2d at time point t k+1 ,t k+2 in the second time period between), no pulse signal is recognized, and the speed of the pulse-based speed sensor 205 decreases again until time point t k+2 . Therefore, the alternative speed 204 is used in stages I.I to III.II.

[0093] Figure 2e Shows the speed change process in the case of additionally recognizing a pulse signal according to type E. The pulse signal at time point t k is additionally recognized. Therefore, the speed of the pulse-based speed sensor 205 suddenly increases and then decreases during the process of the next two pulse signals. Therefore, in stage II ( Figure 2e at time point t k ,t k+1 between) and III ( Figure 2e at time point t k+1 ,t k+2 between) time periods, the alternative speed is used. The same applies to the following cases: the speed suddenly increases twice and then decreases during the process of the next two pulse signals.

[0094] Figure 2f Shows the speed change process in the case of missing a pulse signal according to type F. At the end of stage I.I ( Figure 2f at time point t k-1 ,t k in the first time period between), no pulse signal is recognized. Therefore, according to the pulse-based speed signal, the speed decreases until the time point t k of the next regular pulse signal. From the time point t k+1 of the next pulse signal onwards, the pulse-based speed sensor can be reused for speed determination. Therefore, in stage I.II ( Figure 2f at time point t k-1 ,t k in the second time period between) and II ( Figure 2f at time point t k ,t k+1 between), the alternative speed 205 is used.

[0095] Figure 3 Schematically shows a flowchart according to an embodiment of the present invention.

[0096] First, the recognition of the error sensor is deactivated - state 301. When the activation condition (such as exceeding the minimum speed) is met, the recognition is activated - state 302. If the activation condition is no longer met, the recognition can be deactivated again - state 301. Then it is checked whether the speed is approximately constant - calculation 303. If so, it is checked whether the pulse signal is too early or too late within the tolerance range - determination 304. For this purpose, the two consecutive differences of the time points of three consecutive pulse signals are compared. If the first difference is greater than the second difference, the third pulse signal is too early; if the first difference is less than the second difference, the pulse signal is too late. Subsequently, based on the third difference check of the time points of the third pulse signal and the fourth pulse signal, which type the third pulse signal belongs to is checked.

[0097] If the pulse signal is too early - state 305 - it is checked whether the third difference is greater than the first difference in a ratio similar to the second difference being less than the first difference - determination 306. If so, the pulse signal is offset and is prematurely recognized, for case C - state 307. Otherwise, it is checked whether the sum of the third difference and the second difference is approximately equal to the first difference - determination 308. At this time, an additional pulse signal is recognized; case E - state 309 - otherwise it is the actual acceleration of the vehicle; case A - state 310.

[0098] On the contrary, if the pulse signal is too late - state 311 - it is checked whether the third difference is less than the first difference in a coefficient similar to the second difference being greater than the first difference - determination 312. If so, the pulse signal is offset and is recognized too late; case D - state 313. Otherwise, it is checked whether the second difference is approximately twice the first difference - determination 314. At this time, a pulse signal is missing; case F - state 315 - otherwise it is the actual deceleration of the vehicle; case B - state 316.

[0099] In each case, the alternative speed is switched to for a short time to ensure accurate speed recognition, where the time period of using the alternative speed depends on the type obtained. Then it waits for a stable speed signal - state 317. If neither a missing pulse signal nor an actual acceleration or deceleration is detected, it can first wait for the fifth pulse signal - determination 318. In addition, if too many pulse signals are recognized prematurely, too late, additionally, or missing, the sensor can be classified as faulty.

[0100] Figure 4 A vehicle according to an embodiment of the present invention is shown.

[0101] Figure 4 A vehicle 1 (in the form of an electric bicycle here) is shown, with a pulse-based speed sensor 6, including:

[0102] A detection unit 2, which is configured to detect the first, second, third, and fourth pulse signals through a pulse-based speed sensor,

[0103] Determining device 3, configured to determine a first difference between the time points of a second pulse signal and a first pulse signal, a second difference between the time points of a third pulse signal and the second pulse signal,

[0104] and a third difference between the time points of a fourth pulse signal and the third pulse signal,

[0105] First determination unit 4, configured to determine whether the third pulse signal is recognized too early or too late based on at least one comparison of the first difference and / or the second difference with at least one first threshold value,

[0106] Second determination unit 5, configured to determine the type of the third pulse signal based on at least one comparison of the third difference and the second difference with at least one second threshold value.

[0107] Vehicle 1 is particularly configured to execute Figure 1 the steps S1 to S4 in. The first measurement unit 2 can be integrally configured with a pulse-based speed sensor 6.

[0108] Although the present invention has been described by way of preferred embodiments, it is not limited thereto and can be modified in various ways.

Claims

1. A method for determining an incorrect pulse signal in the speed measurement of a vehicle (1), in particular a monorail vehicle (1), such as an electric bicycle, wherein, the vehicle (1) has a pulse-based speed sensor (6) on the wheel, and the method includes the following steps: (S1) Detect a first pulse signal, a second pulse signal, a third pulse signal, and a fourth pulse signal by means of the pulse-based speed sensor. (S2) Determine a first difference between the time points of the second pulse signal and the first pulse signal, determine a second difference between the time points of the third pulse signal and the second pulse signal, and determine a third difference between the time points of the fourth pulse signal and the third pulse signal. (S3) Based on at least one comparison of the first difference and / or the second difference with at least one first threshold, determine whether the third pulse signal is recognized too early or too late. (S4) Based on at least one comparison of the third difference and the second difference with at least one second threshold, determine the type of the third pulse signal.

2. The method according to claim 1, wherein, the vehicle (1) has other speed sensors, and an alternative speed is determined by means of the other speed sensors.

3. The method according to claim 2, wherein, if it is determined that the third pulse signal is recognized too early or too late, the alternative speed is used for speed measurement.

4. The method according to claim 3, wherein, a time period is determined based on the type of the determined pulse signal, and the alternative speed is used for speed measurement during the time period.

5. The method according to any one of claims 1 to 4, wherein, if two pulse signals, preferably five pulse signals, especially ten pulse signals are detected by the pulse-based speed sensor, and the pulse signals correspond to a minimum speed of 5 km / h, preferably 10 km / h, especially 20 km / h, the determination of the difference (S2) is performed.

6. The method according to any one of claims 1 to 5, wherein, if the absolute value of the difference between the first difference and the second difference is less than a third threshold, the determination (S3) of whether the third pulse signal is recognized too early or too late is performed.

7. The method according to any one of claims 1 to 6, wherein, if two valid pulse signals, preferably five valid pulse signals, especially ten valid pulse signals are detected by the pulse-based speed sensor, and the valid pulse signals correspond to a maximum speed of 20 km / h, preferably 10 km / h, especially 5 km / h, the determination of the difference (S2) is stopped.

8. The method according to any one of claims 1 to 7, wherein, if at least one of the following conditions exists, the determination of the difference (S2) is stopped: the alternative speed is lower than the third threshold, the wheel of the vehicle (1) is in a stationary state, no pulse signal of the pulse-based speed sensor is detected for the determined time period.

9. The method according to any one of claims 1 to 8, wherein, the at least one first threshold and / or the second threshold is set according to the speed of the vehicle (1).

10. A vehicle (1), in particular a monorail vehicle (1), such as an electric bicycle, having a pulse-based speed sensor (6) on a wheel of the vehicle, wherein, the vehicle (1) is configured to determine a false pulse signal in a speed measurement of the vehicle (1), and the vehicle includes: a detection unit (2) configured to detect a first pulse signal, a second pulse signal, a third pulse signal, and a fourth pulse signal by means of the pulse-based speed sensor, and a determination device (3) configured to determine a first difference in time points between the second pulse signal and the first pulse signal, determine a second difference in time points between the third pulse signal and the second pulse signal, and determine a third difference in time points between the fourth pulse signal and the third pulse signal, a first determination unit (4) configured to determine, based on at least one comparison of the first difference and / or the second difference with at least one first threshold, whether the third pulse signal is recognized too early or too late, a second determination unit (5) configured to determine, based on at least one comparison of the third difference and the second difference with at least one second threshold, the type of the third pulse signal.

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