METHOD AND DEVICE FOR CHECKING THE PLAUSIBILITY OF A SENSOR SIGNAL OF A SINGLE-TRACK VEHICLE

Description

State of the art

[0001] The invention relates to a method for checking the plausibility of a sensor signal of a single-track vehicle, in particular an eBike, a pedelec or the like.

[0002] The plausibility check of a vehicle’s sensor signals is described in the patents DE102019115312 B3 and DE102014212760 A1.

[0003] The invention further relates to a plausibility check device which is designed to determine the reliability of a sensor signal of a single-track vehicle, in particular an eBike, a pedelec or the like.

[0004] The invention further relates to a system comprising a single-track vehicle, in particular an eBike, a pedelec or the like, and a plausibility check device.

[0005] Although the present invention is generally applicable to any single-track vehicle, the present invention is described with reference to bicycles in the form of eBikes or Pedelecs.

[0006] E-bikes provide propulsion assistance to a rider through a drive unit with a motor. The respective drive unit includes not only the respective drive motor but also sensors, for example, to determine the e-bike's speed. The propulsion assistance level changes depending on the e-bike's speed. Above a certain maximum speed, the propulsion assistance no longer provides any supporting drive torque.

[0007] Due to sensor malfunctions, it may happen that a driving speed sensor measures too low a speed and therefore the drive assistance remains activated beyond the maximum speed. Disclosure of the invention

[0008] In one embodiment, the present invention provides a method for checking the plausibility of a sensor signal of a single-track vehicle, comprising the following steps: Estimating gear ratios between a wheel speed of a wheel and a cadence of a pedal of a pedal unit and / or a drive speed of a drive of the single-track vehicle at several points in time, determining a value of a reliability indicator based on the estimated gear ratios, wherein the value of the reliability indicator is determined using a statistical parameter, in particular a variance, of the estimated gear ratios and / or a histogram of the estimated gear ratios, checking the plausibility of the sensor signal by comparing the value of the reliability indicator with a threshold value, wherein the threshold value corresponds to a maximum permissible value of the reliability indicator.

[0009] In one embodiment, the present invention provides a plausibility check device configured to determine the reliability of a sensor signal of a single-track vehicle, comprising: an estimation device designed to estimate a gear ratio between a wheel speed and a cadence and / or a drive speed of the single-track vehicle at a plurality of points in time, a determination device designed to determine a value of a reliability indicator based on the estimated gear ratios, wherein the value of the reliability indicator is determined based on a statistical parameter, in particular a variance, of the estimated gear ratios and / or a histogram of the estimated gear ratios, a plausibility check device designed to check the plausibility of the sensor signal based on the value of the reliability indicator and a threshold value, wherein the threshold value corresponds to a maximum permissible value of the reliability indicator.

[0010] In one embodiment, the present invention provides a system comprising a single-track vehicle and a plausibility check device according to claim 10.

[0011] While pedaling during a ride, the gear ratio, i.e., the ratio between the pedal / drive speed and the wheel speed, can be approximately constant. The gear ratio can be estimated based on the ratio of the values of a wheel speed sensor and a pedal / drive speed sensor according to embodiments of the invention. If a sensor delivers incorrect values due to malfunctions, the estimated gear ratio is no longer constant, in particular, but can exhibit a large value of a statistical parameter, in particular a high variance, over the ride. A high variance of the estimated gear ratios can therefore, for example, be an indicator that a sensor is faulty.

[0012] According to embodiments of the invention, the estimated gear ratios can also be transferred to a histogram. If there are no sensor malfunctions, a sparse histogram results (thin lines in the histogram that correspond to the gear ratios of the various gears). Blurring of the lines, however, indicates that the sensor is providing incorrect values. The advantage of the histogram is that even slow changes in the estimated gear ratios can be detected. If the estimated gear ratios change only slowly, their statistical characteristic, in particular their variance, is low, so that the value of the reliability indicator may not reach the threshold. However, the blurring of the lines in the histogram is detectable even with slow changes.

[0013] One of the advantages achieved is that the reliability of a sensor signal can be easily determined, thus allowing sensor malfunctions to be detected. Another advantage is that the plausibility check can be performed without a redundant sensor. This allows the method to be implemented in a simple and cost-effective manner.

[0014] Further features, advantages and further embodiments of the invention are described below or will become apparent thereby.

[0015] According to an advantageous development of the invention, the estimation of the gear ratios is suspended as long as a change in the gear ratio takes place and / or as long as a minimum torque on a drive side of the single-track vehicle is not reached. During the change in the gear ratio and / or as long as no torque is applied to the drive side of the single-track vehicle, in particular when the bicycle is in freewheel mode, the gear ratios may have a large value of a statistical parameter, in particular a large variance, and an erroneous value for the reliability indicator could be determined. By suspending the estimation, the accuracy of the reliability indicator can be ensured. The change in the gear ratio can be detected, for example, via a sudden change in the engine speed.Additionally or alternatively, the estimation can also be suspended if a minimum speed and / or minimum cadence of a drive is undershot. It is also possible for the estimation to be suspended for a predefined period of time upon detection of a change in torque and / or if the minimum torque, minimum speed, and / or minimum cadence are undershot.

[0016] According to a further advantageous development of the invention, the value of the reliability indicator is determined based on the statistical parameter, in particular the variance, of estimated gear ratios determined since the last change in the gear ratio. The advantage of this is that the correctness or accuracy of the reliability indicator can be increased, since the estimates of the gear ratio exhibit an inherently large variance when there are multiple rapid changes in the gear ratio.

[0017] According to a further advantageous development of the invention, the value of the reliability indicator is determined based on a number of at least 3 and a maximum of 50 most recently estimated gear ratios, in particular at least 5 and a maximum of 30 most recently estimated gear ratios, preferably at least 8 and a maximum of 20 most recently estimated gear ratios. The advantage of this is that the value of the reliability indicator is based on a sufficient number of values to be able to verify the plausibility of the sensor signal, and at the same time, the value of the reliability indicator can be determined sufficiently quickly.

[0018] According to a further advantageous development of the invention, the number of estimated gear ratios is determined based on the value of the reliability indicator. If the value of the reliability indicator is low, i.e., the probability of malfunctions is low, the number of estimated gear ratios used can be reduced. This allows the plausibility check to be performed more efficiently.

[0019] According to a further advantageous development of the invention, an information signal is generated to inform a user about a threshold violation and / or to reduce drive power if the value of the reliability indicator exceeds the threshold. The information signal can, for example, be a message that the vehicle must be inspected at a service station. This ensures that a user is aware that a malfunction exists and that the single-track vehicle must be inspected. Furthermore, it is ensured that the single-track vehicle is not accelerated by the drive unit beyond its maximum speed.

[0020] According to a further advantageous development of the invention, the value of the reliability indicator is determined based on a peak detection algorithm and / or on at least a first-order derivative of a function that describes the values of the estimated gear ratios. In the event of sensor malfunctions, sudden changes in the estimated gear ratios may occur at a given time, even though the gear ratio was not changed at the same time. These sudden changes can therefore also serve as a reliability indicator. Such sudden changes can be easily detected using a peak detection algorithm, for example, CFAR. Alternatively or additionally, a function that describes the gear ratios can be determined, for example, using a Savitzky-Golay filter, and the derivative of this function can be determined.High values of the derivative are also indicators of sudden changes and can therefore be used to determine the value of the reliability indicator. The advantage of this is that the value of the reliability indicator can be determined easily.

[0021] According to a further advantageous development of the invention, the value of the reliability indicator determined from the histogram corresponds to the width of one or more peaks in the histogram. For this purpose, the estimated gear ratios are sorted into predefined bins; for example, up to 500 bins can be used in a range of estimated gear ratios from 0.5 to 5. High values in the histogram result when estimated gear ratios occur frequently in individual bins. If the sensors are not malfunctioning, it is expected that those gear ratios that correspond to the gear ratios are the ones that occur frequently. Due to vibrations, slippage, and inaccurate measurements, gear ratios whose values are close to the gear ratios can also be estimated. This is shown in the histogram by narrow but high peaks.Due to malfunctions, the estimated gear ratios change and no longer correspond to the gear ratios, but become scattered. This is reflected in the histogram by the fact that the peaks are wider and less high than peaks in a histogram created when the sensors are not malfunctioning. The width of the peaks is therefore a reliability indicator for the sensor signal. This makes it easy to determine a value for the reliability indicator.

[0022] The width of the peaks can be determined in several ways. For example, with the help of a peak detection algorithm, in particular CFAR, the individual peaks are first identified, whereby the peaks correspond to gear ratios driven when the sensors were fault-free. The width of this peak is determined by calculating the difference between the smallest and largest estimated gear ratios that are within a continuous value range, whereby in particular each value within the value range has been estimated at least once. The difference therefore corresponds to the maximum width of a peak. Alternatively, only those gear ratios that have been estimated more often than a limit value can be taken into account. The limit value can, for example, correspond to half the maximum value of a peak, e.g. Full Width at Half Maximum.The threshold above which the sensor signal is considered unreliable can in this case be 0.1, in particular 0.05, and preferably 0.03. Of the estimated gear ratios considered, the difference between the largest and smallest values within a range is also calculated. This eliminates one-off outliers. If the estimated gear ratios all lie within a single value range, meaning there is only one peak, the difference can be used directly as a reliability indicator. If, however, the estimated gear ratios lie within multiple value ranges—for example, because the gear was changed during the journey—and consequently multiple differences have been calculated, the average or the maximum value of the differences can be used as the reliability indicator value.

[0023] According to a further advantageous development of the invention, the sensor signal is a speed signal, a drive speed signal, a cadence signal and / or a wheel speed signal. The advantage of this is that different sensor signals can be checked for plausibility. One signal can be checked for plausibility by assuming another signal is known and correct. For example, the cadence can be used to check the plausibility of the speed of a wheel, from which the speed of the single-track vehicle can be deduced. However, it is also possible to check the plausibility of the drive speed based on the speed. For this purpose, the speed can be determined via a third-party source, such as a GPS recording.

[0024] According to a further advantageous development of the invention, the value of the reliability indicator is determined based on a relative difference between the estimated gear ratio and a gear ratio provided by the single-track vehicle, wherein the gear ratio provided by the single-track vehicle is continuously variable. The gear ratio provided by the single-track vehicle can be provided, for example, via a wired or wireless interface and can be determined from a current stage of a gearshift. The advantage of this is that the method can also be used for single-track vehicles with a continuous gear ratio—i.e., without fixed gears. With a continuous gear ratio, the estimated gear ratios also change continuously, so that the value of the statistical parameter, in particular its variance, is inherently high.However, since the actual and estimated gear ratios are ideally equal at any given time, the difference between them is almost zero and thus nearly constant. Significant deviations and / or a high variance in this difference are therefore a sign that a sensor is sending false signals, and the value of the reliability indicator can be determined from this. It is also possible that the plausibility check is performed using the histogram.

[0025] According to a further advantageous development of the invention, the value of the reliability indicator is based on the number of detected peaks. In a fault-free state of the sensors, the number of peaks corresponds at most to the number of gears. If the number of peaks is higher than the number of gears, this is an indicator that the sensor signal is unreliable. The advantage of this is that the reliability indicator can be determined easily.

[0026] Further important features and advantages of the invention emerge from the subclaims, from the drawings and from the associated description of the figures with reference to the drawings.

[0027] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0028] Preferred embodiments and embodiments of the present invention are illustrated in the drawings and are explained in more detail in the following description, wherein like reference numerals refer to like or similar or functionally identical components or elements.

[0029] This shows Figure 1 shows, in schematic form, steps of a method according to an embodiment of the present invention; Figure 2 shows, in schematic form, a first histogram according to a further embodiment of the present invention; Figure 3 shows, in schematic form, a second histogram according to a further embodiment of the present invention; and Figure 4 shows, in schematic form, a third histogram according to an embodiment of the present invention.

[0030] Figure 1 shows in schematic form steps of a method according to an embodiment of the present invention.

[0031] In detail, Figure 1 Steps of a method for checking the plausibility of a sensor signal of a single-track vehicle, comprising the following steps: Estimating S1 gear ratios between a wheel speed of a wheel and a pedal cadence of a pedal unit and / or a drive speed of a drive of the single-track vehicle at several points in time, determining S2 a value of a reliability indicator based on the estimated gear ratios, wherein the value of the reliability indicator is determined using a statistical parameter, in particular a variance, of the estimated gear ratios and / or a histogram of the estimated gear ratios, checking the plausibility S3 of the sensor signal by comparing the value of the reliability indicator with a threshold value, wherein the threshold value corresponds to a maximum permissible value of the reliability indicator

[0032] In other words, in step S1, a gear ratio is estimated for a single-track vehicle as the ratio of a wheel speed, for example, a rear wheel speed, and a pedal cadence. For example, in a bicycle, the pedal cadence of a chain drive is in a fixed relationship to the rear wheel speed. As long as the rear wheel is not freewheeling, the estimated gear ratio is approximately constant. This gear ratio is estimated at multiple points in time.

[0033] In other words, in step S2, a value of a reliability indicator is determined based on the estimated gear ratios. As long as the bicycle is in a fixed gear, the actual gear ratio between the drive and rear wheels remains constant, and consequently the estimated gear ratio must also remain constant, apart from small measurement inaccuracies. This means that the value of the statistical parameter, in particular the variance, of the estimated gear ratios is small as long as the sensors required to estimate the gear ratio are functioning correctly. However, if a sensor malfunctions and delivers incorrect values, the estimated gear ratio would no longer be constant but would fluctuate over the course of a ride. This is indicated by an increased value of the statistical parameter, in particular an increased variance, compared to the error-free state.The value of the statistical parameter of the gear ratios therefore provides information about the reliability of the sensor signal and can serve as the basis for the value of the reliability indicator.

[0034] Alternatively or additionally, the estimated gear ratios can be entered into a histogram in step S2. A bicycle has a fixed number of gears and consequently a fixed number of possible gear ratios. If the gear ratios estimated during the ride are entered into a histogram, in the error-free state only gear ratios would have to be estimated that correspond to the gear ratios of the individual gears. This is shown in the histogram by the fact that a line is created for each gear that corresponds to the gear ratio of the gear. Due to measurement inaccuracies and vibrations, the actually estimated gear ratios can fluctuate around the ideal values, resulting in peaks in the histogram in reality. The width of these peaks is narrow in the error-free state, i.e. the width of the peaks is small compared to the distance between the peaks.However, if a sensor malfunctions and the estimated gear ratios are no longer constant, this is reflected in the peaks in the histogram becoming wider and, in extreme cases, "smearing" into one another. The width of the peaks can therefore also be used to determine the reliability of the sensor signal, so the width of the peaks in the histogram can also serve as the basis for the value of the reliability indicator. This is explained in the . Figures 2 to 4 clarified even more precisely.

[0035] In other words, in step S3, the sensor signal is checked for plausibility by comparing the value of the reliability indicator with a threshold value. The threshold value corresponds, in particular, to a defined limit value above which the sensor signal is classified as unreliable. The threshold value can be determined empirically, for example. If the value of the reliability indicator is greater than the threshold value, i.e., the value of the statistical parameter, in particular the variance, of the estimated gear ratios is too high, the sensor signal is considered unreliable, and the bicycle's drive assistance can be deactivated or reduced.

[0036] Figure 2 shows in schematic form a first histogram according to an embodiment of the present invention.

[0037] In detail, Figure 2 a histogram which is generated when performing the Figure 1The histogram according to the method shown Figure 2 indicates the fault-free status of the bicycle. The abscissa 1 corresponds to the estimated gear ratios, and the ordinate 2 corresponds to the frequency of the estimated gear ratios. Six peaks 3a–f can be seen in the histogram, with the width 5 of each peak being small. This is an indicator that a sensor is functioning correctly, as only a few defined gear ratios were estimated, and these correspond to the bicycle's gears.

[0038] Figure 3 shows in schematic form a second histogram according to an embodiment of the present invention.

[0039] Compared to the Figure 2 shows Figure 3in schematic form, a second histogram according to an embodiment of the present invention, in which the width 5 of the peaks 3a-f is not small, but high. This means that the estimated gear ratios do not always correspond to the actual gear ratios, but rather to gear ratios that cannot be realized in reality on the bicycle. This is an indicator that the sensor signal may be unreliable or faulty. The wider and more blurred the peaks 3a-f are, the more unreliable the sensor signal is. The width 5 of the peaks 3a-f can, for example, be measured on the abscissa 1, or at half the height 4 of the peaks, in order to be able to exclude individual outliers.

[0040] Figure 4 shows in schematic form a third histogram according to an embodiment of the present invention.

[0041] Figure 4Finally, FIG. 1 shows a schematic representation of a third histogram according to an embodiment of the present invention, in which peaks 3a-f "run into each other" and no longer form separate, distinct regions. Thus, a multitude of different ratios have been estimated. This implies that the sensor signal is highly unreliable and the sensor is likely faulty.

[0042] In summary, at least one embodiment of the present invention has at least one of the following features and / or provides at least one of the following advantages: Plausibility check of a sensor signal in a simple way Detection of sensor malfunctions Plausibility check without redundant sensor Plausibility check of various sensor signals possible Simple and cost-effective implementation

[0043] Although the present invention has been described using preferred embodiments, it is not limited thereto but can be modified in many ways.

Claims

1. Method for checking the plausibility of a sensor signal from a single-track vehicle, comprising the following steps of: - estimating (S1) transmission ratios between a wheel speed of a wheel and a cadence of a pedal of a pedal unit and / or a drive speed of a drive of the single-track vehicle at multiple points in time, characterized by the following steps of: - determining (S2) a value of a reliability indicator based on the estimated transmission ratios, the value of the reliability indicator being determined on the basis of a statistical characteristic variable of the estimated transmission ratios and / or a histogram of the estimated transmission ratios, - checking the plausibility (S3) of the sensor signal by comparing the value of the reliability indicator with a threshold value, the threshold value corresponding to a maximum permissible value of the reliability indicator.

2. Method according to Claim 1, wherein the estimation of the transmission ratios is suspended as long as the transmission ratio changes and / or as long as a minimum torque on a drive side of the single-track vehicle is undershot.

3. Method according to one of Claims 1-2, wherein the value of the reliability indicator is determined based on a number of at least 3 and at most 50 last estimated transmission ratios, in particular at least 5 and at most 30 last estimated transmission ratios, preferably at least 8 and at most 20 last estimated transmission ratios.

4. Method according to Claim 3, wherein the number of estimated transmission ratios is determined on the basis of the value of the reliability indicator.

5. Method according to one of Claims 1 - 4, wherein an information signal for informing a user about a threshold value violation is generated and / or a drive power is reduced when the value of the reliability indicator exceeds the threshold value.

6. Method according to one of Claims 1 - 5, wherein the value of the reliability indicator is determined based on a peak detection algorithm and / or on an at least first-order derivative of a function describing the values of the estimated transmission ratios.

7. Method according to one of Claims 1 - 6, wherein the value of the reliability indicator determined on the basis of the histogram corresponds to a width (5) of one or more peaks (3a - f) in the histogram.

8. Method according to one of Claims 1 - 7, wherein the sensor signal is a speed signal, a drive speed signal, a cadence signal and / or a wheel speed signal.

9. Method according to one of Claims 1 - 8, wherein the value of the reliability indicator is determined based on a relative difference between the estimated transmission ratio and a transmission ratio provided by the single-track vehicle, wherein the transmission ratio provided by the single-track vehicle is continuously variable.

10. Method according to one of Claims 1-9, wherein the value of the reliability indicator is based on a number of detected peaks (3a-f).

11. Method according to one of the preceding claims, wherein the statistical characteristic variable is in the form of a variance.

12. Plausibility-checking apparatus which is designed to determine the reliability of a sensor signal from a single-track vehicle, comprising: - an estimation device designed to estimate a transmission ratio between a wheel speed and a cadence and / or a drive speed of the single-track vehicle at multiple points in time, characterized by: - a determination device designed to determine a value of a reliability indicator based on the estimated transmission ratios, the value of the reliability indicator being determined on the basis of a statistical characteristic variable, in particular a variance, of the estimated transmission ratios and / or a histogram of the estimated transmission ratios, - a plausibility-checking device designed to check the plausibility of the sensor signal on the basis of the value of the reliability indicator and a threshold value, the threshold value corresponding to a maximum permissible value of the reliability indicator.

13. System comprising a single-track vehicle and a plausibility-checking apparatus according to Claim 12.