METHOD AND DEVICE FOR DETERMINING THE VEHICLE'S SPEED

Description

[0001] The invention relates to a method and a device for determining a speed value of a vehicle and to a vehicle having a corresponding method or device. State of the art

[0002] EP 3 435 094 A2 discloses an evaluation unit which records the movement behavior of a wheel of a two-wheeler.

[0003] In common bicycle speed detection systems, a magnet is attached to a spoke, which rotates around the wheel's axis as the bicycle moves. To detect this rotational movement and thus determine the speed of travel, a magnetic field sensor, usually in the form of a Hall sensor, is attached to the fork. This generates a magnetic pulse each time the magnet passes. The rotational speed, or the speed of travel, of the bicycle is derived from the time interval between two consecutively generated pulses, based on the wheel diameter.

[0004] However, detecting the magnetic pulse can be problematic if the magnet is too far away from the magnetic field sensor or if the magnetic field sensor has too low a measurement intensity. Furthermore, interfering magnetic fields can complicate detection.

[0005] The object of the present invention is to improve the detection of magnetic pulses, especially when interfering magnetic fields occur. Disclosure of the invention

[0006] The present invention claims a method and a device for determining a speed value of a vehicle, as well as a vehicle having such a device or a corresponding method. The vehicle can be either a motor vehicle or an electrically and / or manually powered two-wheeler, for example, a bicycle, an electric bicycle, an e-scooter, or a motorcycle.

[0007] To determine the speed value, at least first and second sensor variables, which represent the movement of a wheel of the vehicle, are detected by means of a sensor, for example a magnetic field sensor. The speed value is determined from the time interval between the first and second sensor variables. For this purpose, the sensor variables or the detected sensor values ​​are each compared with a first threshold value, wherein the time interval between the particular exceedance of this sensor variable is determined. The core of the invention consists in the fact that a movement variable, which represents the movement of the vehicle in the direction of travel or longitudinal direction, is detected by means of a second sensor, namely an acceleration sensor or an inertial sensor.Based on this locomotion value, a time period is derived within which, after the first sensor value has exceeded the first threshold, the second sensor value is expected to exceed the first threshold. If the second sensor value does not exceed the first threshold after the expiration of the time period, a second threshold is set that is lower than the first threshold. This lower second threshold is used in the subsequent determination of the speed value, in determining the temporal difference between the first and second sensor values, and in particular in the comparison.

[0008] The advantage of such a change and the use of a second, lower threshold value is that if there is a disturbance in the detection or a reduction in the signal strength of the sensor variables, the determination of the speed value is adjusted to the disturbed or reduced signal strength. However, if no disturbance in the sensor variable signal is present or detected, the determination of the speed value is carried out without changing the comparison to the second threshold value.

[0009] In a further development of the invention, the time period derived from the locomotion variable is shorter than the expected time interval between the first and second sensor variables exceeding the first threshold value. For example, the time period can be set to a low percentage value, e.g., 90%, 75%, or 60%, in order to account for changes in the (rotational) speed during the measured value acquisition and for measurement inaccuracies.

[0010] Furthermore, it can be provided that the second threshold is defined as a percentage reduction or decrease of the first threshold. For example, a reduction to 90%, 80%, 75%, or 60% can be provided. Generally, it can be provided that the reduction or decrease of the second threshold occurs in several stages. This can be useful if the defined second threshold is not exceeded by at least one of the sensor variables after the expiration of the time period.

[0011] In an optional embodiment of the invention, it can be provided that during the comparison of the first and / or second sensor variable with the second threshold value, a difference is formed between the maximum value of the corresponding sensor variable and the second threshold value. If the difference exceeds a positive predetermined first value, this can be interpreted as a sign that the signal strength has increased. In this case, it can be provided that the second threshold value is increased, for example gradually or to the original first threshold value. However, if a negative difference is determined, ie the corresponding sensor variable or its maximum value is below the second threshold value, in particular below a second predetermined value for the difference, it can be provided that the second threshold value is further reduced or lowered.Both the increase and decrease can be made dependent on the corresponding difference being above or below the corresponding specified value in at least two comparisons. This disregards short-term changes in signal strength.

[0012] In a further development, it can be provided that, in addition to comparing the sensor variable with the second threshold value, a comparison with the first threshold value is also carried out. If it is detected that the respective sensor variable exceeds both the second and the first threshold value, the second threshold value can be set to the value of the first threshold value for the further determination of the speed value or the determination of the time interval. It can also be provided that the second threshold value is only changed when, in at least two consecutive comparisons, the first and second sensor variables each exceed the second and first threshold values.

[0013] In general, the speed value is to be determined continuously. The first threshold can be used initially for subsequent determinations of the temporal sequence or for determining the speed value within the context of the comparison. If the signal strength is detected to be too low, regardless of whether the comparison is with the first or second sensor variable, the lower second threshold can be used for further comparisons and thus for determining the speed values. By checking to what extent the signal strength increases again and also exceeds the first threshold again, the second threshold can be set to the value of the original first threshold if the signal strength increases accordingly.

[0014] The method according to the invention for determining the speed value and adjusting the threshold values ​​can also be carried out in a control unit. For this purpose, the control unit records the sensor variables of a first sensor, which is attached, for example, to the vehicle and in particular to a part that also moves with the vehicle's movement. The speed value can then be output as output information or made available internally for further processing. Furthermore, the control unit records the movement variable of a second sensor, which is also installed on the vehicle, preferably on a rigid element that moves only with the vehicle in the direction of travel or longitudinally. The sensor variables of the first and second sensors can be recorded by the control unit at separate inputs.Optionally, the control unit can also be configured to have only one input for recording the sensor values ​​of both sensors. However, it is important to ensure that the sensor values ​​are coded so that the control unit can identify and assign the different sensor values. It is also possible for one input to be controlled, allowing the control unit to specifically query and / or record the sensor values ​​of both sensors separately.

[0015] Further advantages emerge from the following description of embodiments and from the dependent patent claims. Short description of the drawings

[0016] In the Figure 1 A control unit is schematically provided which carries out a method according to the invention according to the flow chart of Figure 2 executes. Embodiments of the invention

[0017] The following exemplary embodiment illustrates the invention for determining the speed value of a bicycle, in particular an electric bicycle. However, it should be clarified that the application of the invention is not limited to determining the speed value of a bicycle. Rather, the invention is intended to apply to any speed determination of any vehicle based on a time interval between two sensor values.

[0018] In the block diagram of the Figure 1 a control unit 100 is shown which carries out the method according to the invention, as it is shown in the flow chart of the Figure 2described. To determine the speed value, the control unit 100 detects the sensor signals of a particular external first sensor 120. This first sensor 120 can, for example, be a magnetic field sensor and detect the sensor signals of a magnet on a wheel of the bicycle that rotates around the wheel axis as the bicycle moves forward. The magnet moves closer to and further away from the magnetic field sensor, resulting in a characteristic signal curve, with the frequency of the sine curve representing a measure of the rotational movement of the wheel. The speed of the bicycle can therefore be derived from knowledge of the circumference. To detect the frequency of the sine curve, a first threshold value SW 1 is usually used, which can be stored in the memory 110 of the control unit 100 and with which the signal magnitude of the first sensor 120 or the magnetic field sensor is compared.The frequency of the wheel movement is detected by determining the time interval between the first threshold value SW 1 being exceeded twice by the detected sensor variable. Since the magnetic field sensors used for this purpose usually have only limited spatial detection, complete sinusoidal waveforms of the magnetic field are typically not detected, but instead individual pulses with a width that depends on the length of the magnet and the rotational movement of the wheel. In this case, the time interval between two pulses is detected by comparing the sensor variable of the first sensor 120 with the first threshold value SW 1 and determining the time interval between the first threshold value SW 1 being exceeded by two consecutively detected sensor variables.The speed value thus derived can be forwarded to a further processing unit 150, for example for controlling an electric motor of an electric bicycle, forwarded to a display device 160 or used internally for regulation or control purposes.

[0019] However, disturbances in the magnetic fields may result in the magnetic field sensor only being able to detect a reduced magnetic field of the magnet, so that the signal value detected in this way no longer exceeds the first threshold value SW 1. In order to take such disturbances into account and to improve the quality of the speed value determination, provision is made for the detection of an alternative movement variable to create a possibility of adapting the detection to a reduced signal strength. For this purpose, an acceleration sensor 130 or an inertial sensor 140 detects a movement variable that represents the movement of the bicycle in the direction of travel or in the longitudinal direction. The acceleration sensor 130 or the inertial sensor 140 can be provided on the frame or in a component on the bicycle, e.g. in a display and / or control unit on the handlebars.It is also possible for the locomotion variable to be generated by the sensors in a mobile device and made available to the control unit 100. Such mobile devices can, for example, be temporarily attached to the handlebars in the form of a smartphone or carried by the rider. Based on the locomotion variable thus detected, the method in the control unit 100 can estimate a time period within which, after the first sensor variable exceeds the first threshold value SW 1, the same threshold value is to be expected to be exceeded by a second sensor variable if there is no significant change in the bicycle's speed. If it is determined that no such exceedance occurs after this time period, optionally within a predeterminable period of time, a lower second threshold value SW 2 is set for the subsequent determination of the speed value.

[0020] The flowchart of the Figure 2represents a possible method for determining the second threshold value SW 2 in an exemplary embodiment. In a first step 200, a first exceedance of a first threshold value SW 1 is detected by a corresponding first sensor variable, for example in the form of a pulse or signal values ​​from a magnetic field sensor. In the next step 220, an alternative movement variable of the bicycle is detected, for example in the form of a locomotion variable from an acceleration sensor or an inertial sensor. From the locomotion variable, the time period in which a second exceedance of the first threshold value SW 1 would be expected by a second sensor variable from the first sensor can be estimated. In order to take into account any changes in speed during the detection of the first and second sensor variables, the time period can be shorter than the expected value for the second exceedance to occur.Alternatively, a period of time can be estimated in which the exceedance by the second sensor variable is to be expected, depending on plausible speed changes. It is conceivable that, depending on the speed change and vehicle, the minimum and maximum time are selected such that a speed change of 1 m / s, 2 m / s, 5 m / s or 10 m / s is assumed. The estimated time period or period can be determined in step 220 or in the subsequent comparison step 240. In comparison step 240, a check is carried out to determine whether, after the determined time period or within the determined period, a second sensor variable of the first sensor 120 is detected that exceeds the first threshold value SW 1.If a second exceedance of the first threshold value SW 1 by the second sensor variable is detected here, the method continues in step 280 with the determination of the speed value based on the time interval between the first and second exceedance of the threshold value SW 1 by the corresponding sensor variable. However, if it is detected that the second exceedance of the first threshold value SW 1 by the second sensor variable does not occur, it is assumed that the signal strength of the second sensor variable is too small to trigger the exceedance. In this case, a second threshold value SW 2 is set for the further determination of the speed value in the subsequent step 260. This second threshold value SW 2 is selected such that it is lower than the first threshold value SW 1, for example by setting the second threshold value SW 2 as a percentage of the value of the first threshold value SW 1.However, it is also possible to select an absolute value for the second threshold value SW 2 . Optionally, it can also be provided that the intensity distribution of the first and / or second sensor variable is evaluated and the second threshold value SW 2 is selected such that reliable detection of the exceedance is ensured. In the next step 280, the speed value is determined based on the first and second sensor variables or the time interval between the exceedance of the first and / or second threshold value. If both sensor variables exceed the first threshold value SW 1 , the time interval between the two exceedances is used to determine the speed value.If it is detected in step 240 that the second sensor variable does not exceed the first threshold value SW 1, the time interval is determined based on the first sensor variable exceeding the first threshold value SW 1 and the second sensor variable exceeding the second threshold value SW 2. Optionally, it can also be provided that if at least one of the two sensor variables does not exceed the first threshold value SW 1, only the second threshold value SW 2 is used for all subsequent determinations of the time interval and for determining the speed value. The method can then be terminated or repeated with the detection of the first sensor variable in step 200, optionally with the reduced second threshold value SW 2.

[0021] In a further development of the invention, it can be provided that a check is carried out to determine whether the second threshold value SW 2 has been sufficiently reduced to detect the exceedance by the first and / or second sensor variable. Thus, it can be provided that after the second threshold value SW 2 has been used in step 200 and step 240 to determine the time interval between the two sensor variables, it is recognized that at least one of the two sensor variables for determining the time interval and thus for determining the speed value does not exceed the new, lower second threshold value SW 2. In this case, it can be provided to further reduce the second threshold value SW 2. This can be done, for example, in the determination in step 260.

[0022] Optionally, it can also be provided to increase the second threshold value SW 2 again, for example up to the value of the first threshold value SW 1 . For this purpose, a check can be carried out in step 240, 260 or 280 as to whether the first and second sensor variables exceed both the lower second threshold value SW 2 and the higher first (initial) threshold value SW 1. If it is detected that the signal strength of the first and second sensor variables is sufficiently high again, the threshold value used for deriving the time interval can be set back to the first threshold value SW 1 in step 280, step 200 or step 240. Optionally, it can also be provided that the resetting to the original first threshold value SW 1 only takes place when, in at least two consecutive determinations of the time interval, both sensor variables exceed the first threshold value SW 1 in order to rule out only a short-term improvement in the signal strength.

[0023] The increase or decrease of the second threshold value SW 2 can also occur depending on the detection of a measure that reflects the difference between the signal strengths of the sensor variables, in particular their maximum values, and the threshold values. In this case, if the corresponding threshold value is positively exceeded, an increase of the second threshold value SW 2 can be provided depending on the difference thus detected, for example in step 280. Similarly, if the difference between the threshold value and the signal strength of the sensor variable is negative, a decrease or decrease of the second threshold value SW 2 can be provided, for example depending on the detected difference.

[0024] It should be noted that by detecting the speed in the form of two sensor variables using the first sensor 120, a time-averaged speed value is determined that is subject to smaller fluctuations than a speed value derived from the locomotion variable using the second sensor 130 or 140. A less fluctuating value is particularly helpful for controlling the drive based on this speed value, since, among other things, the motor control system exhibits a certain inertia, which could only react to rapid speed changes with effort and increased wear.

Claims

1. Method for determining a speed value of a vehicle, in particular a two-wheeled vehicle, wherein the method • uses a first sensor (120) to capture at least a first and a second sensor variable on the basis of the movement of a wheel of the vehicle, • determines the speed value from the time interval between the first and second sensor variables, wherein, in order to determine the time interval, the first and second sensor variables are compared with a first threshold value (SW1), characterized in that the method • uses a second sensor (130, 140) to capture a progressive movement variable representing the movement of the vehicle in the direction of travel, and • determines a time period on the basis of the progressive movement variable, wherein the time period within which the first threshold value is expected to be exceeded by the second sensor variable after the first threshold value has been exceeded by the first sensor variable, and • defines a second threshold value (SW2) that is lower than the first threshold value (SW1) if no second sensor variable that exceeds the first threshold value (SW1) is captured after the first sensor variable has been captured and the time period has expired, and • in order to determine the time interval and to determine the speed value, compares at least one of the first and second sensor variables with the second threshold value (SW2).

2. Method according to Claim 1, characterized in that the method • determines an expected time interval between the first and second sensor variables on the basis of the progressive movement variable, and • determines the time period on the basis of the expected time interval, wherein provision is made, in particular, for the time period to be shorter than the expected time interval between the first and second sensor variables.

3. Method according to one of the preceding claims, characterized in that the second threshold value (SW2) is defined as a percentage reduction of the first threshold value (SW1).

4. Method according to one of the preceding claims, characterized in that, in a further step, the method further reduces the second threshold value (SW2) if no second sensor variable that exceeds the previous second threshold value (SW2) is captured after the first sensor variable has been captured and the time period has expired.

5. Method according to one of the preceding claims, characterized in that the method captures further first and second sensor variables after defining the second threshold value (SW2), wherein the speed value is determined on the basis of the time interval of the exceeding of the second threshold value (SW2) by the first and second sensor variables, in particular if the first and / or second sensor variable does not exceed the first threshold value (SW1).

6. Method according to Claim 5 or 6, characterized in that, when comparing the first and second sensor variables with the second threshold value (SW2), the difference between the sensor variable and the second threshold value (SW2) is determined, wherein the second threshold value (SW2) • is increased if the difference exceeds a predefined first value or • is reduced if the difference falls below a predefined second value.

7. Method according to one of the preceding claims, characterized in that the method assigns the value of the first threshold value (SW1) to the second threshold value (SW2) if, after defining a second threshold value (SW2) lower than the first threshold value (SW1), the first and second sensor variables exceed both the lower, second threshold value (SW2) and the higher, first threshold value (SW1).

8. Device for determining a speed value of a vehicle, in particular a two-wheeled vehicle, wherein the vehicle comprises a wheel and a first sensor (120), which is configured to capture a first and a second sensor variable on the basis of the movement of a wheel of the vehicle, wherein the vehicle further has a second sensor (130, 140), which is configured to capture a progressive movement variable representing the movement of the vehicle in the direction of travel, wherein the device has a control unit (100) which is configured to perform a method according to one of Claims 1 to 7, wherein the control unit is designed such that • at least a first and a second sensor variable of a first sensor (120) are captured on the basis of the movement of a wheel of the vehicle, • the speed value is determined from the time interval between the first and second movement variables, wherein, in order to determine the time interval, the first and second sensor variables are compared with a first threshold value (SW1), • wherein the first and / or second movement variable is captured by means of a magnetic field sensor (120), and • the progressive movement variable is captured by means of an acceleration sensor (130) or an inertial sensor (140), characterized in that the control unit (100) • uses a second sensor (130, 140) to capture a progressive movement variable representing the movement of the vehicle in the direction of travel, and • determines a time period on the basis of the progressive movement variable, and • defines a second threshold value (SW2) that is lower than the first threshold value (SW1) if no second sensor variable that exceeds the first threshold value (SW1) is captured after the first sensor variable has been captured and the time period has expired, and • in order to determine the time interval and to determine the speed value, compares at least one of the first and second sensor variables with the second threshold value (SW2).

9. Vehicle, in particular a two-wheeled vehicle, having a device according to Claim 8 and / or a control unit (100), configured to perform the method according to one of Claims 1 to 7 and to output the speed value thus determined, wherein the vehicle at least • has a magnetic field sensor (120) which captures a magnetic field of a magnet located in or on one of the wheels rotating in the progressive movement, and • has an acceleration sensor (130) and / or an inertial sensor (140) which captures the movement of the vehicle in the direction of the progressive movement direction and / or the longitudinal direction of the vehicle.