METHOD FOR DETERMINING A CADENCE OF A BICYCLE

Description

State of the art

[0001] The present invention relates to a method for determining a cadence of a bicycle, and to a bicycle.

[0002] It is well known to record cadence on bicycles using dedicated sensors. For example, a standard revolution sensor, such as a reed sensor, can be used. Cadence can be recorded for purely informational purposes, for example, to accurately display relevant information to the rider from a sporting perspective. It is also known, particularly for electric bicycles, which have a drive unit that supports the rider's torque generated by the rider using motor power, to control the provision of motor torque depending on various parameters, including cadence. Disclosure of the invention

[0003] The method according to the invention with the features of claim 1 is characterized in that a particularly simple and cost-effective possibility is created to precisely determine a cadence on a bicycle.

[0004] In particular, additional sensors for recording the cadence can be dispensed with. This is achieved according to the invention by a method for determining the cadence of a bicycle, preferably an electric bicycle, comprising the steps: Determining a movement signal that represents a temporal progression of the bicycle's movement, determining a frequency spectrum of the movement signal, and determining a cadence based on the determined frequency spectrum, checking the plausibility of the determined movement signal using the determined cadence, in particular based on a previously known gear ratio of a bicycle drive, determining a phase offset between the movement signal and a torque signal that represents a momentary driver torque or a total torque.

[0005] In other words, the method records a temporal progression of movement, such as a bicycle speed, for example using a speed sensor. This is preferably done using a high temporal resolution, which in particular is a multiple of a maximum expected cadence that a bicycle rider typically pedals. The current speed is represented, for example, by the movement signal. This movement signal is analyzed in the method with regard to its frequency spectrum. In particular, characteristic frequency components of the movement signal can be determined. The current cadence at which a bicycle rider operates the pedals is then determined based on the frequency spectrum.

[0006] In particular, the determination of cadence is based on the assumption that while the rider is pedaling, the current speed fluctuates depending on the pedaling torque currently applied by muscle power. The pedaling torque depends in particular on the current pedal position. This means that if, for example, the pedals are horizontal, the rider pedals with maximum pedaling force, so that in this position the maximum pedaling torque is present, whereas if the pedals are vertical, the rider applies less pedaling force to the pedals, so that in this position the minimum pedaling torque is present. These fluctuations in pedaling torque affect the acceleration and thus subsequently the speed of the bicycle. By analyzing the movement signal accordingly using the method, the current cadence can be determined in a particularly simple and reliable manner.This also offers further advantages. For example, if an additional cadence sensor is present, the cadence signal recorded by it can be validated. Furthermore, a speed signal can be validated, for example, by additionally determining the cadence, which allows both parameters to be checked for plausibility.

[0007] The subclaims show preferred developments of the invention.

[0008] Preferably, the method further comprises the step of determining a characteristic frequency of the frequency spectrum of the movement signal. The cadence is determined based on the determined characteristic frequency. A dominant frequency range of the frequency spectrum is considered a characteristic frequency, i.e., a frequency that is particularly dominant when the frequency spectrum is broken down into its individual frequency components. This allows the frequency to be determined particularly simply and reliably based on the detected speed.

[0009] Particularly preferably, the cadence is determined as half the characteristic frequency. This means that the cadence is determined based on the assumption that, for each complete pedal revolution, each of the two pedals is positioned exactly once, for example, in the vertical pedal position where the maximum rider torque is applied.

[0010] Preferably, the frequency spectrum is determined using a fast Fourier transform (FFT). This allows for a particularly simple and efficient analysis of the movement signal with regard to its characteristic frequency components in order to determine the frequency spectrum and derive the cadence from it.

[0011] The movement signal further preferably comprises a speed signal. The speed signal is preferably determined using a speed sensor. The speed sensor is preferably a reed sensor, in particular one designed as a magnetic sensor. The reed sensor preferably generates a signal pulse for each revolution of a wheel of the bicycle, wherein the speed can be determined based on the frequency of the signal pulses and a wheel circumference of the wheel. Alternatively or additionally, the speed signal is preferably determined using an anti-lock sensor of an anti-lock braking system of the bicycle, for example using a tonewheel. This makes it possible to provide a particularly high temporal resolution of the speed and thus a particularly precise determination of the cadence.

[0012] The movement signal preferably comprises an acceleration signal. The acceleration signal is preferably determined using an acceleration sensor, in particular an inertial sensor. In particular, the acceleration sensor can detect an acceleration in the longitudinal direction, i.e., for example, in the direction of travel, and / or an acceleration of a rolling movement. Rolling movement is therefore considered, in particular, an inclination around the longitudinal axis, which is aligned in the direction of travel. This can also provide a high temporal resolution and a precise determination of the cadence.

[0013] Preferably, the method further comprises the steps: Determining a sensor cadence using a cadence sensor, and validating the cadence sensor based on a comparison of the determined cadence and the determined sensor cadence. For example, the cadence sensor can be a revolution sensor configured to detect a frequency of a pedal revolution during pedal actuation. In other words, the sensor-based cadence signal of the cadence sensor, and thus the correct function of the cadence sensor, is validated by redundantly determining the cadence.

[0014] The method according to the invention further comprises the step of checking the plausibility of the determined movement signal using the determined cadence. In particular, the plausibility check is carried out based on a previously known, for example current, gear ratio of a bicycle drive. In particular, the gear ratio is regarded as the overall gear ratio between a pedal drive and a rear wheel of the bicycle. In other words, if the current gear ratio is known, a conversion between speed and cadence can be carried out. For example, a corresponding expected target cadence can be calculated based on the detected speed and the gear ratio. By additionally determining the cadence based on the frequency spectrum of the movement signal, a match orA deviation in the correspondingly determined cadence can be detected in order to easily and reliably verify the plausibility of the speed detection. For example, a deviation between the cadence values ​​determined from the speed and cadence sensor can also be interpreted as an incorrect speed detection, assuming the cadence sensor is functioning correctly, which can be used primarily to detect tampering.

[0015] Particularly preferably, the method further comprises the step of detecting manipulation of the motion signal in response to a determined implausibility of the motion signal. This means that if, when checking the plausibility of the motion signal based on the cadences, it is determined that an implausibility exists, particularly regarding the respective frequencies, it can be concluded that the motion signal has been manipulated. This is particularly advantageous in the case of electric bicycles, as it can prevent, for example, misuse of the manipulated speed detection.

[0016] The method according to the invention further comprises the step of determining a phase shift between the movement signal and a torque signal representing a current rider torque, or preferably between a movement signal and the total torque from the measured rider torque and the set motor torque. The torque signal can preferably be detected using a torque sensor. This allows further advantageous information about the current riding state of the bicycle to be obtained based on the movement signal. In particular, the phase shift is representative of an elasticity and / or an inertia of the drive train, i.e., a measure of the directness of the power transmission. For example, with higher elasticity, the phase shift is greater, i.e., the speed signal lags the torque signal even further.

[0017] Preferably, the plausibility check of the determined motion signal is additionally performed based on the determined phase shift. For example, in the case of an unexpected, i.e., implausible, phase shift, manipulation of the speed signal can also be detected. In this case, for example, the determined phase shift can be compared with a predetermined reference value and / or with calibration data and / or with a lookup table to check the plausibility of the phase shift.

[0018] Furthermore, the invention leads to a method for operating a drive unit of an electric bicycle. The drive unit is particularly configured to provide a motor-assisted motor torque to a rider torque generated by the muscular power of the rider of the electric bicycle. Particularly preferably, the motor torque is generated as a function of the riding parameters of the electric bicycle, in particular at least partially based on the current speed of the electric bicycle. Preferably, the motor torque is generated only up to a predetermined maximum speed. The method for operating the drive unit comprises the following steps: Determining the cadence of the electric bicycle using the method described above for determining the cadence of a bicycle, and actuating the drive unit depending on the determined cadence. In particular, the generated motor torque is regulated depending on the determined cadence. This allows the drive unit to be controlled in a particularly simple, efficient, and precise manner. The specific determination of the cadence using the method according to the invention offers the particular advantage that manipulation of the motor support, for example, so-called "tuning," can be easily and effectively detected and / or prevented.

[0019] Preferably, the method further comprises the step of deactivating the drive unit in response to a detected manipulation of the motion signal, which can preferably be detected, as described above, in response to a detected implausibility of the motion signal. This means that, in the event of a detected manipulation of the motion signal, the drive unit is prevented from generating a motor torque.

[0020] The invention further relates to a bicycle comprising a speed sensor and / or an inertial sensor system for generating a speed signal representing a current speed of the bicycle, and a control unit. The bicycle is preferably an electric bicycle, which preferably further comprises a drive unit. In this case, the control unit is preferably further configured to operate the drive unit in a controlled manner. The control unit is configured to carry out the described method for determining a cadence and / or the described method for operating a drive unit. Short description of the drawings

[0021] Embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing: Figure 1 shows a simplified schematic view of a bicycle in which a method for determining a cadence according to a preferred embodiment of the invention is carried out, Figure 2 shows a simplified representation of exemplary time courses of sensor signals which are used in carrying out the method according to the preferred embodiment, Figure 3 shows an exemplary time course of a speed signal which is used in carrying out the method according to the preferred embodiment, Figure 4 shows an exemplary frequency spectrum of the speed signal of the Figure 3 which is used in carrying out the method according to the preferred embodiment, and Figure 5 shows exemplary time courses of a filtered torque signal and a filtered speed signal which are used in carrying out the method according to the preferred embodiment. Embodiments of the invention

[0022] Figure 1 shows a simplified schematic view of a bicycle 100. The bicycle 100 is an electric bicycle comprising a drive unit 102, which is designed as an electric motor. The drive unit 102 is arranged in the region of a bottom bracket of the bicycle 100 and is provided to assist a rider of the bicycle 100's manual pedaling force, applied via a crank drive 104, with a torque generated by an electric motor.

[0023] The bicycle 100 further comprises an electrical energy storage device 109, by means of which the drive unit 102 can be supplied with electrical energy. A control unit 108 is also integrated into the drive unit 102.

[0024] The control unit 108 is configured to actuate the drive unit 102 in response to pedaling by a rider of the bicycle 100. In detail, the drive unit 102 is actuated in a controlled manner such that a motor torque is generated as a function of a rider torque generated by the rider's muscle power, in order to provide motor assistance to the rider during pedaling. Provision is made for the generation of the motor torque to be controlled as a function of the rider torque level. Furthermore, the actuation of the drive unit 102 can depend on other parameters, such as a cadence.

[0025] In addition, the drive unit 102 is only activated up to a predetermined maximum speed, preferably 25 km / h. If the predetermined maximum speed is exceeded, the generation of engine torque by the drive unit 102 is stopped, for example, by deactivating the drive unit 102.

[0026] During operation of the drive unit 102, the method for determining a cadence of the bicycle 100 according to the preferred embodiment of the invention is carried out. The cadence thus determined can be used to easily and reliably detect and, for example, counteract any manipulation of the speed-dependent control of the drive unit 102. This is described in detail below.

[0027] In the method, a speed signal 2 is first determined using a speed sensor 103. In the described preferred embodiment, the speed sensor 103 is an anti-lock sensor of an anti-lock braking system 110 of the bicycle 100. This allows the speed signal 2 to be detected particularly precisely and with high temporal resolution. Alternatively or additionally, the speed signal 2 can preferably be detected using a reed sensor as a speed sensor.

[0028] An example curve for a recorded speed signal 2 is shown in the Figure 2 and 3 For example, in Figure 2 below and in Figure 3 the speed 54 is shown as a function of time 55.

[0029] Subsequently, the method determines a frequency spectrum 20 of the speed signal 2. The frequency spectrum 20 is determined by means of a fast Fourier transformation. The frequency spectrum 20 of the speed signal of the Figure 3 , that is, a function of the frequency 75 of certain occurring frequencies 56 in the speed signal 2, is in Figure 4 shown.

[0030] As in Figure 4 As can be seen, there is a peak in the frequency distribution at a characteristic frequency 10. Half of this characteristic frequency corresponds to the cadence to be determined, with which the rider of the bicycle 100 pedals.

[0031] This determination is based on the assumption that the instantaneous speed of the bicycle 100 fluctuates due to the rider's pedaling. The corresponding pedaling torque applied during pedaling depends in particular on the current pedal position. This means that with a horizontal pedal position, the maximum pedaling force of the rider in this position generates the maximum pedaling torque, while in a vertical position, the lowest pedaling torque is generated.

[0032] Such a fluctuating torque curve is also in the Figure 2 can be seen, in which a torque signal 3 representing the torque curve is shown in the top diagram. Here, the instantaneous driver torque 51 is shown as a function of time 55.

[0033] Using the determined cadence, the speed signal 2, which is detected by the speed sensor 103, can then be checked for plausibility. In particular, this can be done depending on a current, previously known gear ratio of a drive of the bicycle 100. Using the previously known gear ratio, an expected current speed can be calculated, for example, based on the determined cadence. By comparing the speed calculated in this way with the current speed of the speed signal 2, the speed signal 2 can be validated. If the speed signal 2 is implausible, this can be used to conclude, for example, that the speed detection has been manipulated.If such manipulation is detected, further measures can be taken, such as deactivating the drive unit 102, in order to reliably prevent motor assistance above the predetermined maximum speed.

[0034] Furthermore, the cadence determined based on the speed detection can be used to validate a dedicated cadence sensor 107 in a particularly simple and cost-effective manner.

[0035] A further optimization of the method can be achieved by additionally detecting the torque signal 3, which represents the current driver torque. A phase offset 30 can be determined between the determined speed signal 2 and the torque signal 3, as shown in Figure 2 The phase shift 30 is also shown using the Figure 5which shows a filtered torque signal 51c and a filtered speed signal 54c.

[0036] This phase shift 30 results from mechanical and / or climatic relationships of the power transmission between the pedal actuation by the rider's muscle power and the drive on the rear wheel of the bicycle 100. For example, this entire phase shift 30 is divided into several individual phase shifts, as described below.

[0037] In the second diagram of the Figure 2 A total torque curve 52a is shown, which represents a total torque 52, which is a sum of the driver torque 51 and a generated motor torque of the drive unit 102, over time 55. A first phase offset 52b results between the torque signal 3 and the total torque curve 52a due to torque filtering in the motor control of the drive unit 102.

[0038] In the third diagram of the Figure 2 An acceleration curve 53a is shown, which indicates an acceleration 53 of the bicycle 100 as a function of time 55. Between the total torque curve 52a and the acceleration curve 53a, a second phase shift 53b results due to inertia and / or elasticity and frictional influences in the drive train of the bicycle 100.

[0039] Furthermore, Figure 2 a third phase offset 54b between the acceleration curve 53a and the speed signal 2, which results from the physical relationship of the lag of the speed with respect to the acceleration.

[0040] This results in the total phase offset 30 between the torque signal 3 and the speed signal 2.

[0041] Based on the corresponding determination of the phase shift 30 and the previously known mechanical and kinematic properties of the drive of the bicycle 100, the determined speed signal 2 can also be checked for plausibility. For example, this can be done by comparing the determined phase shift 30 with an expected phase shift, which can be calculated, specified as a predetermined value, or determined from a table.

Claims

1. Method for determining a cadence of a bicycle (100), in particular an electric bicycle, comprising the following steps: - determining a movement signal (2) representing a time profile of the locomotion of the bicycle (100), - determining a frequency spectrum (20) of the movement signal (2), and - determining a cadence based on the determined frequency spectrum (20), the method being characterized by - checking the plausibility of the determined movement signal (2) by means of the determined cadence, in particular based on a previously known transmission ratio of a drive of the bicycle (100), - determining a phase offset (30) between the movement signal (2) and a torque signal (3) representing an instantaneous torque applied by the cyclist or an overall torque.

2. Method according to Claim 1, further comprising the following step: determining a characteristic frequency (10) of the frequency spectrum (20) of the movement signal (2), wherein the cadence is determined based on the determined characteristic frequency (10).

3. Method according to Claim 2, wherein the cadence is determined as half the frequency of the characteristic frequency (10).

4. Method according to any one of the preceding claims, wherein the frequency spectrum (20) is determined by means of a fast Fourier transformation.

5. Method according to any one of the preceding claims, wherein the movement signal (2) includes a speed signal (2), and wherein the speed signal (2) is determined by means of a speed sensor (103), in particular a reed sensor and / or an anti-lock sensor.

6. Method according to any one of the preceding claims, wherein the movement signal (2) includes an acceleration signal (2), and wherein the acceleration signal (2) is determined by means of an acceleration sensor, in particular an inertial sensor system.

7. Method according to any one of the preceding claims, further comprising the following steps: - determining a sensor cadence by means of a cadence sensor (107), and - validating the cadence sensor (107) based on a comparison of the determined cadence and the determined sensor cadence.

8. Method according to any one of Claims 1 to 7, further comprising the following step: - determining a manipulation of the movement signal (2) in response to a determined implausibility of the movement signal (2).

9. Method according to any one of Claims 1 to 8, wherein the plausibility is additionally checked based on the determined phase offset (30).

10. Method for operating a drive unit (102) in an electric bicycle (100), comprising the following steps: - determining a cadence of the electric bicycle (100) by means of a method according to any one of the preceding claims, and - actuating the drive unit (102) depending on the determined cadence.

11. Method according to Claim 10, further comprising the following step: - determining a manipulation of the movement signal (2) in response to a determined implausibility of the movement signal (2), - deactivating the drive unit (102) in response to a detected manipulation of the movement signal (2).

12. Bicycle, in particular electric bicycle, comprising: - a speed sensor (103) and / or an inertial sensor system for generating a movement signal (2) representing a time profile of the locomotion of the bicycle (100), and - a control unit (108) which is configured to carry out a method according to any one of the preceding claims.