Device, system and method for generating a pedal crank-dependent torque for a pedelec, computer program product and pedelec

Abstract

Device (20) for generating a pedal crank-dependent motor torque for a drive motor (40) of a pedelec, comprising a torque interface (22) for receiving a torque signal with information about a pedaling torque generated by a rider of the pedelec; an angle interface (24) for receiving an angle signal with information on a rotation angle of a pedal crank of the pedelec; an evaluation unit (26) for determining a motor torque for the drive motor (40) based on the torque signal, the angle signal and a predetermined correction curve (50) such that the torque signal is corrected with the correction curve and a characteristic value is formed and the motor torque is essentially proportional to the characteristic value; an output interface (28) for outputting a control signal for the drive motor (40) based on the determined motor torque.

Description

[0001] The present invention relates to a device for generating a pedal crank-dependent motor torque for a drive motor of a pedelec, a system for generating a pedal crank-dependent motor torque and a corresponding method.

[0002] Bicycles, especially two-wheelers, electric bicycles, pedelecs, speed pedelecs, cargo motorcycles with or without electric drive, etc., are becoming increasingly complex and are being used for ever-expanding applications, especially in the area of ​​electrically powered bicycles. At the same time, riders' demands for comfort and assistance from the electric drive or auxiliary motor are becoming ever higher. Riders want to ride as comfortably and efficiently as possible while experiencing the best possible assistance. At the same time, suitable and adapted assistance should also increase the range achievable with a single battery charge.

[0003] Current pedelecs often use torque sensors to measure the pedaling torque applied by the rider. To achieve the most consistent assistance response from the pedelec, the input signal is smoothed using a low-pass filter when using only one torque sensor. However, the use of a low-pass filter has the disadvantage of degrading the dynamics. A rapid increase or decrease in torque, such as that generated when starting off, is only transmitted to the motor control with a delay. This type of assistance response is therefore undesirable.

[0004] It is known from the prior art that with a pedelec, the generated and measured pedal torque of the rider depends heavily on the pedal position, i.e. the angle of rotation of the pedal crank. If the pedal crank is vertical, the rider can only generate little torque despite exerting great force, as the corresponding lever arm of the crank is almost zero. To ensure a consistent assistance curve, the measured value of the rider torque is often time-smoothed using the low-pass filter described above. However, this impairs the signal dynamics. In addition, starting off is made more difficult in unfavorable pedal or pedal crank positions, as in these positions only a maximum of approximately a quarter of the pedal torque can be generated, as would be possible with an almost horizontal pedal or horizontal crank.

[0005] DE 10 2014 218 683 A1 discloses a method in which the assistance provided by the auxiliary motor is adapted to the rider's pedaling behavior. The rider's pedaling angle and the pedaling angle-dependent pedaling torque are taken into account. The pedaling torque applied by the motor is adjusted such that a constant total torque is applied to the drive wheel. This ensures that the drive wheel experiences a constant torque. This should result in the most "smooth pedaling" possible. However, the auxiliary torque applied by the auxiliary motor constantly fluctuates, meaning that sometimes complex control methods must be used, and the motor is constantly subjected to varying loads. In order to achieve a constant total torque, the torque applied by the drive motor must therefore be constantly fluctuating. This leads to a reduced efficiency of the motor.

[0006] DE 10 2021 211 270 B3 relates to a method for controlling an electric motor of an electric bicycle. The input torque and crank cadence are recorded at different times to determine the temporal changes in these values. These changes are used to calculate a base torque used to control the electric motor.

[0007] DE 10 2009 000 919 A1 relates to a method for controlling an electric motor of an electric bicycle. The desired drive assistance is determined by dynamically evaluating the pedal crank speed, without requiring an actual measurement of the pedal force or torque.

[0008] The object of the present invention is to propose an approach for providing the rider with a pedal-crank-dependent motor torque, thus creating the most natural riding behavior possible for the rider. This object is achieved by the subject matter having the features of the independent patent claims.

[0009] To achieve this object, the present invention relates in a first aspect to a device for generating a pedal crank-dependent motor torque for a drive motor of a pedelec, comprising a torque interface for receiving a torque signal containing information about a pedaling torque generated by a rider of the pedelec; an angle interface for receiving an angle signal with information on a rotation angle of a pedal crank of the pedelec; an evaluation unit for determining a motor torque for the drive motor based on the torque signal, the angle signal and a predetermined correction curve such that the torque signal is corrected with the correction curve and a characteristic value is formed and the motor torque is substantially proportional to the characteristic value; an output interface for outputting a control signal for the drive motor based on the determined motor torque.

[0010] In another aspect, the present invention relates to a system for generating a pedal crank-dependent motor torque for a drive motor of a pedelec, comprising: a device as described above; a torque sensor arranged on the pedelec for determining the pedaling torque; a sensor arranged on the Pedelec for determining the angle of rotation of a pedal crank of the Pedelec.

[0011] Further aspects of the invention relate to a method configured according to the device, as well as to a computer program product with program code for performing the steps of the method when the program code is executed on a computer. Furthermore, one aspect of the invention relates to a storage medium on which a computer program is stored which, when executed on a computer, effects execution of the method described herein.

[0012] The method and the computer program product can be implemented according to the embodiments described for the device and the system in the dependent claims.

[0013] According to the invention, a torque signal comprising information on a pedaling torque generated by a rider of a pedelec is received at a torque interface. According to the invention, an angle signal comprising information on a rotational angle of the pedal crank of the pedelec is received at the device via an angle interface. The rotational angle is the angular position of the pedal crank. Based on the torque signal and the angle signal as well as based on a predetermined correction curve, the torque signal is corrected and a characteristic value is formed. This can be done, for example, by division. Thus, a corrected pedal torque is determined or calculated. From this, a motor torque is determined or calculated. This motor torque is essentially proportional to the characteristic value and thus to the corrected pedal torque.The corrected pedal torque is characterized by its low ripple and its essentially uniform or constant nature. The same applies to the motor torque to be generated or the control signal.

[0014] For example, the correction curve incorporates data on a typical manually generated pedaling torque curve of a cyclist. The correction curve is also angle-dependent, meaning it is a curve across the angle of rotation of the pedal crank, from 0° to 360°. The correction curve thus takes into account that the torque curve fluctuates greatly across the angle of rotation during a cyclist's pedaling motion. The maximum torque is often almost twice as large as the average torque, averaged over an entire crank revolution.

[0015] By using the correction curve, the rider's pedaling behavior can be taken into account while compensating for the motor torque. This creates a control signal that produces a low-variable or (almost) constant motor torque.

[0016] The characteristic value can be calculated in such a way that, when determining the motor torque to be delivered to the drive motor, the measured torque signal, which reflects the torque or pedaling torque applied by the bicycle, is related to the pedaling torque for the corresponding angle of the pedal crank at which the pedaling torque was measured and to the corresponding value of the correction curve. For example, the measured pedaling torque can preferably be divided by the corresponding torque value of the correction curve (i.e., always at the same angle of rotation). This means that the fluctuation in pedaling torque caused by the position of the pedal crank has little or no influence on the generated motor torque. This makes it possible to achieve a motor torque with relatively low fluctuations. The rider's natural pedaling sensation is retained even when supported by the auxiliary motor or the pedelec's drive motor.

[0017] Determining the motor torque results in a control signal that controls the pedelec's drive motor to generate a torque at the drive motor that corresponds to the determined motor torque. It is advantageous that only one control signal is generated. Closed-loop control, i.e., feedback of the actual motor torque delivered by the drive motor to the determination of the motor torque for the next pedaling angle, is not necessary. This eliminates the need to monitor the motor torque of the drive motor and feed it back to the evaluation unit. This results in a very robust and reliable determination of the torque. The evaluation unit can therefore be designed accordingly cost-effectively.

[0018] The device thus recalculates the applied pedal torque (for a particular pedaling angle or rotation angle) by correcting the pedal torque to the average torque during one revolution using correction values ​​from the angle-dependent correction curve. This average torque can be used to calculate or determine the motor torque for the drive motor.

[0019] Of course, other factors can be taken into account for the control signal sent to the drive motor, such as maximum possible actuating torques for the drive motor or similar.

[0020] The device according to the invention has the further advantage that the generated and determined motor torque remains relatively constant and exhibits low ripple. The total torque of the drive motor and rider (pedaling torque) changes essentially with the fluctuation in the pedaling torque applied by the rider. The absolute fluctuation is almost the same and essentially corresponds to the fluctuation in the rider's pedaling torque. However, due to the amplification by means of the pedaling torque generated by the drive motor, the fluctuation or ripple of the applied total torque over one revolution of the crank is, in relative terms, significantly lower. Since the motor torque generated by the motor fluctuates only slightly, the efficiency of the electric motor for the drive is significantly higher. The load on the motor is low, which leads to an increased service life.At the same time, the device reacts very quickly to changes in the pedaling torque generated by the rider, for example, when accelerating or starting off. The device and the system thus exhibit high dynamics, which increases comfort.

[0021] In a preferred embodiment, the evaluation unit of the device is designed to determine the characteristic value from the mean value of the corrected torque signal. In this case, all data of the corrected torque signal, i.e., the pedaling torque, are averaged over the corresponding angles from 0° to 360°. The induced motor torque is then dependent on the mean value of the corrected torque signal curve. If the mean value shifts, this also leads to a shift in the determined motor torque.

[0022] The correction curve is preferably based on empirical data of the pedaling torque generated by a number of cyclists. This measured data can therefore serve as the basis for creating the correction curve. It is also conceivable for the correction curve to be based on measured pedaling torque profiles of the current rider. For example, a history of angle-dependent pedaling torques over a predetermined period can be taken into account and stored in the form of correction curves. The correction curve should best reflect the current pedaling behavior and the progression of the generated pedaling torque. The better this is done, the more constant and uniform the determined characteristic value and thus the required motor torque.

[0023] The device provides that the evaluation unit is designed to determine the correction curve from a correction function. The correction curve is derived from the individual values ​​of the correction curve for an angular range from 0° to 360°. For example, the correction function can be formed from a polynomial function or an angular function. Periodic functions are preferred.

[0024] The evaluation of empirical data and the pedaling torques measured by a number of riders suggests that the correction curve can be described using a sinusoidal correction function. The correction function can thus be based on a sine function of the pedaling angle. Particularly preferably, the correction function can be based on the squared sine function of a pedaling angle.

[0025] In an alternative embodiment, the correction function for describing the correction curve has an adjustment value, a scaling factor and / or an offset value.

[0026] An adjustment value can, for example, be an angular shift in the pedaling angle. This allows for the fact that the maximum pedaling torque is not generated when the crank is in a horizontal position, but rather shortly before or after, for example at an angle between 5° and 10° around the horizontal position. Using a scaling factor, for example, different groups of cyclists can be considered, on whose measured values ​​the correction curve is based. Using an offset value, for example, it can be taken into account that even when the crank is in a horizontal position, the induced pedaling torque is not zero, but that a minimal torque can be induced even in this position.

[0027] By changing the adjustment value, scaling factor, and / or offset value, the correction curve can be modified or optimized before or during operation, for example, to adapt it to a specific driver or driver type. For example, a driver's right-left asymmetry, different foot sizes, or other special features can be taken into account.

[0028] Preferably, the engine torque is determined in the evaluation unit based on a standardized correction curve. Standardization can be achieved, for example, by determining the integral of the correction curve values ​​over the angle divided by the angle.

[0029] In a preferred embodiment, the control signal output at the device's output interface has a small amplitude fluctuation range, considered over a complete 360° rotation of the pedal crank. The fluctuation range (ripple) is preferably at most ± 30%, more preferably at most ± 20%, and more preferably at most ± 10%. In a very preferred embodiment, the fluctuation range is at most ± 5% of the mean value of the control signal. Thus, the drive motor generates a fairly constant drive torque. Due to the angular dependence of the rider's pedaling torque and the relatively uniform drive torque, the total torque fluctuates in a similar way to the pedaling torque, so that the rider experiences a natural riding behavior with the assistance.

[0030] Another preferred embodiment takes into account a rider-selected assistance level when generating the control signal. The control signal output by the output interface is based on the generated motor torque and the assistance level. For example, a support level can specify that the generated motor torque corresponds to twice the characteristic value of the correction curve. Typically, several assistance levels can be selected by the pedelec rider. These typically range from 50% of the generated pedaling torque or the (standardized) average pedaling torque to three or five times the value. Of course, the assistance level can also be taken into account only after the control signal has been generated.

[0031] In a preferred embodiment, the device comprises a storage unit for storing the correction curve, the characteristic value, a standardized correction curve, and / or a histogram of measured torque signals. The empirically measured data can be stored in the storage unit in the form of a correction curve. It is also possible to store a correction function and / or its parameters. It is also possible to measure the rider's pedaling torque over a longer period of time, store it, and use it to create a histogram or an adapted correction curve. Alternatively, a correction function can be stored and then accessed.

[0032] According to the invention, a torque sensor is used to determine the rider's current pedaling torque. Another sensor is used to determine the angle of rotation or the angular position of the pedal crank of the pedelec. In a preferred embodiment, this sensor for determining the angle of rotation can be an absolute angle sensor. In this way, the current angle of rotation or the angular position of the pedal crank can be easily determined. Alternatively, but equally preferred, the sensor for determining the angle of rotation can be a speed sensor. The angle signal can be formed via the integral of the speed sensor. This can, for example, be a pulse generator on the crank or crankshaft. The zero point is determined dynamically via the minima and maxima of the torque sensor. The speed sensor has the advantage of being less expensive than the absolute angle sensor.However, the method is less accurate and doesn't work when stationary. Furthermore, if a steady pedaling motion is interrupted, the measurement is inaccurate or fails.

[0033] A bicycle is understood here to mean, in particular, an e-bike, a pedelec, an electric cargo bike or an S-pedelec. The terms bicycle and pedelec are used synonymously. The predefined correction curve can be predefined in the sense that it is stored in the device or system. However, predefined here also means that it is described, for example, by a stored correction function or is currently determined for the respective angle of the pedal crank from the correction function. The same applies to the characteristic value, which can be predefined, stored or currently calculated. A standardized correction function or curve, usually standardized via the angle, can also be stored directly or determined during operation. This is also understood under the term “predefined”.The predefined correction curve also includes an adaptive adjustment to the respective rider or a pedal asymmetry between the right and left leg caused by the rider or similar.

[0034] The invention is described and explained in more detail below using selected embodiments in conjunction with the accompanying drawings. They show: Fig. 1 is a schematic representation of a system according to one aspect of the present invention; Fig. 2 a representation of an exemplary course of a correction curve and the characteristic value; Fig. 3 a representation of a correction curve in polar coordinates; Fig. 4 a schematic representation of a method according to the invention.

[0035] In Fig. Figure 1 schematically shows a system 10 according to the invention for generating a pedal-crank-dependent motor torque for a drive motor 40 of a pedelec. The system 10 comprises a device 20 arranged on a pedelec, a torque sensor 30 arranged on the pedelec for determining the torque, and a sensor 32 arranged on the pedelec for determining the angle of rotation of a pedal crank of the pedelec. The sensor 32 is preferably an absolute angle sensor 34.

[0036] In Fig. 1 further shows a drive motor 40 of a pedelec, which is coupled to the device 20 of the system 10.

[0037] The device 20 serves to generate a pedal-crank-dependent motor torque for the drive motor 40 of a pedelec. The device comprises a torque interface 22 for receiving a torque signal containing information about a pedaling torque generated by a rider of the pedelec. The torque signal is preferably determined by the torque sensor 30. The device 20 further comprises an angle interface 24 for receiving an angle signal containing information about a rotation angle or an angular position of the pedal crank of the pedelec.

[0038] An evaluation unit 26 of the device 20 serves to determine a motor torque for the drive motor 40. The motor torque is based on the torque signal, the angle signal, and a predetermined correction curve 50. It is determined by correcting the torque signal using the correction curve 50, for example, dividing the values ​​of the torque signal by the values ​​of the correction curve 50, each for the corresponding angle of rotation. This results in a characteristic value that preferably fluctuates little across all angles of rotation, and particularly preferably is constant. The generated motor torque is essentially proportional to the characteristic value (the corrected pedal torque). This characteristic value can, for example, be an average value.

[0039] A control signal based on the determined motor torque is output to the drive motor 40 via an output interface 28. This control signal controls the drive motor so that the generated motor torque is superimposed on the rider's pedaling torque. Since the motor torque is essentially constant, exhibiting only minor fluctuations with a fluctuation range of preferably ± 10% around its mean value, a total torque results that essentially follows the pedaling torque but is amplified by the drive motor 40. This results in an essentially natural pedaling sensation for the rider.

[0040] Of course, it is possible for the torque interface 22 and the angle interface 24 to be integrated into a common interface. Furthermore, the device 20 can have additional interfaces if additional signals are to be processed. For example, two torque sensors could be provided so that the torque can be measured at each of the two cranks of the pedelec.

[0041] Optionally and preferably, the device 20 comprises a storage unit 29 for storing a correction curve 50, a characteristic value of the correction curve 50, a standardized correction curve 50, and / or a histogram of measured torque signals. The curves can be predefined curves, for example. It is also possible for a correction function to be stored in the storage unit 29, from which, for example, a correction curve 50 can be generated in real time. Likewise, additional values ​​can be stored, saved, or temporarily stored in the storage unit, for example, an offset value or other scaling or adjustment factors.

[0042] Fig. Figure 2 shows a schematic representation of a correction curve 50 on which the determination of the motor torque can be based. The function is represented by the rotation angle α of the pedal crank, which characterizes the current angular position of the pedal crank. The correction curve 50 shown here is standardized, with its integral divided by 360° preferably equal to 1. Therefore, the effective average pedal torque after correction is equal to the value without correction.

[0043] To determine or calculate the motor torque for the drive motor 40, the pedal torque generated by the rider for the respective angular position is divided by the corresponding angle value of the correction curve 50. This "corrected" value corresponds to the motor torque or is preferably proportional to it. The mean value 52 of the correction curve 50 shown here is equal to 1 due to the standardization performed.

[0044] Such a correction curve 50 can also be described by a correction function. This essentially only needs to be periodic over 360°, i.e., over one complete crank revolution. It should describe the typical force curve or the induced pedal torque over the pedaling movement, i.e., one complete crank revolution. One possible function is: KF(α)=S∗sin((α−A)π180)2+W with S = scaling factor; A = adjustment value and W = offset value

[0045] In practice, a scaling factor value of approximately 1.176, or 20 / 17, has proven to be practical. The adjustment value is often specified as 5°, since the maximum pedaling torque according to the correction curve 50 only occurs at a pedaling angle delayed by 5°. In practice, a value of approximately 0.411, or 7 / 17, has been found for the offset value.

[0046] Fig. Figure 3 shows the correction curve 50 and its mean value in polar coordinate representation. Here, it can also be seen that the maximum pedaling torque according to the correction curve occurs at approximately 95° and approximately 275°, respectively.

[0047] Fig. 4 shows a schematic representation of the method according to the invention. In a first step S10, a torque signal containing information about a pedal torque generated by the rider of the pedelec is received to generate a pedal crank-dependent motor torque for a drive motor 40 of a pedelec. In a step S12, an angle signal containing information about a rotation angle of a pedal crank of the pedelec, i.e., information about an angular position, is received.

[0048] In a subsequent step S14, a corrected pedaling torque is determined. The corrected pedaling torque is based on the torque signal, the angle signal, and a predefined correction curve 50. For example, for each rotation angle, the measured pedaling torque can be divided by the corresponding value of the correction curve. The resulting value (corrected pedaling torque value) is a characteristic value that, especially if the correction curve accurately reflects the rider's pedaling behavior, pedaling rhythm, or power distribution, fluctuates little across all rotation angles, i.e., is essentially constant for all rotation angles.

[0049] In a step S16, a motor torque for the drive motor 40 is determined such that it is proportional to the characteristic value of the corrected pedaling torque.

[0050] In step S18, a control signal for the drive motor 40 is output, which is based on the determined motor torque, for example, is proportional. The control signal is designed such that, when the drive motor is controlled with the control signal, it causes and generates the determined motor torque at the drive motor.

[0051] Fig. Figure 4 shows further optional method steps (shown in dashed lines) that include measuring and providing the necessary signals. In an optional step S20, the pedaling torque generated by the rider of the pedelec is measured, preferably using a torque sensor 30. An optional step S22 concerns the generation of the torque signal based on the measurement, which is sent to a torque interface 22 of the device 20 according to the invention in a step S24.

[0052] Further optional method steps relate to measuring the angle of rotation. In step S30, the angle of rotation is measured on a pedal crank of the pedelec. An optional step S32 follows, which involves generating an angle signal based on the measurement. In a further step S34, the angle signal is sent to an angle interface 24 of the device 20 according to the invention in order to subsequently generate the desired motor torque. Reference symbol 10 systems 20 Device 22 Torque interface 24 angle interface 26 Evaluation unit 28 Output interface 29 Storage unit 30 torque sensor 32 sensors 34 Absolute angle sensor 40 drive motor 50 Correction curve 52 mean

Claims

[1] Device (20) for generating a pedal crank-dependent motor torque for a drive motor (40) of a pedelec, comprising a torque interface (22) for receiving a torque signal with information about a pedaling torque generated by a rider of the pedelec; an angle interface (24) for receiving an angle signal with information on a rotation angle of a pedal crank of the pedelec; an evaluation unit (26) for determining a motor torque for the drive motor (40) based on the torque signal, the angle signal and a predetermined correction curve (50) such that the torque signal is corrected with the correction curve and a characteristic value is formed and the motor torque is substantially proportional to the characteristic value; an output interface (28) for outputting a control signal for the drive motor based on the determined motor torque, characterized bythat the evaluation unit (26) is designed to determine the correction curve (50) from a correction function, wherein the correction function preferably comprises a sine function of the pedal angle, particularly preferably a quadratic sine function of the pedal angle and / or characterized by that the correction function comprises an adjustment value, a scaling factor and / or an offset value, wherein the correction function can preferably be adjusted during operation. [2] Device (20) according to claim 1, wherein the evaluation unit (26) is designed to determine the characteristic value from the mean value of the corrected torque signal. [3] Device (20) according to one of the preceding claims, wherein the evaluation unit (26) is designed to determine the engine torque based on a standardized correction curve (50) and / or to use a correction curve based on empirical data of a generated pedaling torque of a plurality of drivers. [4] Device (20) according to one of the preceding claims, wherein the control signal output by the output interface (28) has an amplitude fluctuation range of at most ± 30%, preferably of at most ± 20%, further preferably of at most ± 10%, very preferably of at most ± 5% of the mean value of the control signal over a 360° rotation of the pedal crank. [5] Device (20) according to one of the preceding claims, wherein the control signal output by the output interface (28) is formed based on the generated engine torque and a selected assistance level. [6] Device (20) according to one of the preceding claims, wherein the device comprises a storage unit (29) for storing the correction curve (50), a normalized correction curve and / or a histogram of measured torque signals. [7] System (10) for generating a pedal crank-dependent motor torque for a drive motor (40) of a pedelec, comprising: a device (20) according to one of the preceding claims; a torque sensor (30) arranged on the pedelec for determining the pedaling torque; a sensor (32) arranged on the Pedelec for determining the angle of rotation of a pedal crank of the Pedelec. [8] System (10) according to the preceding claim, wherein the sensor (32) for determining the angle of rotation of a pedal crank of the pedelec is an absolute angle sensor (34) or a speed sensor. [9] Pedelec with a drive motor (40) comprising a system (10) according to claim 7. [10] Method for generating a pedal crank-dependent motor torque for a drive motor (40) of a pedelec, comprising the steps: Receiving a torque signal containing information about a pedaling torque generated by a rider of the pedelec; Receiving an angle signal with information about a rotation angle of a pedal crank of the pedelec; Determining a corrected pedaling torque based on the torque signal, the angle signal and a predetermined correction curve (50); Determining a motor torque for the drive motor (40) based on the corrected pedaling torque such that the motor torque is substantially proportional to a characteristic value of the corrected pedaling torque; Outputting a control signal for the drive motor (40) based on the determined motor torque. [11] Method according to the preceding claim, comprising the further steps: Measuring the pedaling torque generated by the driver of the pedelec, preferably by means of a torque sensor (30); Generating the torque signal based on the measurement; Sending the torque signal to a torque interface (22) of a device (20) for generating an engine torque; Measuring the angular position of a pedal crank of the Pedelec; Generating the angle signal based on the measurement; Sending the angle signal to an angle interface (24) of the device (20) for generating the engine torque. [12] A computer program product comprising program code for performing the steps of the method according to claim 10 when the program code is executed on a computer.

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