Method for adjusting motor torque of motor of electric bicycle and associated device for adjusting motor torque

Abstract

To provide a method and a device of adjusting the motor torque of a motor of an electric bicycle.SOLUTION: The present invention relates to a method (100) for adjusting a motor torque of a motor of an electric bicycle. The method includes: a step (101) for detecting a speed signal which represents the speed of the bicycle; a step (102) for selecting a filter parameter for a filter unit on the basis of the dynamics of the speed signal; a step (103) for filtering the speed signal by the filter unit by applying the selected filter parameter; and a step (104) for ascertaining motor torque on the basis of the filtered speed signal. The present invention also relates to an associated device.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for adjusting the motor torque of an electric bicycle motor. [Background technology]

[0002] Due to legal requirements, motor assistance is only permitted up to a certain speed for pedelecs. This is observed by linearly reducing the motor assistance after a certain speed. The limit speed at which the motor assistance starts to decrease is usually the legal value plus a tolerance. The motor torque is simply calculated from the driver torque, the assistance coefficient, and the speed limit coefficient.

[0003] In this regard, the assistance coefficient is typically specified by an assistance characteristic curve, which shows the assistance coefficient for each possible speed. This assistance characteristic curve typically has a slope where the assistance coefficient is adjusted downward near the limit speed. This slope must be a compromise between two requirements: on the one hand, maximum assistance should be achieved as far as possible up to the limit, which means a steep slope is desirable. On the other hand, an abrupt stop of assistance should not be felt, which means a slope that is as gentle as possible is also desirable.

[0004] The steeper the gradient, the more noticeable small fluctuations in the speed signal become, since they directly affect the motor assist. Fluctuations in the speed signal can occur at any time. First, in the case of pedelecs, speed measurement is not very accurate. This is due, for example, to the sensor equipment used, such as reed sensors, which calculate the speed signal from pulses. However, due to the type of construction, such pulses are usually only provided once per wheel revolution. Second, the actual speed always fluctuates within a certain range, even under constant ambient conditions and with uniform pedaling by the driver.

[0005] Motor assist that varies based on an unstable measured speed is generally perceived as unpleasant by bicyclists. Summary of the Invention

[0006] A method according to the present invention for adjusting the motor torque of an electric bicycle motor includes the steps of capturing a speed signal representative of the bicycle's speed, selecting filter parameters for a filter unit based on the dynamics of the speed signal, filtering the speed signal with the filter unit applying the selected filter parameters, and determining the motor torque based on the filtered speed signal.

[0007] The inventive device for adjusting the motor torque of an electric bicycle motor is adapted to perform the following steps: capturing a speed signal representative of the speed of the bicycle, selecting filter parameters for a filter unit based on the dynamics of the speed signal, filtering the speed signal by the filter unit applying the selected filter parameters, and determining the motor torque based on the filtered speed signal.

[0008] In this regard, the determined motor torque is, among other things, the maximum motor torque provided to assist the bicycle rider. Thus, the determined motor torque is not necessarily actually provided by the motor, but can be provided when needed to assist the rider and the bicycle, for example, when indicated by the rider torque. The rider torque is the torque applied to the bicycle pedals by the bicycle rider. Alternatively, the determined motor torque is the motor torque provided by the motor in response to the determination of the motor torque.

[0009] A speed signal representing the speed of the bicycle is acquired. The speed signal is preferably acquired by a sensor disposed on the bicycle, for example, by a reed sensor. The speed signal is preferably a signal whose signal value increases as the bicycle speed increases and whose signal value decreases as the bicycle speed decreases.

[0010] The filter parameters for the filter unit are selected based on the dynamics of the speed signal. Typically, a single value for a specific filter parameter is selected. The dynamics of the speed signal is a parameter that indicates the rate of change of the speed signal. That is, the dynamics of the speed signal is, among other things, zero when the speed signal is constant. The dynamics of the speed signal is, among other things, represented by the slope of the speed signal over its time course. The filter parameters for the filter unit are selected based on this dynamics. That is, the filter parameters are adapted, among other things, in response to changes in the dynamics of the speed signal. Different dynamics of the speed signal result in different values ​​for the filter parameters. That is, in selecting the filter parameters, a single value for the parameter supplied to the filter unit is selected. The filter characteristic of the filter unit is adapted accordingly to the filter parameters.

[0011] The velocity signal is filtered by the filter unit using selected filter parameters, and is therefore filtered depending on the dynamics of the velocity signal. The filtering of the velocity signal generates a filtered velocity signal.

[0012] The motor torque is determined based on the filtered speed signal. This motor torque is, in particular, the maximally supplied motor torque. Therefore, the motor torque is generated based on the filtered speed signal, not directly from the speed signal. For example, a number of possible values ​​of the speed signal are each assigned an associated motor torque. Corresponding to this assignment, the motor torque is determined from the filtered speed signal. The motor torque is therefore determined indirectly based on the actual speed of the electric bicycle, although the speed signal is filtered in advance. Therefore, depending on the selection of the filter parameters, some fluctuations in the actual speed of the electric bicycle may not affect the determination of the motor torque.

[0013] This allows for uniform driver assistance at the limit, even when small fluctuations in the speed signal are present, thereby improving driving comfort, especially when driving uniformly at the limit, while ensuring compliance with the legal basic requirements for motor driver assistance.

[0014] The dependent claims indicate preferred variants of the invention. The dynamics of the speed signal are preferably represented by the acceleration of the bicycle. This also means that the acceleration of the bicycle can be considered as the dynamics of the speed signal. In this regard, the acceleration of the bicycle is determined, among other things, by the derivative of the speed signal over time. That is, the acceleration of the bicycle can be read from the speed signal, and this acceleration represents, among other things, the gradient of the speed signal over time. Therefore, the dynamics of the speed signal are preferably determined by calculation from the speed signal. Alternatively, the dynamics of the speed signal can be determined independently of the speed signal. That is, for example, if a sensor represents the acceleration of the bicycle, the dynamics of the speed signal can be determined based on the sensor. In this case, the dynamics of the speed signal can be captured using an acceleration sensor.

[0015] It is also advantageous if the filter unit includes a low-pass filter. In particular, the filter unit is a low-pass filter with adjustable filter parameters. By low-pass filtering of the speed signal, relatively small fluctuations in the speed signal that directly affect the motor assist can be filtered out. In other words, fluctuations caused by the driver's pedaling movements can also be filtered out of the speed signal.

[0016] It is also advantageous to select filter parameters such that the speed signal is filtered less strongly in the case of a first dynamic than in the case of a second dynamic, which is greater than the second dynamic. In other words, this means that the speed signal is filtered less strongly in the case of a strong dynamic of the speed signal than in the case of a weaker dynamic. In this regard, stronger filtering means that unintended signal components are attenuated more strongly. This, among other things, can prevent the bicycle motor from providing a torque greater than permitted for a certain speed. In particular, it can prevent the motor from exceeding the permitted assistance above a limit speed, which could occur, for example, if a strong acceleration occurs in a highly dynamic speed signal, but this strong acceleration is filtered, causing the system to erroneously infer a lower bicycle speed. This can be avoided by filtering more weakly in the case of high dynamics, which allows the speed signal to be provided almost unfiltered and taken into account for determining the motor torque.

[0017] Above a predetermined first dynamics limit, the filter parameters are preferably set to a minimum value, at which the filter unit performs minimal or no filtering of the speed signal. This means that when the dynamics of the speed signal, particularly the bicycle's acceleration, are above the first dynamics limit, the filter unit performs minimal or no filtering. Setting such a first dynamics limit can ensure that a filtered speed signal indicating a bicycle speed that differs from the bicycle's true speed is not output for high dynamics of the speed signal. This can ensure that no motor torque is supplied when the bicycle's actual speed is above the maximum value for which motor assistance is permitted.

[0018] It is also advantageous if the filter parameters are selected depending on the bicycle's acceleration, such that the degree of filtering of the speed signal increases over time when the acceleration is below a second dynamics limit and decreases over time when the acceleration is above the second dynamics limit. This results in a smoother speed signal, particularly when the bicycle is moving steadily, and thus more uniform assistance to the rider at a limiting speed beyond which the bicycle should not be assisted by the motor.

[0019] Furthermore, it is advantageous if the first dynamics limit corresponds to a higher acceleration than the second dynamics limit, which can ensure that a range above the first dynamics limit is provided in which distortion of the velocity signal due to filtering is eliminated, while a range below the first dynamics limit is provided in which the filter constants can be dynamically changed depending on whether the dynamics are above or below the second dynamics limit.

[0020] It is also advantageous if, in the step of determining the motor torque based on the filtered speed signal, the motor torque is determined based on an assistance characteristic curve. This assistance characteristic curve defines the degree of motor torque that can be provided for various speeds and, in particular, defines at what speed value the motor assistance of the rider should be reduced. Such assistance characteristic curves are commonly used in controlling electric bicycles. Therefore, the method according to the present invention can also be applied to assistance characteristic curves that are already used in the prior art. In this case, the assistance characteristic curve can be used as is, although this does not exclude that the assistance characteristic curve can be modified based on further methods.

[0021] Preferably, the assist characteristic curve defines an assist coefficient versus speed. Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. [Brief explanation of the drawings]

[0022] [Figure 1] 1 shows an electric bicycle equipped with a device for adjusting the motor torque of a motor of the electric bicycle; [Figure 2] 1 is a flow diagram of a method according to the invention for adjusting the motor torque of a motor of an electric bicycle; [Figure 3] 4 is a graph showing an exemplary assist characteristic curve. [Figure 4] 1 is a signal flow diagram enabling the implementation of a method for regulating the motor torque of a bicycle motor; DETAILED DESCRIPTION OF THE INVENTION

[0023] 1 shows a bicycle 1 including a device 2 for adjusting the motor torque of a motor of the electric bicycle 1. This device 2 is an electronic control unit of the motor of the electric bicycle 1. The device 2 is adapted to carry out a method 100 according to the invention for adjusting the motor torque of a motor of the electric bicycle 1.

[0024] FIG. 2 shows a flow diagram of a method 100 for adjusting the motor torque of a motor of an electric bicycle 1. The method 100 starts with a first process step 101, which involves capturing a speed signal 10 representative of the speed of the bicycle 1. This speed signal 10 is, among other things, the output signal of a speed sensor, e.g., a reed sensor. That is, the speed signal 10 is, for example, an analog signal having an amplitude representative of the speed of the bicycle 1. That is, for example, there is a linear relationship between the amplitude of the speed signal 10 and the speed of the e-bicycle 1. In an alternative embodiment, the speed signal 10 is a digital signal.

[0025] Following the execution of the first process step 101, a second process step 102 is executed. In the second process step 102, a selection of filter parameters for the filter unit 11 is performed based on the dynamics of the speed signal. Thus, in the second process step 102, at least one filter parameter T is selected and generated, and this filter parameter T is supplied to the filter unit 11. In this embodiment, the filter unit 11 is a low-pass filter that filters the speed signal 10. The filter parameter T adjusts the filter characteristics of the filter unit 11, here the low-pass filter. In this regard, the filter parameter T adjusts, among other things, the damping value of the low-pass filter.

[0026] The dynamics of the speed signal 10 is essentially the rate of change of the speed signal. In the embodiment described here, the dynamics of the speed signal is determined by the acceleration of the electric bicycle 1. That is, the speed signal 10 increases strongly in the case of a strong acceleration, which causes a strong change in the speed signal 10. This results in a high dynamics of the speed signal. However, it should be noted here that, as an alternative, other values ​​representing the dynamics of the speed signal can also be used to select the filter parameters. That is, in the speed signal, frequency components are present that result, for example, from the pedaling frequency of the rider of the bicycle 1. For example, the dynamics can be selected to represent the rate of change of the frequency of the speed signal 10.

[0027] The filter parameter T is selected so that the speed signal 10 is filtered less strongly in the case of a first dynamics than in the case of a second dynamics, which is greater than the second dynamics. This results in less filtering of the speed signal 10 in the case of high dynamics, thereby ensuring accurate compliance with the limit values, for example, during subsequent determination of the motor torque. In the embodiment described here, two dynamics limit values ​​are defined, which divide the range of possible values ​​representing the dynamics of the speed signal into three ranges: a first dynamics limit value and a second dynamics limit value. The first dynamics limit value corresponds to a higher acceleration than the second dynamics limit value.

[0028] Above the first dynamics limit, i.e., when the dynamics of the speed signal are greater than the first dynamics limit, the filter parameter T is set to its minimum value, which results in minimal or no filtering of the speed signal 10 by the filter unit. This means, for example, that the attenuation in the attenuation range of the low-pass filter is set to 0. This corresponds to the low-pass filter being deactivated. In the case of very high dynamics of the speed signal, it is therefore ensured that no changes are made to the speed signal 10 before it is taken into account for determining the motor torque.

[0029] If the dynamics of the speed signal are between the first and second dynamics limit values, the filter parameter T is set to decrease over time, thereby ensuring that the filtering of the speed signal 10 is not terminated abruptly, which could result in an unpleasant driving sensation.

[0030] If the dynamics of the speed signal 10 are below the second dynamics limit, the degree of filtering of the speed signal 10 increases over time. This means that an especially strong filtering of the speed signal 10 by the low-pass filter is achieved over time. This means that even when driving at a continuous speed, an especially strong filtering of the speed signal 10 is achieved, which ensures an especially continuous assistance for the driver and therefore also an especially continuous result when determining the motor torque. This means that an especially comfortable driving sensation is achieved when driving at a continuous speed.

[0031] Following the selection of the filter parameters T for the filter unit 11 in the second process step 102, the speed signal 10 is filtered by the filter unit 11 using the selected filter parameters T in a third process step 103. Thus, the speed signal 10 is first analyzed to determine the filter parameters T for the filter unit 11, and is then filtered accordingly by the filter unit 11. In the process, unintended signal components are filtered out of the speed signal 10. Thus, the speed signal 10 waits at the inlet of the filter unit 11. At the outlet of the filter unit 11, a filtered speed signal 12 is output.

[0032] The third process step 103 is followed by a fourth process step 104. In the fourth process step 104, a motor torque determination is performed based on the filtered speed signal 12. In this regard, the motor torque of the motor of the electric bicycle 1 is determined based on an assist characteristic curve 20. The assist characteristic curve 20 defines an assist coefficient S as a function of the speed of the bicycle 1.

[0033] An exemplary assist characteristic curve 20 is shown in FIG. 3. The assist characteristic curve 20 defines how strongly the motor torque of the motor should assist the bicycle torque. For example, it can be seen that in a relatively low speed range, e.g., below 23 km / h, an assist coefficient S of "1" should be selected. This means that the driver torque applied by the rider is multiplied by the assist coefficient S of "1" to calculate the motor assist, specifically the motor torque, to be provided. After an exemplary limit speed of 23 km / h, the assist coefficient S decreases along a gradient, reaching a value of 0 at a speed of approximately 26 km / h. Within this range, the assist coefficient S decreases from the value "1" to the value "0." This means that above the 26 km / h limit, the motor torque of the motor no longer assists the rider. In the range between 23 and 26 km / h, the motor linearly decreases the rider's assistance. Such an assist characteristic curve 20 is known from the prior art. However, according to the invention, the motor torque, and therefore also the assist factor, is determined on the basis of the filtered speed signal 12, and not on the basis of the speed signal originally captured by the sensor. This removes signal components from the speed signal 10 that would cause the selection of an assist factor S that may be perceived as unpleasant in the case of continuous propulsion of the electric bicycle 1.

[0034] FIG. 4 shows a signal flow diagram for implementing the method 100. From FIG. 4, it can be seen that a speed signal 10 is provided at the input. This speed signal 10 was previously acquired, for example, by a sensor. The speed signal 10 is then directly provided to a filter unit 11, which is a low-pass filter. In parallel with this, a derivative of the speed signal 10 is formed to determine the dynamics of the speed signal 10. In this example, the speed v represented by the speed signal 10 is converted into an acceleration a. A filter parameter T is calculated from the acceleration a in an electronic computer 13 based on the acceleration a. In this regard, a dynamic calculation of the filter parameter T is performed. The filter parameter T may also be referred to as a filter constant. The filter parameter T is provided to the filter unit 11, which adjusts the filter characteristic of the filter unit 11. The speed signal 10 is filtered according to the selected filter characteristic of the filter unit 11 and provided by the filter unit 11 at the output. The filtered speed signal 12 is used to calculate the assistance factor S. That is, for example, the determination unit 14 reads the assist coefficient S from the assist characteristic curve shown in Fig. 3. The motor torque of the motor of the electric bicycle 1 is adjusted in accordance with the read assist coefficient S. In this regard, the motor torque is calculated, for example, from the bicycle torque, the assist coefficient S, and a speed limit coefficient.

[0035] That is, the method 100 achieves uniform driver assistance at the limiting limits even during small fluctuations in the speed signal. Simple non-dynamic low-pass filtering of the speed signal may also result in uniform driver assistance at the limit in some situations. However, the resulting signal phase delay would delay the termination of assistance, making compliance with legal regulations impossible. Therefore, method 100 provides a concept involving dynamic low-pass filtering of the speed signal.

[0036] In this regard, the filter constant T of the low-pass filter varies depending on the dynamics of the speed signal 10. The following behavior should be achieved: a) No or weak filtering of the speed signal 10 in case of high dynamics of the speed signal (strong acceleration or braking phases).

[0037] b) Strong filtering of the speed signal 10 when there is no or low dynamics of the speed signal 10 (constant running). The velocity signal 10 is filtered with a filter constant T, which is bounded by the range Tmax (maximum filtering) and Tmin (no filtering). From the velocity signal, an acceleration level is calculated. For a particular acceleration level a grenz Above this limit, T=Tmin always applies, which ensures compliance with regulations for heavy acceleration at the limit and that assistance is resumed as quickly as possible in the event of heavy braking above the limit.

[0038] a grenz Below this, the filter constant T changes dynamically: at low acceleration levels the filter constant increases over time, and at higher acceleration levels the filter constant decreases over time. This results in a smoother speed signal 10 in the case of constant driving, and therefore a more uniform assistance to the driver at the limit.

[0039] Reference is expressly directed to the disclosure of Figures 1-4, along with the above written disclosure. [Explanation of symbols]

[0040] 1. Electric bicycle 2 equipment 10 speed signal 11 Filter unit 12 Filtered Speed ​​Signal 13 Electronic computer 14 Confirmed Units 20 Assist characteristic curve a acceleration T filter parameter S Assist Coefficient v speed

Claims

1. A method (100) for adjusting the motor torque of a motor of an electric bicycle (1), comprising: - a step (101) of capturing a speed signal (10) representing the speed of the electric bicycle (1); - a step (102) of selecting a filter parameter (T) for a filter unit (11) based on the dynamics of the speed signal (10); - a step (103) of filtering the speed signal (10) by the filter unit (11) with the selected filter parameter (T) applied; - a step (104) of determining the motor torque based on the filtered speed signal (12). The method (100) comprising the above steps.

2. The method (100) according to claim 1, characterized in that the dynamics of the speed signal (10) are represented by the acceleration of the electric bicycle (1).

3. The method (100) according to claim 1, characterized in that the filter unit (11) includes a low-pass filter.

4. The method (100) according to claim 1, characterized in that the filter parameter (T) is selected such that the speed signal (10) is filtered less strongly in the case of a first dynamics than in the case of a second dynamics, and the first dynamics are greater than the second dynamics.

5. The method (100) according to claim 1, characterized in that above a predefined first dynamics limit value, the filter parameter (T) is set to a minimum value, and at the minimum value, the least filtering or no filtering of the speed signal (10) by the filter unit (11) is performed.

6. The filter parameter (T) is selected depending on the acceleration of the electric bicycle (1), - when the acceleration is below a second dynamics limit value, the degree of filtering of the speed signal (10) increases over time, - when the acceleration is above the second dynamics limit value, the degree of filtering of the speed signal (10) decreases over time. The method (100) according to claim 5, characterized in that it is selected as such.

7. The method (100) according to claim 6, characterized in that the first dynamics limit value corresponds to an acceleration higher than the second dynamics limit value.

8. The method (100) according to claim 1, characterized in that, in the step of determining the motor torque based on the filtered speed signal (12), the motor torque is determined based on an assist characteristic curve.

9. The method according to claim 8, characterized in that the assist characteristic curve (20) defines an assist coefficient (S) with respect to speed.

10. An apparatus (2) for adjusting the motor torque of a motor of an electric bicycle (1), comprising the following steps: - capturing a speed signal (10) representing the speed of the electric bicycle; - selecting a filter parameter (T) for a filter unit (11) based on the dynamics of the speed signal (10); - filtering the speed signal (10) by a filter unit (11) to which the selected filter parameter (T) is applied; - determining a motor torque based on the filtered speed signal (12) An apparatus (2) adapted to perform the steps.

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