Method for operating a drive unit of an electric bicycle

Abstract

【Solution means】 The present invention relates to a method for operating a drive unit (102) of an electric bicycle (100), including the following steps: A driver torque signal (50) based on a driver torque (55) generated by the muscular strength of the driver of the electric bicycle (100) is determined (1), a first filtering (2) of the driver torque signal (50) is performed by a first low-pass filter, a second filtering (3) of the driver torque signal (50) is performed by a second low-pass filter, and depending on the driver torque signal (53) filtered by the second low-pass filter, motor torque is controllably generated (4) by the drive unit (102).

Description

Technical Field

[0001] The present invention relates to a method for operating a drive unit of an electric bicycle and to an electric bicycle.

Background Art

[0002] There are known electric bicycles having a drive unit for assisting the driver torque generated by the driver with motor power. At this time, the assistance by the motor is usually performed only when the driver applies a certain degree of driver torque by himself, that is, only during the pedal operation by the driver. When the driver stops the pedal operation, it is intended that the generation of the motor torque for assistance also stops, or is defined, for example, by legal regulations. The control of the drive torque of the drive unit generated by the motor often depends on the driver torque detected by the sensor. In this case, since the fluctuations of the driver torque generated while pedaling can be very diverse, the provision of the motor torque may also vary greatly, which can have a negative impact on the riding comfort.

Summary of the Invention

[0003] In contrast, the method of the present invention having the constituent features of claim 1 is characterized in that it can provide a simple and low-cost means for accurately controlling or regulating the drive torque of the drive unit of an electric bicycle, which enables particularly high riding comfort for the driver of the electric bicycle. This is achieved by a method for operating a drive unit of an electric bicycle, which includes the following steps: - A driver torque signal based on the driver torque generated by the muscular strength of the driver of the electric bicycle is determined, - A first filtering of the driver torque signal is performed by a first low-pass filter, - A second filtering of the driver torque signal is performed by a second low-pass filter, - Depending on the driver torque signal filtered by the second low-pass filter, the drive unit generates motor torque in a controlled manner.

[0004] What is regarded as the driver torque signal is, in particular, preferably the value of the driver torque currently generated by the driver, detected by a torque sensor. As an alternative, preferably, the driver torque signal may be any signal or any information that represents the generated driver torque and accordingly reflects the driver's wishes, particularly regarding motor assistance of the drive unit.

[0005] The second filtering of the driver torque signal by the second low-pass filter is preferably performed later in time than the first filtering of the driver torque signal by the first low-pass filter.

[0006] When the motor torque is generated in a controlled manner, it is particularly preferred that the drive unit is controlled such that the generated motor torque is directly proportional to the driver torque signal filtered by the second low-pass filter.

[0007] In other words, in this method, the control of the motor torque generated by the drive unit is based on the driver torque signal filtered by a second separate low-pass filter. Thereby, in order to provide the best possible motor torque for high driving comfort, a particularly flexible control of the drive unit can be carried out. In particular, on the one hand, torque fluctuations of the driver torque can be strongly filtered out as required, thereby enabling a particularly even motor torque progression. For example, it can thereby avoid the "jitter" of motor assistance. On the other hand, in another situation, a high responsiveness of the motor assistance of the drive unit, i.e., a timely and direct implementation of the driver's wishes, can be provided. This is achieved by the fact that both separate low-pass filters provide particularly high flexibility with regard to the filtering of the driver torque signal. At this time, in particular, at least one of the two low-pass filters may be adaptively configured in order to enable the best possible adaptation to the respective driving situation during the driving operation.

[0008] The dependent claims indicate preferred developments of the invention.

[0009] The second low-pass filter preferably has a variable time constant. When the method is implemented, the variable time constant is adapted depending on the driver torque signal. In other words, an active adaptation of the variable time constant of the low-pass filter is carried out in accordance with the current progression of the driver torque signal. In this case, for example, an increase in the variable time constant can be carried out in order to cause a relatively strong smoothing of the driver torque signal. As an alternative, a decrease in the variable time constant can be carried out in order to cause a less strong smoothing of the driver torque signal and thereby provide a higher responsiveness of the drive.

[0010] This method particularly preferably further includes the following steps: The difference in the driver torque signal between the input part and the output part of the second low-pass filter is determined. At this time, the variable time constant of the second low-pass filter is adapted depending on the determined difference. That is, the values of the driver torque signals generated at the input part and the output part of the second low-pass filter are subtracted from each other to form a difference. At this time, depending on the magnitude of the difference, the variable time constant of the second low-pass filter is adapted. Accordingly, the adaptation of the filtering can be carried out in a particularly simple manner.

[0011] The variable time constant of the second low-pass filter is preferably raised under the determined decreasing difference. For example, the decreasing difference can be determined by detecting the difference over a preset time period. As an alternative, the gradient of the difference can be determined and the decrease of the difference can be confirmed based on this. Based on the determined decreasing difference, or as an alternative, based on the current low difference value, a uniform and constant driving situation can be estimated. In such cases, for example, only a low reactivity of the drive is required. Therefore, strong smoothing of the driver torque signal can be implemented to prevent unwanted fluctuations in the motor torque and accordingly provide particularly high driving comfort.

[0012] The variable time constant of the second low-pass filter is preferably reduced under the determined increasing difference. For example, the increasing difference can be determined by detecting the difference through a preset time period. As an alternative, the gradient of the difference can be determined and the increase of the difference can be confirmed based on this. Based on the determined increasing difference or alternatively based on the current high difference value, a dynamic driving situation, for example a technically difficult driving situation, can be estimated. In such a case, for example, a high reactivity of the drive is desirable. By reducing the variable time constant of the second low-pass filter, the filtering by the second low-pass filter is reduced or completely deactivated. For example, the variable time constant can be set equal to zero. Thereby, it is possible to specifically and directly implement the driver's wish to the motor torque quickly.

[0013] When the determined difference is greater than or equal to a preset threshold difference, it is even more preferable that the variable time constant of the second low-pass filter is reduced to a value equal to or lower than the preset threshold time constant. Thereby, a high reactivity of the drive can be provided in the same manner as described above. Preferably, as an alternative or in addition, when the determined difference is smaller than the preset threshold difference, the variable time constant of the second low-pass filter is increased to a value greater than the preset threshold time constant. Thereby, in the same way as also described above, an operating mode of the drive unit can be provided in which strong filtering is implemented to prevent unwanted torque fluctuations of the motor torque. Furthermore, the method can be reliably and accurately implemented in a particularly simple manner.

[0014] The determination of the driver torque signal preferably further includes the following steps: The driver torque signal is recorded over a preset time span. At this time, the adaptation of the variable time constant of the second low-pass filter is performed depending on the recorded driver torque signal. For example, the driver torque signal can be recorded over a time span of 5 seconds. Thereby, further simplification of the method and more accurate adjustment of the driving comfort can be achieved.

[0015] The method preferably further includes the following step: The maximum value of the recorded driver torque signal is determined, especially within a preset time span. At this time, the adaptation of the variable time constant of the second low-pass filter is performed depending on the determined maximum value. Along with this, the method can be implemented in a particularly simple and low-cost manner.

[0016] The method particularly preferably further includes the following step: The driver torque signal is multiplied by an auxiliary coefficient. At this time, the generation of the control formula for the motor torque is performed by the driver torque signal multiplied by the auxiliary coefficient. The auxiliary coefficient can be, for example, a preset constant value. As an alternative, the auxiliary coefficient can be configured variably, that is, adaptively. For example, it can be adapted depending on the magnitude of the driver torque signal. Along with this, the control of the drive unit can be performed in a particularly simple manner.

[0017] The multiplication of the driver torque signal is preferably performed before the second filtering, especially between the first filtering by the first low-pass filter and the second filtering by the second low-pass filter. That is, the driver torque signal already multiplied by the auxiliary coefficient is filtered by the second filter.

[0018] As an alternative, the multiplication of the driver torque signal is preferably performed after the second filtering. In this case, the first filtering and the second filtering are performed directly one after the other.

[0019] The first low-pass filter preferably further has a preset first time constant having a constant value. Along with this, the method can be implemented particularly simply and at low cost, and in order to enable the highest possible riding comfort, it is possible to provide optimal preprocessing of the driver torque signal.

[0020] Furthermore, the present invention provides an electric bicycle including a drive unit set up to generate motor torque, in particular for assisting the muscle strength of a driver of the electric bicycle, and a control unit. At this time, the control unit is set up to operatively control the drive unit. Furthermore, the control unit is set up to implement the method described above.

[0021] Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The drawings show the following.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0023] Figure 1 shows a simplified schematic diagram of an electric bicycle 100. The electric bicycle 100 includes a drive unit 102 configured as an electric motor. The drive unit 102 is arranged in the area of the bottom bracket 108 of the electric bicycle 100 and is intended to assist the manual pedaling force of the driver of the electric bicycle 100, applied via the crank mechanism 104, with the torque generated by the electric motor.

[0024] Furthermore, the electric bicycle 100 includes an electrical energy accumulator 109, by which electrical energy can be supplied to the drive unit 102. The drive unit 102 further incorporates a control unit 103.

[0025] Here, the control unit 103 is set up to operate the drive unit 102 depending on the pedal operation of the driver of the electric bicycle 100. Specifically, the drive unit 102 is controlled in such a way that motor torque is generated depending on the driver torque generated by the driver's muscle strength in order to assist with the motor when the driver pedals. Here, it is intended that the generation of motor torque is controlled depending on the magnitude of the driver torque.

[0026] Here, the control unit 103 is set up to implement a method of operating the drive unit 102. By this method, during the running operation of the electric bicycle 100, i.e., especially during forward movement, an optimized operation of the drive unit 102 can be performed depending on the driver torque.

[0027] Next, the procedure of this method will be described in detail with reference to Figures 2 to 4.

[0028] Figure 2 shows, by way of example, a torque record 60 that can be detected during the running of the electric bicycle 100. Here, the driver torque 62 is shown depending on time 61. The driver torque 62 can be detected by a torque sensor 107 (see FIG. 1). That is, in the torque record 60 of FIG. 2, a temporal torque transition 55 as an example of the driver torque 62 is shown.

[0029] As can be seen in FIG. 2, the latest value of the driver torque 62 may change periodically with respect to time 61, for example, similar to a sine wave oscillation.

[0030] The procedure of the method 10 according to the first embodiment of the present invention is shown schematically and significantly simplified in FIG. 3.

[0031] In this method, the determined driver torque 62, particularly its current value determined by the torque sensor 107, is provided as the driver torque signal 50. That is, in particular, the driver torque signal 50 has the same fluctuating transition as the temporal torque transition 55 shown in FIG. 2. Such determination 1 of the driver torque signal 50 is performed in the first method step.

[0032] Next, a first filtering 2 of the driver torque signal 50 is performed by a first low-pass filter. Here, the first low-pass filter has a fixed, preset first time constant. Accordingly, a first smoothing of the driver torque signal 50 is performed.

[0033] After the first filtering 2, preferably immediately thereafter, a second filtering 3 is performed by a second low-pass filter. Here, the second low-pass filter is configured as a filter separate from the first low-pass filter and has a variable time constant unlike the first low-pass filter.

[0034] Subsequent to the second filtering 3 by the second low-pass filter, a multiplication 5 of the filtered driver torque signal 50 and an auxiliary coefficient is performed.

[0035] The auxiliary coefficient may be, for example, a preset constant value. As an alternative, preferably, the auxiliary coefficient may be configured to be variable and can be adapted, for example, depending on the magnitude of the determined driver torque 62. As an alternative or in addition, preferably, the auxiliary coefficient may be configured to be adaptable by a manual driver input by the driver.

[0036] Subsequently, depending on the driver torque signal 53 multiplied by the auxiliary coefficient, the drive unit 102 is operatively controlled by the control unit 103. This is done in the step of generating the control formula 4 of the motor torque.

[0037] The variable time constant of the second low-pass filter is adapted depending on the difference in the driver torque signal 50 between the input and output of the second low-pass filter. For this purpose, in an additional step, a determination 3a of the difference between the driver torque signal 50 at the input of the second low-pass filter and the driver torque signal 50 at the output of the second low-pass filter is made.

[0038] At this time, the adaptation of the second time constant can be done, in one simple embodiment, such that when the difference decreases, the second time constant is increased during the implementation of the method 10. For example, this may be the case when the transition of the driver torque 55 has relatively low temporal variations, as shown in region B of FIG. 2 for example.

[0039] Due to the increased second time constant, relatively strong filtering or smoothing of the driver torque signal is induced under such determined low differences. Thereby, for example, instead of a temporary change in driver torque being immediately embodied as a strong change in motor torque, a particularly uniform operation of the drive unit 102 is induced. This is particularly preferable under driving conditions where a uniform forward movement of the electric bicycle 100, which does not require a strong change in motor torque demand, is desired. In such cases, particularly effective filtering can be performed by a second low-pass filter with a high time constant, thereby providing particularly high riding comfort. For example, undesirable motor torque fluctuations can be avoided.

[0040] Accordingly, when the difference increases, the second time constant can be decreased. This may be the case, for example, when the transition of the driver torque 55 has large temporal variations, as shown in region A of FIG. 2, for example.

[0041] Due to the second time constant decreased in such cases, under such large differences, it is realized that less strong filtering or smoothing of the driver torque signal 50 is performed. Thereby, the drive unit 102 reacts more quickly and directly to changes in the driver torque signal 50, thereby giving the driver a feeling that the driving response is good. This is particularly desirable at times of dynamically difficult driving conditions in order to provide high riding comfort in such driving conditions.

[0042] In an alternative or additional embodiment of the method 10, the current value of the difference determined in step 3a is monitored each time. When the determined difference is greater than or equal to a preset threshold difference, the variable second time constant of the second low-pass filter is reduced to a value equal to or lower than the preset threshold time constant. Accordingly, when the determined difference is smaller than the preset threshold difference, it is preferable to increase the variable second time constant of the second low-pass filter to a value higher than the preset threshold time constant. Thereby, the method 10 can be implemented particularly simply and at low cost.

[0043] FIG. 4 shows a highly simplified schematic view of a method 10 for operating a drive unit 102 of an electric bicycle 100 according to a second embodiment of the invention. The second embodiment basically corresponds to the first embodiment of FIG. 3, but there is a difference in the alternative temporal procedure of the method steps. Specifically, in the second embodiment, the multiplication 5 of the auxiliary coefficient and the driver torque signal 50 is performed temporally between the first filtering 2 and the second filtering 3. That is, the driver torque signal 50 already multiplied by the auxiliary coefficient is filtered by the second low-pass filter at the time of the second filtering 3. The thus filtered and multiplied driver torque signal 53' is then provided directly to the step of generating the control formula of the motor torque 4.

[0044] The driver torque signal 50 and / or the difference are continuously monitored in each of the above-described embodiments, and it is preferable that the instantaneous value at each time can be used for the implementation of the method 10.

[0045] As an alternative, it is particularly preferred to record the driver torque signal 50 and / or the difference over a preset time span, and at this time the adaptation of the variable second time constant of the second low-pass filter is carried out depending on such a record. At this time, if the adaptation of the variable second time constant of the second low-pass filter is carried out depending on the determined maximum value of the driver torque signal 50 and / or the difference recorded within the preset time span, a particularly simple embodiment of the method 10 can be provided.

Explanation of Signs

[0046] 1 Judgment 2 First Filtering 3 Second Filtering 3a Judgment 4 Generation of Control Formula 5 Multiplication 50 Driver Torque Signal 53 Driver Torque Signal 55 Driver Torque 100 Electric Bicycle 102 Drive Unit 103 Control Unit

Claims

1. A method for operating a drive unit (102) of an electric bicycle (100), comprising the following steps: A driver torque signal (50) based on a driver torque (55) generated by the muscle strength of a driver of the electric bicycle (100) is determined (1). First filtering (2) of the driver torque signal (50) is performed by a first low-pass filter. Second filtering (3) of the driver torque signal (50) is performed by a second low-pass filter. A method in which motor torque is controllably generated (4) by the drive unit (102) depending on the driver torque signal (53) filtered by the second low-pass filter.

2. The method according to claim 1, wherein the second low-pass filter has a variable time constant adapted depending on the driver torque signal (50).

3. Further comprising the following step: A difference of the driver torque signal (50) between an input part and an output part of the second low-pass filter is determined (3a), and the variable time constant of the second low-pass filter is adapted depending on the difference. The method according to claim 2.

4. The method according to claim 3, wherein the variable time constant of the second low-pass filter is increased under the determined decreasing difference.

5. The method according to claim 3 or 4, wherein the variable time constant of the second low-pass filter is decreased under the determined increasing difference.

6. When the determined difference is greater than or equal to a preset threshold difference, the variable time constant of the second low-pass filter is decreased to a value equal to or lower than a preset threshold time constant, and / or When the determined difference is smaller than the preset threshold difference, the variable time constant of the second low-pass filter is increased to a value greater than the preset threshold time constant. The method according to any one of claims 3 to 5.

7. The determination (1) of the driver torque signal (50) includes a step of recording the driver torque signal (50) over a preset time width, The adaptation of the variable time constant is performed depending on the recorded driver torque signal (50). The method according to any one of claims 1 to 6.

8. The method according to claim 7, further comprising a step of determining a maximum value of the recorded driver torque signal (50), wherein the adaptation of the variable time constant is performed depending on the maximum value.

9. The method according to any one of claims 1 to 8, further comprising a step of multiplying the driver torque signal (50) by an auxiliary coefficient (5), wherein the generation of the control formula for the motor torque is performed by the driver torque signal (53, 53') multiplied by the auxiliary coefficient.

10. The method according to claim 9, wherein the multiplication (5) of the driver torque signal (50) is performed before or after the second filtering (2).

11. The method according to any one of claims 1 to 10, wherein the first low-pass filter has a preset constant time constant.

12. An electric bicycle comprising a drive unit (102) and a control unit (103) set up to operate the drive unit (102) according to a control formula, wherein the control unit (103) is further set up to implement the method according to any one of claims 1 to 11.

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