Method for operating a brake assist system for an electric motorcycle

Description

Field of the invention

[0001] The invention relates to a method for operating a brake assist system for an electric motorcycle. Furthermore, the invention relates to a control unit, a computer program, and a computer-readable medium for executing such a method, as well as to a brake assist system equipped with such a control unit. State of the art

[0002] An ABS system typically comprises various hydraulic and electrical components for brake pressure control. For example, a very simple ABS system can be implemented using an inlet valve, an outlet valve, an accumulator chamber, and a check valve.

[0003] For electric motorcycles powered by an electric motor, it is generally possible to use the electric motor for torque modulation. However, in practice, depending on the vehicle type or the size of the electric motor, the problem may arise that the maximum torque generated by the electric motor alone is insufficient to meet the requirements of an ABS system.

[0004] The state of the art is WO 2020 / 118233 A1, which describes an ABS system in conjunction with an electric motor. Disclosure of the invention

[0005] Against this background, the approach presented here provides a method according to claim 1 for operating a brake assist system for an electric motorcycle, a corresponding control unit, a corresponding brake assist system, a corresponding computer program, and a corresponding computer-readable medium according to the independent claims. Advantageous further developments and improvements of the approach presented here emerge from the description and are described in the dependent claims. Advantages of the invention

[0006] Embodiments of the present invention make it possible to brake an electric motorcycle by combining an electromotive braking function with a non-electromotive braking function, for example, a hydraulic braking function. In this way, a corresponding brake assist system for the electric motorcycle can be provided very cost-effectively, for example, by reducing the number of hydraulic components of the brake assist system. Furthermore, the braking performance of the electric motorcycle can be improved.

[0007] A first aspect of the invention relates to a computer-implemented method for operating a brake assistance system for an electric motorcycle. The method comprises at least the following steps: determining a total braking torque required to brake the electric motorcycle; determining an engine torque to be generated by an electric motor of the electric motorcycle as a function of the total braking torque and a maximum braking torque that can be generated by a braking system of the electric motorcycle; and, when the maximum braking torque is generated, generating a control command for controlling the electric motor so that the engine torque is generated together with the maximum braking torque.

[0008] An "electric motorcycle" can generally be understood as a single-track vehicle or two-wheeler with a drive in the form of an electric motor or a combination of an electric motor and an internal combustion engine. An electric motorcycle can also be an electric scooter, an electric bicycle, or a motorcycle-like two-track vehicle with more than two wheels, such as a quad bike.

[0009] The engine torque can be a drive torque or a braking or recuperation torque.

[0010] "Total braking torque" can, for example, be understood as a braking torque estimated based on the current wheel speed of one or more wheels of the electric motorcycle and / or the current engine speed of the electric motor. The current wheel speed can, for example, be measured using a separate wheel speed sensor. However, it is also possible to determine the current wheel speed from the current engine speed. In this case, a separate wheel speed sensor is not necessary.

[0011] The total braking torque can be determined to prevent locking of the wheel that is subjected to both the maximum braking torque of the braking system and the torque of the electric motor, for example, during emergency or full braking. The total braking torque can therefore be understood as the braking torque needed to brake and / or bring the electric motorcycle to a stop as quickly and safely as possible.

[0012] The maximum total braking torque can, for example, be equal to the sum of the maximum braking torque of the braking system and a maximum negative engine torque, i.e., the maximum braking or recuperation torque of the electric motor. The maximum total braking torque should be selected so that the electric motorcycle can be brought to a stop quickly and safely in any driving situation.

[0013] It is possible for the electric motor and the braking system to act on the same wheel or wheels of the electric motorcycle, for example, the rear wheel. However, it is also possible for the electric motor to drive the rear wheel, while the braking system brakes the front wheel or, in addition, the rear wheel. For example, in this case, the braking system can be configured as a single-channel ABS system for the front wheel. The rear wheel can be braked exclusively by the electric motor in recuperation mode.

[0014] The method described here and below enables the electric motor to be used for targeted modulation of the braking torque, whereby an average value of this braking torque is provided by the braking system, independent of the electric motor. The average value can be reduced or increased in magnitude by generating a drive torque, braking torque, or recuperation torque using the electric motor, either simultaneously or slightly offset in time.

[0015] To achieve this, it is advisable to shift the operating point of the braking system accordingly, i.e., to appropriately adapt the maximum braking torque that can be generated by the braking system, for example, its maximum braking pressure, to the maximum motor torque of the electric motor. For example, in the simplest case, the braking system can be equipped with a corresponding isolating or pressure-limiting valve. Such a valve can be retrofitted very easily.

[0016] Especially with electric scooters, the braking or recuperation torque of the electric motor alone may not be sufficient to decelerate the electric motorcycle quickly or forcefully enough. However, the advantage is that the electric motor can modulate the engine torque with very high dynamics, which would be perfectly sufficient for ABS control.

[0017] By combining the braking effect achieved by the electric motor with the braking effect of an additional braking system, for example a hydraulic one, which is capable of providing the required high braking torque, an ABS functionality that meets both requirements can be realized at relatively low cost.

[0018] If the braking system and the electric motor are activated simultaneously, the total braking torque exerted on the wheel in question in the event of braking is the sum of the motor torque of the electric motor and the braking torque of the braking system.

[0019] If the electric motor generates a positive motor torque during braking, it counteracts the braking system and reduces the total braking torque acting on the wheel accordingly. The braking system defines the average braking torque, so to speak, and the electric motor then modulates the total torque acting on the wheel around this average value, i.e., increases or decreases it based on this average value.

[0020] Since a typical (hydraulic) braking system generates a maximum braking torque that is generally significantly greater than the maximum drive torque of a typical electric motor, the electric motor would normally not be able to completely cancel out the braking torque generated by the braking system during an emergency stop. However, by installing a suitable valve in the braking system, it can be ensured that, on the one hand, the sum of the limited maximum braking torque of the braking system and the maximum braking torque of the electric motor corresponds to the maximum total braking torque required for emergency braking, and, on the other hand, the limited maximum braking torque of the braking system can be fully compensated by the maximum drive torque of the electric motor, so that in this case, the total torque acting on the wheel in question is zero.

[0021] Such a limitation makes it possible to use the electric motor to modulate the total braking torque between zero and the maximum braking torque required for emergency braking with sufficient dynamics for ABS functionality. The advantage is that such ABS functionality can be implemented by simply combining an existing electric drive motor and an existing (hydraulic) braking system with only a single additional component in the form of a valve.

[0022] The corresponding control logic can be implemented, for example, in a control unit of the electric motorcycle. A wheel speed sensor is not absolutely necessary, as the wheel speed can also be determined from the motor speed using any internal Hall sensors of the electric motor.

[0023] A second aspect of the invention relates to a control unit. The control unit comprises a processor configured to execute the method according to an embodiment within the meaning of the first aspect of the invention. Features of the method according to an embodiment within the meaning of the first aspect of the invention can also be features of the control unit, and vice versa.

[0024] The control unit may include hardware and / or software modules. In addition to the processor, the control unit may include a memory and data communication interfaces for data communication with peripheral devices.

[0025] A third aspect of the invention relates to a brake assist system for an electric motorcycle. The brake assist system comprises at least one electric motor for accelerating and / or decelerating the electric motorcycle and a control unit according to an embodiment within the meaning of the second aspect of the invention. Such a brake assist system can be manufactured particularly inexpensively. Furthermore, such a brake assist system can contribute to a significant improvement in the braking performance of an electric motorcycle. Accidents can thus be avoided.

[0026] A fourth aspect of the invention relates to a computer program. The computer program comprises instructions that, when executed by the processor, cause the method according to an embodiment within the meaning of the first aspect of the invention.

[0027] A fifth aspect of the invention relates to a computer-readable medium on which the computer program according to an embodiment within the meaning of the third aspect of the invention is stored. The computer-readable medium can be a volatile or non-volatile data storage device. For example, the computer-readable medium can be a hard disk, a USB storage device, a RAM, ROM, EPROM, or flash memory. The computer-readable medium can also be a data communications network enabling a download of program code, such as the Internet or a data cloud.

[0028] Features of the method according to an embodiment within the meaning of the first aspect of the invention may also be features of the computer program and / or the computer-readable medium and vice versa.

[0029] Ideas for embodiments of the present invention can be considered, among other things, to be based on the thoughts and findings described below.

[0030] According to one embodiment, the engine torque can be determined by calculating the difference between the total braking torque and the maximum braking torque. In this way, the total braking torque can be determined particularly efficiently.

[0031] According to one embodiment, the maximum drive torque that can be generated by the electric motor is not less than the maximum braking torque. This has the effect that the braking effect of the braking system can be compensated for by the braking effect of the electric motor, if necessary, particularly in the case of full or emergency braking, when the braking system generates the maximum braking torque and the objective is to prevent the wheel being braked from locking.

[0032] According to one embodiment, the method may further comprise the following step: receiving measurement data indicating a current speed of the electric motor. The total braking torque can be determined by evaluating the measurement data. The measurement data can be provided, for example, by means of a corresponding speed sensor, such as a Hall sensor. It is also possible to estimate the speed based on measured phase voltages and / or currents of the electric motor. In this way, the use of a separate wheel speed sensor can be dispensed with. This further reduces the cost of manufacturing the brake assist system.

[0033] According to one embodiment, the brake assistance system can further comprise a brake system for braking the electric motorcycle. The brake system can be adapted such that the maximum braking torque that can be generated by the brake system is not greater in magnitude than the maximum drive torque that can be generated by the electric motor. The brake system can, for example, be a hydraulic front and / or rear wheel brake. As mentioned above, the brake system can, for example, comprise an inlet valve, an outlet valve, a storage chamber, and a check valve. Thus, the brake pressure that can be generated by a rider by actuating a brake lever or pedal can be limited in a technically efficient manner such that the maximum braking torque of the brake system can be compensated by the maximum drive torque of the electric motor.

[0034] According to one embodiment, the braking system can comprise a hydraulic brake circuit and at least one brake pressure valve for limiting a brake pressure in the hydraulic brake circuit to a value corresponding to the maximum drive torque. In other words, the maximum brake pressure in the hydraulic brake circuit can be limited such that the maximum braking torque of the braking system is at most as large as the maximum drive torque. The brake pressure valve can, for example, be an isolating valve that decouples the master cylinder from the slave cylinder when a certain brake pressure is reached. The isolating valve can, for example, be controlled by the control unit of the electric motorcycle depending on a measured current brake pressure in the hydraulic brake circuit. This has the advantage that the maximum braking torque can be varied depending on the driving situation, for example, depending on the road surface.Alternatively, the brake pressure valve can be designed as a simple pressure relief valve, for example as a check valve, i.e. as a passive component that limits the brake pressure to a fixed value corresponding to the maximum drive torque of the electric motor. Short description of the drawings

[0035] Embodiments of the invention are described below with reference to the accompanying drawings, wherein neither the drawings nor the description are to be construed as limiting the invention. Fig. 1 shows an electric motorcycle with a brake assistance system according to an embodiment of the invention. Fig. 2 shows a detailed view of a brake system of the brake support system from Fig. 1 . Fig. 3 shows a diagram comparing the working ranges of an electric motor and a brake system of the brake support system from Fig. 1 .

[0036] The figures are merely schematic and not to scale. The same reference numerals throughout the figures indicate identical or equivalent features. Embodiments of the invention

[0037] Fig. 1 shows an electric motorcycle 1, here an electric scooter, which is driven by an electric motor 3 on its rear wheel 2. The electric motor 3 is part of a brake assist system 4, which, in addition to the electric motor 3, includes a braking system 5, here a hydraulic rear wheel brake for braking the rear wheel 2, and a control unit 6 for controlling the electric motor 3.

[0038] For this purpose, the control unit 6 determines a total braking torque 7 required to brake the electric motorcycle 1 to a standstill. The total braking torque 7 can, for example, be calculated by the control unit 6 in several consecutive time steps from measurement data 8, which are provided by an engine speed sensor 9 for measuring an engine speed of the electric motor 3, when a full or emergency braking is detected.

[0039] Subsequently, the control unit 6 determines from the total braking torque 7, taking into account a maximum braking torque 11 that can be generated by the braking system 5 on the rear wheel 2, a motor torque 12 that is to be generated by the electric motor 3 in addition to the braking system 5 on the rear wheel 2.

[0040] In the simplest case, the engine torque 12 can be determined by subtracting the maximum braking torque 11 from the total braking torque 7. Alternatively, for a given value of the total braking torque 7, a corresponding value for the engine torque 12 can be read from a lookup table stored in the control unit 6.

[0041] Depending on the total braking torque 7, the motor torque 12 can be opposite to the direction of the maximum braking torque 11 or, as in Fig. 1 shown, act in the same direction as the maximum braking torque 11.

[0042] The braking system 5 and / or the electric motor 3 can be designed such that the sum of the maximum (negative) motor torque 12 and the maximum braking torque 11 corresponds to the maximum total braking torque 7 that can be required to brake the electric motorcycle 1.

[0043] Additionally or alternatively, the braking system 5 and / or the electric motor 3 can be designed such that the maximum (positive) motor torque 12 corresponds to the maximum braking torque 11, ie, its magnitude is not less than the maximum braking torque 11. This makes it possible to cancel the braking effect of the braking system 5 by means of the electric motor 3, if necessary.

[0044] Finally, the control unit 6 generates a corresponding control command 13 for controlling the electric motor 3 based on the engine torque 12, which causes the rear wheel 2, in the event of an emergency or full braking, to be subjected to both the maximum braking torque 11 and the engine torque 12 and thus to the previously determined total braking torque 7.

[0045] Fig. 2 shows the braking system 5 in detail. This includes, for example, a rear brake disc 14 connected in a rotationally fixed manner to the rear wheel 2 and a rear brake caliper 15, which is hydraulically connected via a hydraulic brake circuit 16 to a master cylinder 17 on the handlebar of the electric motorcycle 1.

[0046] A brake pressure limiting valve 18 is arranged in the hydraulic brake circuit 16 between the rear brake calliper 15 and the master cylinder 17, via which the hydraulic brake pressure in the brake system 5 is limited.

[0047] The brake pressure limiting valve 18 is configured such that the hydraulic brake pressure can only be so great that the maximum braking torque 11 generated at the rear wheel 2 by means of the rear brake caliper 14 is at most equal to a maximum drive torque 19 of the electric motor 3.

[0048] The brake pressure relief valve 18 can be designed, for example, as a check valve or an electrically controllable isolating valve with variable or constant blocking pressure.

[0049] Alternatively, the brake system 5 can be used as a hydraulic front wheel brake for braking a front wheel 20 of the electric motorcycle 1 (see Fig. 1 ) or include such a front wheel brake in addition to the rear wheel brake.

[0050] In Fig. 3 It can be seen how a motor operating range 21 of the electric motor 3 and a brake operating range 22 of the braking system 5, i.e., a required ABS operating range, are shifted relative to each other by limiting the hydraulic brake pressure by means of the brake pressure limiting valve 18 in order to achieve the desired combination of both braking effects. The respective torque is plotted on the ordinate, and the speed of the electric motorcycle 1 is plotted on the abscissa.

[0051] Finally, it should be noted that terms such as "comprising," "having," etc., do not exclude other elements or steps, and terms such as "a" or "an" do not exclude a plurality. Reference signs in the claims are not to be considered limiting.

Claims

1. Method for operating a brake assist system (4) for an electric motorcycle (1), wherein the method comprises: determining a total braking torque (7) required for braking the electric motorcycle (1); characterized by determining a motor torque (12) to be generated by means of an electric motor (3) of the electric motorcycle (1) in dependence on the total braking torque (7) and on a maximum braking torque (11) that can be generated by means of a brake system (5) of the electric motorcycle (1); and, when the maximum braking torque (11) is generated, generating a control command (13) for activating the electric motor (3), so that the motor torque (12) is generated together with the maximum braking torque (11).

2. Method according to Claim 1, wherein the motor torque (12) is determined by forming the difference between the total braking torque (7) and the maximum braking torque (11).

3. Method according to either of the preceding claims, wherein a maximum drive torque (19) that can be generated by means of the electric motor (3) is not smaller in terms of magnitude than the maximum braking torque (11).

4. Method according to any of the preceding claims, further comprising: receiving measurement data (8) that indicate a current speed of the electric motor (3); wherein the total braking torque (7) is determined by evaluating the measurement data (8).

5. Controller (6) comprising a processor, which is configured to execute the method according to any of the preceding claims.

6. Brake assist system (4) for an electric motorcycle (1), wherein the brake assist system (4) comprises: an electric motor (3) for accelerating and / or braking the electric motorcycle (1); and a controller (6) according to Claim 5.

7. Brake assist system (4) according to Claim 6, further comprising: a brake system (5) for braking the electric motorcycle (1); wherein the brake system (5) is adapted such that a maximum braking torque (11) that can be generated by means of the brake system (5) is not greater in terms of magnitude than a maximum drive torque (19) that can be generated by means of the electric motor (3).

8. Brake assist system (4) according to Claim 7, wherein the brake system (5) comprises a hydraulic brake circuit (16) and at least one brake pressure valve (18) for limiting a brake pressure in the hydraulic brake circuit (16) to a value corresponding to the maximum drive torque (19).

9. Computer program comprising instructions that, when the computer program is executed by the processor, cause a processor to execute the method according to any of Claims 1 to 4.

10. Computer-readable medium, on which the computer program according to Claim 9 is stored.