Method for operating a brake assist system for an electric two-wheeler, control unit, brake assist system for an electric two-wheeler, computer program, and computer readable medium

Abstract

[Solution] A method for operating a brake assist system (4) for an electric two-wheeled vehicle (1), the method includes determining a total brake torque (7) required to brake the electric two-wheeled vehicle (1), determining a motor torque (12) to be generated by an electric motor (3) of the electric two-wheeled vehicle (1) depending on the total brake torque (7) and a maximum brake torque (11) that can be generated by a brake device (5) of the electric two-wheeled vehicle (1), and, when the maximum brake torque (11) is generated, generating a control command (13) for driving and controlling the electric motor (3), thereby generating the motor torque (12) together with the maximum brake torque (11).

Description

[Technical field]

[0001] The present invention relates to a method for operating a brake-assist system for an electric two-wheeler, and further to a control unit, a computer program and a computer readable medium for carrying out the method, as well as a brake-assist system equipped with such a control unit. [Background technology]

[0002] ABS systems typically contain various hydraulic and electrical components to control the brake pressure. For example, a very simple ABS system has already been realized using an intake valve, an exhaust valve, a reserve chamber and a check valve.

[0003] In electric two-wheelers driven by an electric motor, the electric motor can in principle be used for torque modulation, but in practice, depending on the vehicle type or the size of the electric motor, the maximum torque generated by the electric motor may not be sufficient to meet the requirements of the ABS. Summary of the Invention

[0004] Against this background, the present proposal provides a method for operating a brake assist system for an electric two-wheeler, a corresponding control unit, a corresponding brake assist system, a corresponding computer program and a corresponding computer-readable medium as set forth in the independent claims. Preferred embodiments and developments of the present proposal can be taken from the description and are set forth in the dependent claims. Effect of the Invention

[0005] According to an embodiment of the present invention, it is possible to brake an electric two-wheeler by combining a braking function based on an electric motor with a braking function that is not based on an electric motor, for example a hydraulic braking function. In this way, a suitable brake assist system for an electric two-wheeler can be provided at low cost, for example because the number of hydraulic components of the brake assist system can be reduced. Furthermore, the braking performance of the electric two-wheeler can be improved.

[0006] A first aspect of the present invention relates to a computer-implemented method for operating a brake assist system for an electric two-wheeler, the method including at least the following steps: determining a total brake torque required to brake the electric two-wheeler, determining a motor torque to be generated by an electric motor of the electric two-wheeler depending on the total brake torque and a maximum brake torque that can be generated by a brake device of the electric two-wheeler, and, when the maximum brake torque is generated, generating a control command for driving and controlling the electric motor, thereby generating a motor torque together with the maximum brake torque.

[0007] An "electric two-wheeler" may generally be interpreted as a single or two-wheeled vehicle having a drive unit in the form of an electric motor or a drive unit in the form of a combination of an electric motor and an internal combustion engine. An electric two-wheeler may be an electric scooter, an electric bicycle, or a two-axle vehicle similar to a motorcycle with more than two wheels, for example a four-wheel electric bicycle.

[0008] The motor torque may be a driving torque, a braking torque, or a regenerative torque.

[0009] "Total brake torque" may be understood to mean a brake torque estimated based on the actual wheel rotation speed of one or more wheels of the electric two-wheeler and / or the actual motor rotation speed of the electric motor. The actual wheel rotation speed may be measured, for example, by a separate wheel rotation speed sensor. It is also possible to determine the actual wheel rotation speed from the actual motor rotation speed. In this case, a separate wheel rotation speed sensor is omitted.

[0010] The total brake torque may be determined, for example, in the event of emergency braking or full braking, in order to avoid locking of the wheels, which are applied both by the maximum brake torque of the brake device and by the motor torque of the electric motor. The total brake torque may be interpreted as the brake torque that allows the electric two-wheeler to be braked and / or stopped as quickly and safely as possible.

[0011] The maximum total braking torque may be, for example, the sum of the maximum braking torque of the braking device and the maximum negative motor torque, i.e., the maximum braking torque or regenerative torque of the electric motor. The maximum total braking torque should be selected so that the electric motorcycle can be stopped quickly and safely in all driving situations.

[0012] It is possible for the electric motor and the brake system to act on one or more of the same wheels of the electric two-wheeler, i.e. on the rear wheels. It is also possible for the electric motor to drive the rear wheels and for the brake system to brake the front wheels or additionally the rear wheels. In this case, for example, the brake system can be configured as a single-channel ABS system for the front wheels. In this case, the rear wheels can be braked exclusively in regenerative mode via the electric motor.

[0013] The method described here and below makes it possible to use an electric motor for intentionally modulating the brake torque, the so-called average value of which is provided by the brake device independently of the electric motor, which average value can be reduced or increased in magnitude by the drive torque or the brake torque or the regenerative torque being generated by the electric motor simultaneously or slightly offset in time.

[0014] For this purpose, the working point of the brake system is preferably shifted in a corresponding manner, i.e. the maximum brake torque generated by the brake system, for example its maximum brake pressure, is appropriately adapted to the maximum motor torque of the electric motor. For example, the brake system can in the simplest case be equipped with a corresponding separation valve or pressure limiting valve. Such valves can be retrofitted very easily.

[0015] Particularly in electric scooters, the braking torque or regenerative torque of the electric motor alone may not be sufficient to brake the electric two-wheeler quickly or strongly enough, but preferably the electric motor can provide a modulation of the motor torque with very high dynamics that is completely sufficient for ABS control.

[0016] By combining the braking action obtained via the electric motor with the braking action of an additional, e.g. hydraulic, brake system capable of providing the required high braking torque, an ABS functionality which meets both requirements can be realised at a relatively low cost.

[0017] As soon as the braking device and the electric motor are actuated simultaneously, the total braking torque applied to the wheel in question during braking is obtained as the sum of the motor torque of the electric motor and the braking torque of the braking device.

[0018] If the electric motor generates a positive motor torque during braking, this positive motor torque acts against the brake system and reduces the total brake torque acting on the wheels accordingly, the brake system determining, so to speak, an average value of the brake torque and the electric motor modulates the total torque acting on the wheels approximately to this average value, i.e. increasing or decreasing it starting from this total torque.

[0019] Since standard (hydraulic) brake systems generate a maximum braking torque that is generally significantly greater than the maximum drive torque of a standard electric motor, the electric motor is usually not able to completely compensate for the braking torque generated by the brake system during full braking. However, by incorporating a corresponding valve into the brake system, it can be ensured that, on the one hand, the sum of the limited maximum braking torque of the brake 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 brake system can be completely corrected by the maximum drive torque of the electric motor, so that in this case the total rotational torque acting on the wheel in question is equal to zero.

[0020] This type of limitation thus makes it possible to use the electric motor to modulate the total brake torque between zero and the maximum brake torque required for emergency braking with dynamics that are sufficient for ABS functionality. Advantageously, such ABS functionality can be realized by a simple combination of an existing electric drive motor with an existing (hydraulic) brake system, with only one additional component in the form of a valve.

[0021] A corresponding control logic can be implemented, for example, in a control unit of the electric two-wheeler. Wheel speed sensors are not essential, since the wheel speed can be determined from the motor speed of the electric motor, for example, by means of Hall sensors, which may be provided inside the electric motor.

[0022] A second aspect of the invention relates to a control unit. The control unit contains a processor configured to perform the method according to the embodiment of the first aspect of the invention. Features of the method according to the embodiment of the first aspect of the invention may be features of the control unit and vice versa.

[0023] The control unit may contain hardware and / or software modules. In addition to the processor, the control unit may contain memory and a data communication interface for data communication with peripheral devices.

[0024] A third aspect of the present invention relates to a brake assist system for an electric two-wheeler. The brake assist system contains at least one electric motor for accelerating and / or braking the electric two-wheeler and a control unit according to the embodiment of the second aspect of the present invention. Such a brake assist system can be produced particularly cheaply. Moreover, such a brake assist system can contribute to a significant improvement of the braking performance of the electric two-wheeler. Accidents are thus avoided.

[0025] A fourth aspect of the invention relates to a computer program comprising instructions which, when executed by a processor, cause the processor to perform a method according to an embodiment of the first aspect of the invention.

[0026] A fifth aspect of the present invention relates to a computer readable medium on which a computer program according to the embodiment of the third aspect of the present invention is stored. The computer readable medium may be a volatile or non-volatile data memory. For example, the computer readable medium may be a hard disk, a USB storage device, a RAM, a ROM, an EPROM or a flash memory. The computer readable medium may be a data communication network, for example the Internet or a data cloud, allowing the downloading of the program code.

[0027] Features of the method according to embodiments of the first aspect of the invention may also be features of the computer program and / or the computer readable medium and vice versa.

[0028] The ideas of the embodiments of the present invention may be regarded as being based in particular on the ideas and knowledge set out below.

[0029] According to one embodiment, the motor torque can be determined by forming the difference between the total brake torque and the maximum brake torque. In this way, the total brake torque can be determined particularly efficiently.

[0030] According to one embodiment, the maximum drive torque generated by the electric motor is not less in magnitude than the maximum brake torque, which has the effect that the braking action of the brake system can possibly be compensated by the braking action of the electric motor, particularly in the case of full braking or emergency braking, when the brake system generates a maximum brake torque to prevent locking of the respectively braked wheel.

[0031] According to one embodiment, the method further comprises the step of receiving measurement data representative of the actual rotational speed of the electric motor. The total brake torque can be determined by evaluating this measurement data. The measurement data can be provided by corresponding rotational speed sensors, for example as Hall sensors. It is also possible to estimate the rotational speed based on the measured phase voltages and / or phase currents of the electric motor. In this way, the use of separate wheel rotational speed sensors is dispensed with. The production of the brake assist system can be made even more cost-effective.

[0032] According to one embodiment, the brake assist system further comprises a brake device for braking the electric two-wheeler. This brake device can be adjusted in such a way that the maximum brake torque that can be generated by this brake device is not greater in terms of magnitude than the maximum drive torque that can be generated by the electric motor. The brake device can be, for example, a hydraulic front and / or rear brake. As mentioned at the beginning, the brake device can comprise, for example, an intake valve, an outlet valve, a reserve chamber and a check valve. In this way, the brake pressure that can be generated by the driver by operating the brake lever or the brake pedal can be limited in a technically effective manner in such a way that the maximum brake torque of the brake device can be compensated for by the maximum drive torque of the electric motor.

[0033] According to an embodiment, the brake system includes a hydraulic brake circuit and at least one brake pressure valve for limiting the brake pressure in the hydraulic brake circuit to a value corresponding to a maximum drive torque. In other words, the maximum brake pressure in the hydraulic brake circuit may be limited in such a way that the maximum brake torque of the brake system is at most as large as the maximum drive torque. The brake pressure valve may be, for example, a separate valve which separates the master cylinder from the slave cylinder when a certain brake pressure is reached. The separate valve may be controllable, for example by a control unit of the electric two-wheeler, depending on the measured actual brake pressure in the hydraulic brake circuit. This has the advantage that the maximum brake torque can be varied depending on the driving situation, which is for example dependent on the road surface condition. Alternatively, the brake pressure valve may be configured as a simple pressure limiter valve, for example as a non-return valve, i.e. as a passive component which limits the brake pressure to a fixed value corresponding to the maximum drive torque of the electric motor. [Brief description of the drawings]

[0034] [Figure 1] 1 is a diagram showing an electric motorcycle equipped with a brake assist system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a detailed diagram of a brake device of the brake assist system shown in FIG. [Diagram 3] FIG. 2 is a diagram for comparing the operating range of the brake device and the operating range of the electric motor of the brake assist system shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, in which: FIG.

[0036] In the drawings, the same reference numbers represent the same features or features with the same function.

[0037] 1 shows an electric two-wheeled vehicle 1, here an electric scooter whose rear wheel 2 is driven by an electric motor 3. The electric motor 3 is part of a brake assist system 4, which includes, in addition to the electric motor 3, a brake device 5, here a hydraulic rear wheel brake for braking the rear wheel 2, and a control unit 6 for controlling the drive of the electric motor 3.

[0038] For this purpose, the control unit 6 determines a total brake torque 7 required to brake the electric two-wheeler 1 to a standstill. The total brake torque 7 is calculated by the control unit 6 in a number of successive time steps from measurement data 8, which is provided, for example, by means of a motor speed sensor 9 for measuring the motor speed of the electric motor 3, during a recognised full braking or emergency braking event.

[0039] The control unit 6 then determines from the total braking torque 7 the motor torque 12 to be generated by the electric motor 3 at the rear wheels 2 in addition to the braking device 5 taking into account the maximum braking torque 11 that can be generated by the braking device 5 at the rear wheels 2 .

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

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

[0042] The braking device 5 and / or the electric motor 3 may 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 is maximally required to brake the electric two-wheeler 1.

[0043] Additionally or alternatively, the braking device 5 and / or the electric motor 3 may be designed such that the maximum (positive) motor torque 12 corresponds to the maximum braking torque 11, i.e. in terms of magnitude is not less than the maximum braking torque 11. This makes it possible for the braking action of the braking device 5 to be possibly counteracted by the electric motor 3.

[0044] Finally, based on the motor torque 12, the control unit 6 generates a corresponding control command 13 for controlling the electric motor 3, so that in the event of emergency braking or full braking, the rear wheels 2 are loaded both with the maximum brake torque 11 and also with the motor torque 12 and thus with the predetermined total brake torque 7.

[0045] 2 shows details of the braking device 5. The braking device 5 includes, for example, a rear brake disc 14 connected to the rear wheel 2 so as not to be rotatable relative thereto, and a rear brake caliper 15 fluidly connected via a hydraulic brake circuit 16 to a master cylinder 17 provided on a handle of the electric motorcycle 1.

[0046] A brake pressure limiter valve 18 is disposed in the hydraulic brake circuit 16 between the rear brake caliper 15 and the master cylinder 17, and the brake pressure of the hydraulic pressure in the brake device 5 is limited via this brake pressure limiter valve 18.

[0047] The brake pressure limiter valve 18 is configured so that the hydraulic brake pressure is only such that the maximum brake torque 11 generated by the rear brake caliper 14 at the rear wheel 2 is at most equal in magnitude to the maximum drive torque 19 of the electric motor 3.

[0048] The brake pressure limiter valve 18 can be configured, for example, as an electrically actuable separate valve with a variable or constant shutoff pressure or as a check valve.

[0049] Alternatively, the braking device 5 may be embodied as a hydraulic front brake for braking the front wheel 20 (see FIG. 1) of the electric two-wheeler 1 or may include such a front brake in addition to a rear brake.

[0050] 3 shows how the motor operating range 21 of the electric motor 3 and the brake operating range 22 of the brake device 5, i.e. the required ABS operating range, can be shifted relative to one another in order to obtain the desired combination of the two braking actions by limiting the hydraulic brake pressure with the brake pressure limiter valve 18. In this case, the respective torque is plotted on the ordinate and the speed of the electric two-wheeler 1 on the abscissa.

[0051] Finally, it is pointed out that the words "comprise", "contain" and the like do not exclude other elements or steps, and "a" does not exclude a plurality. Claim signs are not to be regarded as limiting. [Explanation of symbols]

[0052] 1 Electric motorcycle 2 Rear wheels 3 Electric motor 4. Brake Assist System 5 Brake device 6. Control Unit 7 Total Brake Torque 8. Measurement Data 9 Motor speed sensor 11 Maximum brake torque 12 Motor torque 13 Control Commands 14 Rear brake disc 15 Rear brake caliper 16 Hydraulic brake circuit 17 Master cylinder 18 Brake pressure limiter valve 19 Maximum driving torque 20 Front wheel 21 Motor operating range 22 Brake operating range

Claims

1. A method for operating a brake assist system (4) for an electric two-wheeler (1), comprising: determining a total braking torque (7) required to brake the electric two-wheeler (1); determining a motor torque (12) to be generated by an electric motor (3) of the electric two-wheeled vehicle (1) depending on the total brake torque (7) and a maximum brake torque (11) that can be generated by a brake device (5) of the electric two-wheeled vehicle (1); generating a control command (13) for driving and controlling the electric motor (3) when the maximum brake torque (11) is generated, thereby generating the motor torque (12) together with the maximum brake torque (11); A method for operating a brake assist system (4) for an electric two-wheeler (1), comprising:

2. 2. The method according to claim 1, further comprising the step of forming the motor torque (12) by forming the difference between the total brake torque (7) and the maximum brake torque (11).

3. 2. The method according to claim 1, further comprising the step of: preventing the maximum drive torque (19) generated by the electric motor (3) from being less than the maximum brake torque (11) in terms of magnitude.

4. 2. The method according to claim 1, further comprising the step of receiving measurement data (8) representative of an actual speed of the electric motor (3) and determining the total brake torque (7) by evaluating the measurement data (8).

5. In the control unit (6), A control unit (6) containing a processor configured to carry out the method according to any one of claims 1 to 4.

6. A brake assist system (4) for an electric two-wheeler (1), A brake assist system (4) for an electric two-wheeled vehicle (1), the brake assist system (4) including an electric motor (3) for accelerating and / or braking the electric two-wheeled vehicle (1) and a control unit (6) according to claim 5.

7. 7. The brake assist system (4) according to claim 6, further comprising a brake device (5) for braking the electric two-wheeled vehicle (1), the brake device (5) being adjusted such that a maximum brake torque (11) that can be generated by the brake device (5) is not greater in magnitude than a maximum drive torque (19) that can be generated by the electric motor (3).

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

9. A computer program comprising instructions which, when executed by a processor, cause the processor to carry out a method according to any one of claims 1 to 4.

10. 10. A computer readable medium having stored thereon the computer program of claim 9.

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