Method for controlling a brake system of an electric vehicle and brake system

Abstract

The invention relates to a method for controlling a braking system of an electric vehicle, comprising: determining a requested total braking strength of the braking system at least on the basis of a braking request of the braking system of the electric vehicle and a vehicle travel speed (S1); determining the braking strength of each braking mode of a braking system at least based on the vehicle state information of the electric vehicle, the braking system having at least three braking modes, and the braking modes having a preset priority (S2); when at most two braking modes are put into use, a requested braking force for each braking mode is determined at least on the basis of the requested total braking strength and the priority of the braking modes (S3). According to the invention, not only can the braking jitter in the braking process be effectively inhibited and the driving comfort of the vehicle be improved, but also the control strategy for coordinating the braking modes can be simplified and the software and hardware cost of the continuous braking coordinator for coordinating the braking modes can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the field of vehicle braking, and in particular to a method for controlling a braking system of an electric vehicle, a braking system for an electric vehicle, and a computer program product for at least assisting in implementing the steps of the method according to the present invention. Background Art

[0002] Most current vehicles only use service brakes for vehicle braking. However, high-frequency and high-intensity braking may cause wear of the service brakes and even brake failure. To reduce or relieve the load on the service brakes, a retarder can be installed in the vehicle. In addition, for vehicles equipped with an electric motor, the electric motor can be operated in the generator mode to achieve braking energy recovery and improve its endurance. These braking modes can be simultaneously engaged through a continuous braking coordinator (EBC). However, in actual application, serious braking jitter will occur during braking. Therefore, the continuous braking coordinator needs to cooperate with the electronic stability program (ESP) of the vehicle body to ensure vehicle body stability. This results in the existing continuous braking coordinator being only used in specific types of hybrid vehicles equipped with an electronic stability program of the vehicle body and having extremely high software and hardware costs.

[0003] Considering that pure electric vehicles can also be equipped with these braking modes, how to develop a continuous braking coordinator suitable for pure electric vehicles has become a technical problem to be solved currently. Summary of the Invention

[0004] The object of the present invention is to provide a method for controlling a braking system of an electric vehicle, a braking system for an electric vehicle, and a computer program product to at least partially solve the problems in the prior art.

[0005] According to a first aspect of the present invention, there is provided a method for controlling a braking system of an electric vehicle, the method comprising:

[0006] - Step S1: determining a total requested braking intensity of the braking system based at least on a braking request of the braking system of the electric vehicle and a vehicle traveling speed;

[0007] - Step S2: determining a braking intensity of each braking mode of the braking system based at least on vehicle state information of the electric vehicle, wherein the braking system has at least three braking modes, and the braking modes have a preset priority; and

[0008] - Step S3: when at most two braking modes are in use, determining a requested braking force of each braking mode based at least on the total requested braking intensity and the priority of the braking mode.

[0009] The core concept of the present invention lies in: during the braking process of an electric vehicle, at most two braking modes are put into use. Thereby, not only can the braking jitter during the braking process be effectively suppressed, improving the driving comfort of the vehicle, but also the control strategy for coordinating these braking modes can be simplified, effectively reducing the software and hardware costs of the continuous braking coordinator for coordinating these braking modes.

[0010] According to a second aspect of the present invention, there is provided a braking system for an electric vehicle, wherein the system may include the following components:

[0011] - A vehicle state acquisition module configured to acquire vehicle state information of the electric vehicle, the vehicle state information including the vehicle driving speed;

[0012] - A braking request acquisition module configured to acquire a braking request of the braking system;

[0013] - At least three braking modules respectively used to perform braking in different braking modes, the braking modes having preset priorities; and

[0014] - A control module configured to execute the method according to the present invention.

[0015] According to a third aspect of the present invention, there is provided a computer program product, such as a computer-readable program carrier, containing computer program instructions, which at least assist in implementing the steps of the method according to the present invention when executed by a processor. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Hereinafter, the present invention will be described in more detail by referring to the accompanying drawings, and the principles, features and advantages of the present invention can be better understood. The accompanying drawings include:

[0017] Figure 1 Shows a working flowchart of a method for controlling a braking system of an electric vehicle according to an exemplary embodiment of the present invention;

[0018] Figure 2 Shows a structural block diagram of a braking system according to an exemplary embodiment of the present invention;

[0019] Figure 3 Shows a working flowchart of a method for controlling a braking system of an electric vehicle according to another exemplary embodiment of the present invention;

[0020] Figure 4 Shows a working flowchart of a method for controlling a braking system of an electric vehicle according to another exemplary embodiment of the present invention; and

[0021] Figure 5A flowchart showing the operation of a method for controlling a braking system of an electric vehicle according to another exemplary embodiment of the present invention is shown. Detailed implementation

[0022] In order to make the technical problems to be solved, technical solutions and beneficial technical effects of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and multiple exemplary embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention, rather than limiting the protection scope of the present invention. In addition, it should be understood that in this article, the expressions "first", "second", "third", etc. are only for descriptive purposes, and should not be construed as indicating or implying relative importance, nor should they be construed as implicitly indicating the quantity of the indicated technical features.

[0023] Figure 1 A flowchart showing the operation of a method for controlling a braking system of an electric vehicle according to an exemplary embodiment of the present invention is shown. The following exemplary embodiments describe the method according to the present invention in more detail.

[0024] The method may include steps S1 to S3. In step S1, the total requested braking intensity of the braking system 1 may be determined based at least on the braking request of the braking system of the electric vehicle and the vehicle driving speed. In the context of the present invention, an electric vehicle refers to a pure electric vehicle with an on-vehicle power source as the sole power source, which is particularly different from a hybrid vehicle with an internal combustion engine and an electric motor as power sources. Among them, the on-vehicle power source may include one or more of fuel cells, lead-acid batteries, nickel batteries, and lithium batteries, etc. The following will be described in detail in conjunction with Figure 2 A structural block diagram of an exemplary braking system 1 of a fuel cell vehicle shown is elaborated.

[0025] As Figure 2 shown, the braking system 1 includes a vehicle state acquisition module 11, which is configured to acquire various vehicle state information of the electric vehicle. The vehicle state acquisition module 11 may include on-vehicle sensors installed on the electric vehicle. For example, the vehicle driving speed is measured by a vehicle speed sensor, the wheel speed of the electric vehicle, that is, the wheel rotation speed, is measured by a wheel speed sensor, and the motor temperature of the electric vehicle is measured by an on-vehicle temperature sensor. The vehicle state acquisition module 11 may also include various on-vehicle control units of the electric vehicle. For example, the state of charge of the battery of the electric vehicle is acquired through a battery management system, and the retarder gear of the electric vehicle is acquired through a retarder control unit, and so on.

[0026] Here, the braking system 1 further includes a braking request acquisition module 12, which is configured to acquire the braking request of the braking system 1. In particular, the braking request of the driver for the braking system 1 can be determined based on the depth (acquired by measuring the stroke displacement of the brake pedal) and / or speed (acquired by measuring the change in the stroke displacement of the brake pedal) of the driver stepping on the brake pedal. For example, if the driver steps on the brake pedal deeply and quickly, a strong braking request of the driver for the braking system 1 is acquired.

[0027] In the control module 14 of the braking system 1, the total required braking intensity of the braking system 1 can be determined based at least on the braking request of the braking system 1 and the vehicle driving speed, that is, the total required braking intensity for achieving the driver's desired braking at the current driving speed.

[0028] In step S2, the braking intensity of each braking mode of the braking system is determined based at least on the vehicle state information of the electric vehicle. Among them, the braking system 1 has at least three braking modes, and the braking modes have preset priorities. In the current embodiment of the present invention, the braking modes of the braking system 1 include, for example, a retarder braking mode, a service braking mode, and an electric motor braking mode, etc. In Figure 2 The structural block diagram of the braking system 1 exemplarily shows three braking modules 13, which are respectively used to execute the braking of different braking modes. The priority order of these braking modes can be adjusted according to the vehicle design requirements, rather than being fixed. For example, it is set as a first braking mode with the first priority, a second braking mode with the second priority, and a third braking mode with the third priority. It should be noted that the listed braking modes are only exemplary and should not be limited thereto.

[0029] Exemplarily, in the electric motor braking mode, braking force can be generated through regenerative braking. Regenerative braking means that on the premise of ensuring the braking performance of the vehicle, the excess energy released during the vehicle deceleration or braking process is used to make the motor operate in the generator working condition, thereby converting this excess energy into electrical energy and storing it in the on-vehicle energy storage device (such as an on-vehicle battery). During the regenerative braking stage, the higher the wheel speed of the vehicle, the greater the braking intensity of the electric motor braking mode. However, when the state of charge of the battery is higher than a certain threshold, it is necessary to limit the regenerative braking of the electric motor braking mode to prevent the regenerative current from causing overcharging of the on-vehicle battery. In addition, when the temperature of the motor is too high, the resistance value inside the motor will increase, which will lead to a decrease in the braking intensity of the electric motor braking mode. Therefore, the braking intensity of the electric motor braking mode of the braking system 1 can be determined based at least on the wheel speed, the state of charge of the battery, and / or the temperature of the motor of the electric vehicle. In addition, the maximum available braking force of the electric motor braking mode will also be affected by factors such as the wheel speed, the state of charge of the battery, and / or the temperature of the motor of the electric vehicle.

[0030] For another example, the braking intensity of the retarder braking mode of the braking system 1 can be determined at least based on the retarder gear of the electric vehicle. Generally, the retarder gear can be divided into a constant speed gear and braking gears of different gears. Among them, the higher the gear of the braking gear, the higher the braking intensity of the braking gear. According to different working principles, retarders can be divided into eddy current retarders, hydraulic retarders, pneumatic retarders, etc. For example, in the case of a hydraulic retarder, the kinetic energy of the vehicle is converted into heat energy and the converted heat energy is taken away by the circulating coolant. In particular, long-term use of the braking gear of a high gear will cause the temperature of the coolant in the hydraulic retarder to rise, thereby affecting the maximum available braking force of the hydraulic retarder. For example, in the case of an eddy current retarder, a stator magnetic field is generated by the exciting current flowing in the stator coil. The rotor rotates with the transmission shaft and cuts the magnetic force lines of the stator magnetic field, thereby generating eddy current-like induced current inside the rotor. The stator magnetic field will apply an electromagnetic force that hinders the rotation of the rotor, thereby generating a braking force. This braking force can be adjusted by the exciting current flowing in the stator coil. Among them, the larger the exciting current, the stronger the stator magnetic field, and the larger the maximum available braking force of the eddy current retarder.

[0031] For another example, in the service braking mode, the driving speed of the vehicle can be reduced by a hydraulic braking mechanism based on Pascal's law, and its braking intensity is affected by factors such as the ground adhesion coefficient, wheel load, and wheel radius. On the premise of meeting the requirements of the vehicle's overall braking safety, the maximum available braking force of the service braking mode is usually sufficient to meet the braking requests of the driver in non-emergency situations. Therefore, in the sense of the present invention, it can be considered that the maximum available braking force of the service braking mode is not limited.

[0032] In step S3, when at most two braking modes are in use, at least based on the total requested braking intensity and the priorities of the braking modes, the requested braking forces of the respective braking modes are determined. In the prior art, in the braking system of a hybrid vehicle, multiple braking modes such as an electric motor braking mode, a retarder braking mode, a regenerative braking mode, and a service braking mode are usually used simultaneously for braking, which will cause serious braking jitter during the braking process. Therefore, in these hybrid vehicles, the continuous braking coordinator needs to cooperate with the vehicle electronic stability system to ensure vehicle stability, which greatly increases the software and hardware costs of the vehicle system design. In the embodiments of the present invention, during the braking process of the electric vehicle, at most two braking modes are in use, that is, only one braking mode or two braking modes are in use. Among them, the requested braking force of the braking mode in use does not exceed its maximum available braking force. Thus, the control strategy for coordinating these braking modes can be simplified, and the software and hardware costs of the continuous braking coordinator for coordinating these braking modes can be effectively reduced.

[0033] The following will elaborate on step S3 in conjunction with Figure 3 the working flowchart of a method for controlling a braking system of an electric vehicle according to another exemplary embodiment of the present invention shown in FIG. As Figure 3 shown, step S3 may include steps S31 to S35. In step S31, it is determined whether the braking intensity Z1 of the first braking mode is greater than zero. If the braking intensity Z1 of the first braking mode is not greater than zero, then in step S32, in the case where the first braking mode is not in use, the requested braking forces of each braking mode can be determined at least based on the t requested total braking intensity Z and the priority of the braking mode, that is, the requested braking force F2 of the second braking mode and, if necessary, the requested braking force F3 of the third braking mode can be determined here.

[0034] The following will further elaborate on step S32 in conjunction with Figure 4 the working flowchart of a method for controlling a braking system of an electric vehicle according to another exemplary embodiment of the present invention shown in FIG. The following will only elaborate on the Figure 3 differences from the embodiment shown in FIG., and the same steps will not be repeated for the sake of brevity.

[0035] As Figure 4 shown, step S32 further includes steps S321 to S323. In step S321, it is determined whether the t requested total braking intensity Z is greater than the braking intensity Z2 of the second braking mode. If the t requested total braking intensity Z is greater than the braking intensity Z2 of the second braking mode, then in step S322, the requested braking force F2 of the second braking mode is determined as the maximum available braking force F 2max of the second braking mode, and the requested braking force F3 of the third braking mode is determined as the difference between the total requested braking force F t calculated based on the requested total braking intensity Z t and the requested braking force F3 of the third braking mode. If the t requested total braking intensity Z is not greater than the braking intensity Z2 of the second braking mode, then in step S323, the requested braking force F2 of the second braking mode is determined as the total requested braking force F t calculated based on the requested total braking intensity Z t .

[0036] If the braking intensity Z1 of the first braking mode is greater than zero, then in step S33, it is determined whether the t requested total braking intensity Z is greater than the sum of the braking intensity Z1 of the first braking mode and the braking intensity Z2 of the second braking mode. If thet is greater than the sum of the braking intensity Z1 of the first braking mode and the braking intensity Z2 of the second braking mode, then in step S34, the requested braking force F1 of the first braking mode is determined as the maximum available braking force F of the first braking mode 1max , and the requested braking force F3 of the third braking mode is determined as the total requested braking force F calculated based on the requested total braking intensity Z t . t and the difference between the requested braking force F1 of the first braking mode. If the requested total braking intensity Z t is not greater than the sum of the braking intensity Z1 of the first braking mode and the braking intensity Z2 of the second braking mode, then in step S35, in the case where the first braking mode is not in use, the requested braking forces of the respective braking modes can be determined at least based on the requested total braking intensity Z t and the priorities of the braking modes, that is, the requested braking force F1 of the second braking mode and, if necessary, the requested braking force F3 of the third braking mode can be determined here.

[0037] The following further elaborates step S35 in conjunction with Figure 5 the flowchart of the method for controlling the braking system of an electric vehicle according to another exemplary embodiment of the present invention shown below. Only the differences from the embodiment shown in Figure 3 are elaborated below, and the same steps are not repeated for the sake of brevity.

[0038] As Figure 5 shown, step S35 further includes steps S351 to S353. In step S351, it is judged whether the requested total braking intensity Z t is greater than the braking intensity Z1 of the first braking mode. If the requested total braking intensity Z t is greater than the braking intensity Z1 of the first braking mode, then in step S352, the requested braking force F1 of the first braking mode is determined as the maximum available braking force F 1max of the first braking mode, and the requested braking force F2 of the second braking mode is determined as the difference between the total requested braking force F calculated based on the requested total braking intensity Z t and the requested braking force F1 of the first braking mode. If the requested total braking intensity Z t is not greater than the braking intensity Z1 of the first braking mode, then in step S353, the requested braking force F1 of the first braking mode is determined as the total requested braking force F calculated based on the requested total braking intensity Z t . t t .

[0039] ​According to an embodiment of the present invention, at most two braking modes are put into use only during the braking process of an electric vehicle. Thereby, not only can the braking jitter during the braking process be effectively suppressed, improving the driving comfort of the vehicle, but also the control strategy for coordinating these braking modes can be simplified, effectively reducing the software and hardware costs of the continuous braking coordinator for coordinating these braking modes.

[0040] In an alternative embodiment of the present invention, the retarder braking mode can be adopted as the first braking mode with the first priority, the electric motor braking mode can be adopted as the second braking mode with the second priority, and the service braking mode can be adopted as the third braking mode with the third priority. By coordinately using the electric motor braking mode and the service braking mode when preferentially using the retarder braking mode, a smoother braking effect can be obtained, and the braking intensity and braking frequency of the service braking can be reduced as much as possible. Thereby, the service life of the service brake can be effectively extended, and the influence of the thermal fade of the service brake caused by high-intensity and high-frequency service braking can be reduced.

[0041] In another alternative embodiment of the present invention, the electric motor braking mode can be adopted as the first braking mode with the first priority, the retarder braking mode can be adopted as the second braking mode with the second priority, and the service braking mode can be adopted as the third braking mode with the third priority. By coordinately using the retarder braking mode and the service braking mode when preferentially using the electric motor braking mode, the redundant energy during the braking process of the electric vehicle can be recovered as much as possible, improving the endurance of the electric vehicle. At the same time, the braking intensity and braking frequency of the service braking can be reduced as much as possible. Thereby, the service life of the service brake can be effectively extended, and the influence of the thermal fade of the service brake caused by high-intensity and high-frequency service braking can be reduced.

[0042] In addition, it should be noted that the step numbers described herein do not necessarily represent the order of precedence, but are merely a kind of reference numeral. According to the specific situation, the order can be changed as long as the technical purpose of the present invention can be achieved.

[0043] Although specific embodiments have been described above, these embodiments are not intended to limit the scope of the present disclosure, even when describing a single embodiment with respect to a specific feature. The feature examples provided in the present disclosure are intended for illustrative purposes only and not for limitation, unless otherwise stated. In specific implementations, according to actual requirements and when technically feasible, multiple features can be combined with each other. Various substitutions, changes, and modifications can also be conceived without departing from the spirit and scope of the present invention.

Claims

1. A method for controlling a braking system (1) of an electric vehicle, the method comprising: Step S1: Determine the total requested braking intensity of the braking system (1) based at least on the braking request of the braking system (1) of the electric vehicle and the vehicle driving speed. Step S2: Determine the braking intensity of each braking mode of the braking system (1) based at least on the vehicle state information of the electric vehicle, wherein the braking system (1) has at least three braking modes, and the braking modes have a preset priority. And Step S3: When at most two braking modes are in use, determine the requested braking force of each braking mode based at least on the total requested braking intensity and the priority of the braking modes.

2. The method according to claim 1, wherein, The braking modes of the braking system (1) include a retarder braking mode, a service braking mode, and an electric motor braking mode.

3. The method according to claim 2, wherein, Adopt the retarder braking mode as the first braking mode with the first priority, adopt the electric motor braking mode as the second braking mode with the second priority, and adopt the service braking mode as the third braking mode with the third priority.

4. The method according to claim 2, wherein, Adopt the electric motor braking mode as the first braking mode with the first priority, adopt the retarder braking mode as the second braking mode with the second priority, and adopt the service braking mode as the third braking mode with the third priority.

5. The method according to claim 2, wherein, Respectively determine the requested braking force of each braking mode so that the requested braking force of each braking mode does not exceed its maximum available braking force.

6. The method according to any one of claims 2 to 5, wherein, Determine the braking intensity of the electric motor braking mode of the braking system (1) based at least on the wheel speed, the state of charge of the battery, and / or the motor temperature of the electric vehicle.

7. The method according to any one of claims 2 to 5, wherein, Determine the braking intensity of the retarder braking mode of the braking system (1) based at least on the retarder gear of the electric vehicle.

8. The method according to any one of claims 3 to 5, wherein, The step S3 further includes: Step S31: Determine whether the braking intensity of the first braking mode is greater than zero. Step S32: If the braking intensity of the first braking mode is not greater than zero, then when the first braking mode is not in use, determine the requested braking force of each braking mode based at least on the total requested braking intensity and the priority of the braking modes. Step S33: If the braking intensity of the first braking mode is greater than zero, then determine whether the total requested braking intensity is greater than the sum of the braking intensity of the first braking mode and the braking intensity of the second braking mode. Step S34: If the total requested braking intensity is greater than the sum of the braking intensity of the first braking mode and the braking intensity of the second braking mode, then determine the requested braking force of the first braking mode as the maximum available braking force of the first braking mode, and determine the requested braking force of the third braking mode as the difference between the total requested braking force calculated based on the total requested braking intensity and the requested braking force of the first braking mode; and Step S35: If the total requested braking intensity is not greater than the sum of the braking intensity of the first braking mode and the braking intensity of the second braking mode, then when the first braking mode is not in use, determine the requested braking force of each braking mode based at least on the total requested braking intensity and the priority of the braking modes.

9. The method according to claim 8, wherein, The step S32 further includes: Step S321: Determine whether the total requested braking intensity is greater than the braking intensity of the second braking mode; Step S322: If the total requested braking intensity is greater than the braking intensity of the second braking mode, determine the requested braking force of the second braking mode as the maximum available braking force of the second braking mode, and determine the requested braking force of the third braking mode as the difference between the total requested braking force calculated based on the total requested braking intensity and the requested braking force of the third braking mode; and Step S323: If the total requested braking intensity is not greater than the braking intensity of the second braking mode, determine the requested braking force of the second braking mode as the total requested braking force calculated based on the total requested braking intensity.

10. The method according to claim 8, wherein, The step S35 further includes: Step S351: Determine whether the total requested braking intensity is greater than the braking intensity of the first braking mode; Step S352: If the total requested braking intensity is greater than the braking intensity of the first braking mode, determine the requested braking force of the first braking mode as the maximum available braking force of the first braking mode, and determine the requested braking force of the second braking mode as the difference between the total requested braking force calculated based on the total requested braking intensity and the requested braking force of the first braking mode; and Step S353: If the total requested braking intensity is not greater than the braking intensity of the first braking mode, determine the requested braking force of the first braking mode as the total requested braking force calculated based on the total requested braking intensity.

11. A braking system (1) for an electric vehicle, wherein, The system (1) includes the following components: A vehicle state acquisition module (11) configured to acquire vehicle state information of an electric vehicle, where the vehicle state information includes vehicle driving speed; A braking request acquisition module (12) configured to acquire a braking request of the braking system (1); At least three braking modules (13) respectively used to perform braking in different braking modes, and the braking modes have preset priorities; And A control module (14) configured to execute the method according to any one of the above claims.

12. A computer program product, such as a computer-readable program carrier, comprising computer program instructions which, when executed by a processor, at least assist in implementing the steps of the method according to any one of claims 1 to 10 above.

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