Method for controlling brake system of electric vehicle and brake system
The method for controlling electric vehicle braking systems by using at most two modes based on vehicle state and priority addresses brake jitter and cost issues, improving comfort and extending brake life.
Patent Information
- Application Number
- JP2024223871
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-12-20
- Filing Date
- 2024-12-19
- Publication Date
- 2025-07-02
AI Technical Summary
Existing braking systems in electric vehicles face issues such as brake wear, failure, and high hardware and software costs due to the simultaneous use of multiple braking modes, leading to brake jitter and instability.
A method for controlling a braking system in electric vehicles that utilizes at most two braking modes, determining their required braking forces based on vehicle state information and priority, effectively suppressing brake jitter and reducing hardware and software costs.
The method enhances driving comfort by minimizing brake jitter and extends the service life of the service brake while reducing system complexity and costs.
Smart Images
Figure 2025098981000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to the field of vehicles, specifically, to a method for controlling a braking system of an electric vehicle, a braking system for an electric vehicle, and a computer program product designed to at least assist in implementing steps of the method according to the present disclosure.
Background Art
[0002] Most current vehicles use only the service brake for vehicle braking. However, frequent or very strong braking may lead to wear of the service brake and brake failure. To reduce or mitigate the load on the service brake, a retarder can be installed in the vehicle. Also, for a vehicle equipped with a motor, the motor can be operated in generator mode to recover braking energy and improve its cruising range. These braking modes can be used simultaneously by a continuous brake coordinator (EBC), but severe brake jitter may occur during actual application. Therefore, the continuous brake coordinator needs to cooperate with the vehicle body's anti-skid system (ESP) to ensure the stability of the vehicle body. As a result, existing continuous brake coordinators are only used in specific types of hybrid vehicles equipped with an anti-skid system, and the costs of hardware and software are very high.
[0003] Considering that these braking modes can also be equipped in pure electric vehicles, how to develop a continuous brake coordinator for pure electric vehicles is a current technical problem that needs to be solved.
Summary of the Invention
Problems to be Solved by 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, which at least partially solve the problems in the prior art.
Means for Solving the Problems
[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: - Step S1: determining a required total braking strength of the braking system based on at least a braking request of the braking system and a vehicle driving speed of the electric vehicle; - Step S2: determining a braking strength of each braking mode of the braking system based on at least 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 order; - Step S3: when at most two braking modes are used, determining a required braking force of each braking mode based on at least the required total braking strength and the priority of the braking mode; and including.
[0006] The core idea of the present disclosure is that in the braking process of an electric vehicle, at most two braking modes are used, thereby effectively suppressing the braking jitter of the braking process, improving the driving comfort of the vehicle, simplifying the control strategy for adjusting these braking modes, and effectively reducing the hardware and software costs of the continuous brake coordinator for adjusting these braking modes.
[0007] According to a second aspect of the present invention, there is provided a braking system for an electric vehicle, the system comprising: - A vehicle state acquisition module configured to acquire vehicle state information about an electric vehicle, wherein the vehicle state information includes a vehicle driving speed, the vehicle state acquisition module, and - A brake request acquisition module configured to acquire a brake request of the brake system, and - At least three brake modules respectively for executing brakes in different brake modes, wherein the brake modes have a preset priority, at least three brake modules, and - A control module configured to implement the method according to the present invention, and Comprising.
[0008] According to a third aspect of the present disclosure, there is provided a computer program product such as a computer-readable program carrier including computer program instructions, and when the computer program instructions are executed by a processor, this computer program product is for at least assisting in implementing the steps of the method according to the present disclosure.
Brief Description of the Drawings
[0009] In the following, in order to provide a better understanding of the principles, configurations and advantages of the present disclosure, the present disclosure will be described in more detail with reference to the accompanying drawings. The accompanying drawings include the following.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Embodiments for Carrying Out the Invention
[0010] To provide a clearer understanding of the technical problems to be addressed, the technical solutions, and the beneficial technical effects by the present invention, a detailed description of the present invention is provided below with reference to the accompanying drawings and a plurality of exemplary embodiments. Of course, the specific embodiments described in this disclosure are provided only for the purpose of explaining this disclosure and do not limit the scope of protection of this disclosure. It should be noted that in this document, terms such as "first", "second", etc. are used only for the purpose of description and should not be construed as indicating or suggesting relative importance. Furthermore, such terms should not be understood as indicating a specific quantity of the technical configurations shown.
[0011] FIG. 1 shows a workflow diagram of a method for controlling a braking system of an electric vehicle according to an exemplary embodiment of the present invention. The following exemplary embodiments will explain the method according to the present invention in more detail.
[0012] The method may be assumed to include steps S1 to S3. In step S1, based on at least the braking requirement of the braking system of the electric vehicle and the traveling speed of the vehicle, the total required braking intensity of braking system 1 can be determined. In the context of the present invention, an electric vehicle refers to a pure electric vehicle having an in-vehicle power source as the only power source, as a particularity with respect to a hybrid vehicle that uses an internal combustion engine and an electric motor as power sources. The in-vehicle power source may include one or more of a fuel cell, a lead-acid battery, a nickel battery, and a lithium battery. A structural block diagram of one exemplary braking system 1 of a fuel cell vehicle shown in FIG. 2 will be described in detail below.
[0013] As shown in FIG. 2, the braking system 1 includes a vehicle state acquisition module 11 configured to acquire various vehicle state information of the electric vehicle. The vehicle state acquisition module 11 may include in-vehicle sensors equipped on the electric vehicle, such as a vehicle speed sensor for measuring the driving speed of the vehicle, a wheel speed sensor for measuring the wheel speed, i.e., the wheel rotation speed, of the electric vehicle, and an in-vehicle temperature sensor for measuring the motor temperature of the electric vehicle. Further, the vehicle state acquisition module 11 may include various in-vehicle control units of the electric vehicle, such as acquiring the battery charge state of the electric vehicle acquired by the battery management system and acquiring the retarder gear of the electric vehicle via the retarder control unit.
[0014] Here, the braking system 1 further includes a brake demand acquisition module 12 configured to acquire the brake demand of the braking system 1. The driver's demand for the brake of the braking system 1 can be determined particularly based on the depth (acquired by measuring the movement amount of the brake pedal) and / or speed (acquired by measuring the change amount of the movement of the brake pedal) of the driver stepping on the brake pedal. For example, when the driver steps on the brake pedal deeply and quickly, a stronger brake demand from the driver to the braking system 1 is acquired.
[0015] The required total brake strength of the braking system 1, that is, the required total brake strength necessary to achieve the driver's desired brake at the current driving speed, can be determined by the control module 14 of the braking system 1 based on at least the brake demand of the braking system 1 and the vehicle driving speed.
[0016] In step S2, the braking strength of each braking mode of the braking system is determined based on at least the vehicle state information of the electric vehicle. The braking system 1 has at least three braking modes, and the braking modes have a preset priority order. In the present 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 a motor braking mode. In the structural block diagram of the braking system 1 in FIG. 2, three braking modules 13 are exemplarily shown for performing braking in different braking modes, and the order of their priority is not fixed. For example, the first braking mode can be set to have the first priority, the second braking mode can be set to have the second priority, and the third braking mode can be set to have the third priority. It should be noted that the listed braking modes are merely exemplary and should not be limited thereto.
[0017] Exemplarily, in the motor braking mode, the braking force means that during vehicle deceleration or the braking process, the excessive energy released is used to operate the motor in the state of a generator while ensuring the braking efficiency of the vehicle, thereby converting the excessive energy into electrical energy and storing it in an in-vehicle energy storage device (for example, an in-vehicle battery). It can be generated by regenerative braking. The higher the wheel speed of the vehicle during the regenerative braking stage, the greater the braking strength of the motor braking mode. However, when the battery charge state exceeds a specific threshold, the regenerative braking of the motor braking mode needs to be limited to prevent the regenerative current from overcharging the in-vehicle battery. Furthermore, when the motor temperature is too high, the resistance value inside the motor increases, and as a result, the braking strength of the motor braking mode decreases. Therefore, the braking strength of the motor braking mode of the braking system 1 can be determined based on at least the wheel speed of the electric vehicle, the battery charge state, and / or the motor temperature. Furthermore, the maximum braking force of the motor braking mode is also affected by the wheel speed of the electric vehicle, the battery charge state, and / or the motor temperature.
[0018] For example, the braking strength in the retarder braking mode of the braking system 1 can be determined based at least on the retarder gear of the electric vehicle. Typically, the retarder gear can be divided into a constant speed gear and a braking gear corresponding to different gears. The higher the gear of the braking gear, the higher the braking strength of the braking gear. According to the operating principle, the retarder can be classified as an eddy current retarder, a hydraulic retarder, an aerodynamic retarder, etc. For example, in the case of a hydraulic retarder, when the vehicle's kinetic energy is converted into thermal energy and the converted thermal energy is removed through a circulating coolant, especially when the high-speed braking gear is used for a long time, it may increase the coolant temperature of the hydraulic retarder, thereby affecting the maximum available braking force of the hydraulic retarder. For example, in the case of an eddy current retarder, the exciting current flowing in the stator coil generates a stator magnetic field, the rotor rotates together with the drive shaft, cuts the magnetic field of the stator magnetic field, thereby generating an eddy current-like induced current in the rotor. The stator magnetic field applies an electromagnetic force that hinders the rotor rotation to the rotor, thereby generating a braking force that can be adjusted by the exciting current flowing in the stator coil. Here, the larger the exciting current, the stronger the stator magnetic field, and the larger the maximum available braking force of the eddy current retarder.
[0019] For example, in the service braking mode, the driving speed of the vehicle can be reduced by a hydraulic braking mechanism constructed based on Pascal's law, and its braking strength is affected by factors such as the ground adhesion coefficient, wheel load, and wheel radius. On the premise that the safety requirements of the entire vehicle brake are met, the maximum available braking force in the service braking mode is generally sufficient to meet the driver's braking requirements in non-emergency situations. Therefore, the maximum available braking force in the service braking mode can be considered not to be restricted in the sense of the present invention.
[0020] In step S3, in a state where a maximum of two braking modes are used, the required braking force for each braking mode is determined based on at least the required total braking intensity and the priority of the braking mode, respectively. In the prior art, a plurality of braking modes such as a motor braking mode, a retarder braking mode, a regenerative braking mode, and a service braking mode are generally used simultaneously in the braking system of a hybrid vehicle, which may cause severe brake judder during the braking process. Therefore, in these hybrid vehicles, a continuous brake coordinator needs to cooperate with the vehicle body skid prevention system to ensure the stability of the vehicle body, which greatly increases the software and hardware costs of vehicle system design. In an embodiment of the present invention, in the braking process of an electric vehicle, only a maximum of two braking modes are used, that is, only one braking mode or two braking modes are used. Here, the required braking force of the braking mode used does not exceed its available maximum braking force. Therefore, the control strategy used to adjust these braking modes can be simplified, and the hardware and software costs of the continuous brake coordinator used to adjust these braking modes can be effectively reduced.
[0021] Step S3 will be described in detail with reference to the workflow diagram of a method for controlling a braking system of an electric vehicle according to another exemplary embodiment of the present invention as shown in FIG. 3. As shown in FIG. 3, step S3 may be configured to include steps S31 to S35. In step S31, it is determined whether the braking strength Z1 in the first braking mode is greater than zero. If the braking strength Z1 in the first braking mode is not greater than zero, in step S32, when the first braking mode is not being used, the required braking force for various braking modes may be determined based on at least the required total braking strength Zt and the priority of the braking modes, that is, the required braking force F2 in the second braking mode. Optionally, the required braking force F3 in the third braking mode may also be determined here.
[0022] Regarding step S32, it will be further described below in relation to the workflow chart of a method for controlling a braking system of an electric vehicle according to another exemplary embodiment of the present invention shown in FIG. 4. Only the differences from the embodiment shown in FIG. 3 will be described below, and for the sake of brevity, the same steps will not be repeatedly described.
[0023] As shown in FIG. 4, step S32 further includes steps S321 to S323. In step S321, it is determined whether the required total braking strength Zt is greater than the braking strength Z2 of the second braking mode. If the required total braking strength Zt is greater than the braking strength Z2 of the second braking mode, in step S322, the required braking force F2 is determined as the maximum available braking force F2max of the second braking mode, and the required braking force F3 is determined as the difference between the required braking force Ft calculated based on the required total braking strength Zt and the required braking force F3 of the third braking mode. If the required total braking strength Zt is not greater than the braking strength Z2 of the second braking mode, in step S323, the required braking force F2 of the second braking mode is determined as the required total braking force Ft calculated based on the required total braking strength Zt.
[0024] When the braking strength Z1 of the first braking mode is greater than zero, in step S33, it is determined whether the required total braking strength Zt is greater than the sum of the braking strength Z1 of the first braking mode and the braking strength Z2 of the second braking mode. When the required total braking strength Zt is greater than the sum of the braking strength Z1 of the first braking mode and the braking strength Z2 of the second braking mode, in step S34, the required braking force F1 of the first braking mode is determined as the maximum available braking force F1max of the first braking mode, and the required braking force F3 of the third braking mode is determined as the difference between the required total braking force Ft calculated based on the required braking force Zt and the required braking force F1 of the first braking mode. When the required total braking strength Zt is not greater than the sum of the braking strength Z1 of the first braking mode and the braking strength Z2 of the second braking mode, in step S35, when the first braking mode is not used, the required braking force of each braking mode may be determined based at least on the required total braking strength Zt and the priority of the braking mode, that is, the required braking force F1 of the second braking mode and the required braking force F3 of the third braking mode may be determined here.
[0025] Step S35 will be further described in connection with the work flow chart of the method for controlling the braking system of an electric vehicle according to another exemplary embodiment of the present invention shown in FIG. 5. Only the differences from the embodiment shown in FIG. 3 are described below, and for the sake of brevity, the same steps will not be repeatedly described.
[0026] As shown in FIG. 5, step S35 further includes steps S351 to S353. In step S351, it is determined whether the required total braking strength Zt is greater than the braking strength Z1 of the first braking mode. If the required total braking strength Zt is greater than the braking strength Z1 of the first braking mode, then in step S352, the required braking force F1 of the first braking mode is determined as the maximum available braking force F1max of the first braking mode, and the required braking force F2 is determined as the difference between the required total braking force Ft calculated based on the required total braking strength Zt and the required braking force F1 of the first braking mode. If the required total braking strength Zt is not greater than the braking strength Z1 of the first braking mode, then in step S353, the required braking force F1 of the first braking mode is determined as the required total braking force Ft calculated based on the required total braking strength Zt.
[0027] According to an embodiment of the present invention, in the braking process of an electric vehicle, only a maximum of two braking modes are used, thereby effectively suppressing braking jitter in the braking process, improving the driving comfort of the vehicle, simplifying the control strategy used to adjust these braking modes, and effectively reducing the hardware and software costs of the continuous brake coordinator used to adjust these braking modes.
[0028] In an optional embodiment of the present invention, the retarder brake mode may be adopted as a first brake mode having a first priority, the motor brake mode may be adopted as a second brake mode having a second priority, and the service brake mode may be adopted as a third brake mode having a third priority. By using the motor brake mode and the service brake mode in cooperation with the retarder brake mode while prioritizing the retarder brake mode, a smoother braking effect can be obtained, the braking strength and the braking frequency of the service brake can be reduced as much as possible, thereby effectively extending the service life of the service brake and reducing the influence of thermal degradation of the service brake caused by high-strength and high-frequency service brakes.
[0029] In another optional embodiment of the present invention, the motor brake mode may be adopted as a first brake mode having a first priority, the retarder brake mode may be adopted as a second brake mode having a second priority, and the service brake mode may be adopted as a third brake mode having a third priority. By using the retarder brake mode and the service brake mode in cooperation with the motor brake mode while prioritizing the motor brake mode, as much of the excess energy during the braking process of the electric vehicle can be recovered as possible, the braking strength and the braking frequency of the service brake can be minimized, and the cruising range of the electric vehicle can be improved, thereby effectively extending the service life of the service brake and reducing the influence of thermal degradation of the service brake caused by high-strength and high-frequency service brakes.
[0030] In addition, it should be noted that the series of numbers of the steps described in this disclosure do not necessarily represent a continuous order and are merely reference numbers. Depending on the situation, the above order may be changed as long as the technical objectives of this disclosure are achieved.
[0031] Although specific embodiments have been described above, these embodiments are not intended to limit the scope of the present disclosure, even when described with respect to the specific configurations of the individual embodiments. The examples of the configurations provided in the present disclosure are intended to be illustrative and not limiting, unless otherwise described separately. In a specific implementation, a plurality of configurations may be combined with each other according to actual requirements and when technically feasible. Various substitutions, changes, and modifications will be conceivable without departing from the spirit and scope of the present disclosure.
Claims
1. A method for controlling a braking system (1) of an electric vehicle, comprising the steps of: Step S1: determining a total brake strength required for the brake system (1) based on at least a brake demand of the brake system (1) and a vehicle driving speed of the electric vehicle; Step S2: determining a brake strength for each brake mode of the brake system (1) based on at least vehicle state information of the electric vehicle, the brake system (1) having at least three brake modes, the brake modes having a preset priority; Step S3: determining the required brake force for each brake mode based on the total required brake strength and the priority of the brake modes, at least if at most two brake modes are used; The method includes:
2. The method of claim 1 , wherein the braking modes of the braking system (1) include a retarder braking mode, a service braking mode, and a motor braking mode.
3. 3. The method of claim 2, wherein the retarder braking mode is used as a first braking mode having a first priority, the motor braking mode is used as a second braking mode having a second priority, and the service braking mode is used as a third braking mode having a third priority.
4. 3. The method of claim 2, wherein the motor braking mode is used as a first braking mode having a first priority, the retarder braking mode is used as a second braking mode having a second priority, and the service braking mode is used as a third braking mode having a third priority.
5. The method of claim 2 , wherein the requested braking force for each braking mode is determined such that the requested braking force of each braking mode does not exceed a maximum available braking force of each braking mode.
6. 6. The method according to claim 2, wherein the brake strength of the motor braking mode of the brake system (1) is determined based on at least a wheel speed, a battery state of charge and / or a motor temperature of the electric vehicle.
7. 6. The method according to claim 2, wherein the braking strength of the retarder braking mode of the brake system (1) is determined based on at least a retarder gear of the electric vehicle.
8. Step S3 is Step S31: determining whether the brake strength of the first brake mode is greater than zero; Step S32: if the brake strength of the first brake mode is equal to or less than zero, determining the required brake force of each brake mode when the first brake mode is not in use based on at least the required total brake strength and the priority of the brake modes, respectively; Step S33: if the brake strength of the first brake mode is greater than zero, determining whether the requested total brake strength is greater than the sum of the brake strength of the first brake mode and the brake strength of the second brake mode; Step S34: if the requested total brake strength is greater than the sum of the brake strength of the first brake mode and the brake strength of the second brake mode, determine the requested brake force of the first brake mode as the maximum available brake force of the first brake mode, and determine the requested brake force of the third brake mode as a difference between the requested total brake force calculated based on the requested total brake strength and the requested brake force of the first brake mode; Step S35: if the total requested brake strength is not greater than the sum of the brake strength of the first brake mode and the brake strength of the second brake mode, when the first brake mode is not being used, determining the requested brake force for each brake mode based on at least the total requested brake strength and the priority of the brake modes, respectively; The method of claim 3 , further comprising:
9. Step S32 is Step S321: determining whether the requested total braking strength is greater than the braking strength of the second braking mode; Step S322: if the requested total brake strength is greater than the brake strength of the second brake mode, determine the requested brake force of the second brake mode as the maximum available brake force of the second brake mode, and determine the requested brake force of the third brake mode as a difference between the requested total brake force calculated based on the requested total brake strength and the requested brake force of the third brake mode; Step S323: if the requested total brake strength is not greater than the brake strength of the second brake mode, determining the requested brake force of the second brake mode as a requested total brake force calculated based on the requested total brake strength; The method of claim 8 further comprising:
10. Step S35 is Step S351: determining whether the requested total braking strength is greater than the braking strength of the first braking mode; Step S352: if the requested total brake strength is greater than the brake strength of the first brake mode, determine the requested brake force of the first brake mode as the maximum available brake force of the first brake mode, and determine the requested brake force of the second brake mode as a difference between the requested total brake force calculated based on the requested total brake strength and the requested brake force of the first brake mode; Step S353: if the requested total brake strength is not greater than the brake strength of the first brake mode, determining the requested brake force of the first brake mode as a requested total brake force calculated based on the requested total brake strength; The method of claim 8 , comprising:
11. A brake system (1) for an electric vehicle, said system (1) comprising: A vehicle state acquisition module (11) configured to acquire vehicle state information for an electric vehicle, the vehicle state information including a vehicle driving speed; a brake request acquisition module (12) configured to acquire a brake request of the brake system (1); at least three brake modules (13) for performing braking in different braking modes, said braking modes having a preset priority; A control module (14) configured to implement the method according to any one of claims 1 to 10; A brake system (1).
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 performing the steps of the method of any one of claims 1 to 10.