Hydrogen fuel cell vehicle braking energy recovery method and system

Abstract

The application discloses a hydrogen fuel cell vehicle braking energy recovery method and system, and the method comprises the following steps: determining the whole vehicle braking intensity based on the opening degree of the vehicle brake pedal; starting the motor regenerative braking mode when the vehicle speed, the battery charge state value and the whole vehicle braking intensity satisfy the preset judgment condition at the same time; introducing the discomfort index, inputting the vehicle speed, the whole vehicle braking intensity and the discomfort index into the fuzzy controller for processing to obtain the regenerative braking force weight coefficient; when the whole vehicle braking intensity falls in the first preset interval, the vehicle adopts the small intensity braking mode, and the maximum motor braking force is converted into the electric energy and stored in the battery; when the whole vehicle braking intensity falls in the second preset interval, the vehicle adopts the medium intensity braking mode, and the motor braking force constrained by the regenerative braking force weight coefficient is converted into the electric energy and stored in the battery. The application can ensure the braking energy recovery efficiency when the vehicle brakes, and improve the riding comfort of passengers.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicle technology, specifically to a method and system for recovering braking energy in hydrogen fuel cell vehicles. Background Technology

[0002] Currently, there are two types of regenerative braking systems for new energy vehicles: parallel regenerative braking systems, which directly add the regenerative braking torque generated by the motor to the friction torque under the existing hydraulic braking conditions, essentially performing simple torque superposition; and series regenerative braking systems, which can rationally distribute regenerative braking and friction braking according to the current vehicle braking conditions. However, both systems have their advantages and disadvantages: parallel regenerative braking systems are simple in structure, low in cost, and easy to implement, but their energy recovery efficiency is low; series regenerative braking systems require redesigning the vehicle's original braking system, making implementation difficult and costly. More importantly, many scholars currently focus on improving the efficiency of regenerative braking in existing new energy vehicles, often neglecting to improve passenger comfort during braking. Summary of the Invention

[0003] This invention provides a method and system for recovering braking energy in hydrogen fuel cell vehicles, in order to solve one or more technical problems existing in the prior art, and at least provide a beneficial option or create conditions.

[0004] This invention provides a method for recovering braking energy in a hydrogen fuel cell vehicle, the method comprising:

[0005] The braking intensity of the entire vehicle is determined based on the opening of the vehicle's brake pedal;

[0006] When the vehicle speed, battery charge state value and the vehicle braking intensity simultaneously meet the preset judgment conditions, the motor regenerative braking mode is activated.

[0007] An discomfort index is introduced as an important parameter for evaluating passenger comfort. The vehicle speed, the vehicle braking intensity, and the discomfort index are input into a fuzzy controller for processing to obtain the regenerative braking force weight coefficient.

[0008] When the braking intensity of the vehicle falls within the first preset range, the vehicle adopts a low-intensity braking mode and then converts the maximum braking force of the motor into electrical energy stored in the battery.

[0009] When the overall vehicle braking intensity falls within the second preset range, the vehicle adopts a medium-intensity braking mode, and then converts the motor power constrained by the regenerative braking force weighting coefficient into electrical energy stored in the battery.

[0010] Further, the process of determining the discomfort index is as follows:

[0011] Create a mapping relationship table between braking conditions and passenger riding comfort;

[0012] Obtain the vehicle deceleration and deceleration change rate, and then obtain the corresponding discomfort index by looking up the mapping relationship table.

[0013] Further, a regeneration braking force weight coefficient rule base including several independent variables and a single dependent variable is pre-stored inside the fuzzy controller. The several independent variables include vehicle speed intervals, vehicle braking intensity intervals, and discomfort index intervals, and the single dependent variable is the regeneration braking force weight coefficient interval.

[0014] Further, inputting the vehicle speed, vehicle braking intensity, and discomfort index into the fuzzy controller for processing to obtain the regeneration braking force weight coefficient includes:

[0015] According to the vehicle speed interval to which the vehicle speed belongs, the vehicle braking intensity interval to which the vehicle braking intensity belongs, and the discomfort index interval to which the discomfort index belongs, match and screen out the corresponding regeneration braking force weight coefficient interval from the regeneration braking force weight coefficient rule base;

[0016] Use the Mamdani fuzzy inference method自带 by the fuzzy controller to determine a suitable regeneration braking force weight coefficient from this regeneration braking force weight coefficient interval.

[0017] Further, when the vehicle braking intensity falls within the first preset interval, the condition is Z ≤ Z1, and when the vehicle braking intensity falls within the second preset interval, the condition is Z1 < Z ≤ Z2, where Z is the vehicle braking intensity, Z1 is the preset minimum braking intensity, and Z2 is the preset maximum braking intensity.

[0018] Further, the small-intensity braking mode is manifested as:

[0019] When the maximum braking force of the motor is greater than or equal to the braking force required by the front axle, all the braking force required by the front axle is provided solely by the electric motor braking, and the braking force provided by the electric motor braking is the maximum braking force of the motor;

[0020] When the maximum braking force of the motor is less than the braking force required by the front axle, the braking force required by the front axle is provided jointly by the electric motor braking and the front axle hydraulic braking, and the braking force provided by the electric motor braking is the maximum braking force of the motor.

[0021] Furthermore, the medium-intensity braking method is characterized by the following: the braking force required by the front axle is provided by a combination of electric motor braking and front axle hydraulic braking, while the braking force required by the rear axle is provided solely by rear axle hydraulic braking. The braking force provided by the electric motor braking is the product of the regenerative braking force weighting coefficient and the braking force required by the front axle.

[0022] Furthermore, determining the overall vehicle braking intensity based on the vehicle's brake pedal opening includes:

[0023] Based on the brake pedal opening, the corresponding master cylinder braking pressure is obtained by checking the pre-defined correlation curve, and then the overall vehicle braking intensity is calculated.

[0024] Furthermore, the preset judgment condition is:

[0025]

[0026] Where SOC is the battery state of charge, v is the vehicle speed, Z is the vehicle braking intensity, and Z2 is the preset maximum braking intensity.

[0027] In addition, embodiments of the present invention also provide a braking energy recovery system for a hydrogen fuel cell vehicle, the system comprising:

[0028] At least one processor;

[0029] At least one memory for storing at least one program;

[0030] When the at least one program is executed by the at least one processor, the at least one processor implements the regenerative braking method for hydrogen fuel cell vehicles as described above.

[0031] This invention offers at least the following advantages: When the regenerative braking mode is activated, by developing corresponding braking energy recovery strategies for different braking levels, the braking energy recovery efficiency can be maximized, thereby reducing overall vehicle energy consumption and extending driving range. Furthermore, by introducing an discomfort index as a parameter in the braking energy recovery strategy, passenger comfort during vehicle braking can be improved. Attached Figure Description

[0032] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the technical solutions of the present invention, and do not constitute a limitation on the technical solutions of the present invention.

[0033] Figure 1 This is a schematic flowchart of a method for recovering braking energy of a hydrogen fuel cell vehicle according to an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the correlation curve between the brake pedal opening and the required braking pressure of the master cylinder in an embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of the correlation curve between the discomfort index and passenger ride comfort in an embodiment of the present invention;

[0036] Figure 4 This is a surface diagram showing the mapping relationship between vehicle speed, overall vehicle braking intensity, and regenerative braking force weighting coefficient in an embodiment of the present invention.

[0037] Figure 5 This is a surface diagram showing the mapping relationship between vehicle speed, discomfort index, and regenerative braking force weighting coefficient in this embodiment of the invention.

[0038] Figure 6 This is a surface diagram showing the mapping relationship between the vehicle braking intensity, the discomfort index, and the regenerative braking force weighting coefficient in this embodiment of the invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] It should be noted that although functional modules are divided in the system diagram and the logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the system or the order in the flowchart. The terms "first," "second," etc., in the specification, claims, and the aforementioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0041] Please refer to Figure 1 , Figure 1 This is a schematic flowchart of a method for recovering braking energy in a hydrogen fuel cell vehicle according to an embodiment of the present invention. The method includes the following steps:

[0042] S101. Determine the overall vehicle braking intensity based on the vehicle's brake pedal opening.

[0043] In this embodiment of the invention, a technician pre-plans as follows: Figure 2 The correlation curve shown is used to obtain the master cylinder braking pressure required for the vehicle's brake pedal opening, and then the overall vehicle braking intensity is calculated as follows:

[0044]

[0045] Among them, Z is the vehicle braking intensity, T b is the braking torque required by the vehicle, G is the vehicle mass, r b is the effective radius of the brake, 2 indicates that there are two friction plates on the front axle or rear axle of the brake, p b is the braking pressure required by the master cylinder, A b is the effective area of the brake, η b is the brake efficiency, u b is the brake friction coefficient, c b is the braking coefficient, and only p b among the above parameters changes with the change of the braking condition.

[0046] S102. When the vehicle speed, the battery charge state value, and the vehicle braking intensity simultaneously meet the preset judgment conditions, start the motor regenerative braking mode.

[0047] In the embodiment of the present invention, the preset judgment conditions are:

[0048]

[0049] Among them, SOC is the battery charge state value, v is the vehicle speed, and Z2 is the preset maximum braking intensity.

[0050] It should be noted that when the vehicle speed, the battery charge state value, or the vehicle braking intensity does not meet the preset judgment conditions, the motor regenerative braking mode is turned off and the braking energy cannot be recovered; in addition, when the vehicle braking intensity does not meet the preset judgment conditions (i.e., Z>Z2), it is determined that the vehicle is in an emergency braking state, and all the braking force required by the front axle is provided solely by the front axle hydraulic braking, and all the braking force required by the rear axle is provided solely by the rear axle hydraulic braking.

[0051] S103. Judge whether the vehicle braking intensity falls within the first preset interval or the second preset interval.

[0052] Specifically, when it is judged that the vehicle braking intensity falls within the first preset interval (i.e., satisfies Z≤Z1, where Z1 is the preset minimum braking intensity), continue to execute step S104; or, when it is judged that the vehicle braking intensity falls within the second preset interval (i.e., satisfies Z1<Z≤Z2), jump to execute step S105.

[0053] S104. The vehicle adopts a small-intensity braking method, and then converts the maximum braking force of the motor into electric energy and stores it in the battery.

[0054] In this embodiment of the invention, the vehicle employs a low-intensity braking method as follows: When the maximum braking force of the motor is greater than or equal to the braking force required by the front axle, the braking force required by the front axle is entirely provided by the motor brake alone, wherein the braking force provided by the motor brake is the maximum braking force of the motor; or, when the maximum braking force of the motor is less than the braking force required by the front axle, the braking force required by the front axle is jointly provided by the motor brake and the front axle hydraulic brake, wherein the braking force provided by the motor brake is the maximum braking force of the motor, and the braking force provided by the front axle hydraulic brake is: F uf =F uf0 -F max F uf0 For the braking force required by the front axle, F max This is the maximum braking force of the motor.

[0055] In this embodiment of the invention, during low-intensity braking, the braking torque generated by the motor reduces the vehicle speed. Simultaneously, the inertia generated by braking is fed back to the motor via the transmission system, and this inertia is converted into electrical energy to charge the battery. The battery charging power achieved at this time is:

[0056]

[0057] in:

[0058]

[0059] In the formula, P1 is the battery charging power achieved by the vehicle during low-intensity braking, r is the wheel radius, n is the motor speed, and T is the electric motor speed. max n is the peak torque of the motor. e P is the rated speed of the motor. max This represents the peak power of the motor.

[0060] S105. Introduce the discomfort index as an important parameter for evaluating passenger ride comfort. Input the vehicle speed, the vehicle braking intensity and the discomfort index into the fuzzy controller for processing to obtain the regenerative braking force weight coefficient.

[0061] In this embodiment of the invention, the process of determining the discomfort index is as follows: First, a mapping relationship table between braking conditions and passenger ride comfort is created, as shown in Table 1, wherein the braking condition includes vehicle deceleration and vehicle deceleration rate of change, and the passenger ride comfort refers to the discomfort index; second, the vehicle deceleration and deceleration rate of change are obtained, and the corresponding discomfort index is obtained by looking up the mapping relationship table.

[0062] Table 1. Mapping Relationship between Braking Conditions and Passenger Ride Comfort

[0063]

[0064] The discomfort index D ranges from 1 to 5, and the relationship between the discomfort index and passenger comfort is as follows: Figure 3 As shown, it can be seen that the discomfort index and passenger comfort are inversely proportional; that is, the higher the discomfort index, the worse the passenger comfort.

[0065] In this embodiment of the invention, the process for determining the regenerative braking force weighting coefficient includes the following:

[0066] (1) Create a fuzzy controller and store in advance a regenerative braking force weight coefficient rule base including several independent variables and a single dependent variable, wherein the several independent variables include vehicle speed range, vehicle braking intensity range and discomfort index range, and the single dependent variable is the regenerative braking force weight coefficient range.

[0067] In this step (1), firstly, the range of vehicle speed V is determined to be 0≤V≤120, the range of vehicle braking intensity Z is 0≤Z≤1, the range of discomfort index D is 1≤D≤5, and the range of regenerative braking force weight coefficient k is 0≤k≤1; secondly, a mapping relationship surface diagram between any two parameters among vehicle speed, vehicle braking intensity, and discomfort index and the regenerative braking force weight coefficient is established through multiple experiments, such as... Figures 4 to 6 As shown in Table 2, the vehicle speed range is further subdivided into five speed intervals: {VS (very small), S (small), M (medium), L (large), VL (very large)}. Similarly, the overall vehicle braking intensity range is subdivided into three braking intensity intervals: {S (small), M (medium), L (large)}. The discomfort index range is subdivided into three discomfort index intervals: {S (small), M (medium), L (large)}. The regenerative braking force weight coefficient range is further subdivided into five regenerative braking force weight coefficient intervals: {VS (very small), S (small), M (medium), L (large), VL (very large)}. Each parameter's range is divided in ascending order. Finally, based on the established mapping relationship surfaces, the multiple intervals defined by the aforementioned parameter ranges are correlated and matched to form a regenerative braking force weight coefficient rule table, as shown in Table 2.

[0068] Table 2 Regenerative Braking Force Weighting Coefficient Rules

[0069]

[0070] (2) Based on the vehicle speed range to which the vehicle speed belongs, the vehicle braking intensity range to which the vehicle braking intensity belongs, and the discomfort index range to which the discomfort index belongs, the corresponding regenerative braking force weight coefficient range is matched and filtered from the regenerative braking force weight coefficient rule library.

[0071] For example, step (2) is illustrated as follows: The vehicle speed, the vehicle braking intensity, and the discomfort index are input into the fuzzy controller. When it is determined that the vehicle speed falls within the vehicle speed range M, the vehicle braking intensity falls within the vehicle braking intensity range S, and the discomfort index falls within the discomfort index range M, the final regenerative braking force weight coefficient can be determined to fall within the regenerative braking force weight coefficient range L by looking up Table 2.

[0072] (3) Use the Mamdani fuzzy inference method built into the fuzzy controller to determine a suitable regenerative braking force weight coefficient from the range of regenerative braking force weight coefficients.

[0073] S106. The vehicle adopts a medium-intensity braking method, and then converts the motor power constrained by the regenerative braking force weight coefficient into electrical energy and stores it in the battery.

[0074] In this embodiment of the invention, the vehicle employs a medium-intensity braking method as follows: the braking force required by the front axle is provided jointly by the electric motor brake and the front axle hydraulic brake, while the braking force required by the rear axle is provided solely by the rear axle hydraulic brake. The braking force F provided by the electric motor brake is the sum of the regenerative braking force weighting coefficient k and the braking force F required by the front axle. uf0 The product of (i.e., F = kF) uf0 The braking force provided by the front axle hydraulic brake is: F uf =F uf0 -F, and the braking force provided by the rear axle hydraulic brake is: F ur =F ur0 F ur0 This is the braking force required for the rear axle.

[0075] Similarly, the battery charging power achieved by the vehicle during moderate-intensity braking is: P2 = Frn / 9550.

[0076] In this embodiment of the invention, by formulating corresponding braking energy recovery strategies for different braking levels of the vehicle when the regenerative braking mode of the electric motor is activated, the braking energy recovery efficiency of the vehicle can be maximized, thereby reducing the overall energy consumption of the vehicle and extending its driving range. By introducing an discomfort index as a parameter to consider in the formulation of the braking energy recovery strategy, the passenger comfort during vehicle braking will be improved.

[0077] In addition, embodiments of the present invention also provide a braking energy recovery system for a hydrogen fuel cell vehicle, the system comprising:

[0078] At least one processor;

[0079] At least one memory for storing at least one program;

[0080] When the at least one program is executed by the at least one processor, the at least one processor implements the hydrogen fuel cell vehicle braking energy recovery method described in any of the above embodiments.

[0081] The content of the above method embodiments is applicable to this system embodiment. The functions implemented in this system embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are the same as those in the above method embodiments.

[0082] The processor can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of the hydrogen fuel cell vehicle's regenerative braking system, connecting various parts of the system's operational components via various interfaces and wiring.

[0083] The memory can be used to store the computer programs and / or modules. The processor implements various functions of the hydrogen fuel cell vehicle braking energy recovery system by running or executing the computer programs and / or modules stored in the memory and calling the data stored in the memory. The memory may mainly include a program storage area and a data storage area, wherein: the program storage area is used to store the operating system, at least one application program required for a function (such as sound playback function, image playback function, etc.); the data storage area is used to store data created based on the use of the mobile phone (such as audio data, phonebook, etc.). In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as hard disk, memory, plug-in hard disk, smart-media-card (SMC), secure-digital (SD) card, flash card, at least one disk storage device, flash memory device, or other volatile solid-state storage device.

[0084] Although the description of this application has been quite detailed and particularly focused on several of the described embodiments, it is not intended to limit itself to any of these details or embodiments or any particular embodiment. Rather, it should be considered as effectively covering the intended scope of this application by referring to the appended claims and taking into account the prior art, which provides for a broad possible interpretation of these claims. Furthermore, the foregoing description of this application with respect to embodiments foreseeable by the inventors is intended to provide a useful description, and non-substantial modifications to this application that have not yet been foreseen may still represent equivalent modifications.

Claims

1. A hydrogen fuel cell vehicle brake energy recovery method, characterized by, The method comprises: determining the vehicle braking intensity based on the opening degree of the vehicle brake pedal; starting the motor regenerative braking mode when the vehicle speed, the battery charge state value and the vehicle braking intensity simultaneously satisfy the preset judgment condition; introducing the discomfort index as an important parameter for evaluating the passenger ride comfort, inputting the vehicle speed, the vehicle braking intensity and the discomfort index into the fuzzy controller for processing to obtain a regenerative braking force weight coefficient; when the vehicle braking intensity falls within a first preset interval, the vehicle adopts a small-intensity braking mode, and the maximum motor braking force is converted into electrical energy and stored in the battery; when the vehicle braking intensity falls within a second preset interval, the vehicle adopts a medium-intensity braking mode, and the motor braking force constrained by the regenerative braking force weight coefficient is converted into electrical energy and stored in the battery; wherein the small-intensity braking mode is characterized in that when the maximum motor braking force is greater than or equal to the front axle required braking force, the front axle required braking force is entirely provided by the motor braking alone; when the maximum motor braking force is less than the front axle required braking force, the front axle required braking force is jointly provided by the motor braking and the front axle hydraulic braking; the braking force provided by the motor braking is the maximum motor braking force; wherein the medium-intensity braking mode is characterized in that the front axle required braking force is jointly provided by the motor braking and the front axle hydraulic braking, and the rear axle required braking force is entirely provided by the rear axle hydraulic braking alone; the braking force provided by the motor braking is the product of the regenerative braking force weight coefficient and the front axle required braking force; wherein the determination process of the discomfort index is: creating a mapping relationship table between the braking condition and the passenger ride comfort; obtaining the vehicle deceleration and the deceleration change rate, and then obtaining the corresponding discomfort index by looking up the mapping relationship table; wherein a regenerative braking force weight coefficient rule base including a plurality of independent variables and a single dependent variable has been pre-stored in the fuzzy controller, wherein the plurality of independent variables include the vehicle speed interval, the vehicle braking intensity interval and the discomfort index interval, and the single dependent variable is the regenerative braking force weight coefficient interval; wherein the inputting of the vehicle speed, the vehicle braking intensity and the discomfort index into the fuzzy controller for processing to obtain the regenerative braking force weight coefficient comprises: according to the vehicle speed interval to which the vehicle speed belongs, the vehicle braking intensity interval to which the vehicle braking intensity belongs and the discomfort index interval to which the discomfort index belongs, matching and screening out the corresponding regenerative braking force weight coefficient interval from the regenerative braking force weight coefficient rule base; determining a suitable regenerative braking force weight coefficient from the regenerative braking force weight coefficient interval by using the Mamdani fuzzy reasoning method provided by the fuzzy controller.

2. The hydrogen fuel cell vehicle brake energy recovery method of claim 1, wherein, The condition is satisfied when the vehicle braking intensity falls within the first preset interval, i.e. Z≤Z1, and the condition is satisfied when the vehicle braking intensity falls within the second preset interval, i.e. Z1<Z≤Z2, wherein Z is the vehicle braking intensity, Z1 is the preset minimum braking intensity, and Z2 is the preset maximum braking intensity.

3. The hydrogen fuel cell vehicle brake energy recovery method of claim 1, wherein, The preset judgment condition is: Wherein, SOC is the battery charge state value, v is the vehicle speed, Z is the whole vehicle braking intensity, and Z2 is the preset maximum braking intensity.

4. A hydrogen fuel cell vehicle brake energy recovery system characterized by comprising: The system comprises: at least one processor; at least one memory for storing at least one program; When the at least one program is executed by the at least one processor, the at least one processor implements the hydrogen fuel cell vehicle braking energy recovery method as claimed in any one of claims 1-3.

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