Electric vehicle braking control method and vehicle

Abstract

The present invention belongs to the field of automobile technology and discloses an electric vehicle braking control method and a vehicle. The electric vehicle braking control method includes: monitoring the vehicle operating condition, judging whether the vehicle meets the energy recovery condition according to a set step length cycle, and if the vehicle meets the energy recovery condition, performing braking energy recovery; braking energy recovery includes: judging whether the current vehicle speed is greater than or equal to the set vehicle speed, and if the current vehicle speed is greater than or equal to the set vehicle speed, determining the current standard braking torque and the current vehicle target acceleration according to the current vehicle speed and the current brake pedal opening, and determining the current first braking torque correction coefficient according to the difference between the current vehicle actual acceleration and the current vehicle target acceleration; determining the current target braking torque according to the current first braking torque correction coefficient and the current standard braking torque; and controlling the motor torque to adjust to the current target braking torque.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicles, and in particular to a braking control method for an electric vehicle and a vehicle. Background Art

[0002] When the driver needs to decelerate during electric vehicle operation, the electric vehicle uses a combination of electric and mechanical brakes. Electric braking involves the motor outputting reverse torque (braking torque) for braking, while mechanical braking utilizes traditional brakes. Utilizing electric braking as much as possible while ensuring safety is an effective measure for improving vehicle economics. Existing electric vehicle braking control methods, at high speeds, the braking torque is solely dependent on the current vehicle speed and brake pedal opening. The greater the current speed and the wider the brake pedal opening, the greater the braking torque. However, under conditions such as full load and downhill driving, the braking torque is insufficient, resulting in limited brake energy recovery.

[0003] Therefore, there is an urgent need for an electric vehicle braking control method and a vehicle to solve the above problems. Summary of the Invention

[0004] The object of the present invention is to provide an electric vehicle braking control method and vehicle to solve the problem of insufficient braking torque under full load and downhill conditions, and to recover more energy.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] An electric vehicle braking control method, comprising:

[0007] Monitor the vehicle's operating conditions and determine whether the vehicle meets the energy recovery conditions in a cycle according to the set step length. If the vehicle meets the energy recovery conditions, brake energy recovery is performed;

[0008] Braking energy recovery includes:

[0009] determining whether the current vehicle speed is greater than or equal to a set vehicle speed; if so, determining a current standard braking torque and a current vehicle target acceleration based on the current vehicle speed and the current brake pedal opening, and determining a current first braking torque correction coefficient based on a difference between the current actual vehicle acceleration and the current vehicle target acceleration;

[0010] determining a current target braking torque according to the current first braking torque correction coefficient and the current standard braking torque;

[0011] Control the motor torque to adjust toward the current target braking torque.

[0012] Preferably, the current target braking torque is equal to the product of the first braking torque correction coefficient and the current standard braking torque.

[0013] Preferably, the braking energy recovery further includes: filtering the current first braking torque correction coefficient to obtain a second braking torque correction coefficient, and the current target braking torque is equal to the product of the second braking torque correction coefficient and the current standard braking torque.

[0014] Preferably, determining the current standard braking torque and the current vehicle target acceleration according to the current vehicle speed and the current brake pedal opening includes:

[0015] Query the vehicle braking target acceleration MAP according to the current vehicle speed and the current brake pedal opening to determine the current vehicle target acceleration;

[0016] The current standard braking torque is determined by querying the braking torque MAP based on the current vehicle speed and the current brake pedal opening.

[0017] Preferably, controlling the motor torque to adjust toward the current target braking torque includes:

[0018] Determine the current motor braking torque setting change rate according to the current brake pedal opening;

[0019] The motor is controlled to adjust toward the current target braking torque according to the current motor braking torque setting change rate.

[0020] Preferably, the braking energy recovery further comprises:

[0021] If the current vehicle speed is less than the set speed, determine whether the brake pedal opening is greater than or equal to the set opening;

[0022] If the brake pedal opening is greater than or equal to the set opening, the motor is controlled to the speed mode, and the target speed is zero, and the motor speed is controlled to adjust toward the target speed.

[0023] Preferably, controlling the motor speed to adjust toward the target speed includes:

[0024] Determine the current motor braking torque setting change rate according to the current brake pedal opening;

[0025] The motor torque is controlled to adjust toward the current target braking torque according to the current motor braking torque setting change rate.

[0026] Preferably, the braking energy recovery further includes: if the current brake pedal opening is less than the set opening, the motor is controlled to be in torque mode, and the braking torque is zero.

[0027] Preferably, the energy recovery conditions include the current SOC of the vehicle battery being less than a set value, the current ABS not being triggered, and the current brake pedal opening being greater than zero or the current accelerator pedal opening and the current brake pedal opening being both zero.

[0028] A vehicle is provided, wherein the electric vehicle braking control method according to any one of the above items is used to perform vehicle braking control.

[0029] Beneficial effects of the present invention:

[0030] The electric vehicle braking control method and vehicle of the present invention determine whether the vehicle meets the energy recovery conditions by cyclically judging according to a set step length, and when the vehicle meets the energy recovery conditions and the vehicle speed is greater than or equal to the set vehicle speed, determine the current standard braking torque and the current vehicle target acceleration according to the current vehicle speed and the current brake pedal opening, and determine the current first braking torque correction coefficient according to the difference between the current vehicle actual acceleration and the current vehicle target acceleration. The difference between the current vehicle actual acceleration and the current vehicle target acceleration can reflect the difference between the current vehicle actual acceleration and the current vehicle target acceleration. For example, when the vehicle is fully loaded and downhill, after the driver steps on the brake pedal, the acceleration generated by the mechanical brake is small, and the difference between the current vehicle actual acceleration and the current vehicle target acceleration is large. The corresponding current first braking torque correction coefficient is obtained based on this large difference, and the current target braking torque is determined based on the current first braking torque correction coefficient and the current standard braking torque, and the motor torque is controlled to be adjusted toward the current target braking torque, thereby solving the problem of insufficient braking torque under working conditions such as full load and downhill, and recovering more energy. By performing cyclic judgment according to the set step length, the electric vehicle braking control method of the present invention can continuously change the current target braking torque according to changes in the vehicle's working conditions to meet the braking needs of various working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a flow chart of an electric vehicle braking control method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0033] In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0034] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0035] In the description of this embodiment, the terms "upper," "lower," "right," and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplified operation. They do not indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meanings.

[0036] like Figure 1 As shown, this embodiment provides an electric vehicle braking control method, comprising:

[0037] Monitor the vehicle's operating conditions and determine whether the vehicle meets the energy recovery conditions in a cycle according to the set step length. If the vehicle meets the energy recovery conditions, brake energy recovery is performed;

[0038] The braking energy recovery includes: determining whether the current vehicle speed is greater than or equal to a set vehicle speed; if the current vehicle speed is greater than or equal to the set vehicle speed, determining a current standard braking torque and a current vehicle target acceleration based on the current vehicle speed and the current brake pedal opening; and determining a current first braking torque correction coefficient based on a difference between the current vehicle actual acceleration and the current vehicle target acceleration;

[0039] Correcting the current standard braking torque according to the current first braking torque correction coefficient to determine the current target braking torque;

[0040] Control the motor torque to adjust toward the current target braking torque.

[0041] The electric vehicle braking control method, electric vehicle braking control method, and vehicle provided in this embodiment determine whether the vehicle meets energy recovery conditions in a cyclic manner according to a set step size. When the vehicle meets the energy recovery conditions and the vehicle speed is greater than or equal to the set speed, the method determines the current standard braking torque and the current vehicle target acceleration based on the current vehicle speed and the current brake pedal opening. The method also determines the current first braking torque correction coefficient based on the difference between the current actual vehicle acceleration and the current vehicle target acceleration. The difference between the current actual vehicle acceleration and the current vehicle target acceleration can reflect the difference between the current actual vehicle acceleration and the current vehicle target acceleration. For example, when the vehicle is fully loaded and traveling downhill, after the driver depresses the brake pedal, the acceleration generated by the mechanical brake (it should be noted that the acceleration generated by the mechanical brake is a negative value) is small, and the difference between the current actual vehicle acceleration and the current vehicle target acceleration is large. Based on this large difference, the corresponding current first braking torque correction coefficient is derived. The current target braking torque is then determined based on the current first braking torque correction coefficient and the current standard braking torque. The motor torque is then controlled to adjust toward the current target braking torque, thereby resolving the problem of insufficient braking torque under conditions such as full load and downhill driving, and recovering more energy. By performing cyclic judgment according to the set step length, the electric vehicle braking control method of the present invention can continuously change the current target braking torque according to changes in the vehicle's working conditions to meet the braking needs of various working conditions.

[0042] Specifically, in this embodiment, the energy recovery conditions include the current vehicle battery SOC (State of Charge) being less than a set value, the current ABS (Anti-lock Braking System) being untriggered, and the current brake pedal opening being greater than zero, or both the current accelerator pedal opening and the current brake pedal opening being zero. A current vehicle battery SOC being less than a set value indicates that the current vehicle battery is capable of storing recovered energy. A current brake pedal opening greater than zero indicates that the driver has stepped on the brake pedal. A current accelerator pedal opening and the current brake pedal opening being zero indicate that the vehicle is in a state of unpowered inertial driving. Energy recovery is not performed when the ABS is triggered in order to ensure driving safety.

[0043] Alternatively, as Figure 1 As shown, the current target braking torque is equal to the product of the first braking torque correction coefficient and the current standard braking torque.

[0044] Optionally, determining the current first braking torque correction coefficient based on the difference between the current actual vehicle acceleration and the current target vehicle acceleration includes: querying a first braking torque correction coefficient MAP based on the difference between the current actual vehicle acceleration and the current target vehicle acceleration to obtain the current first braking torque correction coefficient. The first braking torque correction coefficient MAP is pre-stored in the vehicle's electronic control unit. The first braking torque correction coefficient MAP includes a correspondence between the difference between the current actual vehicle acceleration and the target vehicle acceleration and the first braking torque correction coefficient. The first braking torque correction coefficient MAP is obtained through experiments. Specifically, in this embodiment, when the current vehicle actual acceleration is equal to the current vehicle target acceleration, the value of the first braking torque correction coefficient is 1, that is, the current target braking torque is equal to the current standard braking torque; when the current vehicle actual acceleration is greater than the current vehicle target acceleration, the value of the first braking torque correction coefficient is greater than 1, that is, the current target braking torque is greater than the current standard braking torque, so as to enhance the braking effect of the motor on the vehicle. For example, the current vehicle actual acceleration is -4 m / s, and the current vehicle target acceleration determined according to the current vehicle speed and the current brake pedal opening is -5 m / s. At this time, the current vehicle actual acceleration is greater than the current vehicle target acceleration, and the difference between the current vehicle actual acceleration and the current vehicle target acceleration is 1 m / s. At this time, the first braking torque correction coefficient is greater than 1. This situation may occur when fully loaded and going downhill. At this time, the motor torque is controlled to be adjusted toward the current target braking torque to further reduce the acceleration of the vehicle; when the current vehicle actual acceleration is less than the current vehicle target acceleration, the value of the first braking torque correction coefficient is less than 1. This situation may occur when lightly loaded and going uphill. The greater the absolute value of the difference between the current actual vehicle acceleration and the current target vehicle acceleration, the greater the absolute value of the difference between the first braking torque correction coefficient and 1, and the more obvious the correction effect.

[0045] Optionally, determining the current standard braking torque and the current vehicle target acceleration based on the current vehicle speed and the current brake pedal opening includes: querying a vehicle braking target acceleration MAP to determine the current vehicle target acceleration based on the current vehicle speed and the current brake pedal opening; and querying a braking torque MAP to determine the current standard braking torque based on the current vehicle speed and the current brake pedal opening. The vehicle braking target acceleration MAP includes a correspondence between vehicle speed and brake pedal opening and the vehicle target acceleration, and the braking torque MAP includes a correspondence between vehicle speed and brake pedal opening and the standard braking torque. Both the vehicle braking target acceleration MAP and the braking torque MAP are obtained experimentally and stored in the vehicle's electronic control unit. The vehicle target acceleration referred to herein is the ideal acceleration of the vehicle at a certain vehicle speed and a certain brake pedal opening. Accordingly, when the vehicle is traveling on flat ground at a certain speed under a certain load condition (e.g., unladen) and a certain load, and the driver depresses the brake pedal to the brake pedal opening, the motor braking torque required to achieve the vehicle target acceleration is the standard braking torque corresponding to the vehicle speed and the brake pedal opening.

[0046] Optionally, controlling the motor torque to adjust toward the current target braking torque includes: determining a current motor braking torque setting change rate based on the current brake pedal opening; and controlling the motor to adjust toward the current target braking torque according to the current motor braking torque setting change rate. Specifically, the current motor braking torque setting change rate is obtained by querying a motor braking torque setting change rate MAP based on the current brake pedal opening. The motor braking torque setting change rate MAP includes a correspondence between the motor braking torque setting change rate and the brake pedal opening. The motor braking torque setting change rate MAP is obtained through experiments and stored in the vehicle's electronic control unit. The motor braking torque setting change rate is positively correlated with the brake pedal opening. That is, when controlling the motor to adjust toward the current target braking torque, the greater the brake pedal opening, the greater the motor braking torque setting change rate, and the faster the motor braking torque changes. This configuration allows the driver's braking feel to adapt to the brake pedal opening, ensuring smooth braking and improving the driver's driving experience.

[0047] Alternatively, as Figure 1 As shown, brake energy recovery also includes: if the current vehicle speed is less than the set speed, determining whether the brake pedal opening is greater than or equal to the set opening; if the brake pedal opening is greater than or equal to the set opening, controlling the motor to speed mode, with the target speed set to zero, and adjusting the motor speed toward the target speed. If the current vehicle speed is less than the set value and the current brake pedal opening is greater than or equal to the set opening, indicating that although the vehicle speed is low, the driver has a desire to stop, the motor is controlled to speed mode, with the target speed set to zero, and adjusting the motor speed toward the target speed. In other words, the motor speed is reduced to zero. During this process, the motor assists the mechanical brake in braking the vehicle and recovers some energy.

[0048] Furthermore, controlling the motor speed to adjust toward the target speed includes: determining a current motor braking torque setting change rate based on the current vehicle speed and the current brake pedal opening; and controlling the motor torque to adjust toward the current target braking torque according to the current motor braking torque setting change rate. The current motor braking torque setting change rate is also obtained by querying the motor braking torque setting change rate MAP. Similarly, a greater brake pedal opening increases the motor braking torque setting change rate, and the motor braking torque changes faster.

[0049] Alternatively, as Figure 1 As shown, brake energy recovery also includes: if the current brake pedal opening is less than the set opening, the motor is controlled to torque mode, and the braking torque is zero. If the current vehicle speed is less than the set value and the current brake pedal opening is less than the set opening, it means that the current vehicle speed is low and the driver has no need to stop. In this case, the motor is controlled to torque mode, and the braking torque is zero, which means that the motor is in an idling state. Specifically, the set opening in this embodiment is the idle travel opening of the brake pedal. Within this idle travel opening range, the mechanical brake will not brake the vehicle. In other words, at this time, neither the mechanical brake nor the electric brake will brake the vehicle, and the vehicle will maintain an inertial driving state.

[0050] The electric vehicle braking control method provided in this embodiment does not adjust the mechanical brake of the electric vehicle, thereby achieving as much energy recovery as possible while ensuring driving safety, thereby improving the economy of the entire vehicle.

[0051] This embodiment also provides a vehicle, which uses the above-mentioned electric vehicle braking control method to perform vehicle braking control.

[0052] Example 2

[0053] like Figure 1As shown, this embodiment provides a braking control method for an electric vehicle. The specific braking control process is substantially the same as that of the first embodiment, except that the braking energy recovery in this embodiment further includes filtering the current first braking torque correction coefficient to obtain a second braking torque correction coefficient. The current target braking torque is equal to the product of the second braking torque correction coefficient and the current standard braking torque. The filtering process aims to prevent sudden changes in the motor braking torque from affecting the driver's driving experience, and to protect the target braking torque from accidental factors such as bumpy roads. Specifically, during vehicle braking, if the first braking torque correction coefficient obtained in a certain judgment differs significantly from the first braking torque correction coefficient obtained in the previous judgment, filtering is performed to bring the first braking torque correction coefficient of the current judgment closer to the first braking torque correction coefficient of the previous judgment to obtain a second braking torque correction coefficient, thereby preventing sudden changes in the target braking torque. For example, if the first braking torque correction coefficient in the previous judgment is 1 and the first braking torque correction coefficient obtained in the current judgment is 2, filtering can be used to correct the first braking torque correction coefficient of 2 obtained in the current judgment to a second braking torque correction coefficient of 1.2.

[0054] This embodiment also provides a vehicle, which uses the above-mentioned electric vehicle braking control method to perform vehicle braking control.

[0055] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. A person skilled in the art would be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. An electric vehicle braking control method, characterized in that: include: Monitor the vehicle's operating conditions and determine whether the vehicle meets the energy recovery conditions in a cycle according to the set step length. If the vehicle meets the energy recovery conditions, brake energy recovery is performed; Braking energy recovery includes: determining whether the current vehicle speed is greater than or equal to a set vehicle speed; if so, determining a current standard braking torque and a current vehicle target acceleration based on the current vehicle speed and the current brake pedal opening, and determining a current first braking torque correction coefficient based on a difference between the current actual vehicle acceleration and the current vehicle target acceleration; determining a current target braking torque according to a current first braking torque correction coefficient and a current standard braking torque; Control the motor torque to adjust to the current target braking torque; The current target braking torque is equal to the product of the first braking torque correction coefficient and the current standard braking torque; The braking energy recovery further includes: filtering the current first braking torque correction coefficient to obtain a second braking torque correction coefficient, wherein the current target braking torque is equal to the product of the second braking torque correction coefficient and the current standard braking torque; Controlling the motor torque to adjust to the current target braking torque includes: Determine the current motor braking torque setting change rate according to the current brake pedal opening; The motor is controlled to adjust toward the current target braking torque according to the current motor braking torque setting change rate.

2. The electric vehicle braking control method according to claim 1, characterized in that: Determining the current standard braking torque and the current vehicle target acceleration based on the current vehicle speed and the current brake pedal opening includes: Query the vehicle braking target acceleration MAP according to the current vehicle speed and the current brake pedal opening to determine the current vehicle target acceleration; The current standard braking torque is determined by querying the braking torque MAP based on the current vehicle speed and the current brake pedal opening.

3. The electric vehicle braking control method according to claim 1, characterized in that: Braking energy recovery also includes: If the current vehicle speed is less than the set speed, determine whether the brake pedal opening is greater than or equal to the set opening; If the brake pedal opening is greater than or equal to the set opening, the motor is controlled to the speed mode, and the target speed is zero, and the motor speed is controlled to adjust toward the target speed.

4. The electric vehicle braking control method according to claim 3, characterized in that: Controlling the motor speed to adjust to the target speed includes: The motor torque is controlled to adjust toward the current target braking torque according to the current motor braking torque setting change rate.

5. The electric vehicle braking control method according to claim 3, characterized in that: Braking energy recovery also includes: if the current brake pedal opening is less than the set opening, the motor is controlled to be in torque mode and the braking torque is zero.

6. The electric vehicle braking control method according to claim 1, characterized in that: The energy recovery conditions include the current SOC of the vehicle battery being less than a set value, the current ABS not being triggered, and the current brake pedal opening being greater than zero or the current accelerator pedal opening and the current brake pedal opening being both zero.

7. A vehicle, characterized in that Vehicle braking control is performed using the electric vehicle braking control method described in any one of claims 1 to 6.

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