Dragging torque control method and device for electric vehicle and storage medium

Abstract

The invention discloses an electric vehicle dragging torque control method and device and a storage medium, and the method comprises the steps: building the oil pressure of a hydraulic braking system when a vehicle speed threshold value is met, enabling the hydraulic braking system and a DTC to work cooperatively so as to generate expected braking force, and when the vehicle is recognized to step from a low-adhesion road condition to a high-adhesion road condition, controlling the hydraulic braking system to work cooperatively. The braking force is gradually smaller than that of a hydraulic braking system; and the braking force of electric braking is correspondingly increased. According to the invention, sufficient braking force can be obtained when the vehicle enters the high-pressure vehicle, the kinetic energy of the vehicle can be fully recovered, and the energy efficiency of the vehicle is improved.

Description

Technical Field

[0001] The present application relates to the technical field of new energy vehicles, and in particular to a method, device and storage medium for controlling the drag torque of an electric vehicle. Background Art

[0002] With the development of new energy vehicles, the strength of the regenerative torque is getting stronger and stronger. However, on certain special roads, such as when the vehicle jumps from high adhesion (i.e., high adhesion road conditions) to low adhesion (i.e., low adhesion road conditions), and when driving on pure low adhesion roads, excessive regenerative torque can cause tire locking, vehicle instability, and safety accidents. In the prior art, the regenerative torque is mainly adjusted through the DTC (drag torque control) function. When it is identified that the wheel end has an excessive slip rate due to the influence of the regenerative torque, the DTC function will intervene in the torque control and control the regenerative torque at a lower level, thereby controlling the slip rate of the wheel end at a reasonable level.

[0003] Regarding the DTC (Drag Torque Control) function, Robert Bosch GmbH has applied for an invention patent with publication number: CN112389389B, entitled Single-pedal Braking Control System and Single-pedal Braking Control Method. This patent is mainly aimed at the situation that when the vehicle encounters a downhill section in single-pedal mode, due to the influence of gravity, the actual deceleration of the vehicle is inconsistent with the deceleration expected by the driver. The braking system actively builds up sufficient hydraulic pressure at the wheel end to achieve the driver's expected deceleration.

[0004] Beijing New Energy Automobile Co., Ltd. has applied for a patent for a control method and device for a single-pedal vehicle and an invention patent for a single-pedal vehicle with publication number CN108082152B. The patent is mainly aimed at the situation that in the single-pedal mode, when the motor speed is low, the efficiency is reduced, resulting in the motor being unable to provide sufficient recovery torque, and the ESP (electronic stability system) actively boosts and assists braking.

[0005] However, the above-mentioned prior arts are unable to solve the technical problem that the vehicle cannot immediately obtain sufficient deceleration when the vehicle changes from a low-adhesion road condition to a high-adhesion road condition while driving. Summary of the invention

[0006] In view of the above problems, the present application provides a drag torque control method for an electric vehicle, which is used to solve the technical problem that the DTC function cannot provide sufficient braking force for the vehicle when the vehicle steps from low attachment to high attachment.

[0007] To achieve the above object, the present application provides a method for controlling the drag torque of an electric vehicle, comprising the following steps:

[0008] When the accelerator pedal of the vehicle is released and the brake pedal is not depressed, the vehicle's electric braking mechanism is activated to decelerate the vehicle through electric braking;

[0009] Detecting whether the vehicle is slipping in the electric brake mechanism, and triggering the DTC mechanism to reduce the anti-drag torque of the electric brake when the slip is detected; and determining whether the current vehicle speed is greater than a preset threshold value, and if so, establishing the oil pressure of the hydraulic brake system of the vehicle, and reducing the anti-drag torque of the electric brake in the DTC mechanism, so that the vehicle obtains the expected braking force through the hydraulic brake system and the electric brake;

[0010] Detect whether the vehicle is moving from a low-adhesion road condition to a high-adhesion road condition. If so, reduce the oil pressure of the hydraulic brake system and increase the anti-drag torque of the electric brake in the DTC mechanism, so that the vehicle can reduce the braking force of the hydraulic brake system and still maintain the expected braking force or increase the expected braking force.

[0011] Further, in the step of “establishing the oil pressure of the hydraulic brake system of the vehicle and reducing the back-drag torque of the electric brake in the DTC mechanism”, the back-drag torque of the electric brake in the DTC mechanism is gradually reduced to 0 Nm; and

[0012] In the step of “reducing the oil pressure of the hydraulic brake system and increasing the anti-drag torque of the electric brake in the DTC mechanism”, the oil pressure of the hydraulic brake system is gradually reduced to a minimum value so that the braking force of the hydraulic brake system is zero.

[0013] Furthermore, after detecting whether the current vehicle speed is greater than a preset threshold value, and before establishing the oil pressure of the vehicle's hydraulic braking system and reducing the back-drag torque of the electric brake in the DTC mechanism, it also includes waiting for a preset time t to avoid abnormal special road conditions triggering the DTC mechanism, and the preset time t is 300ms-800ms.

[0014] Furthermore, the detection of whether the vehicle is moving from a low-adhesion road condition to a high-adhesion road condition is obtained by identifying a change in the deceleration of the vehicle and / or a change in the wheel speed of the vehicle.

[0015] Furthermore, the threshold value of the current vehicle speed is determined according to the docking point speed when the vehicle slides from a high-adhesion road condition to a wet basalt road surface in the high kinetic energy recovery mode.

[0016] Furthermore, the expected braking force is calculated by the vehicle controller according to the current driving mode of the vehicle and the opening of the accelerator pedal when the brake pedal is not depressed.

[0017] In order to solve the above technical problems, this application also provides another technical solution:

[0018] A drag torque control device for an electric vehicle, comprising:

[0019] An activation module, used for activating an electric braking mechanism of the vehicle when the accelerator pedal of the vehicle is released and the brake pedal is not depressed, so as to decelerate the vehicle through electric braking;

[0020] A slip processing module, used to detect whether the vehicle slips in the electric brake mechanism, and trigger the DTC mechanism to reduce the anti-drag torque of the electric brake when slip is detected; and determine whether the current vehicle speed is greater than a preset threshold value, and if so, establish the oil pressure of the hydraulic brake system of the vehicle, and reduce the anti-drag torque of the electric brake in the DTC mechanism, so that the vehicle obtains the expected braking force through the hydraulic brake system and the electric brake;

[0021] The brake switching module is used to detect whether the vehicle is changing from a low-adhesion road condition to a high-adhesion road condition. If so, the oil pressure of the hydraulic brake system is reduced, and the anti-drag torque of the electric brake in the DTC mechanism is increased, so that the vehicle can reduce the braking force of the hydraulic brake system and still maintain the expected braking force or increase the expected braking force.

[0022] Furthermore, it also includes a waiting module, which is used to wait for a preset time t after detecting whether the current vehicle speed is greater than a preset threshold value and before establishing the oil pressure of the vehicle's hydraulic braking system and reducing the back-drag torque of the electric brake in the DTC mechanism, so as to avoid abnormal special road conditions from triggering the DTC mechanism, and the preset time t is 300ms-800ms.

[0023] Furthermore, the detection of whether the vehicle is moving from a low-adhesion road condition to a high-adhesion road condition is obtained by identifying a change in the deceleration of the vehicle and / or a change in the wheel speed of the vehicle.

[0024] In order to solve the above technical problems, this application also provides another technical solution:

[0025] A computer-readable storage medium stores a computer program, wherein when the computer program is executed by a processor, the electric vehicle drag torque control method described in any one of the above technical solutions is executed.

[0026] Different from the prior art, the above technical solution can perform torque control through DTC when the vehicle slips under electric braking, so as to curb the slip in time, and establish the oil pressure of the hydraulic braking system to make the hydraulic braking system work together with DTC when the vehicle speed threshold is met to generate the expected braking force, and when it is identified that the vehicle jumps from low-adhesion road conditions to high-adhesion road conditions, the braking force of the hydraulic braking system is gradually reduced and the braking force of the electric brake (i.e., kinetic energy recovery torque) is increased accordingly, thereby ensuring that the vehicle obtains sufficient braking force when entering high-adhesion road conditions, and can fully recover the kinetic energy of the vehicle, thereby improving the energy efficiency of the vehicle.

[0027] The above-mentioned records related to the invention content are only an overview of the technical solution of the present application. In order to enable ordinary technicians in the field to more clearly understand the technical solution of the present application, and then implement it according to the text of the specification and the contents recorded in the drawings, and to make the above-mentioned purpose and other purposes, features and advantages of the present application easier to understand, the following is an explanation in combination with the specific implementation mode and drawings of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings are only used to illustrate the principles, implementation methods, applications, characteristics and effects of the specific embodiments of the present invention and other related contents, and shall not be considered as limiting the present application.

[0029] In the drawings of the specification:

[0030] Figure 1 It is a flowchart of the drag torque control method of the electric vehicle according to the specific implementation method;

[0031] Figure 2 It is a flowchart of the drag torque control method of the electric vehicle according to the specific implementation method;

[0032] Figure 3 It is a module block diagram of the electric vehicle drag torque control device according to a specific implementation method;

[0033] Figure 4 A schematic diagram of a computer-readable storage medium according to a specific embodiment;

[0034] The reference numerals in the above drawings are described as follows: 300, electric vehicle drag torque control device; 301, activation module; 302, slip processing module; 303, brake switching module; 400, computer readable storage medium; DETAILED DESCRIPTION

[0035] In order to explain in detail the possible application scenarios, technical principles, specific schemes that can be implemented, and the purposes and effects that can be achieved, the following is a detailed description of the specific embodiments listed in conjunction with the accompanying drawings. The embodiments described herein are only used to more clearly illustrate the technical solutions of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0036] Reference to "embodiment" herein means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The term "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or association with other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the various technical features mentioned in the embodiments can be combined in any way to form a corresponding implementable technical solution.

[0037] Unless otherwise defined, the technical terms used in this document have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms in this document is only for describing specific embodiments and is not intended to limit this application.

[0038] In the description of this application, the term "and / or" is an expression used to describe the logical relationship between objects, indicating that three relationships may exist, for example, A and / or B, which means: A exists, B exists, and A and B exist at the same time. In addition, the character " / " in this article generally indicates that the objects before and after are in an "or" logical relationship.

[0039] In the present application, terms such as “first” and “second” are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship of quantity, priority or sequence between these entities or operations.

[0040] Without further limitations, in this application, the words "include", "comprises", "has" or other similar open-ended expressions used in sentences are intended to cover non-exclusive inclusion. These expressions do not exclude the presence of additional elements in the process, method or product including the elements, so that the process, method or product including a series of elements may include not only those limited elements, but also other elements not explicitly listed, or also include elements inherent to such process, method or product.

[0041] Similar to the understanding in the Examination Guidelines, in this application, expressions such as "greater than", "less than", "exceed" and the like are understood to exclude the number itself; expressions such as "above", "below", "within" and the like are understood to include the number itself. In addition, in the description of the embodiments of this application, "multiple" means more than two (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups", "multiple times", etc., unless otherwise clearly and specifically limited.

[0042] In the description of the embodiments of the present application, space-related expressions used, such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate the orientation or position relationship based on the orientation or position relationship shown in the specific embodiments or drawings, and are only for the convenience of describing the specific embodiments of the present application or facilitating the reader's understanding, and do not indicate or imply that the referred device or component must have a specific position, a specific orientation, or be constructed or operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0043] Unless otherwise expressly specified or limited, in the description of the embodiments of the present application, the terms such as "install", "connect", "connect", "fix", "set", etc. used should be understood in a broad sense. For example, the "connection" can be a fixed connection, a detachable connection, or an integrated setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. For technicians in the technical field to which the present application belongs, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0044] See also Figure 1 , this embodiment provides a method for controlling the drag torque of an electric vehicle. The method for controlling the drag torque of an electric vehicle can be applied to new energy vehicles driven by motors, including pure electric-driven electric vehicles, plug-in hybrid electric vehicles, extended-range electric vehicles, and other vehicles equipped with drive motors to provide power for the vehicles, and the drive motor can be reversely dragged to provide electric braking force for the vehicle, and the kinetic energy of the vehicle can be recovered, that is, the drive motor can be used as a generator, and when the vehicle reversely drags the drive motor to rotate (that is, in the driving mode, the drive motor drives the vehicle, and in the kinetic energy recovery mode, the inertia of the vehicle drives the drive motor to rotate, and the drive motor generates electricity and provides electric braking force), the kinetic energy of the vehicle can be recovered to charge the power battery.

[0045] The electric vehicle drag torque control method actively establishes the oil pressure of the hydraulic brake system, so that the hydraulic brake system and the electric brake work together and switch in time, which can not only ensure that the vehicle has sufficient braking force when entering high adhesion from low adhesion, but also can efficiently recover the kinetic energy of the vehicle and improve the energy efficiency of the vehicle.

[0046] like Figure 1 As shown, the electric vehicle drag torque control method described in this embodiment includes the following steps:

[0047] S101. When the accelerator pedal of the vehicle is released and the brake pedal is not depressed, the electric braking mechanism of the vehicle is activated to decelerate the vehicle through electric braking.

[0048] S102, detecting slip, reducing the back-drag torque of the electric brake, and establishing hydraulic brake oil pressure; specifically including: detecting whether the vehicle slips in the electric brake mechanism, and triggering the DTC mechanism to reduce the back-drag torque of the electric brake when slip is detected; and determining whether the current vehicle speed is greater than a preset threshold value, and if so, establishing the oil pressure of the vehicle's hydraulic brake system, and reducing the back-drag torque of the electric brake in the DTC mechanism, so that the vehicle obtains the expected braking force through the hydraulic brake system and the electric brake.

[0049] S103, detecting whether high adhesion is being performed, and gradually switching hydraulic braking to electric braking; which specifically includes: detecting whether the vehicle is changing from a low adhesion road condition to a high adhesion road condition, and if so, reducing the oil pressure of the hydraulic braking system, and increasing the anti-drag torque of the electric brake in the DTC mechanism, so that the vehicle reduces the braking force of the hydraulic braking system and can still maintain the expected braking force or increase the expected braking force.

[0050] In this embodiment, the electric vehicle is in single-pedal mode, that is, when the accelerator pedal (also called the gas pedal) is released during the driving process of the vehicle, even if the brake pedal is not pressed at this time, the vehicle will be electrically braked by the drive motor to recover the vehicle's kinetic energy. In non-single-pedal mode, the vehicle will not recover kinetic energy and slow down when the accelerator pedal is released during driving, and will only slow down when the brake pedal is pressed. In this embodiment, the electric vehicle adopts a single-pedal mode, and the electric braking mechanism of the vehicle is activated when the accelerator pedal is detected to be released, and the kinetic energy of the vehicle is recovered and the vehicle is decelerated through electric braking. Among them, the torque of the vehicle's electric braking is also called recovery torque.

[0051] In step S102, when the vehicle is detected to be slipping, the DTC mechanism is triggered, wherein the slipping is whether the wheels of the vehicle are slipping with the road surface, and the vehicle slipping can be detected by the existing active safety modules on the vehicle, such as the ESP module of the vehicle. When the rotation speed deviation of each wheel of the vehicle is greater than a certain value (i.e., greater than the conventional turning wheel speed difference), it can be considered that the vehicle is slipping. In this embodiment, a hydraulic pump and a proportional pressure relief valve are added through the hydraulic system, and the hydraulic pump and the proportional pressure relief valve are both connected to the hydraulic circuit of the hydraulic system. The oil pressure of the hydraulic system can be increased by the hydraulic pump, and the oil pressure of the hydraulic system can be reduced by the proportional pressure relief valve. Therefore, when the brake pedal is not used, the controller can control the oil pressure and braking force of the hydraulic brake system by controlling the hydraulic pump and the proportional pressure relief valve. Therefore, the oil pressure and braking force of the hydraulic brake system can be established by the hydraulic pump.

[0052] In step S103, when it is detected that the vehicle changes from a low-adhesion road condition to a high-adhesion road condition, the braking force of the vehicle's hydraulic brake system is gradually reduced, which can be achieved by gradually reducing the oil pressure of the hydraulic brake system. While reducing the braking force of the hydraulic brake system, the braking torque of the electric brake force is gradually increased (i.e., the recovery torque is increased), so that the vehicle switches from hydraulic braking to pure electric braking.

[0053] In this embodiment, in the "establishing the oil pressure of the vehicle's hydraulic braking system and reducing the back-drag torque of the electric brake in the DTC mechanism", the back-drag torque of the electric brake in the DTC mechanism is gradually reduced to 0Nm; and in the "reducing the oil pressure of the hydraulic braking system and increasing the back-drag torque of the electric brake in the DTC mechanism", the oil pressure of the hydraulic braking system is gradually reduced to the minimum value so that the braking force of the hydraulic braking system is 0.

[0054] And in the present embodiment, taking into account that the DTC function may be abnormally triggered when the vehicle passes through some special road surfaces, such as speed bumps, ditches, etc., in order to avoid the DTC function being abnormally triggered, after detecting whether the current vehicle speed is greater than the preset threshold value, and before establishing the oil pressure of the vehicle's hydraulic braking system and reducing the anti-drag torque of the electric brake in the DTC mechanism, it also includes waiting for a preset time t to avoid abnormal triggering of the DTC mechanism due to special road conditions. The preset time t is 300ms-800ms.

[0055] In this embodiment, after the DTC function is triggered, the actual torque of the vehicle reaches the requested torque of the DTC function. At this time, the hydraulic braking system is pressurized according to the torque required by the driver so that the hydraulic braking system meets the required braking torque, and the DTC function remains activated until the exit condition is met.

[0056] In the related art, when the vehicle is coasting from low attachment to high attachment, when the driver completely releases the accelerator pedal, the VCU (vehicle control unit) will request a negative torque (Trqcmd) so that the vehicle obtains a certain braking force. However, under the action of the DTC, the motor will prioritize the requested torque of the DTC, and the vehicle cannot obtain the desired deceleration. In this embodiment, in this case, the oil pressure of the hydraulic brake system will be actively established to provide braking torque, and the electric brake will be converted into hydraulic brake. The target braking force should be calculated according to Trqcmd. Therefore, this embodiment takes into account the stability and braking performance of the vehicle, so that the vehicle can quickly obtain the desired deceleration when it is coasting from low attachment to high attachment.

[0057] See also Figure 2 In order to better understand the electric vehicle drag torque control method, Figure 2 A more detailed flowchart is provided.

[0058] Specifically, when the vehicle detects that the driver has released the accelerator pedal and has not stepped on the brake pedal, the vehicle's electric brake is activated, thereby recovering kinetic energy through the drive motor and reducing the vehicle's speed. After the electric brake is activated, the vehicle detects whether the drive wheel is slipping (i.e., whether the electric brake's retraction torque is too large to cause the drive wheel to slip). If slipping occurs, the DTC is triggered, and the electric brake torque is reduced through the DTC function to reduce or control slippage. After the DTC function is triggered, the vehicle detects whether the current vehicle speed meets the vehicle speed threshold value. If it does not meet the vehicle speed threshold value, the existing conventional DTC is used to control the vehicle's electric brake torque; if the vehicle speed threshold value is met, the DTC controls the electric brake torque (i.e., the recovery torque) to decrease, and eventually reduce it to 0Nm. The vehicle braking force required by the vehicle (i.e., the expected braking force of the vehicle) is calculated according to the opening of the accelerator pedal, and the oil pressure of the hydraulic brake system is actively established through the hydraulic pump so that the hydraulic brake system can achieve the above-mentioned expected braking force. In some cases, if the torque of the electric brake force has not dropped to 0Nm, at this time, the torque of the electric force is added to the braking torque of the hydraulic brake system to meet the expected braking force. After the braking force of the hydraulic brake system is established, the vehicle identifies whether it has entered a high-adhesion road condition, that is, whether it has stepped from a low-adhesion road condition to a high-adhesion road condition. If so, the braking force of the hydraulic brake system is gradually reduced by opening the proportional pressure relief valve, and the DTC controls the electric brake torque to increase. The vehicle braking force is gradually converted from hydraulic brake system braking to electric brake until the hydraulic brake system braking force is completely withdrawn. When the braking force of the hydraulic brake system is completely withdrawn, it is switched to conventional DTC to control the torque of the electric brake.

[0059] In this embodiment, the expected braking force is calculated by the vehicle controller based on the current driving mode of the vehicle and the opening of the accelerator pedal when the brake pedal is not pressed. When the driver does not step on the brake pedal, the vehicle controller can calculate the driver's required torque based on the driving mode and the opening of the accelerator pedal. When the accelerator pedal opening is less than a certain threshold, the driver's required torque is a negative value, that is, the electric brake is activated, and the negative value corresponds to the recovery torque. At this time, the controller can calculate the braking force of the vehicle based on the recovery torque, that is, the above-mentioned expected braking force.

[0060] In the above embodiment, the detection of whether the vehicle is changing from a low-adhesion road condition to a high-adhesion road condition is obtained by identifying the change in the vehicle's deceleration and / or the change in the vehicle's wheel speed. When the vehicle is sliding on a low-adhesion road, even if the actuator builds up enough pressure, the vehicle cannot obtain enough deceleration and may even enter the ABS (anti-lock braking system). However, when the vehicle enters a high-adhesion road condition, due to the change in the ground adhesion coefficient, the vehicle's deceleration will change, and the rate of change of the wheel speed will also change significantly. Therefore, the controller can identify the ground adhesion coefficient based on the change in deceleration and wheel speed.

[0061] The threshold value of the current vehicle speed is determined according to the docking point speed when the vehicle slides from a high-adhesion road condition to a wet basalt road surface in a high kinetic energy recovery mode.

[0062] like Figure 3 As shown, in another embodiment, a drag torque control device 300 for an electric vehicle is provided. The drag torque control device 300 for an electric vehicle includes: an activation module 301 , a slip processing module 302 and a brake switching module 303 .

[0063] The activation module 301 is used to activate the electric braking mechanism of the vehicle when the accelerator pedal of the vehicle is released and the brake pedal is not pressed, so as to decelerate the vehicle through electric braking.

[0064] The slip processing module 302 is used to detect whether the vehicle slips in the electric braking mechanism, and to trigger the DTC mechanism to reduce the anti-drag torque of the electric brake when slip is detected; and to determine whether the current vehicle speed is greater than a preset threshold value. If so, the oil pressure of the vehicle's hydraulic braking system is established, and the anti-drag torque of the electric brake in the DTC mechanism is reduced, so that the vehicle obtains the expected braking force through the hydraulic braking system and the electric brake.

[0065] The brake switching module 303 is used to detect whether the vehicle is changing from a low-adhesion road condition to a high-adhesion road condition. If so, the oil pressure of the hydraulic brake system is reduced, and the anti-drag torque of the electric brake in the DTC mechanism is increased, so that the vehicle reduces the braking force of the hydraulic brake system and still maintains the expected braking force or increases the expected braking force.

[0066] Specifically, the electric vehicle drag torque control device 300 further includes a waiting module. The waiting module is used to wait for a preset time t after detecting whether the current vehicle speed is greater than a preset threshold value and before establishing the oil pressure of the vehicle's hydraulic brake system and reducing the anti-drag torque of the electric brake in the DTC mechanism, so as to avoid abnormal special road conditions from triggering the DTC mechanism, and the preset time t is 300ms-800ms.

[0067] Furthermore, the detection of whether the vehicle is moving from a low-adhesion road condition to a high-adhesion road condition is obtained by identifying a change in the deceleration of the vehicle and / or a change in the wheel speed of the vehicle.

[0068] In the related art, when the vehicle is coasting from low attachment to high attachment, when the driver completely releases the accelerator pedal, the VCU (vehicle control unit) will request a negative torque (Trqcmd) so that the vehicle obtains a certain braking force. However, under the action of the DTC, the motor will prioritize the requested torque of the DTC, and the vehicle cannot obtain the desired deceleration. In this embodiment, in this case, the oil pressure of the hydraulic brake system will be actively established to provide braking torque, and the electric brake will be converted into hydraulic brake. The target braking force should be calculated according to Trqcmd. Therefore, this embodiment takes into account the stability and braking performance of the vehicle, so that the vehicle can quickly obtain the desired deceleration when it is coasting from low attachment to high attachment.

[0069] like Figure 4 As shown, in one embodiment, a computer-readable storage medium 400 is provided, in which a computer program is stored. When the computer program is executed by a processor, the electric vehicle drag torque control method described in any one of the embodiments is executed.

[0070] The computer-readable storage medium may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. The non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a ferromagnetic random access memory (FRAM), a flash memory, a magnetic surface memory, an optical disk, or a compact disc read-only memory (CD-ROM); the magnetic surface memory may be a disk memory or a tape memory.

[0071] The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example but not limitation, many forms of RAM are available, such as static random access memory (SR AM), synchronous static random access memory (SSR AM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM), direct memory bus random access memory (DRRAM). The computer-readable storage medium described in the embodiments of the present invention is intended to include these and any other suitable types of memory.

[0072] In some embodiments, the processor can be implemented by software, hardware, firmware or a combination thereof, and can use a circuit, a single or multiple application specific integrated circuits (Application Specific Integrated Circuit, ASIC), a digital signal processor (Digital Signal Processor, DSP), a digital signal processing device (Digital Signal Processing Device, DSPD), a programmable logic device (Programmable Logic Device, PLD), a field programmable gate array (Field Programmable Gate Array, FPGA), a central processing unit (Central Processing Unit, CPU), a controller, a microcontroller, at least one of a microprocessor, so that the processor can execute some steps or all steps or any combination of the steps in the electric vehicle drag torque control method in each embodiment of the present application.

[0073] Finally, it should be noted that although the above embodiments have been described in the specification and drawings of this application, this does not limit the scope of patent protection of this application. All technical solutions generated by replacing or modifying equivalent structures or equivalent processes based on the essential concept of this application using the contents recorded in the specification and drawings of this application, as well as directly or indirectly implementing the technical solutions of the above embodiments in other related technical fields, are included in the scope of patent protection of this application.

Claims

1. A method for controlling the drag torque of an electric vehicle, characterized in that: The following steps are involved: When the accelerator pedal of the vehicle is released and the brake pedal is not depressed, the vehicle's electric braking mechanism is activated to decelerate the vehicle through electric braking; Detecting whether the vehicle is slipping in the electric brake mechanism, and triggering the DTC mechanism to reduce the anti-drag torque of the electric brake when the slip is detected; and determining whether the current vehicle speed is greater than a preset threshold value, and if so, establishing the oil pressure of the hydraulic brake system of the vehicle, and reducing the anti-drag torque of the electric brake in the DTC mechanism, so that the vehicle obtains the expected braking force through the hydraulic brake system and the electric brake; Detect whether the vehicle is moving from a low-adhesion road condition to a high-adhesion road condition. If so, reduce the oil pressure of the hydraulic brake system and increase the anti-drag torque of the electric brake in the DTC mechanism, so that the vehicle can reduce the braking force of the hydraulic brake system and still maintain the expected braking force or increase the expected braking force.

2. The electric vehicle drag torque control method according to claim 1, characterized in that: In the step of “establishing the oil pressure of the hydraulic brake system of the vehicle and reducing the back-drag torque of the electric brake in the DTC mechanism”, the back-drag torque of the electric brake in the DTC mechanism is gradually reduced to 0 Nm; and In the "reducing the oil pressure of the hydraulic brake system and increasing the anti-drag torque of the electric brake in the DTC mechanism", the oil pressure of the hydraulic brake system is gradually reduced to a minimum value so that the braking force of the hydraulic brake system is 0.

3. The electric vehicle drag torque control method according to claim 1 or 2, characterized in that: After detecting whether the current vehicle speed is greater than the preset threshold value, and before establishing the oil pressure of the vehicle's hydraulic braking system and reducing the back-drag torque of the electric brake in the DTC mechanism, it also includes waiting for a preset time t to avoid abnormal special road conditions triggering the DTC mechanism. The preset time t is 300ms-800ms.

4. The electric vehicle drag torque control method according to claim 1 or 2, characterized in that: The detection of whether the vehicle is changing from a low-adhesion road condition to a high-adhesion road condition is obtained by identifying a change in the deceleration of the vehicle and / or a change in the wheel speed of the vehicle.

5. The electric vehicle drag torque control method according to claim 1, characterized in that: The threshold value of the current vehicle speed is determined according to the docking point speed when the vehicle slides from a high-adhesion road condition to a wet basalt road surface in a high kinetic energy recovery mode.

6. The electric vehicle drag torque control method according to claim 1, characterized in that: The expected braking force is calculated by the vehicle controller according to the current driving mode of the vehicle and the opening of the accelerator pedal when the brake pedal is not depressed.

7. A drag torque control device for an electric vehicle, characterized in that: include: An activation module, used for activating an electric braking mechanism of the vehicle when the accelerator pedal of the vehicle is released and the brake pedal is not depressed, so as to decelerate the vehicle through electric braking; A slip processing module, used to detect whether the vehicle slips in the electric brake mechanism, and trigger the DTC mechanism to reduce the anti-drag torque of the electric brake when slip is detected; and determine whether the current vehicle speed is greater than a preset threshold value, and if so, establish the oil pressure of the hydraulic brake system of the vehicle, and reduce the anti-drag torque of the electric brake in the DTC mechanism, so that the vehicle obtains the expected braking force through the hydraulic brake system and the electric brake; The brake switching module is used to detect whether the vehicle is changing from a low-adhesion road condition to a high-adhesion road condition. If so, the oil pressure of the hydraulic brake system is reduced, and the anti-drag torque of the electric brake in the DTC mechanism is increased, so that the vehicle can reduce the braking force of the hydraulic brake system and still maintain the expected braking force or increase the expected braking force.

8. The electric vehicle drag torque control device according to claim 7, characterized in that: It also includes a waiting module, which is used to wait for a preset time t after detecting whether the current vehicle speed is greater than a preset threshold value and before establishing the oil pressure of the vehicle's hydraulic braking system and reducing the back-drag torque of the electric brake in the DTC mechanism, so as to avoid abnormal special road conditions triggering the DTC mechanism. The preset time t is 300ms-800ms.

9. The electric vehicle drag torque control device according to claim 7, characterized in that: The detection of whether the vehicle is changing from a low-adhesion road condition to a high-adhesion road condition is obtained by identifying a change in the deceleration of the vehicle and / or a change in the wheel speed of the vehicle.

10. A computer-readable storage medium having a computer program stored therein, characterized in that: When the computer program is executed by a processor, the electric vehicle drag torque control method according to any one of claims 1 to 6 is executed.

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