Control method and system for virtual low-speed four-wheel drive of electric cross-country vehicle

Abstract

The invention discloses a virtual low-speed four-wheel-drive control method and system for an electric cross-country four-wheel-drive automobile, and relates to the technical field of electric automobile control. The method does not need to depend on a traditional transfer case structure, core components such as a motor control unit (MCU) and an integrated brake controller (IBC) are coordinated through a vehicle control unit (VCU), and the virtual low-speed four-wheel drive function is achieved. And after entering the low-speed four-wheel drive mode, the VCU controls the front motor and the rear motor to be switched to the rotating speed control mode, the target rotating speed, the torque attenuation coefficient and the peak torque of the motors are associated with the pedal opening degree according to the idling scene, the braking scene and the acceleration scene, and stable control over power output is achieved through accurate parameter calibration. The technical problems that a traditional low-speed four-wheel-drive system is high in cost and complex in whole vehicle arrangement are solved, the cross-country power performance is guaranteed, meanwhile, the whole vehicle structure is simplified, the manufacturing cost is reduced, and the driving operation convenience is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric vehicle control, and in particular to a control method and system for virtual low-speed four-wheel drive of an electric off-road vehicle. BACKGROUND

[0002] In the field of off-road vehicles, low-speed four-wheel drive (4L) function is the core configuration to improve the vehicle's climbing ability and passing ability on complex road conditions. The low-speed four-wheel drive function of traditional fuel vehicles is realized through a transfer case. The transfer case can switch different reduction ratio gears. When switching to the low-speed four-wheel drive gear, the driving torque is increased by increasing the reduction ratio to meet the off-road working condition requirements.

[0003] However, the traditional technical solution has obvious defects:

[0004] 1. High cost: The transfer case is a mechanical structure that requires the design of a multi-gear transmission mechanism, which requires high precision of parts processing, resulting in increased manufacturing costs;

[0005] 2. Complex vehicle layout: The transfer case is large in size and requires additional vehicle space, increasing the difficulty of chassis layout;

[0006] 3. Increased vehicle weight: The transfer case and supporting transmission components will increase the weight of the vehicle, affecting the vehicle's range and fuel economy;

[0007] 4. Difficult to operate: In the traditional low-speed four-wheel drive mode, the driver needs to control the power output by adjusting the depth of the accelerator, which is difficult to accurately control the vehicle in extreme off-road conditions.

[0008] With the development of electric vehicle technology, electric off-road four-wheel drive vehicles use a front and rear dual-motor independent drive architecture. The motor naturally has a large torque output characteristic in the low-speed range, eliminating the need to adjust the reduction ratio of the transfer case to meet the off-road power requirements. Based on this characteristic, there is an urgent need for a control method and system for virtual low-speed four-wheel drive of an electric off-road vehicle to address the shortcomings of existing technology. SUMMARY

[0009] The present application aims to solve at least one of the technical problems in the prior art and proposes a control method and system for virtual low-speed four-wheel drive of an electric off-road vehicle.

[0010] In a first aspect, the present application provides a control method for virtual low-speed four-wheel drive of an electric off-road vehicle, comprising:

[0011] Sending a low-speed four-wheel drive mode request to the vehicle control unit through the human-machine interaction interface. The vehicle control unit receives the request and sends a speed control mode switching instruction to the motor control unit;

[0012] The integrated brake controller collects the brake pedal opening signal and transmits it to the vehicle control unit through the CAN bus.

[0013] The vehicle control unit collects the accelerator pedal opening signal and judges the current working condition in combination with the brake pedal opening signal. The vehicle control unit matches the corresponding control parameters according to the current working condition and sends the control parameters to the motor control unit.

[0014] The motor control unit adjusts the motor speed and torque before and after according to the speed control mode switching instruction and the control parameters to ensure speed synchronization.

[0015] The current working condition includes idle scene working condition, braking scene working condition and acceleration scene working condition.

[0016] Further, the vehicle control unit matches the corresponding control parameters according to the current working condition, and the control parameters include motor target speed, motor actual output torque attenuation coefficient, and motor peak torque, and all control parameters can be calibrated.

[0017] Further, the vehicle control unit matches the corresponding control parameters according to the current working condition, and when the current working condition is the idle scene working condition, the front and rear motor target speeds in the scene are set to a fixed value a, and a is a calibratable parameter.

[0018] Further, the vehicle control unit matches the corresponding control parameters according to the current working condition, and when the current working condition is the braking scene working condition, the corresponding control parameter matching method includes: when the vehicle is in D mode, the motor target speed decreases linearly with the increase of the brake pedal opening, and when the brake pedal opening is 0%, the target speed is 300 rpm, and when the opening is 30%, the target speed is 0 rpm.

[0019] When the vehicle is in R mode, the motor target speed increases linearly with the increase of the brake pedal opening, and when the brake pedal opening is 0%, the target speed is -300 rpm, and when the opening is 30%, the target speed is 0 rpm.

[0020] Further, the vehicle control unit matches the corresponding control parameters according to the current working condition, and when the current working condition is the braking scene working condition, the corresponding control parameter matching method further includes:

[0021] When the vehicle is in D mode, the motor actual output torque attenuation coefficient is related to the motor actual speed and the brake pedal opening. The motor actual speed and the brake pedal opening are obtained when the vehicle is in D mode, and the motor actual output torque attenuation coefficient is matched by a first relationship table obtained in advance.

[0022] When the vehicle is in R gear, the motor actual output torque attenuation coefficient is related to the motor actual speed and the brake pedal opening degree, the motor actual speed and the brake pedal opening degree when in R gear are obtained, and the motor actual output torque attenuation coefficient is obtained through the second relationship matching table obtained in advance.

[0023] Further, the vehicle control unit matches the corresponding control parameters according to the current working condition, and when the current working condition is an acceleration scene working condition, the corresponding control parameter matching method comprises:

[0024] When the vehicle is in D gear, the motor target speed linearly increases with the increase of the accelerator pedal opening degree, the target speed is 300 rpm when the accelerator pedal opening degree is 0%, and the target speed is 1200 rpm when the accelerator pedal opening degree is 90%;

[0025] When the vehicle is in R gear, the motor target speed linearly decreases with the increase of the accelerator pedal opening degree, the target speed is -300 rpm when the accelerator pedal opening degree is 0%, and the target speed is -1200 rpm when the accelerator pedal opening degree is 90%.

[0026] Further, the vehicle control unit matches the corresponding control parameters according to the current working condition, and when the current working condition is an acceleration scene working condition, the corresponding control parameter matching method further comprises:

[0027] The motor peak torque linearly increases with the increase of the accelerator pedal opening degree, the peak torque is 200 Nm when the accelerator pedal opening degree is 0%, and the peak torque is 340 Nm when the accelerator pedal opening degree is 90%.

[0028] In a second aspect, the application also discloses a control system of virtual low-speed four-wheel drive of an electric off-road vehicle, characterized by comprising: a speed control mode switching module, a brake pedal opening degree signal acquisition module, a control parameter matching module and a speed synchronization module; wherein:

[0029] The speed control mode switching module is used for sending a low-speed four-wheel drive mode request to the vehicle control unit through a human-computer interaction interface, and the vehicle control unit sends a speed control mode switching instruction to the motor control unit after receiving the request;

[0030] The brake pedal opening degree signal acquisition module is used for acquiring a brake pedal opening degree signal through an integrated brake controller and transmitting the brake pedal opening degree signal to the vehicle control unit through a CAN bus;

[0031] The control parameter matching module is used for acquiring an accelerator pedal opening degree signal through the vehicle control unit, judging a current working condition in combination with the brake pedal opening degree signal, matching corresponding control parameters by the vehicle control unit according to the current working condition, and sending the control parameters to the motor control unit;

[0032] The rotation speed synchronization module is used for adjusting the rotation speed and torque of the front and rear motors according to the rotation speed control mode switching instruction and the control parameter by the motor control unit, so as to ensure the rotation speed synchronization.

[0033] In a third aspect, the present application further discloses an electronic device, comprising:

[0034] one or more processors;

[0035] a memory for storing one or more programs;

[0036] When the one or more programs are executed by the one or more processors, the one or more processors implement the control method.

[0037] The application discloses a control method for virtual low-speed four-wheel drive of an electric off-road four-wheel drive vehicle, and relates to the technical field of electric vehicle control. The method does not need to rely on a traditional transfer case structure, and realizes the virtual low-speed four-wheel drive function by coordinating core components such as a vehicle control unit (VCU), a motor control unit (MCU) and an integrated brake controller (IBC). After entering the low-speed four-wheel drive mode, the VCU controls the front and rear motors to switch to the rotation speed control mode, and according to three scenes of idling, braking and acceleration, respectively associates the motor target rotation speed, the torque attenuation coefficient and the peak torque with the pedal opening degree, so that stable control of power output is realized through accurate parameter calibration. The application solves the technical problems of high cost and complex vehicle arrangement of the traditional low-speed four-wheel drive system, simplifies the vehicle structure while ensuring off-road power performance, reduces the manufacturing cost, and improves the driving operation convenience.

[0038] Compared with the prior art, the application has at least the following beneficial effects:

[0039] 1. Cost advantage: without additional increase of the transfer case and the matching mechanical structure, the vehicle manufacturing cost and the part procurement cost are reduced;

[0040] 2. Arrangement optimization: the space occupied by the transfer case is saved, the chassis arrangement is simplified, and more installation space is provided for components such as power batteries and energy storage devices;

[0041] 3. Performance improvement: the low-speed large-torque characteristics of the motor are fully utilized, combined with accurate electronic control, the power output is more stable, and the off-road passability is better than that of the traditional mechanical transfer case scheme;

[0042] Convenient operation: the driver directly controls the vehicle speed through the accelerator pedal, without complex gear shifting and accelerator control, and the off-road driving difficulty is reduced;

[0043] 4. Strong adaptability: all control parameters support calibration adjustment, and can be adapted to different types of electric off-road four-wheel drive vehicles, and has strong universality. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 A flow chart of a control method for virtual low-speed four-wheel drive of an electric off-road vehicle is provided for an embodiment of the present application.

[0045] Figure 2 A structural block diagram of a control system for virtual low-speed four-wheel drive of an electric off-road vehicle is provided for an embodiment of the present application.

[0046] Figure 3 A structural block diagram of an electronic device is provided for an embodiment of the present application. DETAILED DESCRIPTION

[0047] For those skilled in the art to better understand the technical solutions of the present application, the exemplary embodiments of the present application are described below in conjunction with the drawings, which include various details of the embodiments of the present application to help understanding, and should be considered only as exemplary. Therefore, those skilled in the art should realize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present application. Also, for the sake of clarity and conciseness, the description below omits the description of well-known functions and structures.

[0048] In the case of no conflict, each embodiment of the present application and each feature in the embodiments can be combined with each other.

[0049] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0050] The terms used herein are only used to describe specific embodiments, and are not intended to limit the present application. As used herein, the singular forms "a" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the terms "comprise" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The terms "connected" or "coupled" and / or similar terms are not limited to a physical or mechanical connection or linkage to either another part or device and can also include an electrical connection, whether direct or indirect.

[0051] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an overly literal or overly formal sense unless expressly so defined herein.

[0052] The collection, storage, use, processing, transmission, provision and disclosure of the user personal information in the technical solution of the present application comply with relevant laws and regulations and do not violate public order and good customs. The use of user data in the technical solution complies with relevant national laws and regulations (for example, the Information Security Technology Personal Information Security Specification). For example, appropriate measures are taken for personal information access control, the display of personal information is limited, the use purpose of personal information does not exceed the direct or reasonably associated range, the use of personal information eliminates the explicit identity pointing and avoids accurate positioning to a specific individual.

[0053] To solve at least one of the technical problems in the related art, the present application provides a control method and system for virtual low-speed four-wheel drive of an electric off-road vehicle.

[0054] The present application provides a control method for virtual low-speed four-wheel drive of an electric off-road vehicle, which comprises the following steps: Figure 1

[0055] S100. Send a low-speed four-wheel drive mode request to the vehicle control unit through the human-machine interaction interface, and send a speed control mode switching instruction to the motor control unit after the vehicle control unit receives the request;

[0056] In the present embodiment, the human-machine interaction interface (HMI) provides a low-speed four-wheel drive mode trigger button to feed back the mode activation state. The vehicle control unit is the core control module of the present method, which is responsible for receiving the driver's operation instruction, collecting the pedal opening signal, judging the working condition and sending the control instruction. The motor control unit receives the speed control instruction and parameters from the VCU and dynamically adjusts the speed and torque output of the front and rear motors.

[0057] In the present embodiment, the specific method implemented by S100 comprises the following steps:

[0058] The driver can initiate the request through the human-machine interaction interface of the vehicle, such as the physical button, the central touch screen or the voice control. For example, press the special four-wheel drive mode switching button or select the "low-speed four-wheel drive" in the driving mode option of the central screen. The interface will convert the operation into a standardized electrical signal, which is then transmitted to the vehicle control unit (VCU) through the CAN bus in the vehicle. The signal will contain key identification information such as mode type and request trigger time to ensure that the VCU accurately identifies the instruction intent.

[0059] ​VCU as the "brain" of the vehicle, after receiving the request will not directly issue instructions, need to complete the multi-dimensional state check and logic processing, to ensure the safety of driving and mode switching smoothness: VCU will read the current state data of the vehicle, to determine whether to meet the activation conditions of low-speed four-wheel drive mode, such as whether the rear axle drive device speed is less than the first preset speed, whether the wheel speed is within the low-speed threshold, etc. If the vehicle speed is too high or the drive system has a fault, it will refuse to switch and alarm the driver through the instrument panel.

[0060] If the switching conditions are met, VCU will develop control logic suitable for low-speed four-wheel drive. The core requirement of low-speed four-wheel drive is large torque output and stable power distribution, so VCU will determine to use a specific target speed as the control reference. VCU will convert the prepared strategy into a speed control mode switching instruction, which contains target speed parameters, speed adjustment rate, mode switching time limit, etc. Then send the instruction to the motor control unit (MCU) through the CAN bus.

[0061] MCU as the "executor" of the power system, after receiving the instruction, completes the switching of the speed mode and the motor control, the specific operation is as follows:

[0062] MCU first parses the instruction issued by VCU, and converts the target speed parameter in it into a control signal that the motor can recognize. For example, for a permanent magnet synchronous motor, the target speed needs to be converted into the corresponding three-phase alternating current frequency and voltage adjustment parameters.

[0063] MCU drives the front and rear axle drive motors to adjust the speed through frequency modulation, voltage modulation and other vector control methods. If it is a four-wheel drive vehicle, it will simultaneously coordinate the front and rear axle motor speeds. When the difference between the actual motor speed and the target speed set by VCU is within the preset error range, the electronic clutch is triggered to engage, completing the stable connection of four-wheel drive power. After switching is completed, MCU will collect motor speed, temperature, current and other running data in real time, and feed back to VCU through CAN bus at a fixed period. If the speed deviates, VCU will issue a fine-tuning instruction again, forming a closed-loop control to ensure stable vehicle power output in low-speed four-wheel drive mode and avoid problems such as power interruption.

[0064] In the whole process, CAN bus plays the role of "nervous system", ensuring the real-time and accuracy of data transmission between VCU and MCU, human-machine interface and other components. The state check and closed-loop control of each link are the key to smooth switching of low-speed four-wheel drive mode.

[0065] S200. The integrated brake controller collects the brake pedal opening signal and transmits it to the vehicle control unit through the CAN bus;

[0066] In the embodiment S200, the core signal interaction method of the integrated brake controller (IBC) and the vehicle control unit (VCU) specifically includes:

[0067] The IBC collects the brake pedal opening degree signal and completes signal conversion; when the driver steps on the brake pedal, two opening degree sensors carried on the pedal will detect the pedal stroke in real time; the sensors will convert the mechanical stroke into corresponding voltage signals, and the built-in electronic control unit (ECU) of the IBC will receive the two voltage signals. Then, referring to the preset voltage-opening degree mapping curve, the voltage signal is converted into 0-100% brake pedal opening degree data, and the opening degree change rate is also recorded synchronously to determine whether the driver is regular braking or emergency braking.

[0068] The standardized signal is transmitted through the CAN bus; the IBC will package the processed opening degree signal, signal validity identifier, and its own working state into a standardized data frame conforming to the vehicle CAN bus communication protocol. The data frame will clearly mark the signal source as IBC and the signal type as brake pedal opening degree, etc. key identifiers to ensure directional signal transmission. Since the CAN bus has the characteristics of multi-node communication and strong anti-interference ability, the data frame will be transmitted on the bus together with the signals of other units such as the battery management system (BMS) and the motor controller (MCU), and each node is equal in status, which can ensure the real-time transmission of the opening degree signal and avoid signal delay affecting the braking response.

[0069] The VCU receives the signal and performs subsequent processing and control; the VCU will diagnose the reasonableness of the received two-way opening degree signal, such as checking whether the signal exceeds the normal voltage range and whether the difference between the two signals exceeds the preset threshold (usually 5%). If a single signal is abnormal, the other valid signal will be used; if both signals are abnormal, the maximum opening degree (100%) will be triggered to trigger the emergency braking logic, and a fault alarm will be triggered. The VCU calculates the corresponding braking demand torque based on the pedal opening degree and the opening degree change rate. For example, when the opening degree is large and the change rate is fast, it is determined as emergency braking, and the braking force is prioritized; when the opening degree is small and the change is smooth, the proportion of regenerative braking and mechanical braking can be coordinated to improve energy recovery efficiency. The VCU will convert the braking demand into specific instructions and feed them back to the IBC and the motor controller (MCU) through the CAN bus. For example, the instruction IBC drives the motor to establish a corresponding hydraulic push wheel cylinder brake, and the instruction MCU adjusts the regenerative braking torque to realize smooth coordination of electric braking and mechanical braking. In addition, the VCU will also send the brake state signal to the combination instrument to allow the driver to directly view the relevant braking information.

[0070] S300. The vehicle control unit collects the accelerator pedal opening degree signal, and judges the current working condition in combination with the brake pedal opening degree signal; the vehicle control unit matches the corresponding control parameters according to the current working condition, and sends the control parameters to the motor control unit;

[0071] In the embodiment, the current working condition includes an idle scene working condition, a braking scene working condition and an accelerating scene working condition. The control parameters include a motor target rotating speed, a motor actual output torque attenuation coefficient and a motor peak torque, and all the control parameters can be calibrated.

[0072] Specifically, when the current working condition is the idle scene working condition, the front and rear motor target rotating speeds in the scene are set as fixed values a, and a is a calibratable parameter. For example, when the vehicle is in a low-speed four-wheel drive mode and neither the accelerator pedal nor the brake pedal is operated, the idle scene is entered. The VCU sends the fixed target rotating speed a (calibratable) to the front and rear MCUs, so as to ensure that the front and rear motor rotating speeds are consistent, maintain the vehicle slow driving or stationary standby state, avoid the vehicle from slipping or power suddenly changing when idling on an off-road road, and improve the driving stability.

[0073] When the current working condition is the braking scene working condition, the corresponding control parameter matching method includes: when the vehicle is in D mode, the motor target rotating speed linearly decreases with the increase of the brake pedal opening degree, the target rotating speed is 300 rpm when the brake pedal opening degree is 0%, and the target rotating speed is 0 rpm when the brake pedal opening degree is 30%; when the vehicle is in R mode, the motor target rotating speed linearly increases with the increase of the brake pedal opening degree, the target rotating speed is -300 rpm when the brake pedal opening degree is 0%, and the target rotating speed is 0 rpm when the brake pedal opening degree is 30%.

[0074] Specifically, when the vehicle is in the low-speed four-wheel drive mode and the driver steps on the brake pedal, the braking scene is entered, and the control parameters are strongly associated with the brake pedal opening degree. When the vehicle is in D mode: the motor target rotating speed linearly decreases with the increase of the brake pedal opening degree, and the specific association relationship is shown in Table 1:

[0075] Table 1 Relationship table of D mode motor target rotating speed and brake pedal opening degree

[0076]

[0077] When the vehicle is in R mode, the motor target rotating speed linearly increases (absolute value decreases) with the increase of the brake pedal opening degree, and the specific association relationship is shown in Table 2:

[0078] Table 2 Relationship table of R mode motor target rotating speed and brake pedal opening degree

[0079]

[0080] In the embodiment, when the current working condition is the braking scene working condition, the corresponding control parameter matching method further includes:

[0081] When the vehicle is running in D, the actual output torque attenuation coefficient of the motor is related to the actual motor speed and the brake pedal opening. The actual motor speed and the brake pedal opening are obtained when the vehicle is running in D, and the actual output torque attenuation coefficient of the motor is obtained by matching the first relationship table obtained in advance. In the first relationship table, when the brake pedal opening is 0%, the actual output torque attenuation coefficient of the motor is 100 (i.e. no attenuation) regardless of the actual motor speed (from -1000 rpm to 1000 rpm).

[0082] As the brake pedal opening gradually increases from 5% to 30%, the torque attenuation coefficient shows different change rules in different actual motor speed intervals: when the actual motor speed is -1000 rpm, the torque attenuation coefficient always remains 100 (no attenuation) regardless of the change of the brake pedal opening (5%-30%). When the actual motor speed is -500 rpm, the torque attenuation coefficient decreases from 100 to 80, 70, 60, 50, 50, 50 in turn as the brake pedal opening increases from 5% to 30%. When the actual motor speed is -300 rpm, the torque attenuation coefficient decreases from 100 to 80, 70, 60, 50, 50, 50 in turn as the brake pedal opening increases from 5% to 30%. When the actual motor speed is -200 rpm, the torque attenuation coefficient decreases from 100 to 40, 30, 30, 20, 20, 10 in turn as the brake pedal opening increases from 5% to 30%. When the actual motor speed is -100 rpm, the torque attenuation coefficient decreases from 100 to 20, 10, 10, 10, 0, 0 in turn as the brake pedal opening increases from 5% to 30%. When the actual motor speed is 0 rpm, the torque attenuation coefficient is 0 (complete attenuation) regardless of the change of the brake pedal opening (5%-30%). When the actual motor speed is 100 rpm, the torque attenuation coefficient is 0 (complete attenuation) regardless of the change of the brake pedal opening (5%-30%). When the actual motor speed is 200 rpm, the torque attenuation coefficient decreases from 100 to 40, 30, 30, 20, 20, 20 in turn as the brake pedal opening increases from 5% to 30%. When the actual motor speed is 300 rpm, the torque attenuation coefficient decreases from 100 to 70, 60, 60, 60, 50, 50 in turn as the brake pedal opening increases from 5% to 30%.

[0083] When the actual motor speed is 500 rpm, the torque attenuation coefficient decreases from 100 to 80, 70, 70, 70, 60, 60 in turn as the brake pedal opening increases from 5% to 30%. When the actual motor speed is 1000 rpm, the torque attenuation coefficient always remains 100 (no attenuation) regardless of the change of the brake pedal opening (5%-30%).

[0084] When the vehicle is running in R gear, the motor actual output torque attenuation coefficient is related to the motor actual speed and the brake pedal opening degree, the motor actual speed and the brake pedal opening degree when in R gear are obtained, the motor actual output torque attenuation coefficient is obtained through the second relationship matching table obtained in advance, in the second relationship table, when the brake pedal opening degree is 0%, no matter the motor actual speed is (from -1000 rpm to 1000 rpm), the motor actual output torque attenuation coefficient is 100 (i.e. no attenuation).

[0085] With the gradual increase of the brake pedal opening degree from 5% to 30%, in different motor actual speed intervals, the torque attenuation coefficient presents different change rules: when the motor actual speed is -1000 rpm, no matter how the brake pedal opening degree changes (5%-30%), the torque attenuation coefficient always remains 100 (no attenuation). When the motor actual speed is -500 rpm, the brake pedal opening degree increases from 5% to 30%, the torque attenuation coefficient decreases from 100 to 80, 70, 70, 60, 50, 50 in turn. When the motor actual speed is -300 rpm, the brake pedal opening degree increases from 5% to 30%, the torque attenuation coefficient decreases from 100 to 70, 60, 60, 50, 40, 30 in turn. When the motor actual speed is -200 rpm, the brake pedal opening degree increases from 5% to 30%, the torque attenuation coefficient decreases from 100 to 40, 30, 30, 20, 20, 20 in turn. When the motor actual speed is -100 rpm, no matter how the brake pedal opening degree changes (5%-30%), the torque attenuation coefficient is 0 (complete attenuation).

[0086] When the motor actual speed is 0 rpm, no matter how the brake pedal opening degree changes (5%-30%), the torque attenuation coefficient is 0 (complete attenuation). When the motor actual speed is 100 rpm, the brake pedal opening degree increases from 5% to 30%, the torque attenuation coefficient decreases from 100 to 20, 10, 10, 10, 0, 0 in turn. When the motor actual speed is 200 rpm, the brake pedal opening degree increases from 5% to 30%, the torque attenuation coefficient decreases from 100 to 40, 30, 30, 20, 20, 10 in turn. When the motor actual speed is 300 rpm, the brake pedal opening degree increases from 5% to 30%, the torque attenuation coefficient decreases from 100 to 80, 70, 60, 50, 50, 50 in turn. When the motor actual speed is 500 rpm, no matter how the brake pedal opening degree changes (5%-30%), the torque attenuation coefficient always remains 100 (no attenuation). When the motor actual speed is 1000 rpm, no matter how the brake pedal opening degree changes (5%-30%), the torque attenuation coefficient always remains 100 (no attenuation).

[0087] In the embodiment, when the current working condition is the acceleration scene working condition, the corresponding control parameter matching method comprises: when the vehicle is driven in D gear, the motor target speed linearly increases with the accelerator pedal opening degree, the target speed is 300 rpm when the accelerator pedal opening degree is 0%, and the target speed is 1200 rpm when the accelerator pedal opening degree is 90%; when the vehicle is driven in R gear, the motor target speed linearly decreases with the accelerator pedal opening degree, the target speed is -300 rpm when the accelerator pedal opening degree is 0%, and the target speed is -1200 rpm. When the current working condition is the acceleration scene working condition, the corresponding control parameter matching method further comprises: the motor peak torque linearly increases with the accelerator pedal opening degree, the peak torque is 200 Nm when the accelerator pedal opening degree is 0%, and the peak torque is 340 Nm when the accelerator pedal opening degree is 90%, and the relationship table of the motor peak torque and the accelerator pedal opening degree is shown in Table 3.

[0088] Table 3 Relationship table of motor peak torque and accelerator pedal opening degree

[0089]

[0090] S400. The motor control unit adjusts the motor speed and torque according to the speed control mode switching instruction and the control parameters to ensure speed synchronization.

[0091] Specifically, after the MCU receives the speed control mode switching instruction issued by the vehicle control unit (VCU), the core information is first extracted. The control parameters include the target speed mode (such as the constant speed mode corresponding to low-speed four-wheel drive), the front and rear motor target speed values, the upper limit of the speed adjustment rate, and the torque distribution ratio. At the same time, the integrity and validity of the instruction are checked. If the parameters exceed the safety range preset by the MCU, an abnormal signal will be fed back to the VCU immediately, and the instruction will be corrected.

[0092] The MCU precisely controls the front and rear motors. First, according to the target speed and the current motor actual speed, the speed deviation value is calculated, and the basic torque instruction is generated through the PID control algorithm. For example, when the current speed is lower than the target value, a positive torque instruction is output to increase the speed; when the current speed is higher than the target value, the speed is reduced through regenerative braking torque or by reducing the output torque. Combined with the torque distribution ratio set by the VCU, the front and rear motor torques are dynamically distributed. If the front and rear axles need to output the same torque, the MCU will ensure that the torque response rates of the two sides are consistent; if the distribution ratio is adjusted according to the road conditions, the speed response rhythm will also be calibrated synchronously to avoid speed out-of-step caused by torque differences. In view of the differences in motor characteristics (such as different efficiencies and response speeds of the front and rear motors), the MCU will call the preset compensation algorithm. For example, preloaded torque is applied to the motor that responds more slowly, or the speed adjustment coefficient is adjusted to ensure that the speed changes of the two motors are synchronized.

[0093] MCU real-time acquisition of the speed signal before and after the motor (sampling frequency usually reaches 100Hz or more), continuous comparison of the speed difference between the two. When the difference exceeds the preset threshold (such as ±5rpm), immediately adjust the torque command, quickly correct the deviation, form a closed loop control. If the speed synchronization fails (such as the difference exceeds the threshold, motor fault alarm), MCU will first feedback the fault information to VCU, at the same time reduce the motor output torque or suspend mode switching, avoid damage to the transmission system, and prompt the driver through the instrument.

[0094] In order to better understand the implementation, the method is applied to the conventional off-road working condition as an example, the specific method includes:

[0095] The driver triggers the low-speed four-wheel drive mode through the central control screen HMI in the off-road condition, and the instrument displays "low-speed four-wheel drive activated";

[0096] The vehicle enters the idle speed scene, VCU sets the target speed a=300rpm, and the front and rear motors maintain 300rpm speed, and the vehicle slowly drives;

[0097] When encountering steep slope braking deceleration, the driver steps on the brake pedal, IBC collects the opening signal (such as 10%) and sends it to VCU;

[0098] VCU judges to enter the braking scene, according to the D-gear control logic, matches the target speed 200rpm and the corresponding torque attenuation coefficient, and sends it to MCU;

[0099] MCU adjusts the motor speed to 200rpm, and reduces the torque output according to the attenuation coefficient, and the vehicle slows down smoothly;

[0100] When climbing needs to accelerate, the driver steps on the accelerator pedal (such as 60% opening), VCU judges to enter the acceleration scene, matches the target speed 900rpm and peak torque 320Nm;

[0101] The front and rear motors accelerate according to the target speed, and the torque output reaches 320Nm, and the vehicle obtains sufficient off-road power and smoothly climbs the slope;

[0102] After off-road, the driver exits the low-speed four-wheel drive mode through HMI, and the system returns to normal driving control.

[0103] The method disclosed in the embodiment adopts a rotating speed synchronization mechanism, and the VCU sends a unified target rotating speed instruction to the front and rear MCUs, the MCUs adjust the motor output through a closed-loop control algorithm, the rotating speed deviation of the front and rear motors is controlled within ±5rpm, and the vehicle deviation is avoided; the MCUs adopt a rotating speed closed-loop control strategy, the torque output is dynamically adjusted according to the difference between the actual rotating speed and the target rotating speed, rather than directly responding to the accelerator pedal opening, and the stable power output is ensured; all the control parameters (target rotating speed, torque attenuation coefficient, peak torque) in the embodiment can be modified through a calibration tool, and can be personalized adapted according to the motor characteristics, vehicle body weight and off-road demand of different vehicle models; when the rotating speed deviation of the motor exceeds a threshold value, the brake signal is abnormal or the accelerator pedal is misoperated, the VCU automatically limits the torque output or exits the low-speed four-wheel drive mode, and the driving safety is ensured.

[0104] The embodiment discloses a control method of virtual low-speed four-wheel drive of an electric off-road four-wheel drive vehicle, and relates to the technical field of electric vehicle control. The method does not need to rely on a traditional transfer case structure, coordinates a motor control unit (MCU), an integrated brake controller (IBC) and other core components through a vehicle control unit (VCU), and realizes the virtual low-speed four-wheel drive function. After entering the low-speed four-wheel drive mode, the VCU controls the front and rear motors to switch to the rotating speed control mode, associates the motor target rotating speed, the torque attenuation coefficient and the peak torque with the pedal opening according to three scenes of idling, braking and accelerating, and realizes the stable control of the power output through accurate parameter calibration. The method solves the technical problems of high cost and complex vehicle arrangement of the traditional low-speed four-wheel drive system, simplifies the vehicle structure while ensuring the off-road power performance, reduces the manufacturing cost, and improves the driving operation convenience.

[0105] Based on the same inventive concept, the embodiment of the present application also provides a control system of virtual low-speed four-wheel drive of an electric off-road vehicle. Figure 2 The control system comprises a rotating speed control mode switching module, a brake pedal opening signal acquisition module, a control parameter matching module and a rotating speed synchronization module.

[0106] The rotating speed control mode switching module is used for sending a low-speed four-wheel drive mode request to the vehicle control unit through a human-computer interaction interface.

[0107] The brake pedal opening signal acquisition module is used for acquiring the brake pedal opening signal through the integrated brake controller and transmitting the brake pedal opening signal to the vehicle control unit through a CAN bus.

[0108] The control parameter matching module is configured to acquire a throttle pedal opening degree signal through a vehicle control unit, and determine a current working condition in combination with a brake pedal opening degree signal; the vehicle control unit matches a corresponding control parameter according to the current working condition, and sends the control parameter to the motor control unit;

[0109] The rotating speed synchronization module is configured to adjust the rotating speed and torque of the front motor and the rear motor according to the rotating speed control mode switching instruction and the control parameter through the motor control unit, so as to ensure the rotating speed synchronization.

[0110] Based on the same inventive concept, the embodiment of the present application also provides an electronic device. Figure 3 As shown in FIG. 1, the embodiment of the present application provides an electronic device including one or more processors 101, a memory 102, and one or more I / O interfaces 103. Figure 3 The memory 102 stores one or more programs, and when the one or more programs are executed by the one or more processors, the one or more processors implement the control method in any of the above embodiments; the one or more I / O interfaces 103 are connected between the processor and the memory, and are configured to realize the information interaction between the processor and the memory.

[0111] The processor 101 is a device with data processing capability, including but not limited to a central processing unit (CPU) and the like; the memory 102 is a device with data storage capability, including but not limited to a random access memory (RAM, more specifically SDRAM, DDR, etc.), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), and a flash memory (FLASH); the I / O interface (read-write interface) 103 is connected between the processor 101 and the memory 102, and can realize the information interaction between the processor 101 and the memory 102, including but not limited to a data bus (Bus) and the like.

[0112] In some embodiments, the processor 101, the memory 102, and the I / O interface 103 are connected to each other through a bus 104, and further connected to other components of the computing device.

[0113] In some embodiments, the one or more processors 101 include a field programmable gate array.

[0114] The embodiment of the present application also provides a computer readable medium. The computer readable medium stores a computer program, and when the program is executed by a processor, the steps in any of the control methods in the above embodiments are implemented. The computer readable storage medium can be a volatile or non-volatile computer readable storage medium.

[0115] The embodiment of the present application also provides a computer program product, comprising computer readable code or a nonvolatile computer readable storage medium carrying computer readable code, when the computer readable code is run in a processor of an electronic device, the processor in the electronic device performs the control method.

[0116] Those of ordinary skill in the art will understand that all or some of the steps in the above disclosed method, the functions of the modules / units in the system and the device can be implemented as software, firmware, hardware, or a suitable combination thereof. In a hardware implementation, the division between the functional modules / units referred to in the above description does not necessarily correspond to the division of physical components; for example, one physical component can have multiple functions, or one function or step can be performed by several physical components in cooperation. Some or all of the physical components can be implemented as software executed by a processor, such as a central processing unit, a digital signal processor, or a microprocessor, or as hardware, or as an integrated circuit, such as an application specific integrated circuit. Such software can be distributed on computer readable storage media, which can include computer storage media (or non-transitory media) and communication media (or transitory media).

[0117] As is well known to those of ordinary skill in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable program instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, random access memory (RAM), read only memory (ROM), erasable programmable read only memory (EPROM), static random access memory (SRAM), flash memory or other memory technology, portable compact disc read only memory (CD-ROM), digital versatile disc (DVD) or other optical disk storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and that can be accessed by a computer. Furthermore, it is well known to those of ordinary skill in the art that communication media typically embodies computer readable program instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and can include any information delivery media. The term "modulated data signal" means a signal that has one or more of its characteristics changed or set in a predetermined manner, such as amplitude, frequency or phase, to encode a form of information in the signal. The term "dual-tone multi-frequency signaling" or "DTMF" refers to a telecommunication signaling system in which tones of two specific frequencies are used to represent specific digits. The term "touch tone" refers to a tone of a specific frequency that is used to represent a specific digit in a DTMF system.

[0118] The computer readable program instructions described herein can be downloaded to respective computing / processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and / or a wireless network. The network can comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and / or edge servers. A network adapter card or network interface in each computing / processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing / processing device.

[0119] Computer readable program instructions for carrying out operations of the present application can be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The computer readable program instructions can execute entirely on the user's computing / processing device, partly on the user's computing / processing device, as a stand-alone software package, partly on the user's computing / processing device and partly on a remote computing / processing device or entirely on the remote computing / processing device or server. In the latter scenario, the remote computing / processing device can be connected to the user's computing / processing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computing / processing device, for example, through the Internet using an Internet Service Provider. In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate array (FPGA), or programmable logic array (PLA) can execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present application.

[0120] The computer program product described herein can be embodied specifically by hardware, software or a combination thereof. In an alternative embodiment, the computer program product is embodied specifically as a computer storage medium, and in another alternative embodiment, the computer program product is embodied specifically as a software product, such as a software development kit (SDK) or the like.

[0121] The computer program product described herein can be embodied specifically by hardware, software or a combination thereof. In an alternative embodiment, the computer program product is embodied specifically as a computer storage medium, and in another alternative embodiment, the computer program product is embodied specifically as a software product, such as a software development kit (SDK) or the like.

[0122] These computer readable program instructions can be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks. These computer readable program instructions can also be stored in a computer readable storage medium that can include a non-transitory computer readable storage medium that can be a computer- readable storage medium having no data storage cycles that change state. The instructions can be executed by one or more processors of a computer, other programmable data processing apparatus, or other devices to produce a computer-implemented process such that the instructions which execute via the one or more processors of the computer or other programmable data processing devices create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks. The computer program instructions can also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0123] The computer readable program instructions can also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0124] The flow diagrams and the block diagrams in the drawings are presented to illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to the present application. In this regard, each block in the flow diagrams and the block diagrams can represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical functions ("instructions"). In some alternative implementations, the functions noted in the blocks can occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks can sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and / or flow diagrams, and combinations thereof, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and

[0125] Example embodiments have been disclosed herein and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation. In some instances, it will be apparent to those skilled in the art that features, characteristics or aspects described in relation to one embodiment can be applied to other embodiments, unless otherwise clearly stated. It will also be apparent to one skilled in the art that various modifications, changes, additions and omissions can be made without departing from the scope of the present application as defined by the claims.

Claims

1. A control method of virtual low-speed four-wheel drive of an electric off-road vehicle, characterized by, The method comprises the following steps: sending a low-speed four-wheel drive mode request to the vehicle control unit through the human-computer interaction interface, and sending a rotating speed control mode switching instruction to the motor control unit after the vehicle control unit receives the request; the integrated brake controller collects the brake pedal opening degree signal and transmits it to the vehicle control unit through the CAN bus; the vehicle control unit collects the accelerator pedal opening degree signal and judges the current working condition in combination with the brake pedal opening degree signal; the vehicle control unit matches the corresponding control parameters according to the current working condition and sends the control parameters to the motor control unit; the motor control unit adjusts the rotating speed and torque of the front and rear motors according to the rotating speed control mode switching instruction and the control parameters to ensure the rotating speed synchronization.

2. The control method according to claim 1, characterized by, The current working condition is judged in combination with the brake pedal opening degree signal, and the current working condition includes an idle scene working condition, a braking scene working condition and an accelerating scene working condition.

3. The control method according to claim 1, characterized by, The vehicle control unit matches the corresponding control parameters according to the current working condition, and the control parameters include a motor target rotating speed, a motor actual output torque attenuation coefficient and a motor peak torque, and all the control parameters can be calibrated.

4. The control method according to claim 2, characterized by, When the current working condition is the idle scene working condition, the vehicle control unit matches the corresponding control parameters, and the target rotating speeds of the front and rear motors in the scene are set as a fixed value a, and a is a calibratable parameter.

5. The control method according to claim 2, characterized by, When the current working condition is the braking scene working condition, the vehicle control unit matches the corresponding control parameters, and the corresponding control parameter matching method includes: when the vehicle is running in D mode, the motor target rotating speed linearly decreases with the increase of the brake pedal opening degree, the target rotating speed is 300 rpm when the brake pedal opening degree is 0%, and the target rotating speed is 0 rpm when the brake pedal opening degree is 30%; when the vehicle is running in R mode, the motor target rotating speed linearly increases with the increase of the brake pedal opening degree, the target rotating speed is -300 rpm when the brake pedal opening degree is 0%, and the target rotating speed is 0 rpm when the brake pedal opening degree is 30%.

6. The control method according to claim 2, characterized by When the current working condition is the braking scene working condition, the vehicle control unit matches the corresponding control parameters, and the corresponding control parameter matching method further includes: When the vehicle is running in D mode, the motor actual output torque attenuation coefficient is related to the motor actual rotating speed and the brake pedal opening degree, the motor actual rotating speed and the brake pedal opening degree in D mode are obtained, and the motor actual output torque attenuation coefficient is matched by a first relationship table obtained in advance; When the vehicle is running in R mode, the motor actual output torque attenuation coefficient is related to the motor actual rotating speed and the brake pedal opening degree, the motor actual rotating speed and the brake pedal opening degree in R mode are obtained, and the motor actual output torque attenuation coefficient is matched by a second relationship table obtained in advance.

7. The control method according to claim 2, characterized by, When the current working condition is the accelerating scene working condition, the vehicle control unit matches the corresponding control parameters, and the corresponding control parameter matching method includes: When the vehicle is running in D mode, the motor target rotating speed linearly increases with the increase of the accelerator pedal opening degree, the target rotating speed is 300 rpm when the accelerator pedal opening degree is 0%, and the target rotating speed is 1200 rpm when the accelerator pedal opening degree is 90%; When the vehicle is running in R mode, the motor target rotating speed linearly decreases with the increase of the accelerator pedal opening degree, the target rotating speed is -300 rpm when the accelerator pedal opening degree is 0%, and the target rotating speed is -1200 rpm when the accelerator pedal opening degree is 90%.

8. The control method according to claim 2, characterized by, The vehicle control unit matches corresponding control parameters according to the current working condition, and when the current working condition is an acceleration scene working condition, the corresponding control parameter matching method further comprises: The peak torque of the motor increases in steps with the increase of the accelerator pedal opening degree, and the peak torque is 200 Nm when the accelerator pedal opening degree is 0%, and the peak torque is 340 Nm when the accelerator pedal opening degree is 90%.

9. A control system for virtual low speed four wheel drive of an electrically powered off-road vehicle, characterised in that, The control method comprises the following steps: The speed control mode switching module, the brake pedal opening degree signal acquisition module, the control parameter matching module and the speed synchronization module; wherein: The speed control mode switching module is used for sending a low-speed four-wheel drive mode request to the vehicle control unit through a human-computer interaction interface, and the vehicle control unit sends a speed control mode switching instruction to the motor control unit after receiving the request; The brake pedal opening degree signal acquisition module is used for collecting the brake pedal opening degree signal through the integrated brake controller and transmitting the brake pedal opening degree signal to the vehicle control unit through the CAN bus; The control parameter matching module is used for collecting the accelerator pedal opening degree signal through the vehicle control unit, judging the current working condition in combination with the brake pedal opening degree signal, matching corresponding control parameters according to the current working condition by the vehicle control unit, and sending the control parameters to the motor control unit; The speed synchronization module is used for adjusting the front and rear motor speeds and torques according to the speed control mode switching instruction and the control parameters by the motor control unit, and ensuring the speed synchronization.

10. An electronic device, comprising: The control method comprises the following steps: One or more processors; Memory for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the control method as claimed in any one of claims 1 to 8.

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