Braking control method and device of electric vehicle and electric vehicle

Abstract

The present application relates to the technical field of electric vehicles, and in particular to a braking control method, device and electric vehicle for electric vehicles, wherein the method comprises: when the driver's auxiliary braking intention is identified, identifying the current state of the electric vehicle; judging whether the current state satisfies the auxiliary braking start condition, and if so, controlling the electric vehicle to enter a target auxiliary braking mode that matches the auxiliary braking intention; detecting the actual load of the electric vehicle, matching the correction value of the target auxiliary braking mode according to the actual load, calculating the optimal auxiliary braking torque of the target auxiliary braking mode according to the correction value, and controlling the drive motor to output the optimal auxiliary braking torque to assist the electric vehicle in braking. Thus, the problems in the related art that the auxiliary braking power is only matched according to the gear position, the optimal auxiliary braking force cannot be generated, the accuracy and economy of the braking control are poor, and the driving experience is not good are solved.

Description

Technical Field

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

[0002] At present, heavy-duty electric vehicles are usually equipped with auxiliary braking devices, which are used to assist braking to reduce the load on the vehicle brakes, ensure safe driving and increase the service life of the brakes.

[0003] In the related art, electric vehicles usually match auxiliary braking power according to the current gear position, and perform auxiliary braking according to the matched auxiliary braking power. However, the auxiliary braking power matched only according to the gear position in the related art is not the optimal auxiliary braking force for electric vehicles, resulting in poor accuracy and economy of braking control, and reducing driving experience.

[0004] Application Contents

[0005] The present application provides a braking control method and device for an electric vehicle and an electric vehicle to solve the problems in the related art that the auxiliary braking force is only matched according to the gear position, the optimal auxiliary braking force cannot be generated, the accuracy and economy of the braking control are poor, and the driving experience is not good.

[0006] The first aspect of the present application provides a braking control method for an electric vehicle, comprising the following steps: when the driver's auxiliary braking intention is identified, identifying the current state of the electric vehicle; judging whether the current state satisfies the auxiliary braking start-up condition, and if so, controlling the electric vehicle to enter a target auxiliary braking mode that matches the auxiliary braking intention; detecting the actual load of the electric vehicle, matching a correction value of the target auxiliary braking mode according to the actual load, calculating the optimal auxiliary braking torque of the target auxiliary braking mode according to the correction value, and controlling the drive motor to output the optimal auxiliary braking torque to assist the electric vehicle in braking.

[0007] Furthermore, when the target auxiliary braking mode is a multi-speed auxiliary braking mode, a correction value of the target auxiliary braking mode is matched according to the actual load, and an optimal auxiliary braking torque of the target auxiliary braking mode is calculated according to the correction value, including: calculating the first auxiliary braking torque of the multi-speed auxiliary braking mode according to the actual gear of the multi-speed auxiliary braking mode and the actual speed of the electric vehicle; matching the vehicle weight factor of the electric vehicle according to the load range in which the actual load is located, and correcting the first auxiliary braking torque using the vehicle weight factor; and taking the smaller value of the absolute value between the corrected first auxiliary braking torque and the maximum feedback torque of the drive motor as the optimal auxiliary braking torque.

[0008] Optionally, the load interval includes first to third load intervals, wherein the vehicle weight factor of the first load interval is greater than the vehicle weight factor of the second load interval, the vehicle weight factor of the second load interval is greater than the vehicle weight factor of the third load interval, the minimum value of the first load interval is greater than the maximum value of the second load interval, and the minimum value of the second load interval is greater than the maximum value of the third load interval.

[0009] Further, when the target auxiliary braking mode is the constant speed auxiliary braking mode, a correction value of the target auxiliary braking mode is matched according to the actual load, and an optimal auxiliary braking torque of the target auxiliary braking mode is calculated according to the correction value, including: calculating a speed difference between the target speed and the actual speed of the constant speed auxiliary braking mode; matching an actual speed compensation value of the electric vehicle according to the actual load; correcting the speed difference using the actual speed compensation value, and performing a closed-loop speed calculation on the corrected speed difference to obtain a second auxiliary braking torque; and taking the smaller of the absolute values ​​of the second auxiliary braking torque and the maximum feedback torque of the drive motor as the optimal auxiliary braking torque.

[0010] Optionally, matching the vehicle speed compensation value of the electric vehicle according to the actual load includes: matching the actual vehicle speed compensation value corresponding to the actual load using a load and vehicle speed compensation value relationship table, wherein the vehicle speed compensation value decreases as the load increases.

[0011] Furthermore, identifying the driver's auxiliary braking intention includes: when the gear switch of the auxiliary brake switch is in the on position corresponding to the multi-speed auxiliary braking mode, identifying the driver's auxiliary braking intention as a multi-speed auxiliary braking intention; when the gear switch of the auxiliary brake switch is in the on position corresponding to the constant speed auxiliary braking mode, identifying the driver's auxiliary braking intention as a constant speed auxiliary braking intention.

[0012] Further, the current state includes an accelerator pedal opening state, a brake pedal opening state, a handbrake position state, a gear state of a transmission controller, a speed state of the electric vehicle and a state of an anti-lock braking system, and judging whether the current state satisfies the auxiliary braking activation condition includes: if the current accelerator pedal opening is less than a first opening, the current brake pedal opening is less than a second opening, the current position of the handbrake is in an unpulled position, the current gear of the transmission controller is in a preset gear, the actual speed of the electric vehicle is greater than a preset speed and the anti-lock braking system is in an inactivated state, then it is determined that the current state satisfies the auxiliary braking activation condition.

[0013] A second aspect of the present application provides a braking control device for an electric vehicle, comprising: an identification module, for identifying the current state of the electric vehicle when the driver's auxiliary braking intention is identified; a judgment module, for judging whether the current state satisfies the auxiliary braking start-up condition, and if so, controlling the electric vehicle to enter a target auxiliary braking mode that matches the auxiliary braking intention; a braking module, for detecting the actual load of the electric vehicle, matching a correction value of the target auxiliary braking mode according to the actual load, calculating the optimal auxiliary braking torque of the target auxiliary braking mode according to the correction value, and controlling the drive motor to output the optimal auxiliary braking torque to assist the electric vehicle in braking.

[0014] Furthermore, when the target auxiliary braking mode is a multi-speed auxiliary braking mode, the braking module is specifically used to: calculate the first auxiliary braking torque of the multi-speed auxiliary braking mode according to the actual gear position of the multi-speed auxiliary braking mode and the actual speed of the electric vehicle; match the vehicle weight factor of the electric vehicle according to the load range of the actual load, and use the vehicle weight weight factor to correct the first auxiliary braking torque; and use the smaller absolute value between the corrected first auxiliary braking torque and the maximum feedback torque of the drive motor as the optimal auxiliary braking torque.

[0015] Furthermore, when the target auxiliary braking mode is the constant speed auxiliary braking mode, the braking module is specifically used to: calculate the speed difference between the target vehicle speed and the actual vehicle speed of the constant speed auxiliary braking mode; match the actual vehicle speed compensation value of the electric vehicle according to the actual load; use the actual vehicle speed compensation value to correct the speed difference, and perform a closed-loop speed calculation on the corrected speed difference to obtain a second auxiliary braking torque; and use the smaller absolute value between the second auxiliary braking torque and the maximum feedback torque of the drive motor as the optimal auxiliary braking torque.

[0016] A third aspect of the present application provides an electric vehicle, comprising the brake control device of the electric vehicle described in the above embodiment.

[0017] Therefore, this application has at least the following beneficial effects:

[0018] The auxiliary braking power of electric vehicles is adjusted according to the actual load to generate the best auxiliary braking force, effectively improve the accuracy and economy of braking control, reduce or even avoid the impact of load changes on the braking effect, effectively improve the stability of the vehicle during braking, and enhance the driving experience. This solves the technical problems in the related art that the auxiliary braking power is only matched according to the gear position, the optimal auxiliary braking force cannot be generated, the accuracy and economy of braking control are poor, and the driving experience is not good.

[0019] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0021] Figure 1 A schematic diagram of the structure of a brake control system for an electric vehicle provided according to an embodiment of the present application;

[0022] Figure 2 A schematic flow chart of a braking control method for an electric vehicle provided according to an embodiment of the present application;

[0023] Figure 3 A schematic flow chart of a braking control method for an electric vehicle provided according to an embodiment of the present application;

[0024] Figure 4 The present invention is a block diagram of a brake control device for an electric vehicle provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0025] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0026] At present, most heavy-duty vehicles are equipped with auxiliary braking devices to reduce the load of the service brakes, ensure safe driving and reduce energy consumption. Among them, heavy-duty pure electric vehicles use the characteristics of the drive motor and the power battery, and the auxiliary braking is mostly achieved by energy recovery, and the size of the auxiliary braking force varies according to the setting of the auxiliary braking gear. However, the related art only outputs the auxiliary braking force according to the gear position, which cannot meet the driver's need to maintain a stable speed under certain working conditions, such as going down a long slope; in addition, the load of heavy-duty vehicles varies a lot. If the size of the auxiliary braking force is adjusted only according to the gear position, it may cause a significant difference in driving feel when the load changes greatly.

[0027] It is precisely because the related art does not consider the need for multi-speed auxiliary braking and constant speed braking at the same time, and does not adjust the auxiliary braking force according to the change of vehicle load, which leads to problems such as poor vehicle stability and economy. To this end, the embodiment of the present application proposes a solution that considers the request of multi-speed auxiliary braking and constant speed braking at the same time, and adjusts the auxiliary power according to the change of vehicle load.

[0028] The following will describe the braking control method, device and vehicle of the electric vehicle of the embodiment of the present application with reference to the accompanying drawings. In view of the problem that the auxiliary braking power matched only by the gear position in the related technology mentioned in the background technology center cannot generate the optimal auxiliary braking force, the accuracy and economy of the braking control are poor, and the driving experience is not good, the present application provides a braking control method for an electric vehicle, in which the auxiliary braking power of the electric vehicle is adjusted according to the actual load to generate the optimal auxiliary braking force, effectively improve the accuracy and economy of the braking control, reduce or even avoid the influence of the load change on the braking effect, effectively improve the stability of the vehicle during braking, and improve the driving experience. As a result, the technical problems such as the inability to generate the optimal auxiliary braking force, the poor accuracy and economy of the braking control, and the poor driving experience in the related technology are solved.

[0029] Specifically, Figure 1 Schematic diagram of the structure of the brake control system of the electric vehicle in the embodiment of the present application.

[0030] like Figure 1 As shown, the system includes: a vehicle controller 1, an auxiliary brake switch 2, an accelerator pedal 3, a brake pedal 4, a handbrake 5, a slope sensor 6, a transmission controller 7, an anti-lock brake controller 8, a power battery management system 9 and a drive motor controller 10.

[0031] The vehicle controller 1 is used to receive the gear switch signal of the auxiliary brake switch 2, the pedal opening signal of the accelerator pedal 3, the pedal switch signal of the brake pedal 4, the position signal of the handbrake 5, the slope signal of the slope sensor 6, the gear signal of the gearbox controller 7, the vehicle speed signal and the anti-lock control activation signal of the anti-lock brake controller 8, etc., to determine whether the vehicle can enter the auxiliary braking driving mode, and distinguish whether to enter the multi-gear auxiliary braking or constant speed braking; at the same time, according to the maximum feedback power signal of the power battery management system 9, the maximum feedback torque and speed signal of the drive motor controller 10, the maximum torque that can be fed back by the vehicle is calculated, and the calculated target torque is sent to the CAN bus. The drive motor controller 10 receives the target torque and other information on the CAN bus and controls the torque of the drive motor to change accordingly.

[0032] Specifically, the functions of each component in the braking control system of an electric vehicle are as follows:

[0033] Vehicle controller 1: Receives auxiliary brake switch signal, accelerator pedal opening signal, brake pedal switch signal, handbrake position signal, slope signal of slope sensor, gear signal of transmission controller, vehicle speed signal and anti-lock control activation signal of anti-lock brake controller, maximum feedback power signal of power battery system, motor speed and maximum feedback torque signal of drive motor controller, determines driver's auxiliary brake related request, realizes auxiliary brake multi-gear torque control or constant speed control, outputs corresponding auxiliary brake torque, performs torque coordination processing, and sends the processed target torque to CAN bus.

[0034] Auxiliary brake switch 2: The driver's intention of auxiliary braking is reflected through the adjustment of the switch, and the switch signal is fed back to the vehicle controller.

[0035] Accelerator pedal 3: The driver's driving intention is reflected by the change of the accelerator pedal opening, and the pedal opening signal is fed back to the vehicle controller.

[0036] Brake pedal 4: The switch state of the brake pedal reflects the driver's need to brake the vehicle, and feeds back the brake switch signal to the vehicle controller.

[0037] Handbrake 5: The handbrake position signal reflects the driver's need to brake the vehicle, and the handbrake position signal is fed back to the vehicle controller.

[0038] Slope sensor 6: detects the slope information of the road surface and feeds back the slope signal to the vehicle controller.

[0039] Transmission controller 7: controls the automatic shifting of gears and sends the gear signal to the CAN bus.

[0040] Anti-lock brake controller 8: detects the wheel speed information of the vehicle, performs anti-lock brake control on the vehicle, and sends the calculated vehicle speed signal and anti-lock brake control activation signal to the CAN bus.

[0041] Power battery management system 9: Calculates the maximum feedback power according to the power battery charge state, temperature and other information, and sends the calculated result to the CAN bus.

[0042] The drive motor controller 10 receives information such as the target torque on the CAN bus, controls the torque change of the drive motor, calculates the maximum feedback torque, and sends the actual speed and maximum feedback torque of the drive motor to the CAN bus.

[0043] Figure 2 A schematic flow chart of a braking control method for an electric vehicle provided in an embodiment of the present application.

[0044] like Figure 2As shown, the braking control method of the electric vehicle comprises the following steps:

[0045] In step S101 , when the driver's intention of assisting braking is recognized, the current state of the electric vehicle is recognized.

[0046] Among them, the auxiliary braking intention may include multi-speed auxiliary braking intention and constant speed auxiliary braking intention; the current state may include the accelerator pedal opening state, the brake pedal opening state, the position state of the handbrake, the gear state of the transmission controller, the speed state of the electric vehicle and / or the state of the anti-lock braking system, etc.

[0047] In this embodiment, identifying the driver's auxiliary braking intention includes: when the gear switch of the auxiliary brake switch is in the on position corresponding to the multi-speed auxiliary braking mode, identifying the driver's auxiliary braking intention as a multi-speed auxiliary braking intention; when the gear switch of the auxiliary brake switch is in the on position corresponding to the constant speed auxiliary braking mode, identifying the driver's auxiliary braking intention as a constant speed auxiliary braking intention.

[0048] Among them, the opening positions corresponding to the multi-speed auxiliary braking mode may include multiple positions such as the I gear position and the II gear position.

[0049] It is understandable that the vehicle controller can determine the driver's specific auxiliary braking intention based on the operating state of the auxiliary braking switch for subsequent auxiliary braking control.

[0050] In step S102, it is determined whether the current state satisfies the auxiliary braking activation condition. If so, the electric vehicle is controlled to enter a target auxiliary braking mode that matches the auxiliary braking intention.

[0051] Among them, the target auxiliary braking mode may include a multi-speed auxiliary braking mode and a constant speed auxiliary braking mode. The target auxiliary braking mode may be determined by the auxiliary braking intention. For example, when the auxiliary braking intention is a multi-speed auxiliary braking intention, then when the auxiliary braking start-up conditions are met, the electric vehicle may be controlled to enter the multi-speed auxiliary braking mode; when the auxiliary braking intention is a constant speed auxiliary braking intention, then when the auxiliary braking start-up conditions are met, the electric vehicle may be controlled to enter the constant speed auxiliary braking mode.

[0052] It can be understood that the vehicle controller can determine whether the auxiliary braking start conditions are met based on the accelerator pedal opening signal, brake pedal switch signal, handbrake position signal, transmission controller gear signal, vehicle speed signal of the anti-lock braking controller and anti-lock activation signal. If not, the target torque for normal driving is output. If satisfied, the electric vehicle is controlled to enter the target auxiliary braking mode determined according to the auxiliary braking intention.

[0053] In this embodiment, if the current opening of the accelerator pedal is less than the first opening, the current opening of the brake pedal is less than the second opening, the current position of the handbrake is in the unpulled position, the current gear of the transmission controller is in the preset gear, the actual speed of the electric vehicle is greater than the preset speed and the anti-lock braking system is in an inactive state, then it is determined that the current state meets the auxiliary braking activation condition.

[0054] Among them, the first opening and the second opening can be set according to actual conditions without specific limitations. When the current opening of the accelerator pedal is less than the first opening, it means that the accelerator pedal is not triggered; when the current opening of the brake pedal is less than the second opening, it means that the brake pedal is not triggered.

[0055] Among them, the preset gear can be the forward gear (D gear).

[0056] Among them, the preset vehicle speed can be specifically calibrated, for example, it can be set to 8km / h or 10km / h.

[0057] It can be understood that when the vehicle controller detects that the accelerator pedal is not triggered, the brake pedal is not triggered, the gearbox is in D gear, the actual vehicle speed is greater than a certain value, and the anti-lock braking system is not activated, etc., it can be determined that the current state of the electric vehicle meets the auxiliary braking start-up conditions and the electric vehicle can be controlled to enter the auxiliary braking mode.

[0058] In step S103, the actual load of the electric vehicle is detected, a correction value of the target auxiliary braking mode is matched according to the actual load, an optimal auxiliary braking torque of the target auxiliary braking mode is calculated according to the correction value, and the drive motor is controlled to output the optimal auxiliary braking torque to assist the electric vehicle in braking.

[0059] It is understandable that the embodiments of the present application can take into account changes in vehicle load during auxiliary braking control of electric vehicles and make corresponding adjustments to the auxiliary braking force of the vehicle to reduce the difference in driving feel caused by load changes and improve the driving experience.

[0060] In this embodiment, when the target auxiliary braking mode is the multi-speed auxiliary braking mode, a correction value of the target auxiliary braking mode is matched according to the actual load, and the optimal auxiliary braking torque of the target auxiliary braking mode is calculated according to the correction value, including: calculating the first auxiliary braking torque of the multi-speed auxiliary braking mode according to the actual gear of the multi-speed auxiliary braking mode and the actual speed of the electric vehicle; matching the vehicle weight factor of the electric vehicle according to the load range in which the actual load is located, and correcting the first auxiliary braking torque using the vehicle weight factor; and taking the smaller value of the absolute value between the corrected first auxiliary braking torque and the maximum feedback torque of the drive motor as the optimal auxiliary braking torque.

[0061] Among them, the load interval includes first to third load intervals, wherein the vehicle weight weight factor of the first load interval is greater than the vehicle weight weight factor of the second load interval, the vehicle weight weight factor of the second load interval is greater than the vehicle weight weight factor of the third load interval, the minimum value of the first load interval is greater than the maximum value of the second load interval, and the minimum value of the second load interval is greater than the maximum value of the third load interval.

[0062] It should be noted that the load interval can be set according to the load of the electric vehicle without specific limitation. For example, the load of the electric vehicle can be divided into three levels: full load, half load, and no load. The first load interval can correspond to the full load level, the second load interval can correspond to the half load level, and the third load interval can correspond to the no load level.

[0063] The vehicle weight weight factor corresponding to different load intervals can be specifically calibrated or set. In specific applications, the value range of the vehicle weight weight factor can be 0-1, and the vehicle weight weight factor increases with the increase of load. The auxiliary braking force can be increased when the load increases to reduce the difference in driving feel caused by load changes. For example, the vehicle weight weight factor of a fully loaded vehicle can be set to 1 or 0.9, the vehicle weight weight factor of a half-loaded vehicle can be set to 0.5 or 0.6, and the vehicle weight weight factor of an unloaded vehicle can be set to 0.1 or 0.2.

[0064] Specifically, after the vehicle controller controls the electric vehicle to enter the multi-speed auxiliary braking control, it first calculates the first auxiliary braking torque according to the multi-speed auxiliary braking control gear signal and the vehicle speed signal sent by the anti-lock braking controller; then, considering the influence of different vehicle weights on the auxiliary braking torque, the corresponding vehicle weight weight factor is matched according to the actual load, and the product of the vehicle weight weight factor and the first auxiliary braking torque is calculated; finally, the product of the vehicle weight weight factor and the first auxiliary braking torque is compared with the maximum feedback torque of the drive motor, and the smaller absolute value after the comparison is output.

[0065] In this embodiment, the first auxiliary braking torque of the multi-speed auxiliary braking mode is calculated according to the actual gear position of the multi-speed auxiliary braking mode and the actual vehicle speed of the electric vehicle, including: searching the gear position-vehicle speed-assisted braking torque relationship table of the multi-speed auxiliary braking mode to determine the first auxiliary braking torque.

[0066] It is understandable that the embodiment of the present application can pre-set the gear position-vehicle speed-assist brake torque relationship, and then quickly determine the assist brake torque according to the actual gear position and the actual vehicle speed. The actual gear position may include gear I, gear II, etc., which is specifically determined according to the position of the auxiliary brake switch, and the larger the gear position, the larger the corresponding auxiliary brake torque.

[0067] In some embodiments, the vehicle controller can calculate the maximum regenerative torque available for the vehicle based on the maximum regenerative power sent by the power battery management system and the maximum regenerative torque of the motor sent by the drive motor controller, combined with the actual speed of the drive motor.

[0068] In this embodiment, when the target auxiliary braking mode is the constant speed auxiliary braking mode, a correction value of the target auxiliary braking mode is matched according to the actual load, and the optimal auxiliary braking torque of the target auxiliary braking mode is calculated according to the correction value, including: calculating the speed difference between the target speed and the actual speed of the constant speed auxiliary braking mode; matching the actual speed compensation value of the electric vehicle according to the actual load; correcting the speed difference using the actual speed compensation value, and performing a closed-loop speed calculation on the corrected speed difference to obtain a second auxiliary braking torque; and taking the smaller value of the absolute value between the second auxiliary braking torque and the maximum feedback torque of the drive motor as the optimal auxiliary braking torque.

[0069] Among them, the embodiment of the present application can use a vehicle speed closed-loop algorithm to calculate the auxiliary braking torque. The vehicle speed closed-loop algorithm can be selected according to actual conditions and is not specifically limited to this.

[0070] Specifically, when the vehicle controller performs constant speed auxiliary braking control, it first calculates the difference based on the target vehicle speed signal confirmed when the constant speed gear is pressed, and the actual vehicle speed feedback from the anti-lock brake controller, and calculates the vehicle speed compensation value based on the different vehicle weights to obtain the final vehicle speed difference; then the auxiliary braking torque is calculated through a speed closed loop, and finally compared with the maximum feedback torque, and the smaller absolute value after the comparison is output.

[0071] It should be noted that if the calculated absolute value of the auxiliary braking torque is less than the maximum feedback torque, that is, there is a possibility that the current target vehicle speed cannot be maintained, the driver can be reminded to adjust the target vehicle speed or step on the brake pedal through instruments or other means.

[0072] In this embodiment, matching the vehicle speed compensation value of the electric vehicle according to the actual load includes: matching the actual vehicle speed compensation value corresponding to the actual load using a load and vehicle speed compensation value relationship table.

[0073] Among them, the load and vehicle speed compensation value relationship table can be specifically calibrated or specifically set, and there is no specific limitation on this. The vehicle speed compensation value decreases as the load increases. The auxiliary braking force can be increased when the load increases to reduce the difference in driving feel caused by load changes.

[0074] In some embodiments, the vehicle controller may also coordinate the optimal auxiliary braking torque with the output torque in the normal driving mode and send it to the drive motor controller via the CAN bus.

[0075] According to the braking control method of the electric vehicle proposed in the embodiment of the present application, graded auxiliary braking and auxiliary braking at a constant vehicle speed can be realized, and the auxiliary braking power of the electric vehicle can be adjusted according to the actual load to generate the optimal auxiliary braking force, effectively improving the accuracy and economy of the braking control, reducing or even avoiding the impact of load changes on the braking effect, effectively improving the stability of the vehicle during braking, and improving the driving experience.

[0076] The braking control method of an electric vehicle will be described below through a specific embodiment. Figure 3 As shown, the following steps are included:

[0077] In step 201 , the vehicle controller determines whether the driver has an auxiliary brake on request based on the operating state of the auxiliary brake switch, and if so, executes step 202 .

[0078] In step 202, the vehicle controller calculates the maximum regenerative torque Tq available for the vehicle based on the maximum regenerative power sent by the power battery management system and the maximum regenerative torque of the motor sent by the drive motor controller, combined with the actual speed of the drive motor. gmax .

[0079] In step 203, the vehicle controller determines whether the auxiliary brake activation condition is met based on the accelerator pedal opening signal, the brake pedal switch signal, the handbrake position signal, the gear position signal of the transmission controller, the vehicle speed signal of the anti-lock brake controller and the anti-lock activation signal; if so, execute step 204, otherwise go to step 213.

[0080] In step 204 , the vehicle controller determines to enter the auxiliary braking driving mode.

[0081] In step 205 , the vehicle controller determines whether the signal sent by the auxiliary brake switch is a request for multiple gears such as gear I and gear II. If so, step 206 is executed; otherwise, the process proceeds to step 209 .

[0082] In step 206 , the vehicle controller calculates the auxiliary braking torque Tq1 according to different gear position signals of the auxiliary braking switch and the vehicle speed signal, wherein the larger the gear position, the larger the corresponding auxiliary braking torque.

[0083] In step 207, since different vehicle weights have different effects on the auxiliary braking torque, the vehicle controller can divide the calculated vehicle weight into three levels: full load, half load, and no load after calculating the vehicle weight, and calculate the corresponding vehicle weight factor, and correct the auxiliary braking torque Tq1 calculated in step 206 to obtain the final torque Tq2 under different auxiliary braking gears; wherein, as the vehicle weight increases, the auxiliary braking torque increases accordingly.

[0084] In step 208, the absolute values ​​of the auxiliary braking torque obtained in step 207 and the maximum feedback torque obtained in step 202 are compared, and the smaller absolute value after comparison between the two is output.

[0085] In step 209 , the vehicle controller determines whether the auxiliary brake switch is a constant speed gear request, and determines whether the constant speed control condition is met according to the slope signal. If so, step 210 is executed, otherwise step 213 is executed.

[0086] In step 210, the vehicle controller determines the target vehicle speed signal V according to the target vehicle speed signal V when the constant speed gear is pressed. t , and the actual vehicle speed V fed back by the anti-lock brake controller a The signal is used to calculate the difference, and the speed compensation value V is calculated according to the different vehicle weights. m .

[0087] In step 211, the vehicle controller calculates the vehicle speed difference ΔV=V t -V a -V m , the auxiliary braking torque is calculated through the vehicle speed closed loop to obtain the torque Tq3.

[0088] In step 212, the auxiliary braking torque obtained in step 211 is compared with the absolute value of the maximum feedback torque obtained in step 202, and the smaller absolute value after the comparison is output; at the same time, if the output is Tq gmax , it means that the calculated braking assist torque exceeds the current vehicle energy recovery capability and the target vehicle speed V cannot be maintained. t The possibility of driving requires the driver to be reminded through instruments or other means to adjust the target speed or step on the brake pedal.

[0089] In step 213 , the vehicle controller outputs a target torque for normal driving when the auxiliary brake is not activated.

[0090] In step 214, the vehicle controller coordinates the target torque outputted in steps 208, 212 and 213, and sends it to the drive motor controller via the CAN bus. The drive motor controller controls the torque output of the drive motor according to the target torque.

[0091] In summary, the embodiments of the present application can, without changing the configuration of the electric vehicle power system, realize the functions of graded auxiliary braking and constant speed auxiliary braking by energy recovery through the recognition of the driver's intention and the vehicle status when the driver has an auxiliary braking demand; at the same time, taking into account the influence of the vehicle weight load, the power output of the auxiliary braking is adjusted accordingly to reduce the difference in driving feel caused by load changes, thereby not only meeting the requirements of vehicle deceleration and stability, but also effectively reducing energy consumption, reducing the number of times the brake pedal is triggered, reducing wear, and improving the economy of the entire vehicle.

[0092] Next, the braking control device of the electric vehicle proposed in accordance with the embodiment of the present application is described with reference to the accompanying drawings.

[0093] Figure 4 It is a block diagram of a brake control device for an electric vehicle according to an embodiment of the present application.

[0094] like Figure 4 As shown, the brake control device 100 of the electric vehicle includes: an identification module 110 , a judgment module 120 and a brake module 130 .

[0095] Among them, the identification module 110 is used to identify the current state of the electric vehicle when the driver's auxiliary braking intention is identified; the judgment module 120 is used to judge whether the current state meets the auxiliary braking start-up conditions, and if so, control the electric vehicle to enter a target auxiliary braking mode that matches the auxiliary braking intention; the braking module 130 is used to detect the actual load of the electric vehicle, match the correction value of the target auxiliary braking mode according to the actual load, calculate the optimal auxiliary braking torque of the target auxiliary braking mode according to the correction value, and control the drive motor to output the optimal auxiliary braking torque to assist the electric vehicle in braking.

[0096] Furthermore, when the target auxiliary braking mode is the multi-speed auxiliary braking mode, the braking module 130 is specifically used to: calculate the first auxiliary braking torque of the multi-speed auxiliary braking mode according to the actual gear position of the multi-speed auxiliary braking mode and the actual speed of the electric vehicle; match the vehicle weight factor of the electric vehicle according to the load range of the actual load, and use the vehicle weight factor to correct the first auxiliary braking torque; and take the smaller absolute value between the corrected first auxiliary braking torque and the maximum feedback torque of the drive motor as the optimal auxiliary braking torque.

[0097] Furthermore, when the target auxiliary braking mode is the constant speed auxiliary braking mode, the braking module 130 is specifically used to: calculate the speed difference between the target vehicle speed of the constant speed auxiliary braking mode and the actual vehicle speed; match the actual vehicle speed compensation value of the electric vehicle according to the actual load; use the actual vehicle speed compensation value to correct the speed difference, and perform a closed-loop speed calculation on the corrected speed difference to obtain a second auxiliary braking torque; and use the smaller absolute value between the second auxiliary braking torque and the maximum feedback torque of the drive motor as the optimal auxiliary braking torque.

[0098] It should be noted that the above explanation of the embodiment of the braking control method of the electric vehicle is also applicable to the braking control device of the electric vehicle of this embodiment, which will not be repeated here.

[0099] According to the braking control device of the electric vehicle proposed in the embodiment of the present application, graded auxiliary braking and auxiliary braking at a constant vehicle speed can be realized, and the auxiliary braking power of the electric vehicle can be adjusted according to the actual load to generate the optimal auxiliary braking force, effectively improving the accuracy and economy of the braking control, reducing or even avoiding the influence of load changes on the braking effect, effectively improving the stability of the vehicle during braking, and improving the driving experience.

[0100] This embodiment also provides an electric vehicle, including the brake control device of the electric vehicle of the above embodiment. The vehicle can not only meet the requirements of vehicle deceleration and stability, but also reduce energy consumption and improve the economy of the whole vehicle.

[0101] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0102] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0103] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0104] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiment, the N steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0105] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

Claims

1. A braking control method for an electric vehicle, characterized in that: The following steps are involved: When the driver's intention of assisting braking is recognized, the current state of the electric vehicle is recognized; Determining whether the current state satisfies an auxiliary braking activation condition, and if so, controlling the electric vehicle to enter a target auxiliary braking mode that matches the auxiliary braking intention; Detecting the actual load of the electric vehicle, matching the correction value of the target auxiliary braking mode according to the actual load, calculating the optimal auxiliary braking torque of the target auxiliary braking mode according to the correction value, and controlling the drive motor to output the optimal auxiliary braking torque to assist the braking of the electric vehicle, wherein: When the target auxiliary braking mode is a multi-gear auxiliary braking mode, the first auxiliary braking torque of the multi-gear auxiliary braking mode is calculated according to the actual gear of the multi-gear auxiliary braking mode and the actual speed of the electric vehicle; the vehicle weight factor of the electric vehicle is matched according to the load interval where the actual load is located, and the first auxiliary braking torque is corrected by using the vehicle weight factor; the smaller value of the absolute value between the corrected first auxiliary braking torque and the maximum feedback torque of the drive motor is used as the optimal auxiliary braking torque; When the target auxiliary braking mode is the constant speed auxiliary braking mode, the speed difference between the target vehicle speed and the actual vehicle speed of the constant speed auxiliary braking mode is calculated; the actual vehicle speed compensation value of the electric vehicle is matched according to the actual load; the speed difference is corrected using the actual vehicle speed compensation value, and a closed-loop speed calculation is performed on the corrected speed difference to obtain a second auxiliary braking torque; the smaller value of the absolute value between the second auxiliary braking torque and the maximum feedback torque of the drive motor is used as the optimal auxiliary braking torque.

2. The method according to claim 1, characterized in that: The load interval includes first to third load intervals, wherein the vehicle weight factor of the first load interval is greater than the vehicle weight factor of the second load interval, the vehicle weight factor of the second load interval is greater than the vehicle weight factor of the third load interval, the minimum value of the first load interval is greater than the maximum value of the second load interval, and the minimum value of the second load interval is greater than the maximum value of the third load interval.

3. The method according to claim 1, characterized in that: The matching of the vehicle speed compensation value of the electric vehicle according to the actual load includes: The actual vehicle speed compensation value corresponding to the actual load is matched using a load-vehicle speed compensation value relationship table, wherein the vehicle speed compensation value decreases as the load increases.

4. The method according to claim 1, characterized in that Identify the driver's intention to assist braking, including: When the gear switch of the auxiliary brake switch is in an on position corresponding to the multi-gear auxiliary brake mode, identifying the driver's auxiliary braking intention as a multi-gear auxiliary braking intention; When the gear switch of the auxiliary brake switch is in an on position corresponding to the constant speed auxiliary brake mode, the auxiliary brake intention of the driver is identified as a constant speed auxiliary brake intention.

5. The method according to claim 1, characterized in that: The current state includes the accelerator pedal opening state, the brake pedal opening state, the handbrake position state, the gear state of the transmission controller, the speed state of the electric vehicle and the state of the anti-lock braking system. Determining whether the current state meets the auxiliary brake activation condition includes: If the current opening of the accelerator pedal is less than the first opening, the current opening of the brake pedal is less than the second opening, the current position of the handbrake is in the unpulled position, the current gear of the transmission controller is in the preset gear, the actual speed of the electric vehicle is greater than the preset speed and the anti-lock braking system is in an inactive state, it is determined that the current state meets the auxiliary braking activation condition.

6. A brake control device for an electric vehicle, characterized in that: include: An identification module, used for identifying a current state of the electric vehicle when an auxiliary braking intention of the driver is identified; A judging module, used for judging whether the current state satisfies the auxiliary braking activation condition, and if so, controlling the electric vehicle to enter a target auxiliary braking mode matching the auxiliary braking intention; A braking module, used for detecting an actual load of the electric vehicle, matching a correction value of the target auxiliary braking mode according to the actual load, calculating an optimal auxiliary braking torque of the target auxiliary braking mode according to the correction value, and controlling a drive motor to output the optimal auxiliary braking torque to assist braking of the electric vehicle; When the target auxiliary braking mode is a multi-gear auxiliary braking mode, the braking module is specifically used to: Calculating a first auxiliary braking torque of the multi-gear auxiliary braking mode according to an actual gear position of the multi-gear auxiliary braking mode and an actual vehicle speed of the electric vehicle; Matching a vehicle weight factor of the electric vehicle according to the load interval in which the actual load is located, and using the vehicle weight factor to correct the first auxiliary braking torque; The smaller absolute value between the corrected first auxiliary braking torque and the maximum feedback torque of the driving motor is used as the optimal auxiliary braking torque; When the target auxiliary braking mode is the constant speed auxiliary braking mode, the braking module is specifically used for: calculating a vehicle speed difference between a target vehicle speed and an actual vehicle speed in the constant speed auxiliary braking mode; Matching an actual speed compensation value of the electric vehicle according to the actual load; The vehicle speed difference is corrected by using the actual vehicle speed compensation value, and a vehicle speed closed-loop calculation is performed on the corrected vehicle speed difference to obtain a second auxiliary braking torque; The smaller absolute value between the second auxiliary braking torque and the maximum feedback torque of the driving motor is used as the optimal auxiliary braking torque.

7. An electric vehicle, characterized in that: The invention comprises a brake control device for an electric vehicle as claimed in claim 6.

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