A method and system for preventing a motor vehicle from rolling down a slope

Abstract

The application discloses an anti-slip control method and system for an electric vehicle, wherein the method comprises the following steps: based on the motor speed change rate, the scatter points in the preset hill-holding torque scatter diagram are fitted by the least square method to obtain a function relationship between the anti-slip torque and the motor speed change rate; according to the function relationship and the most recently collected speed change rate after entering the anti-slip mode, the anti-slip torque is obtained; according to the anti-slip torque and a preset first coefficient, a feedforward torque is generated; and based on the collected slope slope, the feedforward torque and the anti-slip torque are applied to or removed from the vehicle. Through the entering, exiting and re-entering conditions of the anti-slip mode, the application accurately applies and removes the anti-slip torque, and realizes the accurate control of the electric vehicle to complete hill-holding in various scenes.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of vehicle control, and particularly relates to an anti-slip control method and system for an electric vehicle. BACKGROUND

[0002] The anti-slip function refers to a function that, in the case of no human intervention, the vehicle is rear-slipped or front-slipped during normal driving, and the driving motor automatically generates torque to keep the vehicle stationary for a period of time. In order to realize this function, the driving motor needs to be switched between the normal mode and the anti-slip mode. When in the normal mode, the driving system is in the torque control state and responds to the torque request instruction issued by the vehicle controller; when in the anti-slip mode, the driving system is in the speed control state and targets at zero speed to automatically adjust the output torque for speed control.

[0003] The existing solution is to provide the anti-slip function by the driving motor, which provides a certain braking pressure for the electric vehicle for a period of time without increasing the hardware cost, so that the driver can move his foot to the accelerator pedal to control the vehicle. However, this solution has certain defects, for example, the ESC system of the vehicle is not considered in the entry condition, which will lead to the modification of the motor controller software when the vehicle is newly equipped with the ESC system, resulting in the increase of working time and cost; and in the anti-slip torque generation process, only the speed loop PI is used, which leads to a long torque adjustment time and a long rear-slipping distance of the vehicle, and the safety is poor. In addition, when the electric vehicle exits the anti-slip mode and the motor withdraws the torque, the system only uses a unified torque withdrawal slope without considering different working conditions, which causes the gear backlash and the gear rattle phenomenon, and affects the driving comfort of the vehicle. SUMMARY

[0004] The application provides an anti-slip control method and system for an electric vehicle, which accurately applies and withdraws the anti-slip torque by setting the entry, exit and re-entry conditions of the anti-slip mode, and accurately controls the electric vehicle to complete the hill holding in various scenes.

[0005] The first aspect of the application provides an anti-slip control method for an electric vehicle, which comprises:

[0006] Based on the motor speed change rate, the scatter points in the preset hill holding torque scatter plot are fitted by the least square method to obtain a functional relationship between the anti-slip torque and the motor speed change rate;

[0007] According to the functional relationship and the most recently collected speed change rate after entering the anti-slip mode, the anti-slip torque is obtained;

[0008] According to the anti-slip torque and a preset first coefficient, a feedforward torque is generated;

[0009] apply or remove the feedforward torque and the anti-slip torque to the vehicle based on the collected slope gradient.

[0010] The above scheme first collects the slope gradient of the slope where the electric vehicle is located and the running data of the current vehicle equipment, including the state data of the electric vehicle drive motor, the power battery, the brake pedal and the gear. Then the anti-slip torque and the feedforward torque are generated according to the speed of the drive motor and the slope gradient, respectively. The anti-slip torque can make the electric vehicle accurately complete the hill holding and will not appear the forward slip or backward slip, ensuring the safety of the electric vehicle driving. Considering that the drive motor may cause the backward slip distance to be too large due to the too long adjustment time, the feedforward torque is automatically applied or removed to the electric vehicle during hill holding, so as to minimize the backward slip distance and further improve the safety of the electric vehicle driving. Then, according to the entering condition, the exiting condition and the re-entering condition of the improved anti-slip mode, it is determined whether to apply or remove the torque to the electric vehicle through the state information, so that the electric vehicle can accurately complete the hill holding in various scenes without increasing the ESC system or other hardware and software, thereby reducing the cost and time of anti-slip control.

[0011] In a possible implementation method of the first aspect, the feedforward torque is generated according to the anti-slip torque and a preset first coefficient, specifically:

[0012] The anti-slip torque is multiplied by the first coefficient to obtain the feedforward torque; wherein the feedforward torque is less than the anti-slip torque.

[0013] In a possible implementation method of the first aspect, the feedforward torque and the anti-slip torque are applied or removed to the vehicle based on the collected slope gradient, specifically:

[0014] When the vehicle meets the preset entering condition of the anti-slip mode, the vehicle is controlled to enter the anti-slip mode from the normal mode, and the feedforward torque is first applied to the vehicle and then the anti-slip torque is applied to the vehicle at the slope gradient.

[0015] When the vehicle meets the preset exiting condition of the anti-slip mode, the vehicle is controlled to enter the normal mode from the anti-slip mode, and the feedforward torque is first removed from the vehicle and then the anti-slip torque is removed from the vehicle at the slope gradient.

[0016] When the vehicle meets the preset re-entering condition of the anti-slip mode and it is detected that the preset anti-slip time has been exceeded, the vehicle is allowed to enter the anti-slip mode.

[0017] In a possible implementation method of the first aspect, when the vehicle meets the preset entering condition of the anti-slip mode, specifically:

[0018] detecting whether the vehicle meets preset starting conditions, the starting conditions including that the drive system is fault-free, the brake pedal is not braked, the allowable charge-discharge power of the power battery is greater than a first threshold, the vehicle is not equipped with an ESC system, the current gear is set to D or R, and the absolute value of the rotational speed of the drive motor is within a first range;

[0019] If the vehicle meets all the starting conditions, it is determined that the vehicle meets the entering condition.

[0020] The above scheme sets perfect entering conditions for the electric vehicle entering the anti-slip mode, and links the hill-holding of the electric vehicle with the drive system, brake pedal, charge-discharge power of the power battery, whether the vehicle is equipped with an ESC system, gear state and motor speed, fully considers the influence of the external environment and the state of the electric vehicle, provides a guarantee for the safety of the vehicle, and makes the control of the electric vehicle more rigorous.

[0021] In a possible implementation method of the first aspect, when the vehicle meets preset exit conditions of the anti-slip mode, specifically:

[0022] detecting whether the vehicle meets preset termination conditions, the termination conditions including that the drive system has a fault, the brake pedal is braked, the allowable charge-discharge power of the power battery is less than or equal to the first threshold, the current gear is set to N, the difference between the requested torque and the anti-slip torque is greater than or equal to a second threshold, the requested torque and the anti-slip torque are opposite, and it is detected that a preset anti-slip time has been exceeded;

[0023] If the vehicle meets any of the termination conditions, it is determined that the vehicle meets the exit condition.

[0024] In a possible implementation method of the first aspect, when the vehicle meets preset re-entering conditions of the anti-slip mode, specifically:

[0025] detecting whether the vehicle meets preset re-starting conditions, the re-starting conditions including that the brake pedal is braked for a third threshold time, the current gear is set to N for a fourth time, and the motor speed of the drive motor is in the same direction as the gear for a fifth time;

[0026] If the vehicle meets any of the re-starting conditions, it is determined that the vehicle meets the re-entering condition.

[0027] In a possible implementation method of the first aspect, based on the collected slope slope, the feedforward torque and the anti-slip torque are applied to or removed from the vehicle, specifically:

[0028] Based on the current speed of the driving motor, the front feed torque is increased at a preset speed until the front feed torque is equal to the anti-slip slope torque, so as to apply or remove the anti-slip slope torque to the vehicle.

[0029] In a possible implementation method of the first aspect, the front feed torque is increased at a preset speed until the front feed torque is equal to the anti-slip slope torque, specifically:

[0030] According to the collected slope slope and the vehicle controller, the corresponding torque removal slope is determined;

[0031] The size of the speed is set according to the torque removal slope, and the application or removal of the front feed torque is controlled at the speed until the front feed torque is equal to the anti-slip slope torque.

[0032] In a possible implementation method of the first aspect, the method further comprises:

[0033] When the vehicle switches between the anti-slip slope mode and the normal mode, the torque removal slope changes according to the state of the vehicle controller.

[0034] The above scheme determines the reason for the electric vehicle to exit the anti-slip slope mode according to the state information when the torque is removed from the electric vehicle, and determines the corresponding torque removal slope according to different reasons, so that the anti-slip slope torque can be stably and slowly implemented, and a balance between response timeliness and vehicle comfort can be achieved, avoiding the occurrence of gear backlash and shaking caused by fast torque removal, which leads to vehicle jerk.

[0035] The second aspect of the present application provides an anti-slip slope control system for an electric vehicle, the system comprising: a function relationship construction module, an anti-slip slope torque generation module, a front feed torque generation module, and a torque execution module;

[0036] The function relationship construction module is configured to fit the scatter points in a preset stationary slope torque scatter plot based on the motor speed change rate by the least square method, to obtain a function relationship between the anti-slip slope torque and the motor speed change rate.

[0037] The anti-slip slope torque generation module is configured to obtain the anti-slip slope torque according to the function relationship and the most recently collected speed change rate after entering the anti-slip slope mode.

[0038] The front feed torque generation module is configured to generate the front feed torque according to the anti-slip slope torque and a preset first coefficient.

[0039] The torque execution module is configured to apply or remove the front feed torque and the anti-slip slope torque to the vehicle based on the collected slope slope. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the present application, the drawings required to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings described in the following embodiments are only some of the embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort based on these drawings.

[0041] Figure 1 is a specific flowchart of an electric vehicle anti-slip control method provided by an embodiment of the present application;

[0042] Figure 2 is a driving system mode switching diagram of an electric vehicle anti-slip control method provided by an embodiment of the present application;

[0043] Figure 3 is an anti-slip torque generation diagram of an electric vehicle anti-slip control method provided by an embodiment of the present application;

[0044] Figure 4 is an anti-slip torque application and removal diagram of an electric vehicle anti-slip control method provided by an embodiment of the present application;

[0045] Figure 5 is a specific structure diagram of an electric vehicle anti-slip control system provided by an embodiment of the present application. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort belong to the scope of protection of the present application.

[0047] It should be understood that the step numbers used herein are only for the convenience of description, and are not limited to the execution sequence of the steps.

[0048] First Embodiment

[0049] During driving, users are faced with various unexpected scenarios, which brings challenges to the safety and comfort of driving. For example, when the vehicle is on a slope, the driver moves his foot from the brake pedal to the accelerator pedal, and the vehicle will appear to slide backward due to gravity. This scenario is dangerous, so a certain torque needs to be applied to the vehicle to prevent the vehicle from sliding too far and colliding. However, how to accurately apply or remove the torque to the vehicle while ensuring the safety of the vehicle and not affecting the driving comfort is the main research direction of the embodiments of the present application.

[0050] AsFigure 1 As shown, Figure 1 A specific flowchart of an electric vehicle anti-slip control method is provided for an embodiment of the present application. The electric vehicle anti-slip control method of the embodiment includes steps S1 to S3, which are described in detail as follows:

[0051] In step S1, based on the motor speed change rate, the scatter points in the preset hill-holding torque scatter plot are fitted by the least square method to obtain a functional relationship between the anti-slip torque and the motor speed change rate.

[0052] In the embodiment of the present application, the anti-slip function of the electric vehicle refers to the function that, in the normal driving process of the vehicle, the vehicle is kept stationary for a period of time by the driving motor issuing torque without human intervention in the case of rear slipping or front slipping. To achieve this function, the driving motor needs to switch between the normal mode and the anti-slip mode. When in the normal mode, the driving system is in a torque control state and responds to the torque request instruction issued by the vehicle controller; when in the anti-slip mode, the driving system is in a speed control state, with zero speed as the target, and adjusts the output torque for speed control.

[0053] To better show how the vehicle switches between the anti-slip mode and the normal mode, Figure 2 A driving system mode switching diagram is provided. As shown, the left side is the vehicle in the normal mode, at this time the driving system of the electric vehicle is in a torque control state, responding to the torque request instruction issued by the vehicle controller, then controlling the speed of the driving motor through the motor controller, and then entering the anti-slip mode after meeting the entering condition or the re-entering condition; the right side is the vehicle in the anti-slip mode, at this time the driving system of the electric vehicle is in a speed control state, through determining the gear, the brake pedal, whether the ESC system is configured, the charge and discharge power of the power battery, and whether the torque request is received, to control the motor controller to adjust the speed of the driving motor and adjust the output torque for speed control.

[0054] To identify whether to enter the anti-slip mode, the slope slope of the slope where the electric vehicle is currently located and the state information of the electric vehicle need to be periodically collected within a period of time. The state information includes the operating data of the driving motor, the power battery, the brake pedal, and the gear of the electric vehicle.

[0055] Specifically, the state information includes whether the brake pedal has a stepping action, the duration of the stepping action, whether the driving system has a fault, the allowable charge and discharge power of the power battery, whether the electric vehicle is configured with an ESC system, which gear the gear is in, and the speed of the driving motor.

[0056] Because the whole vehicle hill-holding torque is positively correlated with the drive motor speed change rate when rolling down the slope, the greater the speed change rate, the greater the required hill-holding torque, so the current motor speed is first obtained to obtain the motor speed change rate. Then the hill-holding torque scatter plot is obtained.

[0057] Then, based on the current motor speed and the hill-holding torque scatter plot, the least squares method is used to fit the scatter points in the hill-holding torque scatter plot to obtain the functional relationship between the motor speed and the hill-holding torque. The latest speed change rate after the vehicle enters the anti-rolling mode is identified, and the anti-rolling torque is obtained through the functional relationship.

[0058] Step S2, according to the functional relationship and the latest speed change rate collected after entering the anti-rolling mode, the anti-rolling torque is obtained.

[0059] In the embodiment of the present application, the current drive motor speed is obtained, and the zero speed is taken as the target, and the anti-rolling torque is output through PI closed-loop regulation. However, only using speed closed-loop control may cause problems such as long regulation time and long rolling distance, and the safety is poor, so a feedforward torque is also needed to reduce the regulation time and the rolling distance.

[0060] Because the whole vehicle hill-holding torque is positively correlated with the drive motor speed change rate when rolling down the slope, the greater the speed change rate, the greater the required hill-holding torque, so the current motor speed is first obtained to obtain the motor speed change rate. Then the hill-holding torque scatter plot is obtained.

[0061] Then, based on the current motor speed and the hill-holding torque scatter plot, the least squares method is used to fit the scatter points in the hill-holding torque scatter plot to obtain the functional relationship between the motor speed and the hill-holding torque. The latest speed change rate after the vehicle enters the anti-rolling mode is identified, and the anti-rolling torque is obtained through the functional relationship.

[0062] Step S3, according to the anti-rolling torque and the preset first coefficient, the feedforward torque is generated.

[0063] In the embodiment of the present application, the anti-rolling torque is multiplied by the slope slope to obtain the feedforward torque, so as to compatible the error of hill-holding adjustment. Wherein, the slope slope is valued between 0-1.

[0064] Wherein, the hill-holding torque scatter plot is mainly used for analyzing the hill-holding performance of electric vehicles on slopes. By observing the scatter plot, the change of the torque output by the drive motor under different slope and different load conditions can be directly understood, so as to evaluate the hill-holding ability and stability of the vehicle.

[0065] Further, the feedforward torque is automatically provided to the whole vehicle by the driving motor for a certain time length to achieve the purpose of preventing hill rolling. The generation of the feedforward torque is simple and effective, and the function can be realized without high-power chips. The addition of the function greatly shortens the time of dynamic adjustment of the anti-hill rolling torque, reduces the distance of rear rolling, and improves the safety of driving.

[0066] In the embodiments of the present application, Figure 3 An anti-hill rolling torque generation graph is provided to illustrate how to generate the anti-hill rolling torque and the feedforward torque.

[0067] In step S4, the feedforward torque and the anti-hill rolling torque are applied or removed to the vehicle based on the collected slope slope.

[0068] In the embodiments of the present application, the entering condition, the exiting condition and the re-entering condition of the anti-hill rolling mode are formulated, which fully considers the influence of the external environment, and the generation, application and removal of the anti-hill rolling torque can be realized without adding additional devices such as ESC and slope sensor. Even if the vehicle is iteratively added with ESC configuration, the motor controller software does not need to be updated, which is economical and convenient, and at the same time, the charging and discharging power of the power battery is always concerned, which provides a guarantee for the safety of the power battery.

[0069] Further, according to the acquired state information, it is judged whether the electric vehicle can enter the anti-hill rolling mode using the entering condition. The entering condition is specifically:

[0070] 1) The driving system itself is fault-free and can operate normally;

[0071] 2) The brake pedal is not stepped on, indicating that the driver has no braking intention;

[0072] 3) The allowable charging and discharging power of the power battery is greater than a first threshold value; if this condition is not considered, there may be a dangerous situation that the torque generated by the driving system exceeds the bearing capacity of the power battery, causing an overcurrent fault of the power battery;

[0073] 4) The vehicle is not configured with an ESC system; this condition is to automatically close the hill holding function of the driving system when the vehicle is added with an ESC configuration in the future, so that the HHC slope auxiliary function is provided by the ESC to avoid the conflict between the two functions;

[0074] 5) The gear is in D or R; when the gear is in D, the driving motor is in negative speed, indicating that the vehicle is rear rolling; when the gear is in R, the driving motor is in positive speed, indicating that the vehicle is front rolling;

[0075] 6) The absolute value of the rotational speed of the driving motor is within a preset interval range; the lower limit of the interval range is set to prevent the driving system from being slightly disturbed by the gear gap, causing the anti-slip mode to be entered by mistake; the upper limit of the interval range is set to identify when the severity of the slip exceeds the hill-holding capability of the driving system, and the hill-holding is not entered; for example, the interval range set in the embodiment of the application is [20, 200].

[0076] When the state information meets all the above conditions, the driving system of the electric vehicle can enter the anti-slip mode from the normal mode.

[0077] In addition, according to the state information and the exit condition, it can be determined whether the electric vehicle is switched from the anti-slip mode to the normal mode. The exit condition is met specifically as follows:

[0078] 1) The driving system cannot operate normally, causing the driving motor to be unable to continue to provide torque;

[0079] 2) The brake pedal is depressed and lasts for a period of time; this condition indicates that the driver has a clear braking intention, rather than a mistake;

[0080] 3) The allowable charge-discharge power of the power battery is less than or equal to a first threshold value, at which time the power battery cannot provide sufficient energy for the driving battery to apply the anti-slip torque;

[0081] 4) The gear is switched to N;

[0082] 5) The difference between the requested torque of the vehicle controller and the anti-slip torque is greater than or equal to a second threshold value, for example, 2 m, indicating that the requested torque needs to be responded to at this time;

[0083] 6) The requested torque and the anti-slip torque are opposite;

[0084] 7) The preset anti-slip time has been exceeded. When the anti-slip function is triggered, the motor speed is zero, and the driving system outputs torque, which is a motor stall condition and can generate a large amount of heat. In order to protect the driving system, the anti-slip function is set to have a certain running time, which is less than the allowed stall time.

[0085] When the state information meets any of the above conditions, the driving system of the electric vehicle can enter the normal mode from the anti-slip mode.

[0086] When the anti-slip time is exceeded, the anti-slip function timing ends, and the driving system exits the anti-slip mode, it is determined whether the re-entry condition is met.

[0087] Further, continuously entering the anti-slip mode is equivalent to continuously being in the stall condition, which can cause the device to be seriously overheated and damaged. In order to avoid this problem, the re-entry condition of the anti-slip mode needs to be set.

[0088] Specifically, the re-entry condition is satisfied when:

[0089] 1) the brake pedal is depressed and lasts for a period of time;

[0090] 2) the gear of the vehicle is switched to N and lasts for a period of time;

[0091] 3) the rotational speed of the drive motor is in the same direction as the gear and lasts for a period of time.

[0092] When the state information satisfies any of the above conditions, the drive system of the electric vehicle sets the anti-slip mode permission flag, allowing the vehicle to re-enter the anti-slip mode.

[0093] Among the entry condition, the exit condition and the re-entry condition, the setting of the duration is affected by the motor controller hardware and the vehicle interaction signal period, which needs to be determined according to the actual hardware data of the vehicle.

[0094] When the normal mode is switched to the anti-slip mode, torque will be applied; when the anti-slip mode is switched to the normal mode, the torque will sometimes be directly removed, such as when the gear is changed to N. The application and removal of torque may cause jerk or shaking problems due to the existence of gear clearance in the drive system, resulting in poor user experience. Therefore, in the embodiments of the present application, a ramp processing is added when the torque is applied or removed, and the anti-slip torque is applied or removed to the vehicle using the ramp slope.

[0095] Specifically, when the anti-slip torque and the feedforward torque are applied to or removed from the electric vehicle, based on the current rotational speed of the drive motor, the PI closed loop is used to apply or remove the feedforward torque to the electric vehicle with the drive motor zero speed as the target, and then the feedforward torque is increased at a preset speed until it equals the anti-slip torque. At the same time, when the anti-slip torque and the feedforward torque are removed, the corresponding torque removal slope is determined according to the collected slope slope and the vehicle controller, and the speed is set according to the torque removal slope.

[0096] In addition, when the vehicle switches between the anti-slip mode and the normal mode, the torque removal slope changes according to the state of the vehicle controller.

[0097] Exemplarily, Figure 4Provided are the anti-slip torque application and withdrawal diagrams showing the process of applying torque to the vehicle from entering the anti-slip mode to withdrawing torque from exiting the anti-slip mode. As shown in the figure, at t1, the electric vehicle meets the entering condition, and the torque applied by the drive system is processed through slope K1 to avoid the jerk problem caused by the vertical application of torque. At t2, the anti-slip timing has not ended, and the vehicle state meets the remaining exit conditions. When the vehicle controller requests torque condition is met, the drive system responds to the vehicle controller request torque, and its slope follows the vehicle controller, i.e., K2 in the figure; when the brake pedal action exit condition is met, the drive system torque can be quickly withdrawn to reduce the stall condition and not be perceived by the user, i.e., according to the slope K3 to withdraw. When the remaining conditions such as gear switching to N are met, to avoid jerk, the torque should be withdrawn according to the slope K4, and the slope K4 is less than K3. At t3, the anti-slip function timing ends, and the drive system is withdrawn according to the slope K5. Since the user does not perform any action at this time, the slope K5 should be less than K4 to avoid the user's panic caused by too fast torque withdrawal.

[0098] The embodiments of the present application have the following beneficial effects:

[0099] The embodiments of the present application first collect the slope of the slope where the electric vehicle is located and the running state of the current vehicle equipment, including the state data of the electric vehicle drive motor, the power battery, the brake pedal and the gear. Then, the anti-slip torque and the feedforward torque are generated according to the speed of the drive motor and the slope, respectively, wherein the anti-slip torque can accurately complete the hill holding of the electric vehicle and will not appear the forward or backward rolling, and the safety of the electric vehicle driving is ensured; considering that the drive motor may cause the backward rolling distance to be too large due to the too long adjustment time, the feedforward torque is automatically applied or withdrawn to the electric vehicle during hill holding, so as to minimize the backward rolling distance and further improve the safety of the electric vehicle driving. Then, according to the entering condition, the exit condition and the re-entering condition of the improved anti-slip mode, whether to apply or withdraw torque to the electric vehicle is determined through the state information, so that the electric vehicle can accurately complete the hill holding in various scenes without increasing the ESC system or other hardware and software, thereby reducing the cost and time of anti-slip control.

[0100] Second embodiment

[0101] Further, in order to execute the electric vehicle anti-slip control system corresponding to the above-mentioned method embodiments, to realize the corresponding functions and technical effects, Figure 5 A structural diagram of an electric vehicle anti-slip control system is provided. For ease of illustration, only the part related to the present embodiment is shown, and the electric vehicle anti-slip control system provided by the embodiments of the present application comprises:

[0102] The function relationship construction module 201 is configured to obtain a function relationship between the anti-slippery slope torque and the motor speed change rate by fitting the scatter points in the preset scatter point graph of the hill-holding torque through the least square method based on the motor speed change rate.

[0103] In the embodiment of the present application, the anti-slippery slope function of the electric vehicle refers to a function that, in the process of normal driving of the vehicle, the vehicle is kept in a stationary state for a period of time by the driving motor automatically issuing a torque without human intervention when the vehicle is slipping backward or slipping forward. In order to realize this function, the driving motor needs to be switched between the normal mode and the anti-slippery slope mode. When in the normal mode, the driving system is in a torque control state and responds to the torque request instruction issued by the vehicle controller; when in the anti-slippery slope mode, the driving system is in a speed control state and takes zero speed as the target to automatically adjust the output torque for speed control.

[0104] In order to identify whether the anti-slippery slope mode is entered, the slope slope of the slope where the electric vehicle is currently located and the state information of the electric vehicle need to be periodically collected within a period of time. The state information includes the operating data of the driving motor, the power battery, the brake pedal, the gear of the electric vehicle, etc.

[0105] Specifically, the state information includes whether the brake pedal is stepped on, the duration of the stepping action, whether the driving system has a fault, the allowable charge and discharge power of the power battery, whether the electric vehicle is configured with an ESC system, which gear the gear is in, the speed of the driving motor, etc.

[0106] Because the vehicle hill-holding torque is positively correlated with the driving motor speed change rate when slipping, the greater the speed change rate, the greater the hill-holding torque required, so the current motor speed is first obtained to obtain the motor speed change rate. Then the hill-holding torque scatter point graph is obtained.

[0107] Then, based on the current motor speed and the hill-holding torque scatter point graph, the least square method is used to fit the scatter points in the hill-holding torque scatter point graph to obtain the function relationship between the motor speed and the hill-holding torque. The latest speed change rate after the vehicle enters the anti-slippery slope mode is identified, and the anti-slippery slope torque is obtained through the function relationship.

[0108] The anti-slippery slope torque generation module 202 is configured to obtain the anti-slippery slope torque according to the function relationship and the latest collected speed change rate after entering the anti-slippery slope mode.

[0109] In the embodiment of the present application, the speed of the current driving motor is obtained, and the anti-slippery slope torque is output through PI closed-loop adjustment with zero speed as the target. However, only using speed closed-loop control may cause problems such as long adjustment time and long slipping distance, and the safety is poor, so a feedforward torque needs to be added to reduce the adjustment time and the slipping distance.

[0110] Because the whole vehicle hill-holding torque is positively correlated with the drive motor speed change rate when hill-starting, the greater the speed change rate, the greater the required hill-holding torque, so the current motor speed is first obtained to get the motor speed change rate. Then the hill-holding torque scatter plot is obtained.

[0111] Then based on the current motor speed and the hill-holding torque scatter plot, the least square method is used to fit the scatter points in the hill-holding torque scatter plot to obtain the functional relationship between the motor speed and the hill-holding torque. Then the latest speed change rate after the vehicle enters the anti-hill-starting mode is identified, and the anti-hill-starting torque is obtained through the functional relationship.

[0112] The feedforward torque generation module 203 is configured to generate a feedforward torque according to the anti-hill-starting torque and a preset first coefficient.

[0113] In the embodiment of the present application, the anti-hill-starting torque is multiplied by the ramp slope to obtain the feedforward torque to accommodate the error of hill-holding adjustment. The ramp slope is between 0 and 1.

[0114] The hill-holding torque scatter plot is mainly used to analyze the hill-holding performance of the electric vehicle on the ramp. By observing the scatter plot, the change of the torque output by the drive motor under different slope and load conditions can be directly understood, so as to evaluate the hill-holding ability and stability of the vehicle.

[0115] Moreover, the feedforward torque is automatically provided to the whole vehicle by the drive motor for a certain time length to achieve the purpose of anti-hill-starting. The generation of the feedforward torque is simple and effective, and the function can be realized without high-performance chips. The addition of the function greatly shortens the time of dynamic adjustment of the anti-hill-starting torque, reduces the backward sliding distance, and improves the safety of driving.

[0116] The torque execution module 204 is configured to apply or remove the feedforward torque and the anti-hill-starting torque to the vehicle based on the collected ramp slope.

[0117] In the embodiment of the present application, when the vehicle meets the preset entering condition of the anti-hill-starting mode, the vehicle is controlled to enter the anti-hill-starting mode from the normal mode, and the feedforward torque is first applied to the vehicle and then the anti-hill-starting torque is applied to the vehicle at the ramp slope.

[0118] When the vehicle meets the preset exiting condition of the anti-hill-starting mode, the vehicle is controlled to enter the normal mode from the anti-hill-starting mode, and the feedforward torque is first removed from the vehicle and then the anti-hill-starting torque is removed from the vehicle at the ramp slope.

[0119] When the vehicle meets the preset re-entering condition of the anti-hill-starting mode and it is detected that the preset anti-hill-starting time has been exceeded, the vehicle is allowed to enter the anti-hill-starting mode.

[0120] In some embodiments, the torque execution module 204 further comprises:

[0121] In the embodiments of the present application, the entering condition, the exiting condition and the re-entering condition of the anti-slip mode are formulated, which fully considers the influence of the external environment, and the generation, application and removal of the anti-slip torque can be realized without adding additional devices such as ESC and slope sensor. Even if the ESC configuration is newly added to the whole vehicle, the motor controller software does not need to be updated, which is economical and convenient, and the charging and discharging power of the power battery is always monitored, which provides a guarantee for the safety of the power battery.

[0122] Further, according to the obtained state information, it is determined whether the electric vehicle can enter the anti-slip mode using the entering condition. The entering condition is specifically:

[0123] 1) The driving system itself is fault-free and can operate normally;

[0124] 2) The brake pedal is not stepped on, indicating that the driver has no braking intention;

[0125] 3) The allowable charging and discharging power of the power battery is greater than a first threshold value; if this condition is not considered, the torque generated by the driving system itself may exceed the bearing capacity of the power battery, causing the risk of overcurrent failure of the power battery;

[0126] 4) The vehicle is not configured with an ESC system; this condition is to automatically close the slope holding function of the driving system when the ESC configuration is added to the subsequent vehicle, so that the HHC slope auxiliary function is provided by the ESC to avoid the conflict between the two functions;

[0127] 5) The gear is in D or R; when the gear is in D, the driving motor has a negative speed, indicating that the vehicle is slipping backward; when the gear is in R, the driving motor has a positive speed, indicating that the vehicle is slipping forward;

[0128] 6) The absolute value of the speed of the driving motor is within a preset interval range; the lower limit of the interval range is set to prevent the slight fluctuation of the speed caused by the gear clearance of the driving system, which may cause the anti-slip state to be entered by mistake; the upper limit of the interval range is set to identify the situation that the severity of the slip exceeds the slope holding capability of the driving system, and the anti-slip mode is not entered; for example, the interval range set in the embodiments of the present application is [20, 200].

[0129] When the state information meets all the above conditions, the driving system of the electric vehicle can enter the anti-slip mode from the normal mode.

[0130] In addition, according to the state information and the exiting condition, it can be determined whether the electric vehicle is switched from the anti-slip mode to the normal mode. The exiting condition is specifically:

[0131] 1) the driving system cannot operate normally, resulting in the driving motor being unable to continue to provide torque;

[0132] 2) the brake pedal is depressed and maintained for a period of time; this condition indicates that the driver has a clear braking intention, rather than an accidental touch;

[0133] 3) the allowable charge-discharge power of the power battery is less than or equal to a first threshold value, at which time the power battery cannot provide sufficient energy for the driving battery to apply an anti-slip slope torque;

[0134] 4) the gear is switched to N;

[0135] 5) the difference between the requested torque of the vehicle controller and the anti-slip slope torque is greater than or equal to a second threshold value, for example, 2 m, indicating that the requested torque needs to be responded to at this time;

[0136] 6) the requested torque and the anti-slip slope torque are in opposite directions;

[0137] 7) a preset anti-slip slope time has been exceeded. When the anti-slip slope function is triggered, the motor speed is zero, and the driving system outputs torque, which is a motor stall condition and can generate a large amount of heat. To protect the driving system, the anti-slip slope function is set to a certain operating time, which is less than the stall allowable time.

[0138] When the state information meets any of the above conditions, the driving system of the electric vehicle can enter the normal mode from the anti-slip slope mode.

[0139] When the anti-slip slope time is exceeded, the anti-slip slope function timing ends, and the driving system exits the anti-slip slope mode, it is determined whether the re-entry condition is met.

[0140] Further, continuously entering the anti-slip slope mode is equivalent to continuously being in a stall condition, which can cause a serious temperature rise of the device and damage it. To avoid this problem, the re-entry condition of the anti-slip slope mode needs to be set.

[0141] Specifically, the re-entry condition is met when:

[0142] 1) the brake pedal is depressed and maintained for a period of time;

[0143] 2) the gear of the vehicle is switched to N and maintained for a period of time;

[0144] 3) the speed of the driving motor and the gear are in the same direction and are maintained for a period of time.

[0145] When the state information meets any of the above conditions, the anti-slip slope mode of the driving system of the electric vehicle is set to an allowable flag, which allows the vehicle to re-enter the anti-slip slope mode.

[0146] The setting of the duration in the entering condition, the exiting condition and the re-entering condition is affected by the motor controller hardware and the vehicle interaction signal cycle, and needs to be determined according to the actual hardware data of the vehicle.

[0147] When the normal mode is switched to the anti-slip mode, the torque is applied; when the anti-slip mode is switched to the normal mode, the torque is sometimes directly removed, such as when the gear is changed to the N gear. If the application and removal of the torque do not go through the slope processing, due to the gear clearance existing in the drive system, the jerk or the shaking problem may be caused, resulting in poor user experience. Therefore, in the embodiments of the present application, the slope processing is added when the torque is applied or removed, and the anti-slip torque is applied or removed to the vehicle using the slope slope.

[0148] Specifically, when the anti-slip torque and the feedforward torque are applied or removed to the electric vehicle, based on the current speed of the drive motor, the PI closed loop is used to apply or remove the feedforward torque to the electric vehicle first, and then the feedforward torque is increased at a preset speed until it is equal to the anti-slip torque. At the same time, when the anti-slip torque and the feedforward torque are removed, the corresponding torque removal slope is determined according to the state information, and the speed is set according to the torque removal slope.

[0149] The embodiments of the present application have the following beneficial effects:

[0150] The embodiments of the present application first collect the slope of the slope where the electric vehicle is located and the running state of the current vehicle equipment, including the state data of the electric vehicle drive motor, the power battery, the brake pedal and the gear. Then, the anti-slip torque and the feedforward torque are generated according to the speed of the drive motor and the slope, wherein the anti-slip torque can make the electric vehicle accurately complete the slope parking and will not appear the forward slip or backward slip, ensuring the safety of the electric vehicle driving; considering that the drive motor may cause the backward slip distance to be too large due to the too long adjustment time, the feedforward torque is automatically applied or removed to the electric vehicle during the slope parking, so as to minimize the backward slip distance and further improve the safety of the electric vehicle driving. Then, according to the entering condition, the exiting condition and the re-entering condition of the improved anti-slip mode, it is determined whether the torque is applied or removed to the electric vehicle through the state information, without adding the ESC system or other hardware and software, the electric vehicle can accurately complete the slope parking in various scenes, and the cost and time of the anti-slip control are reduced.

[0151] The above-described specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above-described specific embodiments are only for the specific embodiments of the present application and are not used to limit the protection scope of the present application. It is particularly pointed out that any modification, equivalent replacement, improvement, etc. made by those skilled in the art within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for controlling an electric vehicle from rolling down a slope, characterized by, The method comprises the following steps: Based on the motor speed change rate, the scatter points in the preset hill-hold torque scatter diagram are fitted by the least square method to obtain a function relationship between the anti-slip slope torque and the motor speed change rate; According to the function relationship and the latest collected speed change rate after entering the anti-slip slope mode, the anti-slip slope torque is obtained; According to the anti-slip slope torque and a preset first coefficient, a feedforward torque is generated; Based on the collected slope slope, the feedforward torque and the anti-slip slope torque are applied to or removed from the vehicle, specifically: when the vehicle meets the preset entering condition of the anti-slip slope mode, the vehicle is controlled to enter the anti-slip slope mode from the normal mode, and the feedforward torque is first applied to the vehicle and then the anti-slip slope torque is applied to the vehicle at the slope slope; when the vehicle meets the preset exit condition of the anti-slip slope mode, the vehicle is controlled to enter the normal mode from the anti-slip slope mode, and the feedforward torque is first removed from the vehicle and then the anti-slip slope torque is removed from the vehicle at the slope slope; when the vehicle meets the preset re-entry condition of the anti-slip slope mode and it is detected that the preset anti-slip slope time has been exceeded, the vehicle is allowed to enter the anti-slip slope mode; Wherein, when the vehicle meets the preset entering condition of the anti-slip slope mode, specifically: it is detected whether the vehicle meets the preset starting condition, the starting condition includes that the drive system is fault-free, the brake pedal is not braked, the allowable charge and discharge power of the power battery is greater than a first threshold value, the vehicle is not installed with an ESC system, the current gear is set to D or R, and the absolute value of the speed of the drive motor is within a first range; if the vehicle meets all the above starting conditions, it means that the vehicle meets the entering condition.

2. The electric vehicle anti-rollaway control method of claim 1, wherein The feedforward torque is generated according to the anti-slip slope torque and the preset first coefficient, specifically: The anti-slip slope torque is multiplied by the first coefficient to obtain the feedforward torque; wherein the feedforward torque is less than the anti-slip slope torque.

3. The electric vehicle anti-rollaway control method of claim 1, wherein, When the vehicle meets the preset exit condition of the anti-slip slope mode, specifically: It is detected whether the vehicle meets the preset termination condition, the termination condition includes that the drive system has a fault, the brake pedal is braked, the allowable charge and discharge power of the power battery is less than or equal to the first threshold value, the current gear is set to N, the difference between the request torque and the anti-slip slope torque is greater than or equal to a second threshold value, the request torque and the anti-slip slope torque are opposite, and it is detected that the preset anti-slip slope time has been exceeded; If the vehicle meets any of the termination conditions, it means that the vehicle meets the exit condition.

4. The electric vehicle anti-rollaway control method of claim 1, wherein When the vehicle meets the preset re-entry condition of the anti-slip slope mode, specifically: It is detected whether the vehicle meets the preset re-starting condition, the re-starting condition includes that the brake pedal is braked for a third threshold time, the current gear is set to N for a fourth time, and the motor speed of the drive motor is in the same direction as the gear for a fifth time; If the vehicle meets any of the above re-starting conditions, it means that the vehicle meets the re-entry condition.

5. The electric vehicle anti-rollaway control method of claim 1, wherein, Based on the collected slope slope, the feedforward torque and the anti-slip slope torque are applied to or removed from the vehicle, specifically: Based on the current speed of the driving motor, the front feed torque is applied or removed to the vehicle by PI closed loop with the zero speed of the driving motor as the target, and the front feed torque is increased at a preset speed until the front feed torque is equal to the anti-slip torque, so as to apply or remove the anti-slip torque to the vehicle.

6. The electric vehicle anti-rollaway control method of claim 5, wherein, The front feed torque is increased at a preset speed until the front feed torque is equal to the anti-slip torque, specifically: According to the collected slope slope and the vehicle controller, the corresponding torque removal slope is determined; The size of the speed is set according to the torque removal slope, and the application or removal of the front feed torque is controlled at the speed until the front feed torque is equal to the anti-slip torque.

7. The electric vehicle anti-rollaway control method of claim 6, wherein, Also includes: When the vehicle switches between the anti-slip mode and the normal mode, the torque removal slope changes according to the state of the vehicle controller.

8. An electric vehicle anti-rollaway control system characterized by comprising: Includes: Function relationship construction module, anti-slip torque generation module, front feed torque generation module and torque execution module; The function relationship construction module is used to fit the scatter points in the preset hill-hold torque scatter plot based on the motor speed change rate by the least square method to obtain the function relationship of the anti-slip torque and the motor speed change rate; The anti-slip torque generation module is used to obtain the anti-slip torque according to the function relationship and the most recently collected speed change rate after entering the anti-slip mode; The front feed torque generation module is used to generate the front feed torque according to the anti-slip torque and the preset first coefficient; The torque execution module is used to apply or remove the front feed torque and the anti-slip torque to the vehicle based on the collected slope slope, specifically: when the vehicle meets the preset entering condition of the anti-slip mode, the vehicle is controlled to enter the anti-slip mode from the normal mode, and the front feed torque is applied to the vehicle first and then the anti-slip torque is applied to the vehicle at the slope slope; when the vehicle meets the preset exit condition of the anti-slip mode, the vehicle is controlled to enter the normal mode from the anti-slip mode, and the front feed torque is removed from the vehicle first and then the anti-slip torque is removed from the vehicle at the slope slope; when the vehicle meets the preset re-entering condition of the anti-slip mode and it is detected that the preset anti-slip time has been exceeded, the vehicle is allowed to enter the anti-slip mode; When the vehicle meets the preset entering condition of the anti-slip mode, specifically: it is detected whether the vehicle meets the preset starting condition, the starting condition includes that the driving system is fault-free, the brake pedal is not braked, the allowable charge and discharge power of the power battery is greater than a first threshold value, the vehicle is not installed with an ESC system, the current gear is set to D or R, and the absolute value of the speed of the driving motor is within a first range; if the vehicle meets all the above starting conditions, it means that the vehicle meets the entering condition.

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