Slope sliding prevention control method and system for electric automobile

Abstract

The invention discloses an anti-slip control method and system for an electric vehicle, and the method comprises the steps: carrying out the fitting of scatter points in a preset hill-holding torque scatter diagram through a least square method based on the change rate of the rotating speed of a motor, and obtaining a function relation between the anti-slip torque and the change rate of the rotating speed of the motor; according to the function relation and the rotating speed change rate collected last time after entering the anti-slope-sliding mode, the anti-slope-sliding torque is obtained; according to the anti-slip torque and a preset first coefficient, feed-forward torque is generated; and applying or evacuating the feed-forward torque and the anti-slip torque to the vehicle based on the acquired slope gradient. According to the application, through the set entering, exiting and re-entering conditions of the anti-slope-sliding mode, the application and evacuation of the anti-slope-sliding torque are accurately carried out, and the electric vehicle is accurately controlled to complete slope parking in multiple scenes.

Description

Technical Field

[0001] The present application belongs to the field of vehicle control, and specifically relates to an anti-slope control method and system for an electric vehicle. Background Art

[0002] The anti-slope function refers to the function that when the vehicle slides backward or forward without human intervention during normal driving, the drive motor automatically generates torque to keep the vehicle stationary for a period of time. If the drive motor wants to achieve this function, it needs to switch between normal mode and anti-slope mode. When in normal mode, the drive system is in torque control state, responding to the torque request command issued by the vehicle controller; when in anti-slope mode, the drive system is in speed control state, with zero speed as the target, and automatically adjusts the output torque for speed control.

[0003] The existing solution is to provide the anti-slope function by the drive motor, so as to provide the electric vehicle with braking pressure for a certain 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 entry conditions do not consider whether the vehicle is equipped with the ESC system, which will cause the motor controller software to be modified when the ESC configuration is added to the subsequent vehicle, resulting in an increase in working time and working costs; and in the process of generating the anti-slope torque, it is only obtained through the speed loop PI, resulting in a long torque adjustment time, which makes the car slide back a long distance and poor safety. In addition, when the electric vehicle exits the anti-slope mode and allows the motor to de-twist, the system only uses a unified de-twist slope without considering the different working conditions, resulting in the phenomenon of tooth hitting and shaking caused by the gear gap, affecting the driving comfort of the whole vehicle. Summary of the invention

[0004] The present application proposes an anti-slope control method and system for an electric vehicle, which accurately applies and removes the anti-slope torque by setting the entry, exit and re-entry conditions of the anti-slope mode, thereby achieving accurate control of the electric vehicle to complete slope holding in a variety of scenarios.

[0005] A first aspect of the present application provides an electric vehicle anti-slope control method, the method comprising:

[0006] Based on the motor speed change rate, the scattered points in the preset slope-holding torque scatter diagram are fitted by the least squares method to obtain the functional relationship between the anti-slope torque and the motor speed change rate;

[0007] The anti-slope rolling torque is obtained according to the functional relationship and the speed change rate collected most recently after entering the anti-slope rolling mode;

[0008] Generate a feed-forward torque according to the anti-slope torque and a preset first coefficient;

[0009] Based on the acquired slope gradient, the feed-forward torque and the anti-slope torque are applied to or released from the vehicle.

[0010] The above scheme first collects the slope of the ramp where the electric vehicle is located and the operating data of the current vehicle equipment, including the status data of the electric vehicle drive motor, power battery, brake pedal and gear position. Then, the anti-slope torque and feedforward torque are generated respectively according to the speed of the drive motor and the slope slope. The anti-slope torque can enable the electric vehicle to accurately complete the slope without slipping forward or backward, ensuring the safety of the electric vehicle. Considering that the drive motor may cause a large backward slip distance due to a long adjustment time, the feedforward torque is automatically applied or withdrawn to the electric vehicle when the slope is parked, so as to reduce the backward slip distance as much as possible and further improve the safety of the electric vehicle. Then, according to the entry conditions, exit conditions and re-entry conditions of the perfect anti-slope mode, whether the torque is applied or withdrawn to the electric vehicle is determined by the state information. Without adding the ESC system or other hardware and software, the electric vehicle can be accurately controlled to complete the slope parking in a variety of scenarios, reducing the cost and time of anti-slope control.

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

[0012] The anti-slope torque is multiplied by the first coefficient to obtain the feed-forward torque; wherein the feed-forward torque is smaller than the anti-slope torque.

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

[0014] When the vehicle meets the preset entry conditions of the anti-slope mode, the vehicle is controlled to enter the anti-slope mode from the normal mode, and at the same time, the feed-forward torque is first applied to the vehicle at the slope slope and then the anti-slope torque is applied;

[0015] When the vehicle meets the preset exit condition of the anti-slope mode, the vehicle is controlled to enter the normal mode from the anti-slope mode, and at the same time, the feedforward torque is firstly released from the vehicle and then the anti-slope torque is released at the slope slope;

[0016] When the vehicle meets the preset re-entry conditions of the anti-slope rolling mode and it is detected that the preset anti-slope rolling time has been exceeded, the vehicle is allowed to enter the anti-slope rolling mode.

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

[0018] Detecting whether the vehicle meets preset start conditions, wherein the start conditions include that the drive system has no faults, the brake pedal is not applied, the allowable charge and 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 gear or R gear, and the absolute value of the speed of the drive motor is within a first range;

[0019] If the vehicle meets all of the above-mentioned starting conditions, it means that the vehicle meets the entry conditions.

[0020] The above scheme sets perfect entry conditions for electric vehicles to enter the anti-slope mode, and links the electric vehicle's slope holding ability with its own drive system, brake pedal, charging and discharging power of the power battery, whether the ESC system is installed, gear status and motor speed. It fully considers the impact of the external environment and the status of the electric vehicle itself, provides protection for the safety of the vehicle, and makes the control of electric vehicles more rigorous.

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

[0022] Detecting whether the vehicle meets a preset termination condition, wherein the termination condition includes a drive system failure, a brake pedal braking, an allowable charge and discharge power of the power battery being less than or equal to a first threshold, the current gear being set to gear N, a difference between the requested torque and the anti-slope torque being greater than or equal to a second threshold, the requested torque being opposite to the anti-slope torque, and detecting that a preset anti-slope time has been exceeded;

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

[0024] In a possible implementation method of the first aspect, when the vehicle meets a preset re-entry condition of the anti-slope mode, specifically:

[0025] Detecting whether the vehicle meets a preset restart condition, wherein the restart condition includes braking of the brake pedal for a third threshold time, the current gear being set to N gear for a fourth time, and the motor speed of the drive motor being in the same direction as the gear for a fifth time;

[0026] If the vehicle meets any of the above-mentioned restart conditions, it means that the vehicle meets the re-entry condition.

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

[0028] Based on the current speed of the drive motor and with the zero speed of the drive motor as the target, the feedforward torque is first applied to or released from the vehicle through the PI closed loop, and the feedforward torque is increased at a preset speed until the feedforward torque is equal to the anti-slope torque, so as to achieve the application or release of the anti-slope torque to the vehicle.

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

[0030] Determine the corresponding detent slope based on the collected ramp slope and vehicle controller;

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

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

[0033] When the vehicle switches to the anti-slope mode or the normal mode, the detent slope changes according to the state of the vehicle controller.

[0034] When the above scheme releases torque to the electric vehicle, the reason why the electric vehicle exits the anti-slope mode is determined according to the status information, and the corresponding torque release slope is determined according to different reasons, so that the anti-slope torque can be implemented stably and slowly, and a balance can be achieved between response timeliness and vehicle comfort, avoiding the situation where the gear clearance causes tooth rattling and shaking due to the rapid release of torque, which may cause the vehicle to stall.

[0035] A second aspect of the present application provides an electric vehicle anti-slope control system, the system comprising: a functional relationship building module, an anti-slope torque generation module, a feedforward torque generation module and a torque execution module;

[0036] The functional relationship building module is used to obtain the functional relationship between the anti-slope torque and the motor speed change rate by fitting the scatter points in the preset slope-holding torque scatter diagram through the least squares method based on the motor speed change rate;

[0037] The anti-slope rolling torque generation module is used to obtain the anti-slope rolling torque according to the functional relationship and the speed change rate collected most recently after entering the anti-slope rolling mode;

[0038] The feed-forward torque generating module is used to generate the feed-forward torque according to the anti-slope torque and a preset first coefficient;

[0039] The torque execution module is used for applying or releasing the feed-forward torque and the anti-slope torque to the vehicle based on the acquired slope slope. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the implementation manner will be briefly introduced below. Obviously, the drawings described below are only some implementation manners of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0041] Figure 1 This is a specific flow chart of an electric vehicle anti-slope control method provided by a certain embodiment of the present application;

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

[0043] Figure 3 It is an anti-slope torque generation diagram of an anti-slope control method for an electric vehicle provided in a certain embodiment of the present application;

[0044] Figure 4 It is a diagram of applying and removing the anti-slope torque of an anti-slope control method for an electric vehicle provided in a certain embodiment of the present application;

[0045] Figure 5 It is a specific structural diagram of an electric vehicle anti-slope control system provided in a certain embodiment of the present application. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0047] It should be understood that the step numbers used in this article are only for the convenience of description and are not intended to limit the order in which the steps are executed.

[0048] First embodiment

[0049] When driving a car, users face various unexpected scenarios, which pose challenges to the safety and comfort of their driving. For example, when the vehicle is on a slope, when the driver moves his foot from the brake pedal to the accelerator pedal, the vehicle may slide backwards due to the influence of gravity. This scenario is dangerous, so a certain torque needs to be applied to the car to prevent the backward slide distance from being too large and causing a vehicle collision. How to accurately apply or remove torque to the vehicle while ensuring vehicle safety without affecting driving comfort is the main research direction of the embodiments of this application.

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

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

[0052] In the embodiment of the present application, the anti-slope function of an electric vehicle refers to the function that when the vehicle slides backward or forward without human intervention during normal driving, the drive motor automatically generates torque to keep the vehicle stationary for a period of time. If the drive motor wants to achieve this function, it needs to switch between normal mode and anti-slope mode. When in normal mode, the drive system is in torque control state, responding to the torque request instruction issued by the vehicle controller; when in anti-slope mode, the drive system is in speed control state, with zero speed as the target, and automatically adjusts the output torque for speed control.

[0053] To better demonstrate how the vehicle switches between anti-hill slide mode and normal mode, Figure 2 A schematic diagram of the drive system mode switching is provided. As shown in the figure, the left side shows that the vehicle is in normal mode, at which time the drive system of the electric vehicle is in torque control state, responding to the torque request instruction issued by the vehicle controller, and then controlling the speed of the drive motor through the motor controller, and then entering the anti-slope mode after meeting the entry conditions or re-entering the conditions; the right side shows that the vehicle is in anti-slope mode, at which time the drive system of the electric vehicle is in speed control state, and by determining the gear position, brake pedal, whether the ESC system is configured, the charge and discharge power of the power battery, and whether the torque request is received, the motor controller is controlled to adjust the speed of the drive motor, and the output torque is adjusted automatically for speed control.

[0054] In order to identify whether the vehicle has entered the anti-slope mode, it is necessary to regularly collect the slope of the slope on which the electric vehicle is currently located and the status information of the electric vehicle over a period of time. The status information includes the operating data of the electric vehicle's drive motor, power battery, brake pedal, gear position, etc.

[0055] Specifically, the status information includes whether the brake pedal is stepped on, the duration of the stepping action, whether there is a fault in the drive system, the allowable charging and discharging power of the power battery, whether the electric vehicle is equipped with an ESC system, which gear is in which position, the speed of the drive motor, etc.

[0056] Because the vehicle's holding torque is positively correlated with the speed change rate of the drive motor when sliding down the slope, the greater the speed change rate, the greater the required holding torque, so first obtain the current motor speed and the motor speed change rate. Then obtain the holding torque scatter plot.

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

[0058] Step S2, obtaining the anti-slope rolling torque according to the functional relationship and the speed change rate collected most recently after entering the anti-slope rolling mode.

[0059] In the embodiment of the present application, the current speed of the driving motor is obtained, and the zero speed is used as the target, and the anti-slip torque is output through PI closed-loop regulation. However, only the speed closed-loop control will lead to problems such as long adjustment time and long back-slip distance, and poor safety. Therefore, it is necessary to increase the feed-forward torque to reduce the adjustment time and back-slip distance.

[0060] Because the vehicle's holding torque is positively correlated with the speed change rate of the drive motor when sliding down the slope, the greater the speed change rate, the greater the required holding torque, so first obtain the current motor speed and the motor speed change rate. Then obtain the holding torque scatter plot.

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

[0062] Step S3, generating a feed-forward torque according to the anti-slope torque and a preset first coefficient.

[0063] In the embodiment of the present application, the anti-slip torque is multiplied by the ramp slope to obtain the feed-forward torque to accommodate the error of the hill-holding adjustment. The ramp slope is between 0 and 1.

[0064] The hill-holding torque scatter plot is mainly used to analyze the hill-holding performance of electric vehicles on slopes. By observing the scatter plot, one can intuitively understand the changes in the torque output by the drive motor under different slopes and different load conditions, thereby evaluating the hill-holding ability and stability of the vehicle.

[0065] Moreover, the feed-forward torque automatically provides torque to the vehicle for a certain period of time through the drive motor to achieve the purpose of preventing the vehicle from sliding downhill. The generation of feed-forward torque is simple and effective, and does not require a high-computing chip to support the implementation of the function. The addition of this function greatly shortens the time for dynamic adjustment of the anti-slope torque, reduces the backward slip distance, and improves driving safety.

[0066] In the embodiment of the present application, Figure 3 An anti-slope torque generation diagram is provided to illustrate how to generate the anti-slope torque and the feed-forward torque.

[0067] Step S4: applying or removing the feedforward torque and the anti-slope torque to the vehicle based on the acquired slope slope.

[0068] In the embodiment of the present application, the entry conditions, exit conditions and re-entry conditions of the anti-slope mode are formulated. These conditions fully consider the influence of the external environment, and the generation, application and withdrawal of the anti-slope torque can be achieved without adding additional devices such as ESC, slope sensors, etc. Even when the ESC configuration is added to the vehicle iteration, there is no need to update the motor controller software, which is economical and convenient, and the charging and discharging power of the power battery is always paid attention to, providing a guarantee for its safety.

[0069] Further, according to the acquired state information, the entry condition is used to determine whether the electric vehicle can enter the anti-slope mode. The entry condition is specifically met as follows:

[0070] 1) The drive system itself has no faults and can operate normally;

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

[0072] 3) The allowable charge and discharge power of the power battery is greater than the first threshold value; if this condition is not taken into account, the torque generated by the drive system may exceed the power battery's tolerance, causing a dangerous situation of overcurrent failure of the power battery;

[0073] 4) The vehicle is not equipped with an ESC system. This condition is to prevent conflicts between the two functions when the ESC system is added to the subsequent vehicle. The drive system can automatically turn off the hill-holding function and provide the HHC hill-holding assist function by ESC.

[0074] 5) The gear is in D or R gear; when the gear is in D gear, the drive motor has a negative speed, indicating that the vehicle is sliding backward; when the gear is in R gear, the drive motor has a positive speed, indicating that the vehicle is sliding forward;

[0075] 6) The absolute value of the speed of the driving motor is within a preset range; the lower limit of the range is set to prevent slight fluctuations in the speed caused by gear clearance between the driving systems, resulting in erroneous entry into the anti-slope state; the upper limit of the range is set to identify the situation where the severity of the slope exceeds the slope-holding ability of the driving system, and not enter the slope-holding state; illustratively, the range set in the embodiment of the present application is [20,200].

[0076] When the state information satisfies all the above conditions, the driving system of the electric vehicle can enter the anti-slope 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 switches from the anti-slope mode to the normal mode. The exit condition is specifically met as follows:

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

[0079] 2) The brake pedal is pressed for a period of time; this condition indicates that the driver has a clear intention to brake, rather than an accidental touch;

[0080] 3) The allowable charge and discharge power of the power battery is less than or equal to the first threshold value. At this time, the power battery cannot provide sufficient energy for the drive battery to apply the anti-slope torque;

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

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

[0083] 6) The requested torque is opposite to the anti-slope torque;

[0084] 7) The preset anti-slope time has been exceeded. When the anti-slope function is triggered, the motor speed is zero and the drive system outputs torque. This operating condition is the motor stall condition, which will generate a lot of heat. In order to protect the drive system, the anti-slope function is set to a certain running time, which is less than the stall allowable time.

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

[0086] When the anti-slope rolling time is exceeded and the anti-slope rolling function timing ends, when the driving system exits the anti-slope rolling mode, it will be determined whether the re-entry conditions are met.

[0087] Furthermore, continuously entering the anti-slip mode is equivalent to continuously being in a stalled condition, which will cause a serious temperature rise in the device and even damage it. In order to avoid this problem, it is necessary to set the re-entry condition of the anti-slip mode.

[0088] Specifically, the re-entry conditions are met as follows:

[0089] 1) The brake pedal is pressed for a period of time;

[0090] 2) The vehicle's gear is switched to N gear and remains in N gear for a period of time;

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

[0092] When the state information meets any of the above conditions, the driving system of the electric vehicle sets the anti-slope mode permission flag, allowing the vehicle to enter the anti-slope mode again.

[0093] Among them, the setting of the duration in the entry condition, exit condition and re-entry condition is affected by the motor controller hardware and the vehicle interaction signal cycle, and needs to be determined based on the actual hardware data of the vehicle.

[0094] When the normal mode is switched to the anti-slope mode, torque will be applied; when the anti-slope mode is switched to the normal mode, the torque will sometimes be directly withdrawn, such as the gear position is changed to N gear, etc. The application and withdrawal of torque, if not processed by a ramp, may cause setbacks or jitters due to the gear gap in the drive system, resulting in a poor user experience. Therefore, in the embodiment of the present application, a ramp process is added when applying or withdrawing the torque, and the ramp slope is used to apply or withdraw the anti-slope torque to the vehicle.

[0095] Specifically, when the anti-slope torque and the feedforward torque are applied or removed from the electric vehicle, based on the current speed of the drive motor and with the zero speed of the drive motor as the target, the feedforward torque is first applied or removed from the electric vehicle through a PI closed loop, and then the feedforward torque is increased at a preset speed until it is equal to the anti-slope torque. At the same time, when the anti-slope 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 to the anti-slope mode or the normal mode, the detent slope changes according to the state of the vehicle controller.

[0097] For example, Figure 4A diagram of anti-slope torque application and withdrawal is provided, showing the process of the vehicle applying torque from entering the anti-slope mode to withdrawing torque from the anti-slope mode. As shown in the figure, at time t1, the electric vehicle meets the entry condition, and the torque applied by the drive system is processed by slope K1 to avoid the setback problem caused by the vertical application of torque. At t2, the anti-slope timing has not ended, and the vehicle state meets the remaining exit conditions. When the vehicle controller request torque condition is met, the drive system responds to the vehicle controller request torque, and its slope follows the vehicle controller, that is, K2 in the figure; when the exit condition of the brake pedal action is met, due to the operation of the brake system, the drive system torque can be withdrawn quickly to reduce the stall condition, and it is not perceived by the user, that is, it is withdrawn according to the slope K3. When the remaining conditions are met, such as the gear shift to N gear, in order to avoid setbacks, the torque should be withdrawn according to the slope K4, and the slope K4 is less than K3. At t3, the anti-slope function timing ends, and the drive system withdraws according to the slope K5. Since the user does not perform any action at this time, the slope K5 should be smaller than K4 to avoid panicking caused by untwisting too quickly.

[0098] Implementing the embodiments of the present application has the following beneficial effects:

[0099] The embodiment of the present application first collects the slope of the ramp where the electric vehicle is located and the operating status of the current vehicle equipment, including the status data of the electric vehicle drive motor, power battery, brake pedal and gear position. Then, the anti-slip torque and feedforward torque are generated respectively according to the speed of the drive motor and the slope of the ramp, wherein the anti-slip torque can enable the electric vehicle to accurately complete the slope without slipping forward or backward, ensuring the safety of the electric vehicle; considering that the drive motor may cause the backward slip distance to be too large due to the long adjustment time, the feedforward torque is automatically applied or evacuated to the electric vehicle when the slope is stationary, so as to reduce the backward slip distance as much as possible, and further improve the safety of the electric vehicle. Then, according to the entry conditions, exit conditions and re-entry conditions of the perfect anti-slip mode, the torque is applied or evacuated to the electric vehicle through the state information, and the electric vehicle can be accurately controlled to complete the slope in a variety of scenarios without adding the ESC system or other hardware and software, reducing the cost and time of anti-slip control.

[0100] Second embodiment

[0101] Furthermore, in order to execute the electric vehicle anti-slope control system corresponding to the above method embodiment to achieve corresponding functions and technical effects, Figure 5 A structural diagram of an electric vehicle anti-slope control system is provided. For ease of description, only the parts related to this embodiment are shown. The electric vehicle anti-slope control system provided by the embodiment of the present application includes:

[0102] The function relationship building module 201 is used to obtain the function relationship between the anti-slope torque and the motor speed change rate by fitting the scatter points in the preset slope-holding torque scatter diagram through the least square method based on the motor speed change rate.

[0103] In the embodiment of the present application, the anti-slope function of an electric vehicle refers to the function that when the vehicle slides backward or forward without human intervention during normal driving, the drive motor automatically generates torque to keep the vehicle stationary for a period of time. If the drive motor wants to achieve this function, it needs to switch between normal mode and anti-slope mode. When in normal mode, the drive system is in torque control state, responding to the torque request instruction issued by the vehicle controller; when in anti-slope mode, the drive system is in speed control state, with zero speed as the target, and automatically adjusts the output torque for speed control.

[0104] In order to identify whether the vehicle has entered the anti-slope mode, it is necessary to regularly collect the slope of the slope on which the electric vehicle is currently located and the status information of the electric vehicle over a period of time. The status information includes the operating data of the electric vehicle's drive motor, power battery, brake pedal, gear position, etc.

[0105] Specifically, the status information includes whether the brake pedal is stepped on, the duration of the stepping action, whether there is a fault in the drive system, the allowable charging and discharging power of the power battery, whether the electric vehicle is equipped with an ESC system, which gear is in which position, the speed of the drive motor, etc.

[0106] Because the vehicle's holding torque is positively correlated with the speed change rate of the drive motor when sliding down the slope, the greater the speed change rate, the greater the required holding torque, so first obtain the current motor speed and the motor speed change rate. Then obtain the holding torque scatter plot.

[0107] Then, based on the current motor speed and the hill-holding torque scatter diagram, the least squares method is used to fit the scattered points in the hill-holding torque scatter diagram to obtain the functional relationship between the motor speed and the hill-holding torque. Then, the most recent speed change rate after the vehicle enters the anti-hill-slip mode is identified, and the anti-hill-slip torque is obtained through the functional relationship.

[0108] The anti-slope rolling torque generating module 202 is used to obtain the anti-slope rolling torque according to the functional relationship and the speed change rate collected most recently after entering the anti-slope rolling mode.

[0109] In the embodiment of the present application, the current speed of the driving motor is obtained, and the zero speed is used as the target, and the anti-slip torque is output through PI closed-loop regulation. However, only the speed closed-loop control will lead to problems such as long adjustment time and long back-slip distance, and poor safety. Therefore, it is necessary to increase the feed-forward torque to reduce the adjustment time and back-slip distance.

[0110] Because the vehicle's holding torque is positively correlated with the speed change rate of the drive motor when sliding down the slope, the greater the speed change rate, the greater the required holding torque, so first obtain the current motor speed and the motor speed change rate. Then obtain the holding torque scatter plot.

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

[0112] The feed-forward torque generating module 203 is used to generate the feed-forward torque according to the anti-slope torque and a preset first coefficient.

[0113] In the embodiment of the present application, the anti-slip torque is multiplied by the ramp slope to obtain the feed-forward torque to accommodate the error of the 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 electric vehicles on slopes. By observing the scatter plot, one can intuitively understand the changes in the torque output by the drive motor under different slopes and different load conditions, thereby evaluating the hill-holding ability and stability of the vehicle.

[0115] Moreover, the feed-forward torque automatically provides torque to the vehicle for a certain period of time through the drive motor to achieve the purpose of preventing the vehicle from sliding downhill. The generation of feed-forward torque is simple and effective, and does not require a high-computing chip to support the implementation of the function. The addition of this function greatly shortens the time for dynamic adjustment of the anti-slope torque, reduces the backward slip distance, and improves driving safety.

[0116] The torque execution module 204 is configured to apply or release the feed-forward torque and the anti-slope torque to the vehicle based on the acquired slope slope.

[0117] In the embodiment of the present application, when the vehicle meets the preset entry conditions of the anti-slope mode, the vehicle is controlled to enter the anti-slope mode from the normal mode, and at the same time, the feed-forward torque is first applied to the vehicle at the slope slope and then the anti-slope torque is applied;

[0118] When the vehicle meets the preset exit condition of the anti-slope mode, the vehicle is controlled to enter the normal mode from the anti-slope mode, and at the same time, the feedforward torque is firstly released from the vehicle and then the anti-slope torque is released at the slope slope;

[0119] When the vehicle meets the preset re-entry conditions of the anti-slope rolling mode and it is detected that the preset anti-slope rolling time has been exceeded, the vehicle is allowed to enter the anti-slope rolling mode.

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

[0121] In the embodiment of the present application, the entry conditions, exit conditions and re-entry conditions of the anti-slope mode are formulated. These conditions fully consider the influence of the external environment, and the generation, application and withdrawal of the anti-slope torque can be achieved without adding additional devices such as ESC, slope sensors, etc. Even when the ESC configuration is added to the vehicle iteration, there is no need to update the motor controller software, which is economical and convenient, and the charging and discharging power of the power battery is always paid attention to, providing a guarantee for its safety.

[0122] Further, according to the acquired state information, the entry condition is used to determine whether the electric vehicle can enter the anti-slope mode. The entry condition is specifically met as follows:

[0123] 1) The drive system itself has no faults and can operate normally;

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

[0125] 3) The allowable charge and discharge power of the power battery is greater than the first threshold value; if this condition is not taken into account, the torque generated by the drive system may exceed the power battery's tolerance, causing a dangerous situation of overcurrent failure of the power battery;

[0126] 4) The vehicle is not equipped with an ESC system. This condition is to prevent conflicts between the two functions when the ESC system is added to the subsequent vehicle. The drive system can automatically turn off the hill-holding function and provide the HHC hill-holding assist function by ESC.

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

[0128] 6) The absolute value of the speed of the driving motor is within a preset range; the lower limit of the range is set to prevent slight fluctuations in the speed caused by gear clearance between the driving systems, resulting in erroneous entry into the anti-slope state; the upper limit of the range is set to identify the situation where the severity of the slope exceeds the slope-holding ability of the driving system, and not enter the slope-holding state; illustratively, the range set in the embodiment of the present application is [20,200].

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

[0130] In addition, according to the state information and the exit condition, it can be determined whether the electric vehicle switches from the anti-slope mode to the normal mode. The exit condition is specifically met as follows:

[0131] 1) The drive system cannot operate normally, causing the drive motor to be unable to continue to provide torque;

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

[0133] 3) The allowable charge and discharge power of the power battery is less than or equal to the first threshold value. At this time, the power battery cannot provide sufficient energy for the drive battery to apply the anti-slope torque;

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

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

[0136] 6) The requested torque is opposite to the anti-slope torque;

[0137] 7) The preset anti-slope time has been exceeded. When the anti-slope function is triggered, the motor speed is zero and the drive system outputs torque. This operating condition is the motor stall condition, which will generate a lot of heat. In order to protect the drive system, the anti-slope function is set to a certain running time, which is less than the stall allowable time.

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

[0139] When the anti-slope rolling time is exceeded and the anti-slope rolling function timing ends, when the driving system exits the anti-slope rolling mode, it will be determined whether the re-entry conditions are met.

[0140] Furthermore, continuously entering the anti-slip mode is equivalent to continuously being in a stalled condition, which will cause a serious temperature rise in the device and even damage it. In order to avoid this problem, it is necessary to set the re-entry condition of the anti-slip mode.

[0141] Specifically, the re-entry conditions are met as follows:

[0142] 1) The brake pedal is pressed for a period of time;

[0143] 2) The vehicle's gear is switched to N gear and remains in N gear for a period of time;

[0144] 3) The speed of the drive motor is in the same direction as the gear position and lasts for a period of time.

[0145] When the state information meets any of the above conditions, the driving system of the electric vehicle sets the anti-slope mode permission flag, allowing the vehicle to enter the anti-slope mode again.

[0146] Among them, the setting of the duration in the entry condition, exit condition and re-entry condition is affected by the motor controller hardware and the vehicle interaction signal cycle, and needs to be determined based on the actual hardware data of the vehicle.

[0147] When the normal mode is switched to the anti-slope mode, torque will be applied; when the anti-slope mode is switched to the normal mode, the torque will sometimes be directly withdrawn, such as the gear position is changed to N gear, etc. The application and withdrawal of torque, if not processed by a ramp, may cause setbacks or jitters due to the gear gap in the drive system, resulting in a poor user experience. Therefore, in the embodiment of the present application, a ramp process is added when applying or withdrawing the torque, and the ramp slope is used to apply or withdraw the anti-slope torque to the vehicle.

[0148] Specifically, when the anti-slope torque and the feedforward torque are applied or removed from the electric vehicle, based on the current speed of the drive motor and with the zero speed of the drive motor as the target, the feedforward torque is first applied or removed from the electric vehicle through a PI closed loop, and then the feedforward torque is increased at a preset speed until it is equal to the anti-slope torque. At the same time, when the anti-slope 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] Implementing the embodiments of the present application has the following beneficial effects:

[0150] The embodiment of the present application first collects the slope of the ramp where the electric vehicle is located and the operating status of the current vehicle equipment, including the status data of the electric vehicle drive motor, power battery, brake pedal and gear position. Then, the anti-slip torque and feedforward torque are generated respectively according to the speed of the drive motor and the slope of the ramp, wherein the anti-slip torque can enable the electric vehicle to accurately complete the slope without slipping forward or backward, ensuring the safety of the electric vehicle; considering that the drive motor may cause the backward slip distance to be too large due to the long adjustment time, the feedforward torque is automatically applied or evacuated to the electric vehicle when the slope is stationary, so as to reduce the backward slip distance as much as possible, and further improve the safety of the electric vehicle. Then, according to the entry conditions, exit conditions and re-entry conditions of the perfect anti-slip mode, the torque is applied or evacuated to the electric vehicle through the state information, and the electric vehicle can be accurately controlled to complete the slope in a variety of scenarios without adding the ESC system or other hardware and software, reducing the cost and time of anti-slip control.

[0151] The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the scope of protection of the present application. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A method for preventing electric vehicles from sliding downhill, characterized in that: include: Based on the motor speed change rate, the scattered points in the preset slope-holding torque scatter diagram are fitted by the least squares method to obtain the functional relationship between the anti-slope torque and the motor speed change rate; The anti-slope rolling torque is obtained according to the functional relationship and the speed change rate collected most recently after entering the anti-slope rolling mode; Generate a feed-forward torque according to the anti-slope torque and a preset first coefficient; Based on the acquired slope gradient, the feed-forward torque and the anti-slope torque are applied to or released from the vehicle.

2. The electric vehicle anti-slope control method according to claim 1, characterized in that: The feedforward torque is generated according to the anti-slope torque and the preset first coefficient, specifically: The anti-slope torque is multiplied by the first coefficient to obtain the feed-forward torque; wherein the feed-forward torque is smaller than the anti-slope torque.

3. The electric vehicle anti-slope control method according to claim 1, characterized in that: The step of applying or removing the feedforward torque and the anti-slope torque to the vehicle based on the acquired slope slope is specifically as follows: When the vehicle meets the preset entry conditions of the anti-slope mode, the vehicle is controlled to enter the anti-slope mode from the normal mode, and at the same time, the feed-forward torque is first applied to the vehicle at the slope slope and then the anti-slope torque is applied; When the vehicle meets the preset exit condition of the anti-slope mode, the vehicle is controlled to enter the normal mode from the anti-slope mode, and at the same time, the feedforward torque is firstly released from the vehicle and then the anti-slope torque is released at the slope slope; When the vehicle meets the preset re-entry conditions of the anti-slope rolling mode and it is detected that the preset anti-slope rolling time has been exceeded, the vehicle is allowed to enter the anti-slope rolling mode.

4. The electric vehicle anti-slope control method according to claim 3 is characterized in that: When the vehicle meets the preset entry conditions of the anti-slope mode, specifically: Detecting whether the vehicle meets preset start conditions, wherein the start conditions include that the drive system has no faults, the brake pedal is not applied, the allowable charge and 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 gear or R gear, and the absolute value of the speed of the drive motor is within a first range; If the vehicle meets all of the above-mentioned starting conditions, it means that the vehicle meets the entry conditions.

5. The electric vehicle anti-slope control method according to claim 3, characterized in that: When the vehicle meets the preset exit conditions of the anti-slope mode, specifically: Detecting whether the vehicle meets a preset termination condition, wherein the termination condition includes a drive system failure, a brake pedal braking, an allowable charge and discharge power of the power battery being less than or equal to a first threshold, the current gear being set to gear N, a difference between the requested torque and the anti-slope torque being greater than or equal to a second threshold, the requested torque being opposite to the anti-slope torque, and detecting that a preset anti-slope time has been exceeded; If the vehicle meets any of the termination conditions, it means that the vehicle meets the exit condition.

6. The electric vehicle anti-slope control method according to claim 3, characterized in that: When the vehicle meets the preset re-entry conditions of the anti-slope mode, specifically: Detecting whether the vehicle meets a preset restart condition, wherein the restart condition includes braking of the brake pedal for a third threshold time, the current gear being set to N gear for a fourth time, and the motor speed of the drive motor being in the same direction as the gear for a fifth time; If the vehicle meets any of the above-mentioned restart conditions, it means that the vehicle meets the re-entry condition.

7. The electric vehicle anti-slope control method according to claim 1, characterized in that: The applying or removing the feedforward torque and the anti-slope torque to the vehicle based on the acquired slope slope is specifically: Based on the current speed of the drive motor and with the zero speed of the drive motor as the target, the feedforward torque is first applied to or released from the vehicle through the PI closed loop, and the feedforward torque is increased at a preset speed until the feedforward torque is equal to the anti-slope torque, so as to achieve the application or release of the anti-slope torque to the vehicle.

8. The electric vehicle anti-slope control method according to claim 7, characterized in that: The step of increasing the feed-forward torque at a preset speed until the feed-forward torque is equal to the anti-slope torque is specifically as follows: Determine the corresponding detent slope based on the collected ramp slope and vehicle controller; The speed is set according to the torque withdrawal slope, and the application or withdrawal of the feed-forward torque is controlled at the speed until the feed-forward torque is equal to the anti-slope torque.

9. The electric vehicle anti-slope control method according to claim 8, characterized in that: Also includes: When the vehicle switches to the anti-slope mode or the normal mode, the detent slope changes according to the state of the vehicle controller.

10. An electric vehicle anti-slope control system, characterized in that: include: Functional relationship building module, anti-slip torque generation module, feedforward torque generation module and torque execution module; The functional relationship building module is used to obtain the functional relationship between the anti-slope torque and the motor speed change rate by fitting the scatter points in the preset slope-holding torque scatter diagram through the least squares method based on the motor speed change rate; The anti-slope rolling torque generation module is used to obtain the anti-slope rolling torque according to the functional relationship and the speed change rate collected most recently after entering the anti-slope rolling mode; The feed-forward torque generating module is used to generate the feed-forward torque according to the anti-slope torque and a preset first coefficient; The torque execution module is used for applying or releasing the feed-forward torque and the anti-slope torque to the vehicle based on the acquired slope slope.

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