A pure electric drive vehicle driving anti-skid control method and system

Abstract

The present invention discloses a pure electric drive vehicle anti-skid control method and system, comprising: a target limit control layer obtains the vehicle wheel speed and steering wheel angle at the current moment, and determines the drive shaft speed limit according to the vehicle wheel speed and steering wheel angle; when in a transient working condition of wheel slip, a high-frequency control layer calculates the motor speed limit according to the drive shaft speed limit, calculates the torque limit according to the motor speed limit, and controls the output torque of the vehicle drive motor according to the torque limit; when in a steady-state working condition of wheel slip, the TCS in the low-frequency control layer ESP controls the output torque of the vehicle drive motor.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle drive anti-skid driving, and in particular to a drive anti-skid control method and system for a pure electric drive vehicle. Background Art

[0002] In the traditional drive anti-skid control function (TCS), the body electronic stability system (ESP) calculates the slip rate according to the driving wheel speed and the reference vehicle speed, and sends a torque control request to the vehicle controller (VCU) and the transmission control unit (DCU) to control the slip rate near the target value. In addition, while the ESP performs torque intervention on the separation road, it also performs braking control on the low-access side wheels to control the wheel speed difference near the target value. The main problems are that the torque control link is long, the control delay is large, and there is a certain delay in the activation and exit of the TCS function.

[0003] However, there are significant differences in the dynamic characteristics of the drive systems of pure electric vehicles and traditional vehicles. Compared with traditional engines, the drive motor has a larger low-speed torque, faster torque response, smaller moment of inertia, and higher speed. These differences in characteristics result in the TCS function in the traditional ESP being unable to quickly intervene in the torque when the wheels of the pure electric vehicle slip, and the wheel speed and motor speed rise rapidly, resulting in poor drive anti-skid control performance, which can easily lead to the following problems: For example, the wheel speed rises too high at the moment of starting on a low-adhesion road, affecting safety and comfort. At the same time, the power consumption rises rapidly due to the rapid increase in motor speed at the moment of starting, which can easily lead to battery overcurrent; when starting on a separated road (i.e., low-adhesion on one side and high-adhesion on the other side), the high speed of the wheel on the low-adhesion side will cause starting jerking and affect the life of the differential; on a connecting road where high-adhesion and low-adhesion frequently switch, the wheel speed rises too high, and a large impact will occur when the wheel enters a high-adhesion road from a low-adhesion road. Summary of the invention

[0004] The purpose of the present invention is to provide a pure electric drive vehicle anti-skid control method and system, and a computer-readable storage medium to solve the technical problem that the TCS in the traditional ESP has poor anti-skid control performance when applied to a pure electric drive vehicle.

[0005] To achieve the above-mentioned object, the present invention provides a first aspect of a pure electric vehicle driving anti-skid control method, comprising:

[0006] The target limit control layer obtains the current vehicle wheel speed and steering wheel angle, and determines the drive shaft speed limit value according to the vehicle wheel speed and steering wheel angle;

[0007] When in a transient working condition of wheel slip, the high-frequency control layer calculates the motor speed limit according to the drive shaft speed limit, calculates the torque limit according to the motor speed limit, and controls the output torque of the vehicle drive motor according to the torque limit;

[0008] When in a steady-state condition with wheel slip, the low-frequency control layer controls the output torque of the vehicle's drive motor based on the TCS in ESP.

[0009] Optionally, determining the drive shaft speed limit value according to the vehicle wheel speed and the steering wheel angle specifically includes:

[0010] Calculating a reference vehicle speed according to the vehicle wheel speed, and calculating a reference axle speed according to the reference vehicle speed and the steering wheel angle;

[0011] Obtaining a shaft speed offset value according to the reference shaft speed table, and obtaining a basic shaft speed limit value according to the reference shaft speed and the shaft speed offset value;

[0012] The wheel speed difference between the left and right driving wheels of the vehicle is calculated and the absolute value is taken to obtain the wheel speed difference, and the basic shaft speed limit is corrected according to the wheel speed difference to obtain the driving shaft shaft speed limit.

[0013] Optionally, the correcting the basic shaft speed limit value according to the wheel speed difference to obtain the drive shaft shaft speed limit value includes:

[0014] Obtaining a corresponding dead zone threshold value by looking up a table according to the reference vehicle speed, determining whether the wheel speed difference is greater than the dead zone threshold value, performing wheel speed difference correction if greater than the dead zone threshold value, and not performing wheel speed difference correction if less than the dead zone threshold value;

[0015] When performing wheel speed difference correction, if the wheel speed difference increases, the wheel speed difference is multiplied by a preset correction coefficient to obtain an initial wheel speed difference correction value, and the preset correction coefficient is 0 to 1; if the wheel speed difference decreases, the wheel speed difference is subjected to a decrease delay process to obtain an initial wheel speed difference correction value;

[0016] Obtaining a final wheel speed difference correction value according to a preset wheel speed difference limit value and the wheel speed difference initial correction value;

[0017] The shaft speed limit correction value is calculated according to the wheel speed difference correction value, and the basic shaft speed limit value is corrected according to the shaft speed limit correction value to obtain the drive shaft shaft speed limit value.

[0018] Optionally, the working state of the high-frequency control layer includes a preparation state, a control state and a release state;

[0019] The method comprises:

[0020] When the wheels are not slipping, the high-frequency control layer is in a standby state;

[0021] When the high-frequency control layer is in the preparatory state, if the vehicle enters a transient condition of wheel slip, the torque limiting function of the high-frequency control layer is activated and jumps from the preparatory state to the control state;

[0022] After the high-frequency control layer enters the control state, the motor speed limit is calculated according to the drive shaft speed limit, the torque limit is calculated according to the motor speed limit, and the output torque of the vehicle drive motor is controlled according to the torque limit; wherein, if the TCS function of the ESP is activated, or the error between the intervention torque output by the ESP and the actual torque of the motor is within a preset error range, the high-frequency control layer jumps from the control state to the release state; if the high-frequency control layer does not jump from the control state to the release state within a preset time range and returns to a non-slip state, the high-frequency control layer jumps from the control state back to the standby state;

[0023] After the high-frequency control layer enters the release state, the torque limiting function of the high-frequency control layer is turned off, and if it returns to the non-slip state, the high-frequency control layer jumps back to the standby state from the release state.

[0024] Optionally, the working state of the low-frequency control layer includes an idle state, a control state, and a degraded control state;

[0025] The method comprises:

[0026] When the wheels are not slipping, the low-frequency control layer is in an idle state;

[0027] When ESP is degraded without fault, if the vehicle enters a steady-state condition with wheel slip, the TCS function in ESP is activated, and the low-frequency control layer jumps from the idle state to the control state; after the low-frequency control layer enters the control state, the TCS in ESP controls the output torque of the vehicle drive motor; among them, when the TCS function in ESP is turned off, the low-frequency control layer jumps from the control state to the idle state;

[0028] When the ESP fails and is degraded, if the high-frequency control layer is in the control state and the high-frequency control layer has completed the shaft speed control of the transient working condition with sudden shaft speed change, the low-frequency control layer jumps from the idle state to the degraded control state; after the low-frequency control layer enters the degraded control state, the VCU or MCU controls the output torque of the vehicle drive motor according to the drive shaft shaft speed limit; and, if it recovers to the non-slip state, the low-frequency control layer jumps from the degraded control state to the idle state.

[0029] Optionally, for a pure low-adhesion road surface, if the rise of the drive shaft speed has reached a peak point and begins to decrease, it is determined that the high-frequency control layer has completed the shaft speed control of the transient working condition of the shaft speed sudden change;

[0030] For a separated road surface, if the difference between the drive shaft speed and the reference vehicle speed is greater than a preset value, it is determined that the high-frequency control layer has completed the shaft speed control of the transient working condition of the sudden shaft speed change.

[0031] A second aspect of the present invention provides a pure electric vehicle driving anti-skid control system, comprising:

[0032] The target limit control layer is used to obtain the current vehicle wheel speed and steering wheel angle, and determine the drive shaft speed limit value according to the vehicle wheel speed and steering wheel angle;

[0033] A high-frequency control layer, used for calculating a motor speed limit according to the drive shaft speed limit, calculating a torque limit according to the motor speed limit, and controlling an output torque of the vehicle drive motor according to the torque limit when the vehicle is in a transient working condition of wheel slip;

[0034] The low-frequency control layer is used to control the output torque of the vehicle drive motor based on the TCS in ESP when the vehicle is in a steady-state condition with wheel slip.

[0035] Optionally, the target restriction control layer includes:

[0036] A sensor information acquisition unit, used to acquire the current vehicle wheel speed and steering wheel angle;

[0037] A reference axle speed calculation unit, used to calculate a reference vehicle speed according to the vehicle wheel speed, and to calculate a reference axle speed according to the reference vehicle speed and the steering wheel angle;

[0038] a basic shaft speed limit value calculation unit, configured to obtain a shaft speed offset value by looking up a table according to the reference shaft speed, and obtain a basic shaft speed limit value according to the reference shaft speed and the shaft speed offset value; and

[0039] The shaft speed limit correction calculation unit is used to calculate the wheel speed difference between the left and right driving wheels of the vehicle and take the absolute value to obtain the wheel speed difference, and correct the basic shaft speed limit according to the wheel speed difference to obtain the driving shaft shaft speed limit.

[0040] Optionally, the high-frequency control layer includes a high-frequency control state management unit, a motor speed limit calculation unit, and a motor speed limiting unit; the high-frequency control state management unit is used to manage the working state of the high-frequency control layer, and the working state of the high-frequency control layer includes a preparatory state, a control state, and a release state;

[0041] in:

[0042] When the wheel does not slip, the high-frequency control state management unit controls the high-frequency control layer to enter a preparatory state;

[0043] When the high-frequency control layer is in the preparatory state, if the vehicle enters a transient working condition of wheel slip, the torque limiting function of the motor speed limiting unit is activated, and the high-frequency control state management unit controls the high-frequency control layer to jump from the preparatory state to the control state;

[0044] After the high-frequency control layer enters the control state, the motor speed limit calculation unit calculates the motor speed limit according to the drive shaft speed limit; the motor speed limiting unit calculates the torque limit according to the motor speed limit, and controls the output torque of the vehicle drive motor according to the torque limit; wherein, if the TCS function of the ESP is activated, or the error between the intervention torque output by the ESP and the actual torque of the motor is within a preset error range, the high-frequency control state management unit controls the high-frequency control layer to jump from the control state to the release state; if the high-frequency control layer does not jump from the control state to the release state within a preset time range and returns to the non-slip state, the high-frequency control state management unit controls the high-frequency control layer to jump from the control state back to the standby state;

[0045] After the high-frequency control layer enters the release state, the torque limiting function of the motor speed limiting unit is turned off, and if it returns to the non-slip state, the high-frequency control state management unit controls the high-frequency control layer to jump from the control state back to the standby state.

[0046] Optionally, the low-frequency control layer includes a low-frequency control state management unit and a shaft speed control unit; the low-frequency control state management unit is used to manage the working state of the low-frequency control layer, and the working state of the low-frequency control layer includes an idle state, a control state, and a degraded control state; the shaft speed control unit includes a TCS in the ESP, and a VCU or an MCU;

[0047] in:

[0048] When the wheels are not slipping, the low-frequency control state management unit controls the low-frequency control layer to enter an idle state;

[0049] When the ESP is degraded without fault, if the vehicle enters a steady-state condition with wheel slippage, the TCS function in the ESP is activated, and the low-frequency control state management unit controls the low-frequency control layer to jump from the idle state to the control state; after the low-frequency control layer enters the control state, the TCS in the ESP controls the output torque of the vehicle drive motor; wherein, when the TCS function in the ESP is turned off, the low-frequency control state management unit controls the low-frequency control layer to jump from the control state to the idle state;

[0050] When the ESP fails and is degraded, if the high-frequency control layer is in the control state and the high-frequency control layer has completed the shaft speed control of the transient working condition with sudden shaft speed change, the low-frequency control state management unit controls the low-frequency control layer to jump from the idle state to the degraded control state; after the low-frequency control layer enters the degraded control state, the VCU or MCU controls the output torque of the vehicle drive motor according to the drive shaft shaft speed limit; and, if it recovers to the non-slip state, the low-frequency control state management unit controls the low-frequency control layer to jump from the degraded control state to the idle state.

[0051] Implementing the above-mentioned anti-skid control method and system for a pure electric vehicle has at least the following beneficial effects:

[0052] The changes in wheel speed / axle speed during the wheel slip process are decomposed into high-frequency changes and low-frequency changes. Correspondingly, the vehicle drive anti-skid control requirements are decomposed into high-frequency control requirements and low-frequency control requirements. A high-frequency control layer and a low-frequency control layer are designed to cope with the high-frequency control requirements and the low-frequency control requirements respectively. This can effectively suppress the rapid increase of the drive shaft speed under transient conditions where the drive shaft speed changes rapidly, and can also achieve precise control of the drive shaft speed under steady-state conditions where the drive shaft speed is relatively stable.

[0053] Other features and advantages of the present invention will be set forth in the description which follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0055] Figure 1 The present invention is a flowchart of a method for controlling anti-skid driving of a pure electric vehicle according to an embodiment of the present invention.

[0056] Figure 2 Schematic diagram of the working state of the high-frequency control layer in one embodiment of the present invention.

[0057] Figure 3 Schematic diagram of the working state of the low-frequency control layer in one embodiment of the present invention.

[0058] Figure 4 The figure is a schematic diagram of the framework structure of a driving anti-skid control system for a pure electric vehicle in one embodiment of the present invention.

[0059] Figure 5 Schematic diagram of the target restriction control layer framework structure in one embodiment of the present invention.

[0060] Figure 6 It is a schematic diagram of the framework structure of the high-frequency control layer in one embodiment of the present invention.

[0061] Figure 7 Schematic diagram of the low-frequency control layer framework structure in one embodiment of the present invention. DETAILED DESCRIPTION

[0062] Various exemplary embodiments, features and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. In addition, in order to better illustrate the present invention, numerous specific details are given in the specific embodiments below. It should be understood by those skilled in the art that the present invention can also be implemented without certain specific details. In some examples, means well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

[0063] An embodiment of the present invention provides a pure electric vehicle driving anti-skid control method. The method of this embodiment is implemented based on a pure electric vehicle driving anti-skid control system. The control system includes a target limit control layer, a high-frequency control layer, and a low-frequency control layer. The control system can be implemented by a vehicle controller (VCU) or a drive motor controller (MCU) and other hardware devices. Figure 1 The method of this embodiment includes the following steps S1 to S3:

[0064] Step S1, the target limit control layer obtains the current vehicle wheel speed and steering wheel angle, and determines the drive shaft speed limit value according to the vehicle wheel speed and steering wheel angle;

[0065] Specifically, the target limit control layer in this embodiment is used to calculate the desired drive shaft speed limit value as the control target of the high frequency control layer in step S2 and the low frequency control layer in step S3;

[0066] Step S2: when the vehicle is in a transient working condition of wheel slip, the high-frequency control layer calculates the motor speed limit according to the drive shaft speed limit, calculates the torque limit according to the motor speed limit, and controls the output torque of the vehicle drive motor according to the torque limit;

[0067] Specifically, the high-frequency control layer in this embodiment is used for shaft speed control in transient conditions where the shaft speed of the drive shaft changes suddenly when the wheel slips. In this transient condition, a function different from the traditional TCS is used. Instead, the motor torque limit is calculated based on the shaft speed limit of the drive shaft, and the motor torque limit is sent to the motor torque execution unit to control the output torque of the vehicle drive motor. Compared with the traditional TCS function's control of sudden changes in the shaft speed of the drive shaft, the high-frequency control layer in the embodiment of the present invention has a short control link and a fast response, and can achieve rapid adjustment of the shaft speed, effectively suppressing the soaring of the shaft speed of the drive shaft;

[0068] Step S3: When the vehicle is in a steady-state condition with wheel slip, the low-frequency control layer controls the output torque of the vehicle drive motor based on the TCS in the ESP;

[0069] Specifically, in this embodiment, the low-frequency control layer is used to control the drive shaft speed under the condition that the drive shaft speed is relatively stable when the wheel slips, and the precise control of the drive shaft speed is achieved by calling the TCS function of ESP.

[0070] It should be noted that step S2 and step S3 are executed synchronously and in parallel, so as to realize the driving anti-skid control of the pure electric drive vehicle in all working conditions.

[0071] The embodiment of the present invention decomposes the change of wheel speed / axle speed during the wheel slip process into high-frequency changes and low-frequency changes, and correspondingly decomposes the vehicle drive anti-skid control demand into high-frequency control demand and low-frequency control demand, and designs a high-frequency control layer and a low-frequency control layer to respectively cope with the high-frequency control demand and the low-frequency control demand. It can effectively suppress the rapid increase of the drive shaft speed under the transient condition where the drive shaft speed changes rapidly, and can also realize the precise control of the drive shaft speed under the steady-state condition where the drive shaft speed is relatively stable.

[0072] In a specific example, the step S1 of determining the drive shaft speed limit according to the vehicle wheel speed and the steering wheel angle specifically includes:

[0073] Step S11, calculating a reference vehicle speed according to the vehicle wheel speed, and calculating a reference axle speed according to the reference vehicle speed and the steering wheel angle;

[0074] Specifically, there is a corresponding relationship between the shaft speed, the vehicle speed, and the steering wheel angle. The reference shaft speed in this embodiment is the shaft speed of the drive shaft when the vehicle wheels are not slipping. Specifically, the shaft speed of the drive shaft in the non-slip state can be calculated according to the reference vehicle speed, the steering wheel angle, the wheelbase, the track width, the center of mass position, and the steering transmission ratio as the reference shaft speed;

[0075] Step S12, obtaining a shaft speed offset value by looking up a table according to the reference shaft speed, and obtaining a basic shaft speed limit value according to the reference shaft speed and the shaft speed offset value;

[0076] Specifically, before the implementation of this embodiment, the corresponding relationship between different reference shaft speeds and shaft speed offset values ​​can be obtained through actual vehicle calibration data and saved as table data. In step S12, the shaft speed offset value corresponding to the reference shaft speed can be obtained by querying the table data according to the reference shaft speed; wherein the reference shaft speed is added to the shaft speed offset value and then multiplied by the road adhesion coefficient to obtain a basic shaft speed limit value, and the road adhesion coefficient is a known parameter, which is used to correct the sum of the reference shaft speed and the shaft speed offset value;

[0077] Step S13, calculating the wheel speed difference between the left and right driving wheels of the vehicle and taking the absolute value to obtain the wheel speed difference, and correcting the basic shaft speed limit according to the wheel speed difference to obtain the driving shaft shaft speed limit;

[0078] Specifically, the wheel speed difference between the left and right driving wheels of the vehicle can be obtained from ESP via the CAN bus;

[0079] The step of correcting the basic shaft speed limit value according to the wheel speed difference to obtain the drive shaft shaft speed limit value includes:

[0080] Step S131, obtaining a corresponding dead zone threshold value by looking up a table according to the reference vehicle speed, determining whether the wheel speed difference is greater than the dead zone threshold value, if it is greater than the dead zone threshold value, performing wheel speed difference correction, if it is less than the dead zone threshold value, not performing wheel speed difference correction;

[0081] Specifically, in this embodiment, the dead zone threshold is calculated by looking up the table based on the reference vehicle speed; the purpose of setting the dead zone is to filter out the wheel speed difference caused by normal wheel speed fluctuations; when the reference vehicle speed is low, the dead zone threshold needs to be set smaller to ensure a rapid response to the wheel speed difference correction; when the reference vehicle speed is high, the real-time requirements for wheel braking control are reduced, and the dead zone threshold can be set larger;

[0082] Step S132: when performing wheel speed difference correction, if the wheel speed difference increases, the wheel speed difference is multiplied by a preset correction coefficient to obtain an initial wheel speed difference correction value, and the preset correction coefficient is 0 to 1; if the wheel speed difference decreases, a decrease delay process is performed on the wheel speed difference to obtain an initial wheel speed difference correction value;

[0083] Specifically, in this embodiment, the rising rate of the wheel speed difference is adjusted, and its function is to adjust the rising rate of the wheel speed difference correction value when the actual wheel speed difference rises, so as to achieve the limitation of the rising rate of the wheel speed on the low-side of the separation road surface; in addition, in this embodiment, the wheel speed difference is also delayed in decreasing. When the wheel speed difference decreases, the drive shaft speed limit value will also decrease accordingly. Since there is a delay in the transmission of the drive shaft speed limit value signal to the execution unit of the motor speed limit, the limitation will take effect, but it does not meet the expectation in fact. Therefore, the wheel speed difference is delayed in decreasing, that is, a queue is used to store the historical data of the wheel speed difference for a certain length of time, so as to achieve the delayed output of its value;

[0084] Step S133, obtaining a final wheel speed difference correction value according to the preset wheel speed difference limit value and the wheel speed difference initial correction value;

[0085] Specifically, in the embodiment of the present invention, the initial correction value of the wheel speed difference is limited according to the preset wheel speed difference limit value, so as to achieve the limitation of the maximum value of the wheel speed on the low-side of the separation road surface; limiting the initial correction value of the wheel speed difference means that the initial correction value of the wheel speed difference corrected in step S132 needs to be within the range of the preset wheel speed difference limit value, if the initial correction value of the wheel speed difference is within the range of the preset wheel speed difference limit value, no correction is performed, if the initial correction value of the wheel speed difference is not within the range of the preset wheel speed difference limit value, correction is performed, and the preset wheel speed difference limit value is used as the final wheel speed difference correction value;

[0086] Step S134, calculating an axle speed limit correction value according to the wheel speed difference correction value, and correcting the basic axle speed limit value according to the axle speed limit correction value to obtain the drive axle speed limit value;

[0087] Specifically, the requirement for correcting the basic axle speed limit value based on the wheel speed difference correction value is to add the axle speed increment corresponding to the wheel speed difference correction value as a correction value to the basic axle speed limit value;

[0088] It should be noted that the skidding speed of the low-attachment wheels on the separated road is faster and the peak value is higher, which brings about problems such as vehicle shaking, damage difference and reduced life; therefore, in the step S13, the basic axle speed limit is corrected for the separated road axle speed limit; wherein, when the drive shaft is traveling on the separated road, there will be a wheel speed difference between the left and right wheels. Under this condition, the ESP must apply a braking torque to the low-attachment wheels so that the high-attachment wheels obtain the driving torque; the size of the wheel speed difference directly affects the size of the wheel braking torque applied by ESP, therefore, the embodiment of the present invention corrects the axle speed limit based on the wheel speed difference to avoid causing the wheel braking torque applied by ESP to be too small, and at the same time, the method of the embodiment of the present invention can adjust the rising rate of the wheel speed difference and the upper limit of the wheel speed difference, and cooperate with the wheel braking control of ESP to improve the driving performance on flat and slope separated roads.

[0089] In a specific example, see Figure 2 , the working state of the high-frequency control layer includes a preparation state (4-1), a control state (4-2) and a release state (4-3);

[0090] See also Figure 2 , the workflow of the high-frequency control layer specifically includes:

[0091] step11. When the wheels are not slipping, the high-frequency control layer is in a standby state;

[0092] Specifically, in the standby state, the high-frequency control layer is always ready to limit the drive torque.

[0093] Suppress the speed increase of the drive shaft;

[0094] Step 12: When the high-frequency control layer is in the preparatory state, if the vehicle enters a transient condition of wheel slip, the torque limit function of the high-frequency control layer is activated and jumps from the preparatory state to the control state (i.e. Figure 2 Jump state as shown by arrow 4-4 in the figure);

[0095] step 13, after the high-frequency control layer enters the control state, the motor speed limit is calculated according to the drive shaft speed limit, the torque limit is calculated according to the motor speed limit, and the output torque of the vehicle drive motor is controlled according to the torque limit to quickly adjust the drive shaft torque;

[0096] If the TCS function of ESP is activated, or the error between the intervention torque output by ESP and the actual torque of the motor (i.e. the motor output torque at the current moment) is within the preset error range, it means that the high-frequency control demand has been completed. At this time, high-frequency control is no longer required, but the TCS function should be activated to limit the torque. Then the high-frequency control layer jumps from the control state to the release state (i.e. Figure 2 Jump state as shown by arrows 4-5 in the figure);

[0097] If the high-frequency control layer does not jump from the control state to the release state within the preset time range (i.e. Figure 2 The jump state shown by the 4-5 arrows in the figure does not occur), and the vehicle returns to the non-slip state, then the high-frequency control layer jumps from the control state back to the preparatory state (i.e. Figure 2 Jump state as shown by arrows 4-6 in the figure);

[0098] Specifically, after obtaining the drive shaft speed limit, the motor speed limit can be calculated according to the transmission ratio and the tire radius. The specific formula is: motor speed limit = drive shaft speed limit × 1000m / 60min / (2pi×Rm)×transmission ratio; in this formula, the unit of the motor speed limit is rpm, and the unit of the drive shaft speed limit is km / h;

[0099] Among them, the corresponding torque limit value can be calculated by converting according to the motor speed limit value, and the torque limit value is used to limit the torque of the drive motor, so as to control the motor speed below the motor speed limit value; illustratively, the control of the motor speed limit can adopt, for example, PI closed-loop control to limit the motor speed; when the motor speed limit enable state is enabled, and the actual speed of the motor reaches the motor speed limit value, the PI closed-loop control is activated;

[0100] Step 14: After the high-frequency control layer enters the release state, the torque limit function of the high-frequency control layer is turned off. At this time, the high-frequency control layer does not intervene in the driving torque; and if the drive shaft speed returns to the shaft speed state when there is no slipping, the high-frequency control layer jumps from the release state back to the standby state (i.e. Figure 2Jump state as shown by arrows 4-7 in the figure), and prepare for the next high-frequency control intervention.

[0101] In a specific example, see Figure 3 , the working states of the low frequency control layer include an idle state (5-1), a control state (5-2), and a degraded control state (5-3);

[0102] See also Figure 3 , the workflow of the low-frequency control layer specifically includes:

[0103] step21. When the wheel does not slip, the low-frequency control layer is in an idle state;

[0104] Specifically, the idle state is a state in which low frequency control is not activated;

[0105] Step 22: When ESP is downgraded without fault, if the vehicle enters a steady-state condition with wheel slip, the TCS function in ESP is activated, and the low-frequency control layer jumps from the idle state to the control state (i.e. Figure 3 After the low-frequency control layer enters the control state, the TCS in the ESP controls the output torque of the vehicle drive motor; when the TCS function in the ESP is turned off, the low-frequency control layer jumps from the control state to the idle state (i.e. Figure 3 Jump state as shown by the 5-5 arrow in the figure);

[0106] Specifically, when the ESP is degraded without fault, the TCS function of the ESP is available, then after the low-frequency control layer enters the control state, the TCS in the ESP controls the output torque of the vehicle drive motor;

[0107] Step 23, when the ESP fails and is degraded, if the high-frequency control layer is in the control state and the high-frequency control layer has completed the shaft speed control of the transient working condition of the shaft speed sudden change, the low-frequency control layer jumps from the idle state to the degraded control state (i.e. Figure 3 After the low-frequency control layer enters the degraded control state, the VCU or MCU controls the output torque of the vehicle drive motor according to the drive shaft speed limit; and if the drive shaft speed returns to a non-slip state, the low-frequency control layer jumps from the degraded control state to the idle state (i.e. Figure 3 Jump state as shown by arrow 5-1 in the figure);

[0108] Among them, for a pure low-adhesion road surface, if the rise of the drive shaft speed has reached the peak point and begins to decline, it is determined that the high-frequency control layer has completed the shaft speed control of the transient working condition of the sudden change of the shaft speed; for a separated road surface, if the difference between the drive shaft speed and the reference vehicle speed is greater than a preset value, it is determined that the high-frequency control layer has completed the shaft speed control of the transient working condition of the sudden change of the shaft speed;

[0109] Specifically, if ESP is downgraded due to a fault and the TCS function of ESP is unavailable, the low-frequency control layer still needs to control the increase in shaft speed to ensure driving safety as much as possible and prevent problems such as battery overcurrent and differential wear. Therefore, after the low-frequency control layer enters the degraded control state, the VCU or MCU controls the output torque of the vehicle drive motor according to the drive shaft speed limit, that is, calculates the corresponding output torque limit according to the drive shaft speed limit, and performs closed-loop control so that the output torque of the vehicle drive motor is less than the output torque limit.

[0110] It can be seen from the above description of the embodiments that the embodiments of the present invention have the following advantages:

[0111] (1) The embodiments of the present invention can improve the safety and ride comfort of a vehicle when starting and accelerating on a low-adhesion road surface, thereby improving product quality;

[0112] (2) The embodiments of the present invention can effectively protect the vehicle's differential and power battery, reduce the failure rate, and extend their service life;

[0113] (3) The embodiments of the present invention can reduce the difficulty of developing vehicle drivability and low-adhesion control performance; the present invention can decouple vehicle drivability calibration from low-adhesion control calibration, so that the vehicle's throttle torque rising slope and maximum torque drop rate no longer affect the performance of low-adhesion control. Because the embodiments of the present invention use a high-frequency control layer to cope with the working conditions of sudden and rapid changes in shaft speed, there are no longer excessive requirements for the throttle torque rising slope and maximum torque drop rate.

[0114] See also Figure 4 Corresponding to the above-mentioned embodiment method, another embodiment of the present invention provides a pure electric vehicle driving anti-skid control system, which can be used to implement the steps of the above-mentioned embodiment method. The system of this embodiment includes:

[0115] The target limit control layer 1 is used to obtain the current vehicle wheel speed and steering wheel angle, and determine the drive shaft speed limit value according to the vehicle wheel speed and steering wheel angle;

[0116] High frequency control layer 2, used for calculating the motor speed limit according to the drive shaft speed limit, calculating the torque limit according to the motor speed limit, and controlling the output torque of the vehicle drive motor according to the torque limit when the vehicle is in a transient working condition of wheel slip;

[0117] The low-frequency control layer 3 is used to control the output torque of the vehicle drive motor based on the TCS in the ESP when the vehicle is in a steady-state condition with wheel slip.

[0118] Optionally, see Figure 5 , the target restriction control layer 1 comprises:

[0119] The sensor information acquisition unit 11 is used to acquire the current vehicle wheel speed and steering wheel angle;

[0120] A reference shaft speed calculation unit 12, used to calculate a reference vehicle speed according to the vehicle wheel speed, and to calculate a reference shaft speed according to the reference vehicle speed and the steering wheel angle;

[0121] A basic shaft speed limit value calculation unit 13 is used to obtain a shaft speed offset value according to the reference shaft speed table, and obtain a basic shaft speed limit value according to the reference shaft speed and the shaft speed offset value; and

[0122] The shaft speed limit correction calculation unit 14 is used to calculate the wheel speed difference between the left and right driving wheels of the vehicle and take the absolute value to obtain the wheel speed difference, and correct the basic shaft speed limit according to the wheel speed difference to obtain the driving shaft shaft speed limit.

[0123] The basic shaft speed limit calculation unit 13 is specifically used for:

[0124] Obtaining a corresponding dead zone threshold value by looking up a table according to the reference vehicle speed, determining whether the wheel speed difference is greater than the dead zone threshold value, performing wheel speed difference correction if greater than the dead zone threshold value, and not performing wheel speed difference correction if less than the dead zone threshold value;

[0125] When performing wheel speed difference correction, if the wheel speed difference increases, the wheel speed difference is multiplied by a preset correction coefficient to obtain an initial wheel speed difference correction value, and the preset correction coefficient is 0 to 1; if the wheel speed difference decreases, the wheel speed difference is subjected to a decrease delay process to obtain an initial wheel speed difference correction value;

[0126] Obtaining a final wheel speed difference correction value according to a preset wheel speed difference limit value and the wheel speed difference initial correction value; and

[0127] The shaft speed limit correction value is calculated according to the wheel speed difference correction value, and the basic shaft speed limit value is corrected according to the shaft speed limit correction value to obtain the drive shaft shaft speed limit value.

[0128] Optionally, see Figure 6 The high-frequency control layer 2 includes a high-frequency control state management unit 21, a motor speed limit calculation unit 22, and a motor speed limiting unit 23; the high-frequency control state management unit 21 is used to manage the working state of the high-frequency control layer 2, and the working state of the high-frequency control layer includes a preparatory state, a control state, and a release state;

[0129] in:

[0130] When the wheel does not slip, the high-frequency control state management unit 21 controls the high-frequency control layer 2 to enter the preparatory state;

[0131] When the high-frequency control layer 2 is in the preparatory state, if the vehicle enters a transient working condition of wheel slip, the torque limiting function of the motor speed limiting unit 23 is activated, and the high-frequency control state management unit 21 controls the high-frequency control layer 2 to jump from the preparatory state to the control state;

[0132] After the high-frequency control layer 2 enters the control state, the motor speed limit calculation unit 22 calculates the motor speed limit according to the drive shaft speed limit; the motor speed limiting unit 23 calculates the torque limit according to the motor speed limit, and controls the output torque of the vehicle drive motor according to the torque limit; wherein, if the TCS function of the ESP is activated, or the error between the intervention torque output by the ESP and the actual torque of the motor is within a preset error range, the high-frequency control state management unit 21 controls the high-frequency control layer 2 to jump from the control state to the release state; if the high-frequency control layer 2 does not jump from the control state to the release state within a preset time range and returns to the non-slip state, the high-frequency control state management unit 21 controls the high-frequency control layer 2 to jump from the control state back to the standby state;

[0133] After the high-frequency control layer 2 enters the release state, the torque limiting function of the motor speed limiting unit 23 is turned off, and if it returns to the non-slip state, the high-frequency control state management unit 21 controls the high-frequency control layer 2 to jump from the control state back to the standby state.

[0134] Optionally, see Figure 7 The low-frequency control layer 3 includes a low-frequency control state management unit 31 and a shaft speed control unit 32; the low-frequency control state management unit 31 is used to manage the working state of the low-frequency control layer 3, and the working state of the low-frequency control layer 3 includes an idle state, a control state, and a degraded control state; the shaft speed control unit includes a TCS in an ESP, and a VCU or an MCU;

[0135] in:

[0136] When the wheels are not slipping, the low-frequency control state management unit 31 controls the low-frequency control layer 3 to enter an idle state;

[0137] When the ESP is not fault-degraded, if the vehicle enters a steady-state condition with wheel slip, the TCS function in the ESP is activated, and the low-frequency control state management unit 31 controls the low-frequency control layer 3 to jump from the idle state to the control state; after the low-frequency control layer 3 enters the control state, the TCS in the ESP controls the output torque of the vehicle drive motor; wherein, when the TCS function in the ESP is turned off, the low-frequency control state management unit 31 controls the low-frequency control layer 3 to jump from the control state to the idle state;

[0138] When the ESP fails and is downgraded, if the high-frequency control layer is in the control state and the high-frequency control layer has completed the shaft speed control of the transient working condition with sudden shaft speed change, the low-frequency control state management unit 31 controls the low-frequency control layer 3 to jump from the idle state to the degraded control state; after the low-frequency control layer 3 enters the degraded control state, the VCU or MCU controls the output torque of the vehicle drive motor according to the drive shaft shaft speed limit; and, if it is restored to the non-slip state, the low-frequency control state management unit 31 controls the low-frequency control layer 3 to jump from the degraded control state to the idle state.

[0139] Among them, for pure low-adhesion road surfaces, if the rise of the drive shaft speed has reached the peak point and begins to decline, it is determined that the high-frequency control layer has completed the shaft speed control of the transient working condition of sudden shaft speed changes; for separated road surfaces, if the difference between the drive shaft speed and the reference vehicle speed is greater than the preset value, it is determined that the high-frequency control layer has completed the shaft speed control of the transient working condition of sudden shaft speed changes.

[0140] The system embodiment described above is merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0141] It should be noted that the system described in the above embodiment corresponds to the method described in the above embodiment. Therefore, the part of the system described in the above embodiment that is not described in detail can be obtained by referring to the content of the method described in the above embodiment, that is, the specific steps recorded in the method of the above embodiment can be understood as the functions that can be achieved by the system of this embodiment, and will not be repeated here.

[0142] Furthermore, if the anti-skid control system for a pure electric vehicle described in the above embodiment is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium.

[0143] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for controlling driving anti-skid of a pure electric vehicle, characterized in that: include: The target limit control layer obtains the current vehicle wheel speed and steering wheel angle, and determines the drive shaft speed limit value according to the vehicle wheel speed and steering wheel angle; When in a transient working condition of wheel slip, the high-frequency control layer calculates the motor speed limit according to the drive shaft speed limit, calculates the torque limit according to the motor speed limit, and controls the output torque of the vehicle drive motor according to the torque limit; When the vehicle is in a steady-state condition with wheel slip, the low-frequency control layer controls the output torque of the vehicle drive motor based on the TCS in the ESP; wherein the control steps of the transient condition with wheel slip and the control steps of the steady-state condition with wheel slip are executed synchronously; Wherein, the working state of the high frequency control layer includes a preparation state, a control state and a release state; The method comprises: When the wheels are not slipping, the high-frequency control layer is in a standby state; When the high-frequency control layer is in the preparatory state, if the vehicle enters a transient condition of wheel slip, the torque limiting function of the high-frequency control layer is activated and jumps from the preparatory state to the control state; After the high-frequency control layer enters the control state, the motor speed limit is calculated according to the drive shaft speed limit, the torque limit is calculated according to the motor speed limit, and the output torque of the vehicle drive motor is controlled according to the torque limit; wherein, if the TCS function of the ESP is activated, or the error between the intervention torque output by the ESP and the actual torque of the motor is within a preset error range, the high-frequency control layer jumps from the control state to the release state; if the high-frequency control layer does not jump from the control state to the release state within a preset time range and returns to a non-slip state, the high-frequency control layer jumps from the control state back to the standby state; After the high-frequency control layer enters the release state, the high-frequency control layer torque limit function is turned off, and if it returns to the non-slip state, the high-frequency control layer jumps from the release state back to the standby state; The working state of the low-frequency control layer includes an idle state, a control state, and a degraded control state; The method comprises: When the wheels are not slipping, the low-frequency control layer is in an idle state; When ESP is degraded without fault, if the vehicle enters a steady-state condition with wheel slip, the TCS function in ESP is activated, and the low-frequency control layer jumps from the idle state to the control state; after the low-frequency control layer enters the control state, the TCS in ESP controls the output torque of the vehicle drive motor; among them, when the TCS function in ESP is turned off, the low-frequency control layer jumps from the control state to the idle state; When the ESP fails and is degraded, if the high-frequency control layer is in the control state and the high-frequency control layer has completed the shaft speed control of the transient working condition with sudden shaft speed change, the low-frequency control layer jumps from the idle state to the degraded control state; after the low-frequency control layer enters the degraded control state, the VCU or MCU controls the output torque of the vehicle drive motor according to the drive shaft shaft speed limit; and, if it recovers to the non-slip state, the low-frequency control layer jumps from the degraded control state to the idle state.

2. The anti-skid control method for a pure electric vehicle according to claim 1, characterized in that: Determining the drive shaft speed limit value according to the vehicle wheel speed and the steering wheel angle specifically includes: Calculating a reference vehicle speed according to the vehicle wheel speed, and calculating a reference axle speed according to the reference vehicle speed and the steering wheel angle; Obtaining a shaft speed offset value according to the reference shaft speed table, and obtaining a basic shaft speed limit value according to the reference shaft speed and the shaft speed offset value; The wheel speed difference between the left and right driving wheels of the vehicle is calculated and the absolute value is taken to obtain the wheel speed difference, and the basic shaft speed limit is corrected according to the wheel speed difference to obtain the driving shaft shaft speed limit.

3. The anti-skid control method for a pure electric vehicle according to claim 2, characterized in that: The step of correcting the basic shaft speed limit value according to the wheel speed difference to obtain the drive shaft shaft speed limit value includes: Obtaining a corresponding dead zone threshold value by looking up a table according to the reference vehicle speed, determining whether the wheel speed difference is greater than the dead zone threshold value, performing wheel speed difference correction if greater than the dead zone threshold value, and not performing wheel speed difference correction if less than the dead zone threshold value; When performing wheel speed difference correction, if the wheel speed difference increases, the wheel speed difference is multiplied by a preset correction coefficient to obtain an initial wheel speed difference correction value, and the preset correction coefficient is 0 to 1; if the wheel speed difference decreases, the wheel speed difference is subjected to a decrease delay process to obtain an initial wheel speed difference correction value; Obtaining a final wheel speed difference correction value according to a preset wheel speed difference limit value and the wheel speed difference initial correction value; The shaft speed limit correction value is calculated according to the wheel speed difference correction value, and the basic shaft speed limit value is corrected according to the shaft speed limit correction value to obtain the drive shaft shaft speed limit value.

4. The anti-skid control method for a pure electric vehicle according to claim 1, characterized in that: For a pure low-adhesion road surface, if the speed of the drive shaft has reached the peak and started to decrease, it is determined that the high-frequency control layer has completed the shaft speed control of the transient working condition of the shaft speed sudden change; For a separated road surface, if the difference between the drive shaft speed and the reference vehicle speed is greater than a preset value, it is determined that the high-frequency control layer has completed the shaft speed control of the transient working condition of the sudden shaft speed change.

5. A pure electric vehicle driving anti-skid control system, characterized in that: include: The target limit control layer is used to obtain the current vehicle wheel speed and steering wheel angle, and determine the drive shaft speed limit value according to the vehicle wheel speed and steering wheel angle; A high-frequency control layer, used for calculating a motor speed limit according to the drive shaft speed limit, calculating a torque limit according to the motor speed limit, and controlling an output torque of the vehicle drive motor according to the torque limit when the vehicle is in a transient working condition of wheel slip; The low-frequency control layer is used to control the output torque of the vehicle drive motor based on the TCS in the ESP when the vehicle is in a steady-state condition with wheel slip; wherein the control steps of the transient condition with wheel slip and the control steps of the steady-state condition with wheel slip are executed synchronously; Wherein, the high-frequency control layer includes a high-frequency control state management unit, a motor speed limit calculation unit, and a motor speed limiting unit; the high-frequency control state management unit is used to manage the working state of the high-frequency control layer, and the working state of the high-frequency control layer includes a preparatory state, a control state, and a release state; in: When the wheel does not slip, the high-frequency control state management unit controls the high-frequency control layer to enter a preparatory state; When the high-frequency control layer is in the preparatory state, if the vehicle enters a transient working condition of wheel slip, the torque limiting function of the motor speed limiting unit is activated, and the high-frequency control state management unit controls the high-frequency control layer to jump from the preparatory state to the control state; After the high-frequency control layer enters the control state, the motor speed limit calculation unit calculates the motor speed limit according to the drive shaft speed limit; the motor speed limiting unit calculates the torque limit according to the motor speed limit, and controls the output torque of the vehicle drive motor according to the torque limit; wherein, if the TCS function of the ESP is activated, or the error between the intervention torque output by the ESP and the actual torque of the motor is within a preset error range, the high-frequency control state management unit controls the high-frequency control layer to jump from the control state to the release state; if the high-frequency control layer does not jump from the control state to the release state within a preset time range and returns to the non-slip state, the high-frequency control state management unit controls the high-frequency control layer to jump from the control state back to the standby state; After the high-frequency control layer enters the release state, the torque limiting function of the motor speed limiting unit is turned off, and if the non-slip state is restored, the high-frequency control state management unit controls the high-frequency control layer to jump from the control state back to the standby state; The low-frequency control layer includes a low-frequency control state management unit and a shaft speed control unit; the low-frequency control state management unit is used to manage the working state of the low-frequency control layer, and the working state of the low-frequency control layer includes an idle state, a control state, and a degraded control state; the shaft speed control unit includes a TCS in an ESP, and a VCU or an MCU; in: When the wheels are not slipping, the low-frequency control state management unit controls the low-frequency control layer to enter an idle state; When the ESP is degraded without fault, if the vehicle enters a steady-state condition with wheel slippage, the TCS function in the ESP is activated, and the low-frequency control state management unit controls the low-frequency control layer to jump from the idle state to the control state; after the low-frequency control layer enters the control state, the TCS in the ESP controls the output torque of the vehicle drive motor; wherein, when the TCS function in the ESP is turned off, the low-frequency control state management unit controls the low-frequency control layer to jump from the control state to the idle state; When the ESP fails and is degraded, if the high-frequency control layer is in the control state and the high-frequency control layer has completed the shaft speed control of the transient working condition with sudden shaft speed change, the low-frequency control state management unit controls the low-frequency control layer to jump from the idle state to the degraded control state; after the low-frequency control layer enters the degraded control state, the VCU or MCU controls the output torque of the vehicle drive motor according to the drive shaft shaft speed limit; and, if it recovers to the non-slip state, the low-frequency control state management unit controls the low-frequency control layer to jump from the degraded control state to the idle state.

6. The anti-skid control system for a pure electric vehicle according to claim 5, characterized in that: The target restriction control layer includes: A sensor information acquisition unit, used to acquire the current vehicle wheel speed and steering wheel angle; A reference axle speed calculation unit, used to calculate a reference vehicle speed according to the vehicle wheel speed, and to calculate a reference axle speed according to the reference vehicle speed and the steering wheel angle; a basic shaft speed limit value calculation unit, configured to obtain a shaft speed offset value by looking up a table according to the reference shaft speed, and obtain a basic shaft speed limit value according to the reference shaft speed and the shaft speed offset value; and The shaft speed limit correction calculation unit is used to calculate the wheel speed difference between the left and right driving wheels of the vehicle and take the absolute value to obtain the wheel speed difference, and correct the basic shaft speed limit according to the wheel speed difference to obtain the driving shaft shaft speed limit.

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