A dynamic parking torque control method, system, electric vehicle and storage medium

Abstract

The present invention specifically relates to a dynamic parking torque control method, system, electric vehicle and storage medium. The dynamic parking torque control method includes: after detecting the trigger of the vehicle's dynamic parking DBF, performing arbitration on the initial demand torque of the whole vehicle to obtain the initial demand torque T3 of the whole vehicle; obtaining and calculating the vehicle torque change ΔT based on the vehicle's vehicle jerk; obtaining the hysteresis time t1 when the vehicle's deceleration control CDP takes effect and the hysteresis time t2 when the rear wheel anti-lock RWU takes effect; monitoring the CDP state, if CDP is activated, then processing T3 according to ΔT and t1; if CDP is not activated but RWU is activated, then processing T3 according to ΔT and t2; if neither CDP nor RWU is activated, then processing T3 based on the vehicle speed V; the present invention controls the demand-side torque during the dynamic parking process to adjust the torque output, so as to achieve the purpose of improving the dynamic parking drivability and enhancing the safety of the braking process, and solve the problem of insufficient vehicle body attitude control caused by uneven braking during the dynamic parking process.

Description

Technical Field

[0001] The present invention relates to the technical field of electric vehicles, and in particular to a dynamic parking torque control method, system, electric vehicle and storage medium. Background Art

[0002] Electric vehicles have the advantages of simple structure, environmental protection, rapid power response, etc., and have become the target of competition among major automobile manufacturers, with the market retention volume continuously increasing. Based on the voltage platform advantage of electric vehicles, the electronic parking brake system (EPB) gradually replaces the traditional pull-type handbrake due to its simple structure and easy assembly. When the braking system fails or in emergency situations (such as the driver being unable to operate the pedal), the vehicle can be assisted to brake by continuously pulling up the EPB switch, so as to realize emergency vehicle stop.

[0003] For models with the dynamic parking (DBF) function, after the DBF function is triggered, the vehicle is decelerated through the deceleration control (CDP) function of the electronic stability program (ESP); when the CDP function fails, the vehicle can also be decelerated through the rear wheel anti-lock (RWU) function of the electronic parking brake system (EPB); after the DBF decelerates the vehicle to a certain value or below, the controller will control the vehicle to park and shift gears.

[0004] In new energy vehicle models such as pure electric vehicles, range-extended electric vehicles, plug-in hybrid vehicles, and fuel cell vehicles, coasting energy recovery and creep functions have become relatively common configurations. During driving, when the braking system fails suddenly when the coasting recovery torque or creep demand torque of the vehicle is large, the DBF function is triggered through the EPB. Affected by the current demand torque, it may cause the vehicle to change from driving to emergency braking, or from slow braking to emergency braking, resulting in torque mutation, and then affecting the drivability and safety of the vehicle. Therefore, during the EPB-assisted dynamic parking process, the coasting recovery and creep torques of the whole vehicle should be controlled.

[0005] The publication number is: CN111645683A, and the invention name is a method, system, vehicle and storage medium for an ACC system to request ESC dynamic parking, which discloses that: in a set scenario, after the CDD function fails, the ACC realizes the request timing sequence of dynamic parking through CDP or RWU and the switching timing sequence between various functions. However, this solution does not consider the drivability handling problems in the function response process of CDP and RWU.

[0006] Publication No.: CN114802169A, Invention Title: An EPB Control Method and System for Implementing Equivalent P-Gear Function discloses a technical solution: when the vehicle speed is higher than a certain value, the EPB parking control system performs dynamic parking and feeds back the braking state to the motor controller, and the motor controller outputs a clearing instruction to control the motor torque to zero. After the dynamic parking is triggered, the motor controller directly controls the motor torque to zero, without considering the forward jerk and drivability problems caused by vehicle inertia during the response process of the braking actuator.

[0007] In summary, in the control method of EPB-assisted dynamic parking, there are the following problems to be solved:

[0008] 1. CDP realizes deceleration through a hydraulic system. During the pressure building process of the hydraulic system, if the coasting recovery torque exits quickly, the vehicle will jerk forward due to inertia. The higher the vehicle speed and the heavier the vehicle, the greater the forward jerk distance, which poses a safety hazard and also deteriorates the occupant comfort; if the creep torque exits quickly, the vehicle will "nod twice", affecting the occupant comfort.

[0009] 2. RWU drives the caliper through the motor. When the caliper starts to clamp, it is desired that the demand torque at the vehicle's demand end be zeroed to better control the vehicle body posture and enable the vehicle to perform emergency braking. However, there is also a time delay from when RWU is activated to when the caliper starts to clamp. During this delay period, the existence of the demand torque will also affect the vehicle safety and drivability. Summary of the Invention

[0010] In view of the above-mentioned disadvantages of the prior art, the present invention provides a dynamic parking torque control method, system, electric vehicle and storage medium, aiming to adjust the torque output of the powertrain by controlling the demand torque during the dynamic parking process, so as to improve the drivability of dynamic parking, enhance the safety during the braking process, and solve the problem of insufficient vehicle body posture control caused by uneven braking during the dynamic parking process.

[0011] To achieve the above object, the present invention provides a dynamic parking torque control method considering safety and drivability; the input of this control method includes 20 parameters such as the coasting recovery function enable flag, coasting recovery demand torque, creep function enable flag, creep demand torque, DBF activation flag, CDP function activation flag, CDP available status, booster cylinder braking pressure, booster cylinder pressure building hysteresis time, RWU braking activation flag, RWU braking available status, EPB caliper status, RWU function hysteresis time, vehicle rotational mass conversion coefficient, vehicle mass, wheel rolling radius, driveline speed ratio, driveline transmission efficiency, vehicle jerk, vehicle speed, etc., and the output is the processed vehicle demand torque.

[0012] The present invention provides a dynamic parking torque control method, including:

[0013] Monitor the triggering status of the dynamic parking DBF of the vehicle, and perform vehicle initial demand torque arbitration after the DBF is triggered to obtain the vehicle initial demand torque T3;

[0014] Obtain and calculate the vehicle torque change ΔT based on the vehicle's overall vehicle impact;

[0015] Obtain the hysteresis time t1 when the deceleration control CDP of the vehicle becomes effective and the hysteresis time t2 when the rear wheel anti-lock RWU becomes effective;

[0016] Monitor the CDP status. If the CDP is activated, process the vehicle initial demand torque T3 according to the vehicle torque change ΔT and the hysteresis time t1 when the CDP becomes effective;

[0017] If the CDP is not activated but the RWU is activated, process the vehicle initial demand torque T3 according to the vehicle torque change ΔT and the hysteresis time t2 when the RWU becomes effective; otherwise

[0018] If neither the CDP nor the RWU is activated, process the vehicle initial demand torque T3 based on the vehicle speed V.

[0019] In an embodiment of the present invention, the step of monitoring the triggering status of the dynamic parking DBF of the vehicle and performing vehicle initial demand torque arbitration after the DBF is triggered to obtain the vehicle initial demand torque T3 includes:

[0020] After the DBF is triggered, only receive and process the signals of the vehicle's coasting recovery torque T1 and creep torque T2;

[0021] Define the coasting recovery torque T1 and the vehicle's braking torque as negative values. When T1 < 0, make T1 = T1; when T1 > 0, make T1 = -T1. And when the vehicle's coasting recovery function is not turned on, the coasting recovery torque T1 = 0;

[0022] Define the creep torque as a positive value and make T2 = |T2|. And when the creep function is turned off, the creep torque T2 = 0;

[0023] Determine the vehicle initial demand torque T3 based on the coasting recovery torque T1 and the creep torque T2, make T3 = T1 + T2, and 0 ≤ |T3| ≤ max(|T1|max, T2max).

[0024] In an embodiment of the present invention, after the step of determining the initial vehicle demand torque T3 based on the coasting recovery torque T1 and the creeping torque T2, such that T3 = T1 + T2 and 0 ≤ |T3| ≤ max(|T1|max, T2max), the following steps are further included:

[0025] Compare the absolute value of the initial vehicle demand torque T3 with the motor output torque limit T4 of the vehicle, such that T3 = min(|T3|, T4).

[0026] In an embodiment of the present invention, the motor output torque limit includes the motor maximum driving torque limit and the motor maximum recovery torque limit.

[0027] In an embodiment of the present invention, in the step of obtaining and calculating the vehicle torque change amount ΔT based on the vehicle jerk, the calculation formula for the vehicle torque change amount ΔT is as follows:

[0028]

[0029] Wherein, δ is the conversion coefficient of the rotating mass of the vehicle; m is the vehicle mass, in kg; r is the wheel rolling radius, in m; i is the transmission ratio; η is the transmission efficiency; j is the vehicle jerk, in m / s 3 ; Δt is the time interval, in s; ΔT is the vehicle torque change amount corresponding to the vehicle jerk of j within the time of Δt.

[0030] In an embodiment of the present invention, the vehicle jerk j can be expressed as:

[0031]

[0032] Wherein, is the first derivative of the vehicle acceleration, is the second derivative of the vehicle longitudinal speed.

[0033] In an embodiment of the present invention, the step of obtaining the hysteresis time t1 when the vehicle's deceleration control CDP becomes effective and the hysteresis time t2 when the rear wheel anti-lock RWU becomes effective includes:

[0034] Determine the hysteresis time t1 when the CDP becomes effective and the hysteresis time t2 when the RWU becomes effective based on the vehicle's actual vehicle test, specifically including:

[0035] Record the time from the triggering of the DBF to the time when the brake cylinder braking pressure P of the CDP reaches the corresponding pressure value P1 for braking purposes, and record it as the hysteresis time t1; and

[0036] Record the time from the trigger of the DBF to the feedback of the electronic parking brake system (EPB) of the vehicle that the caliper of the vehicle starts to clamp, and denote it as the hysteresis time t2.

[0037] In an embodiment of the present invention, the step of determining the hysteresis time t1 when the CDP becomes effective and the hysteresis time t2 when the RWU becomes effective based on real vehicle tests further includes:

[0038] Respectively record the hysteresis time t1' when the CDP becomes effective and the hysteresis time t2' when the RWU becomes effective corresponding to four vehicle speeds of 120 km / h, 90 km / h, 60 km / h, and 30 km / h of the vehicle;

[0039] Respectively take the average values of the hysteresis time t1' and the hysteresis time t2' corresponding to the four vehicle speeds to obtain the hysteresis time t1 when the CDP becomes effective and the hysteresis time t2 when the RWU becomes effective.

[0040] In an embodiment of the present invention, the step of monitoring the CDP status, and if the CDP is activated, processing the initial vehicle demand torque T3 according to the change in the vehicle's total torque ΔT and the hysteresis time t1 when the CDP becomes effective includes:

[0041] When the DBF is triggered and the CDP is activated, activate the CDP braking function;

[0042] Determine the first change in the vehicle's total torque based on the hysteresis time t1 and the change in the vehicle's total torque ΔT

[0043] When the DBF is triggered, the initial vehicle demand torque is T3, and judge the magnitude relationship between |T3| and ΔT1;

[0044] If |T3| ≤ ΔT1, then the vehicle's total demand torque = T3 = 0;

[0045] If |T3| > ΔT1, then monitor the brake pressure P of the booster cylinder. When P < P1, and make |T3| = |T3| - ΔT2. At the same time, when it is monitored that P ≥ P1 or |T3| < N1 × ΔT1, make the vehicle's total demand torque = T3 = 0; where ΔT2 is the exit gradient of |T3|, and N1 is the anti-jump coefficient of |T3|, and 0.5 ≤ N1 ≤ 0.8.

[0046] In an embodiment of the present invention, the exit gradient ΔT2 of |T3| can be expressed as:

[0047]

[0048] where, |T3|max = max(|T1|max, T2max), and t1 is the hysteresis time when the CDP becomes effective.

[0049] In an embodiment of the present invention, the step of processing the initial vehicle demand torque T3 according to the vehicle torque change amount ΔT and the hysteresis time t2 when the RWU becomes effective if the CDP is not activated but the RWU is activated includes:

[0050] When the DBF is triggered, the CDP is not activated, and the RWU is activated, activate the braking function of the RWU;

[0051] Within the hysteresis time t2 of the RWU braking function, make |T3| = |T3| - ΔT3, and when the t2 time arrives, if |T3| > 0, then |T3| = 0; where, ΔT3 is the exit gradient of |T3|.

[0052] In an embodiment of the present invention, the exit gradient ΔT3 of |T3| can be expressed as:

[0053]

[0054] where, N2 is the safety factor of |T3| and 1.1 ≤ N2 ≤ 1.3, |T3|max = max(|T1|max, T2max), and t2 is the hysteresis time when the RWU becomes effective.

[0055] In an embodiment of the present invention, the step of processing the initial vehicle demand torque T3 based on the vehicle speed V if both the CDP and the RWU are not activated includes:

[0056] When the DBF is triggered and both the CDP and the RWU are not activated, activate the pure electric braking module of the vehicle and obtain the current vehicle speed V;

[0057] When V ≥ V1, T3 = -|T3|max;

[0058] When V2 ≤ V ≤ V1, T3 = V × A + B, where A and B are calibratable constants;

[0059] When V ≤ V2, T3 = 0;

[0060] where, V1 and V2 are calibratable speed values, and V1 > V2.

[0061] The present invention further provides a dynamic parking torque control system. The control system executes the dynamic parking torque control method as described above. The control system includes a CDP braking module, an RWU braking module, and a pure electric braking module. When it is detected that the dynamic parking DBF is triggered, the available states of the CDP braking module and the RWU braking module are sequentially read, and when the CDP braking module or the RWU braking module is available, the CDP braking module or the RWU braking module is activated to enter the CDP braking state or the RWU braking state. Otherwise, the pure electric braking module is activated to enter the pure electric braking state.

[0062] The present invention further provides an electric vehicle, including a dynamic parking torque control system, an electronic parking brake system EPB, an electronic stability program ESP, and a vehicle control unit VCU. The VCU reads the coasting recovery torque signal and the creep torque signal of the electric vehicle to perform arbitration on the initial vehicle demand torque to obtain the initial vehicle demand torque. The VCU monitors the triggering state of the dynamic parking DBF of the EPB and activates the deceleration control CDP of the ESP or the rear wheel anti-lock RWU of the EPB, so that the CDP or the RWU controls the vehicle demand torque of the electric vehicle based on the initial vehicle demand torque through the dynamic parking torque control system.

[0063] In an embodiment of the present invention, the electric vehicle further includes a pure electric braking module. When both the CDP and the RWU are unavailable, the pure electric braking module is activated, and the vehicle demand torque is controlled based on the vehicle speed of the electric vehicle through the dynamic parking torque control system.

[0064] The present invention also provides a computer-readable storage medium, on which computer-readable instructions are stored. When the computer-readable instructions are executed by a processor of a computer, the computer is made to execute the dynamic parking torque control method as described above.

[0065] The dynamic parking torque control method provided by the present invention can be divided into six parts: the first is the arbitration of the initial vehicle demand torque; the second is the calculation of the vehicle torque change amount based on the vehicle jerk; the third is the determination of the hysteresis time for the CDP and RWU functions to take effect; the fourth is the processing of the vehicle demand torque during CDP braking; the fifth is the processing of the vehicle demand torque during RWU braking; the sixth is the processing of the vehicle demand torque when both the CDP and the RWU are unavailable.

[0066] [1] Arbitration of the initial vehicle demand torque:

[0067] 1. To ensure the emergency braking effect, after the DBF is triggered, this control method no longer receives the driver's driving demand torque parsed from the vehicle accelerator pedal signal, and only processes the coasting recovery torque and the creep torque signals input to the vehicle.

[0068] 2. Coasting Recovery Torque Processing: In this control method, the recovery and braking torques of the vehicle are defined as negative values. When the coasting recovery function is enabled, it is necessary to confirm whether the received coasting recovery torque T1 has a sign. If not, a negative sign needs to be added. When the coasting recovery function is not enabled, T1 = 0;

[0069] 3. Creeping Torque Processing: In this control method, the creeping torque is defined as a positive value. When the creeping function is enabled, it is necessary to take the absolute value of the received creeping torque T2. If the creeping function is disabled, then T2 = 0;

[0070] 4. Demand - side Torque Arbitration: Add the coasting recovery torque T1 and the creeping torque T2 to obtain the initial demand torque T3 of the whole vehicle. To prevent torque overflow, limit the range of the initial demand torque of the whole vehicle so that |T3| does not exceed Tmax determined by the maximum coasting recovery and creeping capabilities, and the minimum value of |T3| is 0;

[0071] [2] Calculation of the vehicle torque change ΔT based on the vehicle jerk:

[0072]

[0073] where δ is the conversion coefficient of the rotating mass of the vehicle; m is the vehicle mass, in kg; r is the rolling radius of the wheel, in m; i is the transmission ratio; η is the transmission efficiency; j is the vehicle jerk, in m / s 3 ; Δt is the time interval, in s; ΔT is the vehicle torque change corresponding to the vehicle jerk j within the time interval Δt.

[0074] [3] Determination of the hysteresis time when CDP and RWU functions are effective: The determination process is carried out when both CDP and RWU functions are available, and the determination results are used for the subsequent control method;

[0075] 1. Determination of the pressure - building hysteresis time of the CDP function booster cylinder: Through on - vehicle tests and other methods, record the time from when CDP is triggered by DBF to when the braking pressure P of the booster cylinder is not less than a certain value P1 at vehicle speeds of 120 km / h, 90 km / h, 60 km / h, and 30 km / h respectively. Take the average of the four times to obtain the pressure - building hysteresis time t1 of CDP, with the unit of ms;

[0076] 2. Determination of the hysteresis time of the RWU function: Shield the CDP function through calibration and other methods, and record the hysteresis time from when RWU is triggered by DBF to when the EPB feedback caliper starts to clamp at vehicle speeds of 120 km / h, 90 km / h, 60 km / h, and 30 km / h respectively. Take the average of the four times to obtain the hysteresis time t2 of the RWU function, with the unit of ms.

[0077] [4]During CDP braking, the vehicle's required torque processing:

[0078] 1. When it is detected that DBF is triggered, the CDP available status is "available", and the CDP braking function is activated, enter the CDP braking module;

[0079] 2. Within the CDP pressure - building hysteresis time t1, when the vehicle's jerk is j, the first vehicle torque change

[0080] 3. When the DBF function is triggered, the initial required torque of the vehicle is T3, compare |T3| with ΔT1;

[0081] 4. If |T3| is not greater than ΔT1, directly set the vehicle's required torque to zero;

[0082] 5. If |T3| is greater than ΔT1, monitor the brake pressure P of the booster cylinder. When P is less than a certain value P1, make |T3| start to decrease at a certain gradient ΔT2. During the CDP operation, when it is detected that P is not less than P1 or |T3| is less than N1×ΔT1 (N1≤0.8, to prevent jumps), terminate the superposition of the initial required torque T3 of the vehicle and set the vehicle's required torque to zero;

[0083] 6. Method for determining ΔT2: It is determined by Tmax determined by the maximum coasting recovery and creeping ability and the booster cylinder pressure - building hysteresis time t1 (can be calibrated).

[0084] [5]During RWU braking, the vehicle's required torque processing:

[0085] 1. When it is detected that DBF is triggered, the CDP available status is "unavailable", the RWU available status is "available", and the RWU braking function is activated, enter the RWU braking module;

[0086] 2. Within the hysteresis time t2 when the RWU function takes effect, the initial required torque |T3| of the vehicle decreases at a gradient ΔT3. If |T3| is still greater than 0 after the t2 time has elapsed, directly set it to zero and output it as the vehicle's required torque;

[0087] 3. Method for determining ΔT3: It is determined by Tmax determined by the maximum coasting recovery and creeping ability, the caliper action hysteresis time t2, and the safety factor N2 (1.1≤N2≤1.5) (can be calibrated).

[0088] [6]When both CDP and RWU are unavailable, the vehicle's required torque processing:

[0089] When the DBF trigger is detected, and the available status of CDP is "unavailable" and the available status of RWU is "unavailable", enter the pure electric braking module. At this time, the vehicle's required torque value is related to the vehicle speed V. When V is higher than V1, the vehicle maintains the maximum value of coasting recovery, that is, T3 = -Tmax. When the vehicle decelerates below V1 and is greater than V2, T3 has a linear relationship with the vehicle speed (calibratable). When the vehicle speed drops below V2, T3 is cleared to achieve parking.

[0090] Advantages of the present invention:

[0091] The dynamic parking torque control method of the present invention controls the torque at the demand side during the dynamic parking process to adjust the torque output of the powertrain, achieving the purpose of improving the drivability of dynamic parking and enhancing the safety of the braking process; and according to whether the deceleration control CDP function of the vehicle electronic stability system ESP and the rear wheel anti-lock RWU function of the electronic parking brake system EPB are available, different torque control strategies are adopted respectively to meet the purpose of improving drivability and safety during the dynamic parking process. Description of the drawings

[0092] Figure 1 is the flowchart of the dynamic parking torque control method of the present invention;

[0093] Figure 2 is the schematic diagram of coasting recovery torque processing;

[0094] Figure 3 is the schematic diagram of creep torque processing;

[0095] Figure 4 is the schematic diagram of vehicle required torque arbitration after the dynamic parking DBF trigger;

[0096] Figure 5 is the schematic diagram of the relationship between vehicle required torque and vehicle speed when both the deceleration control CDP and the rear wheel anti-lock RWU fail;

[0097] Figure 6 is the logic flowchart of the dynamic parking control of the electronic parking brake system EPB in an embodiment of the present invention;

[0098] Figure 7 is the architecture diagram of the dynamic parking torque control system of the present invention;

[0099] Figure 8 is the architecture diagram of the electric vehicle of the present invention. Detailed implementation manners

[0100] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for explaining the present invention and not for limiting the protection scope of the present invention.

[0101] It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0102] Appendix Figures 1 to 8 The flowcharts and block diagrams in the appendix illustrate the possible architectures, functions, and operations of systems, methods, and computer program products according to various embodiments of the present invention. Among them, each block in the flowchart or block diagram may represent a module, a program segment, or a part of code, and the above-mentioned module, program segment, or part of code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order from that marked in the accompanying drawings.

[0103] Please refer to Figure 1 , the present invention proposes a dynamic parking torque control method, including:

[0104] Monitoring the triggering state of the dynamic parking DBF of the vehicle, and performing arbitration on the initial demand torque of the whole vehicle after the DBF is triggered to obtain the initial demand torque T3 of the whole vehicle;

[0105] Obtaining and calculating the vehicle torque change amount ΔT based on the vehicle's overall vehicle jerk;

[0106] Obtaining the hysteresis time t1 when the vehicle's deceleration control CDP becomes effective and the hysteresis time t2 when the rear wheel anti-lock RWU becomes effective;

[0107] Monitoring the CDP state. If the CDP is activated, the initial demand torque T3 of the whole vehicle is processed according to the vehicle torque change amount ΔT and the hysteresis time t1 when the CDP becomes effective;

[0108] If the CDP is not activated but the RWU is activated, the initial demand torque T3 of the whole vehicle is processed according to the vehicle torque change amount ΔT and the hysteresis time t2 when the RWU becomes effective; otherwise

[0109] If neither CDP nor RWU is activated, the initial vehicle demand torque T3 is processed based on the vehicle speed V.

[0110] In this embodiment, when the driver cannot brake the vehicle through the brake pedal, dynamic parking is performed by using the vehicle's electronic parking brake system, such as operating the EPB button. At this time, the vehicle control unit VCU receives the dynamic parking command and reads the coasting recovery torque and creep torque of the vehicle, and processes them as the vehicle demand coasting recovery torque T1 and the vehicle demand creep torque T2. Then, torque arbitration is performed on T1 and T2 to obtain the initial vehicle demand torque T3. At the same time, the vehicle control unit reads the current speed of the vehicle and calculates the vehicle jerk parameter based on this. The vehicle torque change ΔT is continuously calculated based on the vehicle jerk and vehicle attributes, and different strategies are adopted to process the initial vehicle demand torque according to the delay time t1 when the deceleration control CDP function of the vehicle electronic stability program ESP becomes effective and the delay time t2 when the rear wheel anti-lock RWU function of the electronic parking brake system EPB becomes effective, so as to realize the torque control of vehicle dynamic parking.

[0111] When the deceleration function and the rear wheel anti-lock function of the vehicle electronic stability system are unavailable and the braking purpose cannot be achieved, the coasting recovery torque of the vehicle's coasting recovery function is directly used as the initial vehicle demand torque for processing, and the size of the coasting recovery torque is adjusted corresponding to the parameter size of the current vehicle speed V of the vehicle, so as to realize the torque control of vehicle dynamic parking.

[0112] It should be noted that the coasting recovery torque of the vehicle is generally determined by the vehicle's energy recovery mode. For example, the coasting recovery torque of the vehicle in the strong energy recovery mode is greater than that in the weak energy recovery mode. Similarly, after detecting the dynamic parking command, the vehicle can be calibrated to directly use the coasting recovery torque in the strong energy recovery mode as the initial vehicle demand torque for processing.

[0113] Please refer to Figures 2 to 4 , in an embodiment, the steps of monitoring the trigger state of the vehicle's dynamic parking DBF and performing initial vehicle demand torque arbitration after DBF is triggered to obtain the initial vehicle demand torque T3 include:

[0114] After DBF is triggered, only receive and process the signals of the vehicle's coasting recovery torque T1 and creep torque T2;

[0115] Define the coasting recovery torque T1 and the vehicle's braking torque as negative values. When T1 < 0, make T1 = T1; when T1 > 0, make T1 = -T1. And when the coasting recovery function of the vehicle is not turned on, the coasting recovery torque T1 = 0;

[0116] Define the creep torque as a positive value and make T2 = |T2|. And when the creep function is turned off, the creep torque T2 = 0;

[0117] Determine the initial vehicle demand torque T3 based on the coasting recovery torque T1 and the creeping torque T2, such that T3 = T1 + T2, and 0 ≤ |T3| ≤ max(|T1|max, T2max);

[0118] Compare the absolute value of the initial vehicle demand torque T3 with the motor output torque limit T4 of the vehicle, such that T3 = min(|T3|, T4); wherein, the motor output torque limit includes the maximum driving torque limit of the motor and the maximum recovery torque limit of the motor.

[0119] In this embodiment, the arbitration of the initial vehicle demand torque is to confirm, calculate, and limit the input signals such as the magnitudes and polarities of the coasting recovery torque and the creeping torque of the vehicle by the vehicle controller and then output the initial vehicle demand torque. Specifically, it includes: first, confirm and process the polarities of the received coasting recovery torque and creeping torque; then sum the coasting recovery torque and the creeping torque with signs to determine the initial vehicle demand torque; finally, compare the absolute value of the initial vehicle demand torque obtained by summation with the boundary value determined by the motor capacity, and take the smaller value for output.

[0120] It should be noted that "positive torque" in the torque polarity corresponds to driving, such as forward gear driving and reverse gear driving (such as acceleration, creeping), and the demand torque is positive; "negative torque" corresponds to recovery and braking, and the demand torque is negative for both forward gear and reverse gear coasting recovery and braking. Among them, the maximum value of the initial vehicle demand torque T3 is the maximum value between the absolute value of the maximum coasting recovery torque and the maximum creeping torque. The motor maximum driving torque limit included in the motor output torque limit T4 corresponds to the maximum positive torque that can be provided, and the motor maximum recovery torque limit corresponds to the maximum negative torque that can be provided. Therefore, it determines the achievable parameter range of the initial vehicle demand torque, and compares the calculated value with the motor output torque limit and takes the minimum value to perform torque control within the torque range that the vehicle can provide.

[0121] In one embodiment, in the step of obtaining and calculating the vehicle torque change ΔT based on the vehicle's vehicle jerk, the calculation formula for the vehicle torque change ΔT is as follows:

[0122]

[0123] wherein, δ is the rotational mass conversion coefficient of the vehicle; m is the vehicle mass, in kg; r is the wheel rolling radius, in m; i is the transmission ratio; η is the transmission efficiency; j is the vehicle jerk, in m / s 3 ; Δt is the time interval, in s; ΔT is the vehicle torque change corresponding to the vehicle jerk of j within the time interval Δt.

[0124] Similarly, the vehicle impact degree j can be expressed as:

[0125]

[0126] Wherein, is the first derivative of the vehicle acceleration, is the second derivative of the vehicle longitudinal speed.

[0127] In this embodiment, the dynamic parking torque control is performed by the vehicle torque change amount ΔT. The definition of the vehicle impact degree is "the change rate of acceleration", which is derived from the derivative of the vehicle acceleration. In the industry, it is generally considered that when J is within 10m / s 3 the longitudinal state change of the vehicle will not significantly affect the comfort of the occupants. Therefore, the vehicle torque change amount is related to the vehicle impact degree j.

[0128] The magnitude of the vehicle acceleration is determined by the output torque after the output torques of each power source are coupled by the power coupling mechanism. Therefore, the acceleration change rate, that is, the impact degree, can directly reflect the fluctuation of the output torque. The greater the output torque fluctuation, the greater the impact degree. The quantization indexes of the impact degree vary from country to country. The recommended value of the impact degree in Germany is |J| ≤ 10m / s 3 and the recommended value of the impact degree in China is |J| ≤ 17.64m / s 3 Therefore, this embodiment uses the impact degree J as the evaluation index of the vehicle torque transformation amount ΔT. Similarly, to reduce the torque fluctuation, |J| = 10m / s 3 is selected as the calibration value to participate in the calculation of the vehicle torque change amount.

[0129] In one embodiment, the steps of obtaining the hysteresis time t1 when the vehicle's deceleration control CDP takes effect and the hysteresis time t2 when the rear wheel anti-lock RWU takes effect include:

[0130] Determining the hysteresis time t1 when the CDP takes effect and the hysteresis time t2 when the RWU takes effect based on the vehicle's actual vehicle test, specifically including:

[0131] Recording the time from the trigger of the DBF to the time when the braking cylinder braking pressure P of the CDP reaches the corresponding pressure value P1 for braking purposes, and recording it as the hysteresis time t1; and

[0132] Recording the time from the trigger of the DBF to the time when the electronic parking brake system EPB of the vehicle feedbacks that the calipers start to clamp, and recording it as the hysteresis time t2.

[0133] Wherein, the steps of determining the hysteresis time t1 when the CDP takes effect and the hysteresis time t2 when the RWU takes effect based on the actual vehicle test further include:

[0134] Record the hysteresis time t1' when the CDP takes effect and the hysteresis time t2' when the RWU takes effect corresponding to the four vehicle speeds of 120 km / h, 90 km / h, 60 km / h, and 30 km / h respectively;

[0135] Take the average value of the hysteresis time t1' and the hysteresis time t2' corresponding to the four vehicle speeds respectively to obtain the hysteresis time t1 when the CDP takes effect and the hysteresis time t2 when the RWU takes effect.

[0136] During the time when the deceleration control CDP function in the vehicle electronic stability system ESP and the rear-wheel anti-lock RWU function of the electronic parking brake system EPB take effect, there is a lack of control of the vehicle's total torque, which may lead to potential drivability and safety problems. Therefore, it is necessary to control the vehicle's torque based on the change in the vehicle's total torque during this time. Therefore, the activation times of the CDP function and the RWU function are measured separately, and it is determined whether they are activated based on the pressure build-up state of the booster cylinder corresponding to the CDP in the vehicle and the caliper state corresponding to the RWU in the vehicle respectively. Since only when the CDP fails will the RWU take effect after the DBF is triggered, when the vehicle is in a normal state, the deceleration control function can be disabled by calibrating (the method is not limited, the purpose is to achieve the function), for example, by shielding the CDP function of the ESP, and then the hysteresis time of the RWU action can be determined.

[0137] It should be noted that by separately measuring the hysteresis times of the CDP and the RWU under four vehicle speed states and calculating the average value, the selected vehicle speed states are only used as an example. To improve the accuracy of the hysteresis times of the corresponding CDP and RWU, the number of vehicle speed measurements and the correlation between the calculated vehicle speed and the corresponding hysteresis time can be considered, and then corresponding calibration can be carried out in the vehicle control unit, so that when calculating the vehicle's total torque variable, the corresponding hysteresis time parameter can be selected according to the real-time vehicle speed, further improving the vehicle's torque control effect and enhancing the drivability and safety during the vehicle's dynamic parking process.

[0138] Please refer to Figure 6 , in an embodiment, the steps of monitoring the CDP state and, if the CDP is activated, processing the initial vehicle demand torque T3 according to the change in the vehicle's total torque ΔT and the hysteresis time t1 when the CDP takes effect include:

[0139] When the DBF is triggered and the CDP is activated, activate the CDP braking function;

[0140] Determine the first change in the vehicle's total torque based on the hysteresis time t1 and the change in the vehicle's total torque ΔT

[0141] When the DBF is triggered, the initial vehicle demand torque is T3, and the magnitude relationship between |T3| and ΔT1 is judged;

[0142] If |T3| ≤ ΔT1, the vehicle's overall demand torque = T3 = 0;

[0143] If |T3| > ΔT1, monitor the brake pressure P of the booster cylinder. When P < P1, make |T3| = |T3| - ΔT2. At the same time, when it is monitored that P ≥ P1 or |T3| < N1 × ΔT1, make the vehicle's overall demand torque = T3 = 0; where ΔT2 is the exit gradient of |T3|, and N1 is the anti-jump coefficient of |T3|, and 0.5 ≤ N1 ≤ 0.8.

[0144] At the same time, the exit gradient ΔT2 of |T3| can be expressed as:

[0145]

[0146] where |T3|max = max(|T1|max, T2max), and t1 is the hysteresis time when CDP takes effect.

[0147] In this embodiment, for the convenience of vehicle attitude control, after DBF is activated, it is more conducive to vehicle body attitude control without the intervention of the overall vehicle demand torque. However, directly clearing the demand torque will cause problems such as vehicle forward rush and secondary nodding. One of the impacts of these problems is "driver comfort". Therefore, first obtain the initial overall vehicle demand torque through torque arbitration, and then the change amount of the overall vehicle demand torque within the hysteresis time calculated by the vehicle's jerk is the upper limit ΔT1 of the torque change amount affecting driver comfort. If the overall vehicle demand torque |T3| is not greater than this value at this time, it means that even if |T3| is directly cleared, it will not affect occupant comfort. At this time, it can be directly cleared without processing the demand torque. Similarly, the overall vehicle torque change amount reflected by ΔT1 is actually the upper limit that determines whether to process the current coasting recovery or creep torque.

[0148] It should be noted that when judging the size relationship between |T3| and ΔT1, the anti-jump coefficient N1 is added. Its specific meaning is: when |T3| > ΔT1, the torque control function is triggered. If it is set that |T3| is not greater than ΔT1, the torque control function is not triggered. If the detected value of |T3| jitters, it will cause the torque control function to jump between triggering and not triggering, affecting drivability. Therefore, it is required that after the torque control function is triggered, the function can be closed only after |T3| < N1 × ΔT1, so that the vehicle controller can stably decide whether to perform torque control. Similarly, according to experience, N1 is often taken between 0.5 and 0.8.

[0149] Please refer to Figure 6 , in an embodiment, if CDP is not activated but RWU is activated, the steps of processing the initial overall vehicle demand torque T3 according to the overall vehicle torque change amount ΔT and the hysteresis time t2 when RWU takes effect include:

[0150] When the DBF is triggered and the CDP is not activated while the RWU is activated, activate the RWU braking function;

[0151] Within the hysteresis time t2 of the RWU braking function, make |T3| = |T3| - ΔT3. When the time t2 arrives, if |T3| > 0, then |T3| = 0; where ΔT3 is the exit gradient of |T3|.

[0152] At the same time, the exit gradient ΔT3 of |T3| can be expressed as:

[0153]

[0154] Where N2 is the safety factor of |T3| and 1.1 ≤ N2 ≤ 1.3, |T3|max = max(|T1|max, T2max), and t2 is the hysteresis time when the RWU takes effect.

[0155] In this embodiment, the RWU function realizes dynamic parking by clamping the caliper. When the RWU takes effect, it is more necessary for the vehicle's required torque to be in a zero state so that the electronic stability system can better control the vehicle body attitude. Therefore, the process of torque control for the vehicle is limited within the hysteresis time from the activation of the RWU to the clamping of the caliper to avoid the impact during the torque control process when the RWU takes effect.

[0156] It should be noted that when controlling the vehicle's initial required torque to exit with a gradient of ΔT3, a safety factor N2 is introduced to ensure that the vehicle's required torque can be zeroed under any vehicle conditions. When the safety factor N2 is not introduced, the exit gradient ΔT3 of the vehicle's initial required torque is ΔT3 = |T3|max / t2 * 1000, and the calculated value represents the gradient that just makes the torque zero fastest. However, considering that when the RWU controls the vehicle body state, in order to maintain the stability of the vehicle attitude, it is more desirable that the vehicle's required torque does not intervene. Therefore, the safety factor N2 is increased to ensure that the vehicle's required torque can definitely be zeroed before the RWU starts to clamp. Similarly, according to experience, the value of N2 is between 1.1 and 1.3.

[0157] Please refer to Figure 5 and Figure 6 , in an embodiment, if neither the CDP nor the RWU is activated, the steps of processing the vehicle's initial required torque T3 based on the vehicle speed V include:

[0158] When the DBF is triggered and neither the CDP nor the RWU is activated, activate the vehicle's pure electric braking module and obtain the current vehicle speed V;

[0159] When V ≥ V1, T3 = -|T3|max;

[0160] When V2 ≤ V ≤ V1, T3 = V × A + B, where A and B are calibratable constants;

[0161] When V ≤ V2, T3 = 0;

[0162] Wherein, V1 and V2 are calibratable speed values, and V1 > V2.

[0163] In this embodiment, please refer to Figure 5 , where "low" in the vehicle speed on the abscissa can correspond to V2 and "high" can correspond to V1 for calculation. The vehicle's required torque value is related to the vehicle speed V. When V is higher than V1, the vehicle maintains the maximum value of coasting recovery, that is, T3 = -|T3|max. When the vehicle decelerates below V1 and is greater than V2, T3 has a linear relationship with the vehicle speed (calibratable). When the vehicle speed drops below V2, T3 is cleared to achieve parking.

[0164] In the following embodiment:

[0165] The current vehicle speed of the vehicle is 70 km / h. When the driver discovers an emergency ahead, releases the accelerator pedal and intends to brake by stepping on the brake pedal but finds that the brake pedal is ineffective, so the EPB is used emergently for dynamic parking. The torque control strategy during this process is as follows:

[0166] [1] Coasting recovery torque processing: Please refer to Figure 1 , the coasting recovery function is turned on. In the D gear (forward gear), vehicle speed 70 km / h, accelerator pedal not depressed, and energy recovery mode is strong recovery state, after processing the input coasting recovery torque, the vehicle's required coasting recovery torque is obtained as T1 = -1200 N·m.

[0167] [2] Creeping torque processing: Please refer to Figure 2 , the creeping function is turned on. In the D gear (forward gear), vehicle speed 70 km / h, and brake pedal not depressed state, after processing the input creeping torque, the vehicle's required creeping torque is obtained as T2 = 0 N·m.

[0168] [3] Torque arbitration: Please refer to Figure 3 , add the coasting recovery torque and the creeping torque, and the vehicle's required torque is obtained as T3 = T1 + T2 = -1200 + 0 = -1200 N·m. Its absolute value is less than Tmax (Tmax = 1500 N·m), so the initially required torque of the whole vehicle arbitrated is T3 = -1200 N·m.

[0169] [4]Calculation of the vehicle torque change based on the jerk: For the example vehicle, the rotational mass conversion coefficient δ = 1.05, the mass m = 2000 kg, the wheel rolling radius r = 0.325 m, the transmission ratio i = 11.137, and the transmission efficiency η = 0.98. From the drivability evaluation and relevant standards, the vehicle jerk j = 10 m / s 3 , the interval time = 1 s, and the jerk per unit time is obtained as 10 m / s 3 . The corresponding vehicle torque change at this time = 625.3 N·m.

[0170] [5]Determination of the CDP and RWU function hysteresis time: Through on-vehicle testing, the hysteresis time t1 from the activation of CDP to the brake pressure P of the booster cylinder being not less than P1 (P1 = 40 bar) is 500 ms, and the hysteresis time t2 from the triggering of RWU to the start of clamping of the EPB feedback caliper is 700 ms.

[0171] [6]When CDP brakes, processing of the initial vehicle demand torque:

[0172] 1. If the triggering of DBF is monitored at this time, the CDP available state is "available", and when the CDP braking function is activated, enter the CDP braking module;

[0173] 2. During the CDP pressure build-up hysteresis time t1, when the jerk is 10 m / s 3 , the vehicle torque change ΔT1 = t1 / 1000×ΔT = 500 / 1000×625.3 = 312.7 N·m;

[0174] 3. When the DBF function is triggered, the vehicle demand torque is T3 = -1200 N·m, and compare |T3| with ΔT1;

[0175] 4. It is easy to obtain that |T3| > ΔT1. During the CDP pressure build-up hysteresis time t1, monitor the brake pressure P of the booster cylinder. When P < 40 bar, reduce |T3| according to a certain gradient ΔT2. When it is monitored that P ≥ 40 bar or |T3| ≤ N1×ΔT1 = 0.7×312.7 = 218.9 N·m, terminate the superposition of the vehicle demand torque and clear the vehicle demand torque T3;

[0176] 5. Method for determining ΔT2: ΔT2 = Tmax / t1×1000 = 1500 / 500×1000 = 3000 N·m / s, that is, before reaching the torque zeroing condition, the vehicle demand torque |T3| will decrease at a gradient of 3000 N·m / s.

[0177] [7]When RWU brakes, processing of the vehicle demand torque:

[0178] 1. If the DBF trigger is detected at this time, and the available status of CDP is "unavailable", the available status of RWU is "available" and the RWU braking function is activated, enter the RWU braking module;

[0179] 2. Within the RWU function hysteresis time t2, the initial vehicle demand torque T3 = -1200 N·m, and it exits with a gradient of ΔT3. If the EPB feedback caliper starts to clamp and |T3| is not equal to 0, then set T3 = 0 N·m;

[0180] 3. Method for determining ΔT3: Take the safety factor N2 = 1.1, then the initial vehicle demand torque exit gradient ΔT3 = N2 × Tmax / t2 × 1000 = 1.1 × 1500 / 700 × 1000 = 2357 N·m / s.

[0181] [8] When both CDP and RWU are unavailable, processing of vehicle demand torque:

[0182] If the DBF trigger is detected at this time, the available status of CDP is "unavailable" and the available status of RWU is "unavailable", and the current vehicle speed V = 70 km / h, which is higher than V1 = 60 km / h, then set T3 = -Tmax = -1500 N·m and hold it; after the vehicle speed decreases to V1, the vehicle demand torque T3 is obtained by Figure 4 interpolation; when the vehicle speed decreases to below V2 = 2 km / h, set T3 to zero to achieve parking.

[0183] In another embodiment:

[0184] The current vehicle speed of the vehicle is 5 km / h, and the vehicle is in a creeping state. At this time, the driver suddenly feels that the legs cannot move, so the EPB is urgently used for dynamic parking. The torque control strategy during this process is as follows:

[0185] [1] Processing of coasting recovery torque: Refer to Figure 1 , the coasting recovery function is turned on. In the R gear (reverse gear), vehicle speed 5 km / h, accelerator pedal not depressed, and energy recovery mode is strong recovery, after processing the input coasting recovery torque, the vehicle demand coasting recovery torque obtained is T1 = 0 N·m.

[0186] [2] Processing of creeping torque: Refer to Figure 2 , the creeping function is turned on. In the R gear (reverse gear), vehicle speed 5 km / h, and brake pedal not depressed, after processing the input creeping torque, the vehicle demand creeping torque obtained is T2 = 700 N·m.

[0187] [3] Torque arbitration: Refer to Figure 4, sum the coasting recovery torque and the creeping torque to obtain the vehicle demand torque as T3 = T1 + T2 = 0 + 700 = 700 N·m. Since its absolute value is less than Tmax (Tmax = 1500 N·m), the initially arbitrated vehicle demand torque is T3 = 700 N·m.

[0188] [4] Calculation of the vehicle torque change based on the jerk: For the vehicle in the embodiment, the rotational mass conversion coefficient δ = 1.05, the mass m = 2000 kg, the wheel rolling radius r = 0.325 m, the transmission ratio i = 11.137, and the transmission efficiency η = 0.98. From the drivability evaluation and relevant standards, the vehicle jerk j = 10 m / s 3 , with an interval time = 1 s, the jerk per unit time is obtained as 10 m / s 3 corresponding to the vehicle torque change = 625.3 N·m.

[0189] [5] Measurement of the CDP and RWU function hysteresis time: Through on-vehicle testing, the hysteresis time t1 from the activation of DBF to the brake pressure P of the booster cylinder being not less than P1 (P1 = 40 bar) for CDP is 500 ms, and the hysteresis time t2 from the triggering of DBF to the start of clamping of the EPB feedback caliper for RWU is 700 ms.

[0190] [6] Processing of the initially demanded vehicle torque during CDP braking:

[0191] 1. If DBF triggering is monitored at this time, the CDP available state is "available", and the CDP braking function is activated, enter the CDP braking module;

[0192] 2. During the CDP pressure build-up hysteresis time t1, when the jerk is 10 m / s 3 , the vehicle torque change ΔT1 = t1 / 1000×ΔT = 500 / 1000×625.3 = 312.7 N·m;

[0193] 3. When the DBF function is triggered, the vehicle demand torque is T3 = 700 N·m, and compare |T3| with ΔT1;

[0194] 4. It is easy to obtain |T3| > ΔT1. Monitor the brake pressure P of the booster cylinder. When P < 40 bar, the vehicle demand torque T3 should be superimposed, and |T3| should be decreased according to a certain gradient ΔT2. When it is monitored that P ≥ 40 bar or |T3| ≤ N1×ΔT1 = 0.7×312.7 = 218.9 N·m, terminate the superimposition of the vehicle demand torque and set the demand torque T3 to zero;

[0195] 5. Method for determining ΔT2: ΔT2 = Tmax / t1 × 1000 = 1500 / 500 × 1000 = 3000 N·m / s. That is, before reaching the torque zeroing condition, the vehicle's required torque |T3| will decrease at a gradient of 3000 N·m / s.

[0196] [7] When RWU brakes, processing of the vehicle's required torque:

[0197] 1. If it is detected at this time that DBF is triggered, the available status of CDP is "unavailable", the available status of RWU is "available" and the RWU braking function is activated, enter the RWU braking module;

[0198] 2. Within the RWU function hysteresis time t2, the vehicle's initial required torque T3 = 800 N·m, and it exits at a gradient of ΔT3. If |T3| is not equal to 0 when the EPB feedback caliper starts to clamp, then set T3 = 0 N·m;

[0199] 3. Method for determining ΔT3: Take the safety factor N2 = 1.1, then the vehicle's initial required torque exit gradient ΔT3 = N2 × Tmax / t2 × 1000 = 1.1 × 1500 / 700 × 1000 = 2357 N·m / s.

[0200] [8] When both CDP and RWU are unavailable, processing of the vehicle's required torque:

[0201] If it is detected at this time that DBF is triggered, the available status of CDP is "unavailable" and the available status of RWU is "unavailable", and the current vehicle speed V = 5 km / h, which is higher than V2, the vehicle's required torque T3 is obtained by Figure 4 interpolation; when the vehicle speed decreases to below V2 = 2 km / h, zero T3 to achieve parking.

[0202] Please refer to Figure 7 , the present invention also provides a dynamic parking torque control system. The control system executes the dynamic parking torque control method as described above. The control system includes a CDP braking module, an RWU braking module, and a pure electric braking module. When it is detected that the dynamic parking DBF is triggered, the available statuses of the CDP braking module and the RWU braking module are read in sequence, and when the CDP braking module or the RWU braking module is available, activate the CDP braking module or the RWU braking module and enter the CDP braking state or the RWU braking state, otherwise activate the pure electric braking module to enter the pure electric braking state.

[0203] The dynamic parking torque control system is installed in the vehicle's vehicle control unit to execute the dynamic parking torque control method, and by respectively judging whether the deceleration control function of the vehicle electronic stability system and the rear-wheel anti-lock function of the electronic parking brake system are in an available state, it selects the torque control method specifically used during the execution of the dynamic parking process. Similarly, when the deceleration control function and the rear-wheel anti-lock function of the electronic stability system fail, it can select the coasting recovery torque used when the drive motor in the vehicle's pure electric braking module performs energy recovery as the torque control object during the execution of the dynamic parking process, improving the vehicle's dynamic parking function and at the same time maintaining the drivability and safety of dynamic parking.

[0204] Please refer to Figure 8 , the present invention further provides an electric vehicle, including a dynamic parking torque control system, an electronic parking brake system EPB, an electronic stability system ESP, and a vehicle control unit VCU. The VCU reads the coasting recovery torque signal and the creep torque signal of the electric vehicle to perform arbitration on the initial vehicle demand torque to obtain the initial vehicle demand torque. The VCU monitors the trigger state of the dynamic parking DBF of the EPB and activates the deceleration control CDP of the ESP or the rear-wheel anti-lock RWU of the EPB, so that the CDP or RWU controls the vehicle demand torque of the electric vehicle based on the initial vehicle demand torque through the dynamic parking torque control system. The electric vehicle also includes a pure electric braking module. When both the CDP and RWU are unavailable, the pure electric braking module is activated, and the vehicle demand torque is controlled based on the vehicle speed of the electric vehicle through the dynamic parking torque control system.

[0205] The electric vehicle processes various input parameters through the vehicle control unit, including the coasting recovery function enable flag bit, the coasting recovery demand torque, the creep function enable flag bit, the creep demand torque, the DBF activation flag bit, the CDP function activation flag bit, the CDP availability status, the booster cylinder braking pressure, the booster cylinder pressure build-up hysteresis time, the RWU braking activation flag bit, the RWU braking availability status, the EPB caliper status, the RWU function hysteresis time, the vehicle rotating mass conversion coefficient, the vehicle mass, the wheel rolling radius, the transmission ratio of the driveline, the driveline transmission efficiency, the vehicle jerk, the vehicle speed, etc., 20 parameters in total. And based on this, combined with the dynamic parking torque control method, it outputs the processed vehicle demand torque. At the same time, the vehicle control unit adapts different vehicle operating conditions according to the deceleration control function of the vehicle electronic stability system, the rear-wheel anti-lock function, and the coasting recovery torque of the vehicle's pure electric braking module, and selects the dynamic parking strategy to maintain the drivability and safety of the vehicle during the dynamic parking process.

[0206] Finally, the present invention also provides a computer-readable storage medium, on which computer-readable instructions are stored. When the computer-readable instructions are executed by a processor of a computer, the computer is made to execute the dynamic parking torque control method as described above, so that an electric vehicle can achieve dynamic parking while maintaining drivability and safety.

[0207] In summary, the dynamic parking torque control method, system, electric vehicle, and storage medium provided by the embodiments of the present invention control the demand-side torque during the dynamic parking process to adjust the torque output of the powertrain, achieving the purpose of improving the drivability of dynamic parking and enhancing the safety of the braking process; and different torque control strategies are respectively adopted according to whether the deceleration control CDP function of the vehicle electronic stability system ESP and the rear-wheel anti-lock RWU function of the electronic parking brake system EPB are available, meeting the purpose of improving drivability and safety during the dynamic parking process.

[0208] The above embodiments are only used to exemplarily illustrate the principles and effects of the present invention, rather than to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A dynamic parking torque control method, characterized in that, Including: Monitoring the trigger status of the dynamic parking DBF of the vehicle, and performing vehicle initial demand torque arbitration after the DBF is triggered to obtain the vehicle initial demand torque T3; Obtain and calculate the vehicle torque change amount based on the vehicle's overall impact degree ; Obtaining the hysteresis time t1 when the deceleration control CDP of the vehicle becomes effective and the hysteresis time t2 when the rear wheel anti-lock RWU becomes effective; Monitor the CDP status. If the CDP is activated, process the initial vehicle demand torque T3 according to the vehicle torque change amount and the hysteresis time t1 when the CDP becomes effective; If the CDP is not activated but the RWU is activated, the initial vehicle demand torque T3 is processed according to the change in the vehicle torque and the hysteresis time t2 when the RWU becomes effective; Otherwise If neither the CDP nor the RWU is activated, process the vehicle initial demand torque T3 based on the vehicle speed V of the vehicle; Wherein, when the DBF is triggered and the CDP is activated, activate the CDP braking function; Based on the hysteresis time t1 and the change in vehicle torque Determine the first change in vehicle torque ; When the DBF is triggered, the initial required torque of the whole vehicle is T3, and it is judged the magnitude relationship between |T3| and ; If |T3| ≤ , then the overall vehicle demand torque of the vehicle = T3 = 0; If |T3| > , then monitor whether the brake pressure P of the booster cylinder reaches the corresponding pressure value P1 for the braking purpose. When P < P1, subtract ΔT2 from the absolute value of T3 to obtain a new absolute value of T3. At the same time, when it is monitored that P ≥ P1 or |T3| < N1 × , set the vehicle demand torque = T3 = 0; where is the exit gradient of |T3|, and N1 is the anti-jump coefficient of |T3|, and 0.5 ≤ N1 ≤ 0.

8.

2. The control method according to claim 1, wherein The step of monitoring the trigger status of the dynamic parking DBF of the vehicle and performing vehicle initial demand torque arbitration after the DBF is triggered to obtain the vehicle initial demand torque T3 includes: After the DBF is triggered, only receive and process the signals of the coasting recovery torque T1 and the creep torque T2 of the vehicle; Define the coasting recovery torque T1 and the braking torque of the vehicle as negative values. When the received coasting recovery torque T1 is positive, convert it to a negative value; when the received coasting torque T1 is negative, keep its negative value, and when the coasting recovery function of the vehicle is not turned on, the coasting recovery torque T1 = 0; Define the creep torque as a positive value and make T2 = |T2|, and when the creep function is turned off, the creep torque T2 = 0; Determine the vehicle initial demand torque T3 based on the coasting recovery torque T1 and the creep torque T2, make T3 = T1 + T2, and 0 ≤ |T3| ≤ max(|T1|max, T2max).

3. The control method according to claim 2, wherein After the step of determining the vehicle initial demand torque T3 based on the coasting recovery torque T1 and the creep torque T2, making T3 = T1 + T2, and 0 ≤ |T3| ≤ max(|T1|max, T2max), it further includes: Compare the absolute value of the vehicle initial demand torque T3 with the motor output torque limit T4 of the vehicle, and make T3 = min(|T3|, T4).

4. The control method according to claim 3, wherein The motor output torque limit includes the motor maximum driving torque limit and the motor maximum recovery torque limit.

5. The control method according to claim 1, wherein Obtaining and calculating the change amount of the vehicle's total torque based on the vehicle's overall impact degree In the step of , the calculation formula of the change amount of the vehicle's total torque Among them, is the conversion coefficient of the rotating mass of the vehicle; m is the vehicle mass, in kg; r is the rolling radius of the wheel, in m; i is the transmission ratio; is the transmission efficiency of the transmission system; j is the vehicle impact severity, in m / s 3 ; is the time interval, in s; is at During the time, the change in the vehicle torque corresponding to the vehicle impact severity of j.

6. The control method according to claim 5, wherein The vehicle jerk j can be expressed as: wherein, is the first derivative of the vehicle acceleration, is the second derivative of the vehicle longitudinal speed.

7. The control method according to claim 1, characterized in that The step of obtaining the hysteresis time t1 when the deceleration control CDP of the vehicle becomes effective and the hysteresis time t2 when the rear wheel anti-lock RWU becomes effective includes: Determine the hysteresis time t1 when the CDP becomes effective and the hysteresis time t2 when the RWU becomes effective based on the vehicle's actual vehicle test, specifically including: Record the time from the trigger of the DBF to the time when the braking cylinder braking pressure P of the CDP reaches the corresponding pressure value P1 for braking purposes, and record it as the hysteresis time t1; and Record the time from the trigger of the DBF to the time when the electronic parking brake system EPB of the vehicle feedbacks that the calipers of the vehicle start to clamp, and record it as the hysteresis time t2.

8. The control method according to claim 7, wherein The step of determining the hysteresis time t1 when the CDP becomes effective and the hysteresis time t2 when the RWU becomes effective based on the actual vehicle test further includes: Record the hysteresis time t1' when the CDP takes effect and the hysteresis time t2' when the RWU takes effect corresponding to the four vehicle speeds of 120 km / h, 90 km / h, 60 km / h, and 30 km / h of the vehicle respectively; Average the hysteresis time t1' and the hysteresis time t2' corresponding to the four vehicle speeds respectively to obtain the hysteresis time t1 when the CDP takes effect and the hysteresis time t2 when the RWU takes effect.

9. The control method according to claim 1, characterized in that The exit gradient of the said |T3| can be expressed as: ； Among them, , t1 is the hysteresis time for the CDP to take effect.

10. The control method according to claim 8, wherein If the CDP is not activated but the RWU is activated, then according to the change amount of the vehicle torque and the hysteresis time t2 when the RWU becomes effective, the step of processing the initial required torque T3 of the vehicle includes: When the DBF is triggered and the CDP is not activated while the RWU is activated, activate the RWU braking function; During the hysteresis time t2 of the RWU braking function, subtract ΔT3 from the absolute value of T3 to obtain a new absolute value of T3. When the time t2 is reached, if |T3| > 0, then |T3| = 0; where is the exit gradient of |T3|.

11. The control method according to claim 10, characterized in that, The exit gradient of the |T3| can be expressed as: ； Among them, N2 is the safety factor of |T3|, and 1.1 ≤ N2 ≤ 1.3, , and t2 is the hysteresis time when the RWU becomes effective.

12. The control method according to claim 1, wherein If neither the CDP nor the RWU is activated, the steps of processing the initial vehicle demand torque T3 based on the vehicle speed V include: When the DBF is triggered and neither the CDP nor the RWU is activated, activate the pure electric braking module of the vehicle and obtain the current vehicle speed V; When V≥V1, set T3 to the negative maximum absolute value of T3; When V2≤V≤V1, T3 = V×A + B, where A and B are calibratable constants; When V≤V2, T3 = 0; Wherein, V1 and V2 are calibratable speed values, and V1>V2.

13. A dynamic parking torque control system, characterized in that, The control system executes the dynamic parking torque control method according to any one of claims 1 to 12. The control system includes a CDP braking module, an RWU braking module, and a pure electric braking module. When it is monitored that the dynamic parking DBF is triggered, the available states of the CDP braking module and the RWU braking module are read in sequence, and when the CDP braking module or the RWU braking module is available, activate the CDP braking module or the RWU braking module to enter the CDP braking state or the RWU braking state, otherwise activate the pure electric braking module to enter the pure electric braking state.

14. An electric vehicle, characterized in that, It includes a dynamic parking torque control system, an electronic parking brake system EPB, an electronic stability system ESP, and a vehicle controller VCU. The dynamic parking torque control system executes the dynamic parking torque control method according to any one of claims 1 to 12. The VCU reads the coasting recovery torque signal and the creeping torque signal of the electric vehicle to perform arbitration on the initial vehicle demand torque to obtain the initial vehicle demand torque. The VCU monitors the triggering state of the dynamic parking DBF of the EPB and activates the deceleration control CDP of the ESP or the rear wheel anti-lock RWU of the EPB, so that the CDP or the RWU controls the vehicle demand torque of the electric vehicle based on the initial vehicle demand torque through the dynamic parking torque control system.

15. The electric vehicle according to claim 14, characterized in that, The electric vehicle further includes a pure electric braking module. When neither the CDP nor the RWU is available, activate the pure electric braking module and control the vehicle demand torque based on the vehicle speed of the electric vehicle through the dynamic parking torque control system.

16. A computer-readable storage medium, characterized in that, It stores computer-readable instructions, and when the computer-readable instructions are executed by the processor of the computer, the computer executes the dynamic parking torque control method according to any one of claims 1 to 12.

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