Calculation method and system for braking energy recovery power capacity boundary of P2 configuration vehicle

Abstract

The present invention discloses a method and a system for calculating the braking energy recovery power capacity boundary of a P2 configuration vehicle. The calculation method includes: calculating the total energy recovery power capacity boundary; calculating the original value of the braking energy recovery power capacity boundary; calculating the full power condition value of the braking energy recovery power capacity boundary; and calculating the braking energy recovery power capacity boundary at the current moment according to whether the vehicle remains in a certain gear within the D gear, or is in the process of switching between different gears within the D gear, or is in the process of switching from the D gear to the N gear, and whether the braking energy recovery prohibition condition is satisfied. By using the present invention, an accurate braking energy recovery power capacity boundary can be obtained, providing guarantee for the braking energy recovery efficiency of the whole vehicle to reach a relatively high level and avoiding braking safety risks.

Description

Technical Field

[0001] The present invention belongs to the field of hybrid vehicle control, and particularly relates to a method and system for calculating the braking energy recovery power capacity boundary of a P2 configuration vehicle. Background Art

[0002] An important energy-saving technology for hybrid vehicles is the vehicle's braking energy recovery system. How much recovery torque the power system can respond to and accurately feedback to the main control unit of the braking energy recovery (i.e., the chassis controller) is one of the most important links in the braking energy recovery system. The braking energy recovery power capacity boundary refers to the torque capacity of the power system to respond to the chassis braking energy recovery target.

[0003] As Figure 1 shown, the working process of the braking energy recovery system of a P2 architecture vehicle includes: the power controller (i.e., PCU) calculates and outputs its braking energy recovery power capacity boundary to the chassis controller in real time; the chassis controller determines the braking energy recovery target torque allocated to the motor and the torque allocated to the chassis hydraulic actuator according to the brake pedal depth, the braking energy recovery power capacity boundary, and the torque required by the brake pedal, and sends the braking energy recovery target torque allocated to the motor to the power controller; the power controller calculates the current actual braking energy recovery torque executed by the motor and feeds back the current actual braking energy recovery torque of the motor to the chassis controller; the chassis controller compares the fed-back current actual braking energy recovery torque of the motor with the issued braking energy recovery target torque, and controls the chassis hydraulic pressure to supplement the torque that the motor has not executed in place, avoiding the loss of vehicle braking force. Under the condition that the braking energy recovery power capacity boundary permits, it is generally preferentially allocated to the motor to achieve the maximum braking energy recovery effect. During the execution process, if the chassis controller monitors that the motor execution is lower than the allocation, it will coordinate the chassis hydraulic pressure to supplement at an appropriate rate. It should be noted that if the chassis hydraulic pressure supplements too fast, there will be a noise from the brake fluid oil pump; if the chassis hydraulic pressure supplements too slow, the vehicle will have a loss of braking force.

[0004] If the calculation of the braking energy recovery power capacity boundary is inaccurate, such as being too small, it will lead to waste of energy; such as being too large, it will lead to the inability to fully execute the force allocated by the chassis, resulting in partial or even temporary complete loss of vehicle braking force, bringing serious vehicle safety risks. In addition, the braking energy recovery power capacity boundary cannot suddenly drop significantly, which will cause the chassis hydraulic pressure to be insufficiently supplemented, also resulting in partial or even temporary complete loss of vehicle braking force. Therefore, accurate calculation of the braking energy recovery power capacity boundary is an important guarantee for the safety and efficiency of the braking energy recovery system.

[0005] As Figure 2As shown in the figure, there is only one motor 2 in the P2 architecture vehicle. The motor 2 is used for both driving and braking energy recovery. The motor 2 is located at the rear end of the engine 3 and the front end of the transmission 1. When the vehicle is running in the EV mode (i.e., the pure electric mode), the K0 clutch at the engine end is in the disengaged state, and the engine 3 does not participate in the operation of the transmission system. During the braking energy recovery process, the motor 2 and the transmission 1 are connected in series. When the vehicle is running in the HEV mode (i.e., the hybrid mode), the K0 clutch at the engine end is in the engaged state, and the engine 3 participates in the operation of the transmission system. During the braking energy recovery process, the motor 2, the engine 3 and the transmission 1 are connected in series. According to its structure, in the HEV mode, when calculating the braking energy recovery power capacity boundary, not only the recovery capabilities of the power battery and the motor 2 need to be considered, but also the impacts brought by the engine 3 and the transmission 1 need to be considered.

[0006] CN111775924A discloses a control method for maximizing the braking energy recovery of a series-parallel hybrid power system, which describes the specific distribution methods of the electric braking forces of two motors in the pure electric working mode, the series working mode, and the parallel working mode, including the calculation of a rough capacity boundary, that is, taking the smaller value of (system electric braking torque demand - engine back-dragging torque, driving motor's real-time electric braking torque capacity * empirical value K2 of the maximum load rate in the efficient area) as the driving motor torque control; taking the smaller value of (system electric braking torque demand - engine back-dragging torque - driving motor's real-time electric braking torque) as the ISG motor torque control; using the actual driving motor efficiency characteristic MAP and the ISG motor efficiency characteristic MAP for offline simulation, and finally obtaining the braking torques of the driving motor and the ISG motor to be executed. There are several problems with this control method: (1) It does not clearly calculate the braking energy recovery power capacity boundary. The "system electric braking torque demand" mentioned in it is generally allocated by the chassis controller, but the necessary condition for its allocation is to know the braking energy recovery power capacity boundary. Otherwise, if the chassis controller allocates too much or too little, the energy waste or the loss of the vehicle's braking force mentioned above will occur; (2) The calculations of the driving motor torque and the ISG motor torque do not consider the gear positions of the transmission. Obviously, for a transmission with multiple gear positions, due to the large differences in the gear ratios of different gear positions, the capacity boundary at the motor end converted to the wheel-end torque of the vehicle will be different; further, for a transmission with multiple gear positions, after shifting gears (mainly referring to upshifting), due to the reduction of the gear ratio, the torque boundary corresponding to the wheel end will suddenly decrease significantly, and the power capacity boundary at this time needs special treatment; (3) The analysis of the power capacity boundary when the engine participates is insufficient. When the vehicle speed is low and the engine speed is close to the idle target speed n, the engine will enter a speed control mode with the idle target speed n as the target. In this mode, the engine will inject fuel and generate torque. Obviously, at this time, the engine torque is not the "engine back-dragging torque"; (4) It does not design the prohibited conditions for the braking energy recovery power capacity boundary. Summary of the Invention

[0007] The object of the present invention is to provide a method and system for calculating the braking energy recovery power capacity boundary of a P2 configuration vehicle, so as to obtain an accurate braking energy recovery power capacity boundary, and provide guarantees for the braking energy recovery efficiency of the whole vehicle to reach a relatively high level and avoid braking safety risks.

[0008] The method for calculating the braking energy recovery power capacity boundary of the P2 configuration vehicle described in the present invention includes:

[0009] Using the formula: Mer = Min(MotTqMin, ElecCpbyMin, TrsmCluTqMin), calculate the total energy recovery power capacity boundary Mer. Wherein, Min() represents the minimum operation, MotTqMin represents the maximum negative torque of the motor, ElecCpbyMin represents the maximum charging torque of the motor under the current battery SOC, and TrsmCluTqMin represents the maximum negative torque of the transmission and clutch.

[0010] Using the formula: MbRgnMaxRaw = Mer * GearRatAct - CoastTqDmd, calculate the original value MbRgnMaxRaw of the braking energy recovery power capacity boundary (which is also the wheel end value of the braking energy recovery power capacity boundary). Wherein, GearRatAct represents the current gear ratio, and CoastTqDmd represents the coasting energy recovery torque. The torque interaction between the power controller and the chassis controller in the braking energy recovery system is unified as the wheel end torque.

[0011] Using the formula: MbRgnMaxALL = MbRgnMaxRaw * λ, calculate the full power condition value MbRgnMaxALL of the braking energy recovery power capacity boundary. Wherein, λ represents the discount coefficient, 0 ≤ λ ≤ 1. Using the discount coefficient can achieve the purpose that the braking energy recovery power capacity boundary is 0 when the vehicle speed is low and the engine speed is close to the idle target speed n during the braking energy recovery process of the P2 configuration vehicle (with a dual clutch DCT transmission) in the HEV mode. At this time, the engine will enter the speed control mode with the idle target speed n as the target.

[0012] If the vehicle remains in a certain gear within the D gear range, when the braking energy recovery prohibition condition is not met, make MbRgnMax = MbRgnMaxALL; wherein, MbRgnMax represents the braking energy recovery power capacity boundary at the current moment.

[0013] If the vehicle is in the process of switching between different gears in the D gear, when MbRgnTar > MbRgnMaxRawGearTar and the braking energy recovery prohibition condition is not met, make MbRgnMax decrease from MbRgnTar + OffsetA as the starting point to MbRgnMaxRawGearTar at a preset first slope K1, so as to ensure that the chassis controller gradually reduces the distribution of electric braking and gradually increases the distribution of hydraulic braking.

[0014] If the vehicle is in the process of switching between different gears in the D gear, when MbRgnTar ≤ MbRgnMaxRawGearTar and the braking energy recovery prohibition condition is not met, make MbRgnMax = MbRgnTar + OffsetA until the gear shift is successful, and then make MbRgnMax = MbRgnMaxRawGearTar.

[0015] Among them, MbRgnTar represents the target torque of braking energy recovery allocated by the chassis controller, MbRgnMaxRawGearTar represents the boundary value of the braking energy recovery power capacity of the target gear, OffsetA represents the torque increment, and OffsetA = T * k max , T represents a preset CAN signal period, and k max represents the maximum rate of the chassis controller allocating the target torque of braking energy recovery.

[0016] If the vehicle is in the process of switching from D gear to N gear (corresponding to receiving the command that the shift lever position is N sent by the TCU), when the braking energy recovery prohibition condition is not met, make MbRgnMax decrease from the braking energy recovery power capacity boundary at the previous moment to 0 at a second slope K2. From a hardware perspective, when the actual gear is N gear, the transmission system will lose the torque transmission ability, and the braking energy recovery power capacity boundary should be 0. However, when the transmitted torque has not been truly unloaded to 0, the actual gear will not be executed to N yet. Therefore, during the process of the boundary decreasing, the power still has the ability to execute the electric braking torque within the boundary range.

[0017] When the braking energy recovery prohibition condition is met, make MbRgnMax = 0.

[0018] Preferably, the discount factor λ is specifically:

[0019] When the vehicle is running in the EV mode (i.e., the pure electric mode), λ = 1.

[0020] When the vehicle is operating in the HEV mode (i.e., the hybrid mode), first use the formula: Vname = 60 * π * D * n / 1000 * GearRatAct to calculate the nominal vehicle speed Vname, then use the formula: ΔV = VehSpd - Vname to calculate the vehicle speed difference ΔV, and finally use ΔV to query the preset discount coefficient table by interpolation to obtain the discount coefficient λ. Where D represents the wheel diameter, n represents the idle target speed, VehSpd represents the actual vehicle speed, and the preset discount coefficient table is a corresponding relationship table of vehicle speed difference and discount coefficient obtained through calibration.

[0021] Preferably, in the preset discount coefficient table, when ΔV ≤ 3 kph, the discount coefficient is equal to 0; when ΔV ≥ 12 kph, the discount coefficient is equal to 1; when 3 kph < ΔV < 12 kph, the discount coefficient increases as ΔV increases.

[0022] Preferably, the second slope K2 is obtained in the following way:

[0023] First use the formula: ΔQ = the braking energy recovery power capacity boundary at the previous moment - MbRgnTar to calculate the torque difference ΔQ;

[0024] Then use ΔQ to query the preset second slope table by interpolation to obtain the second slope K2.

[0025] Where the preset second slope table is a corresponding relationship table of torque difference and second slope obtained through calibration.

[0026] Preferably, the preset first slope K1 is equal to the maximum rate of chassis hydraulic replenishment. In the preset second slope table, when ΔQ ≤ 0, the second slope is equal to the maximum rate of chassis hydraulic replenishment; when ΔQ > 0, the second slope increases as ΔQ increases. The second slope can ensure that the braking energy recovery power capacity boundary is quickly discharged to 0 without obvious loss of vehicle braking force.

[0027] Preferably, the maximum rate of chassis hydraulic replenishment is 800 Nm / s, the value of T is 0.01 s, and the value of k max is 8000 Nm / s.

[0028] Preferably, if any of the conditions 1a to 1e is satisfied, it indicates that the braking energy recovery prohibition condition is satisfied; otherwise, it indicates that the braking energy recovery prohibition condition is not satisfied. Among them, condition 1a: The vehicle is operating in EV mode, the braking energy recovery prohibition condition was satisfied at the previous moment, and the actual vehicle speed at the current moment is less than the preset entry speed; condition 1b: The vehicle is operating in EV mode, the braking energy recovery prohibition condition was not satisfied at the previous moment, and the actual vehicle speed at the current moment is less than or equal to the preset exit speed; condition 1c: The current actual gear position GearAct is in N gear or in R gear; condition 1d: There is a failure in braking energy recovery; condition 1e: The engine is in the starting process.

[0029] Preferably, the preset entry speed is 10 kph, and the preset exit speed is 0 kph.

[0030] A braking energy recovery power capacity boundary calculation system for a P2 configuration vehicle according to the present invention includes a power controller (i.e., PCU), and the power controller is programmed to execute the above-mentioned braking energy recovery power capacity boundary calculation method.

[0031] The present invention provides a braking energy recovery power capacity boundary calculation method for a P2 configuration vehicle (with a dual-clutch DCT transmission) to obtain an accurate braking energy recovery power capacity boundary, which characterizes the true power's ability to respond to the maximum electric braking capacity of the chassis, providing a guarantee for achieving a relatively high level of braking energy recovery efficiency of the whole vehicle and avoiding braking safety risks. The chassis controller can preferentially distribute electric braking according to this power capacity boundary in combination with the depth of the braking pedal, so that the braking energy recovery efficiency of the whole vehicle reaches a relatively high level, significantly reducing the overall fuel consumption of the vehicle; at the same time, according to the supplementary ability of the chassis hydraulic pressure to the electric braking, reasonably handle the reduction and exit of the power capacity boundary to ensure that while the braking energy recovery efficiency of the whole vehicle reaches a relatively high level, the braking force of the whole vehicle is stable and braking safety risks are avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a working flow chart of the braking energy recovery system for a P2 architecture vehicle.

[0033] Figure 2 It is a connection schematic diagram of the hybrid power system for a P2 architecture vehicle.

[0034] Figure 3 It is a flow chart for calculating the braking energy recovery power capacity boundary in this embodiment.

[0035] Figure 4 It is a flow chart for obtaining the discount factor λ in this embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] As Figure 3As shown in the figure, the calculation method for the braking energy recovery power capacity boundary of the P2 configuration vehicle in this embodiment includes the following steps:

[0037] S1. Use the formula: Mer = Min(MotTqMin, ElecCpbyMin, TrsmCluTqMin) to calculate the total energy recovery power capacity boundary Mer, and then execute S2. Here, Min() represents the minimum operation, that is, Min(MotTqMin, ElecCpbyMin, TrsmCluTqMin) means taking the minimum value among MotTqMin, ElecCpbyMin, and TrsmCluTqMin. MotTqMin represents the maximum negative torque of the motor, ElecCpbyMin represents the maximum charging torque of the motor under the current battery SOC, and TrsmCluTqMin represents the maximum negative torque of the transmission and clutch.

[0038] S2. Use the formula: MbRgnMaxRaw = Mer * GearRatAct - CoastTqDmd to calculate the original value of the braking energy recovery power capacity boundary MbRgnMaxRaw (which is also the wheel-end value of the braking energy recovery power capacity boundary), and then execute S3. Here, GearRatAct represents the current gear ratio, and CoastTqDmd represents the coasting energy recovery torque.

[0039] S3. Use the formula: MbRgnMaxALL = MbRgnMaxRaw * λ to calculate the full power condition value MbRgnMaxALL of the braking energy recovery power capacity boundary, and then execute S4. Here, λ represents the discount factor, and 0 ≤ λ ≤ 1.

[0040] As Figure 4 shown, the steps to obtain the discount factor λ include:

[0041] The first step: Determine whether the vehicle is running in the EV mode (i.e., the pure electric mode). If so, execute the second step; otherwise (i.e., when the vehicle is running in the HEV mode), execute the third step.

[0042] The second step: Set the discount factor λ = 1, and then end.

[0043] The third step: Use the formula: Vname = 60 * π * D * n / 1000 * GearRatAct to calculate the nominal vehicle speed Vname, and then execute the fourth step. Here, D represents the wheel diameter, and n represents the idle target speed.

[0044] The fourth step: Use the formula: ΔV = VehSpd - Vname to calculate the vehicle speed difference ΔV. Here, VehSpd represents the actual vehicle speed.

[0045] Step 5: Use ΔV to query the preset discount coefficient table through interpolation to obtain the discount coefficient λ, and then end.

[0046] Among them, the preset discount coefficient table is a corresponding relationship table of vehicle speed difference and discount coefficient obtained through calibration. In the preset discount coefficient table, when ΔV ≤ 3 kph, the discount coefficient is equal to 0; when ΔV ≥ 12 kph, the discount coefficient is equal to 1; when 3 kph < ΔV < 12 kph, the discount coefficient increases as ΔV increases. Table 1 gives an example of a discount coefficient table.

[0047] Table 1

[0048] Vehicle speed difference ΔV (kph) 0 3 6 9 12 Discount factor λ 0 0 1 / 3 2 / 3 1

[0049] S4. Determine whether MbRgnAllwd = 1. If so, execute S5; otherwise (that is, when MbRgnAllwd = 0), execute S13. Among them, MbRgnAllwd represents the braking energy recovery flag bit. MbRgnAllwd = 1 means that the braking energy recovery prohibition condition is not satisfied (that is, the braking energy recovery condition is satisfied), and MbRgnAllwd = 0 means that the braking energy recovery prohibition condition is satisfied.

[0050] If any one of Condition 1a to Condition 1e is satisfied, it means that the braking energy recovery prohibition condition MbRgnAllwd = 0 is satisfied; otherwise, it means that the braking energy recovery prohibition condition MbRgnAllwd = 1 is not satisfied. Condition 1a: The vehicle is running in the EV mode, the braking energy recovery prohibition condition was satisfied at the previous moment, and the actual vehicle speed at the current moment is less than the preset entry vehicle speed (the preset entry vehicle speed in this embodiment is 10 kph); Condition 1b: The vehicle is running in the EV mode, the braking energy recovery prohibition condition was not satisfied at the previous moment, and the actual vehicle speed at the current moment is less than or equal to the preset exit vehicle speed (the preset exit vehicle speed in this embodiment is 0 kph); Condition 1c: The current actual gear position GearAct is in the N gear or in the R gear; Condition 1d: There is a braking energy recovery failure; Condition 1e: The engine is in the starting process.

[0051] S5. Determine whether the vehicle remains in a certain gear within the D gear (such as remaining in the 1st gear, 2nd gear, 3rd gear, 4th gear, 5th gear, etc.). If so, execute S6; otherwise, execute S7.

[0052] S6. Set MbRgnMax = MbRgnMaxALL, and then end. Among them, MbRgnMax represents the braking energy recovery power capacity boundary at the current moment.

[0053] S7. Determine whether the vehicle is in the process of switching between different gears within the D gear. If so, execute S8; otherwise, execute S11.

[0054] S8. Determine whether MbRgnTar > MbRgnMaxRawGearTar. If yes, execute S9; otherwise (i.e., when MbRgnTar ≤ MbRgnMaxRawGearTar), execute S10. Here, MbRgnTar represents the target torque for regenerative braking energy allocated by the chassis controller, and MbRgnMaxRawGearTar represents the boundary value of the regenerative braking power capacity of the target gear.

[0055] S9. Let MbRgnMax start from MbRgnTar + OffsetA and decrease to MbRgnMaxRawGearTar according to a preset first slope K1, and then end. Here, OffsetA represents the torque increment, OffsetA = T * k max , T represents a preset CAN signal period (taking 0.01 s in this embodiment), and k max represents the maximum rate of the target torque for regenerative braking energy allocated by the chassis controller (taking 8000 Nm / s in this embodiment). Then, in this embodiment, OffsetA = 80 Nm. The preset first slope K1 is equal to the maximum rate of chassis hydraulic replenishment (taking 800 Nm / s in this embodiment), that is, in this embodiment, K1 = 800 Nm / s.

[0056] S10. Let MbRgnMax = MbRgnTar + OffsetA until the gear shift is successful, and then let

[0057] MbRgnMax = MbRgnMaxRawGearTar, and then end.

[0058] S11. Determine whether the vehicle is in the process of shifting from D gear to N gear (corresponding to receiving the command that the shift lever gear is N from the TCU). If yes, execute S12; otherwise, end.

[0059] S12. Let MbRgnMax decrease from the regenerative braking power capacity boundary at the previous moment to 0 according to the second slope K2, and then end.

[0060] Here, the second slope K2 is obtained in the following way:

[0061] First, use the formula: ΔQ = the regenerative braking power capacity boundary at the previous moment - MbRgnTar to calculate the torque difference ΔQ.

[0062] Interpolate the preset second slope table using ΔQ to obtain the second slope K2. The preset second slope table is a correspondence table of torque difference and the second slope obtained through calibration. In the preset second slope table, when ΔQ ≤ 0, the second slope is equal to the maximum rate of chassis hydraulic replenishment (i.e., equal to 800 Nm / s), and when ΔQ > 0, the second slope increases as ΔQ increases. Table 2 gives an example of a second slope table.

[0063] Table 2

[0064] Torque difference ΔQ (Nm) 0 200 500 1000 1500 2000 Second slope K2 (Nm / s) 800 1000 1300 1800 2300 2800

[0065] S13. Set MbRgnMax = 0, and then end.

[0066] This embodiment also provides a braking energy recovery power capacity boundary calculation system for a P2 configuration vehicle, including a power controller (i.e., PCU), and the power controller is programmed to execute the above braking energy recovery power capacity boundary calculation method.

Claims

1. A method for calculating the braking energy recovery power capacity boundary of a P2 configuration vehicle, characterized in that Including: Using the formula: Mer = Min(MotTqMin, ElecCpbyMin, TrsmCluTqMin), calculate the total energy recovery power capacity boundary Mer; where Min( ) represents the minimum operation, MotTqMin represents the maximum negative torque of the motor, ElecCpbyMin represents the maximum charging torque of the motor under the current battery SOC, and TrsmCluTqMin represents the maximum negative torque of the transmission and clutch; Using the formula: MbRgnMaxRaw = Mer * GearRatAct - CoastTqDmd, calculate the original value of the braking energy recovery power capacity boundary MbRgnMaxRaw; where GearRatAct represents the current gear ratio and CoastTqDmd represents the coasting energy recovery torque; Using the formula: MbRgnMaxALL = MbRgnMaxRaw * λ, calculate the full power condition value MbRgnMaxALL of the braking energy recovery power capacity boundary; where λ represents the discount factor, 0 ≤ λ ≤ 1; If the vehicle remains in a certain gear within the D gear range, when the braking energy recovery prohibition condition is not met, set MbRgnMax = MbRgnMaxALL; where MbRgnMax represents the braking energy recovery power capacity boundary at the current moment; If the vehicle is in the process of switching between different gears in the D gear, then when MbRgnTar > MbRgnMaxRawGearTar and the braking energy recovery prohibition condition is not met, make MbRgnMax decrease from MbRgnTar + OffsetA as the starting point to MbRgnMaxRawGearTar at a preset first slope K1. When MbRgnTar ≤ MbRgnMaxRawGearTar and the braking energy recovery prohibition condition is not met, make MbRgnMax = MbRgnTar + OffsetA, and then make MbRgnMax = MbRgnMaxRawGearTar until the gear shift is successful; where MbRgnTar represents the braking energy recovery target torque allocated by the chassis controller, MbRgnMaxRawGearTar represents the braking energy recovery power capacity boundary value of the target gear, OffsetA represents the torque increment, OffsetA = T * k max , T represents a preset CAN signal period, k max represents the maximum rate of the braking energy recovery target torque allocated by the preset chassis controller; If the vehicle is in the process of shifting from D gear to N gear, when the braking energy recovery prohibition condition is not met, make MbRgnMax decrease from the braking energy recovery power capacity boundary at the previous moment to 0 according to the second slope K2; When the braking energy recovery prohibition condition is met, set MbRgnMax = 0.

2. The braking energy recovery power capacity boundary calculation method for a vehicle with a P2 configuration according to claim 1, characterized in that: The specific discount factor λ is as follows: When the vehicle is operating in the EV mode, λ = 1; When the vehicle is operating in the HEV mode, first use the formula: Vname = 60 * π * D * n / 1000 * GearRatAct, Calculate the nominal vehicle speed Vname, then use the formula: ΔV = VehSpd - Vname to calculate the vehicle speed difference ΔV, and finally use ΔV to query the preset discount factor table by interpolation to obtain the discount factor λ; where D represents the wheel diameter, n represents the idle target speed, VehSpd represents the actual vehicle speed, and the preset discount factor table is a corresponding relationship table of vehicle speed difference and discount factor obtained through calibration.

3. The braking energy recovery power capacity boundary calculation method for a vehicle with a P2 configuration according to claim 2, characterized in that: In the preset discount factor table, when ΔV ≤ 3 kph, the discount factor is equal to 0; when ΔV ≥ 12 kph, the discount factor is equal to 1; when 3 kph < ΔV < 12 kph, the discount factor increases as ΔV increases.

4. The braking energy recovery power capacity boundary calculation method for a vehicle with a P2 configuration according to claim 1, characterized in that: The second slope K2 is obtained in the following way: First use the formula: ΔQ = the braking energy recovery power capacity boundary at the previous moment - MbRgnTar to calculate the torque difference ΔQ; Then use ΔQ to query the preset second slope table by interpolation to obtain the second slope K2; Among them, the preset second slope table is a corresponding relationship table of torque difference and second slope obtained through calibration.

5. The method for calculating the braking energy recovery power capacity boundary of a vehicle with P2 configuration according to claim 4, wherein: The preset first slope K1 is equal to the maximum rate of chassis hydraulic replenishment; In the preset second slope table, when ΔQ ≤ 0, the second slope is equal to the maximum rate of chassis hydraulic replenishment, and when ΔQ > 0, the second slope increases as ΔQ increases.

6. The braking energy recovery power capacity boundary calculation method for a vehicle with a P2 configuration according to claim 5, wherein: The maximum rate of hydraulic replenishment of the chassis is 800 Nm / s, the value of T is 0.01 s, and the value of k max is 8000 Nm / s.

7. The method for calculating the braking energy recovery power capacity boundary of a vehicle with a P2 configuration according to any one of claims 1 to 6, characterized in that: If any one of conditions 1a to 1e is satisfied, it means that the braking energy recovery prohibition condition is satisfied, otherwise it means that the braking energy recovery prohibition condition is not satisfied; wherein, Condition 1a: The vehicle is operating in EV mode, the braking energy recovery prohibition condition was satisfied at the previous moment, and the actual vehicle speed at the current moment is less than the preset entry vehicle speed; Condition 1b: The vehicle is operating in EV mode, the braking energy recovery prohibition condition was not satisfied at the previous moment, and the actual vehicle speed at the current moment is less than or equal to the preset exit vehicle speed; Condition 1c: The current actual gear position GearAct is in N gear or in R gear; Condition 1d: There is a failure in braking energy recovery; Condition 1e: The engine is in the starting process.

8. The braking energy recovery power capacity boundary calculation method for a vehicle with a P2 configuration according to claim 7, characterized in that: The preset entry vehicle speed is 10 kph, and the preset exit vehicle speed is 0 kph.

9. A braking energy recovery power capacity boundary calculation system for a P2 configuration vehicle, including a power controller, characterized in that: The power controller is programmed to execute the calculation method according to any one of claims 1 to 8.

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