Control methods for dual-motor hybrid vehicles

Abstract

This invention provides a control method for a dual-motor hybrid vehicle. The method includes: acquiring the vehicle's operating mode; calculating the target power of the series drive battery when the vehicle is in series operation mode; performing a feedback control enable calculation for the target power of the series drive battery; calculating the feedback error of the target power of the series drive battery; calculating the integral part of the feedback of the target power of the series drive battery; and limiting the calculation results and upper and lower limits of the feedback control results for the target power of the series drive battery. The control method for a dual-motor hybrid vehicle of this invention effectively avoids the problem of the power battery charge failing to reach the control target for an extended period.

Description

Technical Field

[0001] This invention relates to the field of vehicle control technology, and more specifically, to a control method for a dual-motor hybrid vehicle. Background Technology

[0002] To address global demands for CO2 emission reduction, a dual-motor hybrid vehicle has been developed. This vehicle can operate in three modes: pure electric, series, and parallel, and can automatically switch modes according to driving conditions to achieve better overall vehicle fuel economy. The dual-motor hybrid powertrain mainly consists of an engine, a generator, and a drive motor.

[0003] In hybrid vehicles with a dual-motor structure, the vehicle enters series operation mode after the engine starts. In this mode, the engine drives a generator to produce electricity, which powers both the drive motor and the battery, or the engine drives the generator to produce electricity, which, along with the battery, powers the drive motor. To ensure the vehicle's fuel economy in series operation mode, the engine is controlled to operate within the optimal fuel economy curve. This optimal fuel economy curve is derived from the engine's universal characteristics, referencing the isopower line and the specific fuel consumption contour line. It can be seen that even the optimal fuel economy curve results in lower specific fuel consumption within a certain range; beyond this range, specific fuel consumption increases sharply. Therefore, the goal of series engine control is to ensure that the driver's needs are met while keeping the engine operating within the high-efficiency zone of the optimal fuel economy curve.

[0004] Since the engine drives the generator to generate electricity and simultaneously provides electrical energy to the drive motor, it involves the energy conversion of thermal energy into mechanical energy, mechanical energy into electrical energy, and electrical energy into mechanical energy. When calculating the driver's required power and the engine's required power, the efficiency of each assembly and the transmission efficiency are taken into account. The final electricity consumption and power generation may deviate due to factors such as the accuracy of efficiency and the response precision of the engine, generator, and drive motor, resulting in the power battery charge not reaching the control target for a long time. Summary of the Invention

[0005] The main objective of this invention is to provide a control method for a dual-motor hybrid vehicle that can effectively avoid the problem of the power battery failing to reach the control target for an extended period of time.

[0006] To achieve the above objectives, according to one aspect of the present invention, a control method for a dual-motor hybrid vehicle is provided, comprising:

[0007] Obtain vehicle operating mode;

[0008] Calculate the target power of the series drive battery when the vehicle is in series operating mode;

[0009] Perform target power feedback control enable calculation for series drive batteries;

[0010] Calculate the target power feedback error of the series drive battery;

[0011] Perform the integral calculation of the target power feedback of the series drive battery;

[0012] The calculation of the target power feedback control results for the series drive battery and the upper and lower limits are restricted.

[0013] Furthermore, the step of calculating the target power feedback integral of the series drive battery includes:

[0014] Perform a calculation to reset the previous integration result to zero;

[0015] Calculate the integral calculation flag;

[0016] Perform integral calculation and gain calculation;

[0017] The integral part of the target power feedback of the series drive battery under series drive conditions is obtained by performing integral calculation.

[0018] Furthermore, the step of performing the integral calculation gain includes:

[0019] Calculate the integral gain coefficient;

[0020] Calculate the gain zeroing factor;

[0021] When the actual power of the battery is in the same direction as the target power of the battery and the difference is within the preset range, and within the capability range of the power battery, the integral gain zeroing coefficient is set to 0; otherwise, it is set to 1.

[0022] Implement a delayed confirmation process for the integral gain zeroing strategy;

[0023] The gain is calculated by multiplying the gain coefficient by the gain zeroing coefficient and then integrating the results.

[0024] Furthermore, the step of calculating the target power of the series drive battery includes:

[0025] Calculate the initial power requirement of the engine;

[0026] Calculate whether the series high-load assist flag is set;

[0027] Calculate the superimposed power of series low and medium loads when the vehicle is in the case where the series high load assist indicator is not set.

[0028] Calculate the superimposed power of the series high load when the vehicle is in the position of the series high load assist sign;

[0029] Slope limiting is applied to the superimposed power of different loads in series;

[0030] Calculate the engine's required power and set a minimum limit.

[0031] Furthermore, the step of calculating whether the series high-load assist flag is set includes:

[0032] By comparing the engine's initial power demand and the battery's charge with the pre-set upper limit of the series economic zone power and the lower limit of the battery assist, it can be determined whether it is permissible to perform high-power discharge of the power battery for series assist.

[0033] Furthermore, the step of calculating the superimposed power of low loads in the series connection includes:

[0034] When the initial power demand of the engine is less than the preset lower limit of the series economic zone power, it is determined that the series load is in the low load zone. The superimposed power generation of the series low load zone is calculated by using the initial power demand of the engine in a one-dimensional lookup table, while taking into account the power battery charge.

[0035] When the power battery charge is greater than or equal to the power battery charging limit during driving, the series low load superimposed power is calculated by one-dimensional lookup table calculation of the engine initial demand power and the series low load superimposed power generation power * 0.

[0036] When the power battery charge is less than or equal to the power battery charging limit minus the hysteresis value, the series low load superimposed power is calculated as the engine initial demand power by a one-dimensional lookup table to obtain the series low load superimposed power generation power * 1.

[0037] When the initial power demand of the engine is higher than the preset lower limit of the series economic zone power and lower than the preset upper limit of the series economic zone power, the series load is determined to be in the medium load zone, and the SOC balance discharge power in the initial power demand of the engine is used as the adjustment power.

[0038] Furthermore, the step of calculating the superimposed power of the series-connected large loads includes:

[0039] Series high-load assist battery assist power = Min(Engine initial demand power - Preset series economic zone power limit, power battery discharge capacity);

[0040] The discharge capacity of the power battery = the discharge capacity of the power battery itself - the power of accessories - the speed regulation reserve power. The speed regulation reserve power is related to the discharge capacity of the power battery itself, the engine speed, and the actual power generation of the generator.

[0041] Furthermore, the step of calculating whether the series high-load assist flag is set includes:

[0042] Determine whether the engine's initial power demand is greater than or equal to the upper limit of the series economic zone power;

[0043] When the initial power demand of the engine is greater than or equal to the upper limit of the series economic zone power, the power battery assist is activated.

[0044] Determine whether the power battery charge is greater than or equal to the battery assist lower limit plus the hysteresis value;

[0045] When the power battery charge is greater than or equal to the battery assist lower limit plus the hysteresis value, the power battery has assist capability, and at this time the series high load assist flag is set to position 1.

[0046] Furthermore, the step of calculating whether the series high-load assist flag is set also includes:

[0047] When the initial power demand of the engine is less than or equal to the upper limit of the series economic zone power, determine whether the initial power demand of the engine is less than or equal to the upper limit of the series economic zone power minus the hysteresis value.

[0048] When the initial power demand of the engine is less than or equal to the upper limit of the series economic zone power minus the hysteresis value, it is determined that the engine is already working in the high-efficiency zone and does not require the power battery to assist, and the series high-load assist flag is set to 0.

[0049] When the initial power demand of the engine is greater than the upper limit of the series economic zone power minus the hysteresis value, the original state of the series high load assist flag is maintained, and the initial power demand of the engine is further judged to be greater than or equal to the upper limit of the series economic zone power.

[0050] Furthermore, the step of calculating whether the series high-load assist flag is set also includes:

[0051] When the power battery charge is less than the battery assist lower limit plus the hysteresis value, determine whether the power battery charge is less than or equal to the battery assist lower limit.

[0052] When the power battery charge is less than or equal to the battery assist lower limit, it is considered that the power battery SOC is too low to provide assistance, and the series high load assist flag is set to 0.

[0053] When the power battery charge is greater than the lower limit of battery assist, the original state of the series high load assist flag remains unchanged, and the power battery charge is further judged to be greater than or equal to the lower limit of battery assist plus the hysteresis value.

[0054] The control method for a dual-motor hybrid vehicle using the technical solution of this invention includes: acquiring the vehicle's operating mode; calculating the target power of the series drive battery when the vehicle is in series operating mode; performing a series drive battery target power feedback control enable calculation; performing a series drive battery target power feedback error calculation; performing a series drive battery target power feedback integral calculation; and limiting the calculation and upper and lower limits of the series drive battery target power feedback control result. In the control method for a dual-motor hybrid vehicle of this application, after the engine successfully starts and enters the series operating mode, when calculating the engine's required power, factors such as the driver's required power and battery charge need to be considered. When idling or driving with low throttle, if the driver's required power is low, a certain amount of power generation will be added to increase the engine load based on the driver's required power. When driving with high throttle, if the driver's required power is high, the power battery will assist to some extent, and the power generation will be reduced by a certain amount based on the driver's required power to reduce the engine load. Simultaneously, the power battery charge is considered; the control target for the power battery charge is generally set to the median battery charge value. When the power battery charge is high, it can be appropriately discharged. When the battery charge is low, it can be charged appropriately, and the charge can be maintained when it is near the median value. During the regulation of the actual battery power, the deviation between the target battery power and the actual battery power is used for feedback control. After the deviation between the target battery power and the actual battery power reaches the preset range, the actual battery power is gradually moved closer to the target battery power on one side using an integral method. This can gradually reduce the deviation between the target battery power and the actual battery power, effectively reduce the fluctuation of the feedback control target caused by the fluctuation of the engine operating point during speed regulation, prevent the condition from repeatedly jumping when comparing the actual battery power and the target battery power, and control the actual battery power to quickly reach the target battery power, which is conducive to maintaining the battery balance of the hybrid vehicle. Attached Figure Description

[0055] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0056] Figure 1 A powertrain structure block diagram of a dual-motor hybrid vehicle according to an embodiment of the present invention is shown;

[0057] Figure 2 A flowchart illustrating the engine power request calculation process for a dual-motor hybrid vehicle under series drive conditions, according to an embodiment of the present invention, is shown.

[0058] Figure 3 A flowchart illustrating the calculation of the series high-load assist flag in the series drive condition of a dual-motor hybrid vehicle according to an embodiment of the present invention is shown.

[0059] Figure 4 A flowchart illustrating the calculation process of the series drive battery target power feedback control for a dual-motor hybrid vehicle under series drive conditions, according to an embodiment of the present invention, is shown.

[0060] Figure 5 A flowchart illustrating the calculation of the target power feedback integral part of the series drive battery in the series drive condition of a dual-motor hybrid vehicle according to an embodiment of the present invention is shown.

[0061] Explanation of reference numerals in the attached diagram: 1. Engine management system; 2. Engine; 3. Generator control unit; 4. Generator inverter; 5. Generator; 6. Drive motor control unit; 7. Drive motor inverter; 8. Drive motor; 9. Power battery; 10. Battery management system; 11. Vehicle control unit; 12. Wheel; 13. Clutch; 14. Reduction gear. Detailed Implementation

[0062] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0063] like Figure 1 As shown, the present invention provides a powertrain for a dual-motor hybrid vehicle, including an engine management system 1, an engine 2, a generator control unit 3, a generator inverter 4, a generator 5, a drive motor control unit 6, a drive motor inverter 7, a drive motor 8, a power battery 9, a battery management system 10, a vehicle control unit 11, wheels 12, a clutch 13, and a reduction gear 14.

[0064] Engine 2 and generator 5 are connected by a gear pair. Engine 2 can be started by generator 5. When clutch 13 is disengaged, engine 2 does not directly drive the vehicle. Instead, engine 2 drives generator 5 to generate electricity to provide energy for power battery 9 or drive motor 8. Drive motor 8 drives the vehicle. When clutch 13 is engaged, the torque of engine 2 is transmitted to wheels 12 through clutch 13 and reduction gear 14. Engine 2 and drive motor 8 can drive the hybrid vehicle together.

[0065] The aforementioned engine management system 1, generator control unit 3, drive motor control unit 6, battery management system 10, and vehicle control unit 11 constitute the main electronic control system of the power domain of the dual-motor hybrid vehicle of the present invention.

[0066] The main operating modes of dual-motor hybrid vehicles include the following:

[0067] When the vehicle is parked and the engine 2 is off, the clutch 13 is disengaged, and the vehicle control unit 11 stops sending fuel injection commands and related torque commands. When the generator 5 starts the engine 2 and tows the engine 2 to a certain speed, the vehicle control unit 11 sends fuel injection commands and related torque commands, and the EMS controls the fuel injection and ignition of the engine 2. At this time, the clutch 13 is disengaged. When the engine 2 stops, the vehicle control unit 11 stops sending fuel injection commands and related torque commands, and the EMS controls the fuel cut-off and shutdown of the engine 2. At this time, the clutch 13 is disengaged.

[0068] In pure electric mode, when the power battery has sufficient charge and the vehicle speed and the torque required by the driver are relatively low, the engine 2 stops, and the vehicle is driven by the drive motor 8, whose energy comes entirely from the power battery 9.

[0069] In series mode, when the vehicle speed increases or the driver requires a large torque, the engine 2 generates electricity through the generator 5, which, together with the power battery 9, serves as the energy source for the drive motor 8, or provides electricity to the drive motor 8 while charging the power battery.

[0070] In parallel mode, when the vehicle speed continues to increase and the torque demanded by the driver decreases, the control clutch 13 engages, the engine 2 directly drives the vehicle, and the generator 5 generates electricity based on the power battery charge and engine load. When the torque demanded by the driver is greater than the upper limit of the engine's economic zone or the engine 2 responds slowly, the drive motor 8 provides assistance.

[0071] In the recovery mode, when the vehicle is in motion, the vehicle control unit 11 calculates the coasting energy recovery torque and the braking energy recovery torque requested by the ESP (Electronic Stability Program) based on the vehicle speed, and controls the engine 2 to be in the power generation or fuel cut-off state, and the drive motor 8 performs energy recovery and power generation according to the energy recovery torque.

[0072] In the hybrid vehicle with a dual-motor structure of this invention, after the engine 2 successfully starts and enters the series operating mode, the calculation of the engine's required power needs to consider factors such as the driver's required power and the battery charge. When idling or driving with low throttle, the driver's required power is relatively low, so a certain amount of power generation is added to increase the engine load on top of the driver's required power. When driving with high throttle, the driver's required power is relatively high, so the power battery 9 provides some assistance, reducing the power generation to decrease the engine load based on the driver's required power. When performing the linkage control of engine 2 and power battery 9, the power battery charge is also considered. The control target for the power battery charge is generally set at the median battery charge level. When the power battery charge is high, it can be discharged appropriately; when the power battery charge is low, it can be charged appropriately; and when it is near the median value, the charge level is maintained.

[0073] By taking into account the relative relationship between the driver's power demand and the efficient zone of the engine's optimal economic curve, as well as the power battery charge, the power output or power compensation between engine 2 and power battery 9 can be adjusted according to the relative relationship between the driver's power demand and the efficient zone of the engine's optimal economic curve, and the power battery charge. This will keep the engine operating point as close as possible to the efficient zone of the engine's optimal economic curve, while improving the working performance and efficiency of power battery 9, thereby achieving good economic efficiency.

[0074] See also Figures 2 to 4 As shown, the present invention also provides a control method for a dual-motor hybrid vehicle, comprising: acquiring the vehicle operating mode; when the vehicle is in series operating mode, proceeding to step S301 to calculate the target power of the series drive battery; step S302 to perform a calculation for enabling the feedback control of the target power of the series drive battery; step S303 to calculate the feedback error of the target power of the series drive battery; step S304 to calculate the integral part of the feedback of the target power of the series drive battery; and step S305 to limit the calculation results and upper and lower limits of the feedback control of the target power of the series drive battery. Through the above steps, the battery power portion of the engine's required power after feedback control can be obtained.

[0075] The control method for the dual-motor hybrid vehicle of this application, after the engine 2 successfully starts and enters the series working mode, needs to consider factors such as the driver's power demand and battery charge when calculating the engine's power demand. When idling or driving with low throttle, the driver's power demand is relatively low, so a certain amount of power generation is added to increase the engine load on top of the driver's power demand. When driving with high throttle, the driver's power demand is relatively high, so the power battery 9 provides some assistance, reducing the power generation to decrease the engine load on top of the driver's power demand. Simultaneously, the power battery charge is considered; the control target for the power battery charge is generally set to the median battery charge value. When the power battery charge is high, it can be appropriately discharged. When the battery charge is low, it can be charged appropriately, and when it is near the median value, the charge can be maintained. During the regulation of the actual battery power, the deviation between the target battery power and the actual battery power is used for feedback control. After the deviation between the target battery power and the actual battery power reaches the preset range, the actual battery power is gradually moved closer to the target battery power on one side using an integral method. This can gradually reduce the deviation between the target battery power and the actual battery power, effectively reduce the fluctuation of the feedback control target caused by the fluctuation of the engine operating point during speed regulation, prevent the condition from repeatedly jumping when comparing the actual battery power and the target battery power, and control the actual battery power to quickly reach the target battery power, which is conducive to maintaining the charge balance of the hybrid vehicle.

[0076] In this embodiment, in step S301, calculating the target power of the series drive battery, the target power of the series drive battery = engine demand power - (driver demand power + accessory power). The engine demand power includes two parts: one part is the sum of the driver demand power and accessory power, and the other part is the target battery power that satisfies the SOC balance of the power battery. The other part is obtained by subtracting one part from the engine demand power. In this way, the engine demand power can be correlated with the driver demand power, accessory power, and the target power of the series drive battery, improving the accuracy of power calculation. After determining the engine demand power, the driver demand power can be determined based on the relative relationship between the driver demand power and the high-efficiency zone of the engine's optimal economic curve. Thus, while ensuring that the engine operating point is controlled as much as possible within the high-efficiency zone of the engine's optimal economic curve, the target battery power can be determined, and then the battery charge can be controlled based on the determined target battery power.

[0077] In step S302, the calculation of the enable for the series drive battery target power feedback control, the main requirement for battery target power feedback control in the series drive mode is steady-state operation, where the actual battery power is controlled to reach the target battery power under stable engine load. First, a delay confirmation process is performed each time the series mode is entered to ensure that the engine speed regulation is relatively stable before feedback control is implemented. When the series mode is entered and the engine operating point is stable, feedback control is not performed during warm-up when the power battery SOC is within the normal range. However, feedback control is implemented when the power battery SOC is below the battery assist lower limit or above the forced discharge threshold to maximize the warm-up effect.

[0078] In step S303, the calculation of the target power feedback error of the series drive battery is performed. The target power feedback error of the series drive battery = target power of the series drive battery - actual battery power. The actual battery power = actual battery voltage * actual battery current / 1000 (units are uniformly in kilowatts). The actual battery voltage and actual battery current are reported by the battery controller (BMS). Through this method, the deviation value and direction between the target battery power and the actual battery power can be determined, thus facilitating the adjustment of the actual battery power. By adjusting the battery charge, the actual battery power can quickly approach and reach the target battery power, allowing the battery charge to quickly reach the control target.

[0079] In step S304, the step of calculating the integral part of the target power feedback of the series drive battery is performed by accumulating the target power feedback error of the series drive battery and the integral gain. The integral gain coefficient is calculated by looking up the target power feedback error of the series drive battery in one dimension.

[0080] In step S304, the calculation and upper / lower limit restriction of the target power feedback control result of the series drive battery involves limiting the slope of the integral part of the target power feedback of the series drive battery and limiting the target feedback control result of the series drive battery with the power battery capacity to ensure that its change is gradual and within a reasonable range. The target feedback control result of the series drive battery = Max(Min(power battery discharge capacity (positive sign), target power of the series drive battery + integral part of the target power feedback of the series drive battery (after slope limitation)), power battery charging capacity (negative sign)).

[0081] As can be seen from the control method described above, in this embodiment, during the calculation of the target power of the series drive battery, it is necessary to first calculate the engine power requirement under the series drive condition, referring to [reference needed]. Figure 2 As shown, the engine power requirement under series drive conditions can be calculated using the following steps:

[0082] Step S101: Calculate the initial power demand of the engine. Initial power demand of the engine = Driver's power demand + Accessory power + Max(Forced generation power, SOC balance charging power) - Max(Forced discharge power, SOC balance discharge power), where forced generation power, SOC balance charging power, forced discharge power, and SOC balance discharge power are all positive values. Specifically, driver's power demand = Driver's required torque * Drive motor speed / Final drive ratio / 9550. Finally, considering the drive motor efficiency, the above mechanical power is converted into electrical power. Driver's required torque is calculated from a two-dimensional lookup table based on accelerator pedal opening and vehicle speed. Drive motor speed is reported by drive motor controller 6. Accessory power = DC-DC output power + Air conditioning power. DC-DC output power is calculated from DC-DC output voltage and current, and both DC-DC output voltage and current are reported by the DC-DC controller as electrical power. The median battery charge level is set based on the battery temperature and vehicle speed. An upward shift of this median yields the upper limit of the battery's driving charge, and a downward shift yields the lower limit of the battery's assist charge. The forced generation threshold is calculated as the lower limit of the battery's assist charge minus the hysteresis value. When the battery charge is less than or equal to the forced generation threshold, the forced generation power is calculated using a one-dimensional lookup table of the difference between the battery charge and the forced generation threshold. Under normal circumstances, the battery charge is controlled between the lower assist limit and the upper limit of the driving charge, and the forced generation power is generally 0. The SOC (State of Charge) balancing charging power is calculated using a one-dimensional lookup table of the difference between the battery charge and the median, with the same sign as the forced generation power. Similarly, the forced discharge threshold is calculated as the upper limit of the battery's driving charge plus the hysteresis value. When the battery charge is greater than or equal to the forced discharge threshold, the forced discharge power is calculated using a one-dimensional lookup table of the difference between the battery charge and the forced discharge threshold. Under normal circumstances, the battery charge is controlled between the lower assist limit and the upper limit of the driving charge, and the forced discharge power is generally 0. The SOC (State of Charge) balanced discharge power is calculated from the difference between the battery charge and the median value using a one-dimensional lookup table, and the sign is the same as the forced discharge power. The battery charge and temperature are reported by the battery management system (BMS).

[0083] Step S102: Calculate whether the series high-load assist flag is set. Use the engine's initial power demand and the power battery's charge level to compare with the pre-set upper limit of the series economic zone power and the lower limit of the battery assist to determine whether high-power discharge of the power battery for series assist is permitted. After determining whether high-power discharge of the power battery for series assist is permitted, the result can be used to determine whether the series high-load assist flag is set, thereby determining whether to use the power battery 9 for series assist.

[0084] Step S103: When the vehicle is in a series high-load assist position without being set (the result of whether it is set in step S102 is "no"), the series low-load superimposed power is calculated. When the initial engine demand power is less than the preset lower limit of the series economic zone power, the series load is considered to be in the low-load zone. At this time, the engine load should be increased as much as possible. Therefore, the series low-load zone superimposed power generation is calculated by using the initial engine demand power in a one-dimensional lookup table. At the same time, the power battery charge is considered. When the power battery charge is >= the upper limit of the power battery driving charge, the series low-load superimposed power = the series low-load zone superimposed power generation calculated by the initial engine demand power in a one-dimensional lookup table * 0; when the power battery charge is <= the upper limit of the power battery driving charge - the hysteresis value, the series low-load superimposed power = the series low-load zone superimposed power generation calculated by the initial engine demand power in a one-dimensional lookup table * 1. When the battery charge correction coefficient for the series low-load zone superimposed power generation switches between 0 and 1, a transition processing is required. When the initial power demand of the engine is higher than the preset lower limit of the series economic zone power and lower than the preset upper limit of the series economic zone power, the series load is considered to be in the medium load zone. The medium load relies only on the SOC balance discharge power in the initial power demand of the engine as the adjustment power. Finally, the engine power demand in the medium and low load zone = the initial power demand of the engine + the initial power demand of the engine. The superimposed power generation in the series low load zone is calculated by one-dimensional lookup table * the power correction coefficient. The superimposed power generation in the series low load zone is calculated by one-dimensional lookup table to ensure that the superimposed power in the medium load zone is 0.

[0085] Step S104: When the vehicle is in the series high-load assist position (the result of whether it is set in step S102 is "yes"), the series high-load superimposed power is calculated. Series high-load assist battery assist power = Min(Engine initial demand power - Pre-set series economic zone power limit, power battery discharge capacity), power battery discharge capacity = Power battery's own discharge capacity - Accessory power - Speed ​​regulation reserve power. The speed regulation reserve power is related to the power battery's own discharge capacity, engine speed, and the actual generator output power.

[0086] Step S105 involves limiting the slope of the superimposed power of different loads in series to ensure that the superimposed power of low loads in series and the superimposed power of high loads in series change smoothly after being superimposed with the initial power demand of the engine, so as not to affect the NVH of the whole vehicle.

[0087] Step S106: Calculate the engine power demand and set a minimum limit. Engine power demand = Max(initial engine power demand + slope of power superimposed by different loads in series (after limitation) + auxiliary power + Max(forced generation power, SOC balance charging power) - Max(forced discharge power, SOC balance discharge power) + superimposed power of low and medium loads in series). This ensures that when the driver switches from driving off the throttle to a condition with lower driver power demand or recovery mode, engine 2 can still generate power at a certain load without interrupting fuel supply, thereby improving fuel economy.

[0088] See also Figure 3 As shown, according to an embodiment of the present invention, a method for calculating the series high-load assist flag in the series drive condition of a dual-motor hybrid vehicle is provided, comprising the following steps:

[0089] After calculating the initial power demand of the engine in step S101, the initial power demand of the engine can be obtained, and then the calculation of the series high-load assist flag for series drive conditions can proceed. In this embodiment, during the calculation of the series high-load assist flag for series drive conditions, step S201 is first entered to determine whether the initial power demand of the engine is greater than or equal to the upper limit of the series economic zone power. When the initial power demand of the engine is greater than or equal to the upper limit of the series economic zone power, the power battery 9 needs to assist in order to ensure that the engine operating point is in the high-efficiency zone. Then, step S202 is entered to determine whether the power battery charge is greater than or equal to the lower limit of battery assist plus the hysteresis value. When the power battery charge is greater than or equal to the lower limit of battery assist plus the hysteresis value, the power battery 9 has the assist capability from the SOC balance perspective. At this time, step S205 is entered to set the series high-load assist flag to 1.

[0090] When the initial power demand of the engine is less than or equal to the upper limit of the series economic zone power, the process proceeds to step S203, where it is necessary to further determine whether the initial power demand of the engine is less than or equal to the upper limit of the series economic zone power minus the hysteresis value. If the initial power demand of the engine is less than or equal to the upper limit of the series economic zone power minus the hysteresis value, it is considered that the engine 2 is already operating in the high-efficiency zone and does not require the assistance of the power battery 9, and the process proceeds to step S206, where the series high-load assistance flag is set to 0. However, when the initial power demand of the engine is greater than the upper limit of the series economic zone power minus the hysteresis value, the original state of the series high-load assistance flag is maintained, and the process returns to step S201 to continue determining whether the initial power demand of the engine is greater than or equal to the upper limit of the series economic zone power.

[0091] When the battery charge is less than the battery assist lower limit plus the hysteresis value, the process proceeds to step S204, where it needs to further determine whether the battery charge is less than or equal to the battery assist lower limit. If the battery charge is less than or equal to the battery assist lower limit, it is considered that the battery SOC is too low to provide assistance, and the series high load assist flag is set to 0. If the battery charge is greater than the battery assist lower limit, the series high load assist flag remains unchanged, and the process returns to step S201 to continue determining whether the battery charge is greater than or equal to the battery assist lower limit plus the hysteresis value.

[0092] See also Figure 5 As shown, step S304, the specific steps for calculating the target power feedback integral of the series drive battery, include:

[0093] First, the previous integral result is cleared and calculated (step S401) to ensure that each integral calculation is performed when the engine operating point is relatively stable and is not affected by the previous calculation result. Therefore, the original integral part is cleared when the series drive battery target power feedback control enable switches from 0 to 1. That is, the hybrid vehicle re-enters the series mode and starts integral calculation after working stably for a certain period of time.

[0094] Next, the integral calculation flag is calculated (step S402). When the feedback error of the target power of the series drive battery is less than a certain value, that is, the deviation between the target value and the actual value is within a certain range, it is considered to have entered the integral action range. At the same time, the integral calculation flag is set to 1 when the target power feedback control of the series drive battery is enabled.

[0095] Next, the integral gain is calculated (step S403). The integral gain is divided into two parts. One part, the integral gain coefficient, is calculated using a one-dimensional lookup table of the feedback error of the series drive battery target power. The other part is the gain zeroing coefficient. To reduce the fluctuation of the feedback control target caused by the fluctuation of the engine operating point during speed regulation, the integral gain zeroing coefficient is set to 0 when the actual battery power and the battery target power are in the same direction and the difference is within a certain range, and within the capability of the power battery. Otherwise, it is set to 1. The integral gain zeroing strategy performs a delayed confirmation process to prevent repeated condition jumps when comparing the direction of the actual battery power and the battery target power. The integral gain is obtained by multiplying the gain coefficient and the gain zeroing coefficient. When the integral gain is 0, the integral calculation is paused, which achieves the control target and prevents fluctuations in the integral part of the feedback of the series drive battery target power.

[0096] Next, perform integral calculation (step S404). After the integral calculation flag is set to 1, start multiplying the target power feedback error of the series drive battery with the integral gain and then accumulating it over time to obtain the integral part of the target power feedback of the series drive battery under series drive conditions.

[0097] Finally, upper and lower limits for integral calculation and slope limitation are set (step S405). The integral calculation in step S404 yields the feedback integral portion of the target power of the series drive battery under series drive conditions. Upper and lower limits are set for this integral portion. The integral portion is adjusted to ensure that the deviation between the target power and the actual power of the series drive battery is within a certain range. If the deviation exceeds a certain range, it is considered that a steady-state condition has not been reached or that there is a significant deviation in the assembly response accuracy, indicating that the feedback control integral is not in effect. Setting upper and lower limits determines the effective range of the integral portion, and slope limitation ensures that the integral portion is smoothly superimposed on the target power of the series drive battery.

[0098] After the engine power demand is calculated, the engine speed request in series mode is obtained by one-dimensional lookup table of power and speed. The torque request of engine 2 in series mode is obtained by power (kW) * 9550 / engine speed request. Finally, the HCU controls engine 2 to operate at the corresponding operating point by sending torque and speed braking control.

[0099] The control method described above is applicable to the control device of a dual-motor hybrid vehicle equipped with an engine 2, a generator 5, and a drive motor 8.

[0100] This invention has the following advantages: In a dual-motor hybrid vehicle consisting of an engine 2, a generator 5, and a drive motor 8, under non-warm-up conditions in series mode, the relative relationship between the driver's power demand and the efficient zone of the engine's optimal economic curve, as well as the battery charge, is comprehensively considered to control the engine's operating point as close as possible to the efficient zone of the engine's optimal economic curve, thereby achieving good fuel economy. Furthermore, feedback control is implemented considering the battery's target power and actual battery power to ensure that the battery charge can quickly reach the control target.

[0101] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0102] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0103] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control method for a dual-motor hybrid vehicle, characterized in that, include: Obtain vehicle operating mode; Calculate the target power of the series drive battery when the vehicle is in series operating mode; Perform target power feedback control enable calculation for series drive batteries; Calculate the target power feedback error of the series drive battery; Perform the integral calculation of the target power feedback of the series drive battery; The calculation and upper and lower limits of the target power feedback control results for the series drive battery are restricted. The steps for calculating the integral part of the target power feedback of the series drive battery include: Perform a calculation to reset the previous integration result to zero; Calculate the integral calculation flag; Perform integral calculation and gain calculation; The integral part of the target power feedback of the series drive battery under series drive conditions is obtained by performing integral calculation. The steps for calculating the target power of the series drive battery include: Calculate the initial power requirement of the engine; Calculate whether the series high-load assist flag is set; Calculate the superimposed power of series low and medium loads when the vehicle is in the case where the series high load assist indicator is not set. Calculate the superimposed power of the series high load when the vehicle is in the position of the series high load assist sign; Slope limiting is applied to the superimposed power of different loads in series; Calculate the engine's required power and set a minimum limit.

2. The control method for a dual-motor hybrid vehicle according to claim 1, characterized in that, The steps for performing integral calculation and gain calculation include: Calculate the integral gain coefficient; Calculate the gain zeroing factor; When the actual power of the battery is in the same direction as the target power of the battery and the difference is within the preset range, and within the capability range of the power battery, the integral gain zeroing coefficient is set to 0; otherwise, it is set to 1. Implement a delayed confirmation process for the integral gain zeroing strategy; The gain is calculated by multiplying the gain coefficient by the gain zeroing coefficient and then integrating the results.

3. The control method for a dual-motor hybrid vehicle according to claim 1, characterized in that, The steps for calculating whether the series high-load assist flag is set include: By comparing the engine's initial power demand and the battery's charge with the pre-set upper limit of the series economic zone power and the lower limit of the battery assist, it can be determined whether it is permissible to perform high-power discharge of the power battery for series assist.

4. The control method for a dual-motor hybrid vehicle according to claim 1, characterized in that, The steps for calculating the superimposed power of low loads in a series connection include: When the initial power demand of the engine is less than the preset lower limit of the series economic zone power, it is determined that the series load is in the low load zone. The superimposed power generation of the series low load zone is calculated by using the initial power demand of the engine in a one-dimensional lookup table, while taking into account the power battery charge. When the power battery charge is greater than or equal to the power battery charging limit during driving, the series low load superimposed power is calculated as the engine initial demand power by a one-dimensional lookup table to obtain the series low load superimposed power generation power * 0. When the power battery charge is less than or equal to the power battery charging limit minus the hysteresis value, the series low load superimposed power is calculated as the engine initial demand power by a one-dimensional lookup table to obtain the series low load superimposed power generation * 1. When the initial power demand of the engine is higher than the preset lower limit of the series economic zone power and lower than the preset upper limit of the series economic zone power, the series load is determined to be in the medium load zone, and the SOC balance discharge power in the initial power demand of the engine is used as the adjustment power.

5. The control method for a dual-motor hybrid vehicle according to claim 1, characterized in that, The steps for calculating the superimposed power of series-connected large loads include: Series high-load booster battery booster power = Min (engine initial power demand - pre-set series economic zone power limit, power battery discharge capacity). The discharge capacity of the power battery = the discharge capacity of the power battery itself - the power of accessories - the speed regulation reserve power. The speed regulation reserve power is related to the discharge capacity of the power battery itself, the engine speed, and the actual power generation of the generator.

6. The control method for a dual-motor hybrid vehicle according to claim 1, characterized in that, The steps for calculating whether the series high-load assist flag is set include: Determine whether the engine's initial power demand is greater than or equal to the upper limit of the series economic zone power; When the initial power demand of the engine is greater than or equal to the upper limit of the series economic zone power, the power battery assist is activated. Determine whether the power battery charge is greater than or equal to the battery assist lower limit plus the hysteresis value; When the power battery charge is greater than or equal to the battery assist lower limit plus the hysteresis value, the power battery has assist capability, and at this time the series high load assist flag is set to position 1.

7. The control method for a dual-motor hybrid vehicle according to claim 6, characterized in that, The step of calculating whether the series high-load assist flag is set also includes: When the initial power demand of the engine is less than or equal to the upper limit of the series economic zone power, determine whether the initial power demand of the engine is less than or equal to the upper limit of the series economic zone power minus the hysteresis value. When the initial power demand of the engine is less than or equal to the upper limit of the series economic zone power minus the hysteresis value, it is determined that the engine is already working in the high-efficiency zone and does not require the power battery to assist, and the series high-load assist flag is set to 0. When the initial power demand of the engine is greater than the upper limit of the series economic zone power minus the hysteresis value, the original state of the series high load assist flag is maintained, and the initial power demand of the engine is further judged to be greater than or equal to the upper limit of the series economic zone power.

8. The control method for a dual-motor hybrid vehicle according to claim 7, characterized in that, The step of calculating whether the series high-load assist flag is set also includes: When the power battery charge is less than the battery assist lower limit plus the hysteresis value, determine whether the power battery charge is less than or equal to the battery assist lower limit. When the power battery charge is less than or equal to the battery assist lower limit, it is considered that the power battery SOC is too low to provide assistance, and the series high load assist flag is set to 0. When the power battery charge is greater than the lower limit of battery assist, the original state of the series high load assist flag remains unchanged, and the power battery charge is further judged to be greater than or equal to the lower limit of battery assist plus the hysteresis value.

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