Method for determining starting and stopping conditions of a hybrid vehicle

Abstract

The present invention provides a method for determining start-stop conditions of a hybrid vehicle. The method for determining start-stop conditions of the hybrid vehicle includes: obtaining the time and corresponding vehicle speed of a specific cycle condition; judging the working mode of the vehicle according to the obtained vehicle speed; when the working mode of the vehicle is a series mode, determining a superimposed charging power according to an NVH weight coefficient S1 and an economy weight coefficient S2; sequentially finding working points with the highest, second highest, ... overall efficiency according to the determined superimposed charging power, extracting the engine demand power corresponding to each working point, and accumulating the engine power energy for each point found until the accumulated energy ≥ total driving demand energy + DCDC energy consumption + starting engine energy consumption * number of starting times; determining the starting conditions of the series mode according to the marked point power of the series mode. The method for determining start-stop conditions of the hybrid vehicle according to the present invention can effectively optimize fuel consumption under different conditions and improve the working performance of the vehicle.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle control, and in particular, to a method for determining start-stop conditions of a hybrid vehicle. Background Art

[0002] To meet the global demand for carbon dioxide emission reduction, a hybrid vehicle has been developed. This vehicle can operate in three working modes, including pure electric mode, series mode, and parallel mode, and can automatically switch modes according to the vehicle driving conditions to achieve better overall vehicle economy. The dual-motor hybrid powertrain mainly consists of an engine, a generator, and a drive motor.

[0003] For a hybrid vehicle with a dual-motor structure, after the engine starts, the vehicle enters the series working mode. At this time, the engine drives the generator to generate electricity to provide energy for the drive motor and the power battery, or the engine drives the generator to generate electricity and the power battery together to provide energy for the drive motor. In order to improve the working performance of the hybrid vehicle and reduce the working fuel consumption, optimization can be carried out from the aspect of start-stop control.

[0004] Currently, for the existing start-stop control methods, in addition to the rule-based control method, generally, the equivalent fuel consumption minimum method based on the equivalent factor is more widely used. However, the optimization advantage of the corresponding working condition fuel consumption is not obvious, and in addition, multi-performance comprehensive optimization cannot be carried out, which may cause adverse effects on NVH, drivability, etc. at certain moments. Summary of the Invention

[0005] The main object of the present invention is to provide a method for determining start-stop conditions of a hybrid vehicle, which can effectively optimize the fuel consumption under different working conditions and improve the working performance of the vehicle.

[0006] To achieve the above object, according to one aspect of the present invention, there is provided a method for determining start-stop conditions of a hybrid vehicle, including:

[0007] Obtain the time of a specific cycle working condition and the corresponding vehicle speed;

[0008] Judge the working mode of the vehicle according to the obtained vehicle speed;

[0009] When the working mode of the vehicle is the series mode, determine the superimposed charging power according to the NVH weight coefficient S1 and the economic weight coefficient S2;

[0010] According to the determined superimposed charging power, sequentially find the working points with the highest, second-highest,... total efficiency, extract the engine demand power corresponding to each working point, and accumulate the energy of the engine power every time a point is found;

[0011] For each additional dot marked in series mode, the energy at this power point is accumulated once until the accumulated energy ≥ total driving demand energy + DCDC energy consumption + starting engine energy consumption * number of engine starts;

[0012] Determine the engine starting condition in series mode based on the power at the marked points in series mode.

[0013] Further, the steps of sequentially finding the operating points with the highest, second-highest, etc. overall efficiency according to the determined superimposed charging power include:

[0014] Calculate the engine power after superimposing the charging power according to the determined superimposed charging power;

[0015] Based on the engine power after superimposing the charging power, obtain the engine speed N_req_se and torque T_req_se at this time vehicle speed point according to the optimal economic line table;

[0016] Based on the speed N_req_se and torque T_req_se, combined with the transmission efficiency MAP and power generation efficiency MAP, obtain the overall efficiency Eff_total and the corresponding specific fuel consumption ge at this speed and torque.

[0017] Further, the superimposed charging power is calculated by the following formula:

[0018] Superimposed charging power = S1 * S2 * [(upper / lower limit power formed by the tangent of the specific fuel consumption contour area formed by (minimum specific fuel consumption * S) and the constant power line - driver demand power)]; S is a user-defined value, with a value range of [1, min(P coefficient, 1 / 2 * area enclosed by the engine external characteristic torque and speed / area enclosed by the minimum specific fuel consumption contour)], where P coefficient = average specific fuel consumption of the engine in user big data / minimum specific fuel consumption of the engine in user big data.

[0019] Further, the optimal economic line table is obtained through the following steps:

[0020] Obtain the engine universal characteristic curve and specific fuel consumption distribution;

[0021] Draw constant power curves on the universal characteristic curve;

[0022] Take the point with the lowest specific fuel consumption on the constant power line and obtain its engine speed;

[0023] Obtain the optimal economic line table according to the power at the lowest specific fuel consumption point obtained and the corresponding engine speed.

[0024] Further, the steps of sequentially finding the operating points with the highest, second-highest, etc. overall efficiency, extracting the corresponding engine demand power for each operating point, and accumulating the energy of the engine power for each point found include:

[0025] During the process of finding the point, if the efficiency corresponding to (the point with the highest total efficiency - the point at the previous moment) ≥ a% or the efficiency corresponding to (the point with the highest total efficiency - the point at the next moment) ≥ a%, then this highest-efficiency point is considered invalid, and continue to search downward for the second-highest point. The second-highest point is also judged according to the above conditions, and search in turn. If the second-highest point is valid, then use the second-highest point as the point with the highest efficiency. Every time the point with the highest efficiency is found, all points within t1 time before and after this point are marked as the series mode.

[0026] Further, a = 5 and t1 = 2.5 s.

[0027] Further, the steps of judging the working mode of the vehicle according to the obtained vehicle speed include:

[0028] If the vehicle speed is greater than the vehicle speed threshold, determine that the mode corresponding to this vehicle speed point at this time is the parallel mode;

[0029] If the vehicle speed is less than or equal to the vehicle speed threshold, obtain the driving demand power P_request of the vehicle;

[0030] If the driving demand power P_request is greater than the power threshold, determine that the mode corresponding to this vehicle speed point at this time is the series mode;

[0031] If the driving demand power P_request is less than or equal to the power threshold, determine that the mode corresponding to this vehicle speed point at this time is the pure electric mode, and the pure electric mode is the engine shutdown condition.

[0032] Further, the vehicle speed threshold is determined in the following way:

[0033] Among the intersection points of the specific fuel consumption contour line region formed by the point with the minimum specific fuel consumption of the engine universal characteristic * the emphasis coefficient and the constant engine speed line, take the minimum speed. The vehicle speed corresponding to this speed transmitted to the wheel end through the powertrain is the vehicle speed threshold;

[0034] Where the emphasis coefficient = the ratio of the distribution area of all working condition points in the user big data / the distribution area of the high-gear working condition points, and the emphasis coefficient is greater than 1; and / or,

[0035] The power threshold is determined in the following way:

[0036] The power threshold = the minimum power taken from the intersection point of the specific fuel consumption contour line region formed by the point with the minimum specific fuel consumption of the engine universal characteristic * the P coefficient and the constant engine power line. This power is the power threshold;

[0037] The P coefficient = the average specific fuel consumption of the engine in the user big data / the minimum specific fuel consumption of the engine in the user big data.

[0038] Further, after the step of determining that the mode corresponding to this vehicle speed point at this time is the parallel mode, it also includes:

[0039] Calculate the engine demand torque at this time through the following formula:

[0040] T_req_pa = P_request * 9550 / (V / tire radius / trans_eng2wheel);

[0041] N_req_pa = (V / tire radius / trans_eng2wheel);

[0042] Where trans_eng2wheel is the engine-to-wheel-end speed ratio, V is the vehicle speed, and N_req_pa is the demand speed;

[0043] If the engine demand torque in the parallel mode is greater than the torque threshold, T_req_pa remains unchanged;

[0044] If the engine demand torque in the parallel mode is less than or equal to the torque threshold, T_req_pa is updated to the torque threshold at this speed.

[0045] Furthermore, the torque threshold is determined in the following manner:

[0046] Torque threshold = the point with the minimum specific fuel consumption in the engine universal characteristic * the specific fuel consumption contour area formed by the emphasis coefficient, and among the intersection points of the equal engine torque line, take the minimum torque, and this torque is the torque threshold.

[0047] Applying the technical solution of the present invention, a method for determining the start-stop conditions of a hybrid vehicle includes: obtaining the vehicle speed of a specific cycle condition; judging the working mode of the vehicle according to the obtained vehicle speed; when the working mode of the vehicle is the series mode, determining the superimposed charging power according to the NVH weight coefficient S1 and the economic weight coefficient S2; successively finding the working points with the highest, second-highest,... overall efficiency according to the determined superimposed charging power, extracting the corresponding engine demand power of each working point, and accumulating the energy of the engine power for each point found; marking each additional point as the series mode, then accumulating the energy of this power point once until the accumulated energy ≥ the total driving demand energy + DCDC energy consumption + starting engine energy consumption * number of starting times; determining the starting conditions of the series mode according to the marked point power of the series mode. This method for determining the start-stop conditions of a hybrid vehicle, when determining the start-stop conditions of a hybrid vehicle, not only considers the fuel consumption during vehicle operation, but also needs to consider the NVH performance and economy during vehicle operation. Therefore, it can comprehensively consider the influence of various factors during the start-stop process of the vehicle, perform multi-performance comprehensive optimization on the start-stop conditions of the vehicle, ensure that the fuel consumption of the vehicle is relatively low while ensuring the NVH performance and economy of the vehicle, and enable the vehicle to obtain better comprehensive performance. Description of the Drawings

[0048] The accompanying drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0049] Figure 1 A power-train structure block diagram of a hybrid vehicle according to an embodiment of the present invention is shown;

[0050] Figure 2 A flowchart of a start-stop condition determination method for a hybrid vehicle according to an embodiment of the present invention is shown;

[0051] Figure 3 A graph of the best fuel consumption of the engine of a hybrid vehicle according to an embodiment of the present invention is shown;

[0052] Figure 4 A flowchart of obtaining an optimal economic line table for a hybrid vehicle according to an embodiment of the present invention is shown.

[0053] Description of reference numerals: 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 embodiments

[0054] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0055] As Figure 1 shown, the present invention provides a power-train for a 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, a wheel 12, a clutch 13, and a reduction gear 14.

[0056] The engine 2 is connected to the generator 5 through a gear pair, and the engine 2 can be started through the generator 5. When the clutch 13 is disengaged, the engine 2 does not participate in directly driving the vehicle, but drives the generator 5 to generate electricity to provide energy for the power battery 9 or the drive motor 8, and the vehicle is driven by the drive motor 8. When the clutch 13 is engaged, the torque of the engine 2 is transmitted to the wheel 12 through the clutch 13 and the reduction gear 14, and the engine 2 can jointly drive the hybrid vehicle with the drive motor 8.

[0057] The above-mentioned 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 systems in the power domain of the hybrid vehicle of the present invention.

[0058] The main operating modes of the hybrid vehicle mainly include the following:

[0059] Parking and engine shutdown: The hybrid vehicle is in a parked state, and the engine 2 is in a shutdown state. At this time, the clutch 13 is in a disengaged state, and the vehicle control unit 11 stops sending fuel injection commands and related torque commands; the generator 5 starts the engine 2, and the generator 5 drags 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 engine 2 to inject fuel and ignite. At this time, the clutch 13 is in a disengaged state; the engine 2 shuts down, the vehicle control unit 11 stops sending fuel injection commands and related torque commands, and the EMS controls the engine 2 to cut off fuel and shut down. At this time, the clutch 13 is in a disengaged state.

[0060] Pure electric mode: When the power battery has sufficient power and the vehicle speed and the driver's required torque are relatively small, the engine 2 shuts down, and the vehicle is driven by the drive motor 8. The energy of the drive motor 8 comes entirely from the power battery 9. In this case, the clutch 13 is disengaged, the engine 2 shuts down, and the drive motor 8 directly drives the wheels.

[0061] Series mode: When the vehicle speed increases or the driver's required torque is large, at this time, the engine 2 generates electricity through the generator 5 and, together with the power battery 9, serves as the energy source for the drive motor 8, or supplies power to the drive motor 8 and charges the power battery at the same time. In this case, the clutch 13 is disengaged, the engine 2 does not transmit torque to the wheel ends, and the drive motor 8 directly drives the wheels.

[0062] Parallel mode: When the vehicle speed continues to increase and the driver's required torque decreases, the clutch 13 is controlled to engage, and the engine 2 directly drives and participates in the drive. The generator 5 generates electricity according to the power battery power and the engine load. When the driver's required torque is greater than the upper limit of the engine economic zone or the engine 2 responds slowly, the drive motor 8 provides assistance. In this case, the clutch 13 is engaged, and the engine 2 and the drive motor 8 jointly drive the wheels.

[0063] Recovery condition: The vehicle is in a driving state. The vehicle control unit 11 calculates the coasting energy recovery torque based on the vehicle speed and the braking energy recovery torque requested by the ESP (Electronic Stability Program), and controls the engine 2 to be in a power generation or fuel cut-off state. The drive motor 8 recovers and generates electricity according to the energy recovery torque.

[0064] In the control of hybrid start-stop conditions, it is necessary to balance multiple performances such as fuel consumption, NVH, emissions, and drivability. For a fixed cycle condition (such as WLTC), without considering the accessory consumption and the energy consumption of starting the engine, once the vehicle parameters are determined, the effective work at the wheel end consumed by the vehicle for each complete cycle is the same (both to overcome the wheel end resistance). In addition, according to the regulations of the fuel consumption and emissions test methods for hybrid vehicles, the battery state of charge is balanced before and after WLTC of the vehicle, that is to say, all the effective work at the wheel end ultimately comes from the engine, and the battery is only used as an energy conversion pool. Therefore, the key to achieving the fuel consumption target lies in how to most economically make the energy output by the engine to the wheel end equal to the effective work at the wheel end consumed by the cycle. Under the condition that the engine parameters are determined, the economic line of the engine operation is also determined. The key to improving fuel consumption is the number of starts and the system efficiency.

[0065] Therefore, the method for determining the start-stop conditions of the hybrid vehicle in the embodiments of the present application mainly improves the comprehensive working performance of the hybrid vehicle from the aspects of the number of starts and the system efficiency.

[0066] Combined with Figures 2 to 4 As shown, according to the embodiments of the present invention, the method for determining the start-stop conditions of a hybrid vehicle includes: obtaining the vehicle speed of a specific cycle condition; judging the working mode of the vehicle according to the obtained vehicle speed; when the working mode of the vehicle is the series mode, determining the superimposed charging power according to the NVH weight coefficient S1 and the economic weight coefficient S2; successively finding the working points with the highest, second highest,... total efficiency according to the determined superimposed charging power, extracting the engine required power corresponding to each working point, and accumulating the energy of the engine power for each point found; for each additional point marked as the series mode, accumulating the energy of this power point once until the accumulated energy ≥ the total driving demand energy + DCDC energy consumption + starting engine energy consumption * the number of starts; determining the start condition of the series mode according to the power of the marked points in the series mode.

[0067] In the method for determining the start-stop conditions of the hybrid vehicle, when determining the start-stop conditions of the hybrid vehicle, not only the fuel consumption during vehicle operation is considered, but also the NVH performance and economy during vehicle operation need to be considered. Therefore, various factors affecting the start-stop process of the vehicle can be comprehensively considered, and the start-stop conditions of the vehicle can be optimized with multiple performances. While ensuring that the fuel consumption of the vehicle is relatively low, the NVH performance and economy of the vehicle can be ensured, so that the vehicle obtains better comprehensive performance.

[0068] In one embodiment, when collecting the vehicle speed of a specific cycle condition, it is also possible to collect the time, vehicle speed, driving demand power, actual engine power, actual power of the power battery, DCDC energy consumption, engine universal characteristic parameters, transmission efficiency, motor efficiency, etc. of a specific cycle condition (taking WLTC as an example).

[0069] V is the vehicle speed, P_request is the driving demand power, E_DCDC is the DCDC energy consumption, Eff_trans is the driveline efficiency, Eff_GM is the generator efficiency, and the engine-to-wheel speed ratio is trans_eng2wheel.

[0070] The above parameters can be obtained in advance, so as to provide corresponding data support for the subsequent method steps.

[0071] The start-stop condition determination method for the hybrid vehicle of the present application is also applicable to other specific cycle working conditions.

[0072] The steps of sequentially finding the operating points with the highest, second-highest,... total efficiency according to the determined superimposed charging power include: calculating the engine power after superimposing the charging power according to the determined superimposed charging power; obtaining the engine speed N_req_se and torque T_req_se at this time vehicle speed point according to the engine power after superimposing the charging power based on the optimal economic line table; obtaining the total efficiency Eff_total and the corresponding specific fuel consumption ge at this speed and torque by combining the transmission efficiency MAP and the power generation efficiency MAP.

[0073] The superimposed charging power is calculated by the following formula: superimposed charging power = S1 * S2 * [(upper / lower limit power formed by the tangent of the specific fuel consumption contour area formed by (minimum specific fuel consumption * S) and the constant power line - driver demand power)]; S is a user-defined value, and the value range is [1, min(P coefficient, 1 / 2 * area enclosed by the engine external characteristic torque and speed / area enclosed by the minimum specific fuel consumption contour)], where P coefficient = average specific fuel consumption of the engine in user big data / minimum specific fuel consumption of the engine in user big data. Through this limitation, the phenomenon of engine knocking emissions in the early combustion area can be effectively avoided, and the working stability and reliability of the engine can be improved.

[0074] In order to further improve the comprehensive performance of vehicle operation, in some embodiments, emission weight coefficients and drivability coefficients can also be considered to obtain a more comprehensive performance superimposed charging power.

[0075] In this embodiment, the calculated superimposed charging power is shown in Table 1:

[0076] Table 1 Superimposed Charging Power

[0077] Driver demand power Superimposed power Superimposed power after weighting Engine demand power after superposition 15 15 15*S1*S2 30 (lower limit of contour area) 20 15 15*S1*S2 35 30 15 15*S1*S2 45 40 15 15*S1*S2 55 (upper limit of contour area) 50 5 5*S1*S2 55 (upper limit of contour area) 60 0 0 60 … … …

[0078] Where S1 ≤ 1 and S2 ≤ 1. When calculating the difference between the upper / lower limit power formed by the tangency of the specific fuel consumption contour area and the constant power line and the driver's demand power, the calculation principle is that within the upper and lower limit power range of the contour area, the superimposed power is relatively constant, but the sum of the superimposed power and the driver's demand power cannot exceed the upper limit power range of the contour area. Therefore, after the driver's demand power reaches a certain value, the engine demand power after superposition remains at the upper limit power position of the contour area, and the superimposed power gradually decreases until the driver's demand power reaches or exceeds the upper limit power of the contour area. At this time, the superimposed power is 0. When exceeding the upper and lower limit power range of the contour area, the engine no longer charges the battery, and the engine demand power is the driver's demand power.

[0079] This method can ensure that within the allowable range, when the engine demand power supplies the driver's demand power and the superimposed power simultaneously, the NVH weight and the economic weight can always be considered, so as to ensure that the calculated engine demand power can have the optimal economic line and good NVH performance.

[0080] The optimal economic line table is shown in Table 2:

[0081] Table 2 Optimal Economic Line Table

[0082] Engine demand power 10 20 30 …… Engine demand speed 1200 1500 2000

[0083] Combined with reference to Figure 4 As shown, the optimal economic line table is obtained through the following steps: Obtain the engine universal characteristic curve and the specific fuel consumption distribution; Draw constant power curves on the universal characteristic curve; Take the point with the lowest specific fuel consumption on the constant power curve and obtain its engine speed; Obtain the optimal economic line table according to the power at the lowest specific fuel consumption point obtained and the corresponding engine speed.

[0084] Combined with reference to Figure 3 As shown, this figure is the engine's best fuel consumption curve, where the horizontal axis is the engine speed, the vertical axis is the engine external characteristic torque, the contour lines are the minimum specific fuel consumption contour lines, the middle shaded area is the efficient area, and the hyperbolas are the constant power curves. Through this figure, the above-mentioned optimal economic line table can be conveniently obtained, thus effectively ensuring that the engine can start with lower fuel consumption and better NVH performance and economy.

[0085] In one embodiment, the working points with the highest total efficiency, the second highest total efficiency, and so on are sequentially found, and the engine required power corresponding to each working point is extracted. The step of accumulating energy by adding the engine power for each point found includes: during the process of finding a point, if the efficiency corresponding to (the point with the highest total efficiency - the previous moment point) ≥ a% or the efficiency corresponding to (the point with the highest total efficiency - the next moment point) ≥ a%, then this highest efficiency point is considered invalid, and continue to find the second highest point downward. The second highest point is also judged according to the above conditions, and so on. If the second highest point is valid, then use the second highest point as the point with the highest efficiency. For each point with the highest efficiency found, all points within t1 time before and after this point are marked as the series mode.

[0086] The range of t1 can be 2 to 5 s. In one embodiment, a = 5 and t1 = 2.5 s.

[0087] During the process of finding the point with the highest total efficiency, when the highest point is invalid, then continue to find the second highest point and update it as the new highest point, and judge whether the new highest point is valid. If the new highest point is valid, then mark all points within t1 s before and after the new highest point as the series mode, and then re-define the new highest point and continue to find the valid point until the accumulated energy ≥ total driving demand energy + DCDC energy consumption + starting engine energy consumption * number of starting times. Therefore, during the process of finding the point with the highest efficiency, there will be multiple valid marked points. The highest point in each time period among these marked points can be used as the highest total efficiency point in that time period, that is, there are multiple defined highest points for the marked points in the series mode. The highest point here does not refer to the highest efficiency point of the entire series mode, but the highest efficiency point of each valid time period. During the process of the vehicle running through the entire cycle, the marked points corresponding to each time period are used as the starting conditions, that is, the engine reaches the starting conditions at each marked point. Since the selected total efficiency is the high-efficiency working points arranged according to effectiveness, therefore, the engine can start with a relatively high efficiency at each marked point, thus ensuring that the engine starting efficiency can reach the optimum. At the same time, since during the process of finding the point with the highest total efficiency, the accumulated energy provided by the determined valid points ≥ total driving demand energy + DCDC energy consumption + starting engine energy consumption * number of starting times, it can be ensured that the accumulated energy provided by these valid points can meet the energy required for the vehicle to run through the entire cycle.

[0088] The initial value of the number of starting times can be set and incremented by 1 in sequence until the number of starting times is the same as the number of series starting times.

[0089] In addition, in order to prevent frequent starting, the minimum starting time of the engine is set to t2, where t2 can be 4 to 10 s. In one embodiment, t2 is 5 s.

[0090] In one embodiment, the steps of determining the working mode of the vehicle according to the obtained vehicle speed include: if the vehicle speed is greater than the vehicle speed threshold, determining that the mode corresponding to this vehicle speed point at this time is the parallel mode; if the vehicle speed is less than or equal to the vehicle speed threshold, obtaining the driving demand power P_request of the vehicle; if the driving demand power P_request is greater than the power threshold, determining that the mode corresponding to this vehicle speed point at this time is the series mode; if the driving demand power P_request is less than or equal to the power threshold, determining that the mode corresponding to this vehicle speed point at this time is the pure electric mode, and the pure electric mode is the engine shutdown condition.

[0091] The vehicle speed threshold is determined in the following manner:

[0092] Among the intersection points of the specific fuel consumption contour area formed by the points with the smallest specific fuel consumption of the engine universal characteristic and the emphasis coefficient and the constant engine speed line, the smallest speed is taken, and the vehicle speed corresponding to this speed transmitted to the wheel end through the powertrain is the vehicle speed threshold;

[0093] Where the emphasis coefficient = the ratio of the distribution area of all working condition points of user big data to the distribution area of high-gear working condition points, and the emphasis coefficient is greater than 1. Here, the high gear refers to the gears above the direct gear.

[0094] When the vehicle speed is greater than the vehicle speed threshold, the pure electric mode cannot provide enough torque to make the vehicle reach the predetermined vehicle speed, the battery has enough power, and the driver's demand torque cannot meet the torque requirement for the vehicle speed. At this time, the battery can supply power to the drive motor, and the engine and the drive motor work together to provide the required torque. The engine and the drive motor jointly drive the wheels. At this time, the vehicle is in the parallel mode, and a higher vehicle speed can be obtained while ensuring a lower specific fuel consumption.

[0095] By this method, it can be ensured that the specific fuel consumption of the engine is related to the vehicle speed. While being able to reach the set vehicle speed, a smaller specific fuel consumption can be obtained, reducing the fuel consumption of the vehicle.

[0096] When the vehicle speed is less than or equal to the vehicle speed threshold, the operating mode of the vehicle can be judged according to the driving demand power P_request. When the driving demand power P_request is greater than the power threshold, it means that the energy provided solely by the battery cannot meet the power demand of the vehicle. Therefore, the engine needs to participate in the work. When the engine demand power is between the upper / lower limit power formed by the tangency of the specific fuel consumption contour area and the constant power line, if the lower limit power of the engine in the specific fuel consumption contour area is greater than the driver's demand power, the excess power provided by the engine at this time can charge the battery, so that the engine can work under a condition with a smaller fuel consumption.

[0097] The power threshold is determined in the following manner:

[0098] Power threshold = the intersection point of the specific fuel consumption contour area formed by the point with the minimum specific fuel consumption in the engine universal characteristics * P coefficient and the engine constant power line, and take the minimum power, which is the power threshold;

[0099] P coefficient = average specific fuel consumption of the engine in user big data / minimum specific fuel consumption of the engine in user big data.

[0100] After the step of determining that the mode corresponding to this time vehicle speed point is the parallel mode, it further includes: calculating the engine demand torque at this time through the following formula:

[0101] T_req_pa = P_request * 9550 / (V / tire radius / trans_eng2wheel);

[0102] N_req_pa = (V / tire radius / trans_eng2wheel); where trans_eng2wheel is the engine-to-wheel end speed ratio, V is the vehicle speed, and N_req_pa is the demand speed;

[0103] If the engine demand torque in the parallel mode is greater than the torque threshold, T_req_pa remains unchanged;

[0104] If the engine demand torque in the parallel mode is less than or equal to the torque threshold, T_req_pa is updated to the torque threshold at this speed.

[0105] The torque threshold is determined in the following way: Torque threshold = the intersection point of the specific fuel consumption contour area formed by the point with the minimum specific fuel consumption in the engine universal characteristics * emphasis coefficient and the engine torque line, and take the minimum torque, which is the torque threshold.

[0106] If the engine demand torque in the parallel mode is greater than the torque threshold, it means that the engine demand torque is within the efficient range. Therefore, the engine demand torque can be kept at the current torque at this time. If the engine demand torque in the parallel mode is less than or equal to the torque threshold, it means that the engine demand torque exceeds the efficient range. Therefore, it is necessary to update the engine demand torque to the torque threshold at this speed so that the engine demand torque can still be kept within the efficient range to ensure the working efficiency and performance of the engine.

[0107] In the present invention, the starting points of the series mode and the parallel mode can be marked in the above manner. Points other than the calibrated series mode and parallel mode are marked as the pure electric mode. Among them, the marked points of the series mode and the parallel mode are the starting points, and the marked point of the pure electric mode is the stopping point. According to the specific fuel consumption of each working condition point mode and working point, the total fuel consumption of the cycle and the fuel consumption per 100 kilometers can be calculated, and then the starting and stopping conditions are determined by comprehensively considering NVH and economy.

[0108] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprising" and / or "including" are used in this specification, they specify the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0109] It should be noted that the terms "first", "second", etc. in the description and claims of the present application and the above-mentioned drawings 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 under appropriate circumstances so that the embodiments of the present application described herein can be implemented in an order different from those illustrated or described herein.

[0110] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for determining the starting and stopping conditions of a hybrid vehicle, characterized in that, it includes: Obtain the time and corresponding vehicle speed of a specific cycle condition; Judge the working mode of the vehicle according to the obtained vehicle speed; When the working mode of the vehicle is in series mode, determine the superposition charging power according to the NVH weight coefficient S1 and the economic weight coefficient S2; According to the determined superposition charging power, sequentially find the operating points arranged in descending order of total efficiency, extract the corresponding engine demand power of each operating point, and accumulate the energy of the engine power every time a point is found; For each additional point marked as series mode, accumulate the energy of this power point once until the accumulated energy ≥ total driving demand energy + DCDC energy consumption + starting engine energy consumption * number of starting times; Determine the starting condition of the series mode according to the marked point power of the series mode; The steps of sequentially finding the operating points arranged in descending order of total efficiency and extracting the corresponding engine demand power of each operating point, and accumulating the energy of the engine power every time a point is found include: During the process of finding points, if the efficiency corresponding to (the point with the highest total efficiency - the previous moment point) ≥ a% or the efficiency corresponding to (the point with the highest total efficiency - the next moment point) ≥ a%, then this highest efficiency point is considered invalid, continue to find the next highest point downward, and the next highest point is also judged according to the above conditions. Sequentially find. If the next highest point is valid, use the next highest point as the point with the highest efficiency. Every time the point with the highest efficiency is found, all points within t1 time before and after this point are marked as series mode.

2. The method for determining the starting and stopping conditions of a hybrid vehicle according to claim 1, characterized in that, The steps of sequentially finding the operating points arranged in descending order of total efficiency according to the determined superposition charging power include: Calculate the engine power after the superposition charging power according to the determined superposition charging power; According to the engine power after the superposition charging power, obtain the engine speed N_req_se and torque T_req_se at this time vehicle speed point based on the optimal economic line table; According to the speed N_req_se and torque T_req_se, combined with the transmission efficiency MAP and the power generation efficiency MAP, obtain the total efficiency Eff_total and the corresponding specific fuel consumption ge at this speed and torque.

3. The method for determining the starting and stopping conditions of a hybrid vehicle according to claim 1, characterized in that, The superposition charging power is calculated by the following formula: Superposition charging power = S1 * S2 * [(upper / lower limit power formed by the tangent of the specific fuel consumption contour area formed by (minimum specific fuel consumption * S) and the constant power line - driver demand power]; S is a user-defined value, and the value range is [1, min (P coefficient, 1 / 2 * area enclosed by the engine external characteristic torque and speed / area enclosed by the minimum specific fuel consumption contour)], where P coefficient = average specific fuel consumption of the engine in user big data / minimum specific fuel consumption of the engine in user big data.

4. The method for determining the starting and stopping conditions of a hybrid vehicle according to claim 1, characterized in that, The optimal economic line table is obtained through the following steps: Obtain the engine universal characteristic curve and specific fuel consumption distribution; Draw equal-power curves on the engine map; Select the point with the lowest specific fuel consumption on the equal-power curve and obtain its engine speed; Obtain the optimal economic line table based on the power at the lowest specific fuel consumption point and the corresponding engine speed obtained.

5. The method for determining the start-stop conditions of a hybrid vehicle according to claim 1, wherein, a = 5, t1 = 2.5 s.

6. The method for determining the start-stop conditions of a hybrid vehicle according to claim 1, wherein, The steps of judging the working mode of the vehicle according to the obtained vehicle speed include: If the vehicle speed is greater than the vehicle speed threshold, determine that the mode corresponding to this vehicle speed point at this time is the parallel mode; If the vehicle speed is less than or equal to the vehicle speed threshold, obtain the driving demand power P_request of the vehicle; If the driving demand power P_request is greater than the power threshold, determine that the mode corresponding to this vehicle speed point at this time is the series mode; If the driving demand power P_request is less than or equal to the power threshold, determine that the mode corresponding to this vehicle speed point at this time is the pure electric mode, and the pure electric mode is the engine stop condition.

7. The method for determining the start-stop conditions of a hybrid vehicle according to claim 6, wherein, The vehicle speed threshold is determined in the following manner: Among the intersection points of the specific fuel consumption contour area formed by the point with the minimum specific fuel consumption of the engine map * the emphasis coefficient and the engine constant speed line, take the minimum speed, and the vehicle speed corresponding to this speed transmitted to the wheel end through the powertrain is the vehicle speed threshold; where the emphasis coefficient = the ratio of the distribution area of all working condition points in the user big data / the distribution area of high-gear working condition points, and the emphasis coefficient is greater than 1; and / or, The power threshold is determined in the following manner: The power threshold = among the intersection points of the specific fuel consumption contour area formed by the point with the minimum specific fuel consumption of the engine map * the P coefficient and the engine constant power line, take the minimum power, and this power is the power threshold; The P coefficient = the average specific fuel consumption of the engine in the user big data / the minimum specific fuel consumption of the engine in the user big data.

8. The method for determining the start-stop conditions of a hybrid vehicle according to claim 6, wherein, After the step of determining that the mode corresponding to this vehicle speed point at this time is the parallel mode, the following steps are further included: Calculate the engine demand torque at this time through the following formula: T_req_pa = P_request * 9550 / (V / tire radius / trans_eng2wheel); N_req_pa = (V / tire radius / trans_eng2wheel); where trans_eng2wheel is the engine-to-wheel speed ratio, V is the vehicle speed, and N_req_pa is the required speed; If the engine demand torque in the parallel mode is greater than the torque threshold, T_req_pa remains unchanged; If the engine demand torque in the parallel mode is less than or equal to the torque threshold, T_req_pa is updated to the torque threshold at this speed.

9. The method for determining the start-stop conditions of a hybrid vehicle according to claim 8, wherein, The torque threshold is determined in the following manner: Torque threshold = the minimum torque among the intersection points of the specific fuel consumption contour area formed by the point with the minimum specific fuel consumption in the engine universal characteristics * the emphasis coefficient and the constant engine torque line. This torque is the torque threshold.

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