Automobile energy efficiency optimization method based on PnG mode

Abstract

The invention discloses an automobile energy efficiency optimization method based on a PnG mode, relates to the technical field of automobile intelligent control, and aims to solve the problem that an existing automobile energy efficiency optimization method is poor in energy-saving effect, a vehicle instantaneous fuel consumption model in the PnG mode is established, and constraint conditions of the optimization problem are analyzed in detail. An optimal energy efficiency operation speed optimization model is put forward to deeply research an optimization control algorithm under a PnG strategy, and finally an optimization control model based on the PnG strategy is put forward. In the PnG mode, the control method can effectively optimize speed control in an urban road scene, and the energy-saving effect of the vehicle can be remarkably improved. Compared with a traditional control method, the maximum energy saving rate of the technical scheme can reach 39.4%.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile intelligent control, and in particular to an automobile energy efficiency optimization method based on a PnG mode. Background Art

[0002] Eco-driving, also known as energy-saving driving, refers to improving the vehicle's energy efficiency by optimizing the vehicle's driving strategy, reducing unnecessary fuel consumption and emissions.

[0003] Traditional eco-driving mainly relies on the driver's experience and awareness to achieve energy conservation and emission reduction by changing driving style, choosing appropriate routes, and reasonably controlling vehicle speed and acceleration. In recent years, with the rapid development of intelligent connected vehicles, the concept and technology of eco-driving have also been updated and developed.

[0004] The PnG collaborative control strategy has been widely explored in recent years, especially in the Connected and Automated Vehicle (CAV) system, showing significant energy saving potential. Cao et al.'s research shows that in the convoy following scenario, the PnG strategy can achieve better fuel economy than constant speed driving.

[0005] Due to the complexity of vehicle driving conditions on the road, existing research on PnG energy-saving mechanisms mostly uses simplified road conditions and vehicle dynamics models. These idealized assumptions are quite different from the actual road and traffic environment. For example, many theoretical studies are limited to straight roads, and rarely consider road conditions with variable terrain such as slopes. This leads to poor energy-saving effects of vehicles. Summary of the invention

[0006] The purpose of the present invention is to provide a method for optimizing automobile energy efficiency based on a PnG mode in order to solve the problem that the existing automobile energy efficiency optimization method has poor energy-saving effect.

[0007] The technical solution adopted by the present invention to solve the above technical problems is:

[0008] A method for optimizing automobile energy efficiency based on a PnG mode comprises the following steps:

[0009] Step 1: Get the net wheel force F of the vehicle w (t), wheel radius r w , transmission ratio i e,g and the transmission system efficiency η t , and according to the net wheel force F w (t), wheel radius r w , transmission ratio i e,g and the transmission system efficiency η t , get the engine torque Te (t);

[0010] Step 2: Get the vehicle speed v(t) and combine it with the wheel radius r w and transmission ratio i e,g , get the speed ω e (t);

[0011] Step 3: Obtain the minimum engine power P e,min and engine efficiency η e , and the engine torque T e (t), speed ω e (t), minimum engine power P e,min and engine efficiency η e Input the Willans model to obtain the power P generated by fuel consumption f (t);

[0012] Step 4: Power P generated based on fuel consumption f (t), and combined with the operating mechanism of the PnG mode, the energy consumption E of the vehicle trip in the PnG mode is obtained PnG Model;

[0013] Step 5: Obtain the vehicle's net driving force F a (t), and the vehicle net driving force F a (t), engine torque T e (t), wheel radius r w , transmission system efficiency η t And the transmission ratio i e,g , input the Willans model to get the fuel consumption for mileage

[0014] Step 6: Obtain the total fuel consumption J and trip end time t for the entire trip f , initial stroke speed v i , speed v at the end of the stroke f and travel distance f , and the amount of fuel consumed by the mileage As the objective function, the optimal energy consumption control problem is constructed;

[0015] Step 7: Use the total fuel consumption J and the trip distance s for the entire trip f , get the fuel consumption per unit distance;

[0016] Step 8: Based on the unit distance fuel consumption and combined with the optimal energy consumption control problem, the unit energy consumption control problem is constructed, that is, the PnG mode energy-saving optimal control problem;

[0017] Step 9: Solve the PnG mode energy-saving optimal control problem to obtain the optimal speed and gear.

[0018] Furthermore, the wheel net force F w (t) is expressed as:

[0019]

[0020] C 0 =C rr mgcosθ+mgsinθ

[0021] C 1 =0

[0022]

[0023] Among them, C 0 , C 1 , C 2 is the road load factor, C rr is the rolling resistance coefficient, θ is the road slope angle, ρ a is the air density, A c is the frontal area of ​​the vehicle, C D is the air resistance coefficient, m is the sum of the vehicle's curb weight and the weight of its occupants and cargo, and g is the acceleration due to gravity.

[0024] Furthermore, the engine torque T e (t) is expressed as:

[0025]

[0026] Furthermore, the speed ω e (t) is expressed as:

[0027]

[0028] Furthermore, the power P f (t) is expressed as:

[0029]

[0030] Among them, k e,0 , k e,1 , k e,2 , k e,3 , k e,4 is the correlation coefficient.

[0031] Furthermore, in the PnG mode, the energy consumption of the vehicle trip is PnG The model is expressed as:

[0032]

[0033] Where n is the nth PnG segment, N is the total number of PnG segments, and t n,0 and t n,png The running time of the nth PnG segment is from t n,0 to n,png .

[0034] Furthermore, the amount of fuel consumed by the mileage It is expressed as:

[0035]

[0036] Among them, H f is the lower calorific value of the fuel, a p (t) is the vehicle driving acceleration.

[0037] Furthermore, the optimal energy consumption control problem is expressed as:

[0038]

[0039] Among them, a b (t) is the braking acceleration, s(t) is the distance traveled at time t, s min (t) is the minimum travel distance, s max (t) is the maximum travel distance, a p,min (v(t),t) is the minimum driving acceleration, a p,max (v(t),t) is the maximum driving acceleration, a b,max is the maximum braking deceleration, v min (t,s(t)) is the minimum instantaneous vehicle speed, v max (t,s(t)) is the maximum instantaneous vehicle speed.

[0040] Furthermore, the PnG mode energy-saving optimal control problem is expressed as:

[0041]

[0042] Furthermore, the optimal speed and gear are expressed as:

[0043]

[0044] Among them, v c,opt To solve the optimal instantaneous speed, i e,c,opt To solve the optimal transmission ratio, v is the instantaneous vehicle speed.

[0045] The beneficial effects of the present invention are:

[0046] This application establishes a vehicle instantaneous fuel consumption model under PnG mode and analyzes the constraints of the optimization problem in detail. The optimal energy-efficient operating speed optimization model is proposed, and the optimization control algorithm under the PnG strategy is deeply studied, and finally an optimization control model based on the PnG strategy is proposed. Under PnG mode, the control method of this application can effectively optimize speed control in urban road scenarios and can significantly improve the energy-saving effect of the vehicle. Compared with traditional control methods, the technical solution of this application can achieve a maximum energy saving rate of 39.4%. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic diagram of the forces acting on a moving vehicle; Figure 2 It is a schematic diagram of the PnG mode; Figure 3 is the engine speed and output torque curve; Figure 4 is the engine speed and fuel consumption curve; Figure 5 The fuel consumption per 100 kilometers includes the idling fuel consumption; Figure 6 It is the fuel consumption per 100 kilometers excluding idling fuel consumption; Figure 7 The fuel consumption per 100 kilometers includes the idling fuel consumption; Figure 8 It is the fuel consumption per 100 kilometers excluding idling fuel consumption; Fig. 9 The fuel consumption per 100 kilometers includes the idling fuel consumption; Fig.10 It is the fuel consumption per 100 kilometers excluding idling fuel consumption; Fig.11 is the fuel saving rate including idling fuel consumption; Fig.12 It is the fuel saving rate excluding idling fuel consumption; Fig.13 is the fuel saving rate including idling fuel consumption; Fig.14 It is the fuel saving rate excluding idling fuel consumption; Fig.15 is the fuel saving rate including idling fuel consumption; Fig.16 It is the fuel saving rate excluding idling fuel consumption; Fig.17 Energy efficiency conversion (including idling fuel consumption); Fig.18 It is the energy efficiency conversion amount (excluding idling fuel consumption); Fig.19 is the average speed and fuel consumption of PnG; Fig. 20 is the PnG average speed and fuel saving rate; Fig.21 is the engine efficiency at different PnG average speeds and different speed fluctuation amplitudes; Fig. 22 Pearson correlation coefficient analysis heat map for PnG mode simulation test data; Fig.23 The heat map of Spearman rank correlation coefficient analysis for PnG mode simulation test data; Fig.24 is the road slope curve; Fig.25 It is the optimal energy consumption operating speed curve. DETAILED DESCRIPTION

[0048] It should be particularly noted that, in the absence of conflict, the various embodiments disclosed in this application can be combined with each other.

[0049] Specific implementation method 1: This implementation method describes a vehicle energy efficiency optimization method based on the PnG mode. This application mainly studies the energy consumption of the vehicle in longitudinal motion. Therefore, only the longitudinal dynamic state of the vehicle is considered. The force condition of the vehicle in longitudinal motion is as follows: Figure 1 shown.

[0050] From Newton's second law of motion we know that:

[0051]

[0052] F a (t) = F p (t)-F res (t)-F b (t)

[0053] In formula (1), m t is the total effective mass of the vehicle, m t =m+m r , where m is the sum of the vehicle's curb weight and the weight of passengers and cargo, m r It is the influence term transmitted to the wheels by the inertia of rotating parts (internal rotating parts such as engines and transmissions). It usually changes with the change of transmission ratio, but this change is generally small and usually ignored.

[0054] F a (t) is the net driving force of the vehicle, F p (t) is the vehicle driving force (the sum of the forces transmitted from the vehicle power system to the wheel ends); F b (t) is the braking force applied by the friction brake, F res (t) is the vehicle driving resistance. res There are many factors affecting the vehicle's energy consumption. This paper focuses on the part that has the greatest impact on the vehicle's energy consumption when the vehicle is traveling longitudinally. Therefore, the vehicle's driving resistance F res (t) can be expressed by formula (2):

[0055] F res (t) = F rol (t)+F gra (t)+F air (t) (2)

[0056] In formula (2), F rol (t) is the rolling resistance, F gra (t) is the slope resistance, F air (t) is the air resistance. Also, we know:

[0057] Rolling resistance:

[0058] F rol (t) = Crr mg cosθ (3)

[0059] Ramp resistance:

[0060] F gra (t) = mg sinθ (4)

[0061] Air resistance:

[0062]

[0063] In formula (3) to formula (5), C rr is the rolling resistance coefficient, θ is the road slope angle, R is the vehicle turning radius, ρ a is the air density, A c is the frontal area of ​​the vehicle, C D is the air resistance coefficient, v w is the longitudinal wind speed. Substituting equations (3) to (5) into equation (2), we can obtain equation (6):

[0064]

[0065] From formula (6), we can see that the factors affecting vehicle driving resistance mainly include vehicle characteristics, road conditions, weather conditions, etc. For a certain vehicle and trip, parameters such as vehicle mass, air resistance coefficient, and rolling resistance coefficient are usually considered fixed. However, under high-speed close-following conditions, as the distance between vehicles decreases, C D This application assumes that C D The value remains unchanged.

[0066] If the longitudinal wind speed v is ignored w (wind speed when the vehicle is stationary), then equation (6) can be simplified as:

[0067]

[0068] In order to express concisely and simplify calculations, F res The constant term on the right side of (t) is integrated, and assuming that the vehicle is traveling on a straight and windless road, it is expressed by a polynomial of the speed function v(t), then equation (7) can be expressed as:

[0069] F res (t) = C 0 +C 1 v(t)+C 2 v 2 (t) (8)

[0070] Where C 0 , C 1 , C 2Defined as the road load coefficient, we can know

[0071] C 0 =C rr mgcosθ+mgsinθ (9)

[0072] C 1 =0 (10)

[0073]

[0074] The core of the Willans model is to define two key parameters, efficiency η e and minimum fuel power P e,min These two parameters are related to the engine speed ω e It is related to the performance of the engine at different speeds.

[0075] (1) Efficiency η e : The efficiency with which an engine converts fuel energy into mechanical work.

[0076] (2) Minimum fuel power P e,min : The minimum fuel power consumed by the engine at idle or low load. This power is mainly used to overcome friction and other internal losses.

[0077] The Willans model converts the power generated by fuel consumption into P f Expressed as engine torque T e and speed ω e Function:

[0078]

[0079] In formula (12), η e The heat energy conversion efficiency of the fuel combustion to the cylinder pressure is related to the engine speed ω e (t) related function, P e,min It is the minimum power to maintain the normal operation of the engine, and is also related to ω e (t) is related. e and P e,min / η e Further parameterizing as a function of engine speed, we get

[0080]

[0081] Substituting equations (13) and (14) into equation (12), we can get the power P generated by the fuel: f The closed form expression for is:

[0082]

[0083] In the formula, k e,i (i=0···4) is a coefficient related to the design. For the idle condition, T e =0 and ω e (t) = ω e,idle ,ω e,idle is the engine idle speed, and formula (12) or formula (15) can also be used to calculate the idle fuel consumption.

[0084] When the vehicle is idling or coasting, if the engine is shut down and fuel injection is stopped, set P f (t) = 0, the engine braking torque curve T can be obtained from formula (15): e,min (ω e (t)). Referring to the reasonable parameterization process of the naturally aspirated engine, the maximum torque curve T e,max (ω e (t)) is a quadratic equation:

[0085]

[0086] In summary, the Willans model is an effective tool to describe the relationship between internal combustion engine efficiency and engine operating point. It can help understand the changing law of engine efficiency, guide the optimization of engine operating point and design energy-saving driving strategies.

[0087] Using the Willans model to calculate the power P of the fuel f The definition of , for a discrete gear vehicle, the vehicle energy consumption can be obtained:

[0088]

[0089] Assuming that the vehicle engine does not consume fuel during the coasting and braking phases, the engine braking power of coasting with gear is P e,min , the definition of vehicle braking force, then P e,min =F w (t)v(t) / η t , substituting into formula (16), the engine braking energy can be obtained as:

[0090]

[0091] By P e (t) = T e (t)ω e (t) = F w (t)v(t) / η t By converting the engine torque and speed into wheel end force and vehicle speed, we can calculate E T The parameterized form of is:

[0092]

[0093] According to formula (1) and formula (8), we can get:

[0094]

[0095] We can also know that the engine speed ω e (t) is related to the vehicle speed v(t):

[0096]

[0097] Where γ e,g Corresponding gear ratio, r w is the wheel rolling radius.

[0098] Substituting equations (20) and (21) into equation (19), we can get the actual energy consumption under different gears:

[0099]

[0100] A typical PnG cycle includes an acceleration segment P and a coasting segment G. Therefore, the vehicle energy consumption E in PnG mode is PnG It consists of two parts:

[0101] E PnG =E Pul +E Gli (twenty three)

[0102] Where E Pul and E Gli They are the energy consumption in the acceleration stage and the energy consumption in the taxiing stage of PnG respectively.

[0103] 1) Energy consumption in acceleration stage E Pul

[0104] In the PnG mode, the engine consumes fuel in the acceleration section P to generate traction and output it to the wheel end. It can be seen that:

[0105]

[0106] 2) Energy consumption in taxiing section E Gli

[0107] In the coasting section G, if the vehicle enters the engine braking state, it can be known that the energy consumption of the coasting section is:

[0108]

[0109] Where η t is the transmission system efficiency. Assuming that no fuel is consumed during the engine braking phase, the absorbed power of the engine is set to P e,min (engine braking state), then:

[0110]

[0111] Substituting formula (24) into (23), we can obtain:

[0112]

[0113] The previous content discussed the state of engine braking in the G segment. The fuel consumption in the taxiing segment in other situations is as follows:

[0114] (1) If the transmission system is disconnected and the engine is idling, idling fuel consumption will be generated, E Gli =E Idl ;

[0115] (2) If the transmission system is disconnected, for engines with a coasting fuel cut-off function, E Gli =0;

[0116] 3) PnG mode vehicle energy consumption E PnG

[0117] Substituting equations (24) and (27) into equation (21), we can obtain E in the engine braking state during the PnG taxiing phase: PnG for:

[0118]

[0119] For a vehicle running in PnG mode, its speed curve is composed of a series of PnG sawtooth waves, each of which is a PnG segment (including an acceleration segment P and a coasting segment G), such as Figure 2 shown.

[0120] set up Figure 2 The PnG mode in the process has N PnG sawtooth waves, where the running time of the nth PnG segment starts from t n,0 to n,png , the acceleration section P starts from the lowest speed v min Start, quickly accelerate to maximum speed v max , the acceleration time is t p ; Then the gliding section starts from the maximum speed v max Start gliding to v min , the sliding time is t g , then a complete PnG segment is completed, let t png =t p +t g , define the PnG speed fluctuation amplitude as Δv (Δv = v max -v min ), is the PnG average vehicle speed. Then the PnG mode trip fuel consumption is:

[0121]

[0122] Combining equations (22) and (25), the Willans model is introduced to obtain the calculation E PnG The initial parameterized form of is:

[0123]

[0124] The engine speed ω in formula (30) e (t) is converted to vehicle speed v(t) and substituted into equation (20) to replace F w (t), we can get the final parameterized equation:

[0125]

[0126] Through the collation and analysis of the joint simulation result data, it can be obtained that the vehicle fuel consumption per 100 kilometers under different PnG average speeds and different speed fluctuation ranges is as follows: Figure 5 and Figure 6 For the convenience of expression, three speed sections are defined: low speed section (30-60 km / h), medium speed section (60-90 km / h), and high speed section (90-120 km / h). The specific analysis is as follows:

[0127] like Figure 5 As shown in the figure, for vehicles whose engines remain idle during the coasting phase, in PnG mode, it is observed that when the vehicle speed varies between 30km / h and 120km / h, regardless of the speed fluctuation range, the vehicle's 100km fuel consumption curve shows a concave feature. Specifically, in the low and high speed sections, the 100km fuel consumption is relatively high, while in the medium speed section, the 100km fuel consumption is relatively low. The 100km fuel consumption trend under different speed fluctuation ranges shows consistency.

[0128] In addition, the curve trend shows that as the speed fluctuation amplitude in the PnG mode increases, the vehicle's fuel consumption per 100 kilometers shows a downward trend at the same PnG average speed. However, as the speed fluctuation amplitude further increases, this trend of reducing fuel consumption gradually slows down. It can be observed that when the speed fluctuation amplitude reaches about 10km / h, the fuel consumption curve per 100 kilometers begins to converge.

[0129] In the low-speed range, the change in speed fluctuation has a relatively small impact on the fuel consumption per 100 kilometers, and the fuel consumption data under each fluctuation range are relatively close and concentrated. On the contrary, in the medium- and high-speed range, under smaller speed fluctuations (such as 4km / h and 8km / h), the fuel consumption per 100 kilometers increases significantly with the increase of the PnG average speed.

[0130] If the fuel consumption of the engine at idle speed during the coasting phase in PnG mode is excluded, the vehicle fuel consumption curves per 100 kilometers under different PnG average speeds and different speed fluctuation ranges can be obtained, such as Figure 6 shown.

[0131] It can be clearly observed from the curve trend in the figure that in the low, medium and high speed sections, the vehicle's fuel consumption per 100 kilometers continues to rise with the increase of the PnG average speed. Unlike the case where idling fuel consumption is included, no depression in the middle of the fuel consumption curve is observed, which indicates that the fuel consumption of the vehicle at idle has a significant impact on the overall fuel consumption in the medium and low speed sections. In addition, the overall impact of speed fluctuation on fuel consumption per 100 kilometers is not significant. Only in the high-speed section, especially when the speed fluctuation is small (such as 2km / h and 4km / h), the difference in fuel consumption per 100 kilometers is more obvious. This finding further reveals the different effects of idling fuel consumption on vehicle fuel economy in different speed ranges.

[0132] Figure 7 and Figure 8 The fuel consumption of vehicles per 100 kilometers with and without idling fuel consumption are shown under different PnG speed fluctuation ranges and different average speed conditions. Figure 7 From the data, we can observe the following trends:

[0133] (1) With the increase of PnG speed fluctuation, the fuel consumption per 100 kilometers of vehicles at various average speeds generally shows a change pattern of first decreasing and then stabilizing. Specifically, when the idle fuel consumption is included, when the speed fluctuation exceeds 12km / h, the impact on fuel consumption under medium and low speed conditions tends to be weak. On the contrary, when the idle fuel consumption is not included, the impact of speed fluctuation on fuel consumption is further weakened. When the fluctuation reaches or exceeds 10km / h, the impact on fuel consumption in the three speed ranges of high, medium and low is not significant.

[0134] (2) Further comparative analysis of the curves in the two figures revealed that the curve with idle fuel consumption is denser than the curve without idle fuel consumption. This indicates that idle fuel consumption contributes more to the fuel consumption per 100 kilometers in the low and medium speed range, while its impact is relatively small in the high speed range. The main reason for this phenomenon is that idle fuel consumption is relatively stable and is less affected by vehicle speed fluctuations. As vehicle speed increases, overall fuel consumption increases, thereby relatively reducing the proportion of idle fuel consumption in total fuel consumption. Therefore, it can be concluded that the impact of idle fuel consumption on vehicle fuel economy shows significant differences in different speed ranges.

[0135] Fig. 9 and Fig.10The surface analysis shown provides an intuitive perspective for understanding the overall impact trend of the PnG average speed and its speed fluctuation on the fuel consumption per 100 kilometers. In this figure, the top of each figure shows the surface of the fuel consumption per 100 kilometers, and the plane at the bottom is the projection of the surface, so that we can clearly observe how the fuel consumption per 100 kilometers changes with the changes in the PnG average speed and speed fluctuation. Fig. 9 and Fig.10 The following overall trends can be observed:

[0136] (1) As the average vehicle speed increases, the fuel consumption per 100 kilometers also increases, a trend similar to the performance of the vehicle in non-PnG mode. When driving at high speeds, the increase in air resistance and the increase in engine load are the main reasons for the increase in fuel consumption. This shows that regardless of the driving mode, high-speed driving will result in higher fuel consumption.

[0137] (2) In the low and medium speed range, the speed fluctuation has little effect on the fuel consumption per 100 kilometers, especially when the idling fuel consumption is eliminated. However, when the speed fluctuation is small, the fuel consumption per 100 kilometers in the high-speed range will increase significantly. This phenomenon may be due to the frequent acceleration and deceleration operations of the vehicle at a small speed fluctuation, which will reduce fuel efficiency.

[0138] Therefore, the analysis results show that in order to optimize the fuel economy in the PnG control mode, an appropriate vehicle speed range and appropriate speed fluctuation range should be selected. The appropriate speed range can ensure that the vehicle operates within an efficient working range, while the appropriate speed fluctuation range helps to reduce unnecessary acceleration and deceleration, thereby reducing overall fuel consumption.

[0139] In practical applications, the PnG control strategy should take into account the specific conditions of the vehicle, including engine efficiency, vehicle load, road conditions and other factors, to determine the most economical speed range and speed fluctuation range. In this way, the vehicle's fuel efficiency can be effectively improved and fuel consumption can be reduced.

[0140] The fuel saving rate curve is obtained by comparing the fuel consumption per 100 kilometers in PnG mode with that in the corresponding constant speed driving conditions. Figures 11 to 14 The fuel saving rate under different PnG average speeds and different speed fluctuations is shown. The following trends can be observed from the figure:

[0141] As the average PnG speed increases, the fuel saving rate shows an obvious downward trend regardless of whether the taxiing segment includes idling fuel consumption (see Fig.11 and Fig.12), the fuel saving rates with and without idling fuel consumption dropped to -47.7% and -30.0% respectively. This shows that at higher speeds, the fuel saving effect of the PnG mode is not as significant as at low speeds, and beyond a certain range, it will even further increase energy consumption.

[0142] In the speed range below 60km / h, the fluctuation of fuel saving rate is mainly affected by the gear configuration. Some PnG average speed values ​​are in the gear shift speed range, indicating that in the medium and low speed range, especially in the low speed range, the fuel saving rate is very sensitive to the gear. In the speed range above 60km / h, the shapes of the two groups of curves (including idle speed and excluding idle speed) are basically the same (see Fig.11 and Fig.12 ), indicating that within this speed range, the effect of gear configuration on fuel economy is weakened.

[0143] When the average speed reaches 100km / h, the fuel saving rate curve has a peak (see Fig.11 and Fig.12 ), the gear in the high-speed section has reached the highest gear and has not changed. This should be related to the engine reaching the highest efficiency area at this speed.

[0144] As the speed fluctuation increases, the fuel saving rate increases (see 13 and Fig.14 ), but at high speeds, smaller speed fluctuations will lead to additional fuel consumption, which is higher than the energy consumption of constant speed driving. This is probably because the vehicle's driving resistance is larger at high speeds, and smaller speed fluctuations often make it difficult for the engine to enter a high-efficiency working range. Of course, this may also be related to the fact that discrete gear vehicles are not designed to match more appropriate gears at high speeds.

[0145] When the average speed and speed fluctuation range are exceeded, the fuel saving rate becomes negative (see Figures 11 to 14 ). This means that the vehicle energy consumption in PnG mode is higher than the energy consumption under the corresponding constant speed condition, so it is no longer energy-saving.

[0146] Fig.15 and Fig.16 The comprehensive impact of average vehicle speed and speed fluctuation on fuel consumption rate is shown. From the overall trend of the fuel saving rate curve, we can see that:

[0147] In the medium and low speed section, under the conditions of different speed fluctuation amplitudes, there is a large area of ​​operating conditions (the area above the zero reference surface) that enables the vehicle to show a good energy-saving effect. This means that when the vehicle is driving at medium and low speeds, by properly controlling the speed fluctuation, better fuel economy can be achieved. At the same time, the fuel saving rate decreases with the decrease in the speed fluctuation amplitude, but the reduction is more significant in the high-speed section, which shows that the speed fluctuation amplitude has no significant effect on the fuel saving rate as a whole. It only needs to make the speed fluctuation amplitude exceed a certain range (more than 6 to 8 km / h in the medium and low speed section) to achieve a more ideal energy-saving effect. This is mainly because in the medium and low speed section, the engine has more energy-saving potential to be tapped. By matching the gear position and the speed fluctuation amplitude, it is easier to make the engine run in the efficient working range, and moderate speed fluctuations help to make full use of this advantage.

[0148] In the high-speed section, when the vehicle includes idle fuel consumption while coasting, its energy-saving area is relatively small. This means that when coasting at high speeds, the existence of idle fuel consumption limits the ability of the PnG mode to improve fuel efficiency. Compared with the case without idle fuel consumption, the increase in energy consumption in the non-energy-saving area of ​​the high-speed section (that is, the area where the fuel consumption is higher than the uniform speed condition) is greater when idle fuel consumption is included. This shows that idle fuel consumption has a significant negative impact on fuel efficiency when driving at high speeds. In the high-speed section, if idle fuel consumption is not taken into account, the area of ​​increased fuel consumption in the PnG mode is relatively small, mainly appearing in the area of ​​higher vehicle speeds and lower speed fluctuation ranges. This shows that in the absence of idle fuel consumption, the PnG mode still has the potential to reduce fuel consumption in the high-speed section.

[0149] Fig.17 and Fig.18 The PnG average speed and speed fluctuation amplitude have a comprehensive impact on the energy efficiency conversion amount. The energy efficiency conversion amount is an important indicator that reflects the vehicle driving distance that can be driven by unit energy consumption, that is, the energy utilization efficiency. As can be seen from the figure, the overall trend of the energy efficiency conversion amount is similar to the overall trend of the fuel saving rate. This means that the energy efficiency conversion amount can be used as an effective indicator to evaluate the fuel economy of vehicles under different driving modes.

[0150] In the case of including idling fuel consumption, the energy efficiency conversion in the medium and low speed areas is large (such as Fig.17 As shown in the figure, the speed fluctuation amplitude has little effect on the energy efficiency conversion amount, while its value decreases significantly in the high speed and small speed fluctuation amplitude areas. Fig.18It can be seen that for the case without idling fuel consumption, the energy efficiency conversion amount changes significantly with the average speed, which shows that in the case of no idling fuel consumption, the average speed of the vehicle is the key factor affecting the energy utilization efficiency. As the speed increases, the engine may need to consume more energy to overcome the increased air resistance and other driving resistance. The energy efficiency conversion amount is less affected by the speed fluctuation amplitude.

[0151] From the above analysis, it can be seen that when the speed fluctuation amplitude exceeds 6-8 km / h in the medium and low speed section, or exceeds 10-12 km / h in the high speed section, increasing the speed fluctuation amplitude contributes very little to energy saving, while excessive speed fluctuation amplitude will not only affect riding comfort, but also may cause traffic safety problems. Referring to the research of relevant literature, the typical working condition with a speed fluctuation amplitude of 10% of the PnG average speed is analyzed, and it can be obtained that Fig.19 and Fig. 20 Two sets of curves.

[0152] Fig.19 The data shows that when the speed fluctuation is maintained at 10% of the average speed, as the PnG average speed increases, the fuel consumption per 100 kilometers shows a gradual upward trend. Specifically, when the average speed exceeds the threshold of 100km / h, the fuel consumption under the PnG condition begins to be higher than that under the uniform speed condition. This phenomenon is Fig. 20 It can also be displayed intuitively.

[0153] The core mechanism of PnG mode to achieve energy saving is that it can make the engine run in the most efficient range. Fig.21 The engine efficiency distribution diagram under different PnG average speeds and speed fluctuation amplitudes is shown. It can be seen that when the PnG average speed is around 100km / h, the engine efficiency reaches its peak, which is exactly Fig.21 The fundamental reason for the peak at the corresponding position in the fuel saving rate curve. Although the engine efficiency decreases slightly in the medium and low speed area, it still maintains a high level overall, which forms the basis for the significant energy-saving effect of the PnG mode. However, in a certain area of ​​the low-speed section (around 40km / h) and in areas with a small speed fluctuation, the engine's operating efficiency is relatively low. This phenomenon not only reveals that the PnG mode still has potential to be tapped in terms of energy saving, but also shows that the design of the experimental vehicle is more suitable for high-speed working conditions. By optimizing the matching design of the engine and the power system, the vehicle can be more adapted to the working environment of the medium and low speed sections.

[0154] In summary, if the vehicle achieves zero fuel consumption in the engine during the coasting phase, the overall energy-saving performance of the PnG mode in the medium and low speed range will be significantly improved. However, as the vehicle speed increases, its energy-saving effect gradually weakens compared to the uniform speed condition. Therefore, in order to maximize the energy-saving potential of the PnG mode, a strategy should be adopted to disconnect the transmission system from the wheels during the coasting phase, and ensure that the engine stops consuming fuel during this period. In addition, for the speed fluctuation amplitude, whether from the perspective of actual energy-saving effect, ride comfort or safety, the larger the better, it is necessary to seek the best balance point under comprehensive constraints.

[0155] The energy consumption change in PnG mode is affected by many factors, and it is crucial to analyze which factors have a significant impact on fuel consumption. By analyzing a series of PnG operating status data in the joint simulation, the correlation coefficient matrix is ​​used to evaluate the correlation between performance indicators and vehicle energy consumption under different driving conditions.

[0156] The Shapiro-Wilk normality test of the experimental data showed that the experimental data did not conform to the normal distribution. Therefore, it was decided to add the Spearman rank correlation coefficient matrix analysis on the basis of using the Pearson correlation coefficient matrix to evaluate the correlation.

[0157] After logarithmic transformation of the test data that does not conform to the normal distribution, the processed data that conforms to the normal distribution is obtained, and then the Pearson correlation coefficient matrix is ​​drawn, as shown in Fig. 22 As shown in the Pearson correlation coefficient matrix, it can be seen that there are many factors that affect vehicle energy consumption in the PnG mode.

[0158] The correlation coefficients of P-segment acceleration with fuel consumption per 100 kilometers, fuel saving rate, and energy efficiency conversion are -0.95, 0.9, and 0.95, respectively. The greater the P-segment acceleration, the lower the fuel consumption per 100 kilometers, the higher the fuel saving rate, and the higher the energy efficiency conversion. A higher P-segment acceleration means that the engine has more opportunities to operate in a high-efficiency area. At the same time, within a certain average speed range, compared with a uniform speed condition, it can achieve better energy-saving effects and a longer mileage with the same energy consumption.

[0159] The correlation coefficients between engine speed and fuel consumption per 100 kilometers, fuel saving rate, and energy efficiency conversion are 0.89, -0.88, and -0.89, respectively. This means that the higher the engine speed, the higher the fuel consumption per 100 kilometers, and the lower the fuel saving rate and energy efficiency conversion. Higher engine speeds are usually accompanied by high loads, and the higher efficiency area of ​​the engine usually corresponds to a certain engine speed range. Too high an engine speed often means that the engine is out of the high-efficiency working range, and fuel consumption increases.

[0160] The correlation coefficients between the transmission gear and the fuel consumption per 100 kilometers, fuel saving rate, and energy efficiency conversion are 0.88, -0.80, and -0.88, respectively. The higher the transmission gear, the higher the fuel consumption per 100 kilometers, and the lower the fuel saving rate and energy efficiency conversion. The impact of the increase in transmission gear on energy consumption here is mainly reflected in that as the gear increases, the average speed of the vehicle also increases accordingly, which requires the engine to have a higher power output, which in turn leads to an increase in energy consumption. For a fixed average speed, the increase in gear has a certain energy-saving effect, so the situation where the increase in gear leads to an increase in energy consumption is more inclined to the macroscopic vehicle operation condition, which is corresponding to the speed increase.

[0161] The correlation coefficients between the proportion of acceleration time and fuel consumption per 100 kilometers, fuel saving rate, and energy efficiency conversion are 0.99, -0.95, and -0.99, respectively. The higher the proportion of acceleration time, the higher the fuel consumption per 100 kilometers, and the lower the fuel saving rate and energy efficiency conversion. The proportion of acceleration time is related to the P-segment acceleration. The larger the proportion of acceleration time means the smaller the P-segment acceleration, and the smaller the P-segment acceleration, the longer the vehicle travels in the low-speed and medium-speed ranges, and the engine is more likely to work in a lower efficiency area, thereby increasing energy consumption.

[0162] The correlation coefficients between transmission efficiency and fuel consumption per 100 kilometers, fuel saving rate, and energy efficiency conversion are 0.80, -0.71, and -0.80, respectively. The higher the transmission efficiency, the higher the fuel consumption per 100 kilometers, and the lower the fuel saving rate and energy efficiency conversion. Changes in transmission efficiency usually change with changes in the gear position of the transmission, and its impact on energy consumption is also consistent with changes in the gear position, and changes in the gear position usually mean higher vehicle speeds.

[0163] The correlation coefficients between the PnG average speed and the fuel consumption per 100 kilometers, fuel saving rate, and energy efficiency conversion are 0.98, -0.92, and -0.98, respectively. The higher the PnG average speed, the higher the fuel consumption per 100 kilometers, and the lower the fuel saving rate and energy efficiency conversion. Consistent with the above content, the increase in average speed means higher engine power output and higher driving resistance, which leads to increased fuel consumption, and lower fuel saving rate and energy efficiency conversion.

[0164] Through the analysis of the Pearson correlation coefficient matrix, it can be seen that in order to reduce the vehicle's energy consumption, the P-segment acceleration should be increased, the proportion of the vehicle's acceleration segment operation time should be reduced, the gear should be reasonably selected, and the engine speed should be controlled so that it can operate in the high-efficiency range as much as possible. Through the above analysis, it can be seen that there are cross-influences and correlations between the main influencing factors.

[0165] The Spearman correlation coefficient focuses on the rank order relationship and is suitable for non-normal distribution or rank data. The generated rank correlation coefficient matrix is ​​as follows Fig.23As shown. From the Spearman rank correlation coefficient matrix, it can be seen that the following parameters have a greater impact on the energy consumption of the engine.

[0166] The correlation coefficients between P-segment acceleration and fuel consumption per 100 kilometers, fuel saving rate, and energy efficiency conversion are -0.95, 0.93, and 0.95, respectively. The greater the P-segment acceleration, the lower the fuel consumption per 100 kilometers, the higher the fuel saving rate, and the higher the energy efficiency conversion.

[0167] The correlation coefficients between engine speed and fuel consumption per 100 kilometers, fuel saving rate, and energy efficiency conversion are 0.92, -0.91, and -0.92, respectively. This means that the higher the engine speed, the higher the fuel consumption per 100 kilometers, and the lower the fuel saving rate and energy efficiency conversion.

[0168] The correlation coefficients between transmission gear position and fuel consumption per 100 kilometers, fuel saving rate, and energy efficiency conversion are 0.89, -0.88, and -0.89, respectively. The higher the transmission gear position, the higher the fuel consumption per 100 kilometers, and the lower the fuel saving rate and energy efficiency conversion.

[0169] The correlation coefficients between the proportion of acceleration time and fuel consumption per 100 kilometers, fuel saving rate, and energy efficiency conversion are 1.00, -0.99, and -1.00, respectively. The higher the proportion of acceleration time, the higher the fuel consumption per 100 kilometers, and the lower the fuel saving rate and energy efficiency conversion.

[0170] The correlation coefficients between powertrain efficiency and fuel consumption per 100 kilometers, fuel saving rate, and energy efficiency conversion are 0.80, -0.76, and -0.80, respectively. The higher the powertrain efficiency, the higher the fuel consumption per 100 kilometers, and the lower the fuel saving rate and energy efficiency conversion.

[0171] The correlation coefficients between the PnG average speed and the fuel consumption per 100 kilometers, fuel saving rate, and energy efficiency conversion are 0.99, -0.98, and -0.99, respectively. The higher the PnG average speed, the higher the fuel consumption per 100 kilometers, and the lower the fuel saving rate and energy efficiency conversion.

[0172] By comparing the analysis results of the two correlation coefficient matrices, it is found that both show a significant correlation between P-segment acceleration, engine speed, transmission gear, acceleration time ratio, transmission efficiency, PnG average speed and fuel consumption. The difference is that the correlation strength between some variables in the Spearman correlation coefficient matrix is ​​slightly different from that in the Pearson correlation coefficient matrix. For example, the correlation between the acceleration time ratio and fuel consumption is more obvious in the Spearman correlation coefficient.

[0173] Through the above correlation analysis, it is found that the speed fluctuation amplitude has a weak effect on engine energy consumption, and the maximum correlation coefficient between it and the fuel saving rate and energy efficiency conversion is only 0.15. This is consistent with the analysis of the above joint simulation results, indicating that increasing the speed fluctuation amplitude is not ideal for reducing energy consumption.

[0174] This application first systematically analyzes the concept, classification and energy-saving mechanism of the PnG strategy. On this basis, a vehicle dynamics model, a vehicle driving energy demand model and a vehicle energy consumption model are established, and a vehicle fuel consumption model under the PnG mode is further constructed. In order to numerically solve the vehicle energy consumption, the Willans model is introduced and elaborated in detail. Based on the Willans model, a complete vehicle fuel consumption model and a vehicle energy consumption model under the PnG mode are established.

[0175] This application has built a joint simulation platform of CarSim and MATLAB / Simulink, and based on this platform, simulated, analyzed and studied the vehicle energy consumption conditions under different PnG average speeds and different speed fluctuation amplitudes. Through the analysis of the test data, the energy-saving effects of the vehicle under different PnG average speeds and different speed fluctuation amplitudes were obtained, and the influence of whether the vehicle consumes fuel in the G segment under the PnG mode on the vehicle energy consumption was analyzed. The correlation between the various variables in the test data was analyzed, and the relevant factors affecting the energy-saving effect of the PnG mode were found.

[0176] The simulation results show that compared with the uniform speed operation condition, the PnG mode can achieve a more obvious fuel saving effect in the medium and low speed sections, but as the average speed of the PnG increases, the fuel saving effect gradually weakens. For the case of idling fuel consumption, when the vehicle speed exceeds a certain level in the high speed section, the energy consumption of the PnG mode is higher than that of the uniform speed operation condition. Except for the smaller speed fluctuation amplitude, other speed fluctuation amplitudes have little effect on the overall energy saving effect of the PnG mode operation.

[0177] For the fuel consumption of fuel vehicles, the goal is to minimize the amount of fuel consumed by the vehicle for a certain mileage under certain constraints. Therefore, J is defined as the total fuel consumption of the entire journey, which can be obtained by the fuel mass flow rate of the engine in a given time.

[0178]

[0179] Among them, H f is the lower calorific value of the fuel. Substitute equation (15) into equation (33) and replace the engine speed function ω e (t) is converted into the velocity function v(t), that is, further substituting formula (21) into it, we can get:

[0180]

[0181] Where a p (t) is the vehicle traction acceleration, and a p (t) = F a(t) / m, in order to maximize energy saving, the fuel cut-off strategy is adopted, and the energy loss caused by restoring fuel supply is ignored, then:

[0182]

[0183] Formula (34) establishes the relationship between fuel consumption rate and speed and acceleration, that is, it establishes the relationship between fuel consumption rate and engine torque.

[0184] From the formula, we can see that the engine gear position also has a great impact on the vehicle energy consumption, so the shifting rules preset by the selected transmission in CarSim are used for the subsequent numerical calculations. Then the optimal energy consumption control problem is:

[0185]

[0186] Where t f is the end time of the trip, v i is the initial speed of the stroke, v f is the speed at the end of the stroke, s f is the travel distance. By numerically solving the minimum integral value, the vehicle speed curve corresponding to the vehicle travel with the lowest energy consumption can be obtained.

[0187] There are many constraints on the system state and control quantities in formula (35). The solution of the dynamic programming algorithm needs to be carried out under these constraints. These constraints mainly include speed constraints, acceleration constraints, torque constraints, and distance constraints.

[0188] (1) Speed ​​constraints

[0189] Vehicles traveling on the road are subject to speed constraints in two aspects: one is the limitation of the vehicle's own performance, and the other is the speed limit of the road section where the vehicle is traveling. For example, expressways have minimum and maximum speed limits.

[0190] In this application, v i is the vehicle speed at the start of the trip, v f is the speed at the end of the trip. Usually, these two speeds are 0, and the lowest speed v min , maximum speed v max , the speed of the vehicle at any time during the journey is v(t), then for .

[0191] v min (t,s(t))≤v(t)≤v max (t,s(t)) (36)

[0192] (2) Acceleration constraint

[0193] Similar to speed constraints, acceleration constraints are also limited by the vehicle's own performance or vehicle control mode. As we all know, the vehicle has better acceleration performance in power mode, but excessive acceleration will lead to greater energy consumption. At the same time, excessive acceleration will also lead to poor comfort for passengers in the vehicle; while too small acceleration will increase the travel time. Therefore, it is necessary to comprehensively consider the vehicle's acceleration performance, comfort and fuel economy. Definition a p,min and a p,max are the minimum and maximum traction accelerations of the vehicle, respectively. Then the acceleration a at any time p (t) Constraints need to be met:

[0194] a p,min (v(t),t)≤a p (t)≤a p,max (v(t),t) (37)

[0195] (3) Torque constraint

[0196] On the one hand, the characteristics of the engine determine that it has a maximum output torque limit. On the other hand, the dynamic programming algorithm will calculate the engine torque when changing from one state to the next during the solution process. If this torque exceeds the maximum torque that the engine can provide, the state change cannot be completed. Let T e,max is the maximum engine torque, T e,min It is the minimum torque of the engine, which is the minimum torque when the engine maintains the lowest speed for stable operation.

[0197] (4) Distance constraint

[0198] The distance constraint is the mileage of a vehicle trip, s(t) is the trip distance, and the maximum and minimum mileage can be set according to the needs of the research. Then s(t) needs to satisfy

[0199] s min (t)≤s(t)≤s max (t) (38)

[0200] (5) Braking acceleration constraint

[0201] The braking acceleration constraint has requirements for both the vehicle's own characteristics and braking performance, as well as riding comfort and other aspects. However, in emergency braking situations, the vehicle's a b Should be less than or equal to the maximum braking deceleration a b,max , when braking is not required, or the vehicle is in a gliding state, and there is no engine braking and energy recovery, the minimum braking deceleration can be 0. The specific operating conditions of the vehicle will vary. b (t) Need to be satisfied

[0202] 0≤a b (t)≤a b,max (39)

[0203] In a PnG segment, the initial speed and terminal speed of the vehicle are the same. For PnG control strategies with different speed fluctuation amplitudes and different P segment accelerations, the energy-saving effect can be measured by "fuel consumption per unit distance". Based on maximizing the energy-saving effect of the PnG strategy, the vehicle cuts off fuel in the coasting segment, and the PnG strategy energy-saving optimal control problem is:

[0204]

[0205]

[0206] Then the optimal energy consumption speed and the corresponding optimal gear are:

[0207]

[0208] In order to verify the optimal energy consumption speed optimization algorithm constructed above, this application designed a comprehensive test condition including a ramp, and the vehicle ran for a total of 1200m in the entire condition. The road conditions are described as follows:

[0209] (1) 0-200 m: horizontal straight road section; (2) 200-300 m: downhill section, road slope 0.05; (3) 300-700 m: horizontal straight road section; (4) 700-900 m: uphill section, road slope 0.05; (5) 900-1200 m: horizontal straight road section;

[0210] The vehicle initial speed is 0km / h, the terminal speed is 0, and the acceleration range is -3 to 3m / s2. The speed range is 0 to 100km / h. The road slope curve is shown in the figure. The optimized optimal energy consumption speed curve is as follows: Fig.24 and Fig.25 shown.

[0211] from Fig.25 It can be seen that the vehicle speed will be adjusted as the road slope changes, indicating that changes in road load have a greater impact on the vehicle's optimal energy-efficient operating speed. Based on the navigation map with road slope information, the corresponding vehicle's optimal energy-efficient operating speed curve can be planned, and the corresponding optimized speed can be used as the target speed for ACC cruising. The average speed of the example is 35.2km / h. Compared with the corresponding uniform speed driving condition, the fuel efficiency is improved by 11.6%.

[0212] It should be noted that the specific implementation is only an explanation and description of the technical solution of the present invention, and cannot be used to limit the scope of protection of the rights. Any partial changes made according to the claims and description of the present invention should still fall within the scope of protection of the present invention.

Claims

1. A method for optimizing automobile energy efficiency based on PnG mode, characterized in that The following steps are involved: Step 1: Get the net wheel force F of the vehicle w (t), wheel radius r w , transmission ratio i e,g and the transmission system efficiency η t , and according to the net wheel force F w (t), wheel radius r w , transmission ratio i e,g and the transmission system efficiency η t , get the engine torque T e (t); Step 2: Get the vehicle speed v(t) and combine it with the wheel radius r w and transmission ratio i e,g , get the speed ω e (t); Step 3: Obtain the minimum engine power P e,min and engine efficiency η e , and the engine torque T e (t), speed ω e (t), minimum engine power P e,min and engine efficiency η e Input the Willans model to obtain the power P generated by fuel consumption f (t); Step 4: Power P generated based on fuel consumption f (t), and combined with the operating mechanism of the PnG mode, the energy consumption E of the vehicle trip in the PnG mode is obtained PnG Model; Step 5: Obtain the vehicle's net driving force F a (t), and the vehicle net driving force F a (t), engine torque T e (t), wheel radius r w , transmission system efficiency η t And the transmission ratio i e,g , input the Willans model to get the fuel consumed for the mileage Step 6: Obtain the total fuel consumption J and trip end time t for the entire trip f , initial stroke speed v i , speed v at the end of the stroke f and travel distance f , and the amount of fuel consumed by the mileage As the objective function, the optimal energy consumption control problem is constructed; Step 7: Use the total fuel consumption J and the trip distance s for the entire trip f , get the fuel consumption per unit distance; Step 8: Based on the unit distance fuel consumption and combined with the optimal energy consumption control problem, the unit energy consumption control problem is constructed, that is, the PnG mode energy-saving optimal control problem; Step 9: Solve the PnG mode energy-saving optimal control problem to obtain the optimal speed and gear.

2. The method for optimizing automobile energy efficiency based on the PnG mode according to claim 1 is characterized in that The net wheel force F w (t) is expressed as: C0=C rr mgcosθ+mgsinθ C1＝0 Among them, C0, C1, C2 are road load coefficients, C rr is the rolling resistance coefficient, θ is the road slope angle, ρ a is the air density, A c is the frontal area of ​​the vehicle, C D is the air resistance coefficient, m is the sum of the vehicle's curb weight and the weight of its occupants and cargo, and g is the acceleration due to gravity.

3. The method for optimizing automobile energy efficiency based on the PnG mode according to claim 2 is characterized in that The engine torque T e (t) is expressed as:

4. The method for optimizing automobile energy efficiency based on the PnG mode according to claim 3 is characterized in that The speed ω e (t) is expressed as:

5. The method for optimizing automobile energy efficiency based on the PnG mode according to claim 4 is characterized in that The power P f (t) is expressed as: Among them, k e,0 , k e,1 , k e,2 , k e,3 , k e,4 is the correlation coefficient.

6. The method for optimizing automobile energy efficiency based on the PnG mode according to claim 5 is characterized in that In the PnG mode, the energy consumption of the vehicle trip is E PnG The model is expressed as: Where n is the nth PnG segment, N is the total number of PnG segments, and t n,0 and t n,png The running time of the nth PnG segment is from t n,0 to n,png .

7. The method for optimizing automobile energy efficiency based on the PnG mode according to claim 6 is characterized in that The amount of fuel consumed for the stated mileage It is expressed as: Among them, H f is the lower calorific value of the fuel, a p (t) is the vehicle driving acceleration.

8. The method for optimizing automobile energy efficiency based on the PnG mode according to claim 7 is characterized in that The optimal energy consumption control problem is expressed as: Among them, a b (t) is the braking acceleration, s(t) is the distance traveled at time t, s min (t) is the minimum travel distance, s max (t) is the maximum travel distance, a p,min (v(t),t) is the minimum driving acceleration, a p,max (v(t),t) is the maximum driving acceleration, a b,max is the maximum braking deceleration, v min (t,s(t)) is the minimum instantaneous vehicle speed, v max (t,s(t)) is the maximum instantaneous vehicle speed.

9. The automobile energy efficiency optimization method based on the PnG mode according to claim 8 is characterized in that The PnG mode energy-saving optimal control problem is expressed as:

10. The automobile energy efficiency optimization method based on the PnG mode according to claim 9 is characterized in that The optimal speed and gear are expressed as: Among them, v c,opt To solve the optimal instantaneous speed, i e,c,opt To solve the optimal transmission ratio, v is the instantaneous vehicle speed.

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