CN116588114A - Gear shifting point optimization method for multi-gear electromechanical compound transmission system - Google Patents
Gear shifting point optimization method for multi-gear electromechanical compound transmission system Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
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- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
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- B60W50/00—Details of control systems for road vehicle drive control not related to the control of a particular sub-unit, e.g. process diagnostic or vehicle driver interfaces
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Abstract
The invention discloses a gear shifting point optimization method of a multi-gear electromechanical compound transmission system, and belongs to the field of hybrid electric vehicle transmissions. A parallel plug-in hybrid electric vehicle with a multi-gear electromechanical compound transmission system is selected as a research object, the speed, the pedal opening and the running mode are used as control parameters, the influences of the double power sources of an engine and a motor and the charge state of a battery are considered, on the basis of an initial gear shifting rule, the working efficiency of the system is optimized as a target, and the gear shifting speed under different pedal openings of different modes of a pure electric mode EV, a hybrid electric mode HEV, an engine independent driving mode Eng and a driving charging mode Chg is optimized offline by adopting a DIRECT global optimization method. Compared with other global optimization algorithms, the method can find the optimal solution in fewer iteration times, and improves the calculation efficiency, so that the overall fuel economy of the multi-gear hybrid electric vehicle is obviously improved.
Description
Technical Field
The invention relates to a hybrid electric vehicle transmission technology, in particular to a gear shifting point optimization method of a multi-gear electromechanical compound transmission system.
Background
The increasing of the automobile conservation amount causes the increasingly serious problems of energy shortage and environmental pollution, and brings serious challenges to the realization of the strategic targets of carbon peak and carbon neutralization in China. Therefore, the technical roadmap of the energy-saving and new energy automobile is proposed, and by 2035, the traditional energy passenger cars are all hybrid electric vehicles. Compared with the traditional vehicle, the excellent energy saving and power supply capacity of the hybrid electric vehicle is mainly influenced by two aspects, on one hand, the energy management strategy needs to be optimized, and on the other hand, a reasonable gear shifting strategy needs to be formulated, so that the engine and the motor work in a high-efficiency area. The quality of the shift strategy is largely dependent on the driveline, which may also be referred to as an electromechanical compound driveline. At present, an electromechanical composite transmission system which integrates a multi-gear motor and a transmission is adopted in a plug-in hybrid power system, so that not only can the drivability be obviously improved, but also the energy-saving performance can be obviously improved, and the system becomes one of the trends of hybrid power development. The design of improving the gear number of the electromechanical compound transmission system of the plug-in hybrid electric vehicle ensures that the whole vehicle structure is more compact, the performance is better, the control is convenient, and simultaneously, the engine and the motor work in a high-efficiency range, so that a reasonable gear shifting strategy is important for improving the economy, the dynamic property, the comfort and the like of the whole vehicle.
Conventional shift problem control is typically based on a power source static off-line shift schedule that is manually determined based on past experience or bench test calibration results. Because a large number of heuristic tests and adjustments are performed to realize optimal control of transmission, the method has strong effectiveness and robustness and plays an important role in industrial implementation. However, such a process is time consuming and costly and typically relies on expert knowledge, and requires extensive calibration work for application to a real vehicle. Furthermore, it is difficult to take full advantage of the potential of an integrally integrated electro-mechanical compound drive system to improve overall performance, which results in an optimal limitation to improving fuel economy and drivability. For the electromechanical composite transmission system structure with the motor and the transmission integrated, the working mode is required to be identified in the gear shifting process, so that the gear shifting smoothness is ensured. The whole process has the change of the working mode and the change of the system state under a certain mode, so that the switching of the working mode and the gear shifting strategy of the plug-in hybrid electric vehicle have typical coupling characteristics, and the preparation of the gear shifting rule of the multi-gear hybrid electric system is challenged.
Disclosure of Invention
The invention aims to improve the economical efficiency, the dynamic property and the comfort of the whole vehicle, and provides a gear shifting point optimization method of a multi-gear electromechanical composite transmission system, aiming at the reasonable gear shifting strategy requirement of a certain multi-gear parallel plug-in hybrid electric vehicle provided with an integrated electromechanical composite transmission system, taking the system comprehensive efficiency optimization and the battery charge-discharge balance as starting points, on the basis of analyzing the efficiency models of all parts, by establishing the efficiency models under different working modes and combining the advantages of a DIRECT global optimization algorithm, the invention provides an economical gear shifting strategy design method of energy management and gear shifting strategy coupling, improves the fuel economy of the vehicle and provides a new idea for the economical gear shifting strategy of the plug-in hybrid electric vehicle based on the integrated electromechanical composite transmission system.
The technical scheme adopted by the invention is a gear shifting point optimization method of a multi-gear electromechanical compound transmission system, which comprises the following steps: the system comprises a whole vehicle demand torque module, a mode judging module, a torque distribution module, a comprehensive efficiency calculation module of each mode system, an economical gear shifting rule making module of each mode, a DIRECT algorithm gear shifting rule optimizing module and a gear decision module. The whole vehicle demand torque module analyzes according to the opening degree of an accelerator pedal and a vehicle speed signal, the driving mode judging module judges that the vehicle is in a pure electric mode EV, a hybrid electric mode HEV, an engine independent driving mode Eng and a driving charging mode Chg according to the whole vehicle demand torque and the battery SOC, and the torque distribution module further solves the output torque of each component according to the torque threshold of different components and the vehicle working mode signal determined by the mode judging module. And the system comprehensive efficiency calculation module of each mode calculates the system comprehensive efficiency of each working mode according to the torque distribution of each mode. The initial economical gear shifting rule under each mode is formulated through traversal of the mechanical path gear, the electric path gear and the accelerator pedal opening. The DIRECT algorithm optimizing economy gear shifting rule module corrects the initial economy gear shifting rule through the DIRECT algorithm and outputs the optimized economy gear shifting rule to the gear decision module. And the gear decision module realizes gear switching of the mechanical road and the electric road in each mode according to the optimized economical gear shifting rule.
Preferably, the vehicle demand torque module is characterized in that due to the existence of a multi-gear electromechanical compound transmission system configuration hybrid gear, the mechanical circuit transmission ratio and the electric circuit transmission ratio are related to the working mode and the gear, meanwhile, the torques output by the engine and the motor are coupled in the gearbox, and the demand torque needs to be analyzed to the front end of the main speed reducer and converted into a function of the vehicle speed and the pedal opening.
Preferably, the input required by the drive mode determination module is the vehicle demand torque T r Battery SOC, vehicle speed v, mechanical road speed ratio i ge And electric speed ratio i gm The whole vehicle operation mode is divided into 5 modes: an electric-only mode EV, a hybrid-mode HEV, an engine-alone drive mode Eng, and a charging mode Chg. According to the required torque T r And judging that the vehicle enters a driving mode and a braking mode, and dividing the driving mode into a power consumption mode CD and a power maintenance mode CS according to the change process of the power battery power SOC.
Preferably, the torque distribution module considers the mechanical path speed ratio i due to the existence of the mixed gear of the multi-gear electromechanical compound transmission system ge And electric speed ratio i gm The coupling characteristics of the energy management and shift strategy are achieved by the difference between the torque thresholds of the engine and the electric machine, the engine's optimal fuel economy curve and the required torque.
Preferably, the system integrated efficiency calculation module calculates the power flow of the multi-gear electromechanical hybrid transmission system in the EV mode, the HEV mode, the Eng mode, and the Chg mode. The definition of the comprehensive efficiency of the whole vehicle system is as follows: the ratio of the output power to the input power of the system calculates the efficiency in different modes according to the flow directions of different power flows when the vehicle runs in different modes.
Preferably, the economic gear shifting rule making module of each mode obtains the gear shifting speed by traversing the gear, solving the intersection point of the system comprehensive efficiency of the adjacent gear in each mode, traversing the pedal opening, obtaining the gear shifting speed under different pedal openings, and making pedal opening-upshift rule curves under different modes. And acquiring a downshift law by adopting an equal delay type downshift strategy at a downshift speed difference of 6km/h, correcting a gear shift law curve according to a simulation result, and formulating and acquiring an initial economical upshift and gear shift law.
Preferably, optimizing the economy shift schedule based on the DIRECT global optimization algorithm includes the steps of:
(1) Determining the topological structure and the working mode of a multi-gear electromechanical compound transmission system, and establishing torque distribution of an engine and a motor in a vehicle driving mode;
(2) The method comprises the steps of determining a working mode judgment method of a hybrid electric vehicle of a mode judgment module according to an accelerator pedal and a vehicle speed signal, and transmitting a determined vehicle driving mode signal to a torque distribution module;
(3) Establishing a comprehensive efficiency model of the system under each working mode according to the working torque distributed by the engine and the motor;
(4) Traversing gear and pedal opening, solving the intersection point of the comprehensive efficiency curve of the system under the adjacent gear, and obtaining an initial gear shifting and upshift rule;
(5) Adopting an equal delay type downshift strategy, acquiring a downshift law at a downshift speed difference of 6km/h, and correcting a gear shift law curve according to a simulation result to acquire an initial economical upshift and downshift law;
(6) Aiming at the economical gear shifting rule, the gear shifting speed of adjacent gears under different pedal opening degrees of different modes is taken as an optimization variable, the optimal working efficiency of the system is taken as a target, the lifting gear threshold value of the initial gear shifting rule is taken as the constraint condition of each optimization variable under different pedal opening degrees, and an objective function is established. The constraint conditions comprise rotational speed and torque limit values of different power sources such as an engine, a motor and the like, a threshold value of a gear shifting vehicle speed under an initial economic gear shifting rule and working current and voltage limit values of a battery;
(7) Carrying out optimization solution in a feasible region by adopting a DIRECT method to obtain a speed interval in which gears work reasonably, and further updating an economical gear shifting rule;
preferably, in step (7), the shift speed under different pedal opening degrees of different modes is used as an optimization variable, and the difference between the front and rear efficiencies of the shift is optimized with the aim of optimizing the working efficiency of the system. Meanwhile, in the optimization process, the engine, the motor and other parts must be limited in the physical constraint range, and in order to improve the optimization efficiency, the optimal economical shift curves in all modes are adopted as the upper limit and the lower limit of the constraint conditions of all the optimization variables under different pedal opening degrees respectively.
Preferably, the gear shifting decision module takes the speed ratio of the engine, the speed ratio of the motor, the mode and the speed of the vehicle as inputs, firstly converts the speed ratio of the mechanical path and the speed ratio of the electric path into gears in each mode, then compares the current speed with the gear shifting speed formulated offline, and gradually carries out gear lifting so as to realize gear shifting decision.
The invention has the beneficial effects of meeting the requirement of a reasonable gear shifting strategy of a multi-gear parallel plug-in hybrid electric vehicle provided with an integrated electromechanical compound transmission system, taking the system comprehensive efficiency optimization and the battery charge-discharge balance as starting points, providing an economic gear shifting point optimization method of the multi-gear electromechanical compound transmission system, and further improving the fuel economy of the vehicle by establishing efficiency models under different working modes and combining the advantages of DIRECT global optimization algorithm on the basis of analyzing the efficiency models of all components.
Drawings
FIG. 1 is a schematic illustration of an economical shift point optimization for a multi-speed electromechanical compound transmission system.
Fig. 2 is a schematic illustration of the formulation of an economical shift schedule.
FIG. 3 is a schematic illustration of shift schedules in various modes;
wherein, (a) -pure electric mode, (b) -engine driving mode, (c) -hybrid mode, (d) -driving charging mode.
FIG. 4 is a schematic diagram of a multi-speed electromechanical compound transmission system topology.
Fig. 5 is a DIRECT algorithm optimization schematic.
FIG. 6 is an economy shift decision schematic.
Detailed Description
The invention will be further described with reference to the drawings and the specific examples.
FIG. 1 is a schematic diagram of an economical shift point optimization to be employed by an example of the present invention. The shift point optimization flow comprises the following steps: the system comprises a whole vehicle demand torque module, a driving mode judging module, a torque distribution module, a comprehensive efficiency calculation module of each mode system, an economical gear shifting rule making module of each mode, a DIRECT algorithm gear shifting rule optimizing module and a gear decision module.
The vehicle demand torque module is characterized in that due to the existence of a multi-gear electromechanical compound transmission system configuration hybrid gear, the transmission ratio of a mechanical circuit and an electric circuit is related to a working mode and the gear, simultaneously, the torque output by an engine and a motor is coupled in a gearbox, the demand torque needs to be analyzed to the front end of a main speed reducer, and is converted into a function of the vehicle speed and the pedal opening, and the function is expressed as:
T final_in ＝T e ·i ge +T m ·i gm (1)
T final_in ＝T r /i 0 (2)
T r ＝f r (acc)T max (n i ),0≤acc≤1 (3)
wherein T is final_in Is the torque of the input end of the main speed reducer, T e For engine output torque, T m For the motor to output torque, T r For the wheel end demand torque, i ge For mechanical path speed ratio, i gm For electric path speed ratio, i 0 Speed ratio of main speed reducer, n i Is the rotation speed of the input shaft of the main speed reducer, T max (n i ) The maximum torque value corresponding to the rotation speed of the input shaft, acc is the opening degree of an accelerator pedal, f r (acc) is a monotonically increasing function with respect to accelerator pedal opening, and satisfies:
f r (acc)∈[0,1],acc∈[0,1],f r (0)＝0,f r (1)＝1
the present study will be f r (acc) takes a linear relationship, namely:
T r ＝acc·T max (n i ),0≤acc≤1 (4)
according to the speed, mechanical path gear and electric path gear, the rotation speed of the input shaft of the main speed reducer can be determined to be
Wherein n is i The rotation speed of the input shaft of the main speed reducer is v, the vehicle speed is i gi The speed ratios of the mechanical path and the electric path corresponding to the rotation speed of the input shaft, i 0 The speed ratio of the main speed reducer is represented by r, and the radius of the wheel is represented by r.
Substituting formula (5) into formula (4) to obtain:
the input required by the drive mode judging module is the whole vehicle required torque T r Battery power SOC, vehicle speed v, mechanical path speed ratio i ge And electric speed ratio i gm The whole vehicle operation mode is divided into 5 modes: an electric-only mode EV, a hybrid-mode HEV, an engine-alone drive mode Eng, a charging mode Chg, and a braking mode. According to the required torque T r Judging that the vehicle enters a driving mode and a braking mode, and when the required torque T is r When the torque T is greater than zero, the mode determination module determines that the vehicle is operating in the driving mode r Less than zero, the vehicle is determined to be operating in a braking mode. Meanwhile, the driving mode is divided into a power consumption mode CD and power according to the change process of the power battery power SOCThe quantity maintenance mode CS. When SOC is greater than SOC obj When the SOC is smaller than or equal to the SOC, the battery is in the power consumption mode obj When the battery is in the charge sustaining mode.
In order to further explain the economical gear shifting point method provided by the embodiment of the invention, a plug-in hybrid electric vehicle based on a multi-gear electromechanical composite transmission system structure is taken as a research object, the transmission system structure is shown in fig. 4, the structure mainly comprises an engine, a motor, a single clutch and an AMT gearbox arranged at P2.5, the engine and the motor are respectively connected with the AMT through two shafts, two torque transmission paths which are independent to wheels are provided, a mechanical path connected with the engine and an electric path connected with the motor are provided, and the motor is always connected with an output shaft. The AMT realizes torque coupling while changing speed and torque, and the mechanical road gear and the electric road gear are alternately upshifted, so that continuous power output can be realized. For the hybrid vehicle driveline shown in fig. 4, the shift point optimization method employed includes the steps of:
(1) And determining the topological structure of the multi-gear electromechanical composite transmission system, and solving the output torque of other components according to the torque thresholds of different components and the vehicle working mode signals determined by the mode judging module. At the same time, the mechanical speed ratio i is considered ge And electric speed ratio i gm The coupling characteristics of energy management and gear shifting strategies are realized, and the torque distribution of an engine and a motor in a vehicle driving mode is established as follows:
table 1 torque distribution strategy
Wherein SOC > 0.3 represents that the battery remaining power is more than 30%, SOC is less than or equal to 0.3 represents that the battery remaining power is less than or equal to 30%, CD/CS-EV represents a pure electric driving mode under a power consumption CD and a power maintenance mode CS, CD/CS-HEV represents a hybrid driving mode under the power consumption CD and the power maintenance mode CS, CS-Eng represents a pure engine driving mode under the power maintenance mode CS, and CS-Chg represents a driving charge under the power maintenance mode CSElectric mode, braking represents Braking mode, T r The torque and T are required for driving the whole vehicle mmax For maximum output torque, T of motor emax For maximum output torque, T of engine eopt I is the minimum fuel consumption rate of the engine, namely the optimal output torque ge For mechanical path speed ratio, i gm Is an electric path speed ratio.
(2) And the system comprehensive efficiency calculation module of each mode calculates the system comprehensive efficiency of each working mode according to the torque distribution of each mode. Through traversal of mechanical path gear, electric path gear and pedal opening, an initial economical gear shifting rule under each mode is formulated, a process for formulating an economical gear shifting rule curve is shown in fig. 2, and a gear shifting rule schematic diagram under each mode is shown in fig. 3. The comprehensive efficiency calculation module of each mode system calculates eta according to the power flows in EV mode, HEV mode, eng mode and Chg mode EV 、η HEV 、η Eng 、η Chg The efficiency in the pure electric mode, the efficiency in the hybrid mode, the efficiency in the engine single driving mode and the efficiency in the driving charging mode are respectively as follows:
wherein P is e For engine power, P m Is the motor power eta e For engine efficiency, eta m_motor For motor electric efficiency, eta m_charge The charging efficiency of the motor is obtained by calculating or looking up the working points of the engine and the motor, eta bat For battery charge-discharge efficiency, eta T For driveline efficiency, 0.9 is defined.
(3) Traversing gear and pedal opening, solving the intersection point of the comprehensive efficiency curve of the system under the adjacent gear, and obtaining an initial gear shifting and upshift rule; adopting an equal delay type downshift strategy, acquiring a downshift law at a downshift speed difference of 6km/h, and correcting a gear shift law curve according to a simulation result to acquire an initial economical gear shift law;
(4) Aiming at the economical gear shifting rule, the gear shifting speed of adjacent gears under different pedal opening degrees of different modes is taken as an optimization variable, the optimal working efficiency of the system is taken as a target, the lifting gear threshold value of the initial gear shifting rule is taken as the constraint condition of each optimization variable under different pedal opening degrees, and the established objective function is as follows:
wherein J is an objective function with optimal system working efficiency, cost η As a cost function of efficiency, u i For the shift point, i represents the pedal opening, j represents the gear, P b For battery power, EV/Eng/HEV represents the electric-only drive/engine-only drive/hybrid drive mode, respectively, and Chg represents the traction charging mode. The combination of each gear shifting point in each mode reflects the speed interval of each gear operation, and the reasonable speed interval can enable the multi-gear parallel plug-in type hybrid electric vehicle to operate in a high-efficiency interval.
The constraint conditions comprise the rotation speed and torque limit values of different power sources such as an engine and a motor, and the working current and voltage limit values of a battery, and because of more optimization variables, in order to reduce the optimization operand, the optimal solution is quickly obtained, the optimization efficiency is improved, and the optimal economic upshift curve under each mode is adopted as the upper limit and the lower limit of the constraint conditions of each optimization variable under different pedal opening degrees. The constraint is expressed as:
ω e for engine speed, ω m Is the rotation speed of the motor, T e For engine torque, T m For motor torque, I bat U is the working current of the battery bat For the operating voltage of the battery, "min" in the subscript indicates the lower limit of the term value, and "max" in the subscript indicates the upper limit of the term value.
(5) And carrying out optimization solving in a feasible domain by adopting a DIRECT algorithm, and normalizing the values of the shift points as shown in fig. 5, so that the variable space is changed into an n-dimensional hypercube. Firstly, calculating a function value at a central point of a variable space, then continuously dividing the variable space, comparing the function values at the central points of the divided subspaces to obtain a local optimal efficiency value, and finally obtaining a global optimal efficiency value, thereby obtaining a speed interval for reasonable gear operation.
(6) The engine speed ratio, the motor speed ratio, the mode and the vehicle speed are used as inputs, the mechanical road speed ratio and the electric road speed ratio are firstly converted into gear positions in each mode, then the current vehicle speed is compared with the gear shifting vehicle speed formulated offline, and the gear lifting is gradually carried out, so that gear position decision is realized, as shown in fig. 6.
In the description of the present specification, reference to the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: many changes, modifications, substitutions and variations may be made to the embodiments without departing from the spirit and principles of the invention, the scope of which is defined by the claims and their equivalents.
Claims (8)
1. The method for optimizing the gear shifting point of the multi-gear electromechanical compound transmission system is characterized by comprising the following steps of: the system comprises a whole vehicle demand torque module, a driving mode judging module, a torque distribution module, a comprehensive efficiency calculation module of each mode system, an economical gear shifting rule making module of each mode, a DIRECT algorithm gear shifting rule optimizing module and a gear decision module; the system comprehensive efficiency calculation module calculates the comprehensive efficiency of the system in each working mode according to the torque distribution in each mode, and establishes an initial economical shifting rule in each mode through the traversal of a mechanical path gear, an electric path gear and the accelerator pedal opening, the DIRECT algorithm optimizing economical shifting rule module corrects the initial economical shifting rule through the DIRECT algorithm and outputs the optimized economical shifting rule to the gear decision module, and the gear decision module realizes the gear switching of the mechanical path and the electric path in each mode according to the optimized economical shifting rule.
2. The method of claim 1, wherein the vehicle demand torque module is related to operating modes and gear by virtue of the presence of multiple-gear electromechanical compound drive system configuration hybrid gear, mechanical path and electrical path gear ratios, while engine and motor output torques are coupled within the transmission, requiring a resolution of the demand torque to the final drive front end and conversion to a function of vehicle speed and pedal opening.
3. The method according to claim 1, wherein the mode discrimination module is configured to determine the input vehicle demand torque T r Battery power SOC, vehicle speed v, mechanical path speed ratio i ge And electric speed ratio i gm The whole vehicle operation mode is divided into 5 modes: pure electric mode EV, hybrid-mode HEV, engine alone drive mode Eng, and Driving charging mode Chg; wherein, the driving mode judging module judges the torque T according to the whole vehicle demand r Judging that the vehicle enters a driving mode and a braking mode, and when the vehicle demands torque T r When the vehicle is greater than 0, the vehicle enters a driving mode; when the required torque Tr of the whole vehicle is smaller than or equal to 0, the vehicle enters a braking mode; meanwhile, the driving mode judging module is divided into a power consumption mode CD and a power maintenance mode CS according to the change process of the battery power SOC; the power consumption mode CD is divided into a CD-EV mode and a CD-HEV mode, and the power consumption mode CS is divided into a CS-EV mode, a CS-HEV mode, a CS-Eng mode and a CS-Chg mode.
4. The method of claim 1, wherein the torque distribution module considers a mechanical path speed ratio i due to the presence of a hybrid gear of the multi-speed electro-mechanical compound drive system ge And electric speed ratio i gm The coupling characteristics of the energy management and shift strategy are achieved through torque thresholds of the engine and the electric machine, an engine optimal fuel economy curve and a demand torque.
5. The method according to claim 1, wherein the system integrated efficiency calculation module calculates according to the power flow of the multi-gear electromechanical hybrid transmission system in EV mode, HEV mode, eng mode, chg mode, and the overall system integrated efficiency is defined as: the ratio of the output power to the input power of the system calculates the efficiency in different modes according to the flow directions of different power flows when the vehicle runs in different modes.
6. The method according to claim 1, wherein the economy shift law formulation module obtains the shift speed by traversing the gear, solving the intersection point of the system comprehensive efficiency of the adjacent gear in each mode, traversing the pedal opening, obtaining the shift speed under different pedal openings, formulating a pedal opening-upshift law curve under different modes, obtaining the downshift law with a downshift speed difference of 6km/h by adopting an equal delay downshift strategy, correcting the shift law curve according to the simulation result, and formulating an initial economy upshift law.
7. The method of claim 1, wherein correcting the initial economy shift schedule by DIRECT algorithm and outputting the optimized economy shift schedule to a gear decision module comprises the steps of:
(1) Determining the topological structure and the working mode of a multi-gear electromechanical compound transmission system, and establishing torque distribution of an engine and a motor in a vehicle driving mode;
(2) The method comprises the steps of determining a working mode judgment method of a hybrid electric vehicle of a mode judgment module according to an accelerator pedal and a vehicle speed signal, and transmitting a determined vehicle driving mode signal to a torque distribution module;
(3) Establishing a comprehensive efficiency model of the system under each working mode according to the working torque distributed by the engine and the motor;
(4) Traversing gear and pedal opening, solving the intersection point of the comprehensive efficiency curve of the system under the adjacent gear, and obtaining an initial gear shifting and upshift rule;
(5) Adopting an equal delay type downshift strategy, acquiring a downshift law at a downshift speed difference of 6km/h, and correcting a gear shift law curve according to a simulation result to acquire an initial economical upshift and downshift law;
(6) Aiming at economical gear shifting laws, gear shifting speeds of adjacent gears under different pedal opening degrees of different modes are respectively used as optimization variables, the optimal working efficiency of a system is used as a target, a lifting gear threshold value of an initial gear shifting rule is used as constraint conditions of all the optimization variables under different pedal opening degrees, and the established objective function comprises rotating speeds and torque limit values of different power sources such as an engine and a motor, a threshold value of the gear shifting speed under the initial economical gear shifting laws and working current and voltage limit values of a battery;
(7) And carrying out optimization solution in a feasible region by adopting a DIRECT method to obtain a speed interval in which gears work reasonably, and further updating an economical gear shifting rule.
8. The method of claim 1, wherein the gear shift decision module takes as input an engine speed ratio, a motor speed ratio, a mode, and a vehicle speed, converts the mechanical road speed ratio and the electric road speed ratio into gear in each mode, and then compares the current vehicle speed with an offline formulated gear shift vehicle speed, and gradually shifts up and down to realize gear shift decision.
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