Target calculation method and system for engine torque under series working condition of hybrid electric vehicle
By adopting the torque target calculation method in hybrid vehicle engines, combined with the economic line fixed-point control and optimization algorithm control strategy, the problems of inaccurate torque control and high experimental cost of engines in series operation conditions in the existing technology are solved, and the problem of inaccurate torque control and high experimental cost in the engine in series operation conditions is realized. High-precision torque control and ideal fuel consumption effect.
Patent Information
- Application Number
- CN202411653598.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-19
- Publication Date
- 2025-02-21
AI Technical Summary
The existing torque target control strategy of hybrid vehicle engines in series operating conditions has insufficient fixed-point strategy, which leads to inaccurate torque control at non-experimental measurement points, which increases experimental costs.
A method for calculating engine torque targets in the hybrid vehicle series operation condition is adopted. By obtaining the vehicle's drive mode and the actual engine speed, it is determined whether it is within the threshold range of the measured point. If it is there, an economic line fixed-point control strategy is adopted. If not, the optimization algorithm control strategy is adopted. The optimization algorithm solves the system's equivalent fuel consumption objective function and constraints to obtain the optimal engine torque target.
On the premise of ensuring fuel consumption effect, the dependence on experimental measurement is reduced, the torque control accuracy is improved, the experimental cost is reduced, and the ideal fuel consumption effect is achieved.
Smart Images
Figure CN119489807A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of hybrid vehicle engine control, and in particular to a method and system for calculating an engine torque target under a series working condition of a hybrid vehicle. Background Art
[0002] The energy sources of hybrid vehicles (including PHEV / REM extended-range vehicles) mainly include batteries and fuel. The power of fuel vehicles passes through the engine, and the gearbox amplifies the torque and transmits the power to the wheel end. The main function of the hybrid vehicle engine is to generate electricity and provide a small part of the torque to the wheel end under appropriate working conditions. The main torque is provided by the motor. In the current solution, in order to reduce the performance requirements of the drive motor, a hybrid-specific gearbox is used to transmit power to the wheel end.
[0003] In the series mode, the current engine target torque control strategy mainly includes fixed-point control and other strategies. The fixed-point power generation strategy has the following characteristics: the engine runs stably, which is beneficial to emissions and fuel consumption; the change of power generation is jumpy. Therefore, the fixed-point power generation strategy will have the following shortcomings:
[0004] 1. Due to the discrete distribution of the fixed-point strategy, if the engine speed is at a non-experimental determination point, the interpolation method is generally used to determine the power generation torque point. This method can only approximately make the engine torque point run along the fuel-saving path.
[0005] 2. If you need to obtain an ideal fuel consumption effect, you can reduce the speed range of the experimental test and improve the accuracy of the engine target torque setting, but this method will increase the experimental cost.
[0006] To this end, the present invention proposes a method for calculating the target engine torque under series operation of a hybrid vehicle. Summary of the invention
[0007] In view of the problems existing in the prior art, the present invention provides a method for calculating the target engine torque under series operation of a hybrid vehicle.
[0008] In order to achieve the above object, the present invention adopts the following technical solutions:
[0009] A method for calculating an engine torque target under a series operation condition of a hybrid vehicle, the method comprising:
[0010] Obtain the vehicle's driving mode and actual engine speed;
[0011] determining whether the driving mode is a series mode, and if so, determining whether the vehicle is within a measurement point threshold range according to the actual engine speed;
[0012] When the actual engine speed is within the threshold range of the determination point, the engine outputs the engine torque value of the target economy line fixed point control strategy;
[0013] When the actual engine speed is not within the threshold range of the determination point, the engine output torque target optimizes the engine torque value of the algorithm control strategy.
[0014] Furthermore, the torque target economic line fixed-point control strategy limits the engine operating speed and working torque by a calibration method according to the engine universal characteristic curve, so that the engine is in an economic working area.
[0015] Furthermore, the threshold of the measuring point is measured by experiment, and the engine fuel consumption fitting function f(T, n) can be obtained. The fitting accuracy is generally required to be above 95%, where T is the engine torque, n is the engine speed, and the error is calculated as follows:
[0016]
[0017] The threshold value is determined by actually calibrating the allowable error range.
[0018] Furthermore, the system equivalent fuel consumption objective function of the torque target optimization algorithm control strategy is:
[0019]
[0020] Constraints:
[0021]
[0022] System equivalent fuel consumption = (engine torque * engine speed) / fuel efficiency + (EM2 motor torque * EM2 motor speed) / EM2 motor efficiency * power equivalent factor, where the engine speed is estimated by the vehicle speed or input shaft speed. At a given time under a given working condition, this value is a constant;
[0023] Fuel efficiency is a function of engine speed and engine torque. When the speed is given, fuel efficiency is a univariate function of engine torque.
[0024] The EM2 motor efficiency is an inherent parameter of the EM2 and is a constant under given operating conditions and at given times;
[0025] The electric quantity equivalent factor is related to the electronic control system. Under given working conditions and at given time, the electric quantity equivalent factor is a constant.
[0026] is the wheel-end demand torque, which is determined by the accelerator pedal and SOC at a given moment and is a constant at a given moment.
[0027] i1 is the transmission ratio of engine torque converted to wheel end;
[0028] i2 is the transmission ratio of EM2 motor torque converted to wheel end;
[0029] Based on the above system equivalent fuel consumption objective function and constraints, the optimal engine torque target at the current moment is obtained.
[0030] Furthermore, the system equivalent fuel consumption objective function and constraint conditions are solved with variable step length using the golden section method.
[0031] Furthermore, the optimal engine torque target is processed by a Kalman filter model to obtain an accurate engine torque target.
[0032] Furthermore, the control strategy implementation steps are also included:
[0033] The optimized torque distribution result is sent to the engine controller and the motor controller via the CAN bus;
[0034] Each actuator performs output control according to the command torque.
[0035] Furthermore, an output cycle of the optimal engine torque distribution scheme matches a control cycle of the engine controller.
[0036] The above technical solution of the present invention has the following beneficial technical effects:
[0037] The present invention can solve the shortcomings of the fixed-point strategy and use an optimization algorithm to plan the target torque path of the non-test point, thereby reducing the dependence on experimental measurement as much as possible while ensuring the fuel consumption effect, and obtaining an ideal fuel consumption effect. BRIEF DESCRIPTION OF THE DRAWINGS
[0038] Figure 1 The present invention is a flow chart of a method for calculating the target engine torque of a hybrid vehicle under series operation. DETAILED DESCRIPTION
[0039] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.
[0040] like Figure 1 As shown, the present invention provides a method for calculating the target engine torque of a hybrid vehicle under series operation, the method comprising:
[0041] The vehicle driving mode and the actual engine speed are obtained; specifically, the present invention obtains the total required power according to the wheel end torque demand and the current vehicle speed calculation and the accessory power.
[0042]
[0043] Where P is the total power demand in kW, T is the current wheel end torque demand in Nm, v is the current vehicle speed in km / h, and r is the tire radius in m. accy P is the accessory power in kW. Battery It is the battery charge / discharge power limit, which is sent to the bus by the BMS controller;
[0044] Then, according to the engine universal characteristic table, determine the isopower line, find the optimal point of fuel consumption rate in the isopower line, and then obtain the engine speed and torque at this working point.
[0045] determining whether the driving mode is a series mode, and if so, determining whether the vehicle is within a measurement point threshold range according to the actual engine speed;
[0046] When the actual engine speed is within the threshold range of the determination point, the engine outputs the engine torque value of the target economy line fixed point control strategy;
[0047] When the actual engine speed is not within the threshold range of the determination point, the engine output torque target optimizes the engine torque value of the algorithm control strategy.
[0048] In a specific implementation of the present invention, the torque target economic line fixed-point control strategy limits the engine operating speed and working torque by a calibration method according to the engine universal characteristic curve, so that the engine is in an economic working area.
[0049] In a specific implementation of the present invention, the threshold of the measuring point is determined by experiment, and the engine fuel consumption fitting function f(T, n) can be obtained. The fitting accuracy is generally required to be above 95%, where T is the engine torque, n is the engine speed, and the error calculation is:
[0050]
[0051] The threshold value is determined by actually calibrating the allowable error range;
[0052] It is worth noting that the fitting function f(T,n) formula is obtained by fitting the test data. The general fitting method is polynomial fitting, and the expression can also be obtained by using methods such as neural networks.
[0053] Fitting accuracy is used to measure the degree of deviation between the estimated value obtained by fitting the surface and the actual test data points for a given fitting method. The concept of goodness of fit is used here. For more information about fitting accuracy, please refer to Baidu Encyclopedia Goodness of Fit. In engineering, the following formula can also be used to measure the accuracy of the fitting model, that is, the sum of the squares of the differences between all the estimated values obtained by fitting the model and the actual measured values:
[0054] ∑(y estimation -y actual ) 2 ;
[0055] Error represents the error of the fitting model at a certain point n, T, and is used to determine whether to use the optimization method to improve the torque control accuracy. The error and allowable range are obtained through experiments and are related to the actual vehicle system.
[0056] In a specific implementation of the present invention, the system equivalent fuel consumption objective function of the torque target optimization algorithm control strategy is:
[0057]
[0058] Constraints:
[0059]
[0060] System equivalent fuel consumption = (engine torque * engine speed) / fuel efficiency + (EM2 motor torque * EM2 motor speed) / EM2 motor efficiency * power equivalent factor, where the engine speed is estimated by the vehicle speed or input shaft speed. At a given time under a given working condition, this value is a constant;
[0061] Fuel efficiency is a function of engine speed and engine torque. When the speed is given, fuel efficiency is a univariate function of engine torque.
[0062] The EM2 motor efficiency is an inherent parameter of the EM2 and is a constant under given operating conditions and at given times;
[0063] The electric quantity equivalent factor is related to the electronic control system. Under given working conditions and at given time, the electric quantity equivalent factor is a constant.
[0064] is the wheel-end demand torque, which is determined by the accelerator pedal and SOC at a given moment and is a constant at a given moment.
[0065] i1 is the transmission ratio of engine torque converted to wheel end;
[0066] i2 is the transmission ratio of EM2 motor torque converted to wheel end;
[0067] Based on the above system equivalent fuel consumption objective function and constraints, the optimal engine torque target at the current moment is obtained.
[0068] In a specific implementation manner of the present invention, the system equivalent fuel consumption objective function and constraint conditions are solved with variable step length using the golden section method.
[0069] In a specific implementation manner of the present invention, the optimal engine torque target is processed by a Kalman filter model to obtain an accurate engine torque target.
[0070] In a specific implementation of the present invention, the control strategy implementation step is also included:
[0071] The optimized torque distribution result is sent to the engine controller and the motor controller via the CAN bus;
[0072] Each actuator performs output control according to the command torque.
[0073] In a specific implementation of the present invention, the output cycle of the optimal engine torque distribution scheme matches the control cycle of the engine controller.
[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A method for calculating the target engine torque of a hybrid vehicle in series operation, characterized in that: The method comprises: Obtain the vehicle's driving mode and actual engine speed; determining whether the driving mode is a series mode, and if so, determining whether the vehicle is within a measurement point threshold range according to the actual engine speed; When the actual engine speed is within the threshold range of the determination point, the engine outputs the engine torque value of the target economy line fixed point control strategy; When the actual engine speed is not within the threshold range of the determination point, the engine output torque target optimizes the engine torque value of the algorithm control strategy.
2. The method for calculating the target engine torque of a hybrid vehicle in series operation according to claim 1, characterized in that: The torque target economic line fixed-point control strategy limits the engine operating speed and working torque by calibration according to the engine universal characteristic curve, so that the engine is in the economic working area.
3. The method for calculating the target engine torque of a hybrid vehicle in series operation according to claim 1, characterized in that: The threshold of the measuring point is determined by experiment, and the engine fuel consumption fitting function f(T, n) can be obtained. The fitting accuracy is generally required to be above 95%, where T is the engine torque, n is the engine speed, and the error calculation is: The threshold value is determined by actually calibrating the allowable error range.
4. The method for calculating the target engine torque of a hybrid vehicle in series operation according to claim 1, characterized in that: The system equivalent fuel consumption objective function of the torque target optimization algorithm control strategy is: Constraints: Tq Demand =i1*Tq Eng +i2*Tq_EM2; System equivalent fuel consumption = (engine torque * engine speed) / fuel efficiency + (EM2 motor torque * EM2 motor speed) / EM2 motor efficiency * power equivalent factor, where the engine speed is estimated by the vehicle speed or input shaft speed. At a given time under a given working condition, the engine speed is a constant value; Fuel efficiency is a function of engine speed and engine torque. When the speed is given, fuel efficiency is a univariate function of engine torque. The EM2 motor efficiency is an inherent parameter of the EM2 and is a constant under given operating conditions and at given times; The electric quantity equivalent factor is related to the electronic control system. Under given working conditions and at given time, the electric quantity equivalent factor is a constant. Tq Demand is the wheel end required torque, which is determined by the accelerator pedal and SOC at a given moment and is a constant at a given moment; i1 is the transmission ratio of engine torque converted to wheel end; i2 is the transmission ratio of EM2 motor torque converted to wheel end; Based on the above system equivalent fuel consumption objective function and constraints, the optimal engine torque target at the current moment is obtained.
5. The method for calculating the target engine torque of a hybrid vehicle in series operation according to claim 4, characterized in that: The system equivalent fuel consumption objective function and constraint conditions are solved by variable step length using the golden section method.
6. The method for calculating the target engine torque of a hybrid vehicle in series operation according to claim 4, characterized in that: The optimal engine torque target is processed by a Kalman filter model to obtain an accurate engine torque target.
7. The method for calculating the target engine torque of a hybrid vehicle in series operation according to claim 1, characterized in that: It also includes the control strategy implementation steps: The optimized torque distribution result is sent to the engine controller and the motor controller via the CAN bus; Each actuator performs output control according to the command torque.
8. The method for calculating the target engine torque of a hybrid vehicle in series operation according to claim 1, characterized in that: The output cycle of the optimal engine torque distribution scheme matches the control cycle of the engine controller.