An engine starting control method and system under static conditions

Abstract

This application discloses an engine starting control method and system under static conditions, relating to the field of hybrid electric vehicle technology. The method includes: calculating the engine resistance torque based on an engine starting kinematic model; constructing a state equation based on an engine starting dynamics model, using motor speed, engine speed, and driveshaft torque as state variables, motor torque as a control variable, engine resistance torque as a disturbance variable, and motor speed and engine speed as output variables; constructing a Luenberger-type system state observer; and performing speed curve trajectory tracking based on the Luenberger-type system state observer, a preset engine speed curve, and a preset motor speed curve to obtain the optimal control law, characterizing the optimal torque of the motor during the reverse drag starting process of the engine via the driveshaft. This application ensures rapid starting while reducing the peak torque of the driveshaft, effectively guaranteeing the reliability of the driveshaft.

Description

Technical Field

[0001] This application relates to the field of hybrid vehicle technology, and in particular to an engine start-up control method and system under stationary conditions. Background Technology

[0002] Hybrid vehicles primarily achieve energy conservation and emission reduction through features such as automatic engine start-stop, regenerative braking, electric motor assistance, optimized engine efficiency, and pure electric driving. Hybrid vehicles are generally equipped with two or more power sources, including a traditional internal combustion engine, an electric drive unit, and an energy storage device. Through proper matching, optimization, and coordinated control, optimal energy distribution is achieved. To improve transmission efficiency and reduce fuel consumption, the use of a torque converter is eliminated in a series-parallel hybrid system, allowing the engine and transmission system to be directly coupled. This improves transmission system efficiency while significantly reducing transmission system damping. Therefore, the powertrain system of hybrid vehicles is more prone to torque fluctuations. In a series-parallel hybrid system, when starting the engine under stationary conditions, one electric motor is in braking mode, while the other motor outputs driving torque to drag the engine to the designated speed for ignition. During this process, the drive shaft needs to simultaneously bear the driving torque from the electric motor and the resistance torque from the engine rotation, which can easily generate large torque fluctuations. Excessive torque peaks can even lead to drive shaft breakage. Summary of the Invention

[0003] The purpose of this application is to provide an engine starting control method and system under static conditions, which can effectively suppress torque fluctuations on the drive shaft, reduce torque peaks, and ensure the safety of the drive shaft during rapid engine starting.

[0004] To achieve the above objectives, this application provides the following solution:

[0005] Firstly, this application provides an engine starting control method under static conditions, including:

[0006] A simulation model of a hybrid power system for a vehicle under static conditions is constructed; the simulation model includes a motor, a drive shaft, and an engine.

[0007] Based on the aforementioned hybrid power system simulation model, an engine start-up kinematics model and an engine start-up dynamics model are constructed.

[0008] Based on the engine starting kinematics model, calculate the engine drag torque;

[0009] Based on the engine starting dynamics model, the motor speed, engine speed, and transmission shaft torque are used as state variables, the motor torque is used as a control variable, the engine resistance torque is used as a disturbance variable, and the motor speed and engine speed are also used as output variables to construct a state equation.

[0010] Based on the state equation, a Luenberger-type system state observer is constructed; the Luenberger-type system state observer is used to reconstruct the torque of the drive shaft based on the motor speed and the engine speed;

[0011] Based on the Luenberger-type system state observer, the preset engine speed curve, and the preset motor speed curve, the speed curve trajectory is tracked to obtain the optimal control law; the optimal control law characterizes the optimal torque of the motor during the process of reverse-dragging the engine through the drive shaft.

[0012] Secondly, this application provides an engine starting control system under static conditions, comprising:

[0013] The system simulation model construction module is used to construct a simulation model of a vehicle's hybrid power system under static conditions; the hybrid power system simulation model includes a motor, drive shaft, and engine;

[0014] The kinematic and dynamic model construction module is used to construct the engine start-up kinematic model and engine start-up dynamic model based on the hybrid power system simulation model.

[0015] An engine drag torque determination module is used to calculate the engine drag torque based on the engine starting kinematics model.

[0016] The state equation determination module is used to construct state equations based on the engine start-up dynamics model, taking motor speed, engine speed, and drive shaft torque as state variables, motor torque as control variables, engine resistance torque as disturbance variables, and motor speed and engine speed as output variables.

[0017] The observer determination module is used to construct a Luenberger-type system state observer based on the state equation; the Luenberger-type system state observer is used to reconstruct the transmission shaft torque based on the motor speed and the engine speed;

[0018] The optimal control law determination module is used to perform speed curve trajectory tracking based on the Luenberger-type system state observer, the preset engine speed curve, and the preset motor speed curve to obtain the optimal control law; the optimal control law characterizes the optimal torque of the motor during the process of reverse-dragging the engine through the drive shaft.

[0019] According to the specific embodiments provided in this application, the following technical effects are disclosed:

[0020] This application discloses an engine starting control method and system under static conditions. The method calculates the engine resistance torque based on an engine starting kinematic model. Based on the engine starting dynamics model, it constructs a state equation by using motor speed, engine speed, and driveshaft torque as state variables, motor torque as a control variable, engine resistance torque as a disturbance variable, and motor speed and engine speed as output variables. A Luenberger-type system state observer is then constructed based on this state equation. Using the Luenberger-type system state observer, a preset engine speed curve, and a preset motor speed curve, the speed curve trajectory is tracked to obtain the optimal control law. This optimal control law characterizes the optimal torque of the motor during the reverse-draft engine starting process via the driveshaft. This application can effectively suppress torque fluctuations on the driveshaft and reduce torque peak values ​​while rapidly starting the engine, ensuring the safe use of the driveshaft. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart illustrating the engine start-up control method under static conditions according to this application.

[0023] Figure 2 This is a simplified diagram of the crank-connecting rod mechanism of this application;

[0024] Figure 3 This is a force diagram of the crank-connecting rod mechanism in this application;

[0025] Figure 4 This is a schematic diagram of the engine starting dynamics model under static conditions in this application;

[0026] Figure 5 This is a schematic diagram of the G(s) frequency response curve of this application;

[0027] Figure 6This is a schematic diagram of the H(s) frequency response curve of this application;

[0028] Figure 7 This is a schematic diagram of the Z(s) frequency response curve of this application;

[0029] Figure 8 This is a diagram of the Luenberger state observer structure for this application;

[0030] Figure 9 This is a comparison chart of the simulation results of the Luenberger torque observer in this application;

[0031] Figure 10 This is the optimal control system block diagram for this application;

[0032] Figure 11 shows the simulation results of PID control in this application; wherein, Figure 11(a) is the time-torque diagram of the power element obtained by PID control simulation, Figure 11(b) is the time-speed diagram of the power element obtained by PID control simulation, and Figure 11(c) is the time-torque diagram of the transmission shaft obtained by PID control simulation.

[0033] Figure 12 shows the simulation results of LQT control in this application; wherein, Figure 12(a) is the time-torque diagram of the power element obtained by LQT control simulation, Figure 12(b) is the time-speed diagram of the power element obtained by LQT control simulation, and Figure 12(c) is the time-torque diagram of the transmission shaft obtained by LQT control simulation. Detailed Implementation

[0034] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] This application provides an engine start-up control method and system under static conditions. For the engine start-up process of hybrid vehicles, in order to suppress torque fluctuations on the driveshaft and reduce peak torque, a dynamic model of the hybrid system is established, and a quadratic optimal control algorithm is applied to control the engine to track the target optimal speed curve, calculating the motor torque trajectory with optimal performance indicators. Simulation results show that the designed quadratic optimal speed tracking control strategy can effectively suppress torque fluctuations on the driveshaft and reduce peak torque while rapidly starting the engine, ensuring the safe operation of the driveshaft.

[0036] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] In one exemplary embodiment, such as Figure 1 As shown, this application provides an engine starting control method under static conditions, including:

[0038] Step 100: Construct a simulation model of the hybrid power system of the vehicle under static conditions; the simulation model includes an electric motor, a drive shaft, and an engine. The engine is a crankshaft and connecting rod structure, including a cylinder, piston, crankshaft, crankcase, and connecting rod.

[0039] Specifically, during the process of an electric motor driving an engine, certain resistance torques must be overcome, mainly including cylinder compression resistance torque, piston friction resistance torque, valve mechanism friction resistance torque, piston reciprocating motion inertial torque, and accessory running resistance torque. This application uses a research method combining theory and experiment to analyze the resistance torques in the engine process.

[0040] Step 200: Based on the hybrid power system simulation model, construct the engine starting kinematics model and the engine starting dynamics model.

[0041] (I) The construction of the engine starting kinematic model is described in the following steps:

[0042] To facilitate the kinematic analysis of the crank-connecting rod mechanism, a simplified diagram of the crank-connecting rod mechanism is established, such as... Figure 2 As shown in the diagram. Where O represents the center of the crankshaft; OB represents the crankshaft; A represents the piston pin center; B represents the crank pin center; AB represents the connecting rod; A1 and A2 represent the top dead center and bottom dead center of the piston, respectively; α represents the rotation angle of the crankshaft; and β represents the swing angle of the connecting rod relative to the cylinder centerline. Here, the first cylinder of the engine is used as an example. The kinematic parameters of the crank-connecting rod mechanism are shown in Table 1.

[0043] Table 1. Kinematic parameters of the crank-connecting rod mechanism

[0044] parameter numerical values Crank radius R (mm) 72.62 Linkage length L (mm) 262 Linkage ratio λ 0.277

[0045] Assuming the crank rotates clockwise, the piston displacement when the crank has rotated through an angle α is:

[0046]

[0047] because:

[0048]

[0049] so:

[0050] sinβ=λsinα(3)

[0051]

[0052] Substituting equation (4) into equation (1), we get:

[0053]

[0054] Expanding equation (4) using Taylor's formula, we get:

[0055]

[0056] Substituting equation (6) into equation (1) and simplifying using trigonometric relationships, we get:

[0057] x=R(a0+a1cosα+a2cos2α+a4cos4α+a6cos6α+……) (7)

[0058] The coefficients are represented as follows:

[0059]

[0060] a1 = -1

[0061]

[0062]

[0063]

[0064] Considering that λ is a small value less than 1, the cube and higher values ​​of λ in equation (7) are very small and can be ignored. Therefore, equation (7) can be approximated as a composite component that retains only the two main harmonic components of the displacement, as shown below:

[0065]

[0066] Differentiating equation (8) yields an approximate solution for the piston velocity:

[0067]

[0068] Similarly, by differentiating equation (9), an approximate solution for the piston acceleration can be obtained:

[0069]

[0070] The forces acting on a crank-connecting rod mechanism mainly include gas forces and inertial forces, such as... Figure 3 As shown, the force on the piston is decomposed into several components for calculation.

[0071] The forces acting on a crank-connecting rod mechanism have the following transmission relationships:

[0072]

[0073] The torque of a single cylinder can be obtained as follows:

[0074]

[0075] And because:

[0076] F = F j +F g (14)

[0077] Furthermore, combining equation (10), the reciprocating inertial force can be obtained as:

[0078] F j =-m j a = -m j Rω 2 (cosα+λcos2α)(15)

[0079] Based on the above formula, the resistance torque M of the first cylinder of the engine can be obtained. L1 The calculation formula is:

[0080]

[0081] Because, by simply obtaining the gas pressure, the cylinder output torque can be calculated. This application uses actual measurements of the engine indicator diagram P. g -α curve, converted to F g .

[0082] F g =(p-p0)S p (17)

[0083] In the formula, p is the air pressure inside the cylinder; p0 is the air pressure inside the crankcase; S p This represents the effective area of ​​the piston top.

[0084] The sum of the cylinder compression resistance torque and the piston reciprocating motion inertial torque is calculated by equations (16) and (17), which is the resistance torque of a single cylinder during engine startup. Then, the resistance torque of the other cylinders is obtained by equation (18). Finally, the total engine resistance torque during startup can be calculated.

[0085]

[0086] Among them, M Li ω represents the resistance torque of the i-th cylinder of the engine, ω represents the engine crankshaft speed, and F g The cylinder compression resistance, m jThe mass of the crank-connecting rod mechanism is represented by R, the radius of the crank is represented by α. i β represents the rotation angle of the crankshaft in the first cylinder of the engine. i This represents the angle of the connecting rod in the first cylinder of the engine relative to the cylinder centerline, i = 1,...,6, T e This indicates the engine drag torque.

[0087] (II) The construction of the engine start-up dynamics model is described in the following steps:

[0088] Considering the elasticity and damping of the flexible coupling, and treating the remaining components as completely rigid, undamped rotating inertial elements, expressed in terms of lumped mass, a dynamic model of the series-parallel hybrid power system can be obtained. For example... Figure 4 As shown, J E J A J B These are the equivalent moments of inertia of the engine, motor A, and motor B, respectively; J 01 J 02 J 11 J 12 These are the equivalent moments of inertia of the clutch CL0 driving plate, clutch CL0 driven plate, clutch CL1 driving plate, and clutch CL1 driven plate, respectively; J f1 J f2 These are the equivalent moments of inertia of the two gears in the front drive; J s1 J s2 J s3 These are the equivalent rotational inertia of the sun gears in the three planetary gear mechanisms; J r1 J r2 J r3 These are the equivalent rotational inertia of the gear rings of the three planetary gear mechanisms; J c1 J c2 J c3 These are the equivalent rotational inertia of the planet carriers of the three planetary gear mechanisms.

[0089] When the vehicle starts from a standstill, clutch CL0 engages, clutch CL1 disengages, brake BK engages, motor B is in braking mode, and motor A reverse-drives the engine to start. According to the rotational speed relationship of the planetary gear mechanism, we can obtain:

[0090]

[0091] In the formula, k1 and k2 are the characteristic parameters of planetary gear mechanisms PG1 and PG2 (the ratio of the number of teeth on the ring gear to the number of teeth on the sun gear); n r1 n c1 These represent the rotational speeds of the PG1 ring gear and the planet carrier of the planetary gear mechanism, respectively; n c2 This refers to the rotational speed of the planetary carrier PG2 in the planetary gear mechanism.

[0092] make:

[0093]

[0094] but:

[0095] n c2 =s1n A n c1 =s2n A n f1 =i q s1n A (twenty one)

[0096] For ease of calculation and to avoid analyzing the forces inside the planetary gear set, this application uses the Lagrange equations to establish the dynamic equations for the engine start-up process.

[0097] The system kinetic energy includes the rotational kinetic energy of the engine, motor, external meshing gear of the front drive, and the gear ring and planetary carrier of the planetary gear set. Meanwhile, for the convenience of subsequent analysis, the kinetic energy of the front drive and planetary gear set is equivalent to the output shaft of the motor, as shown in Equation (22).

[0098]

[0099] The system potential energy is manifested as the elastic potential energy of the elastic element on the transmission shaft, and the calculation formula is shown in equation (23).

[0100]

[0101] The system dissipates energy in the damping element on the transmission shaft, and the calculation formula is shown in equation (24).

[0102]

[0103] The driving torque of motor A and the resistance torque of the engine are selected as generalized forces, as shown in equation (25).

[0104] Q1 = T A Q2 = -T E (25)

[0105] Substituting the system's kinetic energy, potential energy, and dissipated energy into the generalized Lagrange equation, as shown in equation (26), we can obtain the dynamic equation for the engine start-up process of the hybrid power system under static conditions, as shown in equation (27).

[0106]

[0107] Among them, J A This represents the equivalent moment of inertia of motor A. T represents the angular acceleration of motor A.A i represents the driving torque of motor A. q This indicates the front gear ratio, s1 represents the proportional coefficient, and T... S J represents the torque of the drive shaft. E This represents the engine's equivalent moment of inertia. T represents the engine's angular acceleration. E The torque represents the engine drag torque, k represents the stiffness of the drive shaft, and θ represents the torque of the engine drag torque. A θ represents the motor rotation angle. E 'c' represents the engine rotation angle, and 'c' represents the drive shaft damping. Indicates the speed of motor A. This indicates the engine speed.

[0108] Step 300: Calculate the engine resistance torque based on the engine starting kinematic model; the specific calculation formulas are shown in formulas (16), (17) and (18) above.

[0109] Step 400: Based on the engine start-up dynamics model, the motor speed, engine speed, and drive shaft torque are used as state variables, the motor torque as a control variable, the engine resistance torque as a disturbance variable, and the motor speed and engine speed as output variables to construct a state equation. That is:

[0110]

[0111] The state equation is:

[0112]

[0113]

[0114]

[0115] in, Let represent the derivative of the state variable, y represent the output variable, x represent the state variable, u represent the control variable, and d represent the disturbance variable. [] T Let represent the transpose of the matrix, and k represent the stiffness of the drive shaft.

[0116] During engine startup under static conditions, torque fluctuations in the drive shaft directly manifest as fluctuations in vehicle acceleration, leading to vehicle vibration and reduced ride comfort. Based on the state-space expression, i.e., state equation (29), the transfer function between the motor A torque and the drive shaft torque can be derived. Substituting the actual parameters yields the following equation:

[0117]

[0118] Take k SPlot the frequency response curves of G(s) for different values ​​as follows: Figure 5 As shown, where k S1 <k S2 <k S3 <k S4 .analyze Figure 5 It can be seen that in the low frequency range, the frequency response curves under different stiffnesses coincide, and the amplitude and phase are constant values; near the resonant frequency, the amplitude-frequency characteristic and phase-frequency characteristic curves fluctuate violently, and the greater the stiffness, the more violent the fluctuation; in the high frequency range after the resonant frequency, the frequency response curves under different stiffnesses tend to coincide again.

[0119] The system characteristics will be further analyzed below. According to the system state equation (29), after substituting the actual parameters, the transfer function between the torque of motor A and the engine speed can be obtained as follows:

[0120]

[0121] Plot the frequency response characteristic curves of H(s) under different stiffnesses, such as... Figure 6 As shown, under different stiffnesses, the amplitude-frequency and phase-frequency characteristic curves of the system coincide in the low-frequency range, fluctuate near the resonant frequency, and the greater the stiffness, the more violent the fluctuation. In the high-frequency stage after passing the resonant frequency, they tend to coincide again. According to the above analysis, during the engine start-up process, the reverse-drafting of the engine by motor A causes a sudden change in the transmission shaft torque, and the system's frequency band is so wide that it covers the resonant frequency, thereby causing resonance in the transmission system and ultimately leading to fluctuations in engine speed.

[0122] According to the system state equation (29), after substituting the actual parameters, the transfer function between the torque and speed of motor A can be obtained as follows:

[0123]

[0124] Plot the frequency response characteristic curves of Z(s) under different stiffnesses, such as... Figure 7 As shown, the troughs and peaks of the amplitude-frequency response curve correspond to the anti-resonance frequency and resonant frequency of the system, respectively. In the low-frequency range, the amplitude-frequency response curves and phase-frequency response curves coincide for different stiffnesses. Near the anti-resonance and resonant frequencies of the system, both the amplitude-frequency response and phase-frequency response curves fluctuate, and the greater the stiffness, the more severe the fluctuations. Analysis of the system's frequency response characteristics reveals that when the transmission shaft torque changes abruptly, i.e., when the system frequency band covers the anti-resonance frequency and resonant frequency, it will cause fluctuations in the speed of motor A.

[0125] Step 500: Based on the state equation, construct a Luenberger-type system state observer; the Luenberger-type system state observer is used to reconstruct the torque of the transmission shaft based on the motor speed and the engine speed.

[0126] In engineering practice, torque measurement devices are not widely used in vehicles due to factors such as high cost and limited usage conditions. In order to obtain the torque value on the drive shaft and facilitate the analysis and evaluation of the effect of the control strategy, this application establishes a Luenberger-type system state observer to observe the torque on the drive shaft. The Luenberger observer adopts the feedback principle to gradually make the estimated state value approach the actual state value. The state-space expression of the engine starting process under static conditions is shown in equation (29), and the observability matrix of the system is:

[0127] N = [CCACA] 2 ] T (33)

[0128] Based on the observability matrix above, it is easy to see that the rank of the observability matrix is ​​rank(N) = 3, the system is completely observable, and it satisfies the existence condition of the Luenberger observer, so the system state observer can be designed.

[0129] Based on the state equation (29) of the engine start-up process under static conditions, the system state is reconstructed using a Luenberger observer. Since the speed data of motor A and engine can be directly obtained through sensor measurement, only a one-dimensional reduced-dimensional observer needs to be designed to reconstruct the torque on the drive shaft.

[0130] First, decompose the state variables into two parts based on detectability. Among them, the motor A speed and the engine speed are two state variables that can be directly measured, therefore let:

[0131]

[0132] The torque on the drive shaft needs to be observed, therefore:

[0133] x2=[T S (35)

[0134] The torques of motor A and the engine are selected as the system inputs, i.e.:

[0135] u = [T A T E ] T (36)

[0136] The state-space expression of the system will have the following form:

[0137]

[0138] A 21 =[ki q s1-k],

[0139]

[0140] Based on the above division, the original system is divided into two subsystems.

[0141] The state-space expression of the first subsystem is:

[0142]

[0143] The state-space expression of the second subsystem is:

[0144]

[0145] make:

[0146] z = A 12 x2(40)

[0147] but:

[0148]

[0149] M and z are the input and output quantities of the subsystem to be observed, respectively.

[0150] In summary, the observer equation can be obtained as follows:

[0151]

[0152] The equation appeared This increased the difficulty of implementation, in order to eliminate Introducing variables:

[0153]

[0154] Therefore, the observer equation becomes:

[0155]

[0156] in, Indicates intermediate variables. G represents the observed torque on the drive shaft, and G represents the configuration matrix.

[0157] Since the speed of motor A and the speed of the engine are directly measurable, there is no estimation error for these two state components. To verify that the estimation error of the torque on the drive shaft has the desired decay rate, equation (42) can be subtracted from equation (39) to obtain the state estimation error equation.

[0158]

[0159] After elimination and simplification, we can obtain:

[0160]

[0161] Since the system is observable, it is certain that by choosing G, (A) can be made to... 22 -GA 12 The poles of the torque on the drive shaft can be arbitrarily configured, thus ensuring that the error decays to zero as quickly as the designer expects. This completes the design of the Luenberger state observer for the torque on the drive shaft. The structure of the entire observer is as follows: Figure 8 As shown.

[0162] The designed Luenberger observer was simulated and verified based on a hybrid power system simulation model. The observation results of the torque on the drive shaft are as follows: Figure 9 As shown, compared with the simulated measured value, the observed torque of the drive shaft has an initial observation error, and the observed value can change with the measurement value during the rest of the time; the peak value of the torque on the drive shaft measured during the simulation is 1731 Nm, and the peak value observed is 1798 Nm, with only a 3.9% deviation between the two.

[0163] Step 600: Based on the Luenberger-type system state observer, the preset engine speed curve, and the preset motor speed curve, perform speed curve trajectory tracking to obtain the optimal control law; the optimal control law characterizes the optimal torque of the motor during the reverse-drive engine start-up process via the drive shaft.

[0164] During the reverse-drive engine start-up process of motor A, the torque fluctuation on the transmission shaft corresponds to the speed fluctuation of the engine and motor A. As shown in equation (27), if the speed of the engine and motor A remains linear (angular acceleration is constant), the torque on the transmission shaft will change uniformly, thus suppressing the torque fluctuation on the shaft. Therefore, by setting the speed trajectory of the engine and motor A and applying control for trajectory tracking, the control problem of suppressing torque fluctuation on the transmission shaft during engine start-up is transformed into a speed tracking control problem. The tracker problem is a type of quadratic optimal control problem, the control objective of which is to make the output closely follow a desired output without consuming excessive control energy.

[0165] Step 600 specifically includes:

[0166] 1) Based on the state equation, determine the system controllability matrix; according to the state-space expression (29) of the engine start-up process under static conditions, the system controllability matrix is:

[0167] M = [BABA] 2 B](47)

[0168] It is easy to see that the rank of the controllability matrix is ​​rank(M) = 3, and the system is completely controllable.

[0169] 2) Based on the system control matrix, the Luenberger-type system state observer, the preset engine speed curve, and the preset motor speed curve, determine the performance functional; set the tracking trajectories of engine and motor A as follows:

[0170]

[0171] In the formula, α A Let α be the angular acceleration of the motor at point A; E The angular acceleration is the engine's angular acceleration. In the tracking trajectory, the angular acceleration of the engine and motor A is set to a constant value, meaning that the rotational speeds of the engine and motor A change according to a linear law.

[0172] Based on the above system controllability matrix, the set tracking trajectory, and the data observed by the Luenberger-type system state observer, the error vector is defined as:

[0173] e(t)=z(t)-y(t))(49)

[0174] Find the optimal control that minimizes the following performance functional:

[0175]

[0176] The letters in equation (50) are explained as follows:

[0177]

[0178] Where J represents the performance index value, [t0,t f ] represents the time series, e represents the error vector, and q represents the time series. 11 and q 12 q1 and q2 respectively represent the degree of importance attached to the speed tracking error of motor A and engine; q3 represents the degree of importance attached to the control cost of motor A; q4 represents the degree of importance attached to the control cost of motor A. 01 and q 02 These represent the degree of importance attached to the tracking error at the final moment of motor A and engine speed, respectively.

[0179] 3) Determine the Hamiltonian function based on the state equation and the performance functional; specifically, the Hamiltonian function can be written according to the minimum principle:

[0180]

[0181] The following equations are derived from the extremum conditions:

[0182]

[0183]

[0184] The canonical equation of the system is:

[0185]

[0186] make:

[0187] λ(t)=P(t)x(t)-g(t) (56)

[0188] Substituting equation (56) into equation (53), we get:

[0189]

[0190] Taking the derivative of both sides of equation (56), we get:

[0191]

[0192] By combining equations (54), (56), and (57), we can obtain:

[0193]

[0194] By combining equations (55) and (56), we can obtain:

[0195]

[0196] If an optimal solution exists, then equations (59) and (60) hold for all x(t) and z(t), leading to the following conclusion:

[0197] (1) The following matrix differential equations must be satisfied:

[0198]

[0199] (2) The following vector differential equations must be satisfied:

[0200]

[0201] Their boundary conditions are:

[0202]

[0203] 4) Solve the Hamiltonian function to obtain the optimal control law. Solve P(t) and g(t) from equations (61) and (62), and substitute them into equation (57) to obtain the optimal control law u*(t), which is the optimal torque output of motor A during the reverse-draft start-up process of the engine. From equations (61) and (63), it can be seen that the solution of P(t) is independent of the selection of z(t), so it can be obtained in the time series [t0,t... f The solution P(t) is obtained directly from the above. This application uses the fourth-order Runge-Kutta method to solve P(t) in reverse order, and the solution expression is as follows:

[0204]

[0205] Where h is the selected simulation step size, the initial conditions required for the solution are obtained from equation (63), and the initial conditions are related to the value of the weight matrix Q0.

[0206] Similarly, based on the selected z(t) and the obtained P(t), the fourth-order Runge-Kutta method is used to calculate the time series [t0, t... f Solve g(t) in reverse order, and the solution expression is:

[0207]

[0208] The initial conditions are determined according to equation (63), and are related to the weight matrix Q0 and z(t). f The values ​​of ) are all related.

[0209] In summary, this addresses the problem of the designed tracker, with the system structure as follows: Figure 10 As shown.

[0210] Finally, based on the simulation model of the hybrid power system, the optimal control law derived above is applied to verify the effect of engine start-up optimal control (LQT). At the same time, proportional-integral-derivative control (PID) is used as a control to compare the proposed control strategy.

[0211] Figure 11 shows the simulation results using PID control. As shown in Figure 11(a), after receiving the engine start command, motor A outputs driving torque to drag the engine to ignition speed. Due to the sudden increase in motor A torque and the combined effect of the engine's resistance torque, the torque on the drive shaft changes abruptly. As shown in Figure 11(c), the peak torque reaches 1731 Nm, affecting the safety of the drive shaft and potentially causing it to break in severe cases. As shown in Figure 11(b), the engine speed gradually increases under the action of motor A torque, reaching 800 r / min for the first time at 0.40 s. After that, the engine maintains idle speed, and motor A stops outputting driving torque, instead operating under the engine's drive.

[0212] Figure 12 shows the simulation results using LQT control. For the engine start-up process under stationary vehicle conditions, the boundary conditions are the same when solving the LQT controller, i.e., both the engine and motor are stationary. Considering the complexity of real-time calculation in actual vehicle applications, this application chooses to perform offline calculations on the controller, saving the calculated optimal control law for interpolation calculations in actual vehicle applications. Unlike PID control, where the motor A torque suddenly rises to its maximum torque and then remains constant, under LQT control, the torque of motor A changes dynamically to ensure a uniform increase in the speed of both the engine and motor A, thereby reducing torque fluctuations on the drive shaft. The peak torque during the start-up process is 1463 Nm, a 15.5% reduction compared to PID control. The entire start-up process lasts 0.34 s, a 15.0% reduction compared to PID control.

[0213] Table 2 shows the detailed data comparing the simulation results of PID and LQT control. It can be seen that, compared with PID control, LQT control can reduce the peak torque of the drive shaft while ensuring rapid start-up, thus effectively ensuring the reliability of the drive shaft and thus having a better control effect.

[0214] Table 2 Comparison of Simulation Results Using PID and LQT Control

[0215] parameter PID LQT reduce Peak torque of the drive shaft (Nm) 1731 1463 15.5％ Startup time (s) 0.40 0.34 15.0％

[0216] Based on the same inventive concept, this application also provides an engine starting control system under static conditions. The solution provided by this system is similar to the solution described in the above method. Therefore, the specific limitations of one or more system embodiments provided below can be found in the limitations of the method above, and will not be repeated here. The engine starting control system under static conditions of this application includes:

[0217] The system simulation model construction module is used to construct a simulation model of a vehicle's hybrid power system under static conditions; the hybrid power system simulation model includes a motor, drive shaft, and engine.

[0218] The kinematic and dynamic model construction module is used to construct the engine start-up kinematic model and engine start-up dynamic model based on the hybrid power system simulation model.

[0219] The engine drag torque determination module is used to calculate the engine drag torque based on the engine starting kinematics model.

[0220] The state equation determination module is used to construct a state equation based on the engine starting dynamics model, taking the motor speed, engine speed, and drive shaft torque as state variables, the motor torque as a control variable, the engine resistance torque as a disturbance variable, and the motor speed and engine speed as output variables.

[0221] The observer determination module is used to construct a Luenberger-type system state observer based on the state equation; the Luenberger-type system state observer is used to reconstruct the torque of the transmission shaft based on the motor speed and the engine speed.

[0222] The optimal control law determination module is used to perform speed curve trajectory tracking based on the Luenberger-type system state observer, the preset engine speed curve, and the preset motor speed curve to obtain the optimal control law; the optimal control law characterizes the optimal torque of the motor during the process of reverse-dragging the engine through the drive shaft.

[0223] In one exemplary embodiment, this application provides an electronic device including a memory and a processor. The memory stores a computer program, and the processor runs the computer program to enable the electronic device to perform an engine starting control method under static conditions. Optionally, the electronic device may be a server.

[0224] In one exemplary embodiment, this application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements an engine start-up control method under static conditions.

[0225] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0226] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for controlling engine starting under static conditions, characterized in that, The methods include: A simulation model of a hybrid power system for a vehicle under static conditions is constructed; the simulation model includes a motor, a drive shaft, and an engine. Based on the aforementioned hybrid power system simulation model, an engine start-up kinematics model and an engine start-up dynamics model are constructed. Based on the engine starting kinematics model, calculate the engine drag torque; Based on the engine starting dynamics model, the motor speed, engine speed, and transmission shaft torque are used as state variables, the motor torque is used as a control variable, the engine resistance torque is used as a disturbance variable, and the motor speed and engine speed are also used as output variables to construct a state equation. Based on the state equation, a Luenberger-type system state observer is constructed; the Luenberger-type system state observer is used to reconstruct the torque of the drive shaft based on the motor speed and the engine speed; Based on the Luenberger-type system state observer, the preset engine speed curve, and the preset motor speed curve, the speed curve trajectory is tracked to obtain the optimal control law; the optimal control law characterizes the optimal torque of the motor during the process of reverse-dragging the engine through the drive shaft.

2. The engine starting control method under static conditions according to claim 1, characterized in that, The engine is a crankshaft and connecting rod structure, including a cylinder, piston, crankshaft, crankcase and connecting rod; The formula for calculating the engine drag torque is as follows: The drag torque M of the first cylinder of the engine L1 The calculation formula is: F g =(p-p0)S p ; The resistance torque M of the i-th cylinder of the engine Li The calculation formula is: The formula for calculating engine drag torque is: Where α represents the rotation angle of the crankshaft of the first cylinder of the engine, α i ω represents the rotation angle of the crankshaft of the first cylinder of the engine; ω represents the engine crankshaft speed, F g The cylinder compression resistance, m j The crankshaft and connecting rod mechanism has mass R, crank radius R, and β, the angle of the connecting rod in the first cylinder of the engine relative to the cylinder centerline. i The connecting rod in the first cylinder of the engine is represented by its angle relative to the cylinder centerline, i = 1,...,6; λ represents the connecting rod ratio; p represents the cylinder pressure; p0 represents the crankcase pressure; S p T represents the effective area of ​​the piston crown. e L represents the engine drag torque, and L represents the connecting rod length.

3. The engine starting control method under static conditions according to claim 1, characterized in that, The engine start-up dynamics model is as follows: Among them, J A This represents the equivalent moment of inertia of motor A. T represents the angular acceleration of motor A. A i represents the driving torque of motor A. q This indicates the front gear ratio, s1 represents the proportional coefficient, and T... S J represents the torque of the drive shaft. E This represents the engine's equivalent moment of inertia. T represents the engine's angular acceleration. E The torque represents the engine drag torque, k represents the stiffness of the drive shaft, and θ represents the torque of the engine drag torque. A θ represents the motor rotation angle. E 'c' represents the engine rotation angle, and 'c' represents the drive shaft damping. Indicates the speed of motor A. This indicates the engine speed.

4. The engine starting control method under static conditions according to claim 3, characterized in that, The state equation is: u=T A ,d=T E , in, Let represent the derivative of the state variable, y represent the output variable, x represent the state variable, u represent the control variable, and d represent the disturbance variable. [] T Let represent the transpose of the matrix, and k represent the stiffness of the drive shaft.

5. The engine starting control method under static conditions according to claim 4, characterized in that, The Luenberger-type system state observer is: THE 21 =[out q s1-k], in, Indicates intermediate variables. G represents the observed torque on the drive shaft, and G represents the configuration matrix.

6. The engine starting control method under static conditions according to claim 4, characterized in that, Based on the Luenberger-type system state observer, the preset engine speed curve, and the preset motor speed curve, speed trajectory tracking is performed to obtain the optimal control law, specifically including: Based on the aforementioned state equations, the system controllability matrix is ​​determined; Based on the system energy control matrix, the Luenberger-type system state observer, the preset engine speed curve, and the preset motor speed curve, the performance functional is determined. The Hamiltonian function is determined based on the state equation and the performance functional. Solve the Hamiltonian function to obtain the optimal control law.

7. The engine starting control method under static conditions according to claim 6, characterized in that, The performance functional is: Q2=q2, Where J represents the performance index value, [t0,t f ] represents the time series, e represents the error vector, and q represents the time series. 11 and q 12 q1 and q2 respectively represent the degree of importance attached to the speed tracking error of motor A and engine; q3 represents the degree of importance attached to the control cost of motor A; q4 represents the degree of importance attached to the control cost of motor A. 01 and q 02 These represent the degree of importance attached to the tracking error at the final moment of motor A and engine speed, respectively.

8. The engine starting control method under static conditions according to claim 7, characterized in that, The formula for calculating the optimal control law is: The solutions for P(t) and g(t) satisfy the following equations: The matrix differential equation is: The vector differential equation is: The boundary conditions are: Among them, u * (t) represents the optimal control law.

9. An engine starting control system under static conditions, characterized in that, The system includes: The system simulation model construction module is used to construct a simulation model of a vehicle's hybrid power system under static conditions; the hybrid power system simulation model includes a motor, drive shaft, and engine; The kinematic and dynamic model construction module is used to construct the engine start-up kinematic model and engine start-up dynamic model based on the hybrid power system simulation model. An engine drag torque determination module is used to calculate the engine drag torque based on the engine starting kinematics model. The state equation determination module is used to construct state equations based on the engine start-up dynamics model, taking motor speed, engine speed, and drive shaft torque as state variables, motor torque as control variables, engine resistance torque as disturbance variables, and motor speed and engine speed as output variables. The observer determination module is used to construct a Luenberger-type system state observer based on the state equation; the Luenberger-type system state observer is used to reconstruct the transmission shaft torque based on the motor speed and the engine speed; The optimal control law determination module is used to perform speed curve trajectory tracking based on the Luenberger-type system state observer, the preset engine speed curve, and the preset motor speed curve to obtain the optimal control law; the optimal control law characterizes the optimal torque of the motor during the process of reverse-dragging the engine through the drive shaft.

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