Torsional vibration active control method for starting and stopping process of engine of power split type hybrid power system

Abstract

The invention relates to a torsional vibration active control method in the starting and stopping process of an engine of a power split type hybrid power system, and aims to solve the problem of torsional vibration of a transmission system under the high coupling effect of multiple excitation sources of the system. Firstly, a transmission system multi-degree-of-freedom kinetic equation used for simulating the engine start-stop torsional vibration phenomenon is established; secondly, considering excitation input of the engine, and designing a self-adaptive filtering feedforward control algorithm to counteract fluctuation components of gas torque and inertia torque of the engine; finally, considering interference input in the start-stop process of the engine, designing a pole assignment feedback algorithm, and reducing a torsional amplitude value from a drive shaft of the transmission system to wheels; according to the method, the torsional vibration of the transmission system in the engine starting and stopping process is remarkably improved through fusion of the two control algorithms, and a new research reference is provided for torsional vibration control in the engine starting and stopping process.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile torsional vibration control, and in particular relates to a method for actively controlling torsional vibration during the start-stop process of an engine of a power-split hybrid power system. Background Art

[0002] The power-split hybrid system, with its multi-degree-of-freedom coupling characteristics, coincides with the needs of commercial vehicles with complex and changeable operating conditions. However, as the system has no clutch or torque converter to separate the engine from the transmission when the engine starts and stops, it is easy to cause system resonance when the engine speed exceeds the resonant speed. It is urgent to develop a control algorithm to reduce the vibration amplitude of the transmission system and improve the vehicle's driving smoothness.

[0003] Some existing patents, such as the invention patent with patent number CN117841961A, design a method for offsetting engine torque pulsation, obtain the pulsation function of the engine torque pulsation with the crank-connecting rod angle change under various working conditions, construct a torsional vibration offset function that offsets the torque with the crank-connecting rod angle change, and add control parameters to the torsional vibration offset function. The invention patent with patent number CN113428157B uses a permanent magnet synchronous motor to perform feedforward control on the torsional vibration of the hybrid powertrain system for adaptive active control, and can adaptively adjust the controller parameters as the torque of the parallel P2 configuration hybrid vehicle transmission system changes in real time, thereby using the controllability of the motor to quickly and accurately compensate for the torque fluctuation of the transmission system.

[0004] However, the system realizes power splitting through the planetary gear mechanism. The power transmission process is not transmitted along a single path, and has two control degrees of freedom. When performing active control, it is necessary to take into account the internal posture of the planetary gear mechanism and the power transmission from the ring gear to the vehicle. Secondly, the transmission system parameters, such as stiffness and damping values, are usually difficult to obtain accurately. The torsional vibration characteristics of the transmission system under different transmission system parameters, such as vibration amplitude and vibration frequency, are different, which poses a greater challenge to the design of the control algorithm. Therefore, how to develop an active vibration reduction control algorithm for the engine start-stop process with system power splitting characteristics to achieve the goal of reducing the torsional vibration of the transmission system and improving vehicle comfort is a difficulty that needs to be solved urgently. Summary of the invention

[0005] The present invention proposes a method for actively controlling torsional vibration during the start-stop process of an engine of a power-split hybrid system. In order to overcome the complex torsional vibration problem caused by the high coupling of three excitation sources during the start-stop process of the engine, the method takes into account the power-split characteristics of the system, designs an adaptive filtering feedforward control algorithm and a pole configuration feedback algorithm, and processes the torque fluctuations of the engine excitation source and the transmission system with clear division of labor, thereby achieving a better solution to the vehicle torsional vibration problem during the start-stop process of the engine.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A power split hybrid system, the hybrid system is composed of an engine, a torsional vibration damper, an MG1 motor, an MG2 motor, a planetary gear mechanism, a first wet clutch, a second wet clutch, a two-speed AMT gearbox, a main reducer, a half shaft and wheels, wherein the planetary gear mechanism includes a ring gear, a planet carrier and a sun gear. The engine is connected to the planet carrier of the planetary gear mechanism through the torsional vibration damper, and the power is split into an electrical path and a mechanical path, and finally converged at the main reducer. In the electrical path, the engine, the MG1 motor, the first wet clutch and the second wet clutch act together on the planetary gear mechanism to change the motion state of the planetary gear mechanism; in the mechanical path, the engine outputs torque through the ring gear of the planetary gear mechanism, and the torque output by the MG2 motor through the two-speed AMT gearbox is coupled at the main reducer and the half shaft, and the wheels are driven together.

[0008] A method for actively controlling torsional vibration during the start-stop process of an engine in a power-split hybrid system, the method comprising the following steps:

[0009] S1: Establish the multi-degree-of-freedom dynamic equations of the transmission system for simulating the engine start-stop torsional vibration phenomenon;

[0010] S2: Based on the multi-degree-of-freedom dynamic equations in S1, the dynamic response of the engine start-stop process of the planetary multi-speed hybrid system is obtained, and the external excitation and system damping are ignored to obtain the theoretical equation of the inherent characteristics of the system;

[0011] S3: Considering the excitation input of the engine, LMS adaptive filter control is applied to the field of torsional vibration control. An adaptive filter feedforward control algorithm is designed to offset the fluctuation components of the engine gas torque and inertia torque. The torque compensation amount is calculated and distributed to the MG1 motor and the MG2 motor to control the torsional vibration at the engine end.

[0012] S4: Considering the disturbance input of the engine start-stop process, a pole configuration feedback algorithm is designed to calculate the motor torque compensation, and the torsional amplitude is reduced from the drive shaft of the transmission system to the wheels, making the engine start process of the power-split hybrid system smoother.

[0013] Furthermore, the multi-degree-of-freedom dynamics equation in step S1 is shown in formula (1):

[0014]

[0015] In the formula, I 1 ,I 2 ,I 3 ,I 4 ,I 5 ,Is They are the rotational inertia of the engine, planetary carrier, ring gear-final reducer, wheel, vehicle, and sun gear respectively; are the angles of the above moment of inertia, the first-order derivative is the speed, and the second-order derivative is the angular acceleration; k 12 , k 34 , k 45 are the torsional stiffness of the torsional damper, half shaft and wheel respectively; c 12 、c 34 、c 45 are the damping of torsional vibration damper, half shaft and wheel respectively; T MG1 、T cl 、T AMT_out 、T b1 、T L They are the MG1 motor torque, the first wet clutch transmission torque, the MG2 motor torque output through the AMT gearbox, the braking torque and the driving resistance torque; i 0 Main reducer speed ratio; F 1 is the internal force of the planetary gear mechanism; R 1 and S 1 are the radii of the ring gear and the sun gear respectively, and their ratio is the characteristic parameter of the planetary gear mechanism.

[0016] Furthermore, the theoretical equation of the inherent characteristics of the system in step S2 is shown in formula (2):

[0017]

[0018] Where I is the moment of inertia matrix, K is the stiffness matrix, and m is the number of degrees of freedom.

[0019] By calculating the system's natural frequency and the engine's critical speed spectrum, the generation mechanism of the transmission system's torsional resonance is clarified.

[0020] Furthermore, step S3 is specifically as follows:

[0021] S31: Calculate the fluctuation component of the torque of the engine 1, and use the Hull moving average method to calculate the average value of the instantaneous torque. First, calculate the weighted moving average WMA(y,T) at time t in the entire time window T, as shown in formula (3):

[0022]

[0023] Secondly, calculate the weighted moving average WMA(y,int(T / 2)) in the most recent time window T / 2, as shown in formula (4):

[0024]

[0025] Finally, the weighted moving average HMA under the time window sqrt(T) is calculated, as shown in formula (5):

[0026] HMA=WMA((2*WMA(y,int(T / 2))-WMA(y,T)),int(sqrt(T))) (5)

[0027] S32: To calculate the compensation torque of the MG1 motor, the output control law is obtained based on the transverse filter. Let (L-1) be the order of the transverse filter, n be the discrete time, and the input vector T d (n) can be expressed as:

[0028] T d (n) = [T d (n-1), T d (n-2),…,T d (n-L+1)] T (6)

[0029] The weight vector at time n is defined as:

[0030] w(n)=[w 0 (n), w 1 (n), w 2 (n),…,w L-1 (n)] T (7)

[0031] Y(n) is the output of the transversal filter, which is obtained by weighted summation of the input signal at each moment and can be expressed as:

[0032]

[0033] The torque error can be obtained as:

[0034] e(n)=T d (n)-Y(n)=T d (n)-w T (n)x(n) (9)

[0035] S33: Based on the minimization of the performance function as the criterion, the filter parameters are adaptively updated based on the steepest descent method. According to the steepest descent principle, the formula for updating the filter weight vector along the negative gradient direction of the error performance is:

[0036]

[0037] J=E[e 2 (n)] (11)

[0038] Where μ is the convergence factor.

[0039] Furthermore, step S4 is specifically as follows:

[0040] S41: According to the transmission system dynamics equation of formula (1), establish and is the state space equation of the state variable, as shown in formula (12):

[0041]

[0042] S42: The difference between the rotation angle of the ring gear and the wheel is the feedback quantity, and the compensation torque T at the ring gear ring for:

[0043]

[0044] Then the compensation torque T of MG2 motor is MG2 for:

[0045]

[0046] Where, T ring_ref 、T MG2_ref is the required torque calculated by the energy management strategy, and f is the feedback gain, which is calculated by the pole configuration of the closed-loop characteristic equation.

[0047] S43: The closed-loop characteristic equation is derived from equation (15):

[0048]

[0049] When the damping ratio is 0, the double root calculation of the equation is shown in equation (16):

[0050]

[0051] Compared with the prior art, the advantages of the present invention are:

[0052] 1. The method for actively controlling torsional vibration of a power-split hybrid system engine during start-stop process of the present invention designs an adaptive filter feedforward control algorithm and a pole placement feedback algorithm, and solves the vehicle torsional vibration problem during the engine start-stop process through torque distribution at the ring gear with clear division of labor;

[0053] 2. The method for actively controlling torsional vibration during the start-stop process of the power-split hybrid system engine of the present invention designs an adaptive filter feedforward control algorithm, which takes into account the time-varying characteristics of the parameters of the vehicle system, and automatically adjusts the filter weight coefficient according to the feedback error and the torque fluctuation component, which can greatly reduce the control error caused by the torque mutation and achieve a good vibration reduction effect;

[0054] 3. The method for active control of torsional vibration during the start-stop process of the power-split hybrid system engine described in the present invention designs a pole configuration feedback algorithm, adjusts the motor torque in real time through the speed difference between the ring gear and the whole vehicle, reduces the vehicle jitter caused by the rapid change of the ring gear torque, and provides a new way to control the torsional vibration during the start-stop process of the hybrid system engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 A schematic diagram of the structure of a power split hybrid system used in the embodiment;

[0056] Figure 2 A flow chart of a method for active torsional vibration control during the start-stop process of an engine in a power-split hybrid system used in an embodiment;

[0057] Figure 3 The six-degree-of-freedom concentrated mass model of the transmission system used in the embodiment;

[0058] Figure 4 A schematic diagram of the periodic excitation torque output by the engine used in the embodiment;

[0059] Figure 5 Flowchart of the adaptive filter feedforward control algorithm used in the embodiment.

[0060] Labels in the figure: 1. Engine, 2. Torsional vibration damper, 3. MG1 motor, 4. MG2 motor, 5. Planetary gear mechanism, 5-1. Ring gear, 5-2. Planetary carrier, 5-3 Sun gear, 6. First wet clutch, 7. Second wet clutch, 8. Two-speed AMT gearbox, 9. Main reducer, 10. Axle shaft, 11. Wheel. DETAILED DESCRIPTION

[0061] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described examples are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] Example 1

[0063] This application proposes a power split hybrid system, such as Figure 1As shown, the hybrid system is composed of an engine 1, a torsional vibration damper 2, an MG1 motor 3, an MG2 motor 4, a planetary gear mechanism 5, a first wet clutch 6, a second wet clutch 7, a two-speed AMT gearbox 8, a final reducer 9, a half shaft 10 and a wheel 11, wherein the planetary gear mechanism 5 includes a ring gear 5-1, a planet carrier 5-2 and a sun gear 5-3. The engine 1 is connected to the planet carrier 5-2 of the planetary gear mechanism 5 through the torsional vibration damper 2, and the power is divided into an electrical path and a mechanical path, and finally converged at the final reducer 9. In the electrical path, the engine 1, the MG1 motor 3 and the first wet clutch 6 and the second wet clutch 7 act together on the planetary gear mechanism 5 to change the motion state of the planetary gear mechanism 5; in the mechanical path, the engine 1 outputs torque through the ring gear 5-1 of the planetary gear mechanism 5, and the torque output by the MG2 motor 4 through the two-speed AMT gearbox 8 is coupled with the torque at the final reducer 9 and the half shaft 10, and the wheels 11 are driven to travel together.

[0064] Example 2

[0065] A method for actively controlling torsional vibration during the start-stop process of a power-split hybrid system engine, the flow chart is as follows Figure 2 As shown. First, an adaptive filter feedforward control algorithm is designed to automatically adjust the filter weight coefficient according to the feedback error and torque fluctuation component, and output the compensation torque of MG1 motor 3; then, a pole configuration feedback algorithm is designed to solve the closed-loop characteristic equation, and the compensation torque of MG2 motor 4 is adjusted in real time through the speed difference between the ring gear and the whole vehicle; finally, the compensation torque of the two motors and the initial torque calculated by the energy management strategy are combined into the total torque of MG1 motor 3 and MG2 motor 4, which is input to the controlled vehicle. The torsional vibration active control method specifically includes:

[0066] S1: Establish the multi-degree-of-freedom dynamic equations of the transmission system for simulating the engine start-stop torsional vibration phenomenon.

[0067] like Figure 3 As shown, the multi-degree-of-freedom dynamics equation is shown in formula (1):

[0068]

[0069] In the formula, I 1 ,I 2 ,I 3 ,I 4 ,I 5 ,I s They are the moments of inertia of the engine 1, the planet carrier 5-2, the ring gear-final reducer, the wheel 11, the vehicle, and the sun gear 5-3; are the angles of the above moment of inertia, the first-order derivative is the speed, and the second-order derivative is the angular acceleration; k 12 , k 34 , k45 are the torsional stiffness of the torsional vibration damper 2, the half shaft 10 and the wheel 11 respectively; c 12 、c 34 、c 45 are the damping of the torsional vibration damper 2, the half shaft 10 and the wheel 11 respectively; T MG1 、T cl 、T AMT_out 、T b1 、T L They are respectively the torque of the MG1 motor 3, the torque transmitted by the first wet clutch 6, the torque output by the MG2 motor 4 via the AMT gearbox 8, the braking torque and the driving resistance torque; i 0 Main reducer 9 speed ratio; F 1 is the internal force of the planetary gear mechanism 5; R 1 and S 1 They are the radii of the ring gear 5 - 1 and the sun gear 5 - 3 respectively, and the ratio between them is the characteristic parameter of the planetary gear mechanism 5 .

[0070] S2: Based on the multi-degree-of-freedom dynamics equations in S1, the dynamic response of the engine start-stop process of the planetary multi-speed hybrid system is obtained. Figure 4 is the periodic excitation torque of the engine, ignoring external excitation and system damping, and obtaining the theoretical equation of the inherent characteristics of the system,

[0071] The theoretical equation of the inherent characteristics of the system is shown in formula (2):

[0072]

[0073] Where I is the moment of inertia matrix, K is the stiffness matrix, and m is the number of degrees of freedom.

[0074] By calculating the system's natural frequency and the engine's critical speed spectrum, the generation mechanism of the transmission system's torsional resonance is clarified.

[0075] S3: Considering the excitation input of the engine, LMS adaptive filter control is applied to the field of torsional vibration control. An adaptive filter feedforward control algorithm is designed to offset the fluctuation components of the engine gas torque and inertia torque. The torque compensation is calculated and distributed to MG1 motor 3 and MG2 motor 4 to control the torsional vibration at the engine end. The flow chart is as follows: Figure 5 shown.

[0076] The specific calculation method is:

[0077] S31: Calculate the fluctuation component of the torque of the engine 1, and use the Hull moving average method to calculate the average value of the instantaneous torque. First, calculate the weighted moving average WMA(y,T) at time t in the entire time window T, as shown in formula (3):

[0078]

[0079] Secondly, calculate the weighted moving average WMA(y,int(T / 2)) in the most recent time window T / 2, as shown in formula (4):

[0080]

[0081] Finally, the weighted moving average HMA under the time window sqrt(T) is calculated, as shown in formula (5):

[0082] HMA=WMA((2*WMA(y,int(T / 2))-WMA(y,T)),int(sqrt(T))) (5)

[0083] S32: To calculate the compensation torque of MG1 motor 3, the output control law is obtained based on the transverse filter. Let (L-1) be the order of the transverse filter, n be the discrete time, and the input vector T d (n) can be expressed as:

[0084] T d (n) = [T d (n-1), T d (n-2),…,T d (n-L+1)] T (6)

[0085] The weight vector at time n is defined as:

[0086] w(n)=[w 0 (n), w 1 (n), w 2 (n),…,w L-1 (n)] T (7)

[0087] Y(n) is the output of the transversal filter, which is obtained by weighted summation of the input signal at each moment and can be expressed as:

[0088]

[0089] The torque error can be obtained as:

[0090] e(n)=T d (n)-Y(n)=T d (n)-w T (n)x(n) (9)

[0091] S33: Taking the minimization of the performance function as the criterion, the filter parameters are adaptively updated based on the steepest descent method. According to the steepest descent principle, the formula for updating the filter weight vector along the negative gradient direction of the error performance is:

[0092]

[0093] J=E[e 2 (n)] (11)

[0094] Where μ is the convergence factor.

[0095] S4: Considering the disturbance input of the start-stop process of engine 1, a pole placement feedback algorithm is designed to calculate the motor torque compensation, and the torsional amplitude is reduced from the drive shaft of the transmission system to the wheels, so that the engine start process of the power split hybrid system is smoother. The specific calculation method is:

[0096] S41: According to the transmission system dynamics equation of formula (1), establish and is the state space equation of the state variable, as shown in formula (12):

[0097]

[0098] S42: The angle difference between the gear ring 5-1 and the wheel is the feedback quantity, and the compensation torque T at the ring gear ring for:

[0099]

[0100] Then the compensation torque T of MG2 motor 4 is MG2 for:

[0101]

[0102] Where, T ring_ref 、T MG2_ref is the required torque calculated by the energy management strategy, and f is the feedback gain, which is calculated by the pole configuration of the closed-loop characteristic equation.

[0103] S43: The closed-loop characteristic equation is derived from equation (15):

[0104]

[0105] When the damping ratio is 0, the double root calculation of the equation is shown in equation (16):

[0106]

[0107] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A power split hybrid system, characterized in that: The hybrid power system comprises an engine (1), a torsional vibration damper (2), an MG1 motor (3), an MG2 motor (4), a planetary gear mechanism (5), a first wet clutch (6), a second wet clutch (7), a two-speed AMT gearbox (8), a main reducer (9), a half shaft (10) and a wheel (11), wherein the planetary gear mechanism (5) comprises a ring gear (5-1), a planetary carrier (5-2) and a sun gear (5-3); the engine (1) is connected to the planetary carrier (5-2) of the planetary gear mechanism (5) through the torsional vibration damper (2), and the power is divided into an electrical path and a mechanical path, and finally converged at the main reducer (9).

2. A method for actively controlling torsional vibration during the start-stop process of a power-split hybrid system engine, the method being based on the hybrid system of claim 1, characterized in that: The method comprises the following steps: S1: Establish the multi-degree-of-freedom dynamic equations of the transmission system for simulating the engine start-stop torsional vibration phenomenon; S2: Based on the multi-degree-of-freedom dynamic equations in S1, the dynamic response of the engine start-stop process of the planetary multi-speed hybrid system is obtained, and the external excitation and system damping are ignored to obtain the theoretical equation of the inherent characteristics of the system; S3: Considering the excitation input of the engine, LMS adaptive filter control is applied to the field of torsional vibration control, and an adaptive filter feedforward control algorithm is designed to offset the fluctuation components of the engine gas torque and inertia torque. The torque compensation amount is calculated and distributed to the MG1 motor (3) and the MG2 motor (4) to control the torsional vibration at the engine end; S4: Considering the disturbance input of the engine (1) start-stop process, a pole configuration feedback algorithm is designed to calculate the motor torque compensation, and the torsional amplitude is reduced from the transmission system drive shaft to the wheel, so that the engine start process of the power split hybrid system is smoother.

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