Planetary multi-gear hybrid power system and active robust vibration reduction control method

Abstract

The invention relates to an active robust vibration reduction control method for a planetary multi-gear hybrid power system, and aims to solve the problem of robust control in the mode switching process of the planetary multi-gear hybrid power system under the influence of interference. The method comprises the following steps: firstly, establishing a multi-degree-of-freedom kinetic equation of an electric path and a mechanical path of the planetary multi-gear hybrid power system according to a torsional vibration kinetic relationship of a transmission system; then, calculating a feedforward target reference value according to the reference rotating speed of the engine, the hub torque requirement and the rigidity damping characteristic of the transmission system; and finally, bringing the closed-loop tracking error of each reference value and control input into a performance optimization index, establishing association with external interference suffered by the transmission system, and solving a motor torque control law by adopting an H-infinity control algorithm. The mode switching time and the torque fluctuation amplitude are effectively reduced, and the robust tracking control problem of the power source under the uncertain condition is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile torsional vibration control, and in particular relates to an active robust vibration reduction control method for a planetary multi-speed hybrid power system. Background Art

[0002] During the mode switching process, the engine, motor, wet clutch and other components are all involved. The superposition of different dynamic characteristics of multiple components can easily cause the actual output torque to change dramatically in a short period of time, resulting in oscillation of the transmission system speed and torque. Severe torsional vibration may even cause the drive shaft to break and damage the torsional vibration damper. Compared with other hybrid systems, the planetary multi-speed hybrid system has more working modes, and the torsional vibration response of the core components of the transmission system under the action of the excitation source is more complex, making vibration reduction control more difficult; in addition, the planetary multi-speed hybrid system has two degrees of freedom of movement, and the power transmission process has multiple path options and can achieve two-way transmission. The complex power transmission process makes the hybrid system more sensitive to torque shocks and is more likely to cause abnormal torsional vibration problems at weak points in the mechanical system.

[0003] Some existing patents, such as the invention patent with patent number CN113428157B, propose a method for adaptive active control of torsional vibration of a hybrid powertrain system, which uses a feedforward filter to calculate the reverse compensation torque of the motor to offset the torque fluctuation component generated by the operation of the engine. The invention patent with patent number CN117841962A proposes a method for torsional vibration offset of a DHT hybrid powertrain system and a hybrid powertrain system, which obtains the torque output function of the output torque of the engine at various speeds and torques as the crankshaft connecting rod angle changes, calculates the required offset torque, and determines the offset torque command corresponding to the motor according to the required offset torque. However, the existing vibration reduction algorithms usually pay little attention to the influence of model parameter uncertainty and external interference on control performance, and it is difficult to ensure control performance in practical applications; therefore, how to develop an active vibration reduction control algorithm for a planetary multi-speed hybrid powertrain system with strong robustness to achieve the goal of weakening torque oscillation and reducing longitudinal impact is a difficulty that needs to be solved urgently. Summary of the invention

[0004] The present invention proposes a planetary multi-speed hybrid power system and an active robust vibration reduction control method. In order to overcome the problem that the control performance of the existing active vibration reduction algorithm is affected by model parameter uncertainty and external interference, the method establishes a correlation between factors such as parameter disturbance and uncertain interference, and superimposes feedback robust control quantities on the basis of feedforward control, so as to jointly achieve stable tracking of target values ​​of various state variables of the transmission system under multi-excitation.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A planetary multi-speed hybrid power system, the planetary multi-speed hybrid power 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 divided into an electrical path and a mechanical path, and finally converged at the main reducer.

[0007] An active robust vibration reduction control method for a planetary multi-speed hybrid power system comprises the following steps:

[0008] S1: Establishing a discretized model with multiple degrees of freedom

[0009] S2: Based on the energy management strategy, engine reference speed, wheel torque demand and transmission system rigidity and flexibility characteristics, the feedforward target reference value is calculated, including the ring gear speed, torsional vibration damper torsion angle, half-shaft torsion angle and motor feedforward torque target.

[0010] S3: Design H ∞ The robust control algorithm incorporates the closed-loop tracking error of the feedforward target reference value and the control input into the performance optimization index, and establishes a correlation with the external disturbance of the transmission system to solve the motor torque feedback control law.

[0011] S4: Add the feedforward torque target value and torque feedback value of the MG1 motor and the MG2 motor obtained in the above steps to form a motor total torque control law, which is output to the controlled vehicle.

[0012] Furthermore, step S1 is specifically as follows:

[0013] Due to the uneven distribution of mass and elasticity of various components in the vehicle transmission system, it is necessary to simplify each component to a certain extent when performing dynamic modeling and establish a multi-degree-of-freedom discretized model in order to achieve an ideal vibration reduction control effect.

[0014] According to the six-degree-of-freedom dynamics model of the transmission system, the dynamics equations of the electrical path and the mechanical path are listed respectively, as shown in equations (1) and (2):

[0015]

[0016] In formula (1) and formula (2), I1, I2, I3, I4, I5, I s They are the moments of inertia of the engine, planet carrier, ring gear, wheel, vehicle, and sun gear; are the angles of the above moments of inertia; k 12 , k 34 , k 45are 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 b1 are MG1 motor torque and braking torque respectively; T MG2 , T AMT_out , T b1 , T f are the MG2 motor torque, the torque output by the MG2 motor through the AMT gearbox, the braking torque, and the driving resistance torque; i0, i AMT are the speed ratio of the main reducer and the speed ratio of the AMT gearbox respectively; F1 is the internal force of the planetary gear mechanism; R1 and S1 are the radii of the ring gear and the sun gear respectively.

[0017] Furthermore, step S2 is specifically as follows:

[0018] S21: Calculate the speed ω at the ring gear according to the vehicle speed following requirement r ;

[0019]

[0020] In formula (3), v is the vehicle speed; R t is the wheel radius.

[0021] S22: Calculate the shock absorber torsion angle based on the stiffness and damping characteristics of the transmission system Torsion angle with half axis

[0022]

[0023] S23: The energy management strategy outputs the feedforward torque target values ​​of the MG1 motor and the MG2 motor according to the vehicle status information and the driver's demand.

[0024] The purpose is to ensure that each state variable changes around its target reference value. Theoretically, if the system model is accurate enough and there is no external interference, after the torque of the MG1 motor and MG2 motor under feedforward control is applied to the transmission system, the state variable response obtained is almost the same as the target reference value.

[0025] Furthermore, step S3 is specifically as follows:

[0026] S31: Based on formulas (1) and (2), the transmission system state equation is established as:

[0027]

[0028] Under the electric path, the state variable x inis the engine speed, planet carrier speed, sun gear speed, the difference between the engine reference speed and the actual speed, and the difference between the damper reference torsion angle and the actual torsion angle, w in is external disturbance, and the control variable x in is the MG1 motor torque, which is specifically shown in formula (7):

[0029]

[0030] Parameter matrix A under the electrical path in , B in1 , B in2 It can be expressed as:

[0031]

[0032] Under the mechanical path, the state variable x in is the speed of the ring gear and the difference between the reference torsion angle of the reducer and the half shaft and the actual torsion angle, w in is external disturbance, and the control variable x in is the MG2 motor torque, which is specifically shown in formula (9):

[0033]

[0034] Parameter matrix A under mechanical path in , B in1 , B in2 It can be expressed as:

[0035]

[0036] S32: In order to improve the system's ability to cope with parameter perturbations, equation (6) can be rewritten as follows:

[0037]

[0038] In the formula, ΔA in is the parameter perturbation matrix, ΔA in =EΣ(t)F, E and F are matrices of known appropriate dimensions, Σ(t) is the uncertainty matrix, and Σ T (t)∑(t)≤I.

[0039] Taking into account the engine speed tracking error, the shock absorber and the half-shaft torsion angle tracking error and the constraints on the system control quantity, the designed output function is:

[0040] z in =C in1 x in +D in12 u1 (12)

[0041] The design objective function is:

[0042]

[0043] Among them, Q in , R in are the weight matrices set, Q in =diag(0,q in1 ,0,q in2 ,0,0), R=[r in ] 1×1 ,q in1 ,q in2 、r in are the corresponding weighting coefficients respectively.

[0044]

[0045] Substituting equation (12) and equation (14) into the objective function equation (9), the objective function can be rewritten as the standard equation (15):

[0046]

[0047] S33: To calculate the minimum performance index γ of the closed-loop system in , the LMI feasible solution condition of formula (16) needs to be satisfied:

[0048]

[0049] By calling Matlab's LMI toolbox for optimization and solution, the state feedback matrix can be obtained Make performance indicators γ in Minimum, thus ensuring the stability and robustness of the closed-loop system.

[0050] According to H ∞ The standard state feedback form of the controller is u1=K in x in , the motor torque feedback control law can be finally obtained.

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

[0052] 1. The active robust vibration reduction control method for a planetary multi-speed hybrid power system of the present invention solves the problem of active suppression of torsional vibration during mode switching, improves the stability of lever attitude adjustment and torque balance, and provides a new approach to torsional vibration control of a planetary multi-speed hybrid power system;

[0053] 2. The active robust vibration reduction control method for a planetary multi-speed hybrid power system described in the present invention incorporates the closed-loop error and control input in the control problem into the performance optimization index, and establishes a correlation with unknown factors such as external parameter perturbations, uncertainty interference and unmodeled dynamics of the transmission system, thereby ensuring the robust performance of the algorithm;

[0054] 3. The active robust vibration reduction control method for a planetary multi-speed hybrid power system described in the present invention divides the active control structure into two parts: feedforward and feedback. The feedforward part is used to calculate the expected values ​​of the rotational speed, torsion angle and motor torque. The robust feedback control incorporates the torsion angle into the feedback tracking control to limit the torque fluctuation amplitude. This method has important guiding significance for solving the torsional vibration problem during the mode switching process of hybrid vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 A schematic diagram of the structure of a planetary multi-speed hybrid power system used in the embodiment;

[0056] Figure 2 A flow chart of an active robust vibration reduction control method for a planetary multi-speed hybrid power system adopted in an embodiment;

[0057] Figure 3 A six-degree-of-freedom dynamic model of a planetary multi-speed hybrid power system used in the embodiment.

[0058] Markings in the figure: 1. Engine, 2. Torsional vibration damper, 3. MG1 motor, 4. MG2 motor, 5. Planetary gear mechanism (ring gear 5-1, planet carrier 5-2, sun gear 5-3), 6. Wet clutch CL1, 7. Wet clutch CL2, 8. Two-speed AMT gearbox, 9. Main reducer, 10. Axle shaft, 11. Wheel. DETAILED DESCRIPTION

[0059] 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.

[0060] Example 1

[0061] A planetary multi-speed hybrid power system, such as Figure 1As shown, the planetary multi-speed 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.

[0062] Example 2

[0063] The active robust vibration reduction control method of the planetary multi-speed hybrid system is divided into two parts: feedforward reference value calculation and robust feedback control. The flow chart is as follows: Figure 2 First, according to the engine reference speed, wheel torque demand and transmission system stiffness and damping characteristics, the feedforward target reference value under each working condition is solved; then, H ∞ As the basic method for designing a vehicle torsional vibration controller, the control algorithm incorporates the closed-loop tracking error and control input of each reference value into the performance optimization index, and establishes a correlation with the external parameter perturbations and uncertainty interferences of the transmission system; finally, the control problem is converted into the standard LMI form and the motor torque control law is solved.

[0064] The active robust vibration reduction control method of the hybrid power system specifically includes:

[0065] S1: Establishing a discretized model with multiple degrees of freedom

[0066] Due to the uneven distribution of mass and elasticity of various components in the vehicle transmission system, it is necessary to simplify each component to a certain extent when performing dynamic modeling and establish a multi-degree-of-freedom discretization model, such as Figure 3 To achieve the ideal vibration reduction control effect.

[0067] in accordance with Figure 3 The six-degree-of-freedom dynamic model of the transmission system is constructed, and the dynamic equations of the electrical path and the mechanical path are written respectively, as shown in equations (1) and (2):

[0068]

[0069]

[0070] In formula (1) and formula (2), I1, I2, I3, I4, I5, I s They are the moments of inertia of the engine 1, the planet carrier 5-2, the ring gear 5-1, the wheel 11, the whole vehicle, and the sun gear 5-3; are the angles of the above moments of inertia; k 12 , k 34 , k 45 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 b1 are MG1 motor 3 torque and braking torque respectively; T MG2 , T AMT_out , T b1 , T f are the torque of the MG2 motor 4, the torque output by the MG2 motor 4 through the AMT gearbox 8, the braking torque and the driving resistance torque; i0, i AMT They are the speed ratio of the main reducer and the speed ratio of AMT gearbox 8; F1 is the internal force of the planetary gear mechanism 5; R1 and S1 are the radii of the ring gear 5-1 and the sun gear 5-3 respectively.

[0071] S2: Based on the energy management strategy, engine reference speed, wheel torque demand and transmission system rigidity and flexibility characteristics, the feedforward target reference value is calculated, including the ring gear speed, torsional vibration damper torsion angle, half-shaft torsion angle and motor feedforward torque target.

[0072] The specific calculation method is:

[0073] S21: Calculate the speed ω at the ring gear according to the vehicle speed following requirement r ;

[0074]

[0075] In formula (3), v is the vehicle speed; R t is the wheel radius.

[0076] S22: Calculate the shock absorber torsion angle based on the stiffness and damping characteristics of the transmission system Torsion angle with half axis

[0077]

[0078] S23: The energy management strategy outputs the feedforward torque target values ​​of MG1 motor 3 and MG2 motor 4 according to the vehicle status information and the driver's demand.

[0079] The purpose is to ensure that each state variable changes around its target reference value. Theoretically, if the system model is accurate enough and there is no external interference, after the torque of MG1 motor 3 and MG2 motor 4 under feedforward control is applied to the transmission system, the state variable response obtained is almost the same as the target reference value.

[0080] S3: Design H ∞ The robust control algorithm incorporates the closed-loop tracking error of the feedforward target reference value and the control input into the performance optimization index, and establishes a correlation with the external disturbance of the transmission system to solve the motor torque feedback control law.

[0081] The specific calculation method is:

[0082] S31: Based on formulas (1) and (2), the transmission system state equation is established as:

[0083]

[0084] Under the electric path, the state variable x in is the engine speed, planet carrier speed, sun gear speed, the difference between the engine reference speed and the actual speed, and the difference between the damper reference torsion angle and the actual torsion angle, w in is external disturbance, and the control variable x in is the MG1 motor torque, which is specifically shown in formula (7):

[0085]

[0086] Parameter matrix A under the electrical path in , B in1 , B in2 It can be expressed as:

[0087]

[0088] Under the mechanical path, the state variable x in is the speed of the ring gear and the difference between the reference torsion angle of the reducer and the half shaft and the actual torsion angle, w in is external disturbance, and the control variable x in is the MG2 motor torque, which is specifically shown in formula (9):

[0089]

[0090] Parameter matrix A under mechanical path in , B in1 , B in2 It can be expressed as:

[0091]

[0092] S32: In order to improve the system's ability to cope with parameter perturbations, equation (6) can be rewritten as follows:

[0093]

[0094] In the formula, ΔA in is the parameter perturbation matrix, ΔA in =EΣ(t)F,E and F is a matrix of known suitable dimension, ∑(t) is an uncertainty matrix, and ∑ T (t)∑(t)≤I.

[0095] Taking into account the engine speed tracking error, the shock absorber and the half-shaft torsion angle tracking error and the constraints on the system control quantity, the designed output function is:

[0096] z in =C in1 x in +D in12 u1 (12)

[0097] The design objective function is:

[0098]

[0099] Among them, Q in , R in are the weight matrices set, Q in =diag(0,q in1 ,0,q in2 ,0,0), R=[r in ] 1×1 ,q in1 ,q in2 、r in are the corresponding weighting coefficients respectively.

[0100]

[0101] Substituting equation (12) and equation (14) into the objective function equation (9), the objective function can be rewritten as the standard equation (15):

[0102]

[0103] S33: To calculate the minimum performance index γ of the closed-loop system in , the LMI feasible solution condition of formula (16) needs to be satisfied:

[0104]

[0105] By calling Matlab's LMI toolbox for optimization and solution, the state feedback matrix can be obtained Make performance indicators γ in Minimum, thus ensuring the stability and robustness of the closed-loop system.

[0106] According to H ∞ The standard state feedback form of the controller is u1=K in x in , the motor torque feedback control law can be finally obtained.

[0107] S4: Add the feedforward torque target value and torque feedback value of the MG1 motor and the MG2 motor obtained in the above steps to form a motor total torque control law, which is output to the controlled vehicle.

[0108] 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 planetary multi-speed hybrid power system, characterized in that: The planetary multi-speed 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 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 main reducer (9).

2. An active robust vibration reduction control method for a planetary multi-speed hybrid power system as claimed in claim 1, characterized in that: The steps include: S1: Establish a discretization model with multiple degrees of freedom; S2: Calculate the feedforward target reference value based on the energy management strategy, engine reference speed, wheel torque demand, and transmission system rigidity and flexibility characteristics, including the ring gear speed, torsional vibration damper torsion angle, half-shaft torsion angle, and motor feedforward torque target; S3: Design H ∞ Robust control algorithm, which incorporates the closed-loop tracking error of the feedforward target reference value and the control input into the performance optimization index, and establishes a correlation with the external disturbance of the transmission system to solve the motor torque feedback control law; S4: Add the feedforward torque target value and torque feedback value of the MG1 motor and the MG2 motor obtained in the above steps to form a motor total torque control law, which is output to the controlled vehicle.

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