An analytical method for vibration characteristics of a heavy-duty hybrid vehicle transmission system

Abstract

This invention provides a method for analyzing the vibration characteristics of a heavy-duty hybrid vehicle transmission system, relating to the technical fields of mechanical and vehicle transmission systems. The method includes establishing a 17-DOF lumped-parameter torsional vibration dynamic model of the heavy-duty hybrid vehicle transmission system; based on the dynamic model, analyzing the system's inherent vibration characteristics, performing parameter sensitivity analysis and resonance avoidance; solving the system dynamic model using the Runge-Kutta method; and performing stress verification. This invention significantly improves the accuracy of vibration characteristic analysis for complex systems, accurately identifying key stiffness parameters that have the greatest impact on the system's low-order natural frequencies, making vibration control more targeted, effectively ensuring system reliability over a wide operating range, and possessing good versatility and engineering guidance significance. Its structured and modular design can be extended to similar transmission systems, providing complete technical support for the design optimization and fault diagnosis of heavy-duty hybrid vehicles.

Description

Technical Field

[0001] This invention relates to the field of transmission system technology, such as machinery and vehicles, and in particular to a method for analyzing the vibration characteristics of a transmission system in a heavy-duty hybrid vehicle. Background Technology

[0002] The heavy-duty vehicle sector is actively seeking new power solutions to replace traditional internal combustion engine systems. Due to the advantages of hybrid power systems in terms of power and economy, the powertrain system, as a core component ensuring normal vehicle operation, makes the research and maintenance of its safety and reliability particularly important. The powertrain system of a hybrid vehicle is a complex multi-degree-of-freedom system involving multiple mass points, and its torsional vibration characteristics significantly impact the vehicle's ride comfort and component lifespan. Therefore, analyzing the vibration characteristics of the electromechanical hybrid powertrain system in heavy-duty vehicles and avoiding the overlap between the input excitation frequency and the powertrain system's natural frequency in multi-power source coupling systems are crucial for improving the performance of hybrid vehicles.

[0003] Currently, research on torsional vibration and stress characteristics of powertrain systems in heavy-duty hybrid vehicles largely focuses on engines with fewer cylinders (such as three-cylinder or four-cylinder) or power-split hybrid systems, and generally employs low-degree-of-freedom rigid connection dynamic models, making it difficult to accurately reflect the true torsional vibration characteristics of complex systems. Although existing research has made some progress in simplifying operating condition analysis, it still has a core deficiency: insufficient understanding of torsional vibration characteristics under multi-source excitation coupling, especially in complex powertrain systems involving multi-cylinder high-power engines (such as ten-cylinder V-type diesel engines) and dual-motor parallel drives. The vibration response mechanism caused by the complex torque harmonic excitation of the engine and the dynamic coupling of the motor torque has not yet been fully revealed.

[0004] The aforementioned major deficiencies have further led to several secondary problems, including insufficient attention to dynamic stress concentration under low-speed, high-torque conditions and a lack of in-depth analysis of the vibration coupling mechanism of the drivetrain after the intervention of the electric drive system. These problems collectively make it difficult for existing methods to accurately assess the vibration response characteristics of the drivetrain, and also restrict the design of effective vibration control strategies, thereby limiting further improvements in vehicle reliability and comfort.

[0005] In summary, it is essential to design an analytical method for the vibration characteristics of the transmission system of heavy-duty hybrid vehicles. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a method for analyzing the vibration characteristics of a heavy-duty hybrid vehicle transmission system.

[0007] To achieve the above objectives, the present invention provides the following solution: This invention provides a method for analyzing the vibration characteristics of a heavy-duty hybrid vehicle transmission system, comprising: Step 1: Establish a 17-DOF lumped parameter torsional vibration dynamic model of the powertrain system of a heavy-duty hybrid vehicle; Step 2: Analyze the inherent vibration characteristics of the system based on the dynamic model; Step 3: If the analysis shows that there is a risk of resonance between the system's natural frequency modes and the excitation modes, then perform parameter sensitivity analysis and resonance avoidance. Step 4: If the analysis shows that there is no risk of resonance between the system's natural frequency modes and excitation modes, then solve the system dynamics model based on the Runge-Kutta method and perform stress verification.

[0008] Preferably, in step 1, a 17-DOF lumped parameter torsional vibration dynamic model of the heavy-duty hybrid vehicle transmission system is established, specifically as follows: Step 101: Construct the transmission system topology; Step 102: Based on the lumped parameter method, the transmission system is simplified into a 17-DOF lumped parameter torsional vibration dynamic model, and the control equations characterizing the overall torsional vibration characteristics of the system are obtained based on the 17-DOF lumped parameter torsional vibration dynamic model. Step 103: Establish an engine torsional vibration model based on the state of each cylinder; Step 104: Establish the dynamic model of the motor.

[0009] Preferably, the transmission system topology specifically includes a fixed-axis gear transmission system, a coupling bus, a reduction bus system, and a speed change bus system, wherein the reduction bus system and the speed change bus system are symmetrical about the coupling bus.

[0010] Preferably, in step 2, the inherent vibration characteristics of the system are analyzed based on the dynamic model, specifically as follows: Step 201: Rewrite the governing equations characterizing the overall torsional vibration properties of the system into matrix form; Step 202: Based on the rewritten matrix form, calculate the differential equation of the undamped free vibration of the system.

[0011] Step 203: Rewrite the differential equation of the undamped free vibration of the system to obtain the equation related to the natural frequency of the system, and analyze the natural vibration characteristics of the system based on the equation. Step 204: Compare the obtained system natural frequency modes with the excitation modes to determine whether there is a risk of resonance between them.

[0012] Preferably, in step 202, based on the rewritten matrix form, the differential equation for the undamped free vibration of the system is calculated, specifically as follows: Obtain the governing equations representing the overall torsional vibration characteristics of the system, rewritten as matrices. Neglecting system damping, obtain the differential equations for the undamped free vibration of the system.

[0013] Preferably, in step 3, parameter sensitivity analysis and resonance avoidance are performed, specifically as follows: Step 301: Derive the formula for the sensitivity of stiffness parameters to natural frequency; Step 302: Perform sensitivity analysis based on the sensitivity formula to determine the component with the highest sensitivity to the natural frequency; Step 303: Adjust the stiffness value of the determined components to avoid resonance.

[0014] Preferably, in step 303, the stiffness value of the determined component is adjusted to avoid resonance, specifically as follows: Adjust the stiffness value of the determined components; Recalculate the system's natural frequency; Determine whether the system's natural frequency coincides with the excitation frequency. If they coincide, repeat step 3; otherwise, output the parameters and execute subsequent operations.

[0015] Preferably, in step 4, the system dynamics model is solved based on the Runge-Kutta method, and stress verification is performed, specifically as follows: The system dynamics model is solved using the Runge-Kutta method to obtain the working state and stress of key components in the system. The working stress is then checked to verify the reliability of the system.

[0016] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: This invention provides a method for analyzing the vibration characteristics of a heavy-duty hybrid vehicle transmission system. The method includes establishing a 17-DOF lumped-parameter torsional vibration dynamic model of the transmission system, analyzing the system's inherent vibration characteristics based on the dynamic model, performing parameter sensitivity analysis and resonance avoidance, solving the system dynamic model using the Runge-Kutta method, and performing stress verification. This invention yields significant technological advancements and numerous beneficial effects, specifically: 1. Significantly improved accuracy: In response to the problem that existing technologies generally use low-degree-of-freedom rigid connection models, which are difficult to accurately reflect the real torsional vibration characteristics of complex systems, this invention constructs a 17-degree-of-freedom lumped parameter torsional vibration dynamic model, which fully considers the excitation characteristics of each cylinder of the engine, the dynamic response behavior of the motor, and the inertia, stiffness and damping parameters of transmission components such as gears, shafts and planetary gear sets, thereby more accurately characterizing the complex torsional vibration behavior under multi-source excitation coupling.

[0017] 2. Strong targeting of key parameter identification and optimization: To address the problem that existing research lacks sufficient understanding of torsional vibration characteristics under multi-source excitation coupling and is difficult to effectively guide vibration control, this invention introduces parameter sensitivity analysis to systematically identify the key stiffness parameters that have the greatest impact on the low-order natural frequencies of the system, making the optimization design objectives clear and significantly improving the effectiveness of vibration control strategies.

[0018] 3. Improved reliability assurance mechanism: In view of the problem that existing technologies do not pay enough attention to dynamic stress concentration under low speed and high torque conditions and stress assessment under all working conditions, this invention comprehensively simulates and analyzes the inherent characteristics and forced vibration response of the system in the entire working condition range, accurately calculates and verifies the torsional stress of key shaft sections, and combines resonance avoidance design to ensure the reliability and durability of the system in a wide working condition range.

[0019] 4. The method has good versatility: Considering that existing research is mostly limited to specific types of engines or power-split hybrid power systems, the modeling, analysis and optimization method proposed in this invention has structured and modular features, and can be extended to other heavy-duty hybrid vehicle transmission systems with similar structures, thus promoting the solution of common problems in related fields.

[0020] 5. Clear engineering guidance significance: In order to overcome the limitations of existing technologies that restrict engineering applications due to model simplification and insufficient understanding of mechanisms, this invention not only provides a complete technical process from modeling and simulation to parameter optimization, but also clearly reveals the vibration coupling mechanism of multi-cylinder high-power engines and dual-motor parallel drive, providing a reliable theoretical basis and practical means for the design improvement, operation optimization and fault diagnosis of transmission systems. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic diagram of the powertrain topology of a parallel hybrid vehicle; Figure 2 This is a schematic diagram of the force analysis of a single cylinder of the engine; Figure 3 This is a schematic diagram of the excitation torque of a single cylinder in an engine. Figure 4a A schematic diagram of the time-domain vibration of a ten-cylinder engine under coupled overall excitation; Figure 4b A schematic diagram of frequency domain vibration of a ten-cylinder engine under coupled overall excitation; Figure 5aThis is a schematic diagram of the stiffness and sensitivity of each component at the natural frequency of 11.4Hz. Figure 5b A schematic diagram of the stiffness and sensitivity of each component at the natural frequency of 18.8Hz; Figure 6 This is a schematic diagram of the torsional stress on the connecting shaft of gear 4-5; Figure 7 A schematic diagram showing the comparative analysis results of torsional stress and allowable stress on the gear 4-gear 5 connecting shaft within the engine's operating range; Figure 8 This is a flowchart of the method of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] The purpose of this invention is to provide an analysis method for the vibration characteristics of a heavy-duty hybrid vehicle transmission system, which significantly improves the accuracy of vibration characteristic analysis of complex systems. It can accurately identify the key stiffness parameters that have the greatest impact on the low-order natural frequencies of the system, making vibration control more targeted. It effectively ensures the reliability of the system over a wide range of operating conditions, has good versatility and engineering guidance significance, and its structured and modular design can be extended to similar transmission systems, providing complete technical support for the design optimization and fault diagnosis of heavy-duty hybrid vehicles.

[0025] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] like Figure 8 As shown, this invention provides a method for analyzing the vibration characteristics of a heavy-duty hybrid vehicle transmission system, including: Step 1: Establish a 17-DOF lumped parameter torsional vibration dynamic model of the powertrain system of a heavy-duty hybrid vehicle; Step 2: Analyze the inherent vibration characteristics of the system based on the dynamic model; Step 3: If the analysis shows that there is a risk of resonance between the system's natural frequency modes and the excitation modes, then perform parameter sensitivity analysis and resonance avoidance. Step 4: If the analysis shows that there is no risk of resonance between the system's natural frequency modes and excitation modes, then solve the system dynamics model based on the Runge-Kutta method and perform stress verification.

[0027] In step 1, a 17-DOF lumped-parameter torsional vibration dynamic model of the heavy-duty hybrid vehicle's transmission system is established, specifically as follows: The transmission system consists of a fixed-axis gear transmission system, a coupling chain, a reduction gear system, and a speed change gear system. The reduction gear system and the speed change gear system are symmetrical about the coupling chain, as shown below. Figure 1 As shown, PG1 is the reduction gearbox and PG5 is the speed change gearbox. The electromechanical composite transmission system includes basic structures such as a fixed-axis gear system, a planetary gear system, a transmission shaft, and a motor. This invention simplifies the model by abstracting the coupling gear set as an equivalent inertia to facilitate the analysis of the vibration characteristics of the power transmission system. J p This represents the moment of inertia of each component in the power transmission system (p takes values ​​of 0, 1, 2, 3, 4, 5, 6, o, A, s1, r1, g1, r3, c3, s3, g3, representing each gear component in the fixed-axis gear system and planetary gear system of the transmission system). K pq and C pq (q takes values ​​1, 2, 3, 4, 5, 6, o, A, s1, r1, g1, b, r3, c3, s3, g3, and V, which respectively represent the gear components in the fixed-axis gear system and planetary gear system of the transmission system and the inertia of the vehicle body.) respectively represent the stiffness and damping of the connecting shaft between different components in the fixed-axis gear system, reduction gear system, and gearbox system, as well as the meshing stiffness and damping of the gears in the transmission system; The model is based on the following assumptions: 1. The torsional vibration system is linear; 2. System clearance is ignored. The dynamic equations for the low-speed, high-torque mode, described using the lumped parameter method, are as follows: For engine steering angle parameters, For gear radius parameters, This refers to the meshing force between the gears in a gear train.

[0028] (1) (2) (3) (4) (5) (6) (7) The meshing force between each gear The calculation formula is: (8) In the formula, and For example, ; The dynamic model of the motor reduction gear system is as follows: (9) in, For the meshing force between the sun gear and the planet gears, The meshing force between the planetary gears and the ring gear, R g R is the radius of the planetary gear. r For the radius of the planetary gear: (10) The coupled-row dynamics model is as follows: (11) The dynamic model of the motor speed change system is shown below, where For the output shaft torque of the variable speed drive, Torque is transmitted to the connecting shaft between the coupling bus and the speed change bus. (12) The meshing force between the sun gear, planet gears, and ring gear is: (13) (14) (15) (16) (17) Based on the above dynamic model, the governing equations characterizing the overall torsional vibration properties of the system can be derived as follows: (18) (19) in, and Let these represent the stiffness matrix and damping matrix of the system, respectively, and the state vector in the equation be... Represented as: (20) The engine uses a ten-cylinder V-type diesel engine model. The output torque includes components of combustion gas pressure and inertial force. The periodic changes in in-cylinder combustion gas pressure and the periodic reciprocating motion of the crankshaft connecting rod mechanism cause periodic fluctuations in engine torque. A torsional vibration model of the engine is established for each cylinder. A four-stroke ten-cylinder V-type diesel engine is selected. The force analysis of a single cylinder is as follows: Figure 2 As shown, the single-cylinder excitation under rated operating conditions is as follows: Figure 3 As shown, the time-domain and frequency-domain vibrations of the ten-cylinder coupled overall excitation are as follows: Figure 4a and Figure 4bAs shown, the vibration amplitude is largest at the first dominant-coherent frequency in the frequency domain signal band of the engine model. Based on the test data of the motor bench, neglecting the electromagnetic and thermal effects of the motor's internal operation, the torque dynamic characteristics of the permanent magnet synchronous motor can be approximately equivalent to a first-order inertia model. The dynamic model of the motor is shown in the following equation: (twenty one) in The control command torque from motor A received from the upper-level energy management controller, simultaneously Let be the torque response time constant of motor A.

[0029] In step 2, based on the dynamic model, the inherent vibration characteristics of the system are analyzed, specifically as follows: The torsional vibration equation of a power transmission system can be written in matrix form as follows: (twenty two) in, and The stiffness matrix and damping matrix of the transmission system are represented by the following formula: (twenty three) (twenty four) (25) Input the torque of the transmission system to the engine module. and To input torsional torque to the motor, The drag torque acting on the vehicle body's inertia is given. Neglecting system damping, we obtain the differential equation for the system's undamped free vibration: (26) The free vibration response of a multi-degree-of-freedom system can be regarded as a superposition of multiple simple harmonic vibrations. The vibration of a certain harmonic can be expressed by the following formula. (27) The above formula can be simplified to obtain: (28) in It is the system's natural frequency. It is the mode shape of the system's relevant natural frequencies; The obtained system natural frequency modes are compared with the excitation modes to determine whether there is a risk of resonance between them.

[0030] Step 3 involves parameter sensitivity analysis and resonance avoidance, specifically: Derivation of the formula for the sensitivity of stiffness parameters to natural frequencies: (29) like Figure 5a and Figure 5b As shown, sensitivity analysis revealed that stiffness K 45 (Gear 4-5 connecting shaft) and K SCZ3 (Transmission-wheel connection shaft) has the highest sensitivity to low-order natural frequencies (11.4Hz, 18.8Hz); By adjusting K 45 and K SCZ3 The stiffness value effectively separates the system's sensitive natural frequency from the engine's main excitation frequency, fundamentally avoiding resonance during operation.

[0031] In step 4, the system dynamics model is solved based on the Runge-Kutta method, and stress verification is performed, specifically as follows: The Runge-Kutta method is a widely used high-precision single-step algorithm in engineering, extending Euler's approximation method to a more accurate approach for complex designs. Using the classic RK method, the calculation formula is as follows: (30) During the simulation, the simulation step size h is set to 5e-2. The Rk method is used to simulate and solve the constructed dynamic differential equation model to obtain the working state and working stress of the key components in the system. The reliability of the system is verified by stress check. The allowable stress of the sensitive shaft section in the transmission system is related to the geometric dimensions, operating speed and operating mode of the shaft section. The calculation formulas for the allowable stress of the shaft section under continuous operation and instantaneous operation modes are as follows; Continuous operation (31) Instantaneous operation (32) In the formula, To allow for continuous operation under torsional vibration stress, The instantaneous torsional vibration allowable stress is expressed in N / mm²; d is the diameter of the shaft section in mm; r is the ratio of the shaft section's operating speed to its rated speed. , The operating speed is expressed in r / min. The rated speed is 3800 r / min.

[0032] When the tensile strength of the shaft is higher than 410 N / mm 2 When the allowable stress τ' is reached, it can be calculated using the following formula: (33) In the formula This represents the minimum tensile strength of the shaft, expressed in units of... .

[0033] Under rated operating conditions (engine speed 3600 r / min), with a safety factor of 1.5, the steady-state torsional stress characteristics of the transmission system gear 4-gear 5 connecting shaft are as follows: Figure 6 As shown in the figure, the black curve represents the instantaneous allowable stress limit, the red curve represents the sustained allowable stress limit, and the blue curve reflects the additional stress response caused by the motor torque excitation. The analysis results show that under the condition of dual power source operation of the engine and motor, the steady-state torsional stress amplitude of this shaft segment is significantly lower than both the instantaneous and sustained allowable stress limits. This stress distribution characteristic confirms that, under rated operating conditions, the transmission system has sufficient torsional vibration stress margin, effectively avoiding the risk of overload failure of the shaft segment due to the superposition of dynamic loads.

[0034] The comparative analysis results of the torsional stress and allowable stress of the gear 4-gear 5 connecting shaft within the engine operating range are as follows: Figure 7 As shown, the torsional stress of the shaft section is lower than the instantaneous allowable stress and the continuous operating stress throughout the engine's entire operating range. This indicates that the geometric dimensions, stiffness, and damping parameters of the shaft section are reasonably configured, which can effectively prevent stress overload.

[0035] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0036] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, 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 the present invention.

Claims

1. A method for analyzing the vibration characteristics of a transmission system in a heavy-duty hybrid vehicle, characterized in that, include: Step 1: Establish a 17-DOF lumped parameter torsional vibration dynamic model of the powertrain system of a heavy-duty hybrid vehicle; Step 2: Analyze the inherent vibration characteristics of the system based on the dynamic model; Step 3: If the analysis shows that there is a risk of resonance between the system's natural frequency modes and the excitation modes, then perform parameter sensitivity analysis and resonance avoidance. Step 4: If the analysis shows that there is no risk of resonance between the system's natural frequency modes and excitation modes, then solve the system dynamics model based on the Runge-Kutta method and perform stress verification.

2. The method according to claim 1, characterized in that, In step 1, a 17-DOF lumped-parameter torsional vibration dynamic model of the heavy-duty hybrid vehicle's transmission system is established, specifically as follows: Step 101: Construct the transmission system topology; Step 102: Based on the lumped parameter method, the transmission system is simplified into a 17-DOF lumped parameter torsional vibration dynamic model, and the control equations characterizing the overall torsional vibration characteristics of the system are obtained based on the 17-DOF lumped parameter torsional vibration dynamic model. Step 103: Establish an engine torsional vibration model based on the state of each cylinder; Step 104: Establish the dynamic model of the motor.

3. The method according to claim 2, characterized in that, The transmission system topology specifically includes a fixed-axis gear transmission system, a coupling bus, a reduction bus system, and a speed change bus system, wherein the reduction bus system and the speed change bus system are symmetrical about the coupling bus.

4. The method according to claim 3, characterized in that, In step 2, based on the dynamic model, the inherent vibration characteristics of the system are analyzed, specifically as follows: Step 201: Rewrite the governing equations characterizing the overall torsional vibration properties of the system into matrix form; Step 202: Based on the rewritten matrix form, calculate the differential equation of the undamped free vibration of the system. Step 203: Rewrite the differential equation of the undamped free vibration of the system to obtain the equation related to the natural frequency of the system, and analyze the natural vibration characteristics of the system based on the equation. Step 204: Compare the obtained system natural frequency modes with the excitation modes to determine whether there is a risk of resonance between them.

5. The method according to claim 4, characterized in that, In step 202, based on the rewritten matrix form, the differential equation for the undamped free vibration of the system is calculated, specifically as follows: Obtain the governing equations representing the overall torsional vibration characteristics of the system, rewritten as matrices. Neglecting system damping, obtain the differential equations for the undamped free vibration of the system.

6. The method according to claim 5, characterized in that, Step 3 involves parameter sensitivity analysis and resonance avoidance, specifically: Step 301: Derive the formula for the sensitivity of stiffness parameters to natural frequency; Step 302: Perform sensitivity analysis based on the sensitivity formula to determine the component with the highest sensitivity to the natural frequency; Step 303: Adjust the stiffness value of the determined components to avoid resonance.

7. The method according to claim 6, characterized in that, In step 303, the stiffness value of the determined component is adjusted to avoid resonance, specifically as follows: Adjust the stiffness value of the determined components; Recalculate the system's natural frequency; Determine whether the system's natural frequency coincides with the excitation frequency. If they coincide, repeat step 3; otherwise, output the parameters and execute subsequent operations.

8. The method according to claim 7, characterized in that, In step 4, the system dynamics model is solved based on the Runge-Kutta method, and stress verification is performed, specifically as follows: The system dynamics model is solved using the Runge-Kutta method to obtain the working state and stress of key components in the system. The working stress is then checked to verify the reliability of the system.

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