Automatic Transmission Actuator Parameter Optimization Design Method Based on Sensitivity Analysis and Genetic Algorithm

Abstract

The present invention relates to a method for optimizing the parameters of an automatic transmission actuator based on sensitivity analysis and genetic algorithm, belonging to the technical field of construction machinery design. The method establishes a dynamic model of the automatic transmission actuator considering electro-mechanical-hydraulic characteristics, including the dynamic models of gear pumps, proportional solenoid valves and clutches; uses sensitivity analysis method to explore the influence degree of internal and external parameters on the pressure and efficiency of the hydraulic system, and determines the main optimization variables of the hydraulic system; designs a controller to track the pressure of the hydraulic system according to the required oil pressure of each solenoid valve and clutch in the shift control strategy; takes the shift shock degree and the sliding friction work of the friction pair as the optimization objectives, takes the shift time as the constraint condition, and uses genetic algorithm to optimize the main optimization variables of the hydraulic system within the allowable range of parameters, so as to complete the improvement of the shift quality and the forward optimization design of the automatic transmission actuator.

Description

Technical Field

[0001] The present invention belongs to the technical field of construction machinery design, and relates to a method for optimizing the parameters of an automatic transmission for a loader, specifically to a method for optimizing the design of the actuator parameters of an automatic transmission based on sensitivity analysis and genetic algorithm. Background Art

[0002] With the increasing maturity of the R & D and production technologies of construction machinery and the gradual expansion of application scenarios, the demand for high-end construction machinery equipment such as loaders has gradually increased. The hydraulic transmission is a key component of high-end mechanical equipment. Its design and optimization process can not only improve the performance and efficiency of the system, reduce the consumption of operating energy and production costs, but also improve the reliability and stability of the actuator, and reduce the impact degree and sliding friction work of the system. Therefore, the design and optimization links are the top priorities in the R & D and production processes of the whole vehicle, and at the same time provide a reference for the research and industrialization of loaders equipped with mechanical automatic transmissions or new energy loaders. Currently, common optimization design methods can be classified according to the perspective of optimization methods: experimental method, simulation method, intelligent optimization algorithm, etc. Among them, the experimental method generally completes the selection of the best combination of parameters by designing a suitable experimental scheme and measuring and analyzing the performance data after different parameter changes. Although the experimental method can intuitively and reliably select the optimal parameters, a large amount of time and resource costs are required for multiple experimental processes. The simulation method is committed to using professional software to build a physical or mathematical model of the system, and simulating and optimizing by continuously adjusting the model parameters. The simulation of the virtual model can reduce the cost consumption in the system design and experimental processes, but the manual parameter adjustment process makes its optimization efficiency low. The optimization method based on intelligent algorithms efficiently searches for the best parameters by setting the objective function and boundary conditions and combining advanced intelligent algorithms. However, the numerous control and design parameters and their coupling relationships affect its optimization effect. Therefore, it is necessary to comprehensively consider the dynamic response characteristics of the automatic transmission actuator, improve the existing optimization method based on intelligent algorithms, perform sensitivity analysis on the parameters to explore the main optimization variables, and finally realize the optimized design of the automatic transmission actuator parameters. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a method for optimizing the design of the actuator parameters of an automatic transmission based on sensitivity analysis and genetic algorithm. Through the analysis of the dynamic response characteristics and their influencing degrees of the design parameters and control parameters of the automatic transmission actuator, and combined with the search of the genetic algorithm under the set objective function and boundary conditions, the optimized design of the automatic transmission actuator for a loader is realized.

[0004] To achieve the above purpose, the present invention provides the following technical solutions:

[0005] An automatic transmission actuator parameter optimization design method based on sensitivity analysis and genetic algorithm, which establishes a dynamic model of the automatic transmission actuator considering the electro-mechanical-hydraulic characteristics, including the dynamic models of key components such as gear pumps, proportional solenoid valves, and clutches; analyzes the dynamic response characteristics of the automatic transmission hydraulic system and actuator under different design parameters and control parameters, uses sensitivity analysis method to explore the influence degree of internal and external parameters on the hydraulic system pressure and efficiency, and determines the main optimization variables of the hydraulic system; designs a controller to track the pressure of the hydraulic system according to the required oil pressure of each solenoid valve and clutch in the shift control strategy; takes the important quality shift shock degree and the sliding friction work of the friction pair in construction machinery as the optimization objectives, takes the shift time as the constraint condition, and uses intelligent algorithms such as genetic algorithm to optimize the main optimization variables of the hydraulic system within the allowable range of parameters, so as to complete the improvement of the shift quality and the positive optimization design of the automatic transmission actuator.

[0006] Furthermore, a dynamic model of the automatic transmission actuator considering the electro-mechanical-hydraulic characteristics is established, specifically including: under the action of the mechanical gear pump, the hydraulic oil is taken out from the oil sump and passes through the coarse filter and fine filter, and is distributed to each proportional solenoid valve according to the required oil pressure of each clutch in the shift control strategy; according to the physical parameters of the key components in the main oil circuit regulation subsystem and actuator, the dynamic simulation HCD model parameters are set.

[0007] The engagement process of the clutch can be divided into three stages, namely: the stage of eliminating the free clearance of the friction plate, the sliding friction stage, and the pressing stage; it can be analyzed that the piston assembly is affected by inertial force, hydraulic force, spring force, piston seal ring friction resistance and piston viscous friction resistance, and the dynamic equilibrium equation of the clutch piston assembly can be obtained as:

[0008]

[0009] In the formula, M L is the mass of the piston and one-third of the spring, kg; x L is the piston displacement, m; P L is the internal pressure of the clutch cylinder, Pa; d 1 is the outer diameter of the clutch, m; d 2 is the inner diameter of the clutch, m; K LS is the return spring stiffness, N / m; x Lo is the initial compression of the spring, m; α is the damping coefficient of the seal ring; b is the width of the seal ring, m; B Lc is the viscous damping coefficient, N·s / m;

[0010] When the clutch is separated and engaged, the oil cylinder is in the oil discharge and oil filling stages respectively. Considering the compressibility of the oil, the oil volume changes differently during oil filling and oil discharge, assuming no oil leakage; the flow rate Q during the oil filling stage and the oil discharge stageL In sequence:

[0011]

[0012] In the formula, C = d 2 / (32μl), where d is the diameter of the throttle orifice; μ is the viscosity of the oil; l is the length of the throttle orifice; A is the cross-sectional area of the flow passage of the throttle orifice, m 2 ; V L is the initial volume of the oil cylinder, m 3 ; S L is the piston acting area, m 2 ;

[0013] In the normal engagement state with the gear position fixed and during the gear shifting process, the torque transmitted by the clutch is different. The torques transmitted by the clutch under the two different working conditions are:

[0014]

[0015] In the formula, T c is the torque transmitted by the clutch, N·m; T load is the load torque, N·m, that is, the torque required for vehicle driving; the second formula is the torque transmitted during the clutch slip friction stage during the clutch gear shifting process. n is the number of friction pairs; r is the working radius of the friction plate, m; F LS is the spring force.

[0016] Furthermore, analyze the dynamic response characteristics of the automatic transmission hydraulic system and the actuator under different design parameters and control parameters, specifically including:

[0017] (1) Influence of the spring parameters of the proportional solenoid valve on the dynamic response characteristics of the hydraulic system pressure: The spring mainly plays a role in regulating the position of the valve core, thereby changing the valve port size, and finally obtaining the target pressure or target flow rate; considering that there are errors in the actual measurement data, analyze the spring stiffness k and the initial spring compression x o of the proportional solenoid valve in the hydraulic system on the dynamic response characteristics of the hydraulic system within a suitable range; as the spring stiffness increases, the pressure dynamic response and the stable value hardly change, but the response time of the oil pressure is significantly delayed; the influence of the initial spring compression on the pressure response is similar to that of the spring stiffness. As the initial spring compression increases, the spring force is greater, the pressure dynamic response and the stable value hardly change, but the response time of the oil pressure is significantly delayed. It can be seen that the influence of the initial spring compression on the oil pressure lag effect of the solenoid valve is more obvious than that of the spring stiffness;

[0018] (2) Influence of the spool mass of the proportional solenoid valve on the dynamic response characteristics of the hydraulic system pressure: The inertia of an object is related to its mass and affects the motion of the object. When the spool mass increases from 0.015 Kg to 0.035 Kg, the change in the dynamic response characteristics of the clutch control oil pressure is extremely small.

[0019] (3) Influence of the damping hole size on the dynamic response characteristics of the hydraulic system pressure: There are many damping holes in the physical object and schematic diagram of the automatic transmission hydraulic system. It can buffer and suppress the fluctuations of pressure and flow rate, and plays a crucial role in the stability and safety of the entire hydraulic system. Generally speaking, different damping hole sizes have a certain influence on the dynamic response characteristics of the shift oil pressure. As the diameter of the damping hole increases, the response of the system output pressure tends to become faster, and the larger the diameter, the weaker the trend of becoming faster, but the pressure fluctuation intensifies. The damping hole sizes at both ends of the solenoid valve mainly affect the response time during the stage of eliminating the free clearance of the friction plate, and the influence of the damping hole size at the right end is greater. At the same time, it will also cause pressure fluctuations during the clutch pressing stage; the damping hole size of the clutch actuator mainly affects the time during the clutch pressing stage.

[0020] (4) Influence of the piston outer diameter or piston acting area on the dynamic response characteristics of the hydraulic system pressure: Considering that the piston inner diameter is limited by the automatic transmission shaft, changing the piston acting area can only be achieved by changing the clutch outer diameter. Analyze the influence of the clutch piston acting area (piston outer diameter d p ) on the dynamic response characteristics of the hydraulic system within a reasonable range. As the clutch outer diameter increases, the oil chamber oil pressure becomes smaller and the pressure response speed slows down. This is mainly because when the clutch outer diameter increases, the volume of the oil cylinder acting chamber increases, and the time required to fill the oil chamber becomes longer, resulting in a slower pressure response.

[0021] (5) Influence of the clutch return spring on the dynamic response characteristics of the hydraulic system pressure: The pre-tightening force of the return spring includes the return spring stiffness k c and the initial compression amount x c which have a certain influence on the clutch dead stroke and slip friction stage. Analyze the influence of the return spring pre-tightening force on the dynamic response characteristics of the hydraulic system within a reasonable range; the greater the return spring stiffness and initial compression amount of the clutch return spring, the greater the corresponding return spring pre-tightening force, the more lagging the piston movement, and the slower the increase in the volume of the oil cylinder cavity. Therefore, the pressure value of the hydraulic oil in the oil chamber is larger. It can be seen that the return spring stiffness has a more significant influence on the piston hydraulic oil pressure boosting stage compared to the initial compression amount.

[0022] (6) Influence of the clutch piston mass on the dynamic response characteristics of the hydraulic system: Analyze the influence of the clutch piston mass m on the dynamic response characteristics of the hydraulic system within a reasonable range. The mass of the clutch piston has little influence on the dynamic characteristics of the hydraulic system because the inertial force of the piston is much smaller than the pre-tightening force of the clutch return spring. Therefore, the influence of the clutch piston mass on the pressure response of the hydraulic system can be ignored;

[0023] (7) Considering that the operating temperature of the automatic transmission hydraulic system is 60 - 90 °C, the temperature of the hydraulic oil has a very significant influence on the response time within the range of 40 - 60 °C. The higher the temperature, that is, the lower the viscosity, the faster the response time of the oil pressure step response, but the longer the step response time. Therefore, only considering the oil pressure response speed unilaterally, the oil temperature should be controlled at a lower level as much as possible.

[0024] Furthermore, use the sensitivity analysis method to explore the influence degree of internal and external parameters on the pressure and efficiency of the hydraulic system, and determine the main optimization variables of the hydraulic system, specifically including: Based on the sensitivity analysis method, normalize the selected eigenvectors, and explore the influence degree of the standardized internal and external parameters on the efficiency of the automatic transmission hydraulic system. The design parameters that have a significant influence on the efficiency of the hydraulic system are ranked in order of influence degree as follows: the stiffness of the clutch return spring, the damping hole at the right end of the solenoid valve, and the clutch acting area; and as the return spring and the spring pre-tightening force increase, that is, the spring stiffness and the initial compression amount increase, the smaller the clutch acting area, that is, the smaller the clutch outer diameter, and the smaller the damping hole size, the higher the efficiency of the hydraulic system.

[0025] Furthermore, use the genetic algorithm to optimize the main optimization variables of the hydraulic system within the allowable range of parameters, specifically including: Design a PID controller to track the pressure of the hydraulic system. The reference oil pressure for tracking is the change of the oil pressure under the actual vehicle shifting conditions. The output oil pressure of the clutch pressure regulating system basically fits the oil pressure of the clutch oil cavity collected under the actual shifting conditions;

[0026] Establish a vehicle dynamics model in the AMEsim software that reflects the shifting quality of the loader, which mainly consists of sub-models such as the engine power input module, the mechanical transmission system, the shifting clutch module, and the vehicle body and road surface module;

[0027] The smoothness and rapidity of the vehicle shifting process are a pair of contradictory attributes, and in practical applications, it is necessary to balance the two attributes by combining the evaluation criteria for the quality of shifting performance. The methods for evaluating the shifting quality mainly include the shifting shock degree J, the sliding friction work W of the friction pair, and the shifting time t;

[0028] The shift shock degree J is expressed as the derivative of the vehicle driving direction acceleration a. It can reflect the smoothness of the whole vehicle during the shifting process, and is not affected by factors such as road surface differences, sudden changes in working conditions, and driver operations. It can better and quantitatively evaluate the driving state of the vehicle and the torque fluctuation during the shifting process. Considering that the shifting process time is relatively short, on a good and flat road surface, it is approximately assumed that T d is a constant, and the shock degree is simplified to:

[0029]

[0030] In the formula, w d represents the driving wheel speed, w t represents the transmission output shaft speed, i 0 represents the transmission ratio of the drive axle, r is the driving wheel radius, J t represents the moment of inertia of the part connected to the transmission output shaft, and v represents the vehicle driving speed;

[0031] The sliding work W of the friction pair is the work done by the main and driven disk friction torques during the clutch sliding stage. During the shifting process, the sliding work generated by the engagement and disengagement of the clutch will be converted into heat energy. The rapid temperature rise of components such as the clutch friction plate deteriorates its operating environment and accelerates wear, thereby affecting the service life of the clutch, which is particularly obvious and crucial in the construction machinery field. Therefore, the sliding work can be regarded as an evaluation index for the life of the friction components. The value of the sliding work should be as small as possible, and the longer the life of the shifting execution components. However, there is a certain degree of contradictory relationship between the sliding work and the shock degree. Therefore, it needs to be adjusted through control methods to ensure that both are within a reasonable range.

[0032] The shifting time t is the time elapsed from the issuance of the shifting signal to the stabilization of the new gear, which can represent the rapidity of shifting. Its value has different degrees of influence on various vehicle performances (such as power performance, smoothness, etc.) and component characteristics (such as the torque transmission characteristics and service life of the clutch).

[0033] In order to unify the shifting smoothness and rapidity, the sliding work W of the friction pair and the shock degree J are set as the optimization objectives; the shifting time t is set as the constraint condition; for the optimization of the multi-objective function, the linear weighted method can be used to construct the objective function. However, the sliding work of the friction pair and the shock degree are two quantities with different natures and there are differences in the order of magnitude. It is necessary to normalize the objective function. The normalized objective function is:

[0034]

[0035] In the formula, W is the current sliding work of the clutch, and W 0 is the final sliding work of the clutch; J is the current shock degree, and J 0is the maximum impact degree; ω is the weighting coefficient; considering that the research object is a loader and there is a phenomenon of clutch friction plate ablation, ω is taken as 0.8.

[0036] Take the three parameters with significant influence on the dynamic response characteristics, namely the pre-tightening force of the clutch return spring, the damping hole at the right end of the solenoid valve, and the clutch acting area (outer diameter), as optimization variables and set the optimization range; the target parameter value changes with the increase of the evolutionary generation, and basically tends to be stable after the evolutionary generation is greater than 500.

[0037] The beneficial effects of the present invention are as follows:

[0038] (1) The present invention takes the actuator of the automatic transmission for loaders as the research object, analyzes the dynamic response characteristics of the actuator pressure and efficiency under different design parameters and control parameters based on the dynamic model of the automatic transmission actuator considering the electro-mechanical-hydraulic characteristics, and determines the key optimization variables of the actuator based on the sensitivity analysis method to compare the influence degree of each parameter.

[0039] (2) The present invention designs a PID controller to track the collected value of the oil pressure in the clutch oil chamber under the actual shifting condition, based on the vehicle dynamics model including sub-modules such as the engine input module, the mechanical transmission and shifting clutch module, and the vehicle body and road surface module. Considering the actual working characteristics of construction machinery, taking the sliding friction work and impact degree of the friction pair as the multi-objective optimization function, taking the shifting time setting as the constraint condition, taking the parameters with significant influence on the dynamic response characteristics as the optimization variables, and using the genetic algorithm to search for the best parameters within a reasonable range to realize the improvement of the shifting quality of the automatic transmission actuator and the positive optimization design.

[0040] Other advantages, objectives and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following specification. Description of the Drawings

[0041] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0042] Figure 1 is the flow chart of the parameter optimization method for the automatic transmission actuator provided by the present invention;

[0043] Figure 2 is the dynamic response characteristic of an automatic transmission actuator provided by an embodiment of the present invention;

[0044] Figure 3The degree of influence of the parameters of an automatic transmission hydraulic system on its performance provided by an embodiment of the present invention based on sensitivity analysis method;

[0045] Figure 4 A vehicle dynamics model provided by an embodiment of the present invention that can reflect the shifting quality of construction machinery. Detailed implementation manners

[0046] The following specific examples illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0047] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation to the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, which do not represent the dimensions of the actual products; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0048] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and should not be construed as a limitation to the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0049] Please refer to Figures 1 to 4 , the present invention provides an optimization design method for the parameters of an automatic transmission actuator based on sensitivity analysis and genetic algorithm, as Figure 1As shown, a dynamic model of the automatic transmission actuator considering the electro-mechanical-hydraulic characteristics is established, mainly including the dynamic models of key components such as gear pumps, proportional solenoid valves, and clutches. Among them, under the action of the mechanical gear pump, hydraulic oil is taken out from the oil sump and passes through the coarse filter and fine filter, and is distributed to the corresponding proportional solenoid valves according to the required oil pressure of each clutch in the shift control strategy. Considering that this hydraulic system is a full-flow direct-acting control, it directly flows into the clutches in each gear. According to the analysis of the dynamic response characteristics of the hydraulic system pressure and efficiency under different design parameters and control parameters, the main optimization variables with significant influence are determined. Taking the shift quality as the optimization goal and boundary conditions, an intelligent algorithm is used to improve the shift quality of the automatic transmission actuator and complete the forward optimization design.

[0050] 1. Construction of the dynamic model of the automatic transmission actuator considering the electro-mechanical-hydraulic characteristics and analysis of its dynamic response characteristics

[0051] (1) Based on the working principle and structure diagram of the main oil circuit regulation subsystem and the actuator, a dynamic simulation model of the automatic transmission actuator considering the electro-mechanical-hydraulic characteristics and including key components such as gear pumps, proportional solenoid valves, and clutches is established by AMEsim. Under the action of the mechanical gear pump, hydraulic oil is taken out from the oil sump and passes through the coarse filter and fine filter, and is distributed to each proportional solenoid valve according to the required oil pressure of each clutch in the shift control strategy. According to the physical parameters of the key components in the main oil circuit regulation subsystem and the actuator, the dynamic simulation HCD model parameters are set.

[0052] The engagement process of the clutch can be divided into three stages, namely: the stage of eliminating the free clearance of the friction plate, the slip friction stage, and the pressing stage. Through analysis, it can be seen that the piston assembly is affected by inertial force, hydrodynamic force, spring force, piston seal ring friction resistance, and piston viscous friction resistance. The dynamic equilibrium equation of the clutch piston assembly can be obtained as follows:

[0053]

[0054] In the formula, M L is the mass of the piston and one-third of the spring, kg; x L is the piston displacement, m; P L is the internal pressure of the clutch cylinder, Pa; d 1 is the outer diameter of the clutch, m; d 2 is the inner diameter of the clutch, m; K LS is the stiffness of the return spring, N / m; x Lo is the initial compression of the spring, m; α is the damping coefficient of the seal ring; b is the width of the seal ring, m; B Lc is the viscous damping coefficient, N·s / m.

[0055] When the clutch is disengaged and engaged, the oil cylinder is in the oil draining and oil filling stages respectively. Considering the compressibility of the oil, different changes in the oil volume occur during oil filling and draining, assuming no oil leakage. The flow rates during the oil filling stage and the oil draining stage are as follows:

[0056]

[0057] In the formula, C = d 2 / (32μl), where d is the diameter of the throttle orifice; μ is the viscosity of the oil; l is the length of the throttle orifice;; A is the cross-sectional area of the throttle orifice, m 2 ; V L is the initial volume of the oil cylinder, m 3 ; S L is the piston acting area, m 2 .

[0058] In the normal engagement state with a fixed gear position and during the gear shifting process, the torque transmitted by the clutch is different. The torque transmitted by the clutch under two different working conditions is as follows:

[0059]

[0060] In the formula, T c is the torque transmitted by the clutch, N·m; T load is the load torque, N·m, that is, the torque required for vehicle driving; the second formula is the torque transmitted during the clutch slip friction stage during the clutch gear shifting process, n is the number of friction pairs; r is the working radius of the friction plate, m; F LS is the spring force.

[0061] (2) The parameters affecting the dynamic response characteristics of the automatic transmission hydraulic system are mainly divided into two categories. One is the internal parameters designed by humans such as spring stiffness, initial spring compression, spool mass, and damping orifice diameter, and the other is the external factors that change with the working conditions such as hydraulic oil temperature and viscosity. Studying different design parameters and control parameters for the dynamic response characteristics of the automatic transmission hydraulic system, as Figure 2 shown, provides a reference for the optimal design of the hydraulic system components and the control of pressure and flow. The analysis results of the dynamic response characteristics are as follows:

[0062] ① The influence of the spring parameters of the proportional solenoid valve on the dynamic response characteristics of the hydraulic system pressure: The spring mainly plays a role in regulating the spool position, thereby changing the valve port size, and finally obtaining the target pressure or target flow. Considering the errors in actual measurement data, within a suitable range, the spring stiffness k and the initial spring compression x of the proportional solenoid valve in the hydraulic system are analyzed respectively oInfluence on the dynamic response characteristics of the hydraulic system. As the spring stiffness increases, the pressure dynamic response and the stable value hardly change, but the response time of the oil pressure is significantly lagged. The influence of the initial compression of the spring on the pressure response is similar to that of the spring stiffness. As the initial compression of the spring increases, the spring force becomes greater, the pressure dynamic response and the stable value hardly change, but the response time of the oil pressure is significantly lagged. It can be seen that the influence of the initial compression of the spring on the oil pressure lag of the solenoid valve is more obvious than that of the spring stiffness.

[0063] ② Influence of the spool mass of the proportional solenoid valve on the pressure dynamic response characteristics of the hydraulic system: The inertia of an object is related to its mass and affects the motion of the object. When the spool mass increases from 0.015 Kg to 0.035 Kg, the change in the dynamic response characteristics of the clutch control oil pressure is extremely small.

[0064] ③ Influence of the damping orifice size on the pressure dynamic response characteristics of the hydraulic system: There are many damping orifices in the physical object and the schematic diagram of the automatic transmission hydraulic system. It can buffer and suppress the fluctuations of pressure and flow rate, and plays a crucial role in the stability and safety of the entire hydraulic system. Generally speaking, different damping orifice sizes have a certain influence on the dynamic response characteristics of the shift oil pressure. As the diameter of the damping orifice increases, the response of the system output pressure tends to become faster, and the larger the diameter, the weaker the tendency to become faster, but the pressure fluctuation intensifies. The damping orifice sizes at both ends of the solenoid valve mainly affect the response time during the stage of eliminating the free clearance of the friction plate, and the influence of the damping orifice size at the right end is greater. At the same time, it will also cause pressure fluctuations during the clutch pressing stage; the damping orifice size of the clutch actuator mainly affects the time during the clutch pressing stage.

[0065] ④ Influence of the piston outer diameter / piston acting area on the pressure dynamic response characteristics of the hydraulic system: Considering that the piston inner diameter is limited by the automatic transmission shaft, changing the piston acting area can only be achieved by changing the clutch outer diameter. Analyze the influence of the clutch piston acting area (piston outer diameter d p ) on the dynamic response characteristics of the hydraulic system within a reasonable range. As the clutch outer diameter increases, the oil chamber oil pressure becomes smaller and the pressure response speed slows down. This is mainly because when the clutch outer diameter increases, the volume of the oil cylinder acting chamber increases, the time required to fill the oil chamber becomes longer, and the pressure response also slows down accordingly.

[0066] ⑤ Influence of the clutch return spring on the pressure dynamic response characteristics of the hydraulic system: The pre-tightening force of the return spring (return spring stiffness k c and the initial compression x c) It has a certain impact on the clutch free travel and the slip friction stage. Analyze the influence of the return spring preload force on the dynamic response characteristics of the hydraulic system within a reasonable range. The greater the stiffness and the initial compression of the clutch return spring, the greater the corresponding return spring preload force, the more lagging the piston movement, and the slower the increase in the volume of the oil cylinder cavity. Therefore, the pressure value of the hydraulic oil in the oil chamber is relatively large. It can be seen that the return spring stiffness has a more significant impact on the piston hydraulic oil pressure rising stage compared to the initial compression.

[0067] ⑥ Influence of the clutch piston mass on the dynamic response characteristics of the hydraulic system pressure: Analyze the influence of the clutch piston mass m on the dynamic response characteristics of the hydraulic system within a reasonable range. The clutch piston mass has little impact on the dynamic characteristics of the hydraulic system because the inertial force of the piston is very small compared to the preload force of the clutch return spring. Therefore, the influence of the clutch piston mass on the hydraulic system pressure response can be ignored.

[0068] ⑦ Considering that the operating temperature of the automatic transmission hydraulic system is 60 - 90 °C, the influence of the hydraulic oil temperature in the range of 40 - 60 °C on the response time is very significant. The higher the temperature, that is, the lower the viscosity, the faster the response time of the oil pressure step response, but the longer the step response time. Therefore, only considering the oil pressure response speed unilaterally, the oil temperature should be controlled at a relatively low level as much as possible.

[0069] (3) Considering the differences in the selection of the parameter characteristic range, based on the sensitivity analysis method, normalize the selected eigenvectors, and explore the influence degree of the standardized internal and external parameters on the efficiency of the automatic transmission hydraulic system as Figure 3 shown. The design parameters that have a significant impact on the efficiency of the hydraulic system are ranked in order of influence degree as follows: the stiffness of the clutch return spring, the damping hole at the right end of the solenoid valve, and the clutch acting area. And as the return spring and the spring preload force increase (the increase in spring stiffness and initial compression), the clutch acting area becomes smaller (the smaller the clutch outer diameter), and the damping hole size becomes smaller, the higher the efficiency of the hydraulic system.

[0070] Normalization formula:

[0071]

[0072] 2. Parameter optimization design of the automatic transmission actuator based on genetic algorithm

[0073] Design a PID controller to track the pressure of the hydraulic system. The reference oil pressure for tracking is the change in oil pressure under the actual vehicle shifting conditions. The output oil pressure of the clutch pressure regulation system basically fits the oil pressure in the clutch oil chamber collected under the actual shifting conditions.

[0074] In the AMEsim software, establish as Figure 4The vehicle dynamics model for the shift quality of the shown reaction loader is mainly composed of sub-models such as the engine power input module 1, the mechanical transmission system 3, the shift clutch module 2, and the vehicle body and road surface module 4.

[0075] The smoothness and rapidity of the vehicle shifting process are a pair of contradictory attributes. In practical applications, it is necessary to balance the two attributes by combining the evaluation criteria for the quality of shifting. The methods for evaluating shift quality mainly include the shift shock degree J, the sliding friction work W of the friction pair, and the shift time t.

[0076] The shift shock degree J is expressed as the derivative of the vehicle driving direction acceleration a. It can represent the smoothness of the whole vehicle during the shifting process and is not affected by factors such as road surface differences, sudden changes in working conditions, and driver operations. It can better and quantitatively evaluate the driving state of the vehicle and the torque fluctuation during the shifting process. Considering that the shifting process time is relatively short, on a good flat road surface, it is approximately assumed that T d is a constant, and the shock degree is simplified as:

[0077]

[0078] In the formula, w d represents the driving wheel speed, w t represents the transmission output shaft speed, i 0 represents the transmission ratio of the drive axle, r is the driving wheel radius, J t represents the moment of inertia of the part connected to the transmission output shaft, and v represents the vehicle driving speed.

[0079] The sliding friction work W of the friction pair is the work done by the main and driven disk friction torques during the clutch sliding friction stage. During the shifting process, the sliding friction work generated by the engagement and separation of the clutch will be converted into heat energy. The rapid temperature rise of components such as the clutch friction plate leads to the deterioration of its operating environment and accelerated wear, which in turn affects the service life of the clutch, especially obvious and crucial in the field of construction machinery. Therefore, the sliding friction work can be regarded as an evaluation index for the life of the friction components. The value of the sliding friction work should be as small as possible, and the longer the life of the shift execution components. However, there is a certain degree of contradictory relationship between the sliding friction work and the shock degree. Therefore, it needs to be adjusted by control methods to ensure that both are within a reasonable range.

[0080] The shift time t is the time experienced from the issuance of the shift signal to the stabilization of the new gear, which can represent the rapidity of shifting. Its value has different degrees of influence on various vehicle performances (such as power performance, smoothness, etc.) and component characteristics (such as the torque transmission characteristics and service life of the clutch).

[0081] In order to unify the shift smoothness and rapidity, the sliding work W and the jerk J of the friction pair are set as the optimization objectives; the shift time t is set as the constraint condition. For the optimization of the multi-objective function, the linear weighted method can be used to construct the objective function. However, the sliding work and the jerk of the friction pair are two quantities with different natures and there are differences in the order of magnitude, so the objective function needs to be normalized. The normalized objective function is:

[0082]

[0083] In the formula, W is the current sliding work of the clutch, and W 0 is the final sliding work of the clutch; J is the current jerk, and J 0 is the maximum jerk; ω is the weighting coefficient. Considering that the research object is a loader and there is a phenomenon of clutch friction plate ablation, ω is taken as 0.8.

[0084] The three parameters with significant influence on the dynamic response characteristics, namely the pre-tightening force of the clutch return spring, the damping hole at the right end of the solenoid valve, and the clutch acting area (outer diameter), are used as the optimization variables and the optimization ranges are set. The target parameter values change with the increase of the number of evolutionary generations, and basically tend to be stable after the number of evolutionary generations is greater than 500.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for optimizing the parameters of an automatic transmission actuator based on sensitivity analysis and genetic algorithm, characterized in that: Establish a dynamic model of the automatic transmission actuator considering the electromechanical and hydraulic characteristics, including the dynamic models of the gear pump, proportional solenoid valve and clutch; analyze the dynamic response characteristics of the automatic transmission hydraulic system and actuator under different design parameters and control parameters, use the sensitivity analysis method to explore the influence of internal and external parameters on the pressure and efficiency of the hydraulic system, and determine the main optimization variables of the hydraulic system; design a controller to track the pressure of the hydraulic system according to the required oil pressure of each solenoid valve and clutch in the shift control strategy; take the shift shock degree and the sliding friction work of the friction pair as the optimization goals, and take the shift time as the constraint condition, use the genetic algorithm to optimize the main optimization variables of the hydraulic system within the range allowed by the parameters, and complete the shift quality improvement and forward optimization design of the automatic transmission actuator; The dynamic model of the automatic transmission actuator considering the electromechanical and hydraulic characteristics is established, including: the hydraulic oil is taken out from the oil pool under the action of the mechanical gear pump and passes through the coarse filter and the fine filter, and is distributed to each proportional solenoid valve according to the required oil pressure of each clutch in the shift control strategy; according to the physical parameters of the main oil circuit regulation subsystem and the key components in the actuator, the dynamic simulation HCD model parameters are set; The clutch engagement process is divided into three stages, namely, the friction plate free clearance elimination stage, the sliding friction stage and the pressing stage. It is known from the analysis that the piston assembly is affected by inertia force, fluid force, spring force, piston sealing ring friction resistance and piston viscous friction resistance, and the dynamic equilibrium equation of the clutch piston assembly is: In the formula, M L is the mass of the piston and one-third of the spring; P L is the internal pressure of the clutch cylinder; d 1 is the outer diameter of the clutch; d 2 is the inner diameter of the clutch; K LS is the return spring stiffness; x L is the piston displacement; x Lo is the initial compression of the spring; is the damping coefficient of the sealing ring; b is the sealing ring width; B Lc is the viscous damping coefficient; When the clutch is disengaged and engaged, the cylinder is in the oil discharge and oil filling stages respectively. Considering the compressibility of the oil, the oil volume changes differently during oil filling and oil discharge. Assuming there is no oil leakage, the flow rate during the oil filling and oil discharge stages is They are: In the formula, ,in d is the throttle hole diameter; is the viscosity of the oil; l is the length of the throttle hole; A is the area of ​​the flow cross section of the throttle hole; V L is the initial volume of the oil cylinder; S L is the piston action area; The torque transmitted by the clutch is different in the normal engagement state with the gear fixed and during the gear shifting process. The torque transmitted by the clutch under the two different working conditions is: In the formula, T c Transmits torque to the clutch; T load is the load torque, i.e. the torque required for vehicle driving; the second formula is the torque transmitted by the clutch during the clutch slipping stage during the clutch shifting process. n is the number of friction pairs; r is the working radius of the friction plate; is the spring force.

2. The automatic transmission actuator parameter optimization design method according to claim 1, characterized in that: Analyze the dynamic response characteristics of the automatic transmission hydraulic system and actuator under different design parameters and control parameters, including: (1) The influence of the spring parameters of the proportional solenoid valve on the dynamic response characteristics of the hydraulic system pressure: The spring plays a role in adjusting the valve core position, thereby changing the valve port size and ultimately obtaining the target pressure or target flow. Considering the error in the actual measurement data, the spring stiffness of the proportional solenoid valve in the hydraulic system is analyzed within a suitable range. k and the initial compression of the spring x o Impact on the dynamic response characteristics of the hydraulic system; the initial compression of the spring has a more obvious effect on the oil pressure hysteresis of the solenoid valve than the spring stiffness; (2) The influence of the valve core mass of the proportional solenoid valve on the dynamic response characteristics of the hydraulic system pressure: The inertia of an object is related to its mass and has an impact on the movement of the object; when the valve core mass increases from 0.015Kg to 0.035Kg, the dynamic response characteristics of the clutch control oil pressure change very little; (3) The influence of damping hole size on the dynamic response characteristics of hydraulic system pressure: The damping hole size at both ends of the solenoid valve affects the response time of the friction plate free gap elimination stage, and the damping hole size at the right end has a greater impact, and it will also cause pressure fluctuations in the clutch clamping stage; the damping hole size of the clutch actuator affects the time of the clutch clamping stage; (4) The influence of piston outer diameter or piston action area on the dynamic response characteristics of hydraulic system pressure: As the outer diameter of the clutch increases, the oil pressure in the oil chamber decreases, and the pressure response speed slows down; (5) The influence of clutch return spring on the dynamic response characteristics of hydraulic system pressure: The return spring preload includes the return spring stiffness. k c and initial compression x c It has an impact on the clutch idle stroke and slipping stage. The impact of the return spring preload on the dynamic response characteristics of the hydraulic system is analyzed within a reasonable range. The return spring stiffness has a more significant impact on the piston hydraulic oil pressure increase stage relative to the initial compression. (6) The influence of clutch piston mass on the dynamic response characteristics of hydraulic system pressure: The influence of clutch piston mass on the pressure response of hydraulic system can be ignored. (7) Considering that the operating temperature of the automatic transmission hydraulic system is 60~90℃, the hydraulic oil temperature in the range of 40~60℃ has a significant impact on the response time. The higher the temperature, that is, the lower the viscosity, the faster the response time of the oil pressure step response, but the longer the step response time. Therefore, considering only the oil pressure response speed, the oil temperature should be controlled at a low level as much as possible.

3. The automatic transmission actuator parameter optimization design method according to claim 2, characterized in that: The sensitivity analysis method is used to explore the influence of internal and external parameters on the pressure and efficiency of the hydraulic system, and to determine the main optimization variables of the hydraulic system, including: based on the sensitivity analysis method, the selected characteristic vectors are normalized, and the influence of the standardized internal and external parameters on the efficiency of the automatic transmission hydraulic system is explored. The design parameters that have a significant impact on the efficiency of the hydraulic system are ranked in order of influence: clutch return spring stiffness, damping hole at the right end of the solenoid valve and clutch effective area; and with the increase of the return spring and spring preload, that is, the increase of the spring stiffness and the initial compression, the smaller the clutch effective area, that is, the smaller the clutch outer diameter, the smaller the damping hole size, and the higher the efficiency of the hydraulic system.

4. The automatic transmission actuator parameter optimization design method according to claim 1, characterized in that: Genetic algorithms are used to optimize the main optimization variables of the hydraulic system within the range allowed by parameters, including: designing a PID controller to track the pressure of the hydraulic system. The reference oil pressure tracked is the change of oil pressure under the actual vehicle shifting condition. The output oil pressure of the clutch pressure regulation system is basically fitted with the clutch oil chamber oil pressure collected under the actual shifting condition. A vehicle dynamics model that reflects the shifting quality of the loader is established in AMEsim software, including the engine power input module, the mechanical transmission system and shift clutch module, and the vehicle body and road surface module; Methods for evaluating shift quality include shift shock J , Sliding friction work of friction pair W and shift time t ; Gear shift shock J Acceleration in the direction of vehicle travel a The derivative of can express the smoothness of the whole vehicle during the shifting process, and is not affected by road surface differences, sudden changes in working conditions, and driver manipulation. It can quantitatively evaluate the driving state of the vehicle and the fluctuation of torque during the shifting process. Considering the short time of the shifting process, it is approximately assumed on a good flat road surface that T d is a constant, the impact degree is simplified to: In the formula, w d represents the driving wheel speed, w t represents the transmission output shaft speed, i 0 represents the transmission ratio of the drive axle, r is the driving wheel radius, Indicates the moment of inertia of the part connected to the transmission output shaft, v Indicates the vehicle's speed; In order to unify the smoothness and speed of gear shifting, the sliding friction work of the friction pair is W And the impact J Set as optimization target; shift time t Set as constraint conditions; for the optimization of multi-objective functions, the linear weighted method is used to construct the objective function. However, the sliding work and impact degree of the friction pair are two quantities of different properties and have different orders of magnitude. The objective function needs to be normalized. The normalized objective function is: In the formula, W is the current slipping work of the clutch, W 0 is the final sliding friction work of the clutch; J is the current impact degree, J 0 is the maximum impact degree; is the weighting coefficient; The three parameters with significant influence on the dynamic response characteristics, namely the clutch return spring preload, the damping hole at the right end of the solenoid valve and the clutch action area, are taken as optimization variables and the optimization range is set; the target parameter value changes with the increase of the evolutionary generation, and the parameter value basically tends to be stable after the evolutionary generation is greater than 500.

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