The Simulation Study And Optimization Design For Heavy Duty Truck Dynamics Performance

Highway transport is important way for transportation today and heavy truck is the primary facility. To satisfy the requirement of heavy truck for continuously run with highspeed and heavy loading,the performance such as ride comfort and handleability and stability performance must be improved. It is demanded that the dynamical performance of vehicle should be hold comprehensively at the stage of design. The analysis and optimizing for dynamical performance of whole vehicle with simulation method is the necessary means to improve the performance of vehicle and reduce the period of research.Focus on high quality heavy tractor of FAW, this paper researches its dynamical performance with dynamics theory and simulation method. The key structure form and important parameter, which influence the dynamical performance of heavy truck, are confirmed basically and will support for the research and design of heavy truck. Due to the area of dynamics for heavy truck is abroad, the ride comfort and the handleability and stability performance are only studied emphatically in this paper. Based on discussing the modeling method of suspension, tire, powertrain mount system and cab mount system, the dynamical model of whole vehicle is built and the simulation is performed for the model. The main content include: The basic knowledge of multibody dynamics is introduced in this paper. Combined with ADAMS software the modeling theory of elastic body worked in the multibody model is discussed.In this paper,the complete vehicle dynamic simulation model for a heavy truck is created with MSC.ADAMS/Car.For those elastic body,the modal data is extracted from FEM and assembled together.Aimed at the difficult problem in modeling of dynamics simulation for heavy truck, modeling of leaf spring, research work is developed. Because the size of heavy truck leaf spring is large and some uncontroled nonlinearity friction consists between leaf pieces, traditional model of leaf spring is difficult to deal with the contradiction between the performance of kinematics and dynamics. Using the equivalent theory of three-link model, the paper creates the model of leaf spring with grade stiffness and so on for the first time and confirmed the parameter of model with experiment. Compared with the result of Finite Element model and experiment, the performance of kinematics and dynamics of model is verified. It is concluded that three-link model can simulate the leaf spring of heavy truck primely and can reduce the degree of freedom of model greatly. It is convenient to simulate the dynamical performance of whole vehicle.The model of tire is the key part in creating the dynamics model of whole vehicle. To describe the complex nonlinear dynamics performance of tire, and to be satisfied with the study of the ride comfort and the handleability and stability performance, the Ftire model of tire which is popularity international recently years is studied in the paper. By identifying the modal parameter of tire with Finite Element simulation and experiment, the Ftire model of meridional tire using for heavy truck is built for the first time, and the validity of model is verified. It provides the reliable condition for buiding model of whole vehicle and carrying simulation exactly. Otherwise, the Ftire model of tire building in the paper can complete the contact trace analysis of tire for static and dynamic statement. It provides an easy way to study and solve the problem of wear and tear of tire.Based on the design of engineering, the multibody dynamics model for powertrain mount system of the heavy vehicle is built in the paper, and is optimized roundly. At first, the explicit optimization is carried out for the parameter such as stiffness and damping coefficient of mount part in iSIGHT software with multi-land genetic algorithms method,which gives the best answer for multi-object optimized problem including mode decoupled and so on. Secondly, aimed at the characteristic that the value of mount parameter is discrete seriously at practice process, the effect of mount stiffness to the target is studied with Monte Carlo simulation and Design of Experiment method while the stiffness is discrete seriously. The robustness optimization is carried out with 6σprobability optimization method. The sensibility analysis is carried out for the optimization result and is verified with modal experiment of vehicle. All kinds of optimization arithmetic used in the paper is integrated and software platform is built for automatic solution. By integrating the software ADAMS,iSIGHT and Matlab availably in optimization process, the optimization workflow of powertrain mount system is run automatically, and the process of optimization and matching for mount system design is performed smoothly. The research result shows that the explicit optimization method can ensure the requirement of vibration isolation and life of mount part only in the condition of good product quality, but the decoupled grade of system is decreased while the stiffness of mount is varied in the production. The effect of isolating vibration is lower. But by the robustness design, the parameter such as modal frequency and decoupled grade of system varies a little while stiffness of mount waves. The reliability of system is improved in great degree. Using ADAMS/View the multi-rigid-body model of cab mount system is built for the heavy truck. The mode of the cab Finite Element model is extracted with Nastran software, and the rigid-elastic coupled model of the cab mount system is built. Compareing the simulation result and test data of two model, it is verified that the precision of rigid-elastic coupled model is better. Then the best level of each factor that affects the comfort performance is achieved using Design of Experiment method, in which it makes the spring stiffness of mount system and absorber damping coefficient as design factor and perpendicular acceleration at the center of gravity as output for cab rigid-elastic coupled model. At last, using the experiment signal as input of the system, the fatigue life of cab rigid-elastic coupled model and the sensitivity for the load and material performance is analysed. The most sensible factor for fatigue life is confirmed and provides the foundation for the improving design.Based on the assembly models built forward, the dynamics model of whole vehicle for heavy truck is built with templet. Compareing the simulation result with experiment data for the ride comfort and the handleability and stability performance, the validity of the whole vehicle model is verified. The estimated experiment of ride comfort performance is tested on the impulse road and the random road. The degree of understeer and roll of body is tested in steady turning experiment as the estimate guideline for the handleability and stability performance. At last, the effect of the factor such as the stiffness of front leaf spring, the damping coefficient of suspension absorber to the ride comfort and the handleability and stability performance of the heavy truck is studied with Design of Experiment method.The factor which influenced greatly is confirmed, and it gives the design condition for optimizing the stiffness and damping parameter of suspension. The design method based on the simulation and optimization of dynamical performance for a series of assembly that is put forward in this paper is used for new heavy truck internal for the first time. According to the using status after the product sells, the ride comfort and the handleability and stability performance of the heavy truck arrives the primary object. It is leader among the similar products internal and is satisfied with the customers greatly.