Research On Dissipation Of Energy Approach For Vehicle Plane Motion System Dynamics Analysis

With the development of intelligent vehicle technology,the improvement of vehicle handling performance and the increase in the complexity of the traffic environment,the situation that the vehicle needs to deal with to ensure its own safety is also more complicated.This brings new opportunities and challenges to the research in the field of vehicle dynamics.However,the current research on the dynamics of the vehicle plane motion system is often carried out in the stable region,and it is necessary to pay attention to the unstable region.Moreover,the existing methods also face limitations such as difficulty in characterizing the differences between state points within a region,and weak generalization ability for vehicle systems with high degrees of freedom(≥3).Thus,it has broad application prospects to carry out research on the global(stable region and unstable region)characteristics of vehicle dynamics and explore new methods that can reveal the global characteristics of the vehicle.Therefore,after in-depth analysis of the relevant research findings in the field of vehicle dynamics,this paper proposes a quantitative method of dissipation of energy for the analysis of the global characteristics of vehicle plane motion system dynamics.The research steps are as follows: propose a new method “dissipation of energy”、analyze the effectiveness of the new method by comparing classical methods、apply the new method to analyze the vehicle dynamics characteristics,solve the problem、verify the conclusion.First of all,a quantitative indicator “dissipation of energy” for global vehicle dynamics analysis is proposed.The phase trajectory characteristics of vehicle models with two,three and five degrees of freedom are analyzed,and a quantitative analysis method of vehicle dynamics based on dissipation of energy is proposed for the first time for the energy dissipation characteristics of vehicle systems.Based on the vehicle model,the corresponding dissipation of energy calculation formula is deduced and verified.The energy layering phenomenon in the global state space of the vehicle is revealed,and a method for solving the stable region based on the dissipation of energy gradient is proposed.By analyzing the dissipation of energy in different time periods,the convergence characteristics of the system with time evolution are explained,and the function-energy component relationship of the vehicle plane motion system is calculated.It shows that this method meets the needs of quantitative analysis of the global characteristics of vehicle dynamics.Secondly,the dissipation of energy is compared with the classical quantitative method and its effectiveness is proved.For the first time,quantitative methods are applied to reveal the global characteristics of the vehicle plane motion system and the dissipation of energy is compared with four quantitative indicators,Lyapunov exponent,longitudinal velocity difference,sideslip angle and convergence time.In the comparison,from the aspects of phase trajectory convergence and vehicle performance,the advantages and disadvantages of each quantitative indicator in revealing the global characteristics of the vehicle plane motion system are discussed,and the relevant quantitative analysis methods and theories are improved.It shows that the dissipation of energy can reflect the overall convergence rate of the phase trajectory in the stable region to a certain extent,and can also be used to evaluate the stability in the sense of vehicle performance.The paper also demonstrated the advantages of quantitative methods in revealing the global characteristics of vehicle system dynamics and the effectiveness of dissipation of energy method in the analysis of vehicle plane motion systems.Thirdly,based on the dissipation of energy method,an analysis of the vehicle system dynamics is carried out.Firstly,the influence of system elements on the global dynamic characteristics is analyzed,that is,the influence of transverse and longitudinal coupling of tire force,driving mode and driving torque on the global characteristics of the system.It is explained that the system elements not only have an impact on the size and shape of the stable region of the vehicle system,but also have a very significant impact on the dynamic characteristics inside the vehicle unstable region,such as the position and shape of the strip-like region.Then,the nonlinear mapping relationship between the tire force characteristics and the vehicle stable region is presented,and it is shown that changing specific tire parameters will not significantly affect the entire stability region boundary,but will have a significant impact on the local part of the stable region boundary.It provides dynamic guidance for the engineering application problem of tire selection based on working conditions,and perfects the analysis of the stable region of the vehicle system.Lastly,the relationship between it and the bifurcation method of the equilibrium point is explained,the theoretical analysis method is improved,the generalization ability of the system with high degrees of freedom is stronger,and the dynamic theory of the(driving-steering)space is perfected.Last but not least,the key core arguments of this paper are verified based on Car Sim.It includes verifying the correctness of the dissipation of energy layering characteristics in the global region;verifying the correctness of the mapping relationship between the tire force characteristics and the stable region;verifying the correctness of the conclusion of vehicle bifurcation and dissipation of energy mutation.It also illustrates the good generalization ability of the dissipation of energy method when it is applied to systems with high degrees of freedom.To sum up,this paper proposes a quantitative analysis method “dissipation of energy” for the analysis of the global characteristics of vehicle system dynamics.For the first time,the dynamic global characteristics of the vehicle plane motion system in the three-dimensional state space and the evolution law of the system with the change of the control quantity are revealed quantitatively from multiple angles and multiple aspects based on the dissipation of energy,Lyapunov exponent and related indicators of vehicle performance.In addition,the nonlinear mapping relationship between tire force characteristics and vehicle stable region is calculated and bifurcation point calculation method using the dynamic bifurcation characteristics of the system is proposed.In short,the paper provides a new method and new idea for the global dynamics analysis of the vehicle plane motion system.