Conflict Analysis And Differential Game Control Of Vehicle Dynamic Performance Based Of Interconnected Air Suspension System

With the development of transportation and the improvement of life,the eagerness for ride comfort and handling stability of vehicles is increasing.Electrically controlled interconnected air suspension can achieve active modulation of suspension stiffness and damping,which is of great significance to improve ride comfort and handling stability.The control of the suspension system stiffness can be achieved by switching the interconnection state of the air springs at the four wheels.Meanwhile,the damping force can be controlled by changing the damping coefficient of the adjustable shock absorber.The conflicts between ride comfort and handling stability exist permanently during driving process.So the improvements of vehicle dynamic performance by coordinated control of suspension stiffness and damping have become the research focus increasingly.The various interconnection modes of air spring system can be switched according to the arrangement of interconnected pipelines connecting air springs.Moreover,the ride comfort and handling stability of the vehicle are sensitive to the air spring interconnection modes under different working conditions.That means,different interconnection modes can improve one of the two performances,ride comfort and handling stability effectively,while deteriorating the other one under certain conditions.Therefore,the contradiction between ride comfort and handling stability under different working conditions and different interconnection modes can be attributed to the performance game.Further,both ride comfort and handling stability attempt to maximize one of the performances,and another may suffer a significant deterioration.A novel approach is presented to coordinated control vehicle dynamic characteristics based on game theory.The proposed approach is assumed to provide new theoretical basis and implementations to improve the performance of interconnected air suspension system.Based on four-corner interconnected air suspension system,a control logic for switching air springs with different interconnections was obtained by simulating and analyzing the influence of different air spring interconnection mode on ride comfort and handling stability under different working conditions with fixed damping.A game model of ride comfort and handling stability was established based on the game theory.The damping force distribution controller and damping force output deviation controller for the adjustable shock absorber have been designed.This paper has developed software and hardware of control system and bench test.The main contents of the paper are as follows.Firstly,the configuration of the interconnected air spring suspension system with four air springs connected to each other was designed based on the in-depth study of the dynamic characteristics of a single air spring and the interconnection characteristics of air spring system.The dynamic model of single air spring,interconnected pipeline model and dynamic model of adjustable shock absorber were established based on thermodynamics of variable gas charge and discharge system.Based on the above dynamic model,a vehicle simulation model including interconnected air springs system and an adjustable shock absorber was established in the vehicle dynamics simulation software veDYNA,which is the basis of the conflict mechanism analysis of ride comfort and handling stability and the foundation of design of coordinated control method for dynamic performance.Secondly,a performance index function that can comprehensively characterize the ride comfort and handling stability was designed.The effects of different interconnection modes of air springs on ride comfort and handling stability under straight and turning conditions were simulated and analyzed based on veDYNA vehicle model.The optimal and deteriorate characteristics for ride comfort and handling stability were also studied.Based on the above simulation analysis and characteristic induction,a new method of solving the contradiction and coordination was proposed via differential game theory combined with the difficulty and characteristic analysis of the conflict and coordination between ride comfort and handling stability.the damping force distribution controller for the adjustable shock absorber was designed based on the game theory.Thirdly,The switching logic of the air spring system interconnection state under complex working conditions was designed based on the performance coordination analysis of different air spring system interconnection states on ride comfort and handling stability,which turn the air spring system to the interconnection state that can solve the primary deterioration performance.On this basis,the damping force distribution controller with adjustable shock absorber output was designed based on the deterministic infinite time domain differential game theory according to the control objectives of the designed system.Taking the designed optimal index function of vehicle dynamic characteristics as the payoff function of the game and the seven degree of freedom vehicle model as the constraints,a game model of vehicle ride comfort and handling stability was established.The optimal distribution of damping force of adjustable shock absorber for the interconnected air suspension system was obtained based on the soft suppression feedback Nash equilibrium solution of the game model.Fourthly,the optimal output deviation controller of the target damping force was designed considering the advantages of the adaptive super-screw sliding mode algorithm in nonlinear disturbance and high frequency buffeting suppression according to allocation of target optimal hindrance.The controller can be used to adjust the adjustable shock absorber to output the target damping force with high accuracy and suppress the disturbance of lumped disturbance effectively.Meanwhile,the Lyapunov stability of the deviation controller was analyzed,and the stability conditions of the controller were given to ensure that the controller has high control accuracy and robustness.The veDYNA software was used to establish the coordinated control simulation model of the dynamic performance of the interconnected air suspension.The validity and accuracy of the control system were verified by the simulation test.Experiments show that the designed control system has the advantages of short response time,high control accuracy and strong anti-interference ability,which can effectively improve ride comfort and restrain the drastic changes in body attitude.At last,the dynamic control performance of the interconnected air suspension system was verified by the bench test.Based on Arduino DUE processor,the vehicle ride comfort and handling stability coordination system controller was obtained,and the test platform of the interconnected air suspension was built.Acceleration sensors,pneumatic sensors and altitude sensors were used to collect the relevant information of the trolley.The bench tests of straight driving and steering were carried out and the effect of vehicle ride comfort and handling stability controller was analyzed.The effectiveness and robustness of the interconnected air suspension coordinated dynamic performance control system were verified.It shows that the designed control system can take into account the ride comfort and handling stability of the whole vehicle,and the evaluation indexes were generally coordinated and optimized,with good effectiveness and robustness.Compared with traditional air suspension,the RMS value of vertical acceleration y was improved by 18.32% when driving on bad road and the roll angle was reduced by 1.26% under steering conditions.In this paper,a coordinated game control method combining with switching air spring interconnection state and vehicle dynamic performance was proposed.It effectively coordinates the contradiction between ride comfort and handling stability and broadens the engineering thinking of semi-active control of interconnected air suspension.The research work has certain significance for improving the research of IAS control field and enriching the research content of IAS.