The Handling Dynamic Analysis And Optimization On Rhombic Chassis Vehicle

Handling stability is the key factor that affects the active safety of the vehicle. It's influenced by the structure, the road condition, the driver and etc. Based on the multi-body theory and the former research, this paper gives the processing method of dynamic analysis and optimization of a similar rhombic chassis vehicle and provides a theory foundation for improving the handling stability of a similar rhombic chassis vehicle.According to the layout specialties of the Rhombic Chassis, the proper suspension structures were well selected. Through utilizing the tensor of finite rotation and space analytic geometry method, the parameterized suspension kinematics model was built and the correctness of the model was also verified by the software of ADAMS. Based on the kinematics model, the maximum of the wheel travel track, caster angle, rolling moment arm were optimized by taking the length and initial position of the suspension swinging arm as the optimized variables. The suspension structures and parameters ensured the improvement of the similar Rhombic Chassis Vehicle's handling stability. Meanwhile, the wind tunnel trials have been made on the improved styling body. The result of the test indicated that the aerodynamics performance was highly enhanced.Based on the structure of the similar Rhombic Chassis Vehicle and combining the theory of multi-body dynamics, its rolling mechanism has been analyzed and the full-vehicle steady-state rolling model was set up. In the processing of the Rhombic Chassis vehicle steady-state rolling, the parameters of the height of the centroid and the rolling center, the stiffness of the rolling angle, the load distribution of the suspension which has an influence on the change of the load on tires, lateral acceleration, and rolling angle of body have been analyzed in detail. The rolling limit of the Rhombic Chassis vehicle was also analyzed and calculated in the paper. Combining the analysis results of the full-vehicle steady-state rolling and the requirements of body rolling angle and rolling value in rolling process, the ability of the Rhombic Chassis Vehicle'anti-roll ability has been enhanced.On the basic of the rolling analysis, the Rhombic Chassis Vehicle pitching mode was built. Under the limiting acceleration and deceleration mode, the vehicle pitch was analyzed separately. The paper mainly analyzed the effects that the longitudinal metacentric height and centre of gravity offset impact on the pitching mode. Under the precondition of assuring the Rhombic Chassis Vehicle's rolling stability, selecting full-vehicle parameters, laying out the front and rear suspension steering bars, and determining the proper longitudinal metacentric height and centre of gravity offset could enhance the Rhombic Chassis Vehicle's anti-pitching ability and handling stability.Opening-loop handling stability method is fit for the study of the vehicle's natural property, and it's also the basic of the research of the handing stability. The study of opening-loop handling stability emphasizes the road-vehicle model, without regard to the driver's influence. With this method, the vehicle itself was regarded as a control system. Bases on the general requirements of the stability of the control system, stabilization quality and transient response characteristic, the kinetic characteristic of the vehicle has been analyzed. According to the analysis of the rolling and pitching dynamic model, and combining with the layout of traditional chassis, the primary parameters were determined.On the basic of the time-varying model of three DOF opening-loop handling stability, the steering wheel step input test, steady state cornering test, steering wheel pulse input test of the Rhombic Chassis Vehicle have been simulated, and the steady-state and the transient-state have been also analyzed. All of the response indexes were analyzed and evaluated, on the basic of the confined indexes and the evaluation methodology of the handling stability. Through the steering wheel step input test, steady-state cornering test, steering wheel pulse input test, the results of evaluating indicators indicated that the Rhombic Chassis Vehicle's handling stability was good.The paper is a pilot theory study of the similar Rhombic Chassis Vehicle's handling stability. It will provide a theoretical foundation for selecting the parameters of a similar Rhombic Chassis Vehicle and the improvement of handling stability.