Optimization Of Steering System Parameters For Improving Vehicle Handling Stability

As the auto industry plays an increasingly important role in the national economy, own brand has invested more funds on research and design under the background of keeping good momenta in both production and marketing of passenger car. The research and design capability have made considerable progress. Compared with other types of vehicles, chassis is a very important part of vehicle structure development and the basic of automotive design. It’s the top priority of the major car firms from beginning to end. The chassis design of small passenger car is complicated due to the vehicle handling, ride comfort, economy and many other requirements.This paper mainly study the influence of steering system hard points on the vehicle steering parameters and the changes of front suspension design parameters during steering. Then by adjusting hard points, the optimal performance of vehicle steering will be achieved. Access to a lot of relative information about suspension design and steering system development and refer to the actual vehicle development process of design ideas, the analysis of suspension performance is based on the original design parameters and adjust the spatial coordinates of double cross universal joints. By theoretical derivation, the relationship between steering wheel angle and double universal joint transmission output rotation over time is get. To identify the causes of transmission ratio fluctuation and the adjustment direction, the change of double cross universal joints transmission ratio is calculated with MATLAB. Then,3D model is built and compared the transmission ratio fluctuations before and after the change of hard points coordinates in CATTA. With the help of DMU, the transmission ratio fluctuations are compared before and after the change of hard points coordinates; using ADAMS/Car to build the front suspension model, the spatial coordinates is considered as research objects, meanwhile, the percent Ackerman, outside turn diameter and Ackerman error are considered as design objects; the sensitivity analysis is finished with ADAMS/Insight, design objects are compared before and after the change of hard points coordinates; hard points has been changed with the sensitivity analysis consequence, in order to find the trend of suspension kinematics, the parallel wheel travel simulation is carried on; the hard points of rack and pinion steering gear, tie rod and knuckle are projected and connected on X-Y plane, on the base of geometric relationships, the coordinates values are optimized by least squares. Depending on the different adjusting program, hunting and sine sweep driving simulation are used to figure out the effect on vehicle handling stability and the best adjustment for the stability of steering. The comparison results indicates that the second adjustment program has more significant effect optimization on the change of handling stability characteristic parameters, but also solves the problem of transmission ratio fluctuation.