Investigation On The Model Based Chassis System Handling And Stability Performance Analysis And Design

With the rapid development of domestic passenger car market, the demand of the performance control work during vehicle development process become more and more intense. Chassis system performance is directly determinant factor which decides the vehicle handling and stability behaviour, therefore chassis system design is the key technology in vehicle development. The thesis take passenger car as the target, this dissertation presents contents and methods of a study on handling and stability performance control at design stage. As handling and stability performance control relates to many aspects, this dissertation only studies part of performances of suspension system and steering system, we make use of virtual prototyping technology to build the dynamical simulated model prototype prior to producing the actual physical sample, and conduct on the vehicle and subsystem handling and stability performance design based on the model. Surrounding this, this thesis has mainly accomplished the following studing content:Suspension K&C characteristics analysis and optimize. By means of analysing the the topology structure of the front and rear suspension in prototype car, then build the structure-oriented model of the front and rear suspensions, with this model to establish the relationship between suspension structures parameters and suspension K&C characteristics. Then design the ride performance and roll performance of chassis, to determine the suspension stiffness characteristics. Then make kinematics simulation to the front and rear suspension, compare the prototype vehicle suspension K&C characteristics with the desired K&C characteristics and find out the differences between them. There are many design factors in suspension, so we must perform the sensitivity analysis to find the highly important design factors and establish the relationship between important design factors and K&C characteristics. Finaly, use this approximation model to optimize the important design factors.The match and design of steering system characteristics. According to the steering factors of suspension, calculate the chassis’s steady turning performance. And according to the requirements of vehicle steering portability and vehicle steering sensitivity, to determine angle ratio of the steering system, then according to the steering kinematics analysis to determine steering gear ratio. Secondly, in steering angle ratio determined premise, the main design parameters is assist characteristics for the steering force transmission characteristics.Through simplify the characteristic curve of reference car reasonably, and then we analyzed the curve by each section to determine the influence of each section in the entire power steering system. Calculation and analysis is applied for steering aligning torque of each steering conditions, then the parameters of assist characteristics are selected.The evaluation of vehicle handling and stability performance. On the basis of front and rear suspension model, writer build a structure-oriented entire car simulated model of prototype including the bodywork, powertrain system, braking system, steering system, tire, and make use of the model to carry out many handling and stability simulation, in line with vehicle manoeuvres specified under National and ISO Standards, there are:steady-state steering performance, transient-state steering performance, hign-speed steering returnability, roll and pitch performance, on-center handling, then compare the handling and stability characteristic which stem from processing the simulated conclusion with the bid vehicle’s characteristic, to verify the system level characteristic parameters.