Research On Optimiation Method Of Haerd Poinits And Bushing Stiffness Of Strut-Links Rear Suspension

With the growth in people's standard of living, vehicles are now playing an indispensable role in our works and lives. Increasing vehicle speed and the trend of non-professional drivers have promoted greater demands for vehicle handling stability among the customers.There are many structural factors that influence vehicle handling stability. Suspension structure is a major element. Suspension can ensure flexible connections between wheels and bearing systems, including bearing body or axles, transfer loads, mitigate impacts, attenuate vibrations and adjust the attitude of vehicle while traveling. The guiding mechanism of suspension ensures a reliable transmission of forces and torques between wheels and the body (or frame) and determines the wheels' displacement performance relative to the frame or body, thus determining the fluctuations of the wheel alignment parameters and the position of the vehicle roll center when the wheels are bumping or rebounding, which on large extent affects the handling stability of the vehicle.Adjusting the parameters of suspension is a commonly used method in engineering to improve the vehicle's handling stability. The essence of the technique is embodied in the design and optimization of the suspension hard points and bushing stiffness, generally including the design and optimization of the steering system and the flexibility of the suspension system. The design and optimization of suspension hard points and bushing stiffness is a multi-objective and multi-parameter optimization process. The design variables are the hard points and bushing stiffness of the suspension and steering systems, and the stiffness of the anti-roll bars. The direct design objectives are Suspension K&C Characteristics, the mechanical properties of suspension and the vibration properties of the suspension and steering systems. After the optimization, a further inspection of the handling stability and vibration characteristics of the full vehicle is necessary. Suspension K&C Characteristics is an important indicator to evaluate the suspension performances. Suspension K&C Characteristics means the Kinematics and Compliance Characteristics of suspension. Early vehicle researches and developments were generally focused on how to adjust the suspension parameters for better K&C Characteristics.Associated with a domestic project that has designed and optimized the suspension hard points and bushing stiffness of a B-Class vehicle, this paper studies and analyses the methods to optimize the hard points and bushing stiffness of the Strut-Links rear suspension properties.Build a Strut-Links rear suspension model in the ADAMS/Car module and verify the model's accuracy by real vehicle Suspension K&C Characteristics test. Analyze the force transmission characteristics of the rear suspension and form a primary understanding of the components that affect the properties of wheel alignment parameters. Use the ADAMS/Insight module to statistically analyze the sensitivities of suspension hard points and bushing stiffness to Suspension K&C Characteristics, and find out the sensitive hard points and bushing stiffness. Find the relationship between the deformation of key bushings and the changes of wheel alignment parameters via the principles of mechanical transmission, thus figure out its impact on the Suspension Compliance Characteristics, laying down the foundation for the optimization of the suspension hard points and bushing stiffness.Our research team has determined the optimal target for Suspension K&C Characteristics via the combination of calculating the K&C Characteristics of part of the suspension and the experiential database for vehicle chassis tuning, of which the data has been accumulated for years. By adjusting the sensitive hard points and bushing stiffness, they made the K&C Characteristics curves/slops of the suspension model approach the optimal target. After the optimization process, the team calculated and analyzed the forces loaded on the bushings in different driving conditions, including steering at constant speed, accelerating, braking, steering while accelerating, steering while braking, etc. No excessive deformation of the bushing was found during the inspection. The research team has established a simulation model to calculate the full vehicle model's understeer degree. The result of the calculation indicates that under different conditions of side accelerations, the optimized full vehicle model has shown all-out improvements in terms of understeer degree, compared with the previous model. The effectiveness of the optimization has also been verified by examining the models before and after optimization through Nation Standard handling stability tests.With the assistance of the secondary development tools of ADAMS/Car, of which the author has participated in the programming, our work efficiency has been greatly promoted during the sensitivity analysis of hard points and bushing stiffness and the simulative experiments of handling stability for the full vehicle model, making the content of this paper more systematic and detailed.