Research On Suspension Compliant Movement And Full Vehicle Steering Character Affected By Rubber Bushing

Suspension K&C is the key factor in the automobile chassis performance and the emphases content in the chassis development. Because of the large usage of rubber bushing and the increasing of the vehicle speed, suspension compliant movement becomes the focus and core content of Suspension K&C. And rubber bushing modeling is the most difficult and important problem in this research. Based on the project:"Car Chassis Integrated Development Platform and Research on Its Key Technology"and the project:"Certain MPV Chassis Platform Development", the dissertation started an in-depth study on suspension compliant movement, rubber bushings modeling ,the influence on suspension compliant movement and automobile steering character impacted by rubber bushings deformation.1. Suspension K&C and the influence factor for compliant movement Suspension K&C is composed of Kinematics and compliance, the research content and resort for the two parts are greatly correlative. Based on the expatiation for the Suspension K&C, the dissertation analyzed the influence factor for suspension compliant movement.Expatiated the definition, research contents and characters of suspension K&C. Analyzed the loading method for the research on Suspension K&C, and summarized the characteristics parameters of suspension K&C. Introduced simulation and test methods for the research on Suspension K&C character,and the suspension virtual prototype database was established for Suspension K & C character simulation.Based on these, analyzed the factors which impact the suspension compliant movement through the typical suspension in the virtual prototype database, and then pointed out that the suspension topology, installation direction and position of rubber bushings can affect the suspension compliant movement, but the deformation of rubber bushing is the most fundamental causes, and the modeling for rubber bushing is the most difficult problem in the suspension compliant movement simulation.2. Research on rubber bushing modeling and testAfter the systematical research on the problem of rubber bushing modeling, a flex-body rubber bushing model was established which is suited for suspension compliant movement simulation, and precision of the model was validated by test.①Discussed the static and dynamic mechanics character of rubber bushing, and pointed out that the rubber bushing behaves the static mechanics character during the suspension compliant movement, and its modeling is mainly for static mechanics character. Analyzed the important features for the static mechanics character modeling for suspension rubber bushings, such as multi direction rate character, shape, install direction, and so on.②Analyzed the features of some typical bushing models, pointed out their disadvantages, such as plenty of test will be done for modeling, unable to be used to study the influence on suspension compliant movement by the shape, material and install direction of the rubber bushing.③The idea of flex-body rubber bushing model was presented and the features of the model fitful to research on suspension compliant movement was introduced, and the basic theory for flex-body modeling was explained.④After a detailed analysis on the constraints surface of bushing metal, interface nodes, modal extraction and other key issues about the rubber bushing modeling the dissertation established rubber bushing flex-body model ,then analyzed its 28 modal shapes and simulated its main directional rate character.⑤The main directional rate character of the rubber bushing was tested and simulated by single direction loading, and the rate character of test and simulation was compared. The results showed that the flex-body model well expresses the deformation of the rubber, and solve some important problem: (1) Modeling needs only material and shape of the rubber, and leaves out the plenty of tests. (2)The flex-body model includes all directional rate character, and has a high precision. (3)The model can be easily used for research on suspension compliant movement impacted material, shape and install direction of the rubber.The rubber bushing flex-body modeling provided the favorable measure for research on suspension compliant movement and the vehicle steering character.3. Research on suspension and vehicle rigid-flex coupling modeling and testHigh precision model was needed for simulating the influence on suspension compliant movement and full vehicle steering character impacted by rubber bushing. Based on the MPV chassis platform development projects, the dissertation established 10 rubber bushings model in the MPV vehicle suspension by the way of the modeling method proposed in this dissertation, and then with these rubber bushings models, established the front and rear suspension rigid-flex coupling virtual prototype models (for K&C character simulation)and full vehicle rigid-flex coupling virtual prototype model (for handling character simulation). The full vehicle model is composed of 58 rigid body and 10 rubber bushing flex-bodies, has 110 rigid-body degree of freedom, and 47392 degree of freedom when considered the flex-body inner degree of freedom.Based on this work, the test and simulation analysis about correlative suspension K&C and full vehicle handling character were done, and the model was validated with correlative test. The results showed that the suspension and full vehicle models based on the rubber bushing flex-body model have a satisfactory accuracy. This indicated that the method of using rubber bushing flex-body model combined with virtual prototype technology is very befitting to study the influence on suspension compliant movement and full vehicle steering character impacted by rubber bushings. At the same time the test and simulation results both showed that the MPV vehicle has a problem of overmuch under steering character.The research on modeling, simulating and test for suspension and full vehicle provides reliable resort and basis for coming study, as well as brings forward the further problem to solve.4. The influence on suspension compliant movement and vehicle steering character impacted by rubber bushing deformation.In order to illustrate the influence on vehicle steering character impacted by rubber bushing deformation, the vehicle double-track movement model with toe angle variety was established. Based on this model, the principle of influence on vehicle steering character impacted by suspension compliant movement was deduced, and the an explicit mathematical explanation was gained, which can be expediently used to guide the design of suspension compliance character.Aim at the problem of overmuch under steering character in the MPV vehicle, based on the suspension and vehicle model and the above principle, and combined with the test research, the dissertation discussed the influence and improved effect on the suspension compliant movement and the vehicle steering character owing to changing the material and installation direction of front and rear suspension rubber bushings. The result showed that:①Increasing the material Young Module of the rubber bushings at the upper and lower arm in the front suspension will increase the rate of the rubber bushings and can improve the C character of the wheel toe angle due to the action of the lateral force, which is beneficial to decrease the overmuch under steering character of the MPV vehicle, but the front suspension rate increased much, which is not beneficial to the vehicle ride character;②Decreasing the material Young Module of the four rubber bushings in the rear suspension at different level will decrease rubber bushings rate and will not influence the rear suspension rate, but can improve the C character of the wheel toe angle due to the lateral force action at different level, which can decrease the overmuch under steering character of the vehicle at different level, and will improve the steering character;③Changing the install direction of the outer rubber bushing in rear suspension will not influence the suspension rate, and can improve the C character of the wheel toe angle due to the lateral force, which is beneficial to improving the vehicle steering character.④Changing the install direction of the inner rubber bushing in rear suspension will not be beneficial to improve the C character of the wheel toe angle due to the lateral force and the vehicle steering character;⑤At last, by way of moderately decreasing the material Young Module of the four rubber bushing in rear suspension and changing the install direction of the outer rubber bushings in rear suspension, the C character of the wheel toe angle due to the lateral force action was improved commendably, and the MPV vehicle gained the satisfactory steering character.Analyzed the shape deformation of the rubber bushing flex-body in the rear suspension, the results shows that: During the suspension compliant movement, the deformation of rubber bushings is not so much and generally occurs inside the linear range, which indicates that it is feasible to treat rubber bushing material as linear material and to study suspension compliant movement and vehicle handling character by way of rubber bushing flex-body model.