Kinematics Simulation, Dynamic Characteristic Analysis And Structural Optimization Of An Automobile Independent Suspension

With the development of the times,people's pursuit of car performance has become more and more intense.Cars with excellent performance such as good ride comfort and handling stability are favored,and the improvement of the suspension system to the performance of the car cannot be ignored.Although the types of modern suspensions are endless,Mac Pherson independent suspension is still widely used in automobiles because of its reasonable space structure and high cost performance.This thesis is based on the research on the Mc Pherson independent suspension of an automobile.The three-dimensional model of the Mc Pherson suspension is constructed by parameter matching and design,and the spatial structure is optimized by kinematics simulation.The strength analysis of the key parts of the suspension is carried out with the method of static analysis,and the optimization scheme of the parts is determined according to the analysis results,so as to realize the improvement of the performance of the Mc Pherson suspension and the optimization of the structure.The main research contents are as follows:(1)Based on the relevant parameters of a certain car,the performance parameters of the Mc Pherson suspension and the dimensions of key components are matched and designed and drawn into a three-dimensional model,and then an assembly is formed to complete the modeling of the front Mc Pherson suspension.(2)Finite element free modal analysis was carried out on the steering knuckle and lower control arm of the front Mc Pherson suspension,respectively,to obtain the natural frequencies and mode shapes of the first ten orders,and a free modal experimental platform was built and the experimental modal analysis was carried out.The natural frequencies of the first ten orders of the steering knuckle and the lower control arm are obtained;the constrained modal analysis of the steering knuckle and the lower control arm is carried out to obtain the natural frequencies and mode shapes of the first six orders.The simulation and experimental results can be obtained:The natural frequencies obtained from the finite element modal analysis and experimental modal analysis of the steering knuckle and the lower control arm all increase with the increase of the order.The natural frequency of the constrained modal analysis is higher than that of the free modal.The lowest-order natural frequency of the steering knuckle is 877.89 Hz in the free mode and 1417.30 Hz in the restrained mode;the lowest-order natural frequency of the lower control arm is 739.69 Hz in the free mode and 774.47 Hz in the restrained mode,and the lowest order of the steering knuckle and the lower control arm is 774.47 Hz.The natural frequency values are far beyond the frequency range that is most likely to cause resonance during vehicle driving.The strength of the two is reliable and the performance is good.At the same time,it is proved that the established knuckle model and the lower control arm model are reasonable and available,and can be used for follow-up research.(3)The established Mc Pherson suspension model is used to obtain the coordinates of the key hard points of the suspension,and the kinematics simulation model of the Mc Pherson suspension is built according to the coordinates of the hard points and the relevant parameters of the vehicle,and the two-wheel jumping tests in the same direction and different directions are carried out.The variation range of wheel alignment parameters is obtained,among which the parameter changes of front wheel camber angle,kingpin caster angle and kingpin inclination angle are within the ideal range,while the change of front wheel toe angle is more than the ideal range.Based on the above analysis,the toe angle of the front wheel is selected as the optimization object,and the coordinates of the suspension hard points that have a greater impact on the toe angle are selected as independent variables through analysis.To be reasonable,the suspension kinematics model was reconstructed using the optimized hard point coordinates and the simulation test was carried out again.The final results show that the change of the front wheel toe angle is in the ideal range,and the changes in the inclination of the kingpin inclination angle have also been greatly improved.(4)The tire contact force under three typical conditions of maximum vertical force,maximum braking force and maximum lateral force during the driving process of the car was solved,and the static load simulation test was carried out for the Mc Pherson suspension analysis model based on this load condition.The loads at the key nodes of the suspension knuckle are extracted,which lays the foundation for the subsequent static analysis.The finite element static analysis of the steering knuckle model under the above typical working conditions is carried out.By comparing the analysis results,the maximum equivalent stress of 245.81 MPa and The maximum deformation is 0.114 mm,of which the maximum equivalent stress value is far less than the yield limit of the steering knuckle,and the strength of the steering knuckle meets the requirements.(5)The topological optimization method is used to optimize the steering knuckle structure to realize the optimization of the suspension structure.According to the finite element static analysis results under the maximum lateral force condition and the constrained modal analysis results,75% of the mass and 70% of the volume and the first-order frequency of the constrained modal analysis is the constraint condition.The topology optimization of the steering knuckle is carried out,and the structural optimization result is obtained,and the depth of the groove at the connecting arm of the fixed platform is used as a variable in the reconstruction of the steering knuckle structure.The rationality of several design schemes was designed and evaluated.Finally,the structural optimization method with a groove depth of 11 mm was selected as the best scheme.The equivalent stress value of the final optimized steering knuckle model was reduced under the three working conditions,especially the maximum equivalent stress under the maximum lateral force condition is reduced by 79.490 MPa,the weight of the steering knuckle is also reduced by0.4881 Kg,and the weight reduction ratio is 9.2%,achieving the goal of optimizing weight reduction.