| The double wishbone independent suspension has lower unsprung mass.It can effectively bear various alternating loads with the unique design of double transposition arm,and the optimal handling stability and ride comfort can be obtained by a reasonable arrangement of parameters.It is not only widely used in the passenger car,but also applied in the multi-axle special heavy-duty vehicle.The dynamic load of each component in the double wishbone suspension system is the main basis for the design of suspension and the body(or frame),which is essential for vehicle design and performance analysis.A calculation method of the dynamic loads for the double wishbone independent suspension based on velocity and acceleration analysis is proposed in this thesis.Compared with the commercial multi-body dynamics software ADAMS,the validity of the model and solution method is verified.The main contents are as follows:(1)Two dynamic models of double wishbone independent suspension are established,one with rigid connection of the body and control arm,the other with flexible connection.The velocity,acceleration and displacement of the suspension components are analyzed,and the dynamic equilibrium equations of the suspension are derived.The mechanical model which describes the nonlinear characteristics of the bush is established in the dynamic models with flexible connection.Using the 6-axis wheel load and acceleration measured from the road test as model input,the dynamic load of the suspension can be obtained by solving the dynamic model.(2)The algorithm for solving the dynamic model is studied.There are a number of continuous large nonlinear equations in the dynamic model.In the case of initial value uncertainty,it is often difficult for the general numerical algorithm to solve.For the dynamic model with rigid connection of the body and control arm,a numerical algorithm based on BFGS and PSO is proposed,which can be used to solve the model effectively.For the dynamic model with flexible connection,it is more difficult to solve the dynamic model with flexible connection,thus an iterative method for solving the model is proposed.This method divides a group of nonlinear equations with many unknowns into two groups of equations with less unknowns.And the model is solved effectively by the iteration process between the two equations.(3)Model verification.The analytical model of double wishbone suspension is established based on MATLAB,and the corresponding multi-body model is established in ADAMS.The simulation calculation is performed under a variety of typical working conditions.And the validity of the model and algorithm is verified by comparing the results of the load extraction of the two models.(4)A prototype system for extracting dynamic load of suspension system is developed,which can improve the work efficiency.The prototype system is applied in the fatigue analysis of the front double wishbone suspension in a certain type of vehicle,and the fatigue life is obtained with the vehicle test.The calculation method has certain theoretical and practical significance for improving the efficiency and accuracy of the dynamic load extraction of suspension system,and speeding up the progress of the development of the body and suspension system. |
