Simulation And Experimental Research Of Traction Test Method Of Parking Brake Performance

With the increase of domestic car ownership,road traffic safety problems are increasing gradually,so the motor vehicles safety technology inspection has become particularly important.National mandatory standards regards ramp test method as the standard method for parking brake performance test.But in engineering practice,there are few vehicle inspection agency capable of building standard ramps,and other alternative methods such as traction test method and roller opposite forces type brake tester test method are usually used to test the vehicle performance.When the parking brake performance is tested by alternative methods,the vehicle is generally kept in a horizontal posture,which is completely different from the state of the vehicle in the ramp method.However,by referring to relevant data,it is found that there are few studies on the consistency of the results obtained by the two methods.Therefore,it is necessary to study the factors that affect the parking brake performance test,and on this basis design and develop a parking brake performance test system.Firstly,the common parking brake performance test methods are briefly analyzed.Except for the ramp test method,other test methods generally ignore the changes of elastic deformation of chassis components and the displacement of the height of the center of gravity of the vehicle caused by the redistribution of the load on each axle when the vehicle stops on the ramp,but the advantages of traction test method are relatively prominent in practical engineering applications.Therefore,it is necessary to take a domestic large bus as an example to study the elastic deformation characteristics of its chassis.Then,the small and complex deformation of the bus chassis is ignored,and the finite element simulation method is used to simulate the elastic characteristics of the tire and suspension leaf spring assembly.For the tire,the natural equilibrium profile curve method was used to draw the profile of two-dimensional section and imported into Hypermesh software for mesh division.Write.inp file to set material properties and rotation operation on two-dimensional section grid information of tire,make it become a three-dimensional finite element model of tire;The stiffness characteristics of the tire under 5 different inflation pressures were obtained by using ABAQUS finite element calculation on the Windows Power Shell.For the leaf spring assembly,by analyzing the geometric characteristics of the upper and lower surfaces of the spring leaf after machining and bending,the curve profile can be described by means of point set,so as to fit the polynomial function relationship of each curve.The profile of the spring leaf was drawn in Solid Works software to generate a 3D model with function drive,and each blade was assembled as a leaf spring assembly.The assembly was divided into 3D meshes with Hypermesh software.The grid information was imported into the ABAQUS interface for pre-processing and simulation calculation.Then the reasonability of the finite element model of tire and leaf spring assembly is verified by empirical formula and actual measurement respectively,which can be used as the research basis for the parking brake performance test.Finally,the finite element calculation results of tire and leaf spring are fully considered to analyze in detail the forces on the vehicle when it is parked on a ramp,and this is used to study the effect of the vehicle structural design parameters and the angle of the test ramp on the parking torque required to be provided by the parking brake.Based on vehicle parking brake force model on the ramp,a parking brake performance test system matching the traction test method was designed using Qt development environment and C++ language.The system includes hardware control,real-time data display and information data protection and other basic functions,can improve the accuracy of traction test method parking brake inspection results.