Dynamic Analysis And Research On Automatic Checking Fixture Of Front Sub Frame

In the production process of the automobile front sub frame, it is required to detect the geometric parameters online quickly and efficiently. This article uses the automatic measuring system to improve the efficiency. Using the cylinder to send testing agency into the hole and shaft and other position of the structure in the process of automatic detection. When the relative size changes, it will drive the detection mechanism, then read out corresponding data through the sensors which are connected with detection structure. At last, through the information processing method to calculate the correlative geometric parameters.The front sub frame is a thin wall welded structure which shape is complex, it is about 2mm thickness. It needs cylinder to drive the related mechanism when positioning clamping and testing, the change and fluctuations of cylinder pressure have a very large influence on test results. Displacement sensor used for testing is sensitive to vibration, but vibration is inevitable when using cylinder to clamp and drive testing institutions, it also Impacts the test results.In order to solve the above problems and improve the automatic measuring system, the main work of this paper is as follows:(1) First, analyze the characteristics of the front sub frame structure, use CATIA software to build a three-dimensional model of the existing automatic detection system, then research the structure and detection principle of each component of the automatic detection system.(2) Using Hyper Mesh conduct front sub frame grid division and establish the finite element model, then import the finite element model into ABAQUS software with carrying on dynamics analysis which include modal analysis and transient response analysis. Filling air pressure load on the structure, then concluded that the location of the deformation under different load conditions.(3) Due to the effect of pressure on the test results in the automatic detection process,using polynomial regression analysis method. The results show the deviation between the pressure and the front sub frame each main dimension. By Particle Swarm Optimization algorithm, regard the overall deviation of the main dimensions about the sub frame as the fitness function, the iterative optimization optimal pressure is 0.4578 MPa.(4) By studying the transient dynamic analysis of the stabilizing plate under 0.4578 MPa air pressure, it is found that the choice of measuring time has a great influence on the accuracy of the measurement. By analyzing the displacement deformation of the three mounting holes and the left hole of the stabilizing plate at the optimal pressure, the optimum time to read the sensor data is 2s after unloading the load.Front sub frame automatic measuring system in automotive production field application shows that the automatic measuring system can be competent for test requirements. The perfect testing system can improve the production efficiency of enterprises with high detection precision.