Study On On-Line Detection And Adaptive Control System Of Reconfigurable Welding Fixture

The body in white(BIW) is an important major part of a car upon which all components are built, thus the quality of BIW plays an essential role in improving function and quality of automobile. Automotive welding fixture as a key device is very important for the quality of BIW manufacturing and assembly.Supported by Science and Technology Commission of Shanghai Municipality in the second development of patent project of Initial Location and Flexible Welding Fixture, to detect the dimensional deviation of the welding workpiece quickly and control the quality of welding workpiece, an on-line detection and adaptive control system with the ability to adjust the dimensional deviation is developed based on reconfigurable automotive welding fixture. The main work includes as following aspects:(1) Studying the current BIW measurement technology, on the basis of BIW coordinate system and the relation of coordinate transformation, constructing a theoretical model for the on-line detection and adaptive control system. Using this theoretical model, the three-dimensional coordinate values of key measurement points on the workpiece are measured, then the dimensional deviations of the welding workpiece are gotten. By analyzing the origin of dimensional variation, the scheme of on-line detection and adaptive control system is presented.(2) Constructing an on-line detection platform based on the hardware of sensor, data acquisition card and computer. First, doing the sensor calibration test get the normalization of liner curves. Second, Removing the outliers in Data by software filter technology. Then, developing the on-line detection system by Modularization, Visualization, Active X. It contains parameter setting, intelligent detection, data analysis, etc.(3) Based on UG environment and virtual design and assembly technology, an adaptive adjusting device with small volume and self-lock ability is studied and fabricated to compensate dimensional deviation in welding process. The device consists of a step motor, a membrane coupling, a ball screw, a driving nut, a linear guide, a bracket, etc.(4) For the development of compensation control system, constructing a step motor open-loop control system. Using Step motor subdivision techlonogy to satisfy the system accuracy requirement. Developing the module of clearance adjustment based on PMAC(Programmable Multi-axis Controller) techlonogy.(5) Using virtual prototype technology, design and simulate air control system combined UG and ADAMS to realize the control of fastening and loosing the reconfigurable welding fixture.(6) Testing the reconfiguration, compensation, on-line detection properties of the reconfigurable automotive welding fixture system on the devices such as SGM60, SGM600, and verified by experts from Testing and Verifying Center of Shanghai Municipality, the results show that this adaptive control system satisfy the design requirement.