Research On Control System Of Surface Defect Detection Device Of Strain Gauges

Strain gauges are widely used industrial sensing elements for measuring stress changes.Surface defect detection of strain gauges is an important process in the production of strain gauges.The long-standing manual detection method greatly limits the production efficiency of strain gauges.In recent years,with the continuous development of technologies such as motion control,embedded operating systems,and machine vision,the conditions for the automation of surface defect detection of strain gauges have gradually matured.In this thesis,an automated device is constructed based on the process of the surface defect detection and marking of strain gauges,and the control system of the surface defect detection and marking device of strain gauges is studied and implemented.The specific work is as follows.Firstly,the detection and marking process of strain gauges’ surface defects is analyzed to design a motion control platform for process automation.Secondly,aiming at the low-cost and high-precision requirements of the motion control scheme,the STM32 is used as the main control CPU to output controllable frequency pulses to control the stepper motor’s operation.Then,in order to realize the basic functions of the platform and the motion control scheme,the hardware PCB circuit and software’s functional modules of the platform controller are designed in turn,and the embedded real-time operating system is transplanted to achieve multi-axis coordinated motion control.Finally,platform functional tests were carried out.The experimental results show that the platform can achieve the control function of single-piece detection and marking of strain gauges,and achieve a micron-level motion control accuracy.To realize high-quality image acquisition of single-piece strain gauge with multiple types,an illumination system suitable for imaging single-piece strain gauge is designed and constructed by analyzing the machine vision requirements for strain gauge detection and considering the practical installation conditions.The image quality of the strain gauge is correlated with the image gradient information.Based on the Tenengrad function of the image,a gradient evaluation method is proposed to proportionally filter out polyimide interference areas.This method is fused with the Tenengrad function to design an exposure evaluation function,and an automatic exposure adjustment mechanism is developed by exposure table and hill-climbing algorithm.Finally,experiments were conducted to capture strain gauge images of different types.The results demonstrate that the imaging system designed in this study can effectively present different defects in the strain gauges,thereby overcoming the limitations of traditional exposure algorithms for identifying pinhole-type defects.To further improve the operational efficiency of the surface defect detection and marking device for strain gauges,an analysis of the time-consuming issue in the entire board marking process is conducted.To address this problem,a scheme is proposed to separate the board marking and detection processes.To implement this scheme,a method is proposed to abstract directed edges as nodes,which is combined with the transformation method of converting ATSP into a classical TSP instance.This method designs a transformation approach to convert the board marking path planning problem into a classical TSP instance,which can be solved using high-performance solvers.To validate the reliability of the transformation method,it is applied to the LKH and Concorde solvers.The experimental results demonstrate that the transformed classical TSP instances correspond to the solutions of the original problem instances before the conversion,and the optimality of the solutions is not cut-down.Finally,by comparing different marking schemes,it is confirmed that the proposed scheme significantly improves the operational efficiency of the device.According to the functional requirements and design requirements of the device,the control software for surface defect detection and marking of strain gauges is designed and developed.It provides functions such as parameters setting of motor speed regulation,platform operation status monitoring and control,and full-sheet detection and marking for operators and researchers.The running tests demonstrate the effectiveness of the control software of the device.