Study On Lower Computer Of The Resistance Spot Welding Monitoring System Based On SOC

Resistance spot welding is a kind of joining method, which has the advantages of high efficiency, simplicity of operation and high level of automation. It is used widely in aviation, spaceflight, energy source, and automobile industry etc, especially in automobile manufacturing. Resistance spot welding has large welding current and short welding time and these factors affect each other. Those make resistance spot welding quality control more difficult, so controlling quality of resistance spot welding becomes very important.Research shows that dynamic signal of resistance spot welding process contains a lot of information, which directly or indirectly reflect the welding spot quality. For resistance spot welding, the joint strength of welding spot is mainly decided by geometry dimension of the welding nugget, which are controlled by many spot welding process parameters, such as welding current, welding period, electrode force, and so on. In addition, some process features, such as dynamic resistance, also reflect the welding spot quality information from one aspect. Therefore we can monitor technology parameters of spot welding in order to control the quality of resistance spot welding in welding production.In order to control quality of the resistance spot welding, a kind of resistance spot welding technology parameters monitoring system which is based on SOC has been studied. The system in this thesis can be used to monitor the quality of the resistance spot welding.The resistance spot welding monitoring system in this thesis uses the upper and lower computer structure. This system takes SOC as lower computer to collect, dispose, storage and display the data of welding current, welding period and spot welding electrode voltage etc. Meanwhile the system takes PC as upper computer to display, storage and analysis the data so that managers can get information about quality of products. USB bus is used to connect lower computer and upper computer. If there is no upper computer, lower can storage those data in an Udisk by CH375HM, and then those date will be disposed and analyzed when an upper computer is got. The paper focuses on the lower computer.In the paper, the system takes C8051F020 single-chip microcomputer as the main control unit of the lower computer, which is a kind of"Totally Integrated Composite Signal System Level Chip (SOC)"from the company named Silicon Laboratories. Its interior integrates most analog and digital peripheral equipments of control system and a MSF. The node uses the integrated ADC0 to collect resistance spot welding parameters.At first, lower computer uses Rogowski current sensor to collect the current signal. The signal adjustment circuit will adjust signals from sensors. After that MCU collects those signals by ADC0 system, and then MCU will count, storage and display those data. To raise a large amount of data acquisition, the system also uses IS62LV1024LL external RAM for mass data storage. SYB240128A LCD module is used in this system to display data. Man-machine interface systems is designed for parameter setting and alarm functions, and real-time displaying the characters and waveform showing of monitoring results. CH375HM is not only used to communicate lower computer and upper computer, but also used to make lower computer send data to Udisk.The software system of lower computer is made up of modules in C program, such as data acquisition modules, data-processing module, interactive modules, LCD modules and USB modules, which realizes the real-time collection and disposal of the system. The program of lower computer is compiled and debugged by KEIL 51μVision2 compiler. In KEIL 51μVision2 compiler environment, program object code is downloaded to control chip by JTAG interface; it can direct observation and control the functions of the device and I/O, online Simulation System Debugging.The software system of upper computer is compiled in Visual C++. It can send some setting parameters to lower computer, and receive/display/analyze some parameters from lower computer.Though there is no upper computer, lower computer can be used as a real resistance spot welding monitoring system. Lower computer has many advantages, such as lower volume, lower cost, good human-computer interaction interface, and mass data storage, etc. Also, it can be used in many kinds of spot welding machine, such as AC spot welding, single phase rectification spot welding machine, three phase sublevel rectification spot welding machine, inversion spot welding machine, etc. In addition, it could be used in all sphere of production of aviation, automobile, ship, etc, and get high use-value. If the software system of upper computer can be developed well, the resistance spot welding monitoring system will be more valuable. In a word, the prospect of the resistance spot welding monitoring system in the paper will be very well.