The Research On Control System Of Resistance Spot Welding Power Based On DSP

With the further application of embedded technology and DSP in the welding field,the process of digitalization of spot-welding machine was expedited significantly. At present, the technology of contravariant full-bridge main circuit with IGBT switching has been developed perfectly. As a key member in the digitalization filed, DSP (Digital Signal Processor) has been the process core of control system replaced SCM (Single Chip Microprocessor) undoubtedly. Based on this background, the research which is about intelligentized control system of resistance spot-welding power basd on DSP was completed in this paper.The topological structure of main circuit of resistance spot-welding power were studied firstly, then electrical principles of full-bridge zero-voltage soft-switching technology was discussed in detail. The timing requirement of system output control to PWM pulse was emphasized, and the method of generating PWM pulse which is called constant-frequency phase-shifted controlling strategy was described briefly. To meet the design requirement, the hardware and software programs of the control system were designed. And the welding process can be controlled precisely. In the system a variety of optional parameters were offered which can meet a variety of process requirements in welding spot. Quality monitoring technology which gives first place to constant-current control and the control of constant-voltage and constant-power takes as a subsidiaty was adopted, and the fuzzy control was applied in the process of welding quality monitoring which made the control system more intelligent.The hardware system based on DSP was established, which offers a good hardware platfrom for process control and quality control. The welding parameter sampling circuit to fetch the welding quality imformation in real time and accurately was designed. In the control system all the inputs and outputs were controlled by CPLD. It makes the system extensible and convenient. Modular design approach was used in software design. All sub-process was separated. It can meet the control requirements of welding process in the welding spot flexibility. Also it is convenient for software to update.In this paper, computer simulation technology was used to aid system design.The modules in Simulink toolbox was fully taken advantage of. The nonlinear resistance model of dynamic resistance and PWM Generation Module in the spot welding process were established. On the basis, IGBT welding inverter power supply system simulation model was established. And soft-switching inverter spot welding simulation is realized successfully. And fuzzy controller in the control system was set and the results were verified.