Research On Resistance Spot Welding Coordination Control Based On DRC Modeling Method

Resistance spot welding is one of the most important welding processes. It isextensively used in modern industry, especially in automotive industry and aviation,for its high-density energy, simple operation, high productivity, and high automation.As the fabrication technique develops, the request for the welding quality andreliability is increasing. According to the request, the ability and the precision ofspot welding control system must be improved. Along with the development of the spot welding quality supervise and controltechnique, especially microcomputer technique and intelligence control applicationin industry control, some of the late-model micro controller spot welding qualitycontrol equipments are gradually expanding. As a whole, control mode has beendeveloping from single mode control into multi-mode control; control method hasbeen developing from a kind of supervise and control into a variety supervises andcontrols decision; regulation parameters have been developing from single variableregulation into many variables regulation; control decision has been developingfrom normal control decision method into artificial intelligence decision method. According to the actual research instance of DRC modeling method controllerin last few years, this thesis aims at the blind area of DRC modeling method inwelding process, which is likely to result in splash or heavy regulation mission inthe later welding process at the significant movement in heat, and so on. On thebasis of wide information and many parameters integration monitor principle,invariable current control is introduced into the control system that is based on DRCmodeling method. We named this method IDRC method that applies different timefield, many level structures and many parameters integration fuzzy control decisionto ensuring each nugget quality in accordance with the welding time. 8031 micro controller is the core of hardware control system that mainlyconsists of external program memory EPROM, external data memory RAM,ADC0809, programmable peripheral interface 8255, watchdog circuit, RAMinformation protection circuit and reset circuit. The hardware control system'sprimary function is to sample the current lag angle in real-time, convert currentsignal and voltage signal to digital, process data and apply fuzzy ratiocination to theoutput. When the AC voltage signal crosses the zero, the voltage synchronous circuitsupplies the micro controller with interruption pulse signal that acts as thebenchmark for the timers and triggering pulse of the thyristors. Under the control of 71Abstractmicro controller, the current sample circuit samples the transformer primary currentsignal by the mutual inductor and the current zero point measurement circuit picksup the current zero point signal. The angle between the current zero point and thevoltage zero point is utilized as the quality control information. Software is the soul of the control system. Consideration the process of weldingis a high nonlinear, complicated coupling process with a lot of stochastic factors,and the process ability of micro controller, we chose the fuzzy control algorithm anddesigned four fuzzy controllers for the real-time control. The program will choicethe corresponding fuzzy controller according to the different condition in weldingprocess. IDRC method makes use of invariable current control in the weldingprophase and DRC control next. The invariable current control has thecharacteristics of quick respondence and high control accuracy, so it can create agood control base for DRC modeling method. The DRC modeling control obtainsthe dynamic resistance curve through real-time measurement the current lag angleand compares the actual curve with the dynamic resistance model curve. Accordingto the windage of valley point time, the increase of the current lag angle after thevalley point and the accumulation value of the increa...