Study On The Monitoring System For Resistance Spot Welding Based On SOC

Resistance spot welding is the most important welding method, which is usedwidely in automobile, aviation industry etc. It has the advantages of highmechanization and high automaticity, simplicity of operation and good workingconditions. Spot welding is a highly nonlinearity, multivariate coupling course,which is effected by many random uncertainty factors. As the nucleation course is inclosed state and can't be observed immediately. The characteristic signals are hard toextract. The nucleation time is very short;little fluctuation of welding conditions willbring out serious consequence. If checking the welding quality after welding course,it not only wastes much of manpower and material resources, but also can't assurethe quality. To design a real-time spot welding parameters monitoring andcommunication system will help to acquire the dynamic parameter of welding coursemore overall, well and truly. After data handling, the system can real-time display theinformation and take monitoring data as basic information write in data base of spotmonitoring system. All these functions are of far reaching importance to satisfy thedemand of real-time quality monitoring and evaluation, to determine the qualitygrade and to realize the right spot welding quality control.In order to meet these needs, the paper has finished the design of resistance spotwelding parameter monitoring system based on SOC and CAN-bus. As the quality ofbutton weld is mostly according as the rectangular dimension of nugget, moreoverthe rectangular dimension of nugget are lie on the parameters of welding course.People can realize the real-time monitoring of welding quality by monitoring thetechnological parameters of spot welding. In the welding process, welding current,electrode force and interelectrode voltage are the most important technologicalparameters, so the monitoring objects in this spot welding technological parametersmonitoring system are spot welding current, electrode force and interelectrodevoltage.This monitoring system combine the new development of field bus techniqueand integrated electronic technology;take the single-chip microcomputer system asthe hypogynous machine, industrial PC as the epigynous machine, and use theCAN-bus as the communication medium. The hypogynous node can realize thosefunction, such as data acquisition, signal processing, real-time display and give analarm;the epigynous machine connects every intelligent node of CAN-bus by CANadaptive card, and accomplishes the welding parameters data acquisition, storage andmanagement, etc.In the paper, the system takes C8051F020 single-chip microcomputer as themain control unit of the hypogynous machine. This product of Silicon, Inc is onekind "Totally Integrated Composite Signal System Level Chip (SOC)", its interiorintegrated most analog and digital peripheral equipment of control system. The nodeuse the integrated ADC0 to collect spot welding parameters, combiningITM128128A LCM, keyboard and IS6LV1024LL memory external module, torealize the welding parameters real-time processing and display. To gather the mostimportant spot welding current signal, Rogowski loop is adopted. This system usedthe loop to abstract signal from secondary circuit of welding transformer. After thegained signal differential passed the hardware integrating circuit, the signal entersinto ADC0 to carry out next step process.Because the work positions are usually spread around and there are too muchenvironmental disturbance in field of welding production, this paper apply theCAN-bus to set up the distributivity real-time monitoring system. This system adoptsindustry PC, PCI-5121 and CAN-bus to realize data and command communicationbetween the epigynous machine and the hypogynous machine. The communicationmodule of intelligent node is chiefly composed by CAN controller SJA1000 andCAN transceiver PCA82C250, which are products of Phillips Co. SJA1000, takecharge of the exchange of status, command signal between MCU, and undertake thenetwork communication. By programming, MCU setting SJA1000's work mode,control its operating state, carry out data's transmission and receiving, and establishthe application layer on it. PCA82C250 is the interface between CAN controller andphysical bus. It can provide bus the differential transmission ability and provideCAN controller the differential acceptance ability.This paper used Silicon IDE (integrated development environment) to compileand debug the program which is used to realize data acquisition, data processing,keyboard scanning, LCD display, and CAN communication function. In Silicon IDE,program object code is downloaded to control chip by JTAG interface;it can beconveniently to unload, modify and debug the program. Then ISP and IAP come true.At length, the compiled applications which are running inerrably are solidified insingle-chip microcomputer.The resistance spot welding parameter monitoring system can be used in manykinds of spot welding machine, such as AC spot welding, single phase rectificationspot welding machine, three phase sublevel rectification spot welding machine,inversion spot welding machine, etc. This system has many advantages such as lowervolume, lower cost and good human-computer interaction interface. It could be usedin all sphere of production of machinofacture, automobile, ship, aviation, etc, and gethigh use-value and wide long term potential.