Adaptive Control of Resistance Spot Welding Based on a Dynamic Resistance Model

Kas Kas,Das Das

doi:10.3390/mca24040086

Abstract

Resistance spot welding is a process commonly used for joining a stack of two or three metal sheets at desired spots. Such welds are accomplished by holding the metallic workpieces together by applying pressure through the tips of a pair of electrodes and then passing a strong electric current for a short duration. This kind of welding process often suffers from two common drawbacks, namely, inconsistent weld quality and inadequate nugget size. In order to address these problems, a new theoretical approach of controlling resistance spot welding processes is proposed in this paper. The proposed controller is based on a simplified dynamical model of the resistance spot welding process and employs the principle of adaptive one-step-ahead control. It is essentially an adaptive tracking controller that estimates the unknown process parameters and adjusts the welding voltage continuously to make sure that the nugget resistance tracks a desired reference resistance profile. The modeling and controller design methodologies are discussed in detail. Also, the results of a simulation study to evaluate the performance of the proposed controller are presented. The proposed control scheme is expected to reduce energy consumption and produce consistent welds.

Highlights

Resistance spot welding (RSW) is an electrothermal process in which contacting metal surfaces are joined by heat
The metal surfaces are held together under pressure exerted by two electrodes
A resistance spot welding cycle consists of three main stages as follows: Stage 1: Squeeze time, during which pressure is applied by the electrodes to squeeze the workpieces

Summary

Introduction

Resistance spot welding (RSW) is an electrothermal process in which contacting metal surfaces are joined by heat. The flow of a strong electric current through the metal sheets causes heating due to the resistance of the joining surfaces and the sheets. A resistance spot welding cycle consists of three main stages as follows: Stage 1: Squeeze time, during which pressure is applied by the electrodes to squeeze the workpieces. The resistance spot welding process is used in many different industries, including automotive, aerospace, railway, military, and industrial manufacturing. An RSW controller design based on using dynamic resistance as a ffeeedback signal is proposed in this paper. TThhee ddeevveellooppmmeenntt ooff aa ddyynnaammiiccaall rreessiissttaannccee mmooddeell aanndd iittss vvaalliiddaattiioonn aarree ddiissccuusssseedd iinn SSeeccttiioonn 33. TThhee ddeessiiggnn ooff aann aaddaappttiivvee ccoonnttrroolllleerr iiss ddiissccuusssseedd iinn SSeeccttiioonn 44. SSeeccttiioonn 55 pprreesseennttss tthhee rreessuullttss ooff ssoommee ssiimmuullaattiioonn ssttuuddiieess,, aanndd fifinnaallllyy,,ssoommeeccoonnccluluddininggrreemmaarrkkssaarreepprroovvidideeddininSSeecctitoionn

Modeling of an RSW Nugget Formation Process

Dynamical Resistance Model of an RSW Nugget Formation Process

Design of an Adaptive RSW Controller

Adaptive One-Step-Ahead Tracking Controller

Findings

Conclusion