Resistance spot welding is widely employed as a manufacturing process. In recent years, the requirement for more sophisticated quality control procedures has considerably grown in the mass production industries. The predominant reasons for this are, the use of alternative materials, such as high strength coated steel and the increasing need for stricter quality control procedures. The requirements for high productivity and good weld qualities have lead to the development of more widely available microprocessor or computer based control, as weld state monitoring system and on-line feedback estimation.
The Resistance spot weld qualities, shear strength, indentation and nugget diameter, are affected by welding current, welding time, welding pressure and so on, called process parameters. As usual, weld qualities are controlled by only weld current which is dominant parameters to welding process. Using air pressure for compression, the study about effectiveness of pressure change in welding has not well done. There is therefore, a considerable interest in the application of more sophisticated, intelligent process control procedures, welding pressure control. We will apply pressure using servo AC motor and control real-time feedback force. The characteristic of this methodology is defined as two aspects. One is the quality control with welding pressure instead previous welding current. The relationship of welding pressure and welding qualities (tensile strength, nugget diameter, indentation) will be shown. The other is the largest portion is removal of unnecessary stroke of gun. This enable us shorten the production time, consuming cost.
The main object in this thesis is analysis about the effectiveness of pressure to weld qualities and design of force robust controller for bad control abilities, as like high stiffness and disturbance by welding current.
