Design considerations for automated electron beam welding

The wide interest in electron beam (PiB) manufacturing applications has intensified because of interest in high-productivity and high quality manufacturing. Applications for EB welding in space, defense projects, Strategic Defense Initiative space stations, and the construction of NASA's space modules have also intensified the interest for automated EB welding systems. A control system that will provide robust automation and exception handling requires extensive knowledge of the process. For complex, multivariable, nonlinear, nonstationary processes, various techniques are usually required to capture the knowledge necessary to handle process exceptions.

This thesis develops a methodology and hierarchical control structure and applies it to the EB welding control problem. The EB gun controller is specifically used to illustrate the methodology and the mapping into the proposed hierarchical control and analysis structure. Special attention is given to the process evaluator element of the hierarchical analysis structure, which utilizes a. combination of qualitative, procedural, and mathematical methods to evaluate and to handle process exceptions. The EB gun, filament controller, and emission controller are modeled and integrated together so that the system/subsystem issues can be evaluated.