Taking the He-Ar mixed gas as protected atmosphere, TIG welding process parameters for AZ31 magnesium alloy plates was optimized by using the method of the orthogonal experiment and variance analysis.

The control system for mixed chains, as the most important part of automatic warehouse, can transport all kinds plates, pocket objects, boxed items, parts assembly and assembled unit cargoes.

By calculation, it is proved that the solution is well suited to some rectangular plates with a free end. So, the principle of minimum potential energy with mixed variables is proved for the plates.