Cascade control of the friction stir welding process to seal canisters for spent nuclear fuel
Lars Cederqvist, Olof Garpinger, Tore Hägglund, Anders Robertsson
This article presents the development to reliably seal copper canisters containing the Swedish nuclear waste, using friction stir welding. To avoid defects and welding tool fractures, it is important to control the welding temperature within a span of 790–910 degrees C. A cascade controller is used to efficiently suppress fast power input disturbances reducing their impact on the temperature. The controller is tuned using a recently presented method for robust PID control. Results show that the controller keeps the temperature within 710 degrees C during the 40 min long joint line sequences. Apart from the cascaded control structure, good process knowledge and control strategies adapted to different weld sequences have contributed to the successful results.
Cascade control Friction stir welding Temperature control Disturbance rejection PI controllers
Control Engineering Practice, 20:1, pp. 35–48, January 2012.