In-process feedback control of tube hydro-forming process

The present work will address the problem of designing an in-process control system for a tube hydro-forming process, controlling the tool filling forming a T-tube. The control problem is nontrivial as wrinkling and bursting will develop rapidly and, in most cases, are irreversible—thus, the control system must react fast and without extensive overshoot. The objective is to control the tool filling, reproducing a reference filling trajectory, where the controller input is defined as a correction of the reference forming pressure. The control system was verified experimentally, using four different error scenarios. Initially, the error was provoked, by manipulating the input signal, and for all three cases, the control system successfully eliminates both wrinkling and bursting. Finally, the material was changed going from an aluminum grade 5049-0 to 6060-T6 also; in this case, the control system eliminates the error and stabilizes the process. The control strategy and implementation was developed using numerical simulation (explicit finite element), and the controller implementation was reused directly in the experimental setup without manipulating or scaling the gain factors.