Designing a feedback control algorithm for the tube hydroforming process

Tube hydroforming has a broad industrial appeal as the process enables production of geometrically complex parts within a single forming operation. The process is highly flexible with respect to adjustable process parameters (in the present context trajectories for the internal pressure and axial feeding). The objective of the present work is to identify a suitable and representative set of state variables and to develop a feedback algorithm enabling online control of material flow throughout the part using only limited/local information regarding the filling of the tool cavity. The filling of the tool is controlled by the internal pressure and the axial material feeding, and the proposed system operates with a constant axial feeding trajectory and controls the internal pressure based on the filling of the tool geometry. The methodology proves to be stable and flexible with respect to the dynamic behavior of the system and the numerical tests show that it is possible to control the quality and plastic deformation of the tube. Numerical simulations show that the control system can eliminate both rupture and irreversible wrinkling - which are the two major failure modes in tube hydroforming.