Process Linearization for Closed-Loop Control of Incremental Sheet Forming

Incremental sheet forming has, despite its great flexibility, not yet been widely adopted by the forming industry, due to its limited geometric accuracy. One of the approaches to overcome this problem is the development of closed-loop control systems. Such control systems are mostly based on linearization with respect to a nominal toolpath. In this work, different approaches to create such linearized process models are reviewed. By implementing the models in a numerical simulation of a model predictive control system for incremental sheet forming, it is investigated how manufacturing accuracy is affected by the chosen linearization. Based on these results, the validity of the most commonly used linearization method is critically discussed. Furthermore, it is shown that the geometric accuracy can be improved by extending the process model with a time-varying component that contains historical information about past control actions.