Time-varying control of position-dependent flexible structures
The implementation of lightweight high-performance motion systems increases the effect of structural flexibilities especially when the point of interest, which often cannot be measured, is not at a fixed location. The development of new control methods is required, capable of taking these position-dependent dynamics and modelling aspects into account.
The implementation of lightweight high-performance motion systems in lithography applications among others imposes lower requirements on actuators, amplifiers, and cooling. However, the decreased stiffness of lightweight designs increases the effect of structural flexibilities especially when the so-called point of interest, e.g. for wafer scanners the point where exposure takes place, is not at a fixed location.
To deal with structural flexibilities, this project aims at developing new control methods capable of handling position-dependent and time-varying dynamics, commonly met in the lithography industry and needed to predict/account for the dynamics at the point of interest which are often inaccessible to measurement. To this end, the use of partial differential equation (PDE) representations, position-dependent compliance compensation and LTV feedforward control methods are considered.
The development of the aforementioned control methods will provide future lithography tool (and other flexible structure) developers with a set of implementable time-varying control schemes able to compensate for both low and high-frequency position-dependent dynamics, combined with a solid framework on the far-reaching task of exploiting PDE representations of flexible structures.