Linear-time-varying feedforward control for position-dependent flexible structures

High performance motion systems in the semiconductor industry can achieve higher tracking accuracy when the structural dynamics of the system are taken into account. This work proposes an LTV feedforward control scheme which is based on the approximation of the system dynamics at low frequencies. The plant approximation contains both the low frequency contribution and resonance dynamics of the dominant modes. As an example of a flexible structure, the damped Euler-Bernoulli beam is investigated with considering the stable inversion of the approximated plant for feedforward control design. The results show a remarkable increase in positioning accuracy of the system being the consequence of the presence of feedforward control forces even when the reference setpoint accelerations equal zero.