Active damping of flexure mechanisms: Modelling, design and control for large deflections

The high repeatability of flexure mechanisms is crucial for precision mechatronics. Traditionally, flexure mechanisms are designed with low moving mass and high support stiffness. This assures that the performance limiting parasitic resonances are high, enabling high feedback bandwidth, good disturbance suppression and fast cycle times. However, with ever increasing performance targets, other means of improving the dynamic performance of flexures are necessary. Besides aiming for higher frequencies, performance can also be improved by damping the parasitic resonances. Damping can, among others, be achieved by integrating piezoelectric material in the flexures. The regions with piezoelectric material function as additional sensors and actuators, coupling with the parasitic resonances. Using control algorithms, these resonances can be damped or suppressed. Although the active damping principle has been around for a while, the application to flexure mechanisms brings novel challenges, in particular when large deflections are involved. As the flexures deform under the nominal motion of the mechanism, the parasitic resonance frequencies will change in frequency and modeshape. As a result, the coupling of the parasitic resonances with the integrated piezoelectric material also varies with the deflection of the mechanism. This dissertation aims to demonstrate the feasibility of active damping in flexure mechanisms and to improve the tools available for the design, modelling and control of active damping in flexure mechanisms, with a particular focus on large deflections.