Abstract
In order to satisfy the demand for the high functionality of future microdevices, research on new concepts for multistable microactuators with enlarged working ranges becomes increasingly important. A challenge for the design of such actuators lies in overcoming the mechanical connections of the moved object, which limit its deflection angle or traveling distance. Although numerous approaches have already been proposed to solve this issue, only a few have considered multiple asymptotically stable resting positions. In order to fill this gap, we present a microactuator that allows large vertical displacements of a freely moving permanent magnet on a millimeter-scale. Multiple stable equilibria are generated at predefined positions by superimposing permanent magnetic fields, thus removing the need for constant energy input. In order to achieve fast object movements with low solenoid currents, we apply a combination of piezoelectric and electromagnetic actuation, which work as cooperative manipulators. Optimal trajectory planning and flatness-based control ensure time- and energy-efficient motion while being able to compensate for disturbances. We demonstrate the advantage of the proposed actuator in terms of its expandability and show the effectiveness of the controller with regard to the initial state uncertainty.
Highlights
Multistability is an important system property found in a variety of microactuators and corresponds to possessing multiple stable actuator positions
We aim to find motions that efficiently enable the proof mass to switch between the equilibrium positions, while taking into account the initial state after the kick motion
The magnetic microactuator has several advantages, such as multiple, asymptotically stable equilibria and the expandability to a larger number of resting positions. This can prove useful for future applications, where large working ranges are necessary, and the proof mass is desired to remain in its position, even without a constant energy supply
Summary
Multistability is an important system property found in a variety of microactuators and corresponds to possessing multiple stable actuator positions While it is most commonly used in switches with two stable resting positions, extending the number of equilibrium points opens up new possibilities in the functionality and application flexibility of microsystems. A considerable number of actuator concepts have been proposed, which can be distinguished in particular on whether the entire actuator or a single object is moved The former includes impact mechanisms, which generate a stepwise motion by repeated impact between an internal mass and a stopper and can be realized using different actuation principles [1,2,3]. Stick-slip actuators move in small steps, but exploit different friction effects Movements of both high precision [4] and large displacements [5] are possible. The actuator is driven by traveling waves, generated by piezoelectric MEMS
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