Abstract
The undesired square-law characteristics in micro-electrostatic actuators and magnetic solenoids results in a limited stable range, which reduces their application fields and performance. This research investigated the isomorphic dynamics in these actuators and observed that the nonlinear drive force and the uncertain time delay are the challenges for the full range position controller design. A hybrid nonlinear control scheme includes an input–output linearization controller and a feedback posicast compensator for targeting these problems with abundant stability margin. The experimental results show that the stable range has been extended from 33% to 80%. Furthermore, it is the first literature report of this type of actuator that can track sinusoidal motion beyond the conventional stable range with an amplitude of 70% of the total range. This contribution can significantly enhance the performance of micro-sensors or expand the usage of electrostatic/magnetic actuators in motion-control systems.
Highlights
Electrostatic parallel-plate actuators (PPA) and magnetic solenoids are commonly used actuators in industrial applications
When the PPA is operated in its open-loop stable range of motion, the electrostatic force and the spring force are in equilibrium
By analyzing the mechanical and electrical behaviors of solenoids and PPAs, the general properties of the actuators possessing a square-law characteristic can be summarized as: (1) The mechanical part is suspended with spring and dampers which can be considered to be a linear second-order system
Summary
Electrostatic parallel-plate actuators (PPA) and magnetic solenoids are commonly used actuators in industrial applications. The nonlinear plunger-type solenoids are used as key actuators in variety of fields, such as biomedical apparatuses [7], internet of things [8] and magnetic bearings [9] These kinds of actuators may have different exteriors, but their physical dynamics are isomorphic in that the mechanical part is a linear second-order system and the driving force is proportional to the square of the input term [10,11]. The contributions of this work are summarized as follows: (1) The comprehensive mechanical and electrical coupling model for actuators with square-law input characteristics are analyzed and unified This model points out the challenges for the control system design.
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