The stable operating region of an electrostatic comb drive actuator in constant-gap mode is limited by a subcritical pitch-fork bifurcation known as side pull-in. We show that oscillatory open-loop control can forestall side pull-in and substantially extend the stable operating region. To our knowledge, this is the first demonstration of control of side pull-in without additional lateral actuators. To our knowledge it is also the first application of open-loop oscillatory control to an electrostatic MEMS model using a single control voltage. Simulations show the stable range of travel increased by over 60%, with an associated oscillation of less than 2%. Although feedback control has been used to stabilize a related bifurcation in electrostatic gap-closing actuators, we show that these approaches are unlikely to succeed for side pull-in. Finally, we present and validate formulas relating parameters of the oscillatory input to the average value and oscillations of the resulting displacement.

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