  In this paper, we propose a new approach to address the control problem for
negative imaginary (NI) systems by using hybrid integrator-gain systems (HIGS).
We investigate the single HIGS of its original form and its two variations,
including a multi-HIGS and the serial cascade of two HIGS. A single HIGS is
shown to be a nonlinear negative imaginary system, and so is the multi-HIGS and
the cascade of two HIGS. We show that these three types of HIGS can be used as
controllers to asymptotically stabilize linear NI systems. The results of this
paper are then illustrated in a real-world experiment where a 2-DOF
microelectromechanical system nanopositioner is stabilized by a multi-HIGS.
