To isolate precision machines from floor vibrations, active vibration isolators are often applied. In this
paper, a two-sensor control strategy, based on acceleration feedback and force feedback, is proposed for
an active vibration isolator using a single-axis active hard mount. The hard mount provides a stiff support
while an active control system is used to get the desired isolation performance. In our previous work, we
showed that a sensor fusion control strategy for active hard mounts can be used to realize three
performance objectives simultaneously: providing isolation from floor vibrations, achieving a low
sensitivity for direct disturbance forces, and adding damping to internal modes of the supported
precision machine. In the present work, an enhanced control strategy is presented, referred to as two-
sensor control. We will show that two-sensor control outperforms sensor fusion, because it has more
possibilities for loop-shaping and has better stability properties. The two-sensor control strategy is
successfully validated on an experimental setup.