are 2.4, 4, and 5 mm, respectively. When the disturbance
frequency is 10 Hz, the output is a sinusoidal signal that has
the same frequency and amplitude as the input, in theory. The
IOL response matches this point in the simulation. Though the
average final value is 2 mm, it ripples around it. The higher
set point failed both in simulation and in experiments. The
system will snap in together or oscillate with a very large
amplitude. The PIESO can extend its stable range to 5 mm
(77.6% of total range) at this situation. However, it also
oscillates around the desired position. At this frequency, the
oscillation has an amplitude of about 0.1 mm. In practice,
the external disturbance does not appear until the reference
input command is given. It is caused by the complicated
solenoid fixture. The static friction force holds the stroke
when the external disturbances have insufficient energy. The
IOL oscillates with a large amplitude (larger than 4 mm) and
does not converge within 1 s. The PIESO can also obtain a
stable range of 77.6% with a rise time around 0.2 s with little
oscillation.