This test verified the effectiveness of PIESO to extend
the solenoid’s travel range and to follow the reference input.
In practice, a maximum stable position of 5 mm was achieved,
which reached 77.6% of the total range. Also considering
that the maximum stable range of the open-loop system was
2.2 mm, the set points were 2.2, 4, and 5 mm, respectively.
The step responses occurring at 0.5 s are illustrated in Fig. 7.