Reviewing the simulation and experimental results, it is
clear that the time delay has the effect of decreasing the
damping. Even if the original mechanical system is not slightly
damped, time delay caused by measurement and actuation
can influence the IOL technique’s performance. In reality, the
existence of friction may enhance the performance under the
time-delay problem, but it is not reliable. The PIESO can
effectively extend the stable range and maintain the position
without perfect knowledge of the system characteristics. This
requires accurate feedback and adjusting the ESO’s parameters
depending on the designer’s experiences.