Nonlinear control of a linear motion system

It is well-known that Bode's gain/phase relation imposes limitations on the performance of a linear system. Tocircumvent these limitations, two examples from literature on nonlinear controllers, more precisely, a PID withnonlinear gain and a SPAN (split-path nonlinear) filter, are implemented on a motion system in order to improve thestep response in comparison with a conventional linear PID controller. Simulations and experiments are presented and itis shown that these nonlinear control strategies can outperform a linear PID controller