I got a position error measured by a linear encoder like in the picture below.
Could anyone explain some possible reasons for this kind of shape to occur in control theory?
My system looks like table with four legs.
The four legs move up and down by using motors and have a linear encoder as control reference.
The table should stay in its position after moving up.
The four servo motors actuating the four legs control the position by using linear encoder signals, respectively.
But after moving the table up around 10 mm ~ 20 mm, a strange symptom has happened. One or two encoder signals look like square waves (sometimes one encoder signal, sometimes two, sometimes none).
A simple setup diagram is as below.