Arduino

I'm not sure what you mean by "amplitude" in this case, but I'm guessing you want to be able to extend the cylinder varying amounts?

Pneumatic cylinders are difficult to control that way, due to the compressibility of the air. Is there any chance you could switch to hydraulic?

You might have a better chance of success with a hydraulic system that has a flow meter in it...

yet that whaat i wanted to say

fo examplei want that the cylinder extends with 3 mm in and same for out to get a mouvement up and down

for the hydraulic i didn t choose yet so it s possible

Another possibility is an electric linear actuator. That might be the best. Hydraulics can be very messy if you're not a good plumber. :-D

Depending on how much force and speed you need, something like these might be much easier to use and control with an Arduino.

i thought in the electric but i m not sure if its can make what i want as u said

i m working on fatigue testing machine so first the actuator must move so fast , and the electric actuator mosut stop to change the sens of motion that s not good for my project

and thanks so much for replying me

if u have other ideas or even if u want to know more information u r welcomed