BACKGROUND:
An air actuator moves an object to target in 0.5 sec. Air pressure 70-80 psi, 25 mm dia piston, travel distance 25 cm. Shock absorber (dash pot) at the end. Object 1 kg.

PROBLEM:
Too much impact at stop even with dash pot. My setup walks around.

QUESTION:
Do they make an intelligent air piston that cuts down air pressure near the end? Or can I fabricate one with electronic control? Difficult to implement?

I'm sure someone else on here has a more in-depth background in pneumatics, but I'm sure its possible to lower the pressure based on actuator travel.

For instance, your actuator moves the piston while a position sensor tracks its movement.  When the piston travels to a certain point, the sensor output signal trips a relief valve.  How fast you drop the pressure determines how fast the actuator slows.  You would be able to set the position relief point with a simple adjustment.  That's my idea.  Best of luck.

Pneumatics - as you have found - tend to slam things around.  With an approximately constant pressure source (as you would have with a sufficiently large regulator)feeding a cylinder you essentially have a constant force input, hence constant acceleration.  So the motion-velocity profile is pretty much governed by the equations of linear motion with constant acceleration.

Using a choke, it is possible to get a condition where the cylinder volume changes faster than the supply can fill it.  This will result in a reduction in force until the air supply can "catch up".  As you might imagine, it's rather difficult to get this set up to work consistently.

Most cylinders have an option for a reed switch or other sensor to detect the piston.  Using such a switch, you could cut off your supply a some point, and simply vent the "supply" side of the cylinder and just let the thing coast.  You could even achieve braking if you choke the vent.  You might be able to make such an arrangement work for you.

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