[Culvan Van Li]

You could put a motor and encoder on the pressure valve then control the position of the motor. It's almost trivial with the Jaguar using CAN. The biggest difficulty would be ensuring your start point is where you want it. You could run it to a stop of some sort to make sure you have the position correct.

Another option is to control the duration signal letting the air in. If it takes 250ms for a full stroke, then having an "on" signal that is shorter than that will reduce the power it has when it reaches the endpoint. This is probably the simplest method and requires the least parts, but it requires more fine-tuning to make it work as desired. It might be possible to even pulse width modultate the air intakes to achieve an overall slower speed. Perhaps you would have it forward for 20 ms and backwards for 10 ms and repeat that pattern until it reaches the desired position. This will use more air since you are using the air to oppose the movement of the pneumatic cylinder.

Andy