Positional Control of Cylinder

Short answer is yes.

Longer answer, you will need to install a linear position sensor on you hydraulic ram. The piston of the ram will need to have a magnet fitted to it. Then, assuming, your hydraulic actuating gear has the requisite finesse, and you utilise the output of the sensor to verify the position of the piston in the cylinder then very accurate movement can be expected.

Note: It is not cheap, accuracy costs money. That goes for the hydraulic gear as well.

Thanks a lot. I am also thinking about the electric cylinder. Do you know which one is better choice in term of the cost and size? electric or hydraulic?

At any temperature?

I think the temperature will be within 20 degreeC to 50 degreeC.

Air cylinder??? No. Hydraulic cylinder??? Maybe. Micrometer, I assume, is 1/1000 of 1 millimeter. How accurate do you really need the position to be?

Thanks. I don't need the accuracy, but the repeatability which is 1um (0.001millimeter).

For that kind of accuracy, you'll need a robust mechanical stop, and even then, I would not guarantee 0.001 mm accuracy.