I just had a brainstorm thinking about a recent earthquake that happened in my area. Then I began thinking about something I saw on one of the science channels where they were testing construction techniques. They used what appeared to be a hydraulic cylinder to shake a platform. I imagine that for their test to be valid it would have to be a very precise system. So I began wondering if hydraulic systems could be used as precision positioning systems, and if such a system could also be adapted to something such as CNC or robotics. I have considered electro-mechanical linear actuators, but the size of the actuators is too big for the amount of force I need. So a hydraulic cylinder with a pump that can be mounted out of the way seems to be the answer.
This must have been done before, I can not be the first person to consider something like this. The application in mind requires compact size and large amounts of force, but also requires a certain amount of accuracy and precision to be controlled by a computer, at least in part, so using standard manual hydraulic valves would not work.
I'm wondering if the piston can be positioned similar to the way a stepper motor is positioned, meaning simply metering the amount of fluid coming and going to and from the cylinder. My current use for such a system would have an accuracy and repeatability of about .100" to .250" so it doesn't need a high degree of accuracy. Coming from an automotive background, I know that a lot of Dodge/Chrysler vehicles use an automatic transmission that uses PWM solenoids to meter fluid into the various hydraulic circuits to change gears. This is also how fuel injectors meter pressurized fuel into the engine. The application I have in mind is not quite the same, but similar so I think the concept is valid, just not sure if this would work with hydraulic cylinders.
Any thoughts or information on the subject would be greatly appreciated.