Actuators ex Libris: Hydraulic Power

Actuation and mechanical engineers go together like lamb and tuna fish.  Yet there are plenty of engineering schools that do not even touch the subject as it applies to the practical world, and above all else, how it applies to industry.  But man I am sure glad I learned to make that black box model.  The standard google search for designing actuation systems will leave you high and dry unless you use the right keywords which you conveniently don't know.  Lucky for whoever is reading this, my stumble-upon searches usually end up at some tech resource.

Enough crap, lets get to the good stuff.  Actuators are used to provide displacement in a mechanical system. The traditional actuator provides linear, or single axis displacement usually in the form of cylinder slides.  Actuation is provided primarily by electronic solenoids, pneumatics, and hydraulics. Gear systems (depending on how you look at it), can also be used but present an additional design element.  As general rule of thumb, system power and size increase in magnitude from:

electronic solenoids -> pneumatics -> hydraulics

Electronic solenoids and pneumatics generally provide forces up to the order of 100lbf, while most hydraulic actuators provide forces in excess of 10,000lbf.  

Actuators require a complete power system to function.  System design is the challenge engineers face, whether manufacturing the components or building the systems.  This article will address hydraulic power, but pneumatic systems are very similar operating on the same fluid principles and often using very similar components.  A basic actuation system is comprised of two main components: motive power and actuation.  The power in the system follows:

Motive Power -----> Transport Medium -----> Actuation

Electronic solenoids are simple, typically powered by a controlled AC/DC power source, the transport medium electrical wire connecting the components.  Pneumatic and hydraulic systems are slightly more complex, requiring a few more components.  The motive power is provided by a pump, and the transport medium consists of piping and valve controls.  It is worth noting a pump is comprised of two components: a motor and pump head (A topic to be discussed in a future article). A general hydraulic system is illustrated by:

Parker Hydraulics is a high end hydraulics manufacturer, and is also a great place to start for system components and information.