Hydraulic aerodynamic actuators utilize pressurized gas or liquids to achieve linear motion and have the largest output potential. These systems include a piston, which is in a sealed tube, and both ends have valves. The piston is connected to an actuator rod, and the rod passes through the seal at one end of the tube. External pressurized source gas or liquid, usually air or hydraulic oil, by which one of the valves is introduced into the cylinder. According to the fluid, the actuator will move forward or backward. There are many other valves, using a lower frequency linear actuator, such as a thermal actuator, which utilizes the expansion of wax and other materials to provide linear motion.
Other types include piezoelectric, magnetic properties, and gear rack actuators. Perhaps the simplest is manual spiral, similar to that used to adjust the cursor. This type of linear actuator uses the same principle as the lead bum, but there is usually a thinner thread for more accurate adjustment.
