Blog: Hydraulic and Pneumatic Linear Actuators

Hydraulic and pneumatic linear actuators are basically displacement cylinders fed from a pump or compressor,  controlled by a system of hydraulic or pneumatic valves.   Modern hydraulic positioning systems use proportional valves or for high accuracy applications, single or multiple stage servo valves. The servo valves convert the electric current command from an electronic control system into mechanical motion within the valve body, opening the ports to enable the flow of the fluid to/from the hydraulic cylinder. There is a feedback device (usually an LVDT, or inductive displacement measuring device) required within or connected to the linear actuator which brings the valve controlling   "torque motor" via the electronic control into equilibrium.