Actuator

An actuator turns supplied energy and a control input into a mechanical action, such as a displacement, force or torque. An electric motor produces rotation; a hydraulic cylinder converts fluid pressure into a linear push. The sensor reports a system's state, while the actuator changes it.

In an ideal cylinder with piston area $A$ and pressure difference $\Delta p$, $F=A\Delta p$. Moving at speed $v$ requires volume flow $Q=Av$, so mechanical power $Fv$ equals hydraulic power $\Delta pQ$ before losses. This relation shows why force capacity, speed and supply power must be considered together. In a controlled mechanism, actuator saturation and response time constrain achievable feedback control.