• Solenoids can be used to convert an electric current to a limited linear motion.
• Hydraulics and pneumatics use cylinders to convert fluid and gas flows to limited linear motions.
• Solenoid valves can be used to redirect fluid and gas flows.
• Pneumatics provides smaller forces at higher speeds, but is not stiff. Hydraulics provides large forces and is rigid, but at lower speeds.
• Many other types of actuators can be used.