What type of actuator is commonly used in hydraulic systems for linear motion?

In hydraulic systems, a hydraulic cylinder is the primary component used for producing linear motion. This actuator operates by using pressurized hydraulic fluid to create force in a linear direction. The hydraulic cylinder consists of a piston housed within a cylinder, and when hydraulic fluid is injected into the cylinder, it pushes the piston, resulting in movement.

This mechanism is essential in applications requiring significant force and precise control over linear motion, such as in construction equipment, manufacturing machinery, and various industrial applications. The use of hydraulic cylinders allows for smooth operation and the ability to lift or push heavy loads efficiently, making them ideal for tasks that require high force in a linear path.

Other types of actuators like rotary actuators are designed to provide rotational motion, and pneumatic actuators operate similarly to hydraulic cylinders but use compressed air, which may not be suitable for all applications. Variable speed drives control the speed of electric motors but do not serve as actuators in the hydraulic sense. Therefore, the hydraulic cylinder is the correct answer for linear motion applications within hydraulic systems.