What is the difference between a linear actuator and a rotary actuator?

Linear actuators move objects in a straight line, usually in a reciprocating motion. Rotating the actuator is to let the object rotate at an angle, which can be any value. Therefore, the linear actuator performs a reciprocating motion, and the rotary actuator performs a rotational motion.


Simply put, a single motor is a rotary actuator. When a current flows through a conventional servo motor, the motor rotates. Directly connecting the motor to the load constitutes a direct drive rotary actuator. Many rotary actuators are combined with mechanical devices to form a mechanical lever structure that helps to reduce rotation and increase torque. If the component ultimately performs a rotational motion, it also belongs to a rotary actuator.


On the other hand, it is also possible to convert the rotary motion into a reciprocating motion by connecting the rotary actuator to the mechanical device, and then it becomes a linear actuator.


What are the mechanical devices mentioned here? Belts and pulleys, gearboxes, balls and screws, racks and pinions. All of these mechanisms can convert energy in some way. Belts and pulleys can be used to convert the rotational motion of a servo motor into a linear motion, such as a conveyor. Gearboxes typically increase torque, reduce the speed of rotational motion, and convert rotational motion into linear motion by combining with mechanical devices. Ball screws and roller screws are commonly used to convert the rotary motion of a servo motor into precise linear motion, for example in machining centers.


It is worth noting that when motion transition occurs between multiple devices, in order to achieve high bandwidth, some physical laws need to be observed to improve the response speed of the actuator. Therefore, the actuator should be as close as possible to the load, such as direct drive rotary motors and direct drive linear motor solutions usually provide the highest bandwidth system.

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