Basics: How Do I Choose an Actuator?

Where to Start

An actuator is a device that converts electrical energy into physical motion. Choosing the right actuators (which include DC motors, gear motors, servo motors, linear actuators, muscle wire etc.) requires an imagination and a bit of math and physics. The vast majority of actuators produce either rotational or linear motion though combinations thereof can lead to complex motion. Keep in mind there are always new and innovative products being brought to market and nothing is set in stone.

Actuators that produce ROTATIONAL motion include:
• DC Motors
• Geared DC Motors
• Servo Motors
• Stepper Motors
• Geared Stepper Motors

Actuators that produce LINEAR motion include:
• Linear actuators
• Solenoid
• Muscle wire
• Pneumatics (Air muscle)
• Hydraulics

To help you find the right actuator for the right task, we have developed the following questions to guide you in the right direction:

Q: Is the motor being used to propel or drive a wheeled robot?

Drive motors must move the weight of the entire robot and should therefore have a gear down. DC gear motors are the ideal choice for robots with wheels as they provide continuous rotation, and can have optional position feedback using optical encoders.

Q: Is the motor being used to lift or turn a heavy weight?

Lifting a weight requires significantly more power than moving a weight on a flat surface. Speed must be sacrificed in order to gain “torque” and it is best to use a gear motor with a high gear ratio and powerful DC gear motor. Consider using system (either with gears, clamps or other) that prevents the mass from falling due to loss of power.

Q: Is the range of motion limited to 0 to 180 degrees?

If the range is limited and the torque required is not significant, a servo motor is ideal. Servo motors are offered in a variety of different torques and sizes and provide angular position feedback (most use a potentiometer, some specialized ones use optical encoders).

Q: Does the angle need to be very precise?

Stepper motors (coupled with a stepper motor controller) offer very precise angular motion. They are sometimes preferred to servo motors because they offer continuous rotation. Some continuous rotation digital servo motors, which often use optical encoders, now offer the same functionality as servos but with very high precision.

Q: Is the motion in a straight line?

Linear actuators are best for moving objects and/or positioning along a straight line. They come in a variety of sizes and configurations. If your motion requires far less force than that of a linear actuator, consider muscle wire. Air muscles are an excellent choice when considering simulation of organic muscles but require a slightly more mechanically complex control setup.


This is a companion discussion topic for the original entry at https://community.robotshop.com/tutorials/show/basics-how-do-i-choose-an-actuator

Just curious: have you encountered many linear and rotary (combined) actuators?

@John Not really, what purpose would they serve?

and if I need one with the best step angle (max 200eur) and not so hard to configure with an arduino UNO ? Thank you very much

@Sergio You should find a stepper motor with the best step angle (most are 1.8, though many are 0.9 degrees per step), and then choose a stepper motor controller which can provide 1/2 steps and even 1/4 steps.

Hi, I am looking for an actuator that can punch an object roughly the size and weight of a marble and set it rolling at least 5 meters.
something like a plunger used in pin ball machine that can be controlled electronically.
what would you suggest?

@Sudhan That would involve some calculations which are beyond what we can provide here.

Hi, I’d like to make a robotic arm that punches objects, so I am looking for a very fast linear actuator with great force. I don’t care about the size. What would you suggest?

@Kappa You might consider a pneumatic system.

hello, i need help on a robotic project

@Amban We will do our best to help, but it’s best to create a new post on the RobotShop Forum and provide as many details as possible.

Hi I’m looking for something that can twist a dial knob to off position 0°, 60° run, 120° start, and back to run then off. What would you sughest?

@Santiago Gonzalez JR If you want the process to be automated, consider a servo motor (which can rotate 0-180 degrees with absolute positioning) and a microcontroller to program the motion / angles. The choice of servo depends on the torque and rpm you need. The microcontroller needs only to be able to control a servo. Last, you will need a power source of 4.8V to 6V (wall adapter or battery pack).

Hello, I am working on a robot and using 3 motors to actuate its movement, the motors are of type 24 BYJ-48 driven by an Arduino UNO board. I need to change the rotary movement to linear but I am don’t know what linear actuator to use. The robot is just a prototype and not much force is required, but as I was searching online for linear actuator screw I couldn’t find any that work with the motor I’m using, can you provide me with any guidelines on that? Thanks.

Two classic ways to change rotational to linear motion are:

  • Lead screw
  • 4-bar mechanism

It’s not easy to find a lead screw for a specific actuator, so it’s best to either use a long machine screw and a shaft coupler, or a shaft coupler and threaded rod. Regarding the 4-bar mechanism, it’s likely a lot easier to produce, but the linear travel might be limited.
A lead screw is almost always used in DC linear actuators. Ex:


hey, im trying to build a actuator or servo needs to provide linear motion, have a travel rate approaching 1" per second and an overall travel of 1.5". Forces that the actuator must overcome will be determined during ground rig testing this Fall,but it is estimated that forces will be below 25 lbs. do you know how to find the best motor for this?
thanks

@Qalex91 Any reason why you would not choose an off the shelf linear actuator with the right specs? https://www.robotshop.com/en/actuators.html
If you really want to design your own, you’ll need a lead screw (and complete specs), gearing and the motor. The gear motor can only be chosen wit the lead screw.

Hi me and my team are planning to build a four legged wheel robot for harsh environments and unstructured terrains which can carry a load of 100 kg. We need a rotating actuator for this purpose. What will be the best option to use? Any preferable options currently available?

@QShaikh Welcome to the community. You wrote “four legged wheel robot” - can you provide a drawing showing the configuration? Note that a 100Kg payload is really impressive and will take a LOT of torque to support. Boston Dynamic’s BigDog could support up to 150Kg:

The design is still in the process. Stuck on choosing the actuator since a while now.