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How Do I Choose the Best Robot Motor?

Robots working on an automobile assembly line.
A DC motor can power a robot.
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  • Written By: Andrew Kirmayer
  • Edited By: Shereen Skola
  • Last Modified Date: 10 July 2014
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The motor used on a robot can depend on a number of factors. What the robot is being used to move, the power needed to do so, and the weight of the robot are all key considerations. Higher power motors require larger batteries, which are considerably heavier and increase the overall weight of robots. The major types of robot motor include continuous direct current (DC) motors as well as stepper and servo motors; each has distinct benefits and disadvantages depending on the robotics application. Voltage, current, speed, torque, and size are major considerations when choosing a motor to make a robot.

For choosing the best robot motor, DC motors are a popular choice because they can run off the power from typical robot batteries. There are many kinds of continuous DC motors to choose from. These robot motors, whether supplied with or connected by the builder to a gearbox, have enough power to support a machine weighing several hundred pounds. Depending on the robot’s torque requirements, gear reducing components might have to be installed which can consequently increase the weight and cost of the project.

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If a stepper motor is used with a robot kit, then it is not necessary to use gears to limit power consumption when the robot moves slowly. The motor moves in small increments, so motion that occurs under changing loads may not be sufficient unless additional circuits are added. Servo motors are another kind of robot motor and are typically the least expensive overall. Suitable for angular and rotational motions, they can be used on robots with grips and multi-jointed arms that pick up, move, and place objects. These motors can also be reconfigured for the addition of continuous rotation to the robot’s capabilities.

When choosing the best robot motor, it is important to know what voltage the motor is rated for. Most home-built robots require six to 24 volts, but if operated at any higher voltages, the motor will tend to overheat and stop working. The current the motor draws while operating is important as well as the stall current drawn when it stops rotating. The level of wattage and amount of heat it can withstand must also be considered, while the force of the robot motor, or torque, and its maximum speed also need to be known when building robots. Generally, the higher the torque rating in robotics, the larger and heavier a robot the motor can support.

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Discuss this Article

miriam98
Post 4

@SkyWhisperer - I understand the industrial application of the term, but when I think of robots, I think of the humanoid type machines that can walk and see.

There are already such machines out there, especially in Japan where companies like Honda have made their own walking robots that can climb steps.

I’m assuming that these machines would have to use a combination of all the different kinds of motors described here. I believe the servo motors would be suitable for arm and leg movements. And to get the robot to turn around (without losing balance) I think it would need a stepper motor to take small steps.

SkyWhisperer
Post 3

@allenJo - I owned a simple robot kit a few years ago. This was back when I dabbled in programming as a hobby and extended my interests into robotic technology.

I built a simple robot that had an arm which could be used to grip and move objects. The arm was powered by a simple servo motor, which if I recall used a couple of nine volt batteries.

I also used a simple programming language to send commands to the unit; the programs were on a computer with a cable which hooked up to the robot so that the commands could be sent. It was a neat project and gave me a taste of real world robotics.

allenJo
Post 2

@NathanG - Yeah, I think those robot cleaners use a simple DC voltage. They don’t need a whole lot of power to operate. I am thinking the voltage drawn would be comparable to what you would need to power a handheld vacuum cleaner. That’s as much power as I think you can deliver with such a small unit.

NathanG
Post 1

I’m willing to bet that the stepper motor is used in those robot vacuum cleaners they advertise on television. These are small vacuum cleaners with a very low profile so that they can get underneath tables and around corners and vacuum your carpet (or wood floor).

I am willing to call these cleaners robots because they do seem to possess some rudimentary intelligence, which is based more or less on its ability to sense obstacles in the way and turn around.

When it turns, it tends to do so in incremental sweeps, which is what a stepper motor would do. The vacuum robot also has to have some ability to remember where it’s vacuumed so that it knows when to stop.

This is not the function of the motor as such but is proof that some computer on board is acting as some sort of thinking machine.

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