Which Motors Are Used in Robotics? Key Types Explained

Brushed DC motors are the oldest and most straightforward motor technology. They operate by using physical brushes that make contact with a rotating commutator to switch the magnetic field.

• Best for: Low-cost toys, simple mobile robots, and applications where cost is the primary factor.
• Pros: Very inexpensive, easy to control (simply apply voltage to spin), and requires minimal electronics.
• Cons: The friction from the brushes creates heat, electrical noise (EMI), and physical wear [1]. They require frequent maintenance if used in high-duty cycles.

In robotics, these are often used with a gearhead to increase torque, as raw DC motors typically spin too fast with very little “pushing” power.

BLDC motors eliminate the physical brushes, replaced by electronic commutation. This shift allows them to be more efficient, quieter, and significantly more durable.

• Best for: Drones, high-speed mobile robots, and electric vehicles.
• Pros: High power-to-weight ratio, long lifespan, and high efficiency. As noted by Renesas Electronics, they are essential for long-running industrial applications where maintenance-free operation is a priority.
• Cons: Requires a complex electronic speed controller (ESC) and sensors (like Hall effect sensors) to track rotor position [2].

Stepper motors move in discrete “steps” (typically 1.8 degrees per step). By pulsing the motor a specific number of times, you can command it to move to an exact position without needing a feedback sensor.

• Best for: 3D printers, CNC machines, and camera gimbals.
• Pros: Excellent for precise positioning and high holding torque at low speeds. They are significantly more repeatable than standard DC motors [1].
• Cons: High power consumption (they draw current even when standing still) and low efficiency at high speeds. If the load is too heavy, the motor can “skip” steps, losing its position.

A servo motor is not necessarily a “different” kind of motor, but rather a system. It combines a motor (usually DC or brushless), a gear train, and a feedback sensor (potentiometer or encoder) to allow for extremely precise angular control.

• Best for: Robotic arms, humanoid joints, and steering mechanisms.
• Pros: High precision and “closed-loop” feedback, meaning the motor knows if it hasn’t reached its target and will increase power until it does.
• Cons: Generally more expensive and can be bulky depending on the gear ratio required.

Advanced robotics often utilize specialized servos to mimic biological movement. To understand how these components differ in scale and complexity, you can read our comparison of Anthrobots vs. Humanoid Robots: Key Differences Explained.

While standard motors work on Earth, space exploration requires specialized hardware. These motors must operate in vacuums, endure extreme temperature swings, and resist radiation. For instance, the rovers on Mars use highly specialized BLDC motors with dry lubricants to prevent freezing in the Martian cold. You can explore more about these technologies in our guide on The Vital Role of Robotics in Space Exploration.

When evaluating motors, use the following formulas to narrow your search.

Calculation of Torque

Torque ($T$) is the measure of force ($F$) applied at a distance ($d$):
$T = F \times d$

If your robot arm needs to lift a 1kg load at the end of a 0.5-meter arm, the motor at the shoulder needs a minimum torque of 4.9 Nm (Newtons x meters), assuming 1kg = 9.8 Newtons [2].

The 1.5x Safety Factor Rule

Engineering communities on Reddit’s r/robotics frequently advise against “maxing out” motor specs. Always select a motor capable of producing at least 1.5 times the torque your calculations suggest. this accounts for friction, battery voltage drops, and unexpected payloads.

Action Plan for Selecting Motors

1. Define Movement: Do you need continuous rotation (wheels) or precise positioning (arm joint)?
2. Calculate Peak Load: Determine the heaviest object the robot will lift.
3. Apply Safety Factor: Multiply your required torque by 1.5.
4. Select Power Source: Ensure your battery can handle the stall current—the maximum current a motor draws when it is prevented from spinning.
5. Match Controller: Purchase a motor driver or ESC that matches the voltage and exceeds the continuous current rating of your motor.

Choosing the right motor is the difference between a functional machine and a pile of overheated electronics. By matching the mechanical requirements of your task to the specific strengths of brushed, brushless, stepper, or servo motors, you ensure your robotic system operates with both efficiency and longevity.