Three motor families dominate robot drivetrains: brushed DC gearmotors, brushless motors and stepper motors. Each is the right answer for some robots and a frustrating one for others. This guide compares them on the things that matter for driving wheels: torque at low speed, efficiency, control, drivers, noise and cost.
Brushed DC gearmotors
The classic choice: a DC motor with carbon brushes and a commutator, almost always paired with a gearbox. Apply a voltage and it turns; reverse it and it turns the other way.
- Strengths: simple, cheap drivers (an H-bridge with PWM); smooth torque at low speed; behaviour that follows the simple straight-line model in our datasheet guide; huge choice of sizes with built-in encoders.
- Weaknesses: brushes wear out over thousands of hours; brush sparking produces electrical noise that disturbs sensors and radios (see the suppression capacitors in our capacitor guide); gearbox noise and backlash.
- Best for: hobby, educational and research robots, and small commercial robots where cost and simplicity matter.
Brushless DC (BLDC) motors
Brushless motors switch their windings electronically instead of with brushes. They need a driver (an ESC or, better for robots, a field-oriented control (FOC) driver) that knows the rotor position, from Hall sensors, an encoder or estimation.
- Strengths: high efficiency and power density; no brushes to wear, so long life and low noise; excellent for high speed. Hub motors (a brushless motor built into the wheel) remove the gearbox entirely, as in hoverboards and many delivery robots.
- Weaknesses: the driver is more complex and more expensive; hobby drone ESCs are designed for propellers and give poor control at low speed and standstill. Smooth torque at near-zero speed, which a wheeled robot needs, requires a sensored FOC driver.
- Best for: heavier and faster robots, long-life commercial platforms, and quiet operation, with a proper FOC driver.
Stepper motors
Steppers move in fixed steps (typically 200 per revolution, subdivided further by microstepping drivers) and hold position without feedback.
- Strengths: precise open-loop positioning; high holding torque at standstill; cheap, standard sizes (NEMA 17 and 23) and drivers.
- Weaknesses: torque falls steeply as speed rises; if the load exceeds the available torque, the motor silently misses steps and the controller no longer knows where it is; they draw full current even when holding still, which wastes battery and makes them hot; they can resonate and vibrate at certain speeds.
- Best for: slow, light robots and positioning mechanisms (lifts, pan-tilt heads, linear stages). For drive wheels, only small, slow, light robots on flat floors, ideally with closed-loop steppers that add an encoder.
Side by side
| Brushed DC gearmotor | Brushless (FOC driver) | Stepper | |
|---|---|---|---|
| Driver complexity | low | high | low to moderate |
| Efficiency | moderate | high | low (current flows even at rest) |
| Torque near zero speed | good | good with sensored FOC | excellent when holding |
| Torque at high speed | falls linearly | good | falls steeply |
| Position without an encoder | no | no | yes, until steps are missed |
| Lifetime limit | brushes, gearbox | bearings | bearings |
| Electrical noise | high (brushes) | low to moderate | moderate |
| Cost | low | moderate to high | low |
A note on smart servos
Smart servo actuators combine a motor, gearbox, encoder and controller in one housing, communicating over a serial bus. Small robots such as the TurtleBot3 drive their wheels with them. They save a lot of integration work, at a higher cost per watt and with power limited to small platforms.
How to choose
- Start with the requirement: torque, speed and power from our motor sizing guide or the calculator.
- Small or medium robot, moderate duty, tight budget: brushed DC gearmotors with encoders.
- Heavy, fast, long-running or quiet robot: brushless, with a sensored FOC driver, or hub motors.
- Slow, light robot or a positioning mechanism: steppers, ideally closed-loop.
- Plan the control loop: brushed and brushless drive motors need closed-loop speed control from encoders, covered in closed-loop motor speed control.
