Level 2 — Actuators & Motion
Motors, torque, speed, and real movement
Actuators are the robot’s muscles. This level explains how motion is produced, how to choose motors correctly, and how to think in torque, speed, and load — not in “it spins, so it works”.
The same control code behaves differently if the actuator choice is wrong. Hardware defines what motion is physically possible.
Actuator types
- DC motor — simple, fast, needs feedback for precision
- Servo — built-in position control, limited range (typical), easy integration
- Stepper — discrete steps, strong low-speed torque, can skip steps under load
- BLDC — efficient, high power density, requires proper driver/control
Torque and speed
Torque is rotational force. Speed is how fast the shaft rotates. In most practical systems, increasing torque reduces speed, and vice versa.
- High speed + low torque → lightweight, fast motion
- Low speed + high torque → heavy loads, precise force delivery
- Gear reduction converts speed into torque
Gear reduction concept
A gearbox (reduction) decreases output speed and increases output torque. This is the core mechanism behind practical robotics motion.
- More reduction → more torque, less speed
- Too much reduction → slow response, higher friction
- Too little reduction → motor stalls under load
Stall and overload
A stalled motor draws maximum current and heats rapidly. Stall is one of the most common reasons robots fail electrically.
- Design to avoid stall in normal operation
- Use gearing and correct motor sizing
- Protect the system with current limits and fuses
Motion quality
Real robots require smooth motion, not just “on/off”. Mechanical inertia and friction demand controlled acceleration.
- Ramp up / ramp down reduces stress and slipping
- Closed-loop speed control improves stability
- Encoders enable precise velocity and position control
What you should know after Level 2
- how to choose actuator type for a task
- how torque and speed trade off
- why gear reduction is essential
- what stall means and why it is dangerous
- why smooth motion matters for control
Next: Level 3 — Power & Electronics