Motor
If a robot wants to turn left, what should it do? Is spinning both wheels at the same time enough?
Think of a tank — it has no front and back wheels, only two tracks. To turn left, it slows down or stops the left track while the right track goes full speed.
To spin 360°, a tank runs its left track backwards and its right track forwards. Because the two sides turn in opposite directions at the same time, the tank spins in place — it doesn’t move! This technique, called “differential drive”, is used in robots too.
Robots mostly use DC motors or servo motors. DC motors are chosen for speed control, servo motors for precise angle control. In two-wheeled robots, “differential drive” sets the speed of each wheel separately to go straight, turn, or spin in place.
1️⃣ Go straight → Left motor: +100, Right motor: +100 (equal, forward) 2️⃣ Turn left → Left motor: +50, Right motor: +100 (right is faster) 3️⃣ Sharp left → Left motor: -100, Right motor: +100 (opposite directions) 4️⃣ Stop → Left motor: 0, Right motor: 0 5️⃣ Go backwards → Left motor: -100, Right motor: -100
On a bike you turn the handlebars to turn. But you can’t spin in place — you can’t do a 360° without getting off. A robot with two separate motors can, by controlling each wheel on its own!
Put your hands on the table, press your left palm down while pushing your right palm forward — what does your body do? That’s exactly how a robot turns left! Now move both hands in opposite directions — that’s a 360° spin!
Research: how do drones (quadcopters) move? They have four propellers but no wheels. What do they do to turn left?
What should a robot do to turn left?