Motors & Wheels
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flagWhat you'll discover
- arrow_forwardDrive a robot using only two motor power sliders
- arrow_forwardPredict the path from any left/right power combination
- arrow_forwardMake the robot spin in place using opposite motor powers
- arrow_forwardExplain the differential drive equations in plain words
Steering without a steering wheel
Most small robots have no steering wheel at all. Instead they use differential drive: two wheels, each with its own motor. Equal power on both sides drives the robot straight. Give the left wheel more power and the robot curves right; more power on the right curves it left.
It feels strange at first, but you already know this trick — it is exactly how you steer a wheelchair or row a boat with two oars.
The math behind the motion
Engineers describe differential drive with two simple equations. Forward speed is the average of the wheel speeds: v = (vL + vR) / 2. Turning rate depends on the difference: w = (vR - vL) / L, where L is the distance between the wheels.
Set both sliders to +80 and the difference is zero — no turning, pure forward motion. Set left to +50 and right to +100, and the difference makes the robot arc smoothly to the left.
The tank turn
Here is the party trick: set the left motor to +60 and the right motor to -60. The average speed is zero, so the robot goes nowhere — but the difference is huge, so it spins on the spot like a top. This is called a tank turn or pivot turn, because tanks steer the same way.
Pivot turns are gold in robot competitions: they let a robot turn around in a tight maze corner without needing any extra space.
From sliders to real robots
On real robots, those slider values become PWM signals — rapid on-off pulses that control how much power each motor receives. A value of 100 means full power; 50 means power half the time.
Robots from vacuum cleaners to Mars rovers use differential steering because it is simple, cheap and precise. With only two motors and clever code, a robot can trace any path you can imagine — watch the trail line in the simulation prove it.