Motor Control

Motor control is the first programming skill students need to master, because every movement starts here. I always tell my students: before you try anything fancy with sensors, make sure your robot can drive predictably and repeatably.

The EV3 motors can be controlled in several ways:

• Power/Speed control – set a motor to run at a certain speed indefinitely. Good for simple forward/backward movement.
• Rotation control – move the motor for a specific number of degrees or rotations. Essential for precise turns or mechanism control.
• Timed movement – run the motor for a fixed duration. Useful for quick tests, but less reliable for precision.
  
  

One thing I always teach my students early is the difference between spin, pivot, and swing turns:

• Spin Turn – both wheels move in opposite directions, making the robot rotate in place. This is the fastest way to turn sharply and is ideal for tight corners on the field.
• Pivot Turn – one wheel is stationary while the other moves, causing the robot to rotate around the stationary wheel. Pivot turns are more stable than spin turns but take up more space. They’re useful when you need a precise turn without the robot swinging out too much.
• Swing Turn – one wheel moves slower than the other, or one is stationary while the other moves, resulting in an arcing turn. Swing turns are smooth and are good for gradual curves or adjusting alignment without overshooting.
  
  

When I teach these, I have students try each type of turn manually with the same angle — 90 degrees, for example — and observe how the robot moves. This helps them see the different behaviors of spin, pivot, and swing turns firsthand, and decide which type of turn is most appropriate for a given situation on the field. It also encourages them to think about space management and smoothness of motion, which are important when planning paths or navigating obstacles.

Task 1: Forward Drive
Program the robot to drive forward 50 cm using motor rotations, and repeat it three times. Observe whether the robot travels the same distance each time.

Task 2: Simple Turn
Program the robot to rotate in place 90 degrees using a spin turn. Repeat using a pivot turn and a swing turn. Compare consistency, speed, and space used.

Task 3: Combined Movements
Create a simple routine where the robot drives forward, turns, and drives again. Encourage students to break the program into small steps and test each one before combining them.

 

Tip: Always start with a “bare drive base” — no attachments — so students can see how motor control behaves without extra variables.