The three Servo Motors give your robot the ability to move. If you use the Move block in the LEGO MINDSTORMS NXT software to program your motors, the two motors will automatically synchronize, so that your robot will move in a straight line.

Built-in Rotation Sensor
Each motor has a built-in Rotation Sensor. This lets your control your robot’s movements precisely. The Rotation Sensor measures motor rotations in degrees or full rotations [accuracy of +/- one degree]. One rotation is equal to 360 degrees, so if you set a motor to turn 180 degrees, its output shaft will make half a turn.

The built-in Rotation Sensor in each motor also lets you set different speeds for your motors [by setting different power parameters in the software]. Try running the motors at different speeds.

Test it!
Test the built-in Rotation Sensor’s ability to measure distance:

1. Connect a motor to the NXT
2. Select the VIEW submenu on the NXT
3. Select the Motor Rotations icon.
4. Select the port where you have connected the motor
5. Attach a wheel to the motor and measure the rotations as you roll the wheel along the floor