Building a tank

In order to build a tank, a physical setup with two motors is required. Here is a simple design consisting 1 touch sensor, 1 colour sensor, and 2 large tacho motors for an EV3. It is designed using the LDD (Lego Digital Designer), and its download is available.

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Remarks:

For motors, please connect output/motor port B to the left motor, and output/motor port C to the right motor.

For sensors, please also connect input/sensor port 1 to the touch sensor and input/sensor port 2 to the colour sensor.

We have to use two Motor class instance to achieve driving an ev3dev tank. To begin with, we will import two following classes:

import org.ev3dev.hardware.motors.Motor;
import org.ev3dev.hardware.ports.LegoPort;
							

With the following code snippets, we will create two Motor instance to drive the tank.

/*
LegoPort.OUTPUT_* assigns the Motor to a specific port on the EV3.

Available output constants are:

- LegoPort.OUTPUT_A -> Assigns to Port A
- LegoPort.OUTPUT_B -> Assigns to Port B
- LegoPort.OUTPUT_C -> Assigns to Port C
- LegoPort.OUTPUT_D -> Assigns to Port D
*/
Motor leftMotor = new Motor(new LegoPort(LegoPort.OUTPUT_B));
Motor rightMotor = new Motor(new LegoPort(LegoPort.OUTPUT_C));
							

We will set the speed of two motors using the following method:

//Speed ranges from -100 to 100
//Negative speed makes the motor to runs backwards
leftMotor.setSpeed_SP(100);
rightMotor.setSpeed_SP(100);
							

Next, we will tell the two motors to run forward! And wait for 5 seconds (5000 ms).

leftMotor.runForever();
rightMotor.runForever();
try {
	Thread.sleep(5000); //Tell the thread to sleep 5000 ms
} catch (InterruptedException ignore){} //We don't need to handle it currently
							

Nevertheless, we will tell the two motors to run backwards! And wait for 5 seconds (5000 ms).

//Negative speed makes the motor to runs backwards
leftMotor.stop(); //Stop it first
rightMotor.stop();

leftMotor.setSpeed_SP(-100);
rightMotor.setSpeed_SP(-100);

leftMotor.runForever(); //Restart
rightMotor.runForever();
try {
	Thread.sleep(5000); //Tell the thread to sleep 5000 ms
} catch (InterruptedException ignore){} //We don't need to handle it currently
							

Turn left! And wait for 5 seconds!

leftMotor.stop(); //We have to stop it first
leftMotor.setSpeed_SP(-100); //Negative speed means let the motor runs in a reverse direction
leftMotor.runForever(); //Restart it!
try {
	Thread.sleep(5000);
} catch (InterruptedException ignore){}
							

Turn right! And wait for 5 seconds!

leftMotor.stop();
leftMotor.setSpeed_SP(100); //Set back to positive speed to let the motor to run forward
leftMotor.runForever(); //Restart

rightMotor.stop();
rightMotor.setSpeed_SP(-100); //Let the motor to run backwards
rightMotor.runForever(); //Restart
try {
	Thread.sleep(5000);
} catch (InterruptedException ignore){}
							

Finally, we stop it.

leftMotor.stop();
rightMotor.stop();
							

You have completed a simple task to drive a tank! Here's the full example.

/*
LegoPort.OUTPUT_* assigns the Motor to a specific port on the EV3.

Available output constants are:

- LegoPort.OUTPUT_A -> Assigns to Port A
- LegoPort.OUTPUT_B -> Assigns to Port B
- LegoPort.OUTPUT_C -> Assigns to Port C
- LegoPort.OUTPUT_D -> Assigns to Port D
*/
Motor leftMotor = new Motor(new LegoPort(LegoPort.OUTPUT_B));
Motor rightMotor = new Motor(new LegoPort(LegoPort.OUTPUT_C));

//
// Set speed to 100 (Forward, Max Speed)
//

leftMotor.setSpeed_SP(100);
rightMotor.setSpeed_SP(100);

//
// Run Forward
//
							
leftMotor.runForever();
rightMotor.runForever();
try {
	Thread.sleep(5000); //Tell the thread to sleep 5000 ms
} catch (InterruptedException ignore){} //We don't need to handle it currently

//
// Run Backwards
//

//Negative speed makes the motor to runs backwards
leftMotor.stop(); //Stop it first
rightMotor.stop();

leftMotor.setSpeed_SP(-100);
rightMotor.setSpeed_SP(-100);

leftMotor.runForever(); //Restart
rightMotor.runForever();
try {
	Thread.sleep(5000); //Tell the thread to sleep 5000 ms
} catch (InterruptedException ignore){} //We don't need to handle it currently

//
// Turn Left
//

leftMotor.stop(); //We have to stop it first
leftMotor.setSpeed_SP(-100); //Negative speed means let the motor runs in a reverse direction
leftMotor.runForever(); //Restart it!
try {
	Thread.sleep(5000);
} catch (InterruptedException ignore){}

//
// Turn Right
//

leftMotor.stop();
leftMotor.setSpeed_SP(100); //Set back to positive speed to let the motor to run forward
leftMotor.runForever(); //Restart


rightMotor.stop();
rightMotor.setSpeed_SP(-100); //Let the motor to run backwards
rightMotor.runForever(); //Restart
try {
	Thread.sleep(5000);
} catch (InterruptedException ignore){}

//
// Stop both motors
//

leftMotor.stop();
rightMotor.stop();