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Autonomous Light Tracking Rover

Some light autonomy

Intermediate
by Ben

Introduction

Prerequisites

This project assumes you have completed the following guides:

For more information, check out the Student Page.

Goal

The focus of this project is the use of the Light Phidget. When completed, your rover will be able to turn itself towards the brightest light source in its field of view.

Parts Inventory


Rover Kit

Light Phidget (2)

Phidget Cable (2)
You will also need tape or dual lock to attach the Light Phidgets to your rover.

Hardware

  1. Begin with a fully assembled Rover Kit.
  2. Remove the Sonar Phidget.
  3. Mount the two Light Phidgets on an angle, facing outward as shown in the image. Mounting the Light Phidgets on an angle increases the field of vision of the robot.

Interpreting Data

To create an autonomous vehicle, the motor commands must be derived entirely from the onboard Light Phidgets. By measuring the difference between the light intensity each Light Phidget recieves, you can create a simple algorithm which will turn the rover towards the brighter side. A greater difference between the readings from the Light Phidgets will result in a larger magnitude of turning correction.


For example, in the image above, the left Light Phidget receives a greater share of light. With this input, the rover should turn to the left.

Software

Step 1: Setup

You will need to set up your four Phidgets. Code samples are provided bellow. For more assistance please see the flow chart to the right. 

    


public static void main(String[] args) throws PhidgetException {

    Net.addServer("", "192.168.100.1", 5661, "", 0);

    LightSensor leftLight = new LightSensor();
    LightSensor rightLight = new LightSensor();
    DCMotor leftMotors = new DCMotor();
    DCMotor rightMotors = new DCMotor();

    // TODO: Address Objects, Register for Events, Open Objects,
    //       Set Light Objects Data Interval to Min,
    //       Set DCMotor Objects Acceleration to Max

}


    

def main():

    Net.addServer("hub5000", "192.168.100.1", 5661, "", 0)

    leftLight = LightSensor()
    rightLight = LightSensor()
    leftMotors = DCMotor()
    rightMotors = DCMotor()
    
    # TODO: Address Objects, Register for Events, Open Objects,
    #       Set Light Objects Data Interval to Min,
    #       Set DCMotor Objects Acceleration to Max

main()    


    
    
static void Main(string[] args)
{
    Net.AddServer("", "192.168.100.1", 5661, "", 0);

    LightSensor leftLight = new LightSensor();
    LightSensor rightLight = new LightSensor();
    DCMotor leftMotors = new DCMotor();
    DCMotor rightMotors = new DCMotor();

    // TODO: Address Objects, Register for Events, Open Objects,
    //       Set Light Objects Data Interval to Min,
    //       Set DCMotor Objects Acceleration to Max
}

Step 2: Events

In your Illuminance Change Events, you will have to store the light value for use in your main loop. 

    


leftLight.addIlluminanceChangeListener(new LightSensorIlluminanceChangeListener() {
    public void onIlluminanceChange(LightSensorIlluminanceChangeEvent e) {
        System.out.println("Left Illuminance: " + e.getIlluminance());
        //TODO: Store illuminance for use in main loop
    }
});

rightLight.addIlluminanceChangeListener(new LightSensorIlluminanceChangeListener() {
    public void onIlluminanceChange(LightSensorIlluminanceChangeEvent e) {
        System.out.println("Right Illuminance: " + e.getIlluminance());
        //TODO: Store illuminance for use in main loop
    }
});



    

def onIlluminanceChangeLeft(self, illuminance):
    print("Illuminance Left: " + str(illuminance))
    # TODO: Store illuminance value for use in control loop

def onIlluminanceChangeRight(self, illuminance):
    print("Illuminance Right: " + str(illuminance))
    # TODO: Store illuminance value for use in control loop


    


private static void Left_IlluminanceChange(object sender, LightSensorIlluminanceChangeEventArgs e)
{
    Console.WriteLine("Illuminance Left: " + e.Illuminance);
    // TODO: Store illuminance for use in main loop
}
private static void Right_IlluminanceChange(object sender, LightSensorIlluminanceChangeEventArgs e)
{
    Console.WriteLine("Illuminance Right: " + e.Illuminance);
    // TODO: Store illuminance for use in main loop
}

Step 3: Main Loop

In your main loop, you will use the illuminance values to move your motors. 

    


//previous code above ...

while(programIsRunning) {
    //TODO: define programIsRunning at the top of main
    //TODO: Update Motors Target Velocity based on illuminance values

    if (System.in.available() > 0) {
        System.out.println("Ending Program");
        programIsRunning = false;
    }

    Thread.sleep(50) //TODO: determine if this sleep time is adequate
}

//TODO: Close Phidgets before program exits



    


def main():

    #previous code above ...
    
    try:

        while True:
            #TODO: Update Motors Target Velocity based on illuminance values
            time.sleep(0.05) #TODO: determine if this sleep time is adequate
        
    except KeyboardInterrupt:
        print("Ending Progam")

    # TODO: Close Phidgets

main()


    


//previous code above ...

while (programIsRunning)
{
    //TODO: define programIsRunning at the top of main
    //TODO: Update Motors Target Velocity based on illuminance values

    if (System.Console.KeyAvailable)
    {
        Console.WriteLine("Ending Program");
        programIsRunning = false;
    }

    System.Threading.Thread.Sleep(20); //TODO: determine if this sleep time is adequate
} 

// TODO: close Phidgets

Conclusion

You now have the beginnings of an autonomous light tracking rover! Through this project you have learned the basics of a Light Phidget. You have learned by tracking the intensity of light between two sensors, you can change the direction of the rover.

Next Steps

Next, try adding additional autonomous functionality to the rover like following a light source.

Or check out our other Rover Projects:

Have you made an autonomous rover? We'd love to hear about it at education@phidgets.com