Experiment 8: Study of Automated guided vehicle.

Hardware Setup:

This is a robotic vehicle controlled by 68HC11 micro controller activity board. It has a 32KB memory, 21 analog input channels, 9 digital input channels, 9 digital output channels, it drives 4 DC motors and 6 RC servo motors. It has a 16X2 LCD display and a buzzer for producing beep. The program is downloaded to the board through a RJ11 cable.

Sensors used:

There are different sensors used in this vehicle.

Sharp proximity sensor: As the name suggest it is a sensor which is used to inform the micro controller when an object comes close proximity to it. It is an IR transceiver sensor which operates in 5V DC. And it gives analog voltage corresponding to the distance of the object from it. It gives low voltage when the object is far away compare to a closer object. It should be connected any one of the analog input channels of the board.

Touch switch sensor: it is a digital sensor which informs the controller when the front side of the robot bumped to some other object. Actually it is a push-to-ON (push button) switch which is used as a sensor. When the vehicle collides with an object the switch is pressed and it sends a high digital pulse to the controller. It should be connected to the digital input channel of the board.

IR reflector: there are three IR reflector sensors placed at the bottom of the chassis. They are used for the track detection purpose.  These are analog sensors so they should be connected to the analog channels of the board.

Software:

The programming IDE is called Interactive C (IC). It is similar to C with some more inbuilt function. The syntax is also same as C and it support all C data types. Some of the hardware interactive library functions and their syntax is listed below:

motor (motor #, speed): this function is used to rotate the motor. Here the motor no. varies between   0-3 and the speed varies between 0-100.

sleep(float x): Gives a delay to the program. And x is in second.

Start_button(): Returns 1 when start button is pressed.

digital(port#): Returns 1 if the port is connected to 5v and returns 0 when the port is connected to 0V. the return type is integer

analog(port #): Returns the value between 0-255 corresponding to analog voltage 0-5V. the return     type is integer.

beep(): Causes a beep sound.

off(motor #): Turns off the motor specified.

ao(): urns all motor ports off. 

Connection Procedure:

Double click on the Interactive C shortcut on the desktop. Then the following window will come

Click on AX-11 board type

Select the com port, and click on connect now.

Then click on "Download firmware."

Again select the com port and click on "Download firmware".

Connect the RJ11 connector between computer serial port and the vehicle board. And then click on "Next".

Look at the SER LED, if it is blinking click on "Yes, it’s blinking". If not click on "Not blinking".

Turn OFF the power switch on the board and click on "Next".

Pick up the robot in hand because at this stage the motor will start rotating. Then first hold down the stop button and then turn ON the power and click on "Next".

Look at the PWR LED and Batt LED if both are then click on "Both lights off" otherwise click on the tab as per  the light conditions.

Now the firmware starts downloading to the board. Firmware contains necessary library files for the controller.

This is the interactive window for testing the connection. You write the command at the white bottom area it will reflect over the grey area, if the code is correct it will return zero otherwise a wrong message.

For the code printf(“hello world”) it executes successfully and returned 0, and for the command hello it returned an error message undeclared symbol hello.

Then go to file and click on new. A new tab will open where you can write the program and download it to controller.

Write the program, save it and download it to the micro controller. Here is some sample programs

Sample program:

Code for forward movement of vehicle:

#define speed 50

void main()

{

    ao();

    printf("press start\n");

    start_press();

    while(!stop_button())

      {

        motor(0,speed);

        motor(1,speed);

        //sleep(2.0);

    }

}

Code for backward movement:

#define speed 50

void main()

{

    ao();

    printf("press start\n");

    start_press();

    while(!stop_button())

      {

        motor(0,-speed);

        motor(1,-speed);

        //sleep(2.0);

    }

}

Code to read sharp sensor value:

void main()

{

    while(1)

      {

        int value;

        Value=analog(22);

        printf("value=%d\n",value);

        sleep(1.0);

    }

}

Code to read track IR reflector sensor value:

void main()

{

    while(1)

      {

        printf("L=%d M=%d R=%d\n",analog(29),analog(25),analog(19));

               sleep(2.0);

    }

}

Code to test touch switch sensor:

void main()

{

    while(1)

      {

        printf("L=%d R=%d\n",digital(15),digital(10));

               sleep(2.0);

    }

}

Task to Solve:

1. write a program to drive the vehicle so that its path would draw a SQUARE
2. write a program to drive the vehicle in its own path avoiding the collision with other objects.
3. write a program to drive the vehicle to follow the white line