Move Forward

Blocks

javaScript

//Set motor power

move(50, 50);

//continue for 3 seconds

await gofor(3);

// Reset power to zero

stop();

Left and Right motors have equal, and positive power

Move Backward

Blocks

javaScript

//Set motor power

move(-50, -50);

//continue for 3 seconds

await gofor(3);

// Reset power to zero

stop();

Left and Right motors have equal, and negative power

Left Turn

Blocks

javaScript

//Set motor power

move(-50, 50);

//continue for 3 seconds

await gofor(3);

// Reset power to zero

stop();

Differential power (left power - right power) is negative

Right Turn

Blocks

javaScript

//Set motor power

move(50, -50);

//continue for 3 seconds

await gofor(3);

// Reset power to zero

stop();

Differential (left - right) power is positive

Following a dark line

Blocks

javaScript

while (true)

{

// Must read inputs in the loop for latest status

// readInputs() also needs await keyword

    await readInputs();

    if( irLeft() < 50)

    {

        move(-50, 50);

    }

    else if ( irRight() < 50)

    {

        move(50, -50);

    }

    else

    {

        move(50, 50);

    }

}

Adjust the power to move faster.

Adjust the differential power to get sharper turns

Navigating the T-junction

Blocks

javaScript

while (true)

{

   // Must read inputs in the loop to get the latest status

   // readInputs() also needs await keyword

    await readInputs();

    // If BOTH sensors on the line, it is a T-junction

    if ( ( irLeft() < 50 ) && ( irRight() < 50 ) )

    {

         TLeft();  

    }

    // Check if left sensor is on or near the line

    else if ( irLeft() < 50 )

    {

        move(-40, 70);

    }

    // Check if right sensor is near the line

    else if (irRight() < 50)

    {

        move(70, -40);

    }

    // Otherwise keep going straight

    else

    {

        move(100, 100);

    }

}

// Function to handle T-junction followied

// by line seek to the left

async function   TLeft()

{

     move(20, 20);

     await gofor(.2);

      while( irRight() <  50 )

      {

         move(-40, 40);

         // We must get the latest input state

         // before the next loop iteration

         await readInputs();

      }

}

Adjust the power to move faster and get sharper turns.

Line following with Sensor Array and PID control algorithm

Blocks

javaScript

// PID Control example with RoboSensei IR sensor array

var kp = 5;

var ki = 5;

var kd = 3;

var P = 0;

var I  = 0;

var D = 0;

var prevError = 0;

var correction = 0;

var lp = 70; // left power

var rp = 70; // right power

var error = 0;

while (true)

{

   // Must read inputs in the loop to get the latest status

   // readInputs() also needs await keyword

   await readInputs();

   error = irArrayErrorGet();

   if (error == 255)

   {

     tprint('oops! out of line!')

   }

    P = error;

    I = I + error;

    D = prevError - error;

    prevError = error;

    correction = kp * P + ki * I + kd * D;

    move(lp - correction, rp + correction);

}

Google / checkout wikipedia to learn more about PID control algorithms. Your air conditioner will be using this algorithm.

Experiment with tuning kp, ki, and kd to improve the line tracking performance. Start with slow speed, slowly increase the speed and tune the control loop.

API

Use notes

 ir8Array()

var sensorArray = ir8Array();

Returns an array of 8 integers whose value is between 0 (black color)  and 255(white color)

ir8Byte()

var sensorByte = ir8Byte();

Returns an integer, whose least significant byte represents a 1/0 status of each sensor based on threshold value of 100.

irArrayErrorGet()

var error = irArrayErrorGet()

This function will return an error value based on the detected sensor values.

This is a convenience function. You may want to write your own function.

This function return the following values:

In the following table ‘x’ (don’t care) means value does not impact the returned value. This could be a 0 or 1.

API

Use notes

await readInputs()

usage: await readInputs();

This function needs to be called before using sensors in the code. In case of loops, where sensor is used; call this at the beginning, inside the loop.

move(powerLeft, powerRight)

usage : move(powerLeft, powerRight);

powerLeft: left motor power 0 - 100

powerRight: right motor power 0 - 100

await movefor(powerLeft, powerRight, timeSeconds)

usage: await movefor(powerLeft, powerRight, timeSeconds);

powerLeft: left motor power 0 - 100

powerRight: right motor power 0 - 100

timeSeconds: time in seconds (decimal number)

Example: await movefor(20, 20, 2);

await delay(timeSeconds)

await gofor(timeSeconds)

Usage: await  delay(timeSeconds);

Usage: await  gofor(timeSeconds);

timeSeconds: time in seconds (decimal number)

stop()

Usage: stop()

Stops the robot by applying zero power to left and right motors. Same as move(0,0);

irLeft()

Usage: irLeft();

Returns the value of the LEFT IR sensor

irRight()

Usage: irRight()

Returns the value of the RIGHT IR sensor

distance()

Usage: distance();

Returns value of distance sensor in mm.

bumperLeft()

bumperRight()

Xplorer ONLY

Usage:

bumperLeft();

bumperRight()

Returns true : bumper is hit; false: bumper not hit

ledon()

ledoff()

Xplorer ONLY

Usage:

ledon(ledId);  ---> ledon(1);

ledoff(ledId;  ----> lefoff(1);

Red: 0, Yellow: 1, Green: 2, Left: 3, Right: 5

tprint(text)

Usage: tprint(‘text’);

Prints text to the debug console located at the bottom of the  the javascript window

You can also print sensor values.

Example: tprint( ‘Distance: ’ + distance() ); will print distance sensor value

Caution: tprint command severely impacts the robot performance, hence should not be used in loops where high performance sensor reading and code execution is required for example in a line follower loop. Generally only use this for debugging purposes.

rgbleft()

rgbright()

mBot ONLY

Usage: rgbleft(rValue, gValue, bValue);  rgbright(rValue, gValue, bValue); 

Controls the RGB LEDs on mBOT.

rValue, gValue, bValue: 0 to  255

Sample code to blink left RGB LED:

while(true)

{

 rgbleft(255, 0, 0);

 await delay(1);

 rgbleft(0,0,0);

 await delay(1);

}