TETRIX Getting Started Guide. Harvester and Transporter Programming Guide (ROBOTC )

Transcription

1 Introduction: In this guide, the Ranger Bot will be programmed to follow a line, pick up an object using the harvester, and put the object into the transporter. It will also count the number of objects collected. This guide is for use with the ROBOTC programming language. Getting Started: 1. To start the program, type the Main Task function followed by an opening brace. task main() Defining Variables: 2. Declare five integer variables as seen in the code below. Beside each variable, there are two slashes (//) followed by what that variable is representing. These mark a comment. Notice that comments appear in green when code is typed into ROBOTC. Note: A comment is not part of the code that the NXT Brick will execute, but it helps the programmer by allowing the addition of notes to describe what has been done. int nvalue; int mvalue; int aposition; int bcounter; int mspeed; // light value // sonar value // servo arm position // touch sensor ball counter // motor speed 3. Type the Wait function and set it to wait 50 milliseconds to allow the robot to initialize motors and sensors. wait1msec(50); 4. Type the servo position command to initialize the position of the servo. This must be set to a value between 0 and 255, representing a position between 0 and 180. This is the servo s full range of motion. servo[servo1] = 140; 5. Type in the initial count for the variable that counts how many balls the robot has picked up with its harvester, which is zero at the beginning of the program. bcounter = 0; 6. Type in the initial motor speed. 7. Type the Wait function and set it to wait one second while the servo motor gets into position. 163

2 Extensions 8. Add an infinite While Loop to make the containing code execute forever. while(true) 9. Set the defined variables to a value and display them to the screen. a. Set the nvalue variable to the value of the light sensor and the mvalue variable to the value of the ultrasonic sensor. b. Use the NXT write to screen command to put them on the screen. This write to screen command requires three pieces of information, called parameters, in order to write both text and a variable to the screen: i. The line number. ii. The text (in quotations) which includes a display variable caller. Note: In this case, %d is the display variable caller. In the place of %d, an integer variable is displayed on the screen. iii. The variable name. This information is inside the brackets beside the command, separated by commas. 10. Below the text that is written on the screen, display a message that says Searching..." Because there is no variable being displayed, only two parameters need to be sent to the function: the line number and the text. nxtdisplaycenteredtextline(4, "Searching..."); 11. Display the bcounter variable on the NXT screen. Use the NXT write to screen command to put them on the screen. nxtdisplaytextline(6, "Ball Count: %d", bcounter); 12. The next few lines of code will decrease the motor speed as the target is being approached. Add a conditional statement so that if the ultrasonic sensor value is greater than 40, the mspeed variable will be set to 30, but if it is equal to or less than 30, the mspeed variable will be set to 15. if(sensorvalue[sonarsensor] > 40) else mspeed = 15; 164

3 Line Follower Code: 13. Add the line-following code that was created in Line Follower Extension Part 3. if(sensorvalue[lightsensor] < 60) motor[motord] = mspeed; else motor[motore] = mspeed; Grab an Object: 14. Add a conditional statement to check if the robot is within 23 cm of the object it is picking up. If the robot is within 24 cm of the object, display Found! on the robot screen and stop the motors. Add a Wait function to pause for one second to give the motors time to stop before the next action is executed. if(sensorvalue[sonarsensor] < 23) nxtdisplaycenteredtextline(4, Found! ); 15. Add a Move Servo command to move servo1 from its current position at 140 to a higher position of 25, and add a Wait function to pause for one second so that the servo has time to get into the position. servo[servo1] = 25; 165

4 Extensions 16. Add a While Loop to continue displaying the value of the light sensor and the sonar sensor until the touch sensor has been pushed by the ball. If the touch sensor has been pressed, then the value of the touch sensor, at that moment, would be 1; otherwise, the value of the touch sensor will be zero. Therefore, the condition for the While Loop statement would be to check if the touch sensor value is equal to zero in order to display the value of the light sensor and the sonar sensor on the NXT screen. To display the light and sonar sensor values to the screen, copy and paste the code in Step 9. while(sensorvalue[touch] == 0) 17. When the touch sensor is pressed, the robot breaks out of the While Loop. Increment the ball counter variable, which is bcounter, by 1. bcounter = bcounter + 1; 18. Type the Wait function to make the program pause for one second. 19. Now that the robot has obtained the ball, the robot should back up. In order to set motore and motord in the reverse direction, use the Motor function and assign a negative motor power to each motor. motor[motore] = -25; motor[motord] = -25; 20. Type the Wait function to make the program pause for 0.5 second. wait1msec(500); 21. Next, stop both motors using the Motor function. 166

5 22. Add a For Loop, which makes the arm servo move from its current position at 25 to a lower position of 140, waiting 10 milliseconds between each movement. for(aposition = 25; aposition < 140; aposition++) servo[servo1] = aposition; wait10msec(1); 23. Type the Wait function and set it to wait one second. End the Program: 24. Type a closing brace to end the conditional statement in Step Type a closing brace to end the infinite While Loop in Step Type a closing brace to end the program. Completed Code: task main() int nvalue; int mvalue; int aposition; int bcounter; int mspeed; // light value // sonar value // servo arm position // Touch sensor ball counter // Motor Speed wait1msec(50); // The program waits 50 milliseconds to initialize the light sensor. servo[servo1] = 140; // Initial startup of harvester position bcounter = 0; 167

6 Extensions Completed Code (continued): // wait for arm and gripper to get to position while(true) // Infinite loop nxtdisplaycenteredtextline(4, "Searching..."); nxtdisplaytextline(6, "Ball Count: %d", bcounter); /// Decrease speed as we approach target. if(sensorvalue[sonarsensor] > 40) else mspeed = 15; //// Line following Here; if(sensorvalue[lightsensor] < 60) // If the Light Sensor reads a value less than 60: motor[motord] = mspeed; // Motor D is run at a mspeed power level. // Motor E is run at a 0 power level. else // If the Light Sensor reads a value greater than or equal to 50: motor[motore] = mspeed; // Motor E is run at a mspeed power level. // Motor D is run at a 0 power level. //// Sonar ranging here; Stop at target distance, position gripper and arm. if(sensorvalue[sonarsensor] < 23) // Target sense distance (centimeters) 168

7 Completed Code (continued): nxtdisplaycenteredtextline(4, "Found!"); // update display // Motor E is off // Motor D is off // Pause for 1 second servo[servo1] = 25; // Raise Harvester while(sensorvalue[touch] == 0) // Wait for touch sensor to be pushed to count ball. bcounter = bcounter + 1; // increment ball count; // Back up - reverse motor[motore] = -25; motor[motord] = -25; wait1msec(500); // Motor E // Motor D // Motor E // Motor D for (aposition = 25; aposition < 140; aposition++) servo[servo1] = aposition; // Lower Harvester wait10msec(1); // wait a second for arm to come down. 169