PID Tutorials for Line Following

Let's Make Robots Robots
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Hey there guys. This post is outdated. Visit https://www.robotshop.com/letsmakerobots/node/39972 for the updated tutorial.Hello LMRians,In this writeup, I will try to create a tutorial for tuning your robot using PID to follow a line. This tutorial won’t go deep down into the details of PID and

This is a companion discussion topic for the original entry at https://community.robotshop.com/blog/show/pid-tutorials-for-line-following
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Pretty good tutorial. That

Pretty good tutorial. That reminds me that I need to dig into the PID a bit more to get some applications running.

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Thanks Lumi. Can’t wait to

Thanks Lumi. Can’t wait to see what you come up with!

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LOL, it will perhaps happen

LOL, it will perhaps happen this year :slight_smile: So many plans and so little time.

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Really good tutorial!

Hi

How behaves your robot in case of  90 degree angle? Radius of angle is 0.

Is the robot able to follow the line.

Best regards.

 

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Hello indrekm.A 90 degree

Hello indrekm.

A 90 degree turn is an extremely sharp turn. The PID parameters need to be tuned to near perfection in order to make a correct turn. But that is rather difficult. So, I suggest you set a 90 degree turn as a “special” case and work out a separate algorithm that varies from the PID routine. A simple “scan” left/right, “turn” left/right should do.

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Kp and Kd constants

Kp = 0.2 and Kd = 5 worked for me as constants!

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Stopping on a line?

I’m using this sensor for my senior project at my University and was wondering if you knew of a way to have the robot stop if it goes over a solid black line being read by all sensors at once?

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QTRSensorsRC qtrrc((unsigned char[]) { 14, 15, 16, 17, 18, 19} ,NUM_SENSORS, TIMEOUT, EMITTER_PIN);

My code is not running because of this line. it says-

Arduino: 1.8.9 (Windows Store 1.8.21.0) (Windows 10), Board: “Arduino/Genuino Uno”

LFR_QTR_TEST:21:1: error: ‘QTRSensorsRC’ does not name a type

QTRSensorsRC qtrrc((unsigned char[]) { 14, 15, 16, 17, 18} ,NUM_SENSORS, TIMEOUT, EMITTER_PIN);

^

LFR_QTR_TEST:21:61: error: expected unqualified-id before ‘,’ token

QTRSensorsRC qtrrc((unsigned char[]) { 14, 15, 16, 17, 18} ,NUM_SENSORS, TIMEOUT, EMITTER_PIN);

                                                         ^

LFR_QTR_TEST:8:22: error: expected unqualified-id before numeric constant

#define NUM_SENSORS 5 // number of sensors used

                  ^

D:\Arduino\Tests\LFR_QTR_TEST\LFR_QTR_TEST.ino:21:62: note: in expansion of macro ‘NUM_SENSORS’

QTRSensorsRC qtrrc((unsigned char[]) { 14, 15, 16, 17, 18} ,NUM_SENSORS, TIMEOUT, EMITTER_PIN);

                                                          ^

D:\Arduino\Tests\LFR_QTR_TEST\LFR_QTR_TEST.ino: In function ‘void loop()’:

LFR_QTR_TEST:47:18: error: ‘qtrrc’ was not declared in this scope

int position = qtrrc.readLine(sensors);

              ^

D:\Arduino\Tests\LFR_QTR_TEST\LFR_QTR_TEST.ino: In function ‘void manual_calibration()’:

LFR_QTR_TEST:88:5: error: ‘qtrrc’ was not declared in this scope

 qtrrc.calibrate(QTR_EMITTERS_ON);

 ^

LFR_QTR_TEST:88:21: error: ‘QTR_EMITTERS_ON’ was not declared in this scope

 qtrrc.calibrate(QTR_EMITTERS_ON);

                 ^

LFR_QTR_TEST:96:20: error: ‘qtrrc’ was not declared in this scope

   Serial.print(qtrrc.calibratedMinimumOn[i]);

                ^

LFR_QTR_TEST:103:20: error: ‘qtrrc’ was not declared in this scope

   Serial.print(qtrrc.calibratedMaximumOn[i]);

                ^

exit status 1
‘QTRSensorsRC’ does not name a type

This report would have more information with
“Show verbose output during compilation”
option enabled in File -> Preferences.