Line Follower - How to detect 90 degree turns with 2 color sensors?
I'm building a line follower with EV3 lego kit as a school project. To stay on the line I'm using PID regulator which uses difference between 2 color sensors on the front for calculating error (sensor read ranges from about 20 on black to 200 on white). It looks something like this:
The code I wrote works pretty well for smooth turns, even the sharp ones - but if the turn is a straight 90 degree angle something like this happens:
- Robot starts the turn
- It's not turning fast enough and both sensors end up on the black line
- Error falls to zero as both sensors are reading same value from black
- As the error is zero the robot goes straight and looses the line
I can manage make those turns by slowing speed and increasing integral and differential constants, but that makes control too aggressive and then it bounces left-right a lot, sometimes making one turn takes like 20 seconds before it manages to bounce like that to the straight line.
Any tips or tricks I could use to improve my Line Follower to deal better with those turns and overall?
Here is my code on GitHub written with Python API for ev3dev.
python
asked Nov 16 '18 at 19:36
StormwakerStormwaker
356
|
show 3 more comments
I'm building a line follower with EV3 lego kit as a school project. To stay on the line I'm using PID regulator which uses difference between 2 color sensors on the front for calculating error (sensor read ranges from about 20 on black to 200 on white). It looks something like this:
The code I wrote works pretty well for smooth turns, even the sharp ones - but if the turn is a straight 90 degree angle something like this happens:
- Robot starts the turn
- It's not turning fast enough and both sensors end up on the black line
- Error falls to zero as both sensors are reading same value from black
- As the error is zero the robot goes straight and looses the line
I can manage make those turns by slowing speed and increasing integral and differential constants, but that makes control too aggressive and then it bounces left-right a lot, sometimes making one turn takes like 20 seconds before it manages to bounce like that to the straight line.
Any tips or tricks I could use to improve my Line Follower to deal better with those turns and overall?
Here is my code on GitHub written with Python API for ev3dev.
python
asked Nov 16 '18 at 19:36
StormwakerStormwaker
356
Do you have access to the absolute values in addition to their relative values?
– Acccumulation
Nov 16 '18 at 19:42
@Acccumulation If you mean absolute values from each sensor then yes - r1 variable holds read from left and r2 from right.
– Stormwaker
Nov 16 '18 at 19:43
When it turns, does it continue forward motion, or does it just pivot? And is more sensors an option?
– Acccumulation
Nov 16 '18 at 19:53
@Acccumulation It turns slightly to the direction it was supposed to turn, because of the integral part, If I set integral high enough it can even return to the line sometimes, but other times it will just start making circles without reaching the line. I can only use 2 sensors.
– Stormwaker
Nov 16 '18 at 20:02
It might help to draw a diagram for the right angle case. When you say that you end up with both sensors on the line, I take it that if you start going north and then the line turns east, the right sensor is on the line going east and the left sensor is on the line going north?
– Acccumulation
Nov 16 '18 at 20:08
|
show 3 more comments
I'm building a line follower with EV3 lego kit as a school project. To stay on the line I'm using PID regulator which uses difference between 2 color sensors on the front for calculating error (sensor read ranges from about 20 on black to 200 on white). It looks something like this:
The code I wrote works pretty well for smooth turns, even the sharp ones - but if the turn is a straight 90 degree angle something like this happens:
- Robot starts the turn
- It's not turning fast enough and both sensors end up on the black line
- Error falls to zero as both sensors are reading same value from black
- As the error is zero the robot goes straight and looses the line
I can manage make those turns by slowing speed and increasing integral and differential constants, but that makes control too aggressive and then it bounces left-right a lot, sometimes making one turn takes like 20 seconds before it manages to bounce like that to the straight line.
Any tips or tricks I could use to improve my Line Follower to deal better with those turns and overall?
Here is my code on GitHub written with Python API for ev3dev.
python
asked Nov 16 '18 at 19:36
StormwakerStormwaker
356
I'm building a line follower with EV3 lego kit as a school project. To stay on the line I'm using PID regulator which uses difference between 2 color sensors on the front for calculating error (sensor read ranges from about 20 on black to 200 on white). It looks something like this:
The code I wrote works pretty well for smooth turns, even the sharp ones - but if the turn is a straight 90 degree angle something like this happens:
- Robot starts the turn
- It's not turning fast enough and both sensors end up on the black line
- Error falls to zero as both sensors are reading same value from black
- As the error is zero the robot goes straight and looses the line
I can manage make those turns by slowing speed and increasing integral and differential constants, but that makes control too aggressive and then it bounces left-right a lot, sometimes making one turn takes like 20 seconds before it manages to bounce like that to the straight line.
Any tips or tricks I could use to improve my Line Follower to deal better with those turns and overall?
Here is my code on GitHub written with Python API for ev3dev.
python
python
asked Nov 16 '18 at 19:36
StormwakerStormwaker
356
asked Nov 16 '18 at 19:36
StormwakerStormwaker
356
asked Nov 16 '18 at 19:36
StormwakerStormwaker
356
asked Nov 16 '18 at 19:36
StormwakerStormwaker
356
asked Nov 16 '18 at 19:36
StormwakerStormwaker
356
356
Do you have access to the absolute values in addition to their relative values?
– Acccumulation
Nov 16 '18 at 19:42
@Acccumulation If you mean absolute values from each sensor then yes - r1 variable holds read from left and r2 from right.
– Stormwaker
Nov 16 '18 at 19:43
When it turns, does it continue forward motion, or does it just pivot? And is more sensors an option?
– Acccumulation
Nov 16 '18 at 19:53
@Acccumulation It turns slightly to the direction it was supposed to turn, because of the integral part, If I set integral high enough it can even return to the line sometimes, but other times it will just start making circles without reaching the line. I can only use 2 sensors.
– Stormwaker
Nov 16 '18 at 20:02
It might help to draw a diagram for the right angle case. When you say that you end up with both sensors on the line, I take it that if you start going north and then the line turns east, the right sensor is on the line going east and the left sensor is on the line going north?
– Acccumulation
Nov 16 '18 at 20:08
|
show 3 more comments
Do you have access to the absolute values in addition to their relative values?
– Acccumulation
Nov 16 '18 at 19:42
@Acccumulation If you mean absolute values from each sensor then yes - r1 variable holds read from left and r2 from right.
– Stormwaker
Nov 16 '18 at 19:43
When it turns, does it continue forward motion, or does it just pivot? And is more sensors an option?
– Acccumulation
Nov 16 '18 at 19:53
@Acccumulation It turns slightly to the direction it was supposed to turn, because of the integral part, If I set integral high enough it can even return to the line sometimes, but other times it will just start making circles without reaching the line. I can only use 2 sensors.
– Stormwaker
Nov 16 '18 at 20:02
It might help to draw a diagram for the right angle case. When you say that you end up with both sensors on the line, I take it that if you start going north and then the line turns east, the right sensor is on the line going east and the left sensor is on the line going north?
– Acccumulation
Nov 16 '18 at 20:08
Do you have access to the absolute values in addition to their relative values?
– Acccumulation
Nov 16 '18 at 19:42
Do you have access to the absolute values in addition to their relative values?
– Acccumulation
Nov 16 '18 at 19:42
@Acccumulation If you mean absolute values from each sensor then yes - r1 variable holds read from left and r2 from right.
– Stormwaker
Nov 16 '18 at 19:43
@Acccumulation If you mean absolute values from each sensor then yes - r1 variable holds read from left and r2 from right.
– Stormwaker
Nov 16 '18 at 19:43
When it turns, does it continue forward motion, or does it just pivot? And is more sensors an option?
– Acccumulation
Nov 16 '18 at 19:53
When it turns, does it continue forward motion, or does it just pivot? And is more sensors an option?
– Acccumulation
Nov 16 '18 at 19:53
@Acccumulation It turns slightly to the direction it was supposed to turn, because of the integral part, If I set integral high enough it can even return to the line sometimes, but other times it will just start making circles without reaching the line. I can only use 2 sensors.
– Stormwaker
Nov 16 '18 at 20:02
@Acccumulation It turns slightly to the direction it was supposed to turn, because of the integral part, If I set integral high enough it can even return to the line sometimes, but other times it will just start making circles without reaching the line. I can only use 2 sensors.
– Stormwaker
Nov 16 '18 at 20:02
It might help to draw a diagram for the right angle case. When you say that you end up with both sensors on the line, I take it that if you start going north and then the line turns east, the right sensor is on the line going east and the left sensor is on the line going north?
– Acccumulation
Nov 16 '18 at 20:08
It might help to draw a diagram for the right angle case. When you say that you end up with both sensors on the line, I take it that if you start going north and then the line turns east, the right sensor is on the line going east and the left sensor is on the line going north?
– Acccumulation
Nov 16 '18 at 20:08
|
show 3 more comments
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Do you have access to the absolute values in addition to their relative values?
– Acccumulation
Nov 16 '18 at 19:42
@Acccumulation If you mean absolute values from each sensor then yes - r1 variable holds read from left and r2 from right.
– Stormwaker
Nov 16 '18 at 19:43
When it turns, does it continue forward motion, or does it just pivot? And is more sensors an option?
– Acccumulation
Nov 16 '18 at 19:53
@Acccumulation It turns slightly to the direction it was supposed to turn, because of the integral part, If I set integral high enough it can even return to the line sometimes, but other times it will just start making circles without reaching the line. I can only use 2 sensors.
– Stormwaker
Nov 16 '18 at 20:02
It might help to draw a diagram for the right angle case. When you say that you end up with both sensors on the line, I take it that if you start going north and then the line turns east, the right sensor is on the line going east and the left sensor is on the line going north?
– Acccumulation
Nov 16 '18 at 20:08