Line follower proportional py v2

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Introduction

Robot

The idea and principle works for almost any robot thought this is tested using Asimov.

Sensors

The color sensor in reflected light intensity mode is used. The sensor convention is

1. port 1 = touch,
2. port 2 = gyro,
3. port 3 = color,
4. port 4 = infrared or ultrasonic

Theory

The proportional line follower actually follows the other side of the line. The turning radius is calculated using the minimum, maximum and current color sensor readings. Also, a proportional coefficient (P) is introduced. It should be noted that the values of the steering function needs be between -100 and +100. Thus, we employ Python Max and Min function.

An Example Code

#!/usr/bin/env python3
# https://sites.google.com/site/ev3devpython/

#Sensor port convention:
#port 3 = color
#port 1 = touch, port 2 = gyro, port 3 = color, port 4 = infrared or ultrasonic.
#84 is Max
#30 is Min

from ev3dev2.sensor.lego import ColorSensor
from ev3dev2.motor import MoveSteering, OUTPUT_B, OUTPUT_C
from time import sleep
import os

os.system('setfont Lat15-TerminusBold32x16') 

steer_pair = MoveSteering(OUTPUT_B, OUTPUT_C)
steer_pair.on(steering=0, speed=10)

cl = ColorSensor() 
clMax = 84
clMin = 30
clAve = (clMax + clMin)/2
P = 2.0

clN = clAve
steering = 0

while True:
    clN = cl.reflected_light_intensity
    #print( clN )
    #print( clAve )
    steering = P*( clN - clAve )
    steering = min(steering, 100)
    steering = max(steering, -100)
    print( steering )
    steer_pair.on(steering=steering, speed=20)

steer_pair.off()
sleep(5)

Exercises

1. It is difficult to debug the robot as it is silent. Let it say if it is in dark or light area. Use Sound.speak('White').wait() command or e.g. sound.beep() command. Sound is imported using import Sound command.

2. Make the robot move faster. Note that you need to change the parameters according to your line to follow (and robot). Generally, it is advised to change only one value at time. Time your original time and try to make it half.

3. Let the robot use the other side of the line.

4. Now the while loop is forever. Make the robot stop when the right has turned 3.4 revolutions. See ev3 Python for help.

5. Let the robot end when it encounters a silver tape (highly shiny).

6. The Rescue is robot game such that it needs to follow the dashed line. So, make a line with a segment missing, but make your robot to still overlap the missing segment and follow the line on the other side of the missing segment.

About

This course is supported by Meet and Code. The course is made in collaboration with Robotiikka- ja tiedekasvatus ry.

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Meet and Code II: Python