1.10: Obstacle Avoidance

Have you ever been in a car when the emergency auto brakes went on? What happened? How was the car able to tell when to stop? Self-driving cars need to be able to avoid obstacles in an emergency. Instead of infrared, they use more advanced sensors like LIDAR (Light Imaging Detection and Ranging) and RADAR. LIDAR uses laser light to map out the environment while RADAR uses radio waves. Despite not having this technology, Zumi can still avoid obstacles!
zumi_beginner zumi_beginner

This lesson works with:

Zumi
Python
  • beginner
  • infrared
  • IR
  • obstacle avoidance
  • programming
  • Python
  • sensor
  • Zumi

Grade level:

6 - 12+

Approx. time required:

60 - 75 mins
Step 1

Obstacle Avoidance (Front IR)

Have you ever been in a car when the emergency auto brakes went on? What happened? How was the car able to tell when to stop? Self-driving cars need to be able to avoid obstacles in an emergency. Instead of infrared, they use more advanced sensors like LIDAR (Light Imaging Detection and Ranging) and RADAR. LIDAR uses laser light to map out the environment while RADAR uses radio waves. Despite not having this technology, Zumi can still avoid obstacles!

Import libraries

In [ ]:
from zumi.zumi import Zumi
import time

zumi = Zumi()
Step 2

Stop for pedestrians

As you saw in the video, it is extremely important for self-driving cars to be able to detect dangers up ahead, especially if they are pedestrians! In this activity, you will code Zumi to drive forward using go_straight() until she detects your hand with either the front left or front right IR sensor. now When you take your hand away, Zumi should keep driving.

Pseudocode

This time, you will be writing the pseudocode for this mission! In the cell below, write each line of pseudocode as a comment. You can do this by putting the pound sign (#) at the beginning of the line. The computer will ignore them but they are a great way to organize your code and provide documentation.

Once you have your pseudocode, translate each line of code into Python and fill it in the for loop below:

In [ ]:
for x in range(300):
    # Write your code here

zumi.stop() # Don't forget to stop at the end!
print("Done!")
Step 3

Zumi Maze

Collision avoidance is an essential feature in any car, but a self-driving car would have to go around the obstacles. In this section, you will learn about how to change direction if Zumi encounters an obstacle.

For this activity, you will need both of your front IR sensors. This time, instead of stopping and waiting for the obstacle to be removed, you will tell Zumi to turn a little to the left or to the right to go around, depending on which sensor is triggered.

Initialize heading

In the beginning of the program, set your heading to 0. You can create a variable with a different name, like angle or direction, but we will use heading in this example. The reason you will be using a variable is because your direction will constantly be changing depending on what obstacles get in Zumi’s way!

heading=0

For all of our programs, it is very important to set the heading to zero to make sure you start off going straight!

Change heading

For this mission, your goal is to turn a little to the left if your right sensor is triggered, and a little to the right if your left sensor is triggered. If both sensors are triggered, something is directly in front! Zumi will need to do a complete 180 to avoid what could possibly be a dead end. Instead of calling turn_left() or turn_right(), you will instruct Zumi to change heading by adding or subtracting degrees. For example:

if front_right_ir < 100:
heading = heading + 30

Since the right sensor being triggered means we go left, you need to add degrees, not subtract. Look back to the lesson gyroscopes if you need help remembering absolute angles.

Pseudocode

set heading to zero
check IR sensors
if front right sensor is triggered, change heading by positive degrees to go left
else if front left sensor is triggered, change heading by negative degrees to go right
else if both sensors are triggered, stop, reverse a little bit, and change heading by 180 (positive or negative)
keep going straight with the new heading
repeat!

Logical operators

Before you go into writing your code, notice that the third if statement is checking if both are triggered. In Python, you would use the and operator, just like in English!

 

if front_right_ir < 100 and front_left_ir < 100:
# Write code here to stop, reverse, and change directions by 180

In [ ]:

# Write out your code here!

heading = 0
zumi.reset_gyro()

for x in range(1000):
    # Statements

zumi.stop()

 

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