Obstacle Avoidance Robot using Raspberry Pi 4 & HC-SR04

Overview
In this project, we will make an Obstacle Avoidance Robot using Raspberry Pi 4 & Ultrasonic Sensor HC-SR04. For this, we will use a Robotic Car Kit called Picar-X Robot from Sunfounder.
The
PiCar-X
is an
AI self-driving robot
car that uses
Raspberry Pi
as its control center. The Robotic Kit is designed by
SunFounder
. The Kit comes with a
Robot HAT
for Raspberry Pi. The HAT integrates the
motor driving, servo driving
, and preset ADC, PWM, and digital pins to extend the functionality. The PiCar-X’s has a
2-axis camera
module,
ultrasonic module
, and
line tracking modules
that can provide the functions of
color/face/traffic signs detection, automatic obstacle avoidance, automatic line tracking
, etc.
An
obstacle-avoiding robot
is a fully
autonomous robot
that can be able to avoid any obstacle it faces when it moves. Simply, when it met an obstacle while it moving forward, automatically stops moving forward and makes a step back. Obstacle-avoiding robots can be used in almost all mobile
robot navigation systems
. They can be used for household work like automatic vacuum cleaning. They can also be used in dangerous environments, where human penetration could be fatal.
Bill of Materials
We need the following components along with the
SunFounder Robot Car Kit
to make an Obstacle Avoidance Robot using Raspberry Pi. You can purchase all these components from Amazon links:
S.N.
Components
Quantity
Purchase Links

Raspberry Pi Ai Car Kit PiCar-X

Amazon
SunFounder

Raspberry Pi 4

Amazon
SunFounder

Samsung 18650 Battery

AliExpress

SD Card 16/32 GB

Amazon
SunFounder

SD Card Adapter

Amazon
AliExpress

18650 Battery Charger

Amazon
AliExpress
Robot HAT cannot charge the battery, so you need to buy a battery charger at the same time.
Robot Assembly
The
Sunfounder Picar-X Robot Kit
comes with all the necessary components required for the Robot which include the following components. You need to buy a Raspberry Pi 4 Board and a pair of
Samsung 18650 Batteries
separately.
The most important part of this Kit is Robot HAT. With the Robot HAT board, the PiCar-X integrates left/right driving motors, servo motors for steering, and the camera’s pan/tilt functions, and pre-sets the Robot HAT’s ADC, PWM, and Digital I2C pins to allow for extensions to the standard functionality of the Raspberry Pi.
Both a
speaker
and a
Bluetooth
chip have been engineered into the Robot HAT for remote control of Text-to-Speech, sound effects, or even background music functionality.
To assemble the components together and make a perfect Robotic Car you can follow the
Assembly Guide
. The PDF Document has all the images and a pictorial view for easy help with assembly.
The
Ultrasonic Sensor HC-SR04
is connected to the following pins of Robot HAT.
Ultrasonic Sensor
RPI HAT
VCC
3.3V
GND
GND
TRIG
D2
ECHO
D3
The
Robotic Kit
Part details,
Assembly
guide, HAT parts & functionality,
calibration
process, Robot
Testing
and Setting Up Rasbian OS has been explained in
PiCar-X Getting Started
guide.
Read the tutorial thoroughly to understand the
Hardware & Software Setup
Part.
Installing Python Modules & Libraries
The
OS installation
part and setup part can be followed on
Raspberry Pi OS Setup
. But for this robotic project part, it is recommended to install
Raspberry Pi OS(Legacy)
You can either use the
HDMI Screen
or enable
SSH
and connect the Raspberry Pi to
VNC Viewer
using the local IP Address, username, and password. It is best to connect the Robot Wirelessly via a
Remote Desktop
as we need a remote control for it.
The
Picar-X Robot
should be turned ON and Raspberry Pi should be connected to the network. Now let’s install all the Python Modules and libraries.
Lets first update the system using following commands.

sudo
apt
update
sudo
apt
upgrade
Then install the Python3 related packages.

sudo
apt
install
git
python3
pip
python3
setuptools
python3
smbus
Download & install the libraries for
Robot-Hat

cd
/
/
pi
/
git
clone
https
:
//github.com/sunfounder/robot-hat.git
cd
robot
hat
sudo
python3
setup
py
install
Running ‘
setup.py
‘ will download some necessary components. Your download may have failed due to network issues. You may need to download it again at this point. See the following interface, type ‘
Y
‘, and press Enter.
Now, download and install the ;
vilib
‘ module.

cd
/
/
pi
/
git
clone
https
:
//github.com/sunfounder/vilib.git
cd
vilib
sudo
python3
install
py
Similarly download and install the ‘
picar-x
‘ module.

cd
/
/
pi
/
git
clone
b
v2

https
:
//github.com/sunfounder/picar-x.git
cd
picar
sudo
python3
setup
py
install
This will download a large number of files, therefore it will take time.
Once the download is complete, run the ‘
i2samp.sh
‘ script to install the components required by the i2s amplifier, otherwise the picar-x will have no sound.

cd
/
/
pi
/
picar
sudo
bash
i2samp
sh
Type ‘
y
‘ and press enter to continue running the script.
Type ‘
y
‘ and press enter to run ‘
/dev/zero
‘ in the background.
Type y and press enter to restart the Picar-X.
After restarting, the Raspberry Pi will connect to the Network and will play a sound.
If there is no sound after restarting, you may need to run the ‘
i2samp.sh
‘ script several times.
All the installation and setup part is complete here.
Python Code for Raspberry Pi Obstacle Avoidance Robot
Here is a complete Python Code for Obstacle Avoidance Robot using Raspberry Pi 4 & Ultrasonic Sensor HC-SR04.
You can directly run the code from the terminal using the following command.

cd
/
/
pi
/
picar
/
example
sudo
python3
avoiding_obstacles
py
The code is also located in the source code path ‘
picar-x/example
‘. You can directly open the code from this location. You can Modify/Reset/Copy/Run/Stop the code below.

from
picarx
import
Picarx
def
main
(
)
:
try
:
px
=
Picarx
(
)
# px = Picarx(ultrasonic_pins=['D2','D3']) # tring, echo
px
forward
(

)
while
True
:
distance
=
px
ultrasonic
read
(
)
(
"distance: "
distance
)
if
distance
>

and
distance
<

:
if
distance
<

:
px
set_dir_servo_angle
(

)
else
:
px
set_dir_servo_angle
(

)
finally
:
px
forward
(

)
if
__name__
==
"__main__"
:
main
(
)
Code Explanation
The ultrasonic module is also imported into the picarx module, and we can use some of its encapsulated functions to detect distance.

from
picarx
import
Picarx
Because the ultrasonic module is imported into the picarx module, we can directly use
px.ultrasonic.read()
to get the distance.

px
=
Picarx
(
)
px
forward
(

)
while
True
:
distance
=
px
ultrasonic
read
(
)
The following code snippet reads the distance value reported by the ultrasonic module, and if the distance is below 25cm (10 inches) it will set the steering servo from 0° (straight) to -35° (turn left).

while
True
:
distance
=
px
ultrasonic
read
(
)
(
"distance: "
distance
)
if
distance
>

and
distance
<

:
if
distance
<

:
px
set_dir_servo_angle
(

)
else
:
px
set_dir_servo_angle
(

)
Testing Obstacle Avoidance Robot using Raspberry Pi
In this project, PiCar-X will
detect obstacles
in front of it while moving forward, and when the obstacles are too close, it will change the
direction
of moving forward.
After running the code, PiCar-X will walk
forward
If it detects that the distance of the obstacle ahead is less than
25cm
, it will turn left. If there is no obstacle in the direction after turning left or the obstacle distance is greater than 25cm, it will continue to move forward.
This is how you can make an
Obstacle Avoidance Robot using Raspberry Pi 4
& Ultrasonic Sensor HC-SR04.
Video Tutorial & Guide
PiCar-X Self Driving AI Robot with Raspberry Pi || Obstacle, Line, Signal, Cliff Detection & TTS
Watch this video on You