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 |
|---|---|---|---|
| 1 | Raspberry Pi Ai Car Kit PiCar-X | 1 | Amazon | SunFounder |
| 2 | Raspberry Pi 4 | 1 | Amazon | SunFounder |
| 3 | Samsung 18650 Battery | 2 | AliExpress |
| 4 | SD Card 16/32 GB | 1 | Amazon | SunFounder |
| 5 | SD Card Adapter | 1 | Amazon | AliExpress |
| 6 | 18650 Battery Charger | 1 | 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.
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sudo apt update sudo apt upgrade |
Then install the Python3 related packages.
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sudo apt install git python3-pip python3-setuptools python3-smbus |
Download & install the libraries for Robot-Hat.
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cd /home/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.
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cd /home/pi/ git clone https://github.com/sunfounder/vilib.git cd vilib sudo python3 install.py |
Similarly download and install the ‘picar-x‘ module.
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cd /home/pi/ git clone -b v2.0 https://github.com/sunfounder/picar-x.git cd picar-x 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.
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cd /home/pi/picar-x 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.
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cd /home/pi/picar-x/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.
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from picarx import Picarx def main(): try: px = Picarx() # px = Picarx(ultrasonic_pins=['D2','D3']) # tring, echo px.forward(30) while True: distance = px.ultrasonic.read() print("distance: ",distance) if distance > 0 and distance < 300: if distance < 25: px.set_dir_servo_angle(-35) else: px.set_dir_servo_angle(0) finally: px.forward(0) 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.
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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.
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px = Picarx() px.forward(30) 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).
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while True: distance = px.ultrasonic.read() print("distance: ",distance) if distance > 0 and distance < 300: if distance < 25: px.set_dir_servo_angle(-35) else: px.set_dir_servo_angle(0) |
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
