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10. Bull Fight

Make PiCar-X an angry bull! Use its camera to track and rush the red cloth!

Run the Code

cd ~/picar-x/example
sudo python3

View the Image

After the code runs, the terminal will display the following prompt:

No desktop !
* Serving Flask app "vilib.vilib" (lazy loading)
* Environment: production
WARNING: Do not use the development server in a production environment.
Use a production WSGI server instead.
* Debug mode: off
* Running on (Press CTRL+C to quit)

Then you can enter http://<your IP>:9000/mjpg in the browser to view the video screen. such as:




You can Modify/Reset/Copy/Run/Stop the code below. But before that, you need to go to source code path like picar-x\examples. After modifying the code, you can run it directly to see the effect.

from picarx import Picarx
from time import sleep
from vilib import Vilib

px = Picarx()

def clamp_number(num,a,b):
return max(min(num, max(a, b)), min(a, b))

def main():
    speed = 50
    x_angle =0
    y_angle =0
    while True:
        if Vilib.detect_obj_parameter['color_n']!=0:
            coordinate_x = Vilib.detect_obj_parameter['color_x']
            coordinate_y = Vilib.detect_obj_parameter['color_y']

            # change the pan-tilt angle for track the object
            x_angle +=(coordinate_x*10/640)-5
            x_angle = clamp_number(x_angle,-35,35)

            y_angle -=(coordinate_y*10/480)-5
            y_angle = clamp_number(y_angle,-35,35)

            # move
            # The movement direction will change slower than the pan/tilt direction
            # change to avoid confusion when the picture changes at high speed.
            if dir_angle > x_angle:
                dir_angle -= 1
            elif dir_angle < x_angle:
                dir_angle += 1

        else :

if __name__ == "__main__":

        print("stop and exit")

How it works?

You need to pay attention to the following three parts of this example:

  1. Define the main function:

    • Start the camera using Vilib.camera_start().

    • Display the camera feed using Vilib.display().

    • Enable color detection and specify the target color as “red” using Vilib.color_detect("red").

    • Initialize variables: speed for car movement speed, dir_angle for the direction angle of the car’s movement, x_angle for the camera’s pan angle, and y_angle for the camera’s tilt angle.

  2. Enter a continuous loop (while True) to track the red-colored object:

    • Check if there is a detected red-colored object (Vilib.detect_obj_parameter['color_n'] != 0).

    • If a red-colored object is detected, obtain its coordinates (coordinate_x and coordinate_y).

    • Calculate new pan and tilt angles (x_angle and y_angle) based on the detected object’s position and adjust them to track the object.

    • Limit the pan and tilt angles within the specified range using the clamp_number function.

    • Set the camera’s pan and tilt angles using px.set_cam_pan_angle() and px.set_cam_tilt_angle() to keep the object in view.

  3. Control the car’s movement based on the difference between dir_angle and x_angle:

    • If dir_angle is greater than x_angle, decrement dir_angle by 1 to gradually change the direction angle.

    • If dir_angle is less than x_angle, increment dir_angle by 1.

    • Set the direction servo angle using px.set_dir_servo_angle() to steer the car’s wheels accordingly.

    • Move the car forward at the specified speed using px.forward(speed).