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 10.bull_fight.py

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 http://0.0.0.0:9000/ (Press CTRL+C to quit)

Then you can enter http://<your IP>:9000/mjpg in the browser to view the video screen. such as: https://192.168.18.113:9000/mjpg

Code

Note

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():
    Vilib.camera_start()
    Vilib.display()
    Vilib.color_detect("red")
    speed = 50
    dir_angle=0
    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)
            px.set_cam_pan_angle(x_angle)

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

            # 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
            px.set_dir_servo_angle(x_angle)
            px.forward(speed)
            sleep(0.05)

        else :
            px.forward(0)
            sleep(0.05)


if __name__ == "__main__":
    try:
    main()

    finally:
        px.stop()
        print("stop and exit")
        sleep(0.1)

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).