SunFounder PiCar-X Kit - Page 83

SunFounder PiCar-X Kit
(continued from previous page)
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 move-
ment, 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).
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