of 500 milliseconds. You have five seconds to place your target object in front of
the camera lens. The next display states that the target is captured.
The following LCD screens provide the object target information.
We begin with Confidence. If the camera does not see a predetermined
amount of target colored pixels, it assumes the target is lost. If it’s above the
amount, the target is acquired (Figure 17).
When the target is acquired, the program will continue to map the target
within its FOV.
The next value after Confidence is the horizontal X. The value of X
determines whether the target is to the left, right, or center (Figure 18).
The next value after the horizontal X is the vertical Y. The value of Y
determines whether the target is up, down, or center (Figure 19).
The next value after the vertical Y is the number of pixels (size). The number
of pixels is used to determine distance from the camera (Z). If the pixels are
under a certain value, it is assumed the target has moved away. If the pixels are
above a certain value, it is assumed the target is too close. In between these two
values, the object is in range (Figure 20).
What Makes a Good Target
Choosing a proper object is essential to having the C-Bot accurately follow
your target. Here are a few guidelines:
Primary Color
I have gotten good results with
monochromatic targets such as a red
ball or orange basketball.
Contrast
To successfully track a target, it
should contrast with the background,
for instance, a red ball against a white
background. The better the contrast,
the easier it is to track the target.
Run Mode
In Run mode, the interpretation of the M packet is identical. However,
instead of updating the LCD display, the interpretation activates the servomotors
to follow the target. The LCD will output instructions up to and including
placing the target object in front of the CMU lens. After that, the LCD is no
longer updated.
After you have tested and found a good target object, you can change
from Test mode to Run mode. In Run mode, turn off the LCD display to conserve
power. The first sequence of blinking the LED confirms communication. The
second sequence is to place the target in front of the lens.
False Targets
In the process of tracking a target,
the camera can lock onto a similarly
colored object and misinterpret that
colored object for the target. For
example, if the red ball rolled in front
of red construction paper, the camera
could lock onto the paper and disregard
the ball. So, be aware that components
in the background shouldn’t match your
target’s color.
STEER WINNING ROBOTS
WITHOUT SERVOS!
Perform proportional speed, direction, and steering with
only two Radio/Control channels for vehicles using two
separate brush-type electric motors mounted right and left
with our mixing RDFR dual speed control. Used in many
successful competitive robots. Single joystick operation: up
goes straight ahead, down is reverse. Pure right or left twirls
vehicle as motors turn opposite directions. In between stick
positions completely proportional. Plugs in like a servo to
your Futaba, JR, Hitec, or similar radio. Compatible with gyro
steering stabilization. Various volt and amp sizes available.
The RDFR47E 55V 75A per motor unit pictured above.
www.vantec.com
Order at
(888) 929-5055
SERVO 05.2009
53
