利用 CmuCam2 攝影機追蹤色球 

作者：劉孝忠 (2008-09-29)

本文介紹Carnegie Mellon University Robotics Institute 生產之CMUcam2，並用CMUcam2來追蹤色球。

圖1 硬體架構圖

一、CMUcam2簡介

圖2 CMUcam2

• Track user-defined colors at up to 50 Frames Per Second (FPS) 
• Track motion using frame differencing at 26 FPS 
• Find the centroid of any tracked data 
• Gather mean color and variance information
• Gather a 28 bin histogram of each color channel
• Manipulate horizontally pixel-differenced images
• Transfer a real-time binary bitmap of the tracked pixels in an imageArbitrary image windowing
• Adjust the camera's image properties
• Dump a raw image (single or multiple channels)
• Up to 160 X 255 resolutionSupports multiple baudrates -- 115,200 57,600 38,400 19,200 9,600 4,800 2,400 1,200
• Control 5 servo outputs
• Automatically use servos to do two axis color trace

二、CMUcam2資料封包(Data Packet)

Type T data packet format:

This is the return packet from a color tracking or frame differencing command.

mx - The middle of mass x value

my - The middle of mass y value

x1 - The left most corner’s x value

y1 - The left most corner’s y value

x2 - The right most corner’s x value

y2 -The right most corner’s y value

pixels –Number of Pixels in the tracked region, scaled and capped at 255: (pixels+4)/8

confidence -The (# of pixels / area)*256 of the bounded rectangle and capped at 255

T mx my x1 y1 x2 y2 pixels confidence\r

Type S data packet format:

This is a statistic packet that gives information about the camera’s view

Rmean - the mean Red or Cr (approximates r-g) value in the current window

Gmean - the mean Green or Y (approximates intensity) value found in the current window

Bmean - the mean Blue or Cb (approximates b-g) found in the current window

Rdeviation - the *deviation of red or Cr found in the current window

Gdeviation- the *deviation of green or Y found in the current window

Bdeviation- the *deviation of blue or Cb found in the current window

*deviation: The mean of the absolute difference between the pixels and the region mean. 

S Rmean Gmean Bmean Rdeviation Gdeviation Bdeviation \r 

三、CMUcam2命令(Command)

The camera is controlled using serial communication. All commands are sent using visible ASCII characters.

四、CMUcam2硬體接線及Baudrate設定

圖3硬體接線

圖4 Baudrate設定