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Michael Wiznitzer

Northwestern University MSR Hackathon (Fall 2017)

To track a red ball with a camera mounted on 2 servos that are commanded to move such that the ball stays in the center of the camera frame.

The ROS camera driver used to get a live video feed is supported by theusb_cam package. Once a feed is obtained, each image is converted to the HSV color space for better color segmentation using OpenCV. The upper and lower HS bounds for the red color were determined experimentally and can be adjusted using trackbars if need be to take into account different lighting conditions. The centroid of the largest contour in each filtered image is determined and is passed along to the servo node.

With the centroid information passed to this node, the servos can be controlled such that the centroid is always in the center of the camera frame. The servos are mounted on apan-tilt mechanism and are controlled through thePololu Micro Maestro servo controller. For smooth motion, each servo position is updated with a small increment or decrement followed by a very small time delay.

camera_trak.launch

camera_pak_node.py

Subscribed Topic:/usb_cam/image_raw

Published Topic:/center_point

servotrack_node.py

Subscribed Topic:/center_point

A video of the ball tracking in action can be seen below.