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How to create a 180 degree laserscan from a panning Kinect?

asked 2011-04-19 18:09:01 -0500

Bart gravatar image

updated 2016-10-24 08:59:15 -0500

ngrennan gravatar image

The Kinect has a narrow (57 degree) field of view, which is limited for obstacle avoidance, navigation and map making as pointed out elsewhere by others. My Kinect is mounted on a pan/tilt mechanism so I should be able to pan the laser and create a wider simulated laserscan. (but with an admittedly lower scan rate than a real laser) An advantage however is that the Kinect should be able to identify obstacles the full height of the robot, rather than just at the laser elevation. Does anyone have experience or example code available for this task?

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answered 2011-04-19 18:12:38 -0500

Bart gravatar image

Based on some help in previous ROS questions/answers I have developed a nodelet "pipeline" that augments the pointcloud_to_laserscan package provided in turtlebot. This pipeline takes the pointcloud from "cloud_throttle.cpp" and tranforms it geometrically based on pan and tilt angles broadcast to tf using pcl_ros::transformPointCloud in a new nodelet "cloud_to_scan_tf.cpp". It then uses a third nodelet "scan_to_wide.cpp" to overlay a sequence of panned narrow scans into a wider 180 degree scan. The result is a simulation of a wider field of view, horizontal mounted, forward facing, planer laser.

The "cloud_to_scan_tf.cpp" nodelet was documented previously as "cloud_to_scanHoriz.cpp" in the "pointcloud to laserscan with transform?" ROS Answers question.

Attached below is the code for the "scan_to_wide" nodelet and a typical launch file. There is a Bool message to start/stop the panning. This nodelet sends a Float32 message to a hardware interface program to move the pan servo and receives a JointState message from the hardware interface program to indicate the pan servo position. The Kinect is tilted downwards 25 degrees to improve visibility just in front of the robot, but tf corrects the laserscan to horizontal. When the robot is moving the Kinect is stationary facing forward. When the robot stops it does a 180 degree pan, which takes about 3 seconds. The Kinect nodelets and other hardware interface programs run on a small netbook (Atom N270 1.6 GHz) at 100% CPU, but only using 20 KB/sec of wireless network bandwidth to display the laserscan on rviz on a remote desktop computer.

I'm interested if anyone has suggestions for improvement or experience integrating a panning Kinect with the navigation stack. As the FAQ suggests, a longer discussion should be moved to the mailing list.

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I can report that a panning Kinect to laserscan can work well with gmapping. I only update the map when a new scan comes in and only send a wide scan when stationary, after a scan is completed. The scan matching localization in gmapping is impressive. Compensates for poor odometry.
Bart gravatar imageBart ( 2011-04-23 07:08:37 -0500 )edit

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Asked: 2011-04-19 18:09:01 -0500

Seen: 1,168 times

Last updated: Apr 19 '11