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remote 3d slam with limited sensing and bandwidth

asked 2018-05-08 14:43:16 -0600

Toms42 gravatar image

I'm trying to implement a 3d visualization for a remotely operated robot, which will be equipped with either stereo grayscale cameras or one grayscale camera and a line striping system that can generate a point cloud. However, the application is incredibly bandwidth/compute limited, and most SLAM systems I've found don't seem to fit the requirements well. The robot is incredibly slow, and I would likely be able to get a pair of images maybe every 5-10cm it travels, in an outdoor environment.

I've looked at rtabmap, specifically this example, but I can't run stereo odometry on the robot, and at this bandwidth I'm unsure if it would work remotely. I have no access to compass or gps data, only IMU data from accel+gyro.

Does anyone here have experience with remote slam for a low-bandwidth compute-limited platform?

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answered 2018-05-10 11:16:26 -0600

matlabbe gravatar image

How much bandwidth do you have? Based on this tutorial and that answer, you may get 600 KB/sec for 5 Hz images or 4.5MB/sec for 30 Hz images. For stereo odometry, it is preferred that you have at least 10-15 Hz, which would be between 1 and 2 MB/sec. Another option is to do visual odometry onboard (if the onboard computer can compute odometry over 10 Hz), but SLAM remotely. As rtabmap is updating only at 1 Hz (by default), you would only need to publish images at 1 Hz out of the robot with the odometry computed.

cheers,
Mathieu

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We only have about 10Kbps of bandwidth, so image frequency is measured in minutes not hertz. The upside is that the robot is traversing on the order of mm/s, so we will likely only be moving several cm between photos, but very slowly. Odometry on the robot would be ideal, but hopefully unnecessary.

Toms42 gravatar imageToms42 ( 2018-05-10 17:05:16 -0600 )edit

Just another idea, having lower resolution images may also help to save some bandwidth at the cost of less good odometry.

matlabbe gravatar imagematlabbe ( 2018-05-10 17:16:53 -0600 )edit

oh yeah that's the plan for sure. Even at 240p black/white images, it's something like 1-2 minutes per frame at 10kbps. I might be sending point clouds too. I'm mostly worried about even being able to configure RTABMAP to update when I get a frame, rather than at a fixed rate.

Toms42 gravatar imageToms42 ( 2018-05-10 17:20:15 -0600 )edit

We might abandon actual SLAM and rely on standard point cloud registration without loop closure. The mission goal is to map a relatively featureless outdoor environment with several known landmarks, but the bandwidth limitations are very restrictive. We're limited to small embedded devices too.

Toms42 gravatar imageToms42 ( 2018-05-10 17:21:56 -0600 )edit

If you could segment out the 'known landmarks' and identify them (ie: without using a slam approach, sort of like a virtual tag or beacon), perhaps the fiducials pkg could be interesting.

gvdhoorn gravatar imagegvdhoorn ( 2018-05-11 03:24:46 -0600 )edit

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Asked: 2018-05-08 14:43:16 -0600

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Last updated: May 10 '18