Neato XV-11 LIDAR hector_slam mapping without odometry at walking speeds?

asked 2016-01-02 11:37:47 -0500

dchang0
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I was inspired by this video to get an XV-11 LIDAR for indoor mapping via hector_slam:

https://www.youtube.com/watch?v=jSlkj...

(Note that the walking speed is quite low--the video had to be sped up 2.5X.)

I'm finding in practice that the results shown at the end of the video may be "at best"--my maps are messy and jump around/overlap on themselves. This is probably due to a problem with the particular XV-11 unit I received (that will be returned/exchanged because it sometimes emits 0.0mm readings for entire revolutions), but while researching the map's jumpiness/overlapping, I'm finding that people either gave up on the XV-11 and went to a higher-end LIDAR with a higher scan rate or added odometry, both of which increase the project cost dramatically.

So, I am wondering, before I return/exchange this XV-11, has anyone gotten the XV-11 to do decent 2D mapping without odometry at walking speeds (1.5m/s)? Is it just not possible with a 5Hz (300rpm) LIDAR? I'm not asking for perfect maps, just usable ones (no walls where there aren't really walls, etc.)

I am basically tasked to do this:

https://www.youtube.com/watch?v=F8pdO...

(Note that the user is walking quite rapidly--probably faster than 1.5m/s. We'd love to be able to go this quickly.)

If you did get it working, how did you do it? Thanks in advance!

answered 2016-01-03 04:31:40 -0500

Stefan Kohlbrecher

24361 ●173 ●299 ●444 https://www.energy-rob...

I don't have access to a XV-11, but I'd be interested in looking at a bag file if you have one. I know of a few people who successfully used hector_slam with the XV-11, but I guess nobody used a very high walking speed of higher than 1.5 m/s with it so far.

At 1.5 m/s with 5 Hz, the robot travels 30cm between scans. A further complication is that scan acquisition is not discrete but continuous, so the scans are warped by the platform motion (see high fidelity projection). At the slow scan rate and high movement speed this effect likely is much more pronounced than with other LIDARs and creates another chicken-and-egg problem (need to know platform motion to undistort scan, need undistorted scan for scanmatching and estimating platform motion).

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Thanks for the reponse, Stefan! I do not have a bag file yet, since we suspect our XV-11 is faulty. We will probably not be getting a bag file at all, since we will likely upgrade to a Hokuyo UTM-30LX laser scanner based in a large part on your answers and past writings about your project.

dchang0 ( 2016-01-03 04:58:43 -0500 )edit

May I ask one more question? Was the IMU required for the handheld UTM-30LX to do a scan without the map breaking, or could we reliably get unbroken maps without one? I am assuming that you were merely practicing for the IMU to be included in the ground robot.

dchang0 ( 2016-01-03 05:02:01 -0500 )edit

Depends on how much roll and pitch motion the sensor has and how the environment looks like. If you keep the sensor level and , a IMU is not required.

Stefan Kohlbrecher ( 2016-01-04 03:05:59 -0500 )edit

Thanks, Stefan! In our application, the floors will be very level and the only roll and pitch will be from the human tester's gait and hand motion. Later, when on a ground robot, the roll and pitch may be less than with the human tester. It sounds like an IMU is not necessary in either case.

dchang0 ( 2016-01-04 03:25:01 -0500 )edit

BTW, Stefan--there are several people asking about how to integrate IMU data into hector_slam on the YouTube videos in the Team Hector channel. Perhaps if you have time, you could answer them... I too am curious about the code required. Thanks!

dchang0 ( 2016-01-04 03:36:43 -0500 )edit

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