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[DPRG] LiDAR-Lite 360 degree continuously rotating mount

Subject: [DPRG] LiDAR-Lite 360 degree continuously rotating mount
From: Paradug paradug at gmail.com
Date: Mon Feb 2 22:29:21 CST 2015

David,
    I agree that when the sensor gets mounted and used there will be lots of changes. For this reason, it is important to get a test platform running around. In the case of the Neato LiDAR we already have an example of it working, i.e., the original product. I am trying to get a test platform together for the Neato LiDAR. Here is my initial take on two of your questions.

Q:  Are 360 degree sweeps really necessary? 
A:  No. However, in an indoor environment with lots of walls a 360 degree sweep is very useful, particularly with a featureless localization scheme (see http://youtu.be/rM-CajaLZi4?list=PLpUPoM7Rgzi_7YWn14Va2FODh7LzADBSm and later videos in the series). Outdoors, I think it depends on what you plan to use the LiDAR information for: obstacle detection, localization, or to adjust navigation. How I would plan to use the LiDAR-lite would not require 360 degree sweeps, since I would be using it to detect obstacles and guide navigation. For this purpose, info in front of you has more value. However, I also want to play with the Neato LiDAR for my own edification.

Q:  Do you really need 40 yard range?
A:  That depends on how fast you plan to go and the speed of the sensor. For the Sparkfun AVC event in June, I am exploring going pretty fast. Unfortunately, I think the outdoors 5 yard max range of the Neato XV11 LiDAR might be too short to be useful. There may be non-LiDAR based alternative solutions.

Here is some food for thought, it is a video from the Sparkfun AVC 2013 event (http://youtu.be/BGbrmp9R6Vg). The vehicle was doing about 20 mph and performed both the hoop and ramp bonus objectives. The course is going to be different location this year. They say they are looking for ways to reward entries that do not use GPS, but they haven’t announced the rules. 


Regards,
Doug P.




From: David Anderson 
Sent: Monday, February 02, 2015 7:36 PM
To: dprglist at dprg.org 
Subject: Re: [DPRG] LiDAR-Lite 360 degree continuously rotating mount

Doug,

My own experience is that until a sensor is mounted on a robot and tasked with doing something, you really don't know if it works or not, other than in a purely technical sense.  Once it goes into use, lots of changes in design and application are then usually required to make it functional and practical.   Only then, again in my experience, does something useful begin to emerge.

Look at our own DPRG projects web page, for example. A number of years ago Earl came up with a nice little board to build his own custom IMU for a balancing robot.  Looks really good on paper.  Nice DPRG project with an excellent web page.  

Only problem is, he never was actually able to get a robot to balance using it.   Though there is no mention of that in the article.  Like so many similar robot technology web pages.  Software problems?  Sensor problems?  Who will ever know?  

In my own case, a number of years ago I spent considerable amount of time and energy designing a bumper to detect collisions for my two-wheel balancing robot.  It's not a simple problem, because of the way the robot moves, but I came up with what seemed to me to be a usable and practical solution.  

However... as progress proceeded on the balancer, it slowly became apparent that a two-wheel balancing robot doesn't need a bumper.  Because of the physics involved in dynamic balance locomotion, the robot can sense collisions from the geometry of the platform itself.  No bumper needed.   That's a fairly major "change in design and application" of the sensor that I could not have anticipated when working on the bumper.   

Hence my skepticism.   

So, what are you planning to do with sensor detections out to 40 meters?   Is that really useful?   Similarly, is 360 degrees really required?  For example, we humans have eyes in the front but not the back --- seems to work fine.    Until the device is actually evaluated in situ, those are all likely to remain unknowns.

regards,
dpa




On 02/02/2015 10:45 AM, Paradug wrote:

  David,
        I understand your pain. I often have similar thoughts. 

       The LiDAR-lite shows promise as a sensor due to its range outdoors (~40 meters). It only takes a max of 100 points per second which is slow compared to the rotating LiDARs made for indoor use, like the Neato XV11 (range ~6 meters indoors), which make about ~2000 reads per second. In the example shown in the links, the author is showing a successful 360 degree sweep at about once every 8 seconds by using 2 sensors. This is a meaningful step forward for using these sensors usefully in a robot, but still slow. Using the same idea with faster rotation and 360 points per revolution, he should be able to get down to about 2 seconds per revolution.  For a robot going less than 2 or 3 meters per second that might be okay. Especially for the case where no object was moving (i.e., people). 

      I am considering an LiDAR-lite based idea that is different for use on my outdoor robot. The linked project has some ideas worth stealing ;^). However, I am still on the fence on purchasing the LiDAR-lite. I need to have a firmer grasp of what I have to accomplish in the software. The SLAM course I mentioned earlier is helping that situation.

      This might be a good opportunity for a group project within the club. I know some members have LiDAR-lites. 

  Regards,
  Doug P. 

  From: David Anderson 
  Sent: Monday, February 02, 2015 9:44 AM
  To: dprglist at dprg.org 
  Subject: Re: [DPRG] LiDAR-Lite 360 degree continuously rotating mount

  Cool.

  <rant>

  In all my other hobbies, except robotics, when someone has a new innovation, they show their craft (heli, sailboat, whatever) doing something really cool, and then explain the technology that makes it possible.   That's why I might be interested in the technology, because it allows the platform to do something interesting that can't be done any other way.

  But that is never the case with hobby robotics.  Instead, the technology is demonstrated as if it is an end in itself, with the hope that someone will eventually do something cool with it.  Just once, I'd like to go to a link like that posted below by Doug, and see a video of a robot DOING SOMETHING interesting, followed by a description of the technology required to do that interesting thing.   

  (As an aside, this same thing seems to apply in spades to all the hobbiest ROS robots I've come across.  Surely there are some HOBBY robots running ROS somewhere out there DOING SOMETHING  interesting that makes all the pain of getting ROS to work worthwhile.   If so they seem to be keeping pretty quiet about  it.   Where are all the videos?)
    
  </rant>

  OK, I'm done, move along, nothing to see here...

  dpa





  On 02/02/2015 08:15 AM, Paradug wrote:

    Here is an interesting project for members with 2 LiDAR-lites. 

    http://www.thingiverse.com/thing:662646

    http://hackaday.io/project/4087-360-degree-lidar-lite-scanner


    Regards,
    Doug P.



     

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