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[DPRG] LiDAR-Lite 360 degree continuously rotating mount

Subject: [DPRG] LiDAR-Lite 360 degree continuously rotating mount
From: cthurston cthurston at sc.rr.com
Date: Tue Feb 17 07:06:39 CST 2015

Hello David,

I think we all wish for that.

Monday, February 16, 2015, 9:24:07 PM, you wrote:

> Well, if we're going to throw       high-technology at the problem,
> how about just some genetically       modified grass that only grows
> to a certain height?  No mowing       needed...

> cheers!
> dpa

> On 02/15/2015 09:35 PM, Rud Merriam wrote:

>   
> Does a mower really need         localization? How about just going
> where the grass is not cut?         That is a vision processing
> problem. Or maybe you could use a         lidar to scan just above
> the height of cut grass. If it detects         grass it needs to be cut.


>   
>              - 73 - 
>    Rud Merriam K5RUD
>   Mystic Lake                 Software
>   
>   
>            On 02/15/2015 08:06 PM, Paul Bouchier wrote:
>   Hi David,

> All good points, but the intended application is localization,     
> not obstacle avoidance (though it may provide a partial solution    
> to that. An outdoor mowing robot is most in need of accurate        
> localization. Decent obstacle avoidance, particularly of things     
> the robot might run over and chew up, are also important. The       
> mower has a bumper strip, but that wouldn't stop it getting        
> stuck under benches, as John Swindle noted in his excellent        
> roomba/neato/mint analysis. I think the mower has roomba-style      
> downward-looking cliff detectors. Any decent solution needs        
> multiple defenses, but without good localization there's little     
> point in working on the "easier" problems because you can't get     
> to a working solution. Tackle the show-stopper problems first.      
> The robotics world is missing good and inexpensive localization     
> solutions. GPS is a partial solution but it will lie to your        
> face and tell you you're somewhere else, with high confidence,      
> and make the mower mow down the flower-bed, confident that it's      on lawn.

> ROS has a particle filter localization module which localizes      
> based on (lidar) ranges from objects in a previously mapped        
> space. I think a high-speed long-range lidar may have        
> application as a sensor to feed that algorithm.

> Regards

> Paul



> On 02/15/2015 06:38 PM, David           Anderson wrote:
>     
>            Thanks Paul,
>   
>            Just trying to get a feel for how this might be used.  
> 16cm           at 40m means 4cm, about 1 and 3/4 inch, at 10 meters.
> So,           unless the scans are jittered vertically,  nothing
> above or           below a 1 and 3/4" strip would be detected at 10
> meters, which           is still 30 feet away from the robot.   
>   
>            That might work well for walls or fences or tree trunks,
> but           would miss many (most?) real-world outdoor obstacles
> that are           higher or lower than a strip a couple of inches
> wide at 30           feet.   Curbs, for example, or low hanging
> branches.  The legs           of a picnic bench, but not the bench
> itself.   Chains of a           swing set, but not the swing.  And so on.
>   
>            And that little strip then becomes even more narrow as
> the           range closes, i.e., close to the robot, when you need
> it the           most.  At 2.5 meters,  (we're about to collide!)
> that strip is           1cm, about 1/2 inch, and nothing above or
> below that will be           detected.   Not that useful outdoors,
> in my experience, unless           your robot happens to be, you
> know,  an inch and 3/4 tall.            Otherwise, obstacles that
> might be detected at 10 meters           simply disappear as the
> robot gets closer.  Not a strategy for           success.
>   
>            So maybe you need to have a fancier rotating mount, one
> that           can pivot vertically to give a denser data set than
> just a           thin strip of the environment at some arbitrary
> height.   But           that would increase the sample time for a
> complete scan and           correspondingly increase the response time of the robot.
>   
>            If it were operating in a typical artificial indoor
> robot           environment (flat orthogonal walls, "objects" that
> are simple           cubes and cylinders sitting directly on the
> floor, etc,) it           would probably work fine.  
> Outdoors-real-world, I'd have a           lot of questions.
>   
>            I'm not sure what you can trust from such a tiny,
> thin-slice           sample of the environment.    How are you
> planning on using           this data?
>   
>            best regards,
>            dpa
>   
>   
>   
>   
> On 02/15/2015 03:22 PM, Paul             Bouchier wrote:
>     
>  Excellent question David. The Tx spec says             4mrad, so
> if I'm operating the calculator correctly, that's             a 16cm
> spot at 40m (both horizontally and vertically). Are             you
> thinking about narrow reflectors? Or about the fact that            
> a 1 rps (60rpm) system sampling at 2kHz would take a sample         
> every 0.18 degrees (3mrad), thereby giving overlapping             coverage?
>   
>              Paul
>   
>   
> On 02/14/2015 12:39 PM, David               Anderson wrote:
>     
>                Do you what the vertical spread of the beam is?
>   
>                thanks,
>                dpa
>   
>   
> On 02/14/2015 09:46 AM, Paul                 Bouchier wrote:
>     
>  FYI - I saw a post from the LIDAR-lite                 folks
> posting on RoboBill's post of a similar rotating                
> platform, and they said that in the first quarter                
> they'll start shipping units with a 2kHz scan rate.                
> Here's the URL - look for the post by Dennis Corey.
>  
> http://diydrones.com/group/ardurover-user-group/forum/topics/contributing-to-giving-sight-to-av-s?commentId=705844%3AComment%3A1870054&groupId=705844%3AGroup%3A903163
>                  That's more like what we need for a scanning lidar suitable for outdoor work.
>                  Paul
>   
>   
>   
> On 02/02/2015 09:45 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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-- 
Best regards,
 Charles Thurston                          mailto:cthurston at sc.rr.com

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