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[DPRG] LiDAR-Lite 360 degree continuously rotating mount

Subject: [DPRG] LiDAR-Lite 360 degree continuously rotating mount
From: David Anderson davida at smu.edu
Date: Mon Feb 16 20:24:07 CST 2015

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 <http://mysticlakesoftware.com/>
> /
>
> 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 <mailto:davida at smu.edu>
>>>>>>> *Sent:* Monday, February 02, 2015 9:44 AM
>>>>>>> *To:* dprglist at dprg.org <mailto: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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