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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 2 19:36:06 CST 2015


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.


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 <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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>> http://list.dprg.org/mailman/listinfo/dprglist
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