[Dprglist] Fwd: LF intersection angle rule

Dan Miner miner at zmail0.centtech.com
Wed Dec 13 11:23:39 PST 2017

Ha – When I went to watch the video below, an ad for a Storm Trooper robot 
popped up:


Looks like it will cost $300. 

-          Dan

From: DPRGlist [mailto:dprglist-bounces at lists.dprg.org] On Behalf Of David 
Sent: Sunday, December 10, 2017 11:52 AM
To: Doug Paradis
Subject: Re: [Dprglist] Fwd: LF intersection angle rule

I did see Ron's robot demo, and interesting contrast between his approach 
and Carl's, though Carl's is admittedly a simulation at this point.

Carl says that this year he is going to "get physical" so I was about to 
post a link to Olivia Newton-John's "Let's Get Physical" as a theme song. 
But then I went back and read the lyrics, and all the thinly and 
not-so-thinly  veiled innuendo from 1980's disco seem oddly discordant in 
today's cultural environment ("I've been patient, I've been good.  Trying to 
keep my hands on the table").

So instead I offer the following, in keeping with the line-following theme 
and the observation that all robot contests eventually devolve into races. 
Even if the requirements are, say, that only line-following WALKING robots 
are allowed:



On 12/10/2017 11:32 AM, Doug Paradis wrote:


       From watching actual robots run the stain elements, I know that it 
very possible for the robot to follow the outside edge of the stain and 
recover the line on the opposite side (my robot did this for one). Following 
this path the robot would be considered not following the line. Again after 
watching multiple robots navigate the S curves, it is easy to see if the 
robot is following the line (I.e., swaying with the S curve) versus just 
cutting across the center line (i.e., not following the line). I agree that 
bigger robots, those with wheel bases larger than the maximum radius of 
curve used in the course (i.e., 6 inches), might not be as responsive as the 
smaller robots. However, I still believe that you can tell when they are not 
following the line.

     BTW, did you see Ron's robot demo on Saturday? His robot was doing 
pretty well. I think the course he was running had a S curve which he 
handled without issue. The practice course didn't have any stains, if I 
recall right.


Doug P,

On Sun, Dec 10, 2017 at 10:49 AM, David Anderson <davida at smu.edu> wrote:

Thanks Doug,

I'm not sure I follow your examples (pun intended!).

For the segmented S curves, the difference between following the arc and 
following straight line approximations of that arc are pretty small, and 
likely to be indistinguishable from Ron's robot's path, for example. 
Similarly, each of the stains on the published "challenge" course is on a 
straight line segment between the entry point and exit point, so the paths 
would be identical in both cases.

For a robot with a base the size of the tiles, I'm not sure there would be 
any difference at all, unless the rules require that the "exact center" of 
the robot must remain on the line, in which case I don't see how either 
Carl's approach or Ron's would qualify.

This is just an intellectual exercise, I'm not planning on fielding such a 


On 12/10/2017 10:06 AM, Doug Paradis wrote:


      Going from entry point to exit point is not considered enough. You 
have to follow the line. For example, the segmented S curves, the robot 
needs to follow the curve  and make an S type movement. Another example is 
the stain elements, the robot needs to follow the line across the stain not 
follow the outside edge of the stain.


Doug P.

On Sun, Dec 10, 2017 at 1:11 AM, David Anderson <davida at smu.edu> wrote:

Great meeting today.

Doug, I have a question based on Ron and Carl's presentations, perhaps it 
has already been answered, to wit:

As I understand, the line following course consists of an assembly of square 
tiles, each of which has an entry and exit point.

Is it sufficient for the robot to just identify the entry and exit points, 
and drive directly from one to the other?

That is, it would not follow the line per se, though with sufficiently large 
robot the differences would probably be pretty negligible, but it would 
follow the course.


On 12/09/2017 08:18 AM, Doug Paradis wrote:


    Currently, the intersecting lines are always straight and all 
intersections are 90 degrees. Curves lines at an intersection would be a 
possible addition to further challenge courses (interesting idea). The link 
to the course layout is at

If you have any additional questions, let me know. I would love to see your 
work on the tests that you are developing.


Doug P.

On Sat, Dec 9, 2017 at 12:36 AM, John Swindle <swindle at compuserve.com> 


I'd say the crossing in your drawing was about either 30 degrees or 150 
degrees, and since it could come in on either side, I'd have to look for 
both. I am not asking that the rules state which side the angle is measured 
from. My issue is that I am developing a two-step test that covers all the 
conditions in the Challenge, but in the steps I need to include something 
that rejects the intersections. I am OK with rejecting any line that is 70 
degrees to 110 degrees on either side. If the intersecting line is straight, 
the test is a bit more robust. If each side is 70 to 110 degrees (a bent 
intersecting line), my two-step test might fail.

Doing it "that's just wrong" way,

John Swindle

-----Original Message-----
From: Doug Paradis <paradug at gmail.com>
To: John Swindle <swindle at compuserve.com>
Cc: DPRG <dprglist at lists.dprg.org>
Sent: Fri, Dec 8, 2017 11:52 pm
Subject: Re: LF intersection angle rule


    In the challenge course, all the intersections are 90 degrees. The rule 
was written to allow crossing variations in the future. I'm thinking that 
70-90 degrees would represent the smallest angle of the intersection. I not 
sure that is right, just the way I would interpret the angle.

if you saw an intersection that was like this:

           |   /

           | /


         / |

        /  |

       /   |

What angle would you say the intersection was?


Doug P.

On Fri, Dec 8, 2017 at 9:03 PM, John Swindle <swindle at compuserve.com> wrote:


The Line Following Challenge rules say "Intersections may cross with angles 
of 70 - 90 degrees." Doesn't that really mean 70 to 110 degrees? Is the 
intersecting line straight, or can it bend at the intersection?


John Swindle

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