<div dir="auto">Then we are per usual more in agreement than not.<div dir="auto"><br></div><div dir="auto">-not dpa</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sat, Oct 23, 2021, 1:22 PM David P. Anderson <<a href="mailto:davida@smu.edu">davida@smu.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div>
<p>Hello not Paul,</p>
<p>I think perhaps you missed the point I was attempting to make.
Not to put words in your mouth... :) I have no objections to
following a path or roadway, no matter how defined. My robots
can do that in several different ways, including following a
closely spaced set of waypoints. My point was more simply that
the robots are not in fact operating unconstrained, as in a
desert, as Paul's analogy suggests. I think that greatly
oversimplifies what they are doing.</p>
<p>Cheers!</p>
<p>-not Karim</p>
<p><br>
</p>
<div>On 10/23/21 1:14 PM, Karim Virani
wrote:<br>
</div>
<blockquote type="cite">
<p style="background-color:#f4eaa5;color:#000000;margin:5px;padding:2px;text-align:left!important;display:block;border:1px solid #000000;font-size:large;font-family:sans-serif"><strong><em style="font-size:11px"> [EXTERNAL SENDER]</em></strong></p>
<div dir="ltr">Try not to take this as putting words in Paul's
mouth. My guess is Paul was not trying to come up with a
rigorously defensible analogy, but accentuating a difference of
constraints in the moment of that conversation.<br>
<br>
In reality, we all place constraints on getting from here to
there. A path following constraint is just one example, but it's
almost never the only one. It's also not required. If you have
constraints against bumping into things instead of trying to
plough through them, then you probably have some sensors
involved. If you have a path following constraint there there
are also sensors involved in determining how far off the path
you have travelled. It could be GPS outside, it could be
odometry - could be a dozen other kinds of sensors. The path
could be described in different kinds of coordinate systems.
Paths may be defined with a different stickiness - how tightly
you have to cleave to them. There may be a different stickiness
per waypoint. A path can be described without waypoints - could
be formulaic.<br>
<br>
Adding path constraints may help with certain kinds of
navigation problems, could be unhelpful, or could be required.
It'll almost never be sufficient. Path planning can get you
around known obstacles (a building), less likely to encounter
obstacles (lane keeping), but won't be helpful in avoiding
collisions with dynamic obstacles (vehicles, people, donkeys).
And for highly planned paths, you have the burden of maintaining
that definition's correspondence with changing reality.<br>
<br>
Animals (including people) follow paths all the time. There are
all sorts of reasons to do so. There are also reasons to depart
from a path. It'll be a long time before robots can judge
dynamically which is the best approach in a given situation.
Until then, they follow the rules we lay out. But your robots
are following a path even if they only do it emergently. I'd
like to see them emergently avoid driving through a freshly
planted flower bed.<br>
<br>
Path planning is just something in our toolbox. Why not learn
how to use it? Figure out where it works best and where it
doesn't? The more I discover about it, it's not a single kind of
tool, it's a spectrum.<br>
<br>
<div>-not Paul</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sat, Oct 23, 2021 at 11:44
AM David P. Anderson via DPRGlist <<a href="mailto:dprglist@lists.dprg.org" target="_blank" rel="noreferrer">dprglist@lists.dprg.org</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi
Paul,<br>
<br>
I've been reflecting on your comments Tuesday evening about
the self <br>
driving trucks needing lots of waypoints to stay on the road,
vs. the <br>
robot demos shown that evening using more sparse waypoints.<br>
<br>
In particular the observation that the robots are operating
essentially <br>
unconstrained, as in a desert, except for the need to avoid
obstacles, <br>
while the trucks need to stay centered on the roadway.<br>
<br>
I'm not sure that is correct. It seems that the long hallways
that my <br>
robot had to navigate is the functional equivalent of the
trucks' <br>
roads. So the robot is not in fact operating as in a desert,
<br>
unconstrained. But must instead follow a fairly narrow and
constrained <br>
path.<br>
<br>
Now if that is the case, why does it not use hundreds
waypoints to <br>
accomplish that task? Or more to the point, why the army
trucks do?<br>
<br>
So I pondered this for a while and it occurred to me that in
the robots' <br>
case, the waypoint navigation is not responsible for keeping
the vehicle <br>
on the "road," i.e., centered in the hallway. Rather that is
the task <br>
of a separate group of sensors and behaviors. But for the
convoy, the <br>
navigation behavior is responsible for navigation in the
global sense as <br>
Chris was describing, and also in the local sense of staying
centered on <br>
the road.<br>
<br>
Now for the army trucks to do it the way the robots do would
also <br>
require a second suite of sensors and behaviors to stay on the
road --- <br>
not trivial --- while the method you describe can all be done
with just <br>
GPS, no other sensors required. (Though I assumed or maybe
you told me <br>
there are forward looking radar to keep from running into the
truck in <br>
front of you.)<br>
<br>
In any case, the desert vs. constrained roadway is perhaps not
the best <br>
analogy for what the robots are doing.<br>
<br>
cheers!<br>
<br>
David<br>
<br>
<br>
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</blockquote>
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