<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
<p>Murray raised some good points. Let me lay out the approach I
would take. It assumes something like a 50 msec loop period and a
robot speed that doesn't overrun the sensors at that rate. The
behaviors with highest to lowest:</p>
<ol>
<li>Intensity X Detected - drive(0,0)</li>
<li>Untrap - see discussion<br>
</li>
<li>Trap detected - initiate ballistic recovery - see discussion<br>
</li>
<li>No light detected - drive(x, -x) (rotate)<br>
</li>
<li>Left sensor detects object - see discussion</li>
<li>Right sensor detects object - see discussion</li>
<li>Forward sensor detects object - see discussion<br>
</li>
<li>Cruise - drive(x,x)</li>
</ol>
<p>Where <i>drive(left, right)</i> is the command to move.</p>
<p>There is an inherent assumption that the time between detection
and turning is sufficient to avoid collision. Tuning this can be
tricky. <br>
</p>
<p>The handling of object detection gets tricky real fast because
there are a number of possible situations. Some points:</p>
<ul>
<li>Forward object detection rotates until side sensor detects
object and continues turn. <br>
</li>
<ul>
<li>If the light is not visible the rotate to search for the
light may bring the object back into sensor range. This will
cause a cycling of turn, no light, rotate, sense object.</li>
<li>The turn triggers another forward sensing of an object.
Consider a corner or, worse, an alcove</li>
<li>One of the nasty situations is getting caught under a chair
where the legs trigger object detection and all turns cause
sensor triggers on the other legs.</li>
</ul>
</ul>
<p>The solutions are not viable with subsumption, per se. This gets
into the <i>ballistic</i> movement that Murray mentioned.
Ballistic movements aren't appropriate for regular tasks but are
sometimes needed to get out of unmanageable situations. A
ballistic movement is a movement based on time, distance, or
rotation, frequently all three. A ballistic movement has to be a
high priority task. It is also dangerous because it may require
ignoring some safety conditions, e.g. no object detection occurs
so the robot bumps into things. <br>
</p>
<p>Determining the need for a ballistic move requires tracking some
value which when exceeded triggers it. In a previous robot project
I was able to track the location of the robot. If the robot's
location did not change after a time period the <i>trap</i> task
took priority. It initiated a reverse movement and a large turn,
sometimes 180 degrees. The <i>untrap</i> task determined when the
ballistic move was completed. <br>
</p>
<div class="moz-signature"><font face="Comic Sans MS"
color="#000080"> <br>
-73 - <br>
<b>Rud Merriam K5RUD</b> <br>
<a href="http://mysticlakesoftware.com/"> <i>Mystic Lake
Software</i> </a> <br>
<br>
</font>
</div>
<div class="moz-cite-prefix">On 10/28/21 9:04 PM, Thalanayar
Muthukumar via DPRGlist wrote:<br>
</div>
<blockquote type="cite"
cite="mid:60035B1B-00A9-47AC-B56C-04F52A80B0C4@gmail.com">
<pre class="moz-quote-pre" wrap="">Today, I saw many mails on this topic.
I am a noob trying to wrap my head around this topic in a way that I can possibly implement reasonably quickly.
This is the scenario I am considering.
Robot is in a room with a light source at the opposite end of the room from where it starts. Overall robot objective - reach the light source. Robot has a light sensor and 3 ultrasonic sensors pointing front, right and left.
Basic behavior a - move forward for 30 secs
Basic behavior b - if any of the ultrasonic sensors detect an obstacle one feet from the robot, turn right 60 degrees
Basic behavior c - if light sensor senses light of intensity X, stop
Priority highest - Basic behavior c
Priority next - Basic behavior b
Priority lowest - Basic behavior a
If the robot is programmed to in every cycle, do one of the basic behaviors based on priority, it will meet the goal without any complex things like SLAM, as an example.
I am aware that the above list of 3 basic behaviors may not meet the overall goal and needs to be tweaked.
I am aware there are many books and videos by various people, but if I implement this on my robot, can I say I have implemented a behavior based robot (subsumption architecture)?
Regards.
- Kumar
Sent from my iPhone
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">On Oct 28, 2021, at 4:09 PM, <a class="moz-txt-link-abbreviated" href="mailto:dprglist-request@lists.dprg.org">dprglist-request@lists.dprg.org</a> wrote:
Send DPRGlist mailing list submissions to
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than "Re: Contents of DPRGlist digest..."
Today's Topics:
1. Re: Robotics "Capability Maturity Model" - Thoughts? (Pat Caron)
2. Re: self driving trucks and the desert (Rud Merriam)
3. On Behavior Trees [Was: self driving trucks and the desert]
(Murray Altheim)
4. Re: self driving trucks and the desert (David P. Anderson)
5. Re: self driving trucks and the desert (<a class="moz-txt-link-abbreviated" href="mailto:secretary@dprg.org">secretary@dprg.org</a>)
6. New Rpi zero 2 (Doug Paradis)
7. Re: Subsumption Discussion (Rud Merriam)
8. Re: On Behavior Trees [Was: self driving trucks and the
desert] (Rud Merriam)
9. Re: On Behavior Trees [Was: self driving trucks and the
desert] (Rud Merriam)
10. Re: Subsumption Discussion (David P. Anderson)
11. Re: On Behavior Trees [Was: self driving trucks and the
desert] (Murray Altheim)
12. Re: On Behavior Trees [Was: self driving trucks and the
desert] (Rud Merriam)
----------------------------------------------------------------------
Message: 1
Date: Wed, 27 Oct 2021 19:43:52 -0400
From: Pat Caron <a class="moz-txt-link-rfc2396E" href="mailto:patcaron@mail.com"><patcaron@mail.com></a>
To: <a class="moz-txt-link-rfc2396E" href="mailto:dprglist@lists.dprg.org">"dprglist@lists.dprg.org"</a> <a class="moz-txt-link-rfc2396E" href="mailto:dprglist@lists.dprg.org"><dprglist@lists.dprg.org></a>
Subject: Re: [Dprglist] Robotics "Capability Maturity Model" -
Thoughts?
Message-ID:
<a class="moz-txt-link-rfc2396E" href="mailto:CA+mr86dRL58x1digEdtWxDQn=PU+jzJFf12+AdYsuYrnA4baYw@mail.gmail.com"><CA+mr86dRL58x1digEdtWxDQn=PU+jzJFf12+AdYsuYrnA4baYw@mail.gmail.com></a>
Content-Type: text/plain; charset="utf-8"
I agree with Jim. DPRG has opened up a group of people with vast knowledge
on all
disciplines required to build robots. This is invaluable for us that are
remotely located.
Thank you DPRG!
Pat Caron
Ontario, Canada
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">On Wed, Oct 27, 2021 at 2:13 PM Jim Merkle via DPRGlist <
<a class="moz-txt-link-abbreviated" href="mailto:dprglist@lists.dprg.org">dprglist@lists.dprg.org</a>> wrote:
If any of you subscribe to Reddit - Arduino group, you'll see generic
questions all the time, many of which are from "tire kickers", folks just
thinking about purchasing something but haven't committed to anything yet.
I don't bother getting involved unless the user indicates they have actual
hardware they are working with.
Since Kumar had already purchased an STM32 NUCLEO board, (I love the STM32
NUCLEO boards in general), I had to get involved.
"Which development environment" is the 2nd most asked question when it
comes to STM32 boards. The most asked is "which STM32 board?".
Unfortunately, many folks begin STM32 exploration with a "Blue Pill". I
HATE that platform!!! Although it's cheap, they often have clone chips and
require plenty of additional hardware already provided with a NUCLEO board.
Much of the capability model involves the individual and their talent
set...
What DPRG provides is mentorship... Folks that are willing and able to
help others get from one *Level* to the next. Thanks GUYS !
The "Build More Robots" is an excellent tool / program to help bring
people (and their robots) from "Level 0.0.0" to "Level 5.0" (or so).
<a class="moz-txt-link-freetext" href="https://www.dprg.org/build-more-robots-series/">https://www.dprg.org/build-more-robots-series/</a>
I truly appreciate DPRG !
---
Jim Merkle
Carrollton, TX 75007
<a class="moz-txt-link-abbreviated" href="mailto:jim@merkles.com">jim@merkles.com</a>
On 2021-10-27 10:03, Chris N via DPRGlist wrote:
So in part because of questions along the line of "where do I get started"
from Kumar, and others before him, that we occasionally get, I thought it
might help to have some sort of capability model in mind that can be
referenced.
That way one can ask "OK - what level are you at currently? What level
are you trying to reach in the near term?"
Below is what I mean. For now this is focused on software and locomotion
(but starting with Level 8, perception comes into the picture)
I have more explanation to go along with each item but wanted to keep it
brief in this e-mail.
The idea is not to explain how to do these things. This just represents
milestones along the journey. This is really more about having an agreed
upon vocabulary.
Thoughts? Is something like this helpful to have written down? Is it
already written down somewhere ? (I am sure that in some ways, this is
captured in some of the material that David Anderson has published over the
years)
Level 0: I have an API through which I can control the speed and direction
of the individual wheels. My robot can move!
Level 1: I have an API through which I can reliably get the incremental
encoder counts for each wheel. When motors are commanded with a certain
duty cycle, I can measure what that translates to in terms of encoder
counts per time unit.
Level 2: I am keeping track of my Robot's X, Y and Theta via
dead-reckoning / odometry
Level 3: I have taken at least basic steps to calibrate my robot's
odometry calculations.
Level 4: I can command the robot to move, but using more abstract units
such as "meters/second" or at least "encoder ticks per time unit"
Level 5: My robot actually moves at the linear and angular velocity I tell
it to, even when battery voltage is lower or surface friction is higher.
And because I have completed Level 3, it can go in a somewhat straight
line when I ask it to.
Level 6: My robot moves in a fairly smooth fashion, i.e. it changes speed
and direction somewhat gradually. Movement is not "robotic"
Level 7: I can command my robot to go to a certain X,Y coordinate aka
waypoint relative to its current location, and the robot more or less
reaches that location provided nothing is in the way
Level 8: My robot can reach the target location, even if there are
obstacles in the way.
Level 9: My robot can come back after reaching its destination.
Level 10: My robot can do all this, even if the obstacles are moving
around quite a bit or if there are other sources of possible confusion
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_______________________________________________
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<a class="moz-txt-link-freetext" href="http://lists.dprg.org/listinfo.cgi/dprglist-dprg.org">http://lists.dprg.org/listinfo.cgi/dprglist-dprg.org</a>
</pre>
</blockquote>
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Message: 2
Date: Wed, 27 Oct 2021 22:23:45 -0500
From: Rud Merriam <a class="moz-txt-link-rfc2396E" href="mailto:rudmerriam@gmail.com"><rudmerriam@gmail.com></a>
To: <a class="moz-txt-link-abbreviated" href="mailto:dprglist@lists.dprg.org">dprglist@lists.dprg.org</a>
Subject: Re: [Dprglist] self driving trucks and the desert
Message-ID: <a class="moz-txt-link-rfc2396E" href="mailto:01714593-ec67-c275-357e-46bf198b5680@gmail.com"><01714593-ec67-c275-357e-46bf198b5680@gmail.com></a>
Content-Type: text/plain; charset="utf-8"; Format="flowed"
I don't recall the details of what makes David's subsumption unique. In
my first NASA competition I used subsumption with a unique twist. There
was a behavior that would switch the subsumption list being used.
If you're not familiar with subsumption is is a list of behaviors or
actions. Every cycle the list begins again until one of the behaviors
"fires". The processing starts again at the beginning of the list.
That's simplified but gives the idea. I actually found that setting a
flag and letting the list finish processing also worked. Once the flag
was any following behavior would not "fire" but it could record
information. That was useful for handling behaviors that did a timing
function.
Since then I've moved to behavior trees (BT) which are used in robotics
and for autonomous actors in games. That shooter coming after you is
driven by a BT. Subsumption is actually subsumed (ha!) by BTs as one of
the techniques used in the trees.
Subsumption is basically an OR operation, just like a logic gate. If one
behavior fires the overall? gate becomes true and returns to a higher
level in the tree. There is also an AND operation where all the
behaviors must fire before returning true. If one fails to fire a false
is returned. The other main operation is NOT which is an inverter of the
output of a list.
There is a lot written about BTs but not as logic gates as I've
described them. I have code which does this but need to update it for
C++20. Once I complete that revision I want to look at learning using
BTs, i.e. adding new behaviors including expanding the trees. An
advantage of treating them as logic gates is boolean algebra is
applicable which allows simplifying trees using some well known
techniques. After learning a larger tree can be trimmed to a more
compact but logically equivalent representation.
-73 -
*Rud Merriam K5RUD*
/Mystic Lake Software/ <a class="moz-txt-link-rfc2396E" href="http://mysticlakesoftware.com/"><http://mysticlakesoftware.com/></a>
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">Thanks for the reply.? I think that perhaps part of the reality is
that I have developed a subsumption based reactive navigation method
that I believe is fairly unique --- the only other people I've
encountered that do the same have learned it from me.
</pre>
</blockquote>
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------------------------------
Message: 3
Date: Thu, 28 Oct 2021 20:19:15 +1300
From: Murray Altheim <a class="moz-txt-link-rfc2396E" href="mailto:murray18@altheim.com"><murray18@altheim.com></a>
To: <a class="moz-txt-link-abbreviated" href="mailto:dprglist@lists.dprg.org">dprglist@lists.dprg.org</a>
Subject: [Dprglist] On Behavior Trees [Was: self driving trucks and
the desert]
Message-ID: <a class="moz-txt-link-rfc2396E" href="mailto:7b1998a1-7bf6-e33a-9d1c-bc9ecc78d25a@altheim.com"><7b1998a1-7bf6-e33a-9d1c-bc9ecc78d25a@altheim.com></a>
Content-Type: text/plain; charset=utf-8; format=flowed
On 28/10/21 4:23 pm, Rud Merriam via DPRGlist wrote:
[...]
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">Since then I've moved to behavior trees (BT) which are used in
robotics and for autonomous actors in games. That shooter coming
after you is driven by a BT. Subsumption is actually subsumed
(ha!) by BTs as one of the techniques used in the trees.
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">Hi Rud,
For those curious could you provide any academic (or non-academic) papers
describing Behaviour Trees, any known implementations in existing online
projects, code repositories, etc. that we might follow up on to learn more?
Cheers,
Murray
...........................................................................
Murray Altheim <murray18 at altheim dot com> = = ===
<a class="moz-txt-link-freetext" href="http://www.altheim.com/murray/">http://www.altheim.com/murray/</a> === ===
= = ===
In the evening
The rice leaves in the garden
Rustle in the autumn wind
That blows through my reed hut.
-- Minamoto no Tsunenobu
------------------------------
Message: 4
Date: Thu, 28 Oct 2021 08:35:48 -0500
From: "David P. Anderson" <a class="moz-txt-link-rfc2396E" href="mailto:davida@smu.edu"><davida@smu.edu></a>
To: <a class="moz-txt-link-rfc2396E" href="mailto:dprglist@lists.dprg.org"><dprglist@lists.dprg.org></a>
Subject: Re: [Dprglist] self driving trucks and the desert
Message-ID: <a class="moz-txt-link-rfc2396E" href="mailto:85af30b6-5045-9600-b756-bad65527cd9e@smu.edu"><85af30b6-5045-9600-b756-bad65527cd9e@smu.edu></a>
Content-Type: text/plain; charset="utf-8"; format=flowed
Howdy DPRG
On 10/27/21 10:23 PM, Rud Merriam via DPRGlist wrote:
[snip]
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">
If you're not familiar with subsumption is is a list of behaviors or
actions. Every cycle the list begins again until one of the behaviors
"fires". The processing starts again at the beginning of the list.
That's simplified but gives the idea. I actually found that setting a
flag and letting the list finish processing also worked. Once the flag
was any following behavior would not "fire" but it could record
information. That was useful for handling behaviors that did a timing
function.
[snip]
Subsumption is basically an OR operation, just like a logic gate. If
one behavior fires the overall? gate becomes true and returns to a
higher level in the tree. There is also an AND operation where all the
behaviors must fire before returning true. If one fails to fire a
false is returned. The other main operation is NOT which is an
inverter of the output of a list.
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">If you're not familiar with subsumption,? the above is not an accurate
description.? At all.?? ;)
For those who might be interested, the Joseph Jones books "Mobile
Robots" and "Behavior Based Robotics" provide sort of the canonical
definitions for subsumption and how it works.? If you don't want to read
that much then I think I did a pretty good job of describing it in the
DPRG talk from last June, for which there is a YouTube video on the club
web page, (miss-labeled "May 12" rather than "June 12").
cheers!
David
------------------------------
Message: 5
Date: Thu, 28 Oct 2021 10:40:36 -0500
From: <a class="moz-txt-link-rfc2396E" href="mailto:secretary@dprg.org">"secretary@dprg.org"</a> <a class="moz-txt-link-rfc2396E" href="mailto:secretary@dprg.org"><secretary@dprg.org></a>
To: "David P. Anderson" <a class="moz-txt-link-rfc2396E" href="mailto:davida@smu.edu"><davida@smu.edu></a>
Cc: DPRG <a class="moz-txt-link-rfc2396E" href="mailto:dprglist@lists.dprg.org"><dprglist@lists.dprg.org></a>
Subject: Re: [Dprglist] self driving trucks and the desert
Message-ID:
<a class="moz-txt-link-rfc2396E" href="mailto:CAOdUW+bQqJOOb6m5URBq0FDajP+dRGiW97=iq8kvqHmrcCc4Qw@mail.gmail.com"><CAOdUW+bQqJOOb6m5URBq0FDajP+dRGiW97=iq8kvqHmrcCc4Qw@mail.gmail.com></a>
Content-Type: text/plain; charset="utf-8"
-All,
David's video is actually titled "Implementing Robot Waypoint
Navigation by David Anderson ? DPRG Virtual Monthly Meeting, 6/12/2021".
However, the video introduction does list the date as May 12th. When
searching for the video use the title above, do not search for May 12th.
Excellent presentation.
Regards,
Doug P.
On Thu, Oct 28, 2021 at 8:35 AM David P. Anderson via DPRGlist <
<a class="moz-txt-link-abbreviated" href="mailto:dprglist@lists.dprg.org">dprglist@lists.dprg.org</a>> wrote:
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">Howdy DPRG
On 10/27/21 10:23 PM, Rud Merriam via DPRGlist wrote:
[snip]
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">
If you're not familiar with subsumption is is a list of behaviors or
actions. Every cycle the list begins again until one of the behaviors
"fires". The processing starts again at the beginning of the list.
That's simplified but gives the idea. I actually found that setting a
flag and letting the list finish processing also worked. Once the flag
was any following behavior would not "fire" but it could record
information. That was useful for handling behaviors that did a timing
function.
[snip]
Subsumption is basically an OR operation, just like a logic gate. If
one behavior fires the overall gate becomes true and returns to a
higher level in the tree. There is also an AND operation where all the
behaviors must fire before returning true. If one fails to fire a
false is returned. The other main operation is NOT which is an
inverter of the output of a list.
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">If you're not familiar with subsumption, the above is not an accurate
description. At all. ;)
For those who might be interested, the Joseph Jones books "Mobile
Robots" and "Behavior Based Robotics" provide sort of the canonical
definitions for subsumption and how it works. If you don't want to read
that much then I think I did a pretty good job of describing it in the
DPRG talk from last June, for which there is a YouTube video on the club
web page, (miss-labeled "May 12" rather than "June 12").
cheers!
David
_______________________________________________
DPRGlist mailing list
<a class="moz-txt-link-abbreviated" href="mailto:DPRGlist@lists.dprg.org">DPRGlist@lists.dprg.org</a>
<a class="moz-txt-link-freetext" href="http://lists.dprg.org/listinfo.cgi/dprglist-dprg.org">http://lists.dprg.org/listinfo.cgi/dprglist-dprg.org</a>
</pre>
</blockquote>
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Message: 6
Date: Thu, 28 Oct 2021 10:49:34 -0500
From: Doug Paradis <a class="moz-txt-link-rfc2396E" href="mailto:paradug@gmail.com"><paradug@gmail.com></a>
To: DPRG <a class="moz-txt-link-rfc2396E" href="mailto:dprglist@lists.dprg.org"><dprglist@lists.dprg.org></a>
Subject: [Dprglist] New Rpi zero 2
Message-ID:
<a class="moz-txt-link-rfc2396E" href="mailto:CAOdUW+YXcdSQ=cyFTG2VYahRHU9Kj_U=GgpAk0m25e0JdwWJMw@mail.gmail.com"><CAOdUW+YXcdSQ=cyFTG2VYahRHU9Kj_U=GgpAk0m25e0JdwWJMw@mail.gmail.com></a>
Content-Type: text/plain; charset="utf-8"
-All,
Just in case you missed the announcement.
<a class="moz-txt-link-freetext" href="https://makezine.com/2021/10/27/eben-upton-raspberry-pi-exciting-year-new-pi-zero-2-w/">https://makezine.com/2021/10/27/eben-upton-raspberry-pi-exciting-year-new-pi-zero-2-w/</a>
Regards,
Doug P.
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Message: 7
Date: Thu, 28 Oct 2021 13:13:34 -0500
From: Rud Merriam <a class="moz-txt-link-rfc2396E" href="mailto:rudmerriam@gmail.com"><rudmerriam@gmail.com></a>
To: <a class="moz-txt-link-abbreviated" href="mailto:dprglist@lists.dprg.org">dprglist@lists.dprg.org</a>
Subject: Re: [Dprglist] Subsumption Discussion
Message-ID: <a class="moz-txt-link-rfc2396E" href="mailto:e0402033-8ce9-6e46-c8b1-d6f82aaca113@gmail.com"><e0402033-8ce9-6e46-c8b1-d6f82aaca113@gmail.com></a>
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David,
I'd like to discuss where we differ on the definition of subsumption.
I'm looking at your page on subsumption
<a class="moz-txt-link-freetext" href="https://www.dprg.org/articles/2007-03a/">https://www.dprg.org/articles/2007-03a/</a> since I don't have the books you
are referencing. (Actually, I found a PDF of "Mobile Robots" at
<a class="moz-txt-link-freetext" href="https://cs.au.dk/~ocaprani/legolab/DigitalControl.dir/NXT/Lesson9.dir/11128_Mobile_Robots_Inspiration_to_Implementation-Flynn_and_Jones.pdf">https://cs.au.dk/~ocaprani/legolab/DigitalControl.dir/NXT/Lesson9.dir/11128_Mobile_Robots_Inspiration_to_Implementation-Flynn_and_Jones.pdf</a>"
The book I started from was elementary and I disposed of it during a
recent move. I have read much on the web about subsumption and BTs, and
have implemented BTs for robotics work.
You refer to layers which I call behaviors. Rodney Brooks original paper
often conflated the two.
Looking at your section III. Arbitration you say:
Subsumption tasks are arranged by priority, from lowest to highest,
as determined by the robot builder for a particular problem set.? An
arbitrator() selects the output of the highest priority task whose
flag is true to pass on to the physical subsystem (motors or
whatever) for this pass through the loop, this 20th of a second.
Low priority tasks can only control the robot when all higher
priority tasks' flags are false.
My description would be:
Behaviors are listed in order of priority from highest to lowest.
Once the list is processed the highest priority task that 'fires' is
given control of the system. The default behavior is the last on the
list.
Although my original reading of subsumption was that the entire list was
not processed but control passed once a behavior fired. I modified this
to process the entire list. Thus, my original understanding may have
been incorrect but I in inadvertently changed to the correct processing.
You provide code from Flynn and Jones:
void arbitrate()
{
while (1) {
if (cruise_output_flag == 1)
{motor_input = cruise_output; }
if (follow_output_flag == 1)
{motor_input = follow_output; }
if (avoid_output_flag == 1)
{motor_input = avoid_output; }
if (escape_output_flag == 1)
{motor_input = escape_output; }
sleep(tick);
}
}
I assert that this is an OR process with the caveat that the default
behavior always results in a true condition so it has control. BTs are
more complex having multiple lists to process so a given set of
behaviors (layer) is not likely to have a default behavior. Subsumption
is a /sequence/ in a BT. From
<a class="moz-txt-link-freetext" href="https://www.gamedeveloper.com/programming/behavior-trees-for-ai-how-they-work">https://www.gamedeveloper.com/programming/behavior-trees-for-ai-how-they-work</a>
Their main power comes from their ability to represent multiple
different courses of action, in order of priority from most
favorable to least favorable, and to return success if it managed to
succeed at any course of action.
We may simply have a difference in terminology, as above, and
implementation details.
-73 -
*Rud Merriam K5RUD*
/Mystic Lake Software/ <a class="moz-txt-link-rfc2396E" href="http://mysticlakesoftware.com/"><http://mysticlakesoftware.com/></a>
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">On 10/28/21 8:35 AM, David P. Anderson via DPRGlist wrote:
Howdy DPRG
On 10/27/21 10:23 PM, Rud Merriam via DPRGlist wrote:
[snip]
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">
If you're not familiar with subsumption is is a list of behaviors or
actions. Every cycle the list begins again until one of the behaviors
"fires". The processing starts again at the beginning of the list.
That's simplified but gives the idea. I actually found that setting a
flag and letting the list finish processing also worked. Once the
flag was any following behavior would not "fire" but it could record
information. That was useful for handling behaviors that did a timing
function.
[snip]
Subsumption is basically an OR operation, just like a logic gate. If
one behavior fires the overall? gate becomes true and returns to a
higher level in the tree. There is also an AND operation where all
the behaviors must fire before returning true. If one fails to fire a
false is returned. The other main operation is NOT which is an
inverter of the output of a list.
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">If you're not familiar with subsumption,? the above is not an accurate
description.? At all.?? ;)
For those who might be interested, the Joseph Jones books "Mobile
Robots" and "Behavior Based Robotics" provide sort of the canonical
definitions for subsumption and how it works.? If you don't want to
read that much then I think I did a pretty good job of describing it
in the DPRG talk from last June, for which there is a YouTube video on
the club web page, (miss-labeled "May 12" rather than "June 12").
cheers!
David
_______________________________________________
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</pre>
</blockquote>
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------------------------------
Message: 8
Date: Thu, 28 Oct 2021 13:36:37 -0500
From: Rud Merriam <a class="moz-txt-link-rfc2396E" href="mailto:rudmerriam@gmail.com"><rudmerriam@gmail.com></a>
To: <a class="moz-txt-link-abbreviated" href="mailto:dprglist@lists.dprg.org">dprglist@lists.dprg.org</a>
Subject: Re: [Dprglist] On Behavior Trees [Was: self driving trucks
and the desert]
Message-ID: <a class="moz-txt-link-rfc2396E" href="mailto:4a2d258f-eedd-03a7-f21e-98eaea07721b@gmail.com"><4a2d258f-eedd-03a7-f21e-98eaea07721b@gmail.com></a>
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I replied to David and included this link:
<a class="moz-txt-link-freetext" href="https://www.gamedeveloper.com/programming/behavior-trees-for-ai-how-they-work">https://www.gamedeveloper.com/programming/behavior-trees-for-ai-how-they-work</a>
Here is a direct link to a C++ implementation I created:
<a class="moz-txt-link-freetext" href="https://bitbucket.org/rmerriam/devr/src/master/robot/mystic_bt/include/">https://bitbucket.org/rmerriam/devr/src/master/robot/mystic_bt/include/</a>
A python implementation:
<a class="moz-txt-link-freetext" href="https://github.com/ToyotaResearchInstitute/task_behavior_engine">https://github.com/ToyotaResearchInstitute/task_behavior_engine</a> Haven't
looked at this in detail so caveat emptor.
Here is another more academic article which shows how subsumption is a
/sequence/ in BTs:
<a class="moz-txt-link-freetext" href="https://www.semanticscholar.org/paper/A-Survey-of-Behavior-Trees-in-Robotics-and-AI-Iovino-Scukins/595c7aeb6a9c9033a68aff1b25067ce967ea2a77">https://www.semanticscholar.org/paper/A-Survey-of-Behavior-Trees-in-Robotics-and-AI-Iovino-Scukins/595c7aeb6a9c9033a68aff1b25067ce967ea2a77</a>
You have to sign up for Research Gate but that is free.
-73 -
*Rud Merriam K5RUD*
/Mystic Lake Software/ <a class="moz-txt-link-rfc2396E" href="http://mysticlakesoftware.com/"><http://mysticlakesoftware.com/></a>
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">On 10/28/21 2:19 AM, Murray Altheim via DPRGlist wrote:
On 28/10/21 4:23 pm, Rud Merriam via DPRGlist wrote:
[...]
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">Since then I've moved to behavior trees (BT) which are used in
robotics and for autonomous actors in games. That shooter coming
after you is driven by a BT. Subsumption is actually subsumed (ha!)
by BTs as one of the techniques used in the trees.
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">Hi Rud,
For those curious could you provide any academic (or non-academic) papers
describing Behaviour Trees, any known implementations in existing online
projects, code repositories, etc. that we might follow up on to learn
more?
Cheers,
Murray
...........................................................................
Murray Altheim <murray18 at altheim dot com>?????????????????????? =
=? ===
<a class="moz-txt-link-freetext" href="http://www.altheim.com/murray/">http://www.altheim.com/murray/</a> ===? ===
= =? ===
??? In the evening
??? The rice leaves in the garden
??? Rustle in the autumn wind
??? That blows through my reed hut.
?????????? -- Minamoto no Tsunenobu
_______________________________________________
DPRGlist mailing list
<a class="moz-txt-link-abbreviated" href="mailto:DPRGlist@lists.dprg.org">DPRGlist@lists.dprg.org</a>
<a class="moz-txt-link-freetext" href="http://lists.dprg.org/listinfo.cgi/dprglist-dprg.org">http://lists.dprg.org/listinfo.cgi/dprglist-dprg.org</a>
</pre>
</blockquote>
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------------------------------
Message: 9
Date: Thu, 28 Oct 2021 13:38:09 -0500
From: Rud Merriam <a class="moz-txt-link-rfc2396E" href="mailto:rudmerriam@gmail.com"><rudmerriam@gmail.com></a>
To: <a class="moz-txt-link-abbreviated" href="mailto:dprglist@lists.dprg.org">dprglist@lists.dprg.org</a>
Subject: Re: [Dprglist] On Behavior Trees [Was: self driving trucks
and the desert]
Message-ID: <a class="moz-txt-link-rfc2396E" href="mailto:f12819e9-eadf-e8fc-92af-a7155c82ccca@gmail.com"><f12819e9-eadf-e8fc-92af-a7155c82ccca@gmail.com></a>
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Sorry, wrong link on the one article on Research Gate. It was the one
that lead me to the correct one:
<a class="moz-txt-link-freetext" href="https://www.researchgate.net/publication/309616544_How_Behavior_Trees_Modularize_Hybrid_Control_Systems_and_Generalize_Sequential_Behavior_Compositions_the_Subsumption_Architecture_and_Decision_Trees">https://www.researchgate.net/publication/309616544_How_Behavior_Trees_Modularize_Hybrid_Control_Systems_and_Generalize_Sequential_Behavior_Compositions_the_Subsumption_Architecture_and_Decision_Trees</a>
-73 -
*Rud Merriam K5RUD*
/Mystic Lake Software/ <a class="moz-txt-link-rfc2396E" href="http://mysticlakesoftware.com/"><http://mysticlakesoftware.com/></a>
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">On 10/28/21 2:19 AM, Murray Altheim via DPRGlist wrote:
On 28/10/21 4:23 pm, Rud Merriam via DPRGlist wrote:
[...]
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">Since then I've moved to behavior trees (BT) which are used in
robotics and for autonomous actors in games. That shooter coming
after you is driven by a BT. Subsumption is actually subsumed (ha!)
by BTs as one of the techniques used in the trees.
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">Hi Rud,
For those curious could you provide any academic (or non-academic) papers
describing Behaviour Trees, any known implementations in existing online
projects, code repositories, etc. that we might follow up on to learn
more?
Cheers,
Murray
...........................................................................
Murray Altheim <murray18 at altheim dot com>?????????????????????? =
=? ===
<a class="moz-txt-link-freetext" href="http://www.altheim.com/murray/">http://www.altheim.com/murray/</a> ===? ===
= =? ===
??? In the evening
??? The rice leaves in the garden
??? Rustle in the autumn wind
??? That blows through my reed hut.
?????????? -- Minamoto no Tsunenobu
_______________________________________________
DPRGlist mailing list
<a class="moz-txt-link-abbreviated" href="mailto:DPRGlist@lists.dprg.org">DPRGlist@lists.dprg.org</a>
<a class="moz-txt-link-freetext" href="http://lists.dprg.org/listinfo.cgi/dprglist-dprg.org">http://lists.dprg.org/listinfo.cgi/dprglist-dprg.org</a>
</pre>
</blockquote>
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------------------------------
Message: 10
Date: Thu, 28 Oct 2021 13:50:04 -0500
From: "David P. Anderson" <a class="moz-txt-link-rfc2396E" href="mailto:davida@smu.edu"><davida@smu.edu></a>
To: <a class="moz-txt-link-rfc2396E" href="mailto:dprglist@lists.dprg.org"><dprglist@lists.dprg.org></a>
Subject: Re: [Dprglist] Subsumption Discussion
Message-ID: <a class="moz-txt-link-rfc2396E" href="mailto:97ecf3de-12b3-6373-0b6c-5994edcf242c@smu.edu"><97ecf3de-12b3-6373-0b6c-5994edcf242c@smu.edu></a>
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Hi Rud,
Ok, that sounds good to me.? Different descriptions of basically the
same thing.?? I'd be more inclined to emphasize the "subsume" nature of
subsumption and it's ramifications, which are pretty deep once you
scratch the surface.
cheers!
David
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">On 10/28/21 1:13 PM, Rud Merriam via DPRGlist wrote:
*/[EXTERNAL SENDER]/*
David,
I'd like to discuss where we differ on the definition of subsumption.
I'm looking at your page on subsumption
<a class="moz-txt-link-freetext" href="https://www.dprg.org/articles/2007-03a/">https://www.dprg.org/articles/2007-03a/</a> since I don't have the books
you are referencing. (Actually, I found a PDF of "Mobile Robots" at
<a class="moz-txt-link-freetext" href="https://cs.au.dk/~ocaprani/legolab/DigitalControl.dir/NXT/Lesson9.dir/11128_Mobile_Robots_Inspiration_to_Implementation-Flynn_and_Jones.pdf">https://cs.au.dk/~ocaprani/legolab/DigitalControl.dir/NXT/Lesson9.dir/11128_Mobile_Robots_Inspiration_to_Implementation-Flynn_and_Jones.pdf</a>"
The book I started from was elementary and I disposed of it during a
recent move. I have read much on the web about subsumption and BTs,
and have implemented BTs for robotics work.
You refer to layers which I call behaviors. Rodney Brooks original
paper often conflated the two.
Looking at your section III. Arbitration you say:
Subsumption tasks are arranged by priority, from lowest to
highest, as determined by the robot builder for a particular
problem set.? An arbitrator() selects the output of the highest
priority task whose flag is true to pass on to the physical
subsystem (motors or whatever) for this pass through the loop,
this 20th of a second.
Low priority tasks can only control the robot when all higher
priority tasks' flags are false.
My description would be:
Behaviors are listed in order of priority from highest to lowest.
Once the list is processed the highest priority task that 'fires'
is given control of the system. The default behavior is the last
on the list.
Although my original reading of subsumption was that the entire list
was not processed but control passed once a behavior fired. I modified
this to process the entire list. Thus, my original understanding may
have been incorrect but I in inadvertently changed to the correct
processing.
You provide code from Flynn and Jones:
void arbitrate()
{
while (1) {
if (cruise_output_flag == 1)
{motor_input = cruise_output; }
if (follow_output_flag == 1)
{motor_input = follow_output; }
if (avoid_output_flag == 1)
{motor_input = avoid_output; }
if (escape_output_flag == 1)
{motor_input = escape_output; }
sleep(tick);
}
}
I assert that this is an OR process with the caveat that the default
behavior always results in a true condition so it has control. BTs are
more complex having multiple lists to process so a given set of
behaviors (layer) is not likely to have a default behavior.
Subsumption is a /sequence/ in a BT. From
<a class="moz-txt-link-freetext" href="https://www.gamedeveloper.com/programming/behavior-trees-for-ai-how-they-work">https://www.gamedeveloper.com/programming/behavior-trees-for-ai-how-they-work</a>
Their main power comes from their ability to represent multiple
different courses of action, in order of priority from most
favorable to least favorable, and to return success if it managed
to succeed at any course of action.
We may simply have a difference in terminology, as above, and
implementation details.
-73 -
*Rud Merriam K5RUD*
/Mystic Lake Software/
<a class="moz-txt-link-rfc2396E" href="http://secure-web.cisco.com/1FKz_X0Ge1ie37k5LHDucUXiDVc-D1xvohLqcTDESE8BjeMVz7ksqQwfV3iUyqpDovtR-0-tn_yo8xt3L2xqvqvv1McOdn6AJOJQ-sFHYPgpnyZbMrjcS1zL51KTf7SbGRDPmH40a1teuLnvGDFDeNOk23sIq4YNsSUIGc-VZkskk0UV7LZfvdcOt95nBziNnV4YwBopI_dF6oloKbUyhiVLmT4A_2qMkmYYIVGNbo_menDPskLCcvqr7VqB-Q-sN4obSw-KecZ1m1TTzyy0Hz9W-oraDa2B2qGphSnHGPY4/http%3A%2F%2Fmysticlakesoftware.com%2F"><http://secure-web.cisco.com/1FKz_X0Ge1ie37k5LHDucUXiDVc-D1xvohLqcTDESE8BjeMVz7ksqQwfV3iUyqpDovtR-0-tn_yo8xt3L2xqvqvv1McOdn6AJOJQ-sFHYPgpnyZbMrjcS1zL51KTf7SbGRDPmH40a1teuLnvGDFDeNOk23sIq4YNsSUIGc-VZkskk0UV7LZfvdcOt95nBziNnV4YwBopI_dF6oloKbUyhiVLmT4A_2qMkmYYIVGNbo_menDPskLCcvqr7VqB-Q-sN4obSw-KecZ1m1TTzyy0Hz9W-oraDa2B2qGphSnHGPY4/http%3A%2F%2Fmysticlakesoftware.com%2F></a>
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">On 10/28/21 8:35 AM, David P. Anderson via DPRGlist wrote:
Howdy DPRG
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">On 10/27/21 10:23 PM, Rud Merriam via DPRGlist wrote:
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">
[snip]
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">
If you're not familiar with subsumption is is a list of behaviors or
actions. Every cycle the list begins again until one of the
behaviors "fires". The processing starts again at the beginning of
the list. That's simplified but gives the idea. I actually found
that setting a flag and letting the list finish processing also
worked. Once the flag was any following behavior would not "fire"
but it could record information. That was useful for handling
behaviors that did a timing function.
[snip]
Subsumption is basically an OR operation, just like a logic gate. If
one behavior fires the overall? gate becomes true and returns to a
higher level in the tree. There is also an AND operation where all
the behaviors must fire before returning true. If one fails to fire
a false is returned. The other main operation is NOT which is an
inverter of the output of a list.
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">If you're not familiar with subsumption,? the above is not an
accurate description.? At all.?? ;)
For those who might be interested, the Joseph Jones books "Mobile
Robots" and "Behavior Based Robotics" provide sort of the canonical
definitions for subsumption and how it works.? If you don't want to
read that much then I think I did a pretty good job of describing it
in the DPRG talk from last June, for which there is a YouTube video
on the club web page, (miss-labeled "May 12" rather than "June 12").
cheers!
David
_______________________________________________
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</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">
_______________________________________________
DPRGlist mailing list
<a class="moz-txt-link-abbreviated" href="mailto:DPRGlist@lists.dprg.org">DPRGlist@lists.dprg.org</a>
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</pre>
</blockquote>
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------------------------------
Message: 11
Date: Fri, 29 Oct 2021 08:52:54 +1300
From: Murray Altheim <a class="moz-txt-link-rfc2396E" href="mailto:murray18@altheim.com"><murray18@altheim.com></a>
To: <a class="moz-txt-link-abbreviated" href="mailto:dprglist@lists.dprg.org">dprglist@lists.dprg.org</a>
Subject: Re: [Dprglist] On Behavior Trees [Was: self driving trucks
and the desert]
Message-ID: <a class="moz-txt-link-rfc2396E" href="mailto:f4dc3f3b-18e9-0610-33af-1a932d41f40c@altheim.com"><f4dc3f3b-18e9-0610-33af-1a932d41f40c@altheim.com></a>
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</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">On 29/10/21 7:36 am, Rud Merriam via DPRGlist wrote:
I replied to David and included this link: [...]
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">
Hi Rud,
I'm doing my own robot OS in python so I'll check out the Python code,
and I've got the link to the Italian/Swedish paper, thanks for that.
My own exploration is inspired by my readings of Brooks, Jones, and what
I've learned from David (who has been a great help), and is a based around
an asynchronous (asyncio) message bus supporting a publish-subscribe model.
There is the ability to enable/disable and suppress/release any of the
Publishers or Subscribers, plus a class of Behaviour that combines both
a Publisher and Subscriber, so the basic foundations of subsumption are
there but not at the level of a single or BT loop, as all of the event-
carrying messages sent around within the system are asynchronous. I
maintain that it's still following the basic idea of a subsumption
architecture but implemented quite differently than others I've seen.
I'm still working through the details of it but so far things are working.
A lot of effort...
I'm curious about the Behaviour Tree idea because it suggests different
patterns or sequences of behaviours for different contexts, which is
something I've been investigating.
Cheers,
Murray
...........................................................................
Murray Altheim <murray18 at altheim dot com> = = ===
<a class="moz-txt-link-freetext" href="http://www.altheim.com/murray/">http://www.altheim.com/murray/</a> === ===
= = ===
In the evening
The rice leaves in the garden
Rustle in the autumn wind
That blows through my reed hut.
-- Minamoto no Tsunenobu
------------------------------
Message: 12
Date: Thu, 28 Oct 2021 15:06:25 -0500
From: Rud Merriam <a class="moz-txt-link-rfc2396E" href="mailto:rudmerriam@gmail.com"><rudmerriam@gmail.com></a>
To: <a class="moz-txt-link-abbreviated" href="mailto:dprglist@lists.dprg.org">dprglist@lists.dprg.org</a>
Subject: Re: [Dprglist] On Behavior Trees [Was: self driving trucks
and the desert]
Message-ID: <a class="moz-txt-link-rfc2396E" href="mailto:065fd9e1-8f6b-e4d2-e406-879b976a8230@gmail.com"><065fd9e1-8f6b-e4d2-e406-879b976a8230@gmail.com></a>
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BTs provide the means of changing the overall behavior from a high
level. In one competition there were 3 main task to be performed. At the
highest level the BT allowed all three to be stated as a simple list of
three items with sub-trees for their specific requirements.
-73 -
*Rud Merriam K5RUD*
/Mystic Lake Software/ <a class="moz-txt-link-rfc2396E" href="http://mysticlakesoftware.com/"><http://mysticlakesoftware.com/></a>
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">On 10/28/21 2:52 PM, Murray Altheim via DPRGlist wrote:
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">On 29/10/21 7:36 am, Rud Merriam via DPRGlist wrote:
I replied to David and included this link: [...]
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">
Hi Rud,
I'm doing my own robot OS in python so I'll check out the Python code,
and I've got the link to the Italian/Swedish paper, thanks for that.
My own exploration is inspired by my readings of Brooks, Jones, and what
I've learned from David (who has been a great help), and is a based
around
an asynchronous (asyncio) message bus supporting a publish-subscribe
model.
There is the ability to enable/disable and suppress/release any of the
Publishers or Subscribers, plus a class of Behaviour that combines both
a Publisher and Subscriber, so the basic foundations of subsumption are
there but not at the level of a single or BT loop, as all of the event-
carrying messages sent around within the system are asynchronous. I
maintain that it's still following the basic idea of a subsumption
architecture but implemented quite differently than others I've seen.
I'm still working through the details of it but so far things are
working.
A lot of effort...
I'm curious about the Behaviour Tree idea because it suggests different
patterns or sequences of behaviours for different contexts, which is
something I've been investigating.
Cheers,
Murray
...........................................................................
Murray Altheim <murray18 at altheim dot com>?????????????????????? =
=? ===
<a class="moz-txt-link-freetext" href="http://www.altheim.com/murray/">http://www.altheim.com/murray/</a> ===? ===
= =? ===
??? In the evening
??? The rice leaves in the garden
??? Rustle in the autumn wind
??? That blows through my reed hut.
?????????? -- Minamoto no Tsunenobu
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