[Dprglist] First BBR implementation and some questions

[Karim Virani]

I agree, that's the problem. Crossover. Subsumption is not the only
architecture in use. Behavior-based is a broad concept and there are many
arbitration schemes that can be employed. I was trying to carefully
constrain my comments to "my vote", in other words, just my own words, my
own opinion - not trying to represent or denigrate any other point of view
or approach.

Maybe the term "ballistic behavior" belongs exclusively to subsumption
architectures ... and I've mistakenly heard it applied more broadly.  I'm
certainly no expert in subsumption. We use explicit state machines to
control our double-digit DOF robots. So I try not to comment directly on
subsumption.

But It can be confusing. When you google:

"ballistic behavior" robot subsumption

The first thing that comes up is this excerpt from an expert in Dallas:

Ballistic behaviors *cannot be subsumed*: they must run to completion. 2.
Ballistic behaviors are therefore usually assigned highest priority.

Yup, the excerpt stops right there even though you continue in your article:

3. Ballistic behaviors can, however, be aborted.

In fact, abort is really the only reasonable response of a ballistic task
when subsumed. For the SR04 robot, the only task that can subsume a
ballistic bumper behavior, which is the highest priority behavior, is
another ballistic bumper behavior.


So can they be subsumed or not? The language is tricksy.

http://www.geology.smu.edu/dpa-www/robo/subsumption/#:~:text=Ballistic%20behaviors%20cannot%20be%20subsumed,therefore%20usually%20assigned%20highest%20priority
.


On Sun, Oct 31, 2021 at 9:59 PM David P. Anderson via DPRGlist <
dprglist at lists.dprg.org> wrote:

> Well, Karim, now that you mention it...
>
>
> On 10/31/21 5:26 PM, Karim Virani via DPRGlist wrote:
>
> I agree with Doug, you should never have blocking code unless you can
> dedicate a separate thread to it apart from your main loop's thread.
>
> And not to start up the whole debate again, I personally vote that there
> is no use for ballistic behaviors. I treat them as an academic construct.
> There are plenty of uses of objective-oriented and terminating behaviors -
> including those where the objective is to last for a certain amount of
> time. But they should still be interruptible and cancellable by higher
> priority behaviors.
>
> I believe this is a misunderstanding of what ballistic behaviors are in
> the context of subsumption.   For some reason the idea has taken root that
> what makes a behavior ballistic is that it for some reason cannot be
> interrupted.    That is a red herring.   What make a behavior a ballistic
> behavior *in the context of subsumption* is that it continues to execute
> after the signal that triggered it has ceased.
>
> That's all.
>
> I don't understand why such a simple concept has turned out to be so hard
> to communicate.  I consider this a major failing on my part.
>
> cheers!
>
> David
>
>
>
>
> On Sun, Oct 31, 2021 at 5:08 PM Doug Paradis via DPRGlist <
> dprglist at lists.dprg.org> wrote:
>
>> Kumar,
>>     I always pass through the loop. So a 1 sec backwards maneuver would
>> use a loop counter with a disengage value of 50 for a loop time of 20 mS. I
>> am not using a multitasking framework, which opens up other possibilities.
>>
>> Regards
>> Doug P.
>>
>> Sent from my iPhone
>>
>> On Oct 31, 2021, at 4:54 PM, Thalanayar Muthukumar via DPRGlist <
>> dprglist at lists.dprg.org> wrote:
>>
>> https://youtu.be/fuFamNWyXc4
>> <https://secure-web.cisco.com/12R-xW2iM6X1mtZ6lGWZ2cU_V7WhrcVFmrYppQ5_RFJAtuHcumxuYD4t8YW_aGm011_ipOLIKUMPmlNlXLKe0mDeZ5NILZd__YuRF_kKIzyxN8EiJErAuYE-OcebwmywmyJ7SoBG9yB3Oyna9Z9RUY7kwZdTuI-sO3UWkVWgVNhYiwT1_tphO9qAaoFdwYrgHVEynVcBz9QhIC_xYutA9B-8OhKAWWEGvh-8EqTFHmW8H5ZsvYDMLEZNwPag9e3p4bO7y-E8y4CehSNJJRVtWHgi8hUB2z2KYLDpQOUR9fxk/https%3A%2F%2Fyoutu.be%2FfuFamNWyXc4> (~15
>> sec)
>>
>> 20 times per sec
>> - default behavior - go straight forward, green headlights
>> - higher priority behavior - light sensed, turn left, red headlights
>>
>> My understanding of BBR is that there should be no state maintained.
>>
>> Question - If we trigger a ballistic behavior (e.g. go straight backward
>> for one sec), is it ok to not return to the loop every 50 msec?
>>
>> Or is it preferable to maintain state and count 20 times for getting
>> duration of 1 sec?
>>
>> Regards.
>> - Kumar
>>
>>
>>
>> Sent from my iPhone
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