[plexil-support] Wait action problem

[Hector C. <hec...@gm...>]

Dear PLEXIL support team,

I have been working for few months in the implementation in the control
layer of an autonomous farming robot. I already implemented an adapter to
connect a Plexil’s  plan with the robot’s hardware, and it worked great.

However, today I’m facing a problem with the Wait action. I have some
actions that should perform periodically, so, based on the documentation
and examples included in the ‘temporal’ folder, I included an action that
is repeated every N seconds. The problem: the action is repeated a
different number of times each time it’s executed. Some times the plan is
completed, and sometimes the plan execution get stuck in a ‘Wait’ execution:

[Node:transition]Transitioning 'Wait__3' from INACTIVE to WAITING at
1456438554.29645 <//1456438554.29645>
[Node:transition]Transitioning 'Wait__3' from WAITING to EXECUTING at
1456438554.29645 <//1456438554.29645>
[Node:clock]Node 'Wait__3' started at 1456438554.29645 <//1456438554.29645>
<— Execution stuck indefinitely


I wrote this basic plan to analyse the problem:



Command pprint (...);

CountIteration:
{

    Boolean continue=true;
    Duration delay = Duration ("PT0.5S");
    Duration tolerance = Duration ("PT0.1S");
    Integer stepsCount=0;

    PeriodicIteration:
    {

        Repeat continue;

        stepsCount=stepsCount+1;

        pprint ("steps Performed: ", stepsCount);
        Sequence{
            Delay:{
                Wait (delay*2),tolerance;
            }
            ConditionallyEndIteration:
            {
                Skip stepsCount<20;
                continue = false;
                pprint ("Ending periodic iteration");
            }

        }

    }
}


In my test environment (Mac OSX / Plexil 4.0.1), only sometimes the plan is
finished. Most of the times, the plan get stuck randomly at different
points (stepsCount=2, stepsCount=9…).

Could you please tell me… am I doing something wrong?… Any advice is really
welcome!


Sincerely yours,


Héctor Cadavid