Re: [Paparazzi-devel] fly in the loop

[Steven Wawryk]

Hi Pascal,

I guess I like to think of the entire <while until="..."/> statement as a
"stage".  But if others like to think of each iteration as a stage, then I'd be
happy with anything that allows a readable construct.  Either of your
suggestions would make me happy.  Prominent warnings about the use of stage_time
in while elements are probably needed.

Steve


Pascal Brisset wrote:
> Hi,
> 
> we could have a
> 
> <sleep until="condition"/>
> 
> instruction or a new "loop_time" variable. What do you think ?
> 
> --Pascal
> 
> Steven Wawryk wrote:
>> Hi Pascal,
>>
>> It's not a criticism, it's just a usage that I find more intuitive and 
>> readable.
>>
>> I agree that it makes no sense during any fixed-wing flying phase.  The
>> situations I've encountered where I would have liked it are all before launch
>> when it doesn't make sense for a controller to be running.
>>
>> One example was for a delay between control surface position changes during
>> pre-launch testing where I wanted:
>>
>> <while cond="LessThan(stage_time,4)"/>
>>
>> and worked around it with:
>>
>> <attitude roll="0.0" throttle="0.0" vmode="throttle"
>> until="LessThan(4,stage_time)"/>.
>>
>> Another was to speed up GPS settling where I wanted a timed out accuracy 
>> criterion:
>>
>> <while cond="And(LessThan(1000,gps_Pacc),LessThan(stage_time,10))"/>
>>
>> and worked around with:
>>
>> <attitude roll="0.0" throttle="0.0" vmode="throttle"
>> until="Or(LessThan(gps_Pacc,1000),LessThan(10,stage_time))"/>
>>
>> I personally think that the "while" element is more readable.
>>
>> The use of empty "while" element works when used with block_time
>> (NavBlockTime()) or any other variable for that matter and there are lots of
>> examples of this in the flight_plan directory, so it can entice the naive 
>> user
>> like me to use stage_time and wonder why it hangs and never gets past that 
>> stage
>> (though the flight plan display doesn't actually show that it is hung up on 
>> that
>> stage, so it takes a bit of investigating).
>>
>> Of course, it's not a show-stopper because there is a work around.
>>
>> Steve
>>
>>
>> Pascal Brisset wrote:
>>   
>>> Hi,
>>>
>>> there is a single "stage_time" variable which is reset at the beginning
>>> of every stage. Here, there is a hidden empty stage inside the while
>>> loop where the variable is reset. It is probably not enough documented.
>>>
>>> However, what do you expect of doing nothing during 2s ? Except during
>>> an initialisation phase (or a perch phase with an heli), on the ground,
>>> you probably want to continue to fly ...
>>>
>>> So the <attitude/> instruction is a good answer
>>>
>>> --Pascal
>>>
>>> Steven Wawryk wrote:
>>>     
>>>> I have noticed previously that stage_time is reset to zero every iteration 
>>>> of a
>>>> while loop.  It works fine with "until=" attributes in other elements or
>>>> "stages", but not while elements.  I think this is a bug.
>>>>
>>>> Try another element that has an "until" attribute, like <attitude ... 
>>>> until="2
>>>> <= stage_time">
>>>>
>>>>
>>>> 郭 flying pig wrote:
>>>>   
>>>>       
>>>>> Hi all
>>>>>
>>>>>   I have try to create a loop flight in the basic.xml (from HOME --> 
>>>>> STDBY --->CLIMB ....repeat),  i use the following 
>>>>>
>>>>>
>>>>>
>>>>> <block name="loop" strip_button="lop">
>>>>>         <while cond="TRUE">
>>>>>         <go wp="HOME"/>
>>>>>         <go wp="STDBY"/> 
>>>>>         <go wp="CLIMB"/>
>>>>>         <while cond="2 > stage_time"/>
>>>>>         </while>
>>>>> </block>
>>>>>
>>>>>
>>>>>   The problem i have is that once i call the block, it will fly from HOME 
>>>>> --->STDBY ---->CLIMB , but after that it will not do anything until i 
>>>>> call the block again, does anyone one have any idea how to do it right? 
>>>>>
>>>>>   I have enclosed my basic2.xml for the flight plan.
>>>>>
>>>>>
>>>>> Thanks
>>>>>
>>>>>                                                                           
>>>>>           Chen
>>>>>
>>>>> _________________________________________________________________
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>>>>>
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