[ros-users] Novint Falcon, HAPI and ROS

[cuenta altas]

Hi Vijay and Josh,

2010/3/25 Vijay Pradeep <vpradeep at willowgarage.com>

What loopRate have you requested?  Could you possibly check and see how fast
> each loop is running?  Is it possible that the haptic processing thread is
> being starved (ie. is your cpu swamped)?
>

 I've tried with rates as low as 1Hz and nothing changes, so I don't think
that's the case.

I also noticed that in the non-ROS version, your while loop is looping as
> fast as possible, whereas in the ROS version, it is slowed down by a
> loopRate object.
>
> I'd be curious to see what happens if you remove the *
> positionPub.publish(positionMsg)* and *ros:spinOnce()*, and maybe also the
> *loopRate.sleep()*.  Pretty much, I'm suggesting that you make your
> ROS-version while loop look exactly the non-ROS while loop.  This might help
> pin down whether or not the background ROS thread is messing things up.


Already tried this too, and it doesn't change anything either.

2010/3/25 Josh Faust <jfaust at willowgarage.com>


> A quick look at the HAPI API shows that enableDevice() can return an error
> code -- what's it returning?
>

It's returning 0, which corresponds to SUCCESS.

The one thing I can think of that might cause problems is if HAPI is trying
> to use SIGPIPE, since I believe roscpp disables it entirely.
>

I'm not completely sure how to find out about this. I just grep'd all HAPI
source files for SIGPIPE and there are no results. I'll try to ask on their
forums anyways.


> Also, a side note: geometry_msgs/Vector3 probably fits your data better
> than std_msgs/Float64MultiArray.
>

Right now I'm using this because I want to send these messages to a Orocos
node and Float64MultiArray is already defined as a valid message type.
Thanks for the suggestion anyways, I'll try to look into it later.

As a side note, I'd like to add that a while ago I also tried to create a
Orocos component to manage the haptic, with similar results. Maybe that can
shred a light for someone.

Thanks to both of you for your suggestions, however I think I'll try to find
a workaround to this, because the only way I can think of solving this is
looking deep into HAPI and ROS source code, and this would require much more
time than I have available right now. If you're still interested in finding
what's going wrong I can do all the tests you want, though.

Best,
Miguel.


On Thu, Mar 25, 2010 at 3:38 AM, cuenta altas <miguel.register at gmail.com>wrote:
>
>> 2010/3/24 Brian Gerkey <gerkey at willowgarage.com>
>>
>>> On Wed, Mar 24, 2010 at 9:50 AM, cuenta altas <miguel.register at gmail.com>
>>> wrote:
>>> > I'm trying to use HAPI to create a node that manages a Novint Falcon
>>> haptic
>>> > device.
>>> > The problem is that haptic rendering doesn't work at all when I manage
>>> the
>>> > device from a ROS node, while almost the same code (without all the ROS
>>> > stuff) works fine from a standalone process.
>>> > I know that HAPI internally spawns a separate thread to manage the
>>> device at
>>> > high frequencies (~1 kHz). I also know that the way it does it is
>>> through
>>> > another library (distributed with HAPI) named H3DUtil, which in turn
>>> uses
>>> > pthreads. I suspect there must be some kind of interference between the
>>> > thread that manages the haptic device and ROS, but I'm not comfortable
>>> > enough with any of them (HAPI or ROS) to be able to speculate any
>>> further.
>>> > Has anyone had any experience with this library before and experienced
>>> > similar problems? And if nobody has, does somebody have any suggestion
>>> on
>>> > which way should I go to try to fix this?
>>>
>>> hi Miguel,
>>>
>>> I'm not familiar with that library, but I'd surprised if the threads
>>> were interfering with each other.  It's more likely that when you're
>>> using ROS, you're not calling HAPI's event loop.  Can you post the
>>> code that works and the code that doesn't?
>>>
>>
>> Hi Brian,
>>
>> These are the two files. Both compile and run okay, but with one I can
>> feel the plane restrictions I send to the device and with the other one I
>> can't.
>>
>> I'll keep trying to figure out what's wrong.
>>
>> Best,
>> Miguel.
>>
>>
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