Basically, I have never used Gazebo 0.7
I only know a little about the code of 0.8-pre1 and above.
I will try to upload a helicopter set today (thanks to Domenico) for 0.8
On Thu, Mar 13, 2008 at 2:26 PM, <[EMAIL PROTECTED]> wrote:
> Just to confirm the update child refers to the update function? I
> specify the update rate using the <UpdateRate> tag in the world file.
> I am sorry I forgot to mention I am using gazebo 0.7 and not 0.8. in
> my sleep deprived state. I was forced to use 0.7 as I was in a hurry
> and didn't have the time to export the Avatar Heli model to 0.8.
>
> I could try the simulation in 0.8 as well, if the need arises. I guess
> the client and controller file would remain same except the place
> where the Helicopter is built in the controller file. I will just make
> a box using the xml file and try it on 0.8.
>
> Thats the reason to have an update param in the controllers, to have
> some independence from the global updaterate. Is this update param the
> second argument to the Get Double function?
> I tried changing the the updateTime in the world file to 10 or 100 but
> to no avail.
>
> The problem in my case is that I am using a very small delta time to
> solve my diff equations. Therefore, the solution to the equations lags
> the simulation. Therefore, I resorted to plotting the Helicopter pose
> at each time instant, which doesn't work either. The code I used for
> plotting is given in the last mail.
>
> How can I make the simulation sleep till new information from the
> client side is received?
> Maybe in my case a function to start and stop the physics simulation
> is needed until and unless I can get by plotting the Helicopter
> positions.
>
Where will I find method Simulator::MainLoop.
>
It is not present in 0.7, I think the main loop should be in the main.c
>
> Thanks a lot.
>
> On 3/13/08, Jordi Polo <[EMAIL PROTECTED]> wrote:
> > The updateRate is read in the controller, the controller will only call
> the
> > UpdateChild method of your specific controller once each update time.
> Are
> > you sure about the bug of not reading the update rate? Where are you
> > specifying the update rate in the XML?
> >
> > The UpdateChild method receive the update time but doesnt use it.
> >
> > About synchronizing visuals and anything else, you can see the method
> > Simulator::MainLoop and you will see that Gazebo just update everything
> as
> > fast as possible. If physics and rendering are slower it will update
> slower.
> > Thats the reason to have an update param in the controllers, to have
> some
> > independence from the global updaterate.
> >
> > I dont know if a global updateRate is a good idea it can be as easy as
> sleep
> > till next frame.
> >
> > Do you think a method to stop physics and restart physics can be useful
> to
> > you?
> >
> >
> >
> > On Thu, Mar 13, 2008 at 4:57 AM, Vaibhav Ghadiok <
> [EMAIL PROTECTED]>
> > wrote:
> >
> > > hi
> > >
> > > I have a set of differential equations for the dynamics of a UAV. They
> > > give me the rpy, xyz and their respective rates. I am solving these in
> my
> > > client program and then pass on the velocities (xyz & rpy rates) using
> > > playerc_position3d_set_velocity. (I put these equations in the client
> > > program and not the controller, because otherwise the UAV model will
> start
> > > falling down as soon as the world file is executed, if it has been
> > initiated
> > > with 0 velocity. It will have to be initiated with trim conditions. I
> need
> > > stationary UAV's at the beginning.)
> > >
> > > As the parameters of my model are different from that of the Avatar
> Heli,
> > > this doesn't work too well. Also the update times of the method used
> to
> > > solved the differential equations in the client program (eg. delta
> time
> > for
> > > the euler method) and the update time of the visualization is not
> > > synchronized) Any suggestions?
> > >
> > > Anyway, I finally changed the update function of the controller
> program as
> > > given below. Basically I just want to pass the position of the
> Helicopter
> > > from the clent program at each time instant and plot the positions of
> the
> > > Helicopter. This isn't quite working though. Even when I initiate the
> > > position of my model at 100, 100, 0 (xyz) using the world file it is
> shown
> > > at 0,0,0.
> > >
> > > Also, what is the double step passed to the update function, it is
> never
> > > used.
> > >
> > > void Helicopter::Update(double step)
> > > {
> > > GzPose pose;
> > > if (this->world->GetSimTime() - this->updateTime >
> this->updatePeriod)
> > > {
> > > this->updateTime = this->world->GetSimTime();
> > >
> > > this->PositionGetCmd();
> > >
> > > // I am passing the positions using playerc_position3d_set_velocity
> > > xxx = this->position->data->cmd_vel_pos[0];
> > > yyy = this->position->data->cmd_vel_pos[1];
> > > zzz = this->position->data->cmd_vel_pos[2];
> > > roll = this->position->data->cmd_vel_rot[0];
> > > pitch = this->position->data->cmd_vel_rot[1];
> > > yaw = this->position->data->cmd_vel_rot[2];
> > >
> > > GzVector pos0 = GzVectorSet(xxx, -yyy, zzz);
> > > GzQuatern rot0 = GzQuaternFromEuler(roll, -pitch, -yaw);
> > > GzPose pose;
> > > this->body->SetPosition(pos0);
> > > this->body->SetRotation(rot0);
> > > pose.pos = pos0;
> > > pose.rot = rot0;
> > > // Update the interface
> > > this->PositionPutData(&pose);
> > > }
> > >
> > > return;
> > > }
> > >
> > > Another issue is the update rate (the rate at which the update
> function is
> > > called). Changing it in the world file doesn't make a difference but
> when
> > I
> > > change the update rate by changing the second parameter of GetDouble
> > > function I get lower update times. (Relevant code is given below). I
> need
> > to
> > > lower the update time to get smooth plotting of the Helicopter. If it
> is
> > > plotted at 10 times per second, it will be very jerky.
> > >
> > > this->updatePeriod = 1.0 / (node->GetDouble("updateRate", 10) + 1e-6);
> > > this->updateTime = -updatePeriod;
> > >
> > > Thanks in advance.
> > >
> > > Vaibhav
> > >
> > > --
> > > http://guidance.aero.iisc.ernet.in/vaibhav
> > >
> -------------------------------------------------------------------------
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> > >
> > >
> >
> >
> > --
> > Jordi Polo Carres
> > NLP laboratory - NAIST
> > http://www.bahasara.org
> >
>
>
> --
> Mobile Robotics Laboratory
> Guidance, Control and Decision Systems Laboratory
> Aerospace Department
> Indian Institute of Science, Bangalore
>
> http://guidance.aero.iisc.ernet.in/vaibhav
>
--
Jordi Polo Carres
NLP laboratory - NAIST
http://www.bahasara.org
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