sebsch's profile - activity

The following worked for me with qtcreator 3.0.1 on Ubuntu 14.04 (Trusty) with ROS Indigo

Within your src directory, check which file the symlink CMakeLists.txt points to. In my case (Indigo on Trusty), ls -l tells me:

CMakeLists.txt -> /opt/ros/indigo/share/catkin/cmake/toplevel.cmake

Then replace the symlink with a copy of toplevel.cmake:

rm CMakeLists.txt

cp /opt/ros/indigo/share/catkin/cmake/toplevel.cmake CMakeLists.txt

It looks like you might have added jochen sprickerhof's ppa for PCL, which interferes with hydro.

Removing it with the following command solved the problem for me:

sudo ppa-purge ppa:v-launchpad-jochen-sprickerhof-de/pcl

AFAIK the navigation stack in its current state does not work for a carlike robot. The last time I checked, base_local_planner required the robot to be able to turn in place.

Would I have to implement an alternative to base_local_planner or is there an easier way to make base_local_planner work for carlike robots?

That's correct, base local planner can only handle holonomic/differential drive robots and assumes roughly circular shape.

The global path currently can be constructed using the sbpl lattice planner. This planner follows the BaseGlobalPlanner interface, so it will output a valid global path for use by a local planner. Be sure to check out the list of motion primitives (section 3.1.2). We have had luck using the unicycle.m and it has generated k-turns for our diff drive robot when we forgot to tell it to turn in place. Base Local Planner took one look at those and ignored them. :)

This code will provide a (probably!) valid plan for Ackermann drive vehicles. Once you have this working, you will need to write your own local planner to take in the desired x, desired y, and desired heading output by the lattice planner. This is more complicated, but you could easily take a systems approach and calculate x_err, y_err, and yaw_err and then perform some sort of PID approach to the steering.

That's the takes effort to implement approach, so I'm hoping someone else knows of a package to do precise path following as the potential based approach in the base local planner will fail for avoiding obstacles in Ackermann (it wants to descend the gradient each step no matter what, not always possible for a car). If you do write your own base planner, be sure to follow the interface given.

There is a topic "/tf" where tf information is published on as type tf/tfMessage (which contains the actual transforms). Why not subscribe to that? All tf information will be published on that topic however, so you may have to inspect the messages and only trigger your control on the right transforms.

Up to now, I have used tf as described in the tutorial Writing a tf listener: Whenever I need some positions transformed, I just use lookupTransform.

I am considering using tf data to control a robot and would like the robot to react whenever new tf information becomes available, i.e. subscribe to tf data. Is this possible at all?

The only possible way I see at the moment is having a polling loop as shown in the tutorial. This is bad because it introduces latency (especially if I choose a low rate) and wastes cpu time (especially if I choose a high rate).

Is there really no different option?

Similar to in earlier versions, you can make packages meant for natty narwhal work on oneiric ocelot.

I successfully tried the following with electric, but it should also work with diamondback.

• Add the latest package source (in this case: Natty) to your sources.list (electric, diamondback).

• Install freeglut3-dev, which replaced libglut3-dev in oneiric:

  sudo apt-get install freeglut3-dev

• Install equivs, which will allow you to create pseudo-packages:

  sudo apt-get install equivs

• Create a file libglut3-dev.conf for the pseudo package linking libglut3-dev and freeglut3-dev:

  Section: misc

  Priority: optional

  Standards-Version: 3.6.2

  Package: libglut3-dev

  Depends: freeglut3-dev

  Description: temporary package to satisfy dependencies of Ubuntu 11.04 packages on 11.10

• Convert it to an actual package and install it:

  equivs-build libglut3-dev.conf

  sudo dpkg -i libglut3-dev_1.0_all.deb

• You should now be able to install the full ros desktop using one of the following

  sudo apt-get install ros-electric-desktop-full

  sudo apt-get install ros-diamondback-desktop-full

• Now you still cannot use opencv and some other packages as they are linked against old versions of some libraries. Download and install the following packages taken from natty to get these to work anyway. Choose the correct link according to your architecture:

  libavcodec52 libavformat52 libavutil50 libavutil-extra-50 libswscale0 libtinyxml2.5.3 libvtk5.4

  Afterwards, install all of these packages using

  sudo dpkg -i *.deb

  wherever you downloaded them to.