Category Archives: Robotics

ROS – [rosout-1] process has died, exit code -11

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Some days ago I started roscore and got faced with an error message like that:

process[rosout-1]: started with pid [16089]
[rosout-1] process has died [pid 16089, exit code -11, cmd /opt/ros/indigo/lib/rosout/rosout __name:=rosout __log:=/home/rosuser/.ros/log/9b3b3980-0b60-11e4-80f9-0015afdb2ab9/rosout-1.log].
log file: /home/rosuser/.ros/log/9b3b3980-0b60-11e4-80f9-0015afdb2ab9/rosout-1*.log

Okay, so roscore seemed to have crashed and created a log file according to the given path. But the logfile was empty *please imagine dramatic sound effects here*. But what do you do, if a programm (rosout?) crashes without log file and an error message like the above?

You insert your well done system wide backups like snapshots from zfs,btrfs, virtual machines, lvm or anything. If you forgot to do so… *fail sound here* you might need to manually check what changed since the last time it worked.

And so I did. For several days.

I soon figured out, that this error applied to all rosccp related ROS-programms – but left all rospy parts alive, which finally put my on track that there has been an kernel update of my ubuntu 14.04, which I unfortunately installed in a moment of weak decisions.
So reverting that would have been been an option, further my lib-boost version seemed to have changed – since ROS is very sensible to that, this might have been the problem. Therefore I tried everything by manually reverting updates, reinstalling packages, recompile everything from source, searching system logs and soon really considered to reset my system by installing good old 13.04 with ROS hydro…

But wait! Sometimes you strike lucky and time solves all issues. Today I’ve just upgraded my ROS from their repos and tadaaa – everything works again.

But why do I write this into an post? Because its easy to avoid situations like that and I want to share my hard learned lessons with you the easy way:

  1. Get your ROS version straight – Do you really need the latest ROS on the latest kernel?
    The answer for your system is probably no. I am currently running stable ROS Hydro and ‘unstable’ ROS Indigo on Ubuntu 14.04 on latest kernel. It works – but it would have been way easier to stick on Hydro all the way.
  2. avoid apt-get dist-upgrade on critical ROS machines
  3. use backups and / or virtual machines
  4. rospy didn’t cause any problems so far – in case performance isn’t the most important thing, think about using python
  5. avoid to put all your catkin_ws code into one git repository  if its running on multiple architectures (x86,x64, arm6,arm7) – alone the openni2_driver took nearly all my sanity during learning that lesson….

That is enough for today, but after this list, I really think about tracking all hard learned lessons in more public and better organised location – ROS best practices? We’ll see.

 

 

aMoSeRo – leaving the virtual cookie box

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It is only consequent to leave the virtual cookie box too:

aMoSeRo – leaving the cookie box

Finding a low cost case isn’t as easy as expected – even with some common dimensions around 200mm*200mm*50mm the only inexpensive thing I found, was an star wars cookie box made out of thin plate.

So to change that I went to a DIY-Store today (or Baumarkt in german) and bought a 2 meters aluminium mopboard, some metal glue, acrylic glass and went to the basement:

But after cleaning the gluey mess off the table with spiritus, taking a well deserved shower and waiting 24 hours for the glue to get its full power the result is something able to be shown:

It’s a bit bigger than before but provides the basic functions in only 40 mm height. So we’ve got a real mobile plattform (base_footprint) for all upcoming modules (i.g. mesh networks, robot arms, flying drones or sensors like Geiger-Müller counters).

We’ve reached half time! Lets see whats still possible 🙂

Reset Arduino Micro via python serial

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Sometimes resetting a device isn’t as easy as expected. After some research i figured out, that opening a serial connection with a special baud rate would to the job for our Arduino Micro (and similiar like Leonardo):

#!/usr/bin/env python


import serial
port='/dev/ttyACM0' #adjust this in case your device differs
ser = serial.Serial() #open serial connection
ser.port=port #setting the port accordingly

#in case your usual baudrate isn't 9600 reset will not work, therefore we will open a resetable connection
#thanks to mattvenn.net for suggesting to add this step!
ser.baudrate=9600
ser.open(); ser.close()

ser.baudrate=1200 # set the reset baudrate
ser.open(); ser.close()
#don't forget to sleep some reset time

Run the script as root. It might need required to change your port according to your serial controller status.

LeapMotion and ROS

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Today I’ve got the chance to get my hands on a Leap Motion. As it uses depth information to track hands on a short range from the device and as there is a ros driver package existing for it, I hoped to get a 3D PointCloud. It costs about 80€ and could have been a cheap replacement for the [amazon &title=Xtion&text=Asus Xtion].

Unfortunately its not possible (yet?) – here is a very nice post why.

But it is fun anyways to get both hands tracked:

Youtube Video

The ros driver interfaces ros with only one hand – but we could do something like shown below to control the amosero:

Youtube Video

Later it would be a nice way to control a robot arm – but for now we leave that nice little device as there is a lot of other stuff to be done.

aMoSeRo – first robot_pose_ekf and gmapping

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This surely doesn’t look amazing from a external look – but this has been a day of hard work and was very important.

The robot_pose_ekf package is working! It is neither the setup I am going to use nor is it very stable – but it proves some points.

First I needed to write my own IMU driver for ros – 9 degrees of freedom (DOF) for 30€ and a bag of problems. This is a lot cheaper (around 100€) than the often used Razor IMU of sparkfun with existing ROS code, and exactly 3DOF better than the WiiMote (with Motion+ and also about 60-70€) I have been experimenting with. There is still a lot of work left for improving the stability, the calibration of the LSM9DS0 and there has been a lot more to find out about magnetic fields and strange units that needed to be converted in other ones than I would have ever expected – but so far the /imu_data topic serves some not totally wrong data – therefore normalisation minimizes  the issues with the 3-5 scales per axis I had to deal with.

Next I needed to increase my bad odometry sources – if not by quality at least with quantity – and added a GPS sensor as /vo topic.  The CubieTruck is a abstruse while handling some easy things like using one of the possible 8 UART connections…  for today I’ve not managed to get it running with UART but a external serial usb controller. Another area that needs heavy improvement…

Finally I had to deal with the REP105 issue that I have been describing in a previous post. The gmapping algorithm needed to get adjusted parameters, coming along with some serious confusion generated by inconsistent syncing over my 4 working devices (rosBrain with roscore and slamming, rosDev – my development machine, the aMoSeRo and the seafile backup server)…

…but after that all parts worked together for the first time, including a simulated aMoSeRo moving on screen while beeing hold in different angles in the real world.

Everything is still far from done – but right on the way – and we’ve already found out how wide the road is 🙂

Willow Garage, the PR2 and REP105

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It is the second time I need to adjust my URDF Model for the sake of NOT following the REP (ROS Enhancement Proposal). This time it is about the relationship between base_link and a not REP mentioned base_footprint.

As REP105 says the ‘Relationship between Frames’ should be:

map –> odom –> base_link

but the relation chip for the Willow Garage (or now Clearpath Robotics) robot PR2 is

map --> odom_combined --> base_footprint  -->   base_link

which is the exact demand of the robot_pose_ekf package.

So Willow Garage, Y U NO Stick to your own REP105 ?

(See more on Know Your Meme)

I suppose because of backwards compatibility, some code might get broken, but what about using some parameters, maybe with a (even hard coded) default fallback?

So for the aMoSeRo there is a decision to be made. Using base_link or base_footprint? Or both? Which frame is the one near to earth?

If decided to take both as a matter of compatibility to other packages and reordered my TF tree:

 

framesWithParentFootprint

 

Still questionable if the base_footprint should have wheels and tracks attached, but that is more a question of taste because they have no special task.

Screenshot - 04.07.2014_4

 

Now the robot has a light grey base_footprint, and a blue base_link.

aMoSeRo – first Simultaneous Planning Localization and Mapping (SPLAM)

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Far from done, but right on the way – the aMoSeRo did his first 2D planning today.  There are still a lot of adjustments needed for the mapping to work properly, but it’s already impressive to see ROS working.

first SPLAM - first navigation through a map

first SPLAM – first navigation through a map

The node graph still grows and will need some changes when used with multiple robots, but organising goes on 🙂

first SPLAM - it is getting even worse, more topics, more nodes

aMoSeRo – very first mapping view available

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After days with latex and struggling with all sensor data a mobile robot needs, today is the first day of ROS showing me a small map view. It’s anything but stable and I can’t claim understanding everything – but because I’ve hadn’t something to report for some time now here a small demonstration:

First Mapping Experience

Screenshot fromMAP

ScreenshotTopics Topics Overview – amosero a distributed system still far from optimal

Because my IMU doesn’t do its work as it should, I’ve used a WiiMote Motion + and run it by a common ros driver and bluetooth.

Yeeeha 🙂