Vassilis's profile - activity

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2013-01-31 04:07:41 -0500	received badge	● Famous Question (source)
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2012-08-20 17:46:57 -0500	received badge	● Famous Question (source)
2012-07-10 16:38:12 -0500	commented question	Problem launching rxbag (global name 'roslib' is not defined) I should also mention that rosbag works fine.
2012-07-10 02:31:43 -0500	asked a question	Problem launching rxbag (global name 'roslib' is not defined) I am running Fuerte and I am getting the following error when launching rxbag with the --record option. It works fine when launching without the --record option (using an existing .bag file). Other rx utilities work fine (rxconsole, rxgraph). Recording using rosbag also works fine. `~/ros_workspace$ rxbag --record --all [INFO] [WallTime: 1341922965.474574] Master found. Connecting... [INFO] [WallTime: 1341922965.791212] Connected to ROS master. [INFO] [WallTime: 1341922965.792201] Recording to 2012-07-10-07-22-45.bag. Error subscribing to /rosout (ignoring): global name 'roslib' is not defined Error subscribing to /rosout_agg (ignoring): global name 'roslib' is not defined` Any ideas? Thanks! Vassilis
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2011-12-27 15:16:41 -0500	answered a question	Turtlebot SLAM map building problems I think I figured this out! My sensor/power board has the ADXRS620 gyro and not the ADXRS613, the big difference is that ADXRS613 has a +/- 150deg/s output and the ADXRS620 has a +/- 300 deg/s output. This is important because for the same angular speed the raw outputs will differ by a factor of two. Also looking at turtlebot_node/src/turtlebot_node/gyro.py the raw signal from the analog input is multiplied by 150 to convert to deg/sec, when I changed it to 300 it worked fine with the values recommended by the calibration. One problem with the higher rate sensor is that the resolution is now halved. As a result I noticed that the drift is very high even with the robot stationary. I added a short averaging filter on the analog input in gyro.py and it helped a lot but I need to experiment with this a bit more. To fix this the gyro type could be defined as a parameter of turtlebot_node. I would be happy to fix this myself if I can get access to commit code.
2011-12-27 12:15:23 -0500	commented question	Turtlebot SLAM map building problems Yes, I am using electric as well. I am going through the code to understand what is going on a bit more.
2011-12-27 08:36:51 -0500	received badge	● Student (source)
2011-12-27 05:20:07 -0500	answered a question	Turtlebot SLAM map building problems It seems like I am getting much better odometry when setting turtlebot_node/gyro_scale_correction to 2.55 instead of 0.876864 that is recommended by the odometry calibration. Not sure if this is normal!
2011-12-27 04:12:27 -0500	commented question	Turtlebot SLAM map building problems I compared the /odom and the /robot_pose_ekf/odom topics and I see a large error in the output of the EKF filter. See the revised question for more details.
2011-12-27 02:27:10 -0500	commented question	Turtlebot SLAM map building problems When I execute "rosparam get /turtlebot_node/gyro_scale_correction" I get the right value.
2011-12-26 13:30:38 -0500	commented question	Turtlebot SLAM map building problems The laser scans are all over the place with the delay on, I do agree there seems to be something wrong with the gyro. I got the Turtlebot sensor/power board last week, so I am not sure what to expect out of the gyro. Maybe somebody with a similar setup can have a look at the IMU plots?
2011-12-26 08:41:31 -0500	commented question	Turtlebot SLAM map building problems Done, please have a look at the revised question for the details. Thanks!
2011-12-26 08:40:03 -0500	received badge	● Editor (source)
2011-12-23 13:20:43 -0500	commented question	Turtlebot SLAM map building problems Yes that was done.
2011-12-23 06:28:53 -0500	asked a question	Turtlebot SLAM map building problems I have some problems building a map with my Turtlebot. I run the calibration (0.85 for the gyro and 0.93 for odom) multiple times and followed the instructions in the tutorials for starting gmapping. The map looks like a set of scans scattered around, also the orientation shown in rviz is not consistent with where the robot is going. To me it seems like there is either a problem with the odometry/gyro or the localization is not working properly. The gyro seems to work (I see the values changing when rotating), do I need to change anything in the config files (except the odo/gyro cal values)? I should also mention that I am using all the turtlebot hardware except the Kinect mounting hardware. I made my own mounting pole but the kinect is located approximately at the same place as with the standard turtlebot. As recommended I did the tests in http://www.ros.org/wiki/navigation/Troubleshooting and it seems like there is something wrong with the odometry, but only while turning, moving straight seems to be fine. The gyro seems to output good values (see plots) and the calibration was done multiple times. Have a look at the following link for a few screenshots and some more details. https://picasaweb.google.com/109216537228630118124/TurtlebotSLAM?authuser=0&authkey=Gv1sRgCPTsg_Wh7fuqZw&feat=directlink I did a 180 degree turn and the /odom orientation (yaw) measured 176.8 degrees, however the /robot_pose_ekf/odom orientation (yaw) measured only 60.4 degrees. So that leads me to believe it is either the gyro or something wrong with the EKF. Also, following is the calibration output (removed a few repeated lines to make the post shorter): [INFO] [WallTime: 1324939496.895343] ... imu drift is -0.621943 degrees per second [INFO] [WallTime: 1324939497.197380] Still waiting for imu [INFO] [WallTime: 1324939497.499277] Still waiting for scan [INFO] [WallTime: 1324939497.801215] Aligning base with wall [INFO] [WallTime: 1324939498.103249] Still waiting for imu [INFO] [WallTime: 1324939498.405232] Still waiting for scan [INFO] [WallTime: 1324939545.778987] Odom error: 2.295941 percent [INFO] [WallTime: 1324939545.780867] Imu error: -32.801991 percent [INFO] [WallTime: 1324939546.090230] Still waiting for imu [INFO] [WallTime: 1324939546.392098] Still waiting for scan [INFO] [WallTime: 1324939546.996119] Aligning base with wall [INFO] [WallTime: 1324939548.270806] Still waiting for imu [INFO] [WallTime: 1324939548.573036] Still waiting for scan [INFO] [WallTime: 1324939560.870167] Odom error: -11.098675 percent [INFO] [WallTime: 1324939560.872639] Imu error: 19.686330 percent [INFO] [WallTime: 1324939561.178241] Still waiting for imu [INFO] [WallTime: 1324939561.480022] Still waiting for scan [INFO] [WallTime: 1324939561.782138] Aligning base with wall [INFO] [WallTime: 1324939565.640311] Still waiting for imu [INFO] [WallTime: 1324939565.942336] Still waiting for scan [INFO] [WallTime: 1324939573.806552] Odom error: 6.987265 percent [INFO] [WallTime: 1324939573.808156] Imu error: 35.610160 percent [INFO] [WallTime: 1324939574.111180] Still waiting for imu [INFO] [WallTime: 1324939574.413042] Still waiting for scan [INFO] [WallTime: 1324939574.715408] Aligning base with wall [INFO] [WallTime: 1324939577.046587] Still ... (more)