DaDaLee's profile - activity

I've read over robot_localization documents , REP105 and the ROSCon 2015 presenation but still got confused by these frames. Here's my question:

1.About base_link frame: It's said to be attached to the robot.Does it mean it always keeps x axis pointing forward like ENU coordinates and move with the robot?

2.About odom frame: Why is it continuous ? The input data of imu and odometry are offered in certain frequency,isn't it discrete data? And why does it drift over time?Is it because the position is calculated by twiste data rather than given by GPS?

3.About map frame: As can be seen from the rviz, the map frame seems to go with odom frame.What's the diffrence between them?

Last but not least,my GPS,IMU,Odometry all pub discrete data but vary in frequency. What I learn from the robot_localization package is that IMU and Odometry are continuous.Which is right? I do appreciate it if someone can enlighten it to me.

Hi Tom/all: I'm wondering what the mathmatics formula in ekf.cpp file is. It's the core of EKF. But I got confused when looking through those code. Can somebody enlighten it to me? Thank you so much!

I'm using a package named robot_localizaton offered by ROS downloaded from github.Here's the problem: I put a couple lines of code to export position data,it goes like this:

"cout<<"robot's y position: "<<filteredposition.pose.pose.position.y&lt;<endl;"&lt; p="">

but I didn't get desired output in the terminal after rosrun robot_localization ekf_localization_node(already get params loaded).I assume the node doesn't operate at all. What confuses me most is that running rostopic echo /odomfiltered leads to data stream output. Any answer would be appreciated,thank you so much.

/rostopic_10245_1493704203398 appears when I run rosnode list. Is it by default? The list of number affixed are random or not?

And it has subscriptions of my node.The relevant info of it presents as follows:

Node [/rostopic_10245_1493704203398]
Publications: 
 * /rosout [rosgraph_msgs/Log]

Subscriptions: 
 * /odometry/filtered [nav_msgs/Odometry]

Services: 
 * /rostopic_10245_1493704203398/set_logger_level
 * /rostopic_10245_1493704203398/get_loggers


contacting node http://idriver-ThinkPad-E450:42951/ ...
Pid: 10245
Connections:
 * topic: /rosout
    * to: /rosout
    * direction: outbound
    * transport: TCPROS
 * topic: /odometry/filtered
    * to: /ekf_navigation_node (http://idriver-ThinkPad-E450:39280/)
    * direction: inbound
    * transport: TCPROS

Can someone enlighten it to me?I do appreciate your help.

Hi Tom/all: As suggested in robot_localization document and REP 103, the imu data is required to be adhere to frame like "x forward, y left, z up", and odom data should adhere to frame like "x east, y north, z up" (which is ENU coordinates). Is that so? The relevant input data should go with the coordinates mentioned above or we need to broadcast transform from imuMsg->frame_id to baselink and odomMsg->frame_id to odom. By the way, what coordinate should GPS data adhere to ? I have no idea whether I'm right. I do appreciate it if someone can enlighten it to me.

I'm using robot_localization offered by ROS downloaded from gihub .It can be compiled and I haven't changed anything of it. When I executed the command: 'roslaunch ekf_template.launch' in a terminal,I got several warnings as follows:

Traceback (most recent call last): File "/home/pantiq/robot/devel/bin/roslaunch", line 6, in exec(fh.read()) File "", line 34, in File "/home/pantiq/robot/devel/lib/python2.7/dist-packages/roslaunch/init.py", line 35, in exec(__fh.read()) File "", line 56, in File "/home/pantiq/robot/src/ros_comm/tools/roslaunch/src/roslaunch/launch.py", line 55, in from roslaunch.nodeprocess import create_master_process, create_node_process File "/home/pantiq/robot/src/ros_comm/tools/roslaunch/src/roslaunch/nodeprocess.py", line 52, in from rosmaster.master_api import NUM_WORKERS File "/home/pantiq/robot/src/ros_comm/tools/rosmaster/src/rosmaster/init.py", line 35, in from .main import rosmaster_main File "/home/pantiq/robot/src/ros_comm/tools/rosmaster/src/rosmaster/main.py", line 43, in import rosmaster.master File "/home/pantiq/robot/src/ros_comm/tools/rosmaster/src/rosmaster/master.py", line 47, in import rosmaster.master_api File "/home/pantiq/robot/src/ros_comm/tools/rosmaster/src/rosmaster/master_api.py", line 72, in from rosmaster.util import xmlrpcapi File "/home/pantiq/robot/src/ros_comm/tools/rosmaster/src/rosmaster/util.py", line 48, in from defusedxml.xmlrpc import monkey_patch ImportError: No module named defusedxml.xmlrpc Then I downloaded a folder named defusedxml from a website,and put it in the robot_localization/src path,still it doesn't work.

What should I do with it?Shall I custimaze it or do something else? I do appreciate it if anyone can help me out.

After rosrun ekf_localization_node and navsat_transform_node, I got warning like this:

I'm using robot_localization package offered by ROS community. I've read over the relevant documents and code. I want to customize it based on the package .Here's my question:

1.If I have one odom and one imu as data source, then only odom0 & imu0 are needed, can I just delete contents about odom1,pose0 and twist0 ?

2.I enable X,Yaw,Vx,Yawrate in odom0_config and Yawrate,Ax in imu0_config. I should set the covariance of these variables mentioned before properly,what about the rest of covariances(including Q and P) whose variables being disabled? Maybe set them to small value (eg.1e-6)?

3.If I want to operate in 2D mode, I need to enable two_d_mode. Should I adjust the transfer function matrix to 2D mode?

4.If I want to adopt the robot_localization. I need to modify the document named ekf_template.yaml, making some change on covariance matrices and deleting some unused contents.Also, I need to modify the transfer function and transfer function Jacobian matrices or say,just simplify it. Is that so?

5.Is the coordinates used in transfer function right-handed coordinate system with X pointing forward ?

I do appreciate it if someone can enlighten it to me.

What's the mathmatics formula in robot_localization Hi Tom/all: I'm wondering what the mathmatics formula in ekf.c