Ask Your Question

Pujie's profile - activity

2020-02-15 00:15:39 -0600 received badge  Popular Question (source)
2020-02-13 19:18:01 -0600 commented question Can't view lidar points in rviz.

It seems that something wrong in my broadcaster. Because when I turn off the broadcaster, and then I set Fixed frame as

2020-02-13 18:16:41 -0600 asked a question Can't view lidar points in rviz.

Can't view lidar points in rviz. Hi, I try to view the lidar points in Rviz, and I tf broadcast topic /scan to /world.

2019-11-26 15:16:49 -0600 received badge  Notable Question (source)
2019-10-17 16:06:25 -0600 marked best answer Why it shows unknown substitution command?

I try to use a launch file. But it shows unknown substitution command. I don't know why.

<launch>
    <param name="/use_sim_time" value="true"/>
    <arg name="map_file" default="$(find turtlebot3_navigation)/maps/map.yaml"/>
    <arg name="open_rviz" default="true"/>


    <!-- Run the map server -->
    <node name="map_server" pkg="map_server" type="map_server" args="$(turtlbot3_navigation)/map/map.yaml" >
        <param name="frame_id" value="/map" />
    </node>

    <group ns="robot1">
        <param name="tf_prefix" value="robot1_tf" />
        <param name="amcl/initial_pose_x" value="1" />
        <param name="amcl/initial_pose_y" value="1" />
        <include file="$(find turtlebot3_navigation)/launch/new_move_base.launch" />
    </group>

    <group ns="robot2">
        <param name="tf_prefix" value="robot2_tf" />
        <param name="amcl/initial_pose_x" value="-1" />
        <param name="amcl/initial_pose_y" value="1" />
        <include file="$(find turtlebot3_navigation)/launch/new_move_base.launch" />
    </group>

    <!--node pkg="rviz" type="rviz" name="rviz" args="-d $(find your_pkg)/config/multi.vcg"
          output="screen" -->
    <node pkg="rviz" type="rviz" name="rviz" required="true"
          args="-d $(find turtlebot3_navigation)/rviz/turtlebot3_navigation.rviz"/>
</launch>

The terminal shows:

roslaunch turtlebot3_navigation multiple_navigation.launch 
... logging to /home/ise-admin/.ros/log/406b2672-a176-11e8-841a-509a4c311940/roslaunch-ise-linux-1-6017.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

Unknown substitution command [turtlbot3_navigation]. Valid commands are ['find', 'env', 'optenv', 'anon', 'arg']
The traceback for the exception was written to the log file

I can't find the log file in /.ros/log. Do you know why it shows Unknown substitution command?

Thank you!

2019-09-13 20:04:21 -0600 received badge  Student (source)
2019-09-13 19:44:08 -0600 marked best answer How to read ros log file?

Recently, I write a .launch file. But when I roslaunch it, I get the info as is shown below.

roslaunch turtlebot3_navigation multiple_navigation.launch 
... logging to /home/ise-admin/.ros/log/e4e33fd6-a16d-11e8-841a-509a4c311940/roslaunch-ise-linux-1-5449.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

Invalid roslaunch XML syntax: not well-formed (invalid token): line 29, column 83
The traceback for the exception was written to the log file

In order to find out where are the errors, I hope to open the log file.

cd `roslaunch-logs`
ls
first_tb3-amcl-4-stdout.log         roslaunch-ise-linux-1-3015.log
map_server-2-stdout.log             roslaunch-ise-linux-1-32614.log
master.log                          roslaunch-ise-linux-1-32683.log
robot1-spawn_minibot_model-2.log    roslaunch-ise-linux-1-32749.log
robot1-spawn_minibot_model-3.log    roslaunch-ise-linux-1-3598.log
robot2-spawn_minibot_model-4.log    roslaunch-ise-linux-1-415.log
robot2-spawn_minibot_model-5.log    roslaunch-ise-linux-1-4348.log
robot_state_publisher-1-stdout.log  roslaunch-ise-linux-1-791.log
roslaunch-ise-linux-1-23504.log     rosout-1-stdout.log
roslaunch-ise-linux-1-23544.log     rosout.log
roslaunch-ise-linux-1-23565.log     rviz-9-stdout.log
roslaunch-ise-linux-1-23628.log     second_tb3-amcl-6-stdout.log
roslaunch-ise-linux-1-24416.log     tb3_0-spawn_urdf-4.log
roslaunch-ise-linux-1-24423.log     tb3_0-spawn_urdf-4-stdout.log
roslaunch-ise-linux-1-25479.log     tb3_1-spawn_urdf-6.log
roslaunch-ise-linux-1-25593.log     tb3_1-spawn_urdf-6-stdout.log
roslaunch-ise-linux-1-25811.log     tb3_2-spawn_urdf-8.log
roslaunch-ise-linux-1-26965.log     tb3_2-spawn_urdf-8-stdout.log
roslaunch-ise-linux-1-27793.log     third_tb3-amcl-8-stdout.log

It seems that the log file is temporary, right?

2019-07-03 01:52:01 -0600 received badge  Famous Question (source)
2019-06-26 04:25:57 -0600 received badge  Popular Question (source)
2019-06-08 02:00:49 -0600 asked a question How to change velocity limit in Gazebo simulation

How to change velocity limit in Gazebo simulation Hi there. I was thinking to track an obstacle in fast moving condition

2019-04-04 07:46:27 -0600 received badge  Famous Question (source)
2019-03-22 04:47:27 -0600 received badge  Famous Question (source)
2019-02-21 18:33:11 -0600 received badge  Famous Question (source)
2019-02-21 18:33:11 -0600 received badge  Notable Question (source)
2019-02-17 21:44:03 -0600 received badge  Notable Question (source)
2019-02-17 18:58:43 -0600 commented answer How to read msg from /odom at time series n and (n-1)

Thank you! They said that I can check something like time in msg.header.stamp to get the msg time

2019-02-17 18:56:44 -0600 received badge  Famous Question (source)
2019-02-17 18:36:21 -0600 received badge  Notable Question (source)
2019-02-16 19:28:22 -0600 commented answer How to read msg from /odom at time series n and (n-1)

Learn a new word "Instantiate", thank you!

2019-02-16 19:26:50 -0600 commented answer How to read msg from /odom at time series n and (n-1)

Thank you very much!

2019-02-16 19:26:13 -0600 marked best answer How to read msg from /odom at time series n and (n-1)

Hi there, I hope to compare the message from the consecutive time series n and (n-1) from /odom in python. I am confused about how to store the msg at time n-1 and time n at the same time, especially for the time sequence t=1.

def listener():
    rospy.init_node('listener', anonymous=True)
    rospy.Subscriber("/odom", Odometry, simple_callback)
    rospy.spin()
def simple_callback():

if __name__== '__main__':
    listener()

The problem which confused me is that: I was thinking to use some variables to store the msg at sequence n-1 and n like : current_odom=[ ] and last_odom=[ ]. However, I don't how to store the msg at time t=1, because listener() and simple_callback are in loop, I don't know when to pass the data in current_odom=[ ] and last_odom=[ ]. Could you please give me any hints?

Thank you.

2019-02-16 18:45:09 -0600 received badge  Popular Question (source)
2019-02-16 17:26:12 -0600 commented answer How to read msg from /odom at time series n and (n-1)

Does last_odom = Odometry() mean generate an "object of Odometry" ?

2019-02-16 10:10:32 -0600 edited question How to read msg from /odom at time series n and (n-1)

How to read msg from /odom at time series n and (n-1) Hi there, I hope to compare the message from the consecutive time

2019-02-16 10:10:01 -0600 asked a question How to read msg from /odom at time series n and (n-1)

How to read msg from /odom at time series n and (n-1) Hi there, I hope to compare the message from the consecutive time

2019-02-13 21:42:59 -0600 commented answer What is the ros::spin rate?

Got it ! Thank you!

2019-02-13 11:22:21 -0600 commented answer What is the ros::spin rate?

@gvdhoorn. Thank you. You mean there is some kind of time delay if the message has too much data? Do you think the messa

2019-02-13 11:11:49 -0600 received badge  Popular Question (source)
2019-02-13 09:50:14 -0600 commented answer What is the ros::spin rate?

Thank you very much! This helps a lot!

2019-02-13 09:49:32 -0600 commented answer What is the ros::spin rate?

Thank you for help!

2019-02-13 09:45:08 -0600 marked best answer What is the ros::spin rate?

Hi, I need to run a moving robot in simulation and I need to know the translation and rotation of this robot. I was thinking to use the translation = linear.velocity *dt, and rotation = linear.velocity.z * dt. But I don't know what dt is. I have a subscriber with ros::spin() to subscriber the /cmd_vel topic.

  1. How can I get the dt?

  2. Does the dt strictly equal to the (1/publisher node's rate) ?

Thank you!

2019-02-13 04:36:18 -0600 received badge  Notable Question (source)
2019-02-13 03:25:38 -0600 received badge  Popular Question (source)
2019-02-13 01:05:21 -0600 commented question What is the ros::spin rate?

I can also use the data in /odom. But I still want to know the dt. Thank you!

2019-02-13 01:03:45 -0600 asked a question What is the ros::spin rate?

What is the ros::spin rate? Hi, I need to run a moving robot in simulation and I need to know the translation and rotati