salime's profile - activity

I am working with the navigation of a two wheeled robot, I am looking at the odometry tutorial www.ros.org/wiki/navigation/Tutorials/RobotSetup/Odom, in this part:

//compute odometry in a typical way given the velocities of the robot
double dt = (current_time - last_time).toSec();
double delta_x = (vx * cos(th) - vy * sin(th)) * dt;
double delta_y = (vx * sin(th) + vy * cos(th)) * dt;
double delta_th = vth * dt;

x += delta_x;
y += delta_y;

it says "A real odometry system would, of course, integrate computed velocities instead"

so, if I have the velocity readings from the wheel encoders, how can I compute this velocities for the odometry model?

www.ros.org/wiki/3d_navigation link demonstrates a package for obstacle avoidance goal driven navigation. But, it is meant for ROS diamondback.Is there a similar version for ROS fuerte with kinect?The robot type is a non-ROS robot.

I am working with a two wheeled robot, and I need the velocity of the wheels in meters per second, I have the encoder count per second, the wheel radius and the wheel distance. How can I translate this to meters per second?

I am trying to implement the navigation with ROS and a two-wheeled robot with Kinect, I have access to the readings of the velocity and pose of the wheel encoders , so I need an odometry motion model . So is there some equation already done for the odometry in ROS that I can use for this purpose? or any person have experience with this topic?

When I run rosrun tf view_frames... I get this: Listening to /tf for 5.000000 seconds Done Listening dot - graphviz version 2.26.3 (20100126.1600) Detected dot version 2.26.3 frames.pdf generated and when I run rostopic echo /map.... I get nothing.... the terminal is empty

Yes, in the rostopic, is this list /cloud_throttled /goal /initialpose /kinect_laser/parameter_descriptions /kinect_laser/parameter_updates /map /map_metadata /openni_manager/bond /rosout /rosout_agg /scan /slam_gmapping/entropy /tf .... so the /map topic is there, but in rviz I can not see that topic

I have that file, I am completely sure, and the code is readable because it was in the tutorial, so I don't know what else could it be

did u solve this??? that thing is happening to me....

I am trying to complete the 2D-Navigation with Kinect and a two-wheel robot, when I following this tutorial to build the map http://www.ros.org/wiki/slam_gmapping/Tutorials/MappingFromLoggedData#record.

What I do is the following: 1) I run the pointcloud_to_laserscan: roslaunch pointcloud_to_laserscan kinect_laser.launch which it works, because I ` have proved it before. 2)rosrun rviz rviz 3) rosrun gmapping slam_gmapping scan:=scan (scan is the base_scan topic) 4) rosbag play --clock example.bag, I wait for this to finish and finally rosrun map_server map_saver.

But it says waiting for the map every time.

I use rosrun gmapping slam_gmapping scan:=scan, (being scan my base_scan topic), and

I installed the ros-fuerte-perception-pcl and ros-fuerte-pcl which are the ones most likely similar in name to point cloud, but I keep getting the same result....

thanks for the reply, could u tell me how can I install it?

I am working with slam_gmapping, and When I launch the pointcloud to laser scan with this file, I do the following steps:

<launch>
  <!-- kinect nodes -->
  <include file="$(find openni_camera)/launch/openni_node.launch"/>

  <!-- openni_manager -->
  <node pkg="nodelet" type="nodelet" name="openni_manager" output="screen" respawn="true" args="manager"/>

  <!-- throttling -->
  <node pkg="nodelet" type="nodelet" name="pointcloud_throttle" args="load pointcloud_to_laserscan/CloudThrottle openni_manager">
    <param name="max_rate" value="2"/>
    <remap from="cloud_in" to="/camera/depth/points"/>
    <remap from="cloud_out" to="cloud_throttled"/>
  </node>

  <!-- fake laser -->
  <node pkg="nodelet" type="nodelet" name="kinect_laser" args="load pointcloud_to_laserscan/CloudToScan openni_manager">
    <param name="output_frame_id" value="/openni_depth_frame"/>
    <remap from="cloud" to="cloud_throttled"/>
  </node>
</launch>

1) After launch the file I open rviz , I set the fixed name to /openni_depth_frame and add a Laser Scan Display.

I followed this tutorial http://answers.ros.org/question/10606/problem-launching-pointcloud-to-laserscan/, and it says that I should see the /scan topic, but I am not able to see it.

How can I solve this?

I have done some tests in the particular case when vl !=0 and vr != 0, incrementing the x, y, ant theta just in these cases, but the results do not look correct either

Thank you for your reply, I did that, the R thing, and now looks like the nan is gone, but the final pose (x,y, theta) keeps getting bigger and bigger when I start moving the robot, even though when I stop moving it.. it keeps getting bigger and bigger in the x, y and theta, and of course these values are not correct for the pose

Thanks for the reply, I am working with ROS Fuerte, Ubuntu 12.04, do I need to use the depthimage_to_laserscan too? Because I saw some posts with that, and I already tried it, but same problem

I want to implement the navigation in a two wheeled robot with the ROS navigation-package using Kinect , How can I calculate the odometry if I have the radius, the wheeled distance, the poses and the velocity of the wheels???