Mayank's profile - activity

Thanks for your comment. I just figured out what was causing the problem.

Hi All,

I'm trying to move the PR2 arms through some predefined points. I have a launch file that first moves them using the default Joint Trajectory Controller on the PR2, and then the ee_cart_imped controller kicks in, and moves the arms through some cartesian coordinates.

My problem is that if initially the Joint Trajectory Controller has run, then the ee_cart_imped controller runs, but if the launch file just runs the ee_cart_controller, I get the following

[ INFO] [1341238106.346256027]: Waiting for the ee_cart_imped_action server

And it does not move the arm at all. Any ideas?

Instead of trying to transform individual points, I am now transforming the entire point cloud to another frame. The code is as follows,

void Convert::convertCallback(const sensor_msgs::PointCloud2 &inputCloud){

    sensor_msgs::PointCloud2 outCloud;
    bool val = mTransformListener->waitForTransform("/base_link", inputCloud.header.frame_id, inputCloud.header.stamp, ros::Duration(10.0));
    pcl_ros::transformPointCloud("/base_link", inputCloud, outCloud, *mTransformListener);
    /* Process the point cloud */
}

It initially worked for the first time, and I could transform the Point Cloud, however, now I am getting a strange error,

[ERROR] [1340908167.092985478]: Lookup would require extrapolation into the past.  

Requested time 1340908154.777419783 but the earliest data is at time 1340908155.041740035, when looking up transform from frame [/narrow_stereo_optical_frame] to frame [/base_link]
Failed to find a field named: 'x'. Cannot convert message to PCL type.
terminate called after throwing an instance of 'pcl::InvalidConversionException'
  what():  Failed to find a field named: 'x'. Cannot convert message to PCL type.
Aborted

Can anyone tell me what's wrong?

Thanks for your answer. I edited the code following your advice, but it still doesn't seem to work. I've posted the details below.

Thanks for your answer. On adding the the frame inside the header, the previous error is rectified. However, now, it gives me an error saying

terminate called after throwing an instance of 'tf::ExtrapolationException'

what(): Lookup would require extrapolation into the future.

I tried to get around this by myself editing the timestamp in the "min_in" header, and then I got the error

terminate called after throwing an instance of 'tf::ExtrapolationException'

what(): Lookup would require extrapolation into the past.

Any ideas on how I can fix this?

Thanks for your answer. I can't post a long comment, so please read my question posted below!

Hi All,

I am trying to convert PointStamped values from the narrow_stereo_link frame to the base_link frame using tf::TransformListener::transformPoint. However, I keep getting:

terminate called after throwing an instance of 'tf::LookupException'

what(): Frame id / does not exist!

In my code I have the following function call,

mTransformListener.waitForTransform("/narrow_stereo_link", "/base_link", ros::Time::now(), ros::Duration(5.0)); mTransformListener.transformPoint("/base_link", min_in, min_res);

On executing

rosrun tf tf_echo narrow_stereo_link base_link

on the terminal, I get the following output :

At time 1340824941.479

• Translation: [0.152, -0.117, -1.386]

• Rotation: in Quaternion [-0.110, 0.061, 0.869, -0.479]

      in RPY [0.214, 0.133, -2.119]
  

which means that the two are connected in the tf_tree, which is also seen in the frames.pdf generated by

rosrun tf view_frames

Can anyone help me with this?

I have a controller which moves the PR2's arms through some specified points. I've noticed that while executing the trajectory, it unnecessarily rotates its grippers by more than 360 degrees to get the orientation of it's wrist joint. What I mean is, instead of rotating by an angle x, it actually rotates by an angle 2kPi + x. I am doing angle correction to avoid this, but it's not working. Has anybody faced this? How do I change the kind of motion planning it does between the specified trajectory points?

I am a beginner with ROS. I am doing a simple task of writing a controller to move the PR2 arm through some predefined points. So, I need the values of [r_shoulder_pan_joint, r_shoulder_lift_joint, r_upper_arm_roll_joint, r_elbow_flex_joint, r_forearm_roll_joint, r_wrist_flex_joint, r_wrist_roll_joint] and similarly for the left arm, for each of these points. I move the PR2 arm through these points using the interactive manipulation, and am trying to listen to a topic to get these joint values. But I don't know what topic publishes these joint values. What topic should I subscribe to for this?

While simply following the tutorials to get familiar with ROS, as soon I run rxgraph, it stops with a segmentation fault immediately. Can I get some help?