lotfishtaine's profile - activity

Hello,

I'm trying to create a map of the environment using pcl_ndt. I use data from simulated velodyne in gazebo. I'm subscribing to PointCloud2 msg and publishing the genrated map via PointCloud2 msg in new topic /ndt_map

However, after a few seconds of publishing /nadt_map topic, I got this warning :

Warning: TF_OLD_DATA ignoring data from the past for frame base_link at time 36,221 according to authority /ndt_map
Possible reasons are listed at http://wiki.ros.org/tf/Errors%20explained
         at line 277 in /tmp/binarydeb/ros-melodic-tf2-0.6.5/src/buffer_core.cpp

I already used this command that should have solved the problem:

rosparam set use_sim_time true

but the error still persist.

I saw that this could happen when reproducing bagfile, but for my case, I'm using online data from the gazebo simulator.

Thanks for helping shedding light on this issue!

UPDATE: this is my callback :

void pts_callback(const sensor_msgs::PointCloud2::ConstPtr& input){
        // Convert the sensor_msgs/PointCloud2 data to pcl/PointCloud
        pcl::fromROSMsg(*input, cloud);

        ndt.align(*outputCloud, init);

        // Get the transformation matrix
        t = ndt.getFinalTransformation();

        // Transforme the cloud with the transformation matrix
        pcl::transformPointCloud(cloud, *transformed_cloud, t);

    tf::TransformBroadcaster br;
        tf::Transform transform;

    //create tf transform from t
    transform = get_tf_transform(t);

        br.sendTransform(tf::StampedTransform(transform, input->header.stamp, "world", "base_link"));

        sensor_msgs::PointCloud2::Ptr map_msg(new sensor_msgs::PointCloud2);
        pcl::toROSMsg(*transformed_cloud, *map_msg);

        ndt_pub.publish(*map_msg);
}

I'm subscribing to VelodyneScan packets with :

points_sub_ = nd.subscribe("velodyne_points", 100000, &pts_callback, this);

and I publish map with :

ndt_pub = nd.advertise<sensor_msgs::PointCloud2>("ndt_map", 1000);

I tried with ros::Time() tf::TransformListener listener; tf::StampedTransform transform; try{ listener.waitForTran

I tried with ros::Time() tf::TransformListener listener1; tf::StampedTransform transform; try{ listener1.waitForTr

get rotation state of a joint with tf::listener.lookupTransform Hello everyone, I have a velodyne with a rotating joint

Hello everyone,

I'm trying to control a rotating joint type "continuous" in velocity, and simulate it in Gazebo.

This is the URDF joint definition:

<joint name="${name}_joint" type="continuous"> 
      <xacro:insert_block name="origin" />
      <parent link="${namespace}/${parent}"/>
      <child link="${namespace}/${name}"/>
      <axis xyz="1 0 0" rpy="0 0 0" />
      <limit effort="2000.0" velocity="40.0" />
    </joint>

    <gazebo>
      <plugin name="gazebo_ros_control" filename="libgazebo_ros_control.so">
        <robotNamespace>${namespace}</robotNamespace>
      </plugin>
    </gazebo>

    <transmission name="${name}_joint_trans">
      <type>transmission_interface/SimpleTransmission</type>
      <joint name="${name}_joint">
        <hardwareInterface>hardware_interface/VelocityJointInterface</hardwareInterface>
      </joint>
      <actuator name="${name}_joint_motor">
        <hardwareInterface>hardware_interface/VelocityJointInterface</hardwareInterface>
        <mechanicalReduction>1</mechanicalReduction>
      </actuator>
    </transmission>

and the config yaml file for controllers:

 joint_state_controller:
    type: joint_state_controller/JointStateController
    publish_rate: 60

  my_joint_position_controller:
    type: velocity_controllers/JointVelocityController
    joint: my_joint
    pid: {p: 0.5, i: 0.6, d: 0.0035}

I have couple of questions:

• first, can someone explain the yaml file or give a tutorial explaining this? what is "publish_rate" and what is its role? how can influence the rotation? same for "joint_state_controller"?

• Second, to change the joint velocity I run :

  rostopic pub /my_joint_position_controller/command std_msgs/Float64 "data: 5.0"

  the data value is a linear velocity (m/s) or rotational velocity (rad/s) ? If it is a linear velocity, how can I transform that to rotational velocity (rad/s)?

• third, how can I get the joint angle at every moment?

Thanks in advance.

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How to control a rotating joint in velocity Hello everyone, I'm trying to control a rotating joint type "continuous" in

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Yes, for the broadcasting I use input->header.stamp I updated the question with the callback that I used. See edit ab

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