AlexKolb's profile - activity

Hi just to make sure: Have you checked if the usb2dynamixel adaper ist set to the right protocol? And if it is, is one of the red led's flashing when you search for motors?

Hey i have the same problem right now but i just cant figure out how to access the picking scheme. Could you give me a hint how to do it. Do i have to create a object from SelectionManager or something like that? (sorry im new to C++)

Hi guys,

I'm playing around with rviz right now and want to place an interactive maker over another cylindrical interactive marker, so that i can select a height with the smaller marker. My problem now is that the bigger marker blocks the arrows to drag the smaller marker along the axis. I already deactivated all interactive marker controls and made the marker transparent but i still can't select the arrow.

After some research i found out that i have to change the picking scheme of the object i want to hide.

"Objects without picking scheme are reliably ignored by assigning a zero selection handle"

Can someone help me with that. I don't have much experience with C++ so its hard to figure it out on my own. By the way is it possible to "reactivate" the marker again after i have selected the height?

Cheers, Alex

EDIT: i found another similar question on the forum but it didnt really help me, since it is really abstract too http://answers.ros.org/question/52853/rviz-get-interactive-object-behind-transparent-object/

Hi there

i just purchased a Dynamixel RX-24F motor to move a hokuyo laser scanner in order to get 3d point clouds. Right now im using dynamixel_motor package, and i set up a position controller with these parameters:

tilt_controller:
controller:
    package: dynamixel_controllers
    module: joint_position_controller
    type: JointPositionController
joint_name: tilt_joint
joint_speed: 0.2
motor:
    id: 1
    init: 512
    min: 0
    max: 1023
joint_compliance_slope: 254
joint_compliance_punch: 1

I really want to move the motor really slow to achieve a dense point cloud, but when the motor is moving at these speeds its like a slip stick motion.

Is there a way to get the motion more smooth with the dynamixel motor package, maybe with a trajectory controller or is there a better solution out there to control the motor.

thanks Alex

Hi there

I have a quit strange problem. I attached my hokuyo laser scanner to a dynamixel motor and im trying to get 3d clouds from this setup. I noticed that when i visualize the 2d laser scan witch is attached to frame laser and the tf data of the frame laser, the scan is lagging about 0.5 - 1 sec behind the arrow of the tf data visualization. The tf data itself seems to be fine but not the frame attached to it.

The result of this is that my point cloud is not perpendicular to the ground and the clouds of an upward scan and downward scan dosed align.

i calculate the tf data with this function:

void callback(const dynamixel_msgs::MotorStateList::ConstPtr& msg, tf::TransformBroadcaster broad) {

tf::Transform transform;
tf::Quaternion q;
q.setRPY(0, (((msg->motor_states[0].position)-512)*(5.23598776/1024)), 0);
transform.setRotation(q);
transform.setOrigin( tf::Vector3(0,0,0) );
broad.sendTransform(tf::StampedTransform(transform, ros::Time::now(), "axes_servo", "laser"));

}

To simplify it i set the servo_axes as fixed frame and the laser frame is just tilting around the x - axes. With tf monitor i get: Frame: servo_axes published by /tf_broadcaster Average Delay: -0.0997534 Max Delay: 0 Frame: laser published by /reading_servo_position Average Delay: 0.000255227 Max Delay: 0.00175389

Any idea whats going wrong?

thanks Alex

Edit: I set a different frame as fixed frame and know the motion of the tf arrow matches the delayed motion of the scan, but the cloud is still not align correctly.

Hi there

i have a basic question about program structure. I want to write a node that calls the laser_assembler service and publishes those scans witch have been taken during one tilt motion of my servo motor. To do so i thought of subscribing to the motor state msg the motor service publishes. How would you structure this node. Would you bind all the objects that are needed (service client, publisher ...) to the callback? Or would you write a class for this (witch would be basically my whole node). Or is it ok to have a couple of global variables?

thanks Alex

I had the same Problem. I've solved it by downloading the Dynamixel RoboPlus software http://www.robotis.com/xe/download_en . It provides the Dynamixel Wizard which will search for any motor attached. You can then change all of its settings.

In my case the baud rate was way off, like Teja Krishna already guessed.

Hi guys

im working on a buffer service that saves a bunch of data i get from a detection node. I also want to save the tf data from a moving object in that service. Now my question is should i avoid the while(ros::ok()) loop i need to listen to the tf data, by writing a new node that sends the tf data to the service if it changed or is it usual to use while loops in ros services. Im just a little bit worried that the callback from the client would be delayed or the program would get stuck in the loop.

Thanks Alex

Hey guys,

I'm detecting cylindrical objects in a point cloud and want to use a service to save all the data of the cylinders and make them accessible to other nodes. What i'm having trouble with is that i want to visualize the cylinders in rviz and therefor i need the center point and the quaternion, but the segmentation function of pcl gives me two vectors, bottom point and a direction vector. I already managed to compensate the offset from the bottom point to center point by simple vector calculations and to get the quaternion from the two vectors but i need the bottom point and don't want to save all of this information.

Is there a way to save just the bottom point and the quaternion and "slide" the bottom point along the quaternion up for half the cylinder hight, whenever i want to visualize it in rviz? Or do you think that the data size wouldn't be problematic if i have to save up to 1000 cylinder datasets containing two 3Dvectors and quaternion?

cheers

Alex

Edit: To sum it up: Is it possible to calculate the center point with just the bottom point and the quaternion?

thanks, but whats the math behind it? How can i calculate the center point for the cylinder with the bottom point and the quaternion?