daalt's profile - activity

I have a concept for an arm that I'm trying to model in URDF and simulate in RViz using Moveit! The problem is that the joint angle for the second arm segment is dependent on the joint angle of the first arm segment (i.e., if the first segment rotates by theta, then so too will the second joint. You see this kind of mechanism used on certain desk lamps. The following YouTube video gives you a visual example of what I'm talking about:

   http://youtu.be/kb7sMt0lyDY

How should I go about modeling this in URDF? Rather than giving this arm a special treatment in URDF, is doing something in Moveit! an option so as to drive the kinematics of this unique type of mechanism?

I'm trying to set a planning goal for MoveIt! but I keep getting an "Unable to sample any valid states for goal tree" error. My Python code is shown below. Anything wrong with this?

group = MoveGroupCommander("robot_arm_group")
group.allow_replanning(True)

#set start state
group.set_start_state_to_current_state()

#set goal state
target_pose = PoseStamped()
target_pose.header.frame_id = 'base_link' 
target_pose.header.stamp = rospy.Time.now() 
target_pose.pose.position.x = 1.3 
target_pose.pose.position.y = 0.4
target_pose.pose.position.z = 0.6
target_pose.pose.orientation.x = 0.0 
target_pose.pose.orientation.y = 0.0 
target_pose.pose.orientation.z = 0.0 
target_pose.pose.orientation.w = 1.0 

group.set_pose_target(target_pose, end_effector_link="forearm")

group.go()

Thanks, lfr. Launch file runs fine without <node> line. Why would node run successfully with rosrun but not roslaunch?

This slightly different than http://answers.ros.org/question/23808... although it appears to generate the same exit code -11. In this case, it's the launch file that triggering the error. In the previous thread, the moveit_commander.RobotCommander() line failed.

I have a node that I can run successfully using:

rosrun <package> <node_name>

In my particular case, my package is called "robot_arm" and node is "ReceiveOrder":

rosrun robot_arm ReceiveOrder

However, ReceiveOrder crashes when I try to run it via a launch file:

<launch>

    <rosparam command="load" file="$(find dispatcher)/dispatcher.yaml"/>
    <rosparam command="load" file="$(find robot_arm)/robot.yaml"/>

    <node name="ReceiveOrder" pkg="robot_arm" type="ReceiveOrder.py" output="screen"/>

</launch>

The error I get from running the launch file is as follows below. Why is this happening?

started roslaunch server http://HPLaptop:39521/

SUMMARY
========

PARAMETERS
 * /motion_planning/orient_tolerance: 0.05
 * /motion_planning/planning_engine: LBKPIECEkConfigDe...
 * /motion_planning/position_tolerance: 0.05
 * /motor_controller/num_motors: 6
 * /motor_controller/rate: 50
 * /order_timeout: 60
 * /robot/feedback_rate: 10
 * /robot/robot_id: 1
 * /robot/robot_timeout: 20
 * /rosdistro: indigo
 * /rosversion: 1.11.19

NODES
  /
    ReceiveOrder (robot_arm/ReceiveOrder.py)

ROS_MASTER_URI=http://localhost:11311

core service [/rosout] found
process[ReceiveOrder-1]: started with pid [13096]
[ReceiveOrder-1] process has died [pid 13096, exit code -11, cmd /home/altemir/ar01/src/robot_arm/src/ReceiveOrder.py __name:=ReceiveOrder __log:=/home/altemir/.ros/log/a6ba0c8e-3cda-11e6-a0d0-002315aba7e4/ReceiveOrder-1.log].
log file: /home/altemir/.ros/log/a6ba0c8e-3cda-11e6-a0d0-002315aba7e4/ReceiveOrder-1*.log
all processes on machine have died, roslaunch will exit
shutting down processing monitor...
... shutting down processing monitor complete

One thing I noticed when I studied the tutorials more closely is that I didn't have the correct package directory structure with a "src" subdirectory under the package directory. Rebuilding the project with the correct directory structure resulted in me being able to successfully run the node.

I tried to model my new C++ node as closely to the Actionlib Simple Action Server tutorial ( http://wiki.ros.org/actionlib_tutoria... ) but I keep getting the following error when running catkin_make:

CMake Error at robot_arm/CMakeLists.txt:20 (add_dependencies):
  add_dependencies called with incorrect number of arguments

What could be wrong with my add_dependencies statement?

Only thing I can think of is that ${robot_arm_EXPORTED_TARGETS} is not getting populated such that catkin_make may think this argument is missing. How can I confirm this?

My CMakeLists.txt is:

cmake_minimum_required(VERSION 2.8.3)
project(robot_arm)

find_package(catkin REQUIRED COMPONENTS roscpp actionlib actionlib_msgs)
find_package(Boost REQUIRED COMPONENTS system)

catkin_package(
  CATKIN_DEPENDS actionlib_msgs common
)

include_directories(include ${catkin_INCLUDE_DIRS} ${Boost_INCLUDE_DIRS})

add_executable(ReceiveOrder ReceiveOrder.cpp)

target_link_libraries(
  ReceiveOrder
  ${catkin_LIBRARIES}
)

add_dependencies(
  ReceiveOrder
  ${robot_arm_EXPORTED_TARGETS}
)

Thanks, gvdhoorn. I also ran a barebones node and it failed immediately after the moveit_commander import. Error message mentioned:

boost: mutex lock failed in pthread_mutex_lock: Invalid argument

I'll start a new thread on this before submitting an issue.

No C/C++ interop within my node. I traced it to the following line where the node crashes:

robot = moveit_commander.RobotCommander()

I made the following imports so I would think that this command is supported:

import sys
import copy
import rospy
import moveit_commander

I have a node, "ReceiveOrder.py", that is run via a roslaunch file and unexpectedly dies when I run it.

I have two clues to offer:

1) The following is part of what I see in the roslaunch terminal window. You'll see that exit code -11 is shown. What does this mean? I don't see anything else that is more specific in this runtime feedback

NODES
  /
    ReceiveOrder (robot_arm/ReceiveOrder.py)
    rviz_HPLaptop_4443_4042809988877892707 (rviz/rviz)

ROS_MASTER_URI=http://localhost:11311

core service [/rosout] found
process[ReceiveOrder-1]: started with pid [4461]
process[rviz_HPLaptop_4443_4042809988877892707-2]: started with pid [4462]
[ INFO] [1466968712.255484346]: rviz version 1.11.14
[ INFO] [1466968712.255610062]: compiled against Qt version 4.8.6
[ INFO] [1466968712.255653092]: compiled against OGRE version 1.8.1 (Byatis)
[ INFO] [1466968712.466849981]: Stereo is NOT SUPPORTED
[ INFO] [1466968712.467064489]: OpenGl version: 2.1 (GLSL 1.2).
[ReceiveOrder-1] process has died [pid 4461, exit code -11, cmd /home/daalt/ar01/src/robot_arm/ReceiveOrder.py __name:=ReceiveOrder __log:=/home/daalt/.ros/log/1300bd8c-3bcf-11e6-8a67-002315aba7e4/ReceiveOrder-1.log].
log file: /home/daalt/.ros/log/1300bd8c-3bcf-11e6-8a67-002315aba7e4/ReceiveOrder-1*.log

2) I only see [INFO] messages in the ReceiveOrder-1.log file, no warnings or errors. However there is this line that suggests that something is going on with the rospy clock:

[rospy.simtime][INFO] 2016-06-26 14:18:32,722: /use_sim_time is not set, will not subscribe to simulated time [/clock] topic

The only place where the question of clock comes into question, as far as I know, is when I define a spin rate in the "ReceiveOrder.py" Python node.

I'm not sure what direction to go in based on these clues. Does anyone suspect something specific going on here or, at least, suggest something I can do to investigate further?

Thank you, ROS community!!

prosa100,

It's been a while since you posted this question but I was just wondering how your project to teach ROS to the FRC community turned out. Did you develop any tutorials or packages? Can you please contact me at altemir .at. verizon dot net and let me know?

I get the following warning when running my custom action server:

[WARN] [WallTime: 1386219718.920124] You've passed in true for auto_start to the python action server, you should always pass in false to avoid race conditions.

Two questions:

1) If actionlib only handles one goal at a time, how conceivably could race conditions occur?

2) Where and how exactly is the auto_start parameter passed?

I was working through the MoveIt tutorials in which I launched the PR2 configuration demo using the RViz plugin and saw how you could use the 6-DOF interactive markers to move the robot joints. I then tried to do the same thing for my robot, but the interactive markers don't appear. Nothing happens when I click on the "Interact" button in RViz. The button is selected but my mouse cursor still displays as the camera control cursor.

How can I check to see what's preventing RViz from allowing me to interact with my robot?