move_group_interface, pose goal not reached correctly

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Hi,

I use MoveIt! and ros-melodic. Currently, I am making simple motion planning exercises using move_group_interface. I test these within rviz and finally on the real robotic arm ur5.

Following the tutorials available here, I make plans for joint-space goals and pose-goals. I have tried to use either of the following kinematics plugins.

• kdl_kinematics_plugin/KDLKinematicsPlugin
• ur_kinematics/UR5KinematicsPlugin

While, movement for the joint-space goal is ok, I do not see correct results for the pose-goal. For example, I specify the following example target pose goal.

  geometry_msgs::Pose sample_pose;

  // specfiy a simple pose of the end-effector
  sample_pose.orientation.x = 1.35;
  sample_pose.orientation.y = -2.33;
  sample_pose.orientation.z = -2.29;
  sample_pose.position.x = 0.0;
  sample_pose.position.y = -0.193;
  sample_pose.position.z = 1.0;

I plan to this pose goal, and I print the coordinates (orientation and position) before and after planning this movement. However, my results, after the plan has been done, do not match the target specified in sample_pose. Here is the code of the function.

void SimpleMotionPlanning::goToPoseGoal()
{
  geometry_msgs::PoseStamped currPose = move_group.getCurrentPose();
  ROS_INFO_STREAM("current pose: " << currPose);

  move_group.setPoseTarget(sample_pose);
  move_group.setGoalTolerance(0.2);

  bool success = (move_group.plan(my_plan) == moveit::planning_interface::MoveItErrorCode::SUCCESS);
  if (!success) //execute
    throw std::runtime_error("No plan found");

  move_group.execute(my_plan);

  currPose = move_group.getCurrentPose();
  ROS_INFO_STREAM("pose after movement: " << currPose); }

And, values before and after the movement.

pose before movement: 
  position: 
    x: 0.81725
    y: 0.19145
    z: -0.005491
  orientation: 
    x: 0.707107
    y: 0.707107
    z: 3.46245e-12
    w: 3.46245e-12

pose after movement:
  position: 
    x: -0.0865113
    y: -0.155637
    z: 0.855142
  orientation: 
    x: 0.0154331
    y: -0.0230949
    z: -0.0882203
    w: 0.995714

As we can see, the final values differ significantly from the target given in sample_pose. Do, we need to specifically compute inverse kinematics (joint angles) that will correspond to the sample_pose, and then some how, set those as a joint-space goal.

thanks for your help.

zahid