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Motion planning for Y-shaped robot with pose goals

asked 2021-09-17 13:54:51 -0600

Peter_Mitrano gravatar image

updated 2021-09-19 16:15:09 -0600

My robot has two torso joints and then two 7-dof arms. I am using the BioIK kinematics plugin which should be able to sample configurations with a specified orientation for one end effector.

I want to plan with the whole group to reach a pose with one of the end effectors, but I get the following error and planning fails: This kinematic solver has more than one tip frame, do not call getTipFrame()

Is what I want possible? What am I doing wrong?

Here's the code

#include <ros/ros.h>

#include <moveit/kinematic_constraints/utils.h>
#include <moveit/planning_interface/planning_interface.h>
#include <moveit/planning_pipeline/planning_pipeline.h>
#include <moveit/planning_scene_monitor/planning_scene_monitor.h>
#include <moveit/robot_model_loader/robot_model_loader.h>
#include <moveit/robot_state/conversions.h>
#include <moveit_msgs/DisplayTrajectory.h>
#include <moveit_visual_tools/moveit_visual_tools.h>

int main(int argc, char** argv) {
  ros::init(argc, argv, "move_group_tutorial");
  ros::AsyncSpinner spinner(1);
  spinner.start();
  ros::NodeHandle nh;

  std::string const group_name = "both_arms";

  auto robot_model_loader = std::make_shared<robot_model_loader::RobotModelLoader>("hdt_michigan/robot_description");
  auto psm = std::make_shared<planning_scene_monitor::PlanningSceneMonitor>(robot_model_loader);

  std::string const robot_namespace = "hdt_michigan";
  auto const scene_topic = ros::names::append(robot_namespace, "move_group/monitored_planning_scene");
  psm->startSceneMonitor(scene_topic);

  auto robot_model = robot_model_loader->getModel();

  auto robot_state =
      std::make_shared<moveit::core::RobotState>(planning_scene_monitor::LockedPlanningSceneRO(psm)->getCurrentState());

  auto planning_pipeline = std::make_shared<planning_pipeline::PlanningPipeline>(robot_model, nh);

  auto display_publisher =
      nh.advertise<moveit_msgs::DisplayTrajectory>("hdt_michigan/move_group/display_planned_path", 10);
  moveit_msgs::DisplayTrajectory display_trajectory;

  namespace rvt = rviz_visual_tools;
  moveit_visual_tools::MoveItVisualTools visual_tools("robot_root");
  visual_tools.deleteAllMarkers();

  // Pose Goal
  planning_interface::MotionPlanRequest req;
  planning_interface::MotionPlanResponse res;
  geometry_msgs::PoseStamped pose;
  pose.header.frame_id = "robot_root";
  pose.pose.position.x = -0.2;
  pose.pose.position.y = 0.6;
  pose.pose.position.z = 0.4;

  tf2::Quaternion myQuaternion;
  myQuaternion.setRPY(-M_PI_2, 0, 0);
  myQuaternion = myQuaternion.normalize();
  pose.pose.orientation.x = myQuaternion.x();
  pose.pose.orientation.y = myQuaternion.y();
  pose.pose.orientation.z = myQuaternion.z();
  pose.pose.orientation.w = myQuaternion.w();

  std::vector<double> tolerance_pose(3, 0.01);
  std::vector<double> tolerance_angle(3, 0.01);

  req.group_name = group_name;
  auto pose_goal = kinematic_constraints::constructGoalConstraints("left_tool", pose, tolerance_pose, tolerance_angle);
  req.goal_constraints.push_back(pose_goal);

  {
    planning_scene_monitor::LockedPlanningSceneRO lscene(psm);
    planning_pipeline->generatePlan(lscene, req, res);
  }

  if (res.error_code_.val != res.error_code_.SUCCESS) {
    ROS_ERROR("Could not compute plan successfully");
    return 0;
  }

  std::cin.get();

  return 0;
}

Update

I've tried just planning with a "left_arm_with_torso" group, but I'm getting slightly different errors. Changing nothing but the group name, now gives:

[ INFO] [1632085872.286359638, 23724.820000000]: Using planning interface 'OMPL'
[ INFO] [1632085872.288865232, 23724.820000000]: The timeout for planning must be positive (0.000000 specified). 
Assuming one second instead.
[ERROR] [1632085872.288767452, 23724.820000000]: Found empty JointState message
[ WARN] [1632085872.288938533, 23724.820000000]: It looks like the planning volume was not specified.
[ERROR] [1632085872.289341162, 23724.820000000]: This kinematic solver has more than one tip frame, do not call 
getTipFrame()
[ERROR] [1632085872.289945357, 23724.830000000]: IK cannot be performed for link 'left_tool'. The solver can report 
IK solutions for link 'drive10'.
[ERROR] [1632085872.290004038, 23724.830000000]: Unable to construct goal representation
[ERROR] [1632085872.290087072, 23724.830000000]: Could not compute plan successfully
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Comments

@Peter_Mitrano: could I ask you to please not link to 3rd party sites for code snippets of moderate length? Try to keep ROS Answers Q&As stand-alone by including relevant parts of questions in the question text itself.

gvdhoorn gravatar image gvdhoorn  ( 2021-09-18 02:26:01 -0600 )edit

1 Answer

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answered 2021-09-17 16:42:36 -0600

v4hn gravatar image

If you specify a planning group with multiple tips, MoveIt expects that you specify a target for each one. the easiest solution for your example code would be to use a second planning group, e. g. "left_arm_with_torso" that leaves out the right subchain.

if you explicitly need to sample for the right arm as well in your request, e. g., to avoid collisions or maintain a center of gravity, you can instead call ik via setFromIK before you invoke the planning pipeline and pass joint state targets to the planner. That also allows to pass other ik objectives.

It probably make sense to support the use case in your example. feel free to create an issue pointing out the related source code locations and we can have a closer look.

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Asked: 2021-09-17 13:54:51 -0600

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Last updated: Sep 19 '21