抓取与放置

注意：本教程中使用的功能已弃用。如需执行抓取与放置操作，应使用 MoveIt Task Constructor（MTC）（用 MoveIt Task Constructor 实现抓取与放置）。

在 MoveIt 中，抓取操作通过 MoveGroup 接口完成。为了抓取物体，我们需要创建 moveit_msgs::Grasp 消息，该消息可定义抓取过程中涉及的各种位姿和手爪姿态。下面的视频展示了本教程的运行效果：

入门

如果尚未完成，请先完成 Getting Started 中的步骤。

运行演示

打开两个终端。在第一个终端中启动 RViz，等待所有内容加载完成：

roslaunch panda_moveit_config demo.launch

在第二个终端中运行抓取与放置教程：

rosrun moveit_tutorials pick_place_tutorial

你应该会看到与本教程开头视频类似的效果。

理解 `moveit_msgs::Grasp`

完整的文档请参阅 moveit_msgs/Grasp.msg。

该消息的主要字段如下：

trajectory_msgs/JointTrajectory pre_grasp_posture：定义抓取前末端执行器规划组中各关节的轨迹位置。
trajectory_msgs/JointTrajectory grasp_posture：定义抓取物体时末端执行器规划组中各关节的轨迹位置。
geometry_msgs/PoseStamped grasp_pose：末端执行器尝试抓取时的位姿。
moveit_msgs/GripperTranslation pre_grasp_approach：定义接近物体时的方向和移动距离。
moveit_msgs/GripperTranslation post_grasp_retreat：定义抓取物体后撤离的方向和移动距离。
moveit_msgs/GripperTranslation post_place_retreat：定义物体放置后撤离的方向和移动距离。

完整代码

完整代码可在 moveit_tutorials GitHub 项目中查看：此处。

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/* Author: Ioan Sucan, Ridhwan Luthra*/

// ROS
#include <ros/ros.h>

// MoveIt
#include <moveit/planning_scene_interface/planning_scene_interface.h>
#include <moveit/move_group_interface/move_group_interface.h>

// TF2
#include <tf2_geometry_msgs/tf2_geometry_msgs.h>

void openGripper(trajectory_msgs::JointTrajectory& posture)
{
  // BEGIN_SUB_TUTORIAL open_gripper
  /* Add both finger joints of panda robot. */
  posture.joint_names.resize(2);
  posture.joint_names[0] = "panda_finger_joint1";
  posture.joint_names[1] = "panda_finger_joint2";

  /* Set them as open, wide enough for the object to fit. */
  posture.points.resize(1);
  posture.points[0].positions.resize(2);
  posture.points[0].positions[0] = 0.04;
  posture.points[0].positions[1] = 0.04;
  posture.points[0].time_from_start = ros::Duration(0.5);
  // END_SUB_TUTORIAL
}

void closedGripper(trajectory_msgs::JointTrajectory& posture)
{
  // BEGIN_SUB_TUTORIAL closed_gripper
  /* Add both finger joints of panda robot. */
  posture.joint_names.resize(2);
  posture.joint_names[0] = "panda_finger_joint1";
  posture.joint_names[1] = "panda_finger_joint2";

  /* Set them as closed. */
  posture.points.resize(1);
  posture.points[0].positions.resize(2);
  posture.points[0].positions[0] = 0.00;
  posture.points[0].positions[1] = 0.00;
  posture.points[0].time_from_start = ros::Duration(0.5);
  // END_SUB_TUTORIAL
}

void pick(moveit::planning_interface::MoveGroupInterface& move_group)
{
  // BEGIN_SUB_TUTORIAL pick1
  // Create a vector of grasps to be attempted, currently only creating single grasp.
  // This is essentially useful when using a grasp generator to generate and test multiple grasps.
  std::vector<moveit_msgs::Grasp> grasps;
  grasps.resize(1);

  // Setting grasp pose
  // ++++++++++++++++++++++
  // This is the pose of panda_link8. |br|
  // Make sure that when you set the grasp_pose, you are setting it to be the pose of the last link in
  // your manipulator which in this case would be **panda_link8** You will have to compensate for the
  // transform from **panda_link8** to the palm of the end effector.
  grasps[0].grasp_pose.header.frame_id = "panda_link0";
  tf2::Quaternion orientation;
  orientation.setRPY(-M_PI / 2, -M_PI / 4, -M_PI / 2);
  grasps[0].grasp_pose.pose.orientation = tf2::toMsg(orientation);
  grasps[0].grasp_pose.pose.position.x = 0.415;
  grasps[0].grasp_pose.pose.position.y = 0;
  grasps[0].grasp_pose.pose.position.z = 0.5;

  // Setting pre-grasp approach
  // ++++++++++++++++++++++++++
  /* Defined with respect to frame_id */
  grasps[0].pre_grasp_approach.direction.header.frame_id = "panda_link0";
  /* Direction is set as positive x axis */
  grasps[0].pre_grasp_approach.direction.vector.x = 1.0;
  grasps[0].pre_grasp_approach.min_distance = 0.095;
  grasps[0].pre_grasp_approach.desired_distance = 0.115;

  // Setting post-grasp retreat
  // ++++++++++++++++++++++++++
  /* Defined with respect to frame_id */
  grasps[0].post_grasp_retreat.direction.header.frame_id = "panda_link0";
  /* Direction is set as positive z axis */
  grasps[0].post_grasp_retreat.direction.vector.z = 1.0;
  grasps[0].post_grasp_retreat.min_distance = 0.1;
  grasps[0].post_grasp_retreat.desired_distance = 0.25;

  // Setting posture of eef before grasp
  // +++++++++++++++++++++++++++++++++++
  openGripper(grasps[0].pre_grasp_posture);
  // END_SUB_TUTORIAL

  // BEGIN_SUB_TUTORIAL pick2
  // Setting posture of eef during grasp
  // +++++++++++++++++++++++++++++++++++
  closedGripper(grasps[0].grasp_posture);
  // END_SUB_TUTORIAL

  // BEGIN_SUB_TUTORIAL pick3
  // Set support surface as table1.
  move_group.setSupportSurfaceName("table1");
  // Call pick to pick up the object using the grasps given
  move_group.pick("object", grasps);
  // END_SUB_TUTORIAL
}

void place(moveit::planning_interface::MoveGroupInterface& group)
{
  // BEGIN_SUB_TUTORIAL place
  // TODO(@ridhwanluthra) - Calling place function may lead to "All supplied place locations failed. Retrying last
  // location in verbose mode." This is a known issue. |br|
  // |br|
  // Ideally, you would create a vector of place locations to be attempted although in this example, we only create
  // a single place location.
  std::vector<moveit_msgs::PlaceLocation> place_location;
  place_location.resize(1);

  // Setting place location pose
  // +++++++++++++++++++++++++++
  place_location[0].place_pose.header.frame_id = "panda_link0";
  tf2::Quaternion orientation;
  orientation.setRPY(0, 0, M_PI / 2);
  place_location[0].place_pose.pose.orientation = tf2::toMsg(orientation);

  /* For place location, we set the value to the exact location of the center of the object. */
  place_location[0].place_pose.pose.position.x = 0;
  place_location[0].place_pose.pose.position.y = 0.5;
  place_location[0].place_pose.pose.position.z = 0.5;

  // Setting pre-place approach
  // ++++++++++++++++++++++++++
  /* Defined with respect to frame_id */
  place_location[0].pre_place_approach.direction.header.frame_id = "panda_link0";
  /* Direction is set as negative z axis */
  place_location[0].pre_place_approach.direction.vector.z = -1.0;
  place_location[0].pre_place_approach.min_distance = 0.095;
  place_location[0].pre_place_approach.desired_distance = 0.115;

  // Setting post-place retreat
  // ++++++++++++++++++++++++++
  /* Defined with respect to frame_id */
  place_location[0].post_place_retreat.direction.header.frame_id = "panda_link0";
  /* Direction is set as negative y axis */
  place_location[0].post_place_retreat.direction.vector.y = -1.0;
  place_location[0].post_place_retreat.min_distance = 0.1;
  place_location[0].post_place_retreat.desired_distance = 0.25;

  // Setting posture of eef after placing object
  // +++++++++++++++++++++++++++++++++++++++++++
  /* Similar to the pick case */
  openGripper(place_location[0].post_place_posture);

  // Set support surface as table2.
  group.setSupportSurfaceName("table2");
  // Call place to place the object using the place locations given.
  group.place("object", place_location);
  // END_SUB_TUTORIAL
}

void addCollisionObjects(moveit::planning_interface::PlanningSceneInterface& planning_scene_interface)
{
  // BEGIN_SUB_TUTORIAL table1
  //
  // Creating Environment
  // ^^^^^^^^^^^^^^^^^^^^
  // Create vector to hold 3 collision objects.
  std::vector<moveit_msgs::CollisionObject> collision_objects;
  collision_objects.resize(3);

  // Add the first table where the cube will originally be kept.
  collision_objects[0].id = "table1";
  collision_objects[0].header.frame_id = "panda_link0";

  /* Define the primitive and its dimensions. */
  collision_objects[0].primitives.resize(1);
  collision_objects[0].primitives[0].type = collision_objects[0].primitives[0].BOX;
  collision_objects[0].primitives[0].dimensions.resize(3);
  collision_objects[0].primitives[0].dimensions[0] = 0.2;
  collision_objects[0].primitives[0].dimensions[1] = 0.4;
  collision_objects[0].primitives[0].dimensions[2] = 0.4;

  /* Define the pose of the table. */
  collision_objects[0].primitive_poses.resize(1);
  collision_objects[0].primitive_poses[0].position.x = 0.5;
  collision_objects[0].primitive_poses[0].position.y = 0;
  collision_objects[0].primitive_poses[0].position.z = 0.2;
  collision_objects[0].primitive_poses[0].orientation.w = 1.0;
  // END_SUB_TUTORIAL

  collision_objects[0].operation = collision_objects[0].ADD;

  // BEGIN_SUB_TUTORIAL table2
  // Add the second table where we will be placing the cube.
  collision_objects[1].id = "table2";
  collision_objects[1].header.frame_id = "panda_link0";

  /* Define the primitive and its dimensions. */
  collision_objects[1].primitives.resize(1);
  collision_objects[1].primitives[0].type = collision_objects[1].primitives[0].BOX;
  collision_objects[1].primitives[0].dimensions.resize(3);
  collision_objects[1].primitives[0].dimensions[0] = 0.4;
  collision_objects[1].primitives[0].dimensions[1] = 0.2;
  collision_objects[1].primitives[0].dimensions[2] = 0.4;

  /* Define the pose of the table. */
  collision_objects[1].primitive_poses.resize(1);
  collision_objects[1].primitive_poses[0].position.x = 0;
  collision_objects[1].primitive_poses[0].position.y = 0.5;
  collision_objects[1].primitive_poses[0].position.z = 0.2;
  collision_objects[1].primitive_poses[0].orientation.w = 1.0;
  // END_SUB_TUTORIAL

  collision_objects[1].operation = collision_objects[1].ADD;

  // BEGIN_SUB_TUTORIAL object
  // Define the object that we will be manipulating
  collision_objects[2].header.frame_id = "panda_link0";
  collision_objects[2].id = "object";

  /* Define the primitive and its dimensions. */
  collision_objects[2].primitives.resize(1);
  collision_objects[2].primitives[0].type = collision_objects[1].primitives[0].BOX;
  collision_objects[2].primitives[0].dimensions.resize(3);
  collision_objects[2].primitives[0].dimensions[0] = 0.02;
  collision_objects[2].primitives[0].dimensions[1] = 0.02;
  collision_objects[2].primitives[0].dimensions[2] = 0.2;

  /* Define the pose of the object. */
  collision_objects[2].primitive_poses.resize(1);
  collision_objects[2].primitive_poses[0].position.x = 0.5;
  collision_objects[2].primitive_poses[0].position.y = 0;
  collision_objects[2].primitive_poses[0].position.z = 0.5;
  collision_objects[2].primitive_poses[0].orientation.w = 1.0;
  // END_SUB_TUTORIAL

  collision_objects[2].operation = collision_objects[2].ADD;

  planning_scene_interface.applyCollisionObjects(collision_objects);
}

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

  ros::WallDuration(1.0).sleep();
  moveit::planning_interface::PlanningSceneInterface planning_scene_interface;
  moveit::planning_interface::MoveGroupInterface group("panda_arm");
  group.setPlanningTime(45.0);

  addCollisionObjects(planning_scene_interface);

  // Wait a bit for ROS things to initialize
  ros::WallDuration(1.0).sleep();

  pick(group);

  ros::WallDuration(1.0).sleep();

  place(group);

  ros::waitForShutdown();
  return 0;
}

// BEGIN_TUTORIAL
// CALL_SUB_TUTORIAL table1
// CALL_SUB_TUTORIAL table2
// CALL_SUB_TUTORIAL object
//
// Pick Pipeline
// ^^^^^^^^^^^^^
// CALL_SUB_TUTORIAL pick1
// openGripper function
// """"""""""""""""""""
// CALL_SUB_TUTORIAL open_gripper
// CALL_SUB_TUTORIAL pick2
// closedGripper function
// """"""""""""""""""""""
// CALL_SUB_TUTORIAL closed_gripper
// CALL_SUB_TUTORIAL pick3
//
// Place Pipeline
// ^^^^^^^^^^^^^^
// CALL_SUB_TUTORIAL place
// END_TUTORIAL

抓取与放置

入门

运行演示

理解 moveit_msgs::Grasp

完整代码

理解 `moveit_msgs::Grasp`