Next-Best-View Exploration Planner

license: CC BY-NC-SA 3.0
autors: Victor Massague Respall, Devitt Dmitry, Fedorenko Roman

Table of Contents

• Overview
• Installation Instructions
• Parameters
  • General Parameters
  • System Parameters
  • Map Parameters
  • Gain Parameters
  • History Graph Parameters
  • Path Planning Parameters
  • Scenario Parameters
• Paper and Video
• Contact

Overview

The Next-Best-View Exploration Planner (NBV Exploration Planner) is a real-time capable exploration path planner. From the current pose it expands a tree to find a next pose that gives a high exploration gain in the vicinity of the MAV. As the vehicle is performing the exploration process, the current pose is stored as a node, indicating wheather a frontier is encountered in the vicinity, in a new data structure called History Graph, which creates a network of visited positions to rely on, when no gain is found in the vicinity of the MAV.

Installation Instructions

To install NBV Exploration Planner, please install ROS Kinetic or ROS Melodic for Ubuntu.

First install additional system dependencies (substitute DISTRO for kinetic or melodic as necessary):

sudo apt-get install python-wstool python-catkin-tools ros-DISTRO-cmake-modules protobuf-compiler autoconf

Next, add a few other dependencies. If you don’t have a catkin workspace yet, set it up as follows:

mkdir -p ~/catkin_ws/src
cd ~/catkin_ws
catkin init
catkin config --cmake-args -DCMAKE_BUILD_TYPE=Release

Clone the planner repository to your catkin workspace and install package dependecies

cd ~/catkin_ws/src/
git clone https://github.com/InnopolisAero/nbv_exploration_planner
wstool init . ./nbv_exploration_planner/dependencies.rosinstall
wstool update

If you have already initialized wstool replace the above wstool init with wstool merge -t

Finally, compile or build the workspace

cd ~/catkin_ws/src/
catkin build

Parameters

General Parameters

• tf_frame: The base frame used when looking up tf transforms. This is also the frame that most outputs are given in (string, default: "world")
• wp_z: Maximum height to perform the initialization motion (double, 1.0m)
• speed_rotate: Yaw speed of the initialization motion (double, 0.5rad/s)
• shift_initial_x: Shift of the MAV position after the initialization motion in x-direction (double, default: 0.0)
• shift_initial_y: Shift of the MAV position after the initialization motion in y-direction (double, default: 0.0)
• shift_initial_z: Shift of the MAV position after the initialization motion in z-direction (double, default: 0.0)
• path_plot: Path to store a log file of the exploration process, if left empty the log is not created. (string, required)

System Parameters

• system/v_max: Maximal linear speed (double, default: 1.0m/s)
• system/dyaw_max: Maximal yaw speed (double, default: 0.5rad/s)
• system/camera/pitch: Pitch angle of the depth sensors (list of doubles, default: 15deg)
• system/camera/horizontal: Horizontal Field of View (FOV) of the depth sensors (list of doubles, default: 90deg)
• system/camera/vertical: Vertical Field of View (FOV) of the depth sensors (list of doubles, default: 60deg)
• system/bbx/x: MAV bounding box for collision avoidance, dimension in x-direction (double, default: 0.5m)
• system/bbx/y: MAV bounding box for collision avoidance, dimension in y-direction (double, default: 0.5m)
• system/bbx/z: MAV bounding box for collision avoidance, dimension in z-direction (double, default: 0.3m)
• system/bbx/overshoot: Extension for collision check, that is added to the nominal length of the path segment (double, default: 0.5m)

Map Parameters

This parameters correspond to the package Voxblox. Please refer to the documentation for more information.

• tsdf_voxel_size: The size of the TSDF voxel, or in other words, resolution of the map (double, default: 0.15m)
• tsdf_voxels_per_side: TSDF voxels per side of an allocated block. Must be a power of 2 (int, default: 16)
• min_time_between_msgs_sec: Minimum time to wait after integrating a message before accepting a new one (double, default: 0.0s)
• min_ray_length_m: The point at which the ray casting will start (double, default: 0.1m)
• max_ray_length_m: The maximum range out to which a ray will be cast (double, default: 5.0m)
• voxel_carving_enabled: If true, the entire length of a ray is integrated, if false only the region inside the trunaction distance is used. (bool, default: true)
• color_mode: The method that will be used for coloring the mesh. ([“color”, “height”, “normals”, “lambert”, “gray”], default: "color")
• use_const_weight: If true all points along a ray have equal weighting (bool, default: false)
• publish_tsdf_map: Whether to publish the complete TSDF map periodically over ROS topics (bool, default: false)
• publish_esdf_map: Whether to publish the complete ESDF map periodically over ROS topics (bool, default: false)
• update_mesh_every_n_sec: Rate at which the mesh topic will be published to, a value of 0 disables (double, default: 0.0s)
• method: Method for TSDF integration (["simple", "merged", "fast"], default: "merged")
• allow_clear: If true points beyond the max_ray_length_m will be integrated up to this distance (bool, default: true)
• use_tf_transforms: If true the ros tf tree will be used to get the pose of the sensor relative to the world. If false the pose must be given via the transform topic. (bool, default: true)
• world_frame: The base frame used when looking up tf transforms. This is also the frame that most outputs are given in (string, default: "world")
• verbose: Prints additional debug and timing information (bool, default: true)

Gain Parameters

• nbvep/gain/free: Gain for visible free voxels (double, default: 0.0)
• nbvep/gain/occupied: Gain for visible occupied voxels (double, default: 0.0)
• nbvep/gain/unmapped: Gain for visible unmapped voxels (double, default: 1.0)
• nbvep/gain/range: Maximum distance of voxels to be considered for the gain computation (double, default: 1.0)
• nbvep/gain/zero: Threshold for considering a node with gain or not (double, default: 0.0)
• nbvep/gain/degressive_coeff: Weighting parameter for the summation of the node specific gains along the branches of the tree. A high coefficient punishes distance more (double, default: 0.0)

Path Planning Parameters

• nbvep/tree/extension_range: Maximum length for new tree branches when sampling (double, default: 1.0)
• nbvep/tree/vicinity_range: Maximum range to build the RRT around the MAV current position (double, default: 5.0m)
• nbvep/tree/init_iterations: Minimum number of nodes in the RRT at every iteration (int, default: 15)
• nbvep/tree/cutoff_iterations: Maximal number of iterations, when the exploration task is considered to be completed when no gain has been found (int, default: 200)
• nbvep/dt: Time step for path sampling (double, default: 0.1)

History Graph Parameters

• nbvep/graph/node_vicinity_range: Maximum range to search for frontier voxels around a History Graph node (double, default: 5.0m)
• nbvep/graph/zero_frontier_voxels: Minimum volume of voxels to consider a History Graph node active (double, default: 0.0)

Scenario Parameters

• bbx/minX: Minimum x-coordinate value of the scenario (double, required)
• bbx/minY: Minimum y-coordinate value of the scenario (double, required)
• bbx/minZ: Minimum z-coordinate value of the scenario (double, required)
• bbx/maxX: Maximum x-coordinate value of the scenario (double, required)
• bbx/maxY: Maximum y-coordinate value of the scenario (double, required)
• bbx/maxZ: Maximum z-coordinate value of the scenario (double, required)

Paper and Video

If you use this software in a scientific publication, please cite the following paper, available here:

Video running on-board of a real MAV can be see here and a simulation of the History Graph capabilities here.

Video of the ICRA presentation here

Contact

You can contact for any question or remark:

• Victor Massagué Respall