nd

Nearness Diagram Navigation. More...

Nearness Diagram Navigation.

This driver implements the Nearness Diagram Navigation algorithm. This algorithm handles local collision-avoidance and goal-seeking and is designed for non-holonomic, non-circular robots operating in tight spaces. The algorithm is in the following papers:

• J. Minguez, L. Montano. Nearness Diagram Navigation (ND): Collision Avoidance in Troublesome Scenarios. IEEE Transactions on Robotics and Automation, pp 154, 2004. PDF
• J. Minguez, J. Osuna, L. Montano. A Divide and Conquer Strategy based on Situations to Achieve Reactive Collision Avoidance in Troublesome Scenarios. IEEE International Conference on Robotics and Automation (ICRA 2004), 2004. New Orleans, USA. PDF

This driver reads pose information from a position2d device, sensor data from a laser device and/or sonar device, and writes commands to a position2d device. The two position2d devices can be the same. At least one device of type laser or sonar must be provided.

The driver itself supports the position2d interface. Send PLAYER_POSITION2D_CMD_POS commands to set the goal pose. The driver also accepts PLAYER_POSITION2D_CMD_VEL commands, simply passing them through to the underlying output device.

Compile-time dependencies

• none

Provides

• position2d

Requires

• "input" position2d : source of pose and velocity information
• "output" position2d : sink for velocity commands to control the robot
• laser : the laser to read from
• sonar : the sonar to read from

Configuration requests

• all position2d requests are passed through to the underlying "output" position2d device.

Configuration file options

• goal_tol (tuple: [length angle])
  • Default: [0.5 10.0] (m deg)
  • Respectively, translational and rotational goal tolerance. When the robot is within these bounds of the current target pose, it will be stopped.
• max_speed (tuple: [length/sec angle/sec])
  • Default: 0.3 45.0
  • Respectively, maximum absolute translational and rotational velocities to be used in commanding the robot.
• min_speed (tuple: [length/sec angle/sec])
  • Default: 0.05 10.0
  • Respectively, minimum absolute non-zero translational and rotational velocities to be used in commanding the robot.
• avoid_dist (length)
  • Default: 0.5 m
  • Distance at which obstacle avoidance begins
• safety_dist (length)
  • Default: 0.0 m
  • Extra extent added to the robot on all sides when doing obstacle avoidance.
• rotate_stuck_time (float)
  • Default: 2.0 seconds
  • How long the robot is allowed to rotate in place without making any progress toward the goal orientation before giving up.
• translate_stuck_time (float)
  • Default: 2.0 seconds
  • How long the robot is allowed to translate without making sufficient progress toward the goal position before giving up.
• translate_stuck_dist (length)
  • Default: 0.25 m
  • How far the robot must translate during translate stuck time in order to not give up.
• translate_stuck_angle (angle)
  • Default: 20 deg
  • How far the robot must rotate during translate stuck time in order to not give up.
• wait_on_stall (integer)
  • Default: 0
  • Should local navigation be paused if the stall flag is set on the input position2d device? This option is useful if the robot's pose is being read from a SLAM system that sets the stall flag when it is performing intensive computation and can no longer guarantee the validity of pose estimates.
• laser_buffer (integer)
  • Default: 10
  • How many recent laser scans to consider in the local navigation.
• sonar_buffer (integer)
  • Default: 10
  • How many recent sonar scans to consider in the local navigation
• sonar_bad_transducers (tuple [integers])
  • Default: [] (empty tuple)
  • Indices of sonar transducers that should be ignored. This option is useful when particular sonars are known to be bad, or if they tend to give returns from the robot's body (usually the wheels), or if they are just not needed because of overlap with the laser.

Example

driver
(
  name "nd"
  provides ["position2d:1"]
  requires ["output:::position2d:0" "input:::position2d:0" "laser:0" "sonar:0"]

  max_speed [0.3 30.0]
  min_speed [0.1 10.0]
  goal_tol [0.3 15.0]
  wait_on_stall 1

  rotate_stuck_time 5.0
  translate_stuck_time 5.0
  translate_stuck_dist 0.15
  translate_stuck_angle 10.0

  avoid_dist 0.4
  safety_dist 0.0

  laser_buffer 1
  sonar_buffer 1
)

Author

Javier Minguez (underlying algorithm), Brian Gerkey (driver integration)