configuring-loopback-sim.rst

Loopback Simulator

Source code on Github.

The nav2_loopback_sim is a stand-alone simulator to create a "loopback" for non-physical simulation to replace robot hardware, physics simulators (Gazebo, Bullet, Isaac Sim, etc). It computes the robot's odometry based on the command velocity's output request to create a perfect 'frictionless plane'-style simulation for unit testing, system testing, R&D on higher level systems, testing behaviors without concerning yourself with localization accuracy or system dynamics, and multirobot simulations.

Parameters

update_duration:	Type Default double 0.01 Description The duration between updates (s)
base_frame_id:	Type Default string "base_link" Description The base frame to use.
odom_frame_id:	Type Default string "odom" Description The odom frame to use.
map_frame_id:	Type Default string "map" Description The map frame to use.
scan_frame_id:	Type Default string "base_scan" Description The scan frame to use to publish a scan
enable_stamped_cmd_vel:	Type Default string True Description Whether cmd_vel is stamped or unstamped (i.e. Twist or TwistStamped). Note: This parameter is default false in Jazzy or older! Kilted or newer uses TwistStamped by default.
scan_publish_dur:	Type Default double 0.1 Description The duration between publishing scan (in sec)
odom_publish_dur:	Type Default double <update_duration> Description The duration between publishing odometry (in sec). Defaults to update_duration.
publish_map_odom_tf:	Type Default bool true Description Whether or not to publish tf from map_frame_id to odom_frame_id
publish_scan:	Type Default bool true Description Whether or not to publish a fake laser scan.
publish_clock:	Type Default bool true Description Whether or not to publish simulated clock to /clock
speed_factor:	Type Default double 1.0 Description Speed factor for the simulated clock, e.g. 2.0 runs simulation at 2x wall time. Only used when publish_clock is true. Dynamically reconfigurable.
scan_range_min:	Type Default double 0.05 Description Minimum measurable distance from the scan in meters. Values below this are considered invalid.
scan_range_max:	Type Default double 30.0 Description Maximum measurable distance from the scan in meters. Values beyond this are out of range.
scan_angle_min:	Type Default double -3.14 Description Starting angle of the scan in radians (leftmost angle)
scan_angle_max:	Type Default double 3.14 Description Ending angle of the scan in radians (rightmost angle)
scan_angle_increment:	Type Default double 0.0261 Description Angular resolution of the scan in radians (angle between consecutive measurements)
scan_use_inf:	Type Default bool true Description Whether to use inf for out-of-range values. If false, values are set to scan_range_max - 0.1 instead.
scan_noise_std:	Type Default double 0.01 Description Standard deviation of Gaussian noise added to scan ranges (in meters).

Example

loopback_simulator:
  ros__parameters:
    base_frame_id: "base_footprint"
    odom_frame_id: "odom"
    map_frame_id: "map"
    scan_frame_id: "base_scan"  # tb4_loopback_simulator.launch.py remaps to 'rplidar_link'
    update_duration: 0.02
    publish_scan: true
    publish_clock: true
    speed_factor: 1.0
    scan_range_min: 0.05
    scan_range_max: 30.0
    scan_angle_min: -3.1415
    scan_angle_max: 3.1415
    scan_angle_increment: 0.02617
    scan_use_inf: true
    scan_noise_std: 0.01