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