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Sensor Sim: readme.md

Project Description

This package implements basic sensor models for an underwater/surface vehicles. It has the following features - Simulate GPS, Depth, DVL (Bottom Track and Water Track), Altitude, AHRS, Ranges - Control Gaussian Noise and Measurement Noise - Control Sensor Publish Frequency - Publish State output of the dynamic model in auv_msgs::NavigationStatus format

Getting Started

Installation

Pkg sensor_sim comes as part of the medusa_vx stack.

Configuration

This section explains how to write the node configuration file. Sample are given below

topics:
  subscribers: [ "/dynamics_sim/position"]
  publishers : [
    "/measurement/position",
    "/measurement/velocity",
    "/measurement/orientation",
    "/sensors/gnss",
    "/sensors/range",
    "/sim/dynamics/model",
    "/diagnostics/thrusterStatus"
  ]
water_column: 100
sensors:
  - type     : "GNSS"
    frame_id : "gnss"
    frequency: 1.0
    count    : 500
    noise    : 0.0
    variance : 0.03
    debug    : false
  - type     : "DVL_BT"
    frame_id : "dvl_bt"
    frequency: 5.0
    noise    : 0.015
    variance : 0.001
    altitude : 30.0
    debug    : true
  - type     : "DVL_WT"
    frame_id : "dvl_wt"
    frequency: 5.0
    noise    : 0.01
    variance : 0.0
    altitude : 110.0
  - type     : "AHRS"
    frame_id : "ahrs"
    frequency: 10.0
    noise    : [0, 0]
    variance : 0.000001
  - type     : "DEPTH"
    frame_id : "depth"
    frequency: 10.0
    noise    : 0.01
    variance : 0.005
  - type     : "ALTIMETER"
    frame_id : "altimeter"
    frequency: 5.0
    noise    : 0.1
    variance : 0.1
  - type     : "MODEL"
    frequency: 10.0

  1. topics/publishers: parameter of type string[7]

  2. Defines the output topics - [position, velocity, orientation, gnss, range, model, thruster]

  3. position topic is used to publish DEPTH & ALTIMETER measurements of type medusa_msgs::Measurement
  4. velocity topic is used to publish DVL_BT, DVL_WT measurements of type medusa_msgs::Measurement
  5. orientation topic is used to publish AHRS measurements of type medusa_msgs::Measurement
  6. gnss topic is used for GNSS measurements in WGS84 of type sensor_msgs::NavSatFix

  7. range topic is used for single beacon measurements of type medusa_msgs::mUSBLFix

  8. topics/subscribers: parameter of type string[1]

  9. position topic to receive the dynamic state of the vehicle in nav_msgs::Odometry

  10. water_column: Length of water column (We assume that water column is constant)

sensors: Sensors to be simulated are described as a list of type . Any number of sensors may be defined following the format described below.

  1. type: parameter of type string

  2. Defines the type of sensor to be simulated. Current available sensors are "GNSS", "DVL_WT", "DVL_BT", "AHRS", "DEPTH", "ALTIMETER", "RANGE", "MODEL"

  3. frame_id: parameter of type string

  4. Frame id of the simulated sensor, must be unique

  5. frequency: parameter of type double

  6. Controls how often the sensor publishes data

  7. count: parameter of type int

  8. Sensor stops publishing after this many outputs

  9. Put 0 for infinite

  10. noise: parameter of type double

  11. gaussian noise added to the sensor

  12. variance: parameter of type double

  13. In addition to the gaussian noise, a constant value is added while publishing the sensor value and variance.

  14. Its main purpose is to easily tune the measurement noise being fed to the filter
  15. This value has no effect while adding noise to the sensor!

Launching the Node

An example launch file is provided below where sensor_sim/sensor_sim.

<?xml version="1.0"?>
<launch>
    <arg name="name" default="myellow"/>
    <node pkg="sensor_sim" type="sensor_sim" name="sensor_sim" respawn="false" output="screen">
        <rosparam command="load" file="$(find sensor_sim)/config/sensors.yaml"/>
    </node>
</launch>
Last update: May 30, 2022
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