Towards the autonomous navigation of intelligent robots for risky interventions

_Daniela Doroftei

Royal Military SchoolAv. De la Renaissance 30, B1000 Brussels,

Belgium

[email protected]

Contribution to ViewFinder – WP2

mailto:[email protected]

The goal of this research project is to prepare the RobuDem robot for an outdoor crisis management task.

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To achieve this goal, the robot must be able to: Be tele-operated by a remote user Ensure its own safety by avoiding obstacles

detected by its sensors (sonar, stereo, …) Navigate autonomously in an unknown

environment by mapping the surroundings Detect chemical contamination Navigate to pre-defined goal positions Execute complex tasks like searching for human

victims Here we will focus on the design of the

control architecture for such a robot3

RobuDem-platform: Outdoor all-terrain robot 4 driving / steering wheels allowing for

different drive modes Supports heavy loads (up to 300kg)

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Ultrasound Sensors for obstacle detection

Joystick for remote control

Chemical sensor with integrated temperature sensor

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Differential GPS (and wheel encoders) for positioning

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Quad-cam vision system consisting of a Bumble-bee stereo vision system and 2 digital cameras.

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SteerSteerRobudemRobudem

SensorsSensors

BehaviorBehaviorProcessorsProcessors

VisualVisualProcessorsProcessors

Positioning Positioning & Mapping& Mapping

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JoystickJoystick

Transmission of joystick commands to the robot:

FilterFilterCommandsCommands

Transmission of filtered commands to the robot:

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JoystickJoystick


ObeyObeyJoystickJoystick

BehaviorBehaviorControllerController

In semi-autonomous control, there is no longer a direct link between joystick and robot actuators:

Instead, there is a Behavior-Based Controller managing the commands sent to the robot

The “Obey Joystick” behavior is only 1 of the multiple behaviors contributing to the global robot control strategy 10

These commands are fused by a behavior-based controller, taking into account both behaviors to come to a globally optimal and consistent command to be sent to the robot

The joystick returns the user commands, telling the robot where to go.

The “ObeyJoystick” behavior calculates the best action to perform in order to follow the users’ commands.


The on-board sonars deliver information about obstacles in the robots’ path.

The “AvoidObstaclesUsingSonar” behavior calculates the best action to perform in order not to bump into the detected obstacles.



FuseFuseBehaviorsBehaviors

AvoidObstaclesAvoidObstaclesUsingSonarUsingSonar

SonarSonarJoystickJoystick

These commands are filtered and sent to the robot

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General requirements: The robot needs accurate positioning The robot needs to build up a model (map) of its

environment to reason with this data

Robot Safety: The robot needs to avoid areas with excessive heat The robot needs to detect chemicals and avoid

areas which are too contaminated The robot needs to detect obstacles using its sonar

sensors and its stereo vision system and avoid these obstacles

The robot needs to avoid all previously detected obstacles stored in the environmental model (map)

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Robot Goals: The robot must be tele-operable The robot needs to detect chemicals and find the

source of contamination The robot should maximize the knowledge about

the environment it is put in. The robot needs to search for human victims on

the disaster site The robot needs to be able to execute a user-

defined trajectory, given through a set of waypoints

In the event of a loss of network connection, the robot should be able to return to the base station13

These 2 positioning estimates are fused a first time to come to a more accurate and robust position estimate

A Visual Simultaneous Localization and Mapping module analyses all this input data. It builds up an environmental model (map) and places the robot accurately on this map.

Data from the rotation of the wheels, measured by wheel encoders, is used to estimate the position

VisualVisualSLAMSLAM

CameraCameraFramegrabberFramegrabber

GISMapGISMapGPSGPSOdometryOdometry

PositionPositionEstimationEstimation

A real-time differential GPS system provides absolute positioning data by acquiring signals from at least 4 space-based satellites

If available, GIS (Geographic Information System) data is used to initialize the maps

The environ-ment is observedby a camera, which detects and tracks features in the environment to estimate the robot motion and to update the map

Environmental model 6-dimensional position estimate

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A Visual SLAM module delivers robot position and a map

A chemical sensor instantaneously measures contaminant concentrations

A temperature sensor measures the temperature

This data is used to build up 2 maps containing the chemical and heat distribution

Using this map, 2 behaviors “AvoidChemicals” and “AvoidHotZones” try to steer the robot away from danger zones


AvoidAvoidChemicalsChemicals

AvoidAvoidHotZonesHotZones

LocalLocalHeatMapHeatMap

ChemicalChemicalSensorSensor

Tempe-Tempe-raturerature

LocalLocalChemicalMapChemicalMap

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The robot is controlled using a behavior-based controller which sends steering commands.

To generate these commands, the controller aims to fuse a number of objectives / tasks / requirements:

General requirements: The robot needs accurate positioning The robot needs to build up a model (map) of its

environment to reason with this data




GISMapGISMap

GPSGPS

OdometryOdometry




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Robot Safety: The robot needs to avoid areas with excessive

heat The robot needs to detect chemicals and avoid

areas which are too contaminated






AvoidAvoidChemicalsChemicals AvoidAvoid

HotZonesHotZones





GISMapGISMap

GPSGPS

OdometryOdometry


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Robot Safety: The robot needs to avoid all previously detected

obstacles stored in the environmental model (map)







HotZonesHotZones





GISMapGISMap

GPSGPS

OdometryOdometry


AvoidObstaclesAvoidObstaclesUsingSLAMUsingSLAM

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Robot Safety: The robot needs to

detect obstacles using its sonar sensors and avoid these obstacles







HotZonesHotZones





GISMapGISMap

GPSGPS

OdometryOdometry



AvoidObstaclesAvoidObstaclesUsingSonarUsingSonar SonarSonar

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Robot Safety: The robot needs

to detect obstacles using its stereo vision system and avoid these obstacles







HotZonesHotZones





GISMapGISMap

GPSGPS

OdometryOdometry



AvoidObstaclesAvoidObstaclesUsingSonarUsingSonar SonarSonarAvoidObstaclesAvoidObstacles

UsingStereoUsingStereo

StereoStereoFramegrabberFramegrabber

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HotZonesHotZones





GISMapGISMap

GPSGPS

OdometryOdometry







JoystickJoystick

Robot Goals: The robot must be

tele-operable

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HotZonesHotZones





GISMapGISMap

GPSGPS

OdometryOdometry







JoystickJoystick

GoToGoToChemicalsChemicals

Robot Goals: The robot needs to

detect chemicals and find the source of contamination

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HotZonesHotZones





GISMapGISMap

GPSGPS

OdometryOdometry







JoystickJoystick


Robot Goals: The robot should

maximize the knowledge about the environment it is put in

MaximizeMaximizeTerrainKnowledgeTerrainKnowledge

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Humans are searched for in each of the 4 camera images

A “Search Humans” behavior directs the robot in the persons’ direction







HotZonesHotZones





GISMapGISMap

GPSGPS

OdometryOdometry







JoystickJoystick


Robot Goals: The robot needs to

search for human victims


PersonPersonDetectorDetector





SearchSearchHumansHumans

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HotZonesHotZones





GISMapGISMap

GPSGPS

OdometryOdometry







JoystickJoystick









GoToGoToGoalsGoals

GlobalGlobalPathPlannerPathPlanner

GoalGoalAssignerAssigner

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HotZonesHotZones





GISMapGISMap

GPSGPS

OdometryOdometry







JoystickJoystick









GoToGoToGoalsGoals



ReturnReturnToBaseToBase

ConnectionConnectionCheckerChecker

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HotZonesHotZones





GISMapGISMap

GPSGPS

OdometryOdometry







JoystickJoystick









GoToGoToGoalsGoals





TaskTaskAssignerAssigner

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AvoidObstaclesAvoidObstaclesUsingSonarUsingSonarAvoidObstaclesAvoidObstacles





HotZonesHotZones

GoToGoToGoalsGoals



GlobalGlobalPathPlannerPathPlannerLocalLocal

HeatMapHeatMap









SonarSonar

JoystickJoystick



GISMapGISMap

GPSGPS

OdometryOdometry




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Using this modular behavior based control framework the robot can: Be tele-operated by a remote user Ensure its own safety by avoiding obstacles

detected by its sensors (sonar, stereo, …) Navigate autonomously in an unknown

environment by mapping the surroundings Detect chemical contamination Navigate to pre-defined goal positions Execute complex tasks like searching for human

victims

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AvoidObstaclesAvoidObstaclesUsingSonarUsingSonarAvoidObstaclesAvoidObstacles





HotZonesHotZones

GoToGoToGoalsGoals



GlobalGlobalPathPlannerPathPlannerLocalLocal

HeatMapHeatMap









SonarSonar

JoystickJoystick



GISMapGISMap

GPSGPS

OdometryOdometry




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Documents

Towards the autonomous navigation of intelligent robots for risky interventions