3d simulation in ros

Intro Gazebo Gazebo in ROS Examples

3D Simulation in ROS

Mihai Emanuel Dolha

Intelligent Autonomous SystemsTechnische Universität München

November 4, 2010

November 4, 2010

3D Simulation Mihai Emanuel Dolha


Outline

1. Introduction

2. Gazebo

3. Gazebo in ROS

4. Examples

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Why do we use simulators? (1/2)

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Why do we use simulators?(2/2)

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3D Simulator Components

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Outline

1. Introduction

2. Gazebo

3. Gazebo in ROS

4. Examples

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Gazebo

I 3D multi robot simulator with dynamicsI part of the Player/Stage project

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Physics Engine(s)

I currently supported: ODE, Bullet

I rigid body dynamicsI based on Newton’s second law:

~F = m~aI constraint formulationI collision detectionI accelerations, velocities and

poses

November 4, 2010



Physics Engine(s)

I currently supported: ODE, BulletI rigid body dynamics

I based on Newton’s second law:~F = m~a

I constraint formulationI collision detectionI accelerations, velocities and

poses

November 4, 2010



Physics Engine(s)

I currently supported: ODE, BulletI rigid body dynamicsI based on Newton’s second law:

~F = m~a

I constraint formulationI collision detectionI accelerations, velocities and

poses

November 4, 2010



Physics Engine(s)


~F = m~aI constraint formulation

I collision detectionI accelerations, velocities and

poses

November 4, 2010



Physics Engine(s)


~F = m~aI constraint formulationI collision detection

I accelerations, velocities andposes

November 4, 2010



Physics Engine(s)


~F = m~aI constraint formulationI collision detectionI accelerations, velocities and

poses

November 4, 2010



Physics Engine(s)

I ConstraintsI jointsI contacts

I Collision detectionI continuous or discreteI broad phase and narrow phase

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Rendering Engine

Ogre3DI Object-Oriented Graphics

Rendering EngineI based on OpenGL

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Modelling in Gazebo

Gazebo modelI other modelsI bodies

I pose,massI geometries

I collision shapeI visual shape

I sensorsI jointsI controllers

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Sensors in Gazebo

Laser sensorsI provided by physics

engineI raycastingI zero sweeping

durationI noise freeI real world data is

much more cluttered

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Sensors in Gazebo

CamerasI provided by

rendering engineI ideal pinhole

camerasI noise free and in

focusI no calibration

neededI real world like

texturing, shadingand lighting requireeffort

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Modeling in Gazebo

World files

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Communication in Gazebo

Controllers and interfaces

I clients write commands on interfacesI controllers get commands from interfacesI commands are processed, then applied to simulated modelI current model status and results are send to client

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Controllers and interfacesI clients write commands on interfaces

I controllers get commands from interfacesI commands are processed, then applied to simulated modelI current model status and results are send to client

November 4, 2010




Controllers and interfacesI clients write commands on interfacesI controllers get commands from interfaces

I commands are processed, then applied to simulated modelI current model status and results are send to client

November 4, 2010




Controllers and interfacesI clients write commands on interfacesI controllers get commands from interfacesI commands are processed, then applied to simulated model

I current model status and results are send to client

November 4, 2010




Controllers and interfacesI clients write commands on interfacesI controllers get commands from interfacesI commands are processed, then applied to simulated modelI current model status and results are send to client

November 4, 2010



Outline

1. Introduction

2. Gazebo

3. Gazebo in ROS

4. Examples

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Overview

I stack:simulator_gazebo

I actively maintainedand developed

I improved modelingmechanism

I integrated in theROS comunicationmechanisms

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Modeling using URDF

I URDF Description:

< robot name=" t e s t _ r o b o t ">< l i n k name=" l i n k 1 " / >< l i n k name=" l i n k 2 " / >< l i n k name=" l i n k 3 " / >< l i n k name=" l i n k 4 " / >

< j o i n t name=" j o i n t 1 " type="cont inuous ">

<parent l i n k =" l i n k 1 " / >< c h i l d l i n k =" l i n k 2 " / >

< / j o i n t >



< / j o i n t >



< / j o i n t >< / robot>

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Modeling

I Gazebo URDF extension

<gazebo re ference=" f i nge r_ t i p_camera_ l i nk "><sensor:camera name=" f inger_t ip_camera_sensor ">

<imageSize>640 480< / imageSize><imageFormat>L8< / imageFormat><hfov>90< / hfov><nearCl ip>0.01< / nearCl ip>< f a r C l i p >100< / f a r C l i p ><updateRate>20.0< / updateRate><con t ro l l e r : r os_camera name=" f i n g e r _ t i p _ c a m e r a _ c o n t r o l l e r " p lug in ="

l ibros_camera . so "><alwaysOn> t rue < / alwaysOn><updateRate>20.0< / updateRate><topicName>f inger_ t ip_cam / image< / topicName><frameName> f i nge r_ t i p_camera_ l i nk < / frameName>< in te r face :camera name=" f i nge r_ t i p_camera_ i face " / >

< / con t ro l l e r : r os_camera >< / sensor:camera>< t u r n G r a v i t y O f f > t rue < / t u r n G r a v i t y O f f >< ma te r i a l >PR2/ Blue< / ma te r i a l >

< / gazebo>

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Modeling

I Loading a URDF model in Gazebo

<launch>

< !−− send pr2 u rd f to param server −−><param name=" r o b o t _ d e s c r i p t i o n " command=" $( f i n d xacro ) / xacro . py ’ $ ( f i n d

p r2_desc r i p t i on ) / robots / pr2 . u rd f . xacro ’ " / >

< !−− push r o b o t _ d e s c r i p t i o n to f a c t o r y and spawn robot i n gazebo −−><node name=" pr2_gazebo_model " pkg=" gazebo " type=" spawn_model " args=" $( optenv

ROBOT_INITIAL_POSE) −unpause −u rd f −param r o b o t _ d e s c r i p t i o n −model pr2 "respawn=" f a l s e " output= " screen " / >

< / launch>

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Communication & Control

I robot description on parameter serverI the controller manager:

I loads controllersI creates a robot state object

I client nodes publish their commands on topicsI controllers read the topics, process the command and

push it to the robot stateI the controller manager gets the commands from the robot

state and sends them to the hardware or to the simulatedmodel

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I robot description on parameter server

I the controller manager:I loads controllersI creates a robot state object




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I loads controllers

I creates a robot state objectI client nodes publish their commands on topicsI controllers read the topics, process the command and



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November 4, 2010






I client nodes publish their commands on topics

I controllers read the topics, process the command andpush it to the robot state

I the controller manager gets the commands from the robotstate and sends them to the hardware or to the simulatedmodel

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push it to the robot state

I the controller manager gets the commands from the robotstate and sends them to the hardware or to the simulatedmodel

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I pr2_teleop publishes commands on topic(/base_contrller/command)

I base_controller computes commands for each wheel andupdates the commands on the robot state

I the gazebo_ros_controller_manager checks the robotstate for commands and sends them to the joints of thesimulated model

I for controlling the real hardware: pr2_controller_managerI real world / simulator switching is done by the env. var.

ROBOT

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Outline

1. Introduction

2. Gazebo

3. Gazebo in ROS

4. Examples

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The PR2 pluging in

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Naive physics simulation

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Human character simulation

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Thank you

Questions?

November 4, 2010


3d simulation in ros

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