• Udacity Nanodegree: Robotics Software Engineer
  • Concept
  • Project 01: Build My World
    • Directory Structure
    • Steps to launch the simulation
      • Step 1 Update and upgrade the Workspace image
      • Step 2 Clone the lab folder in /home/workspace/
      • Step 3 Compile the code
      • Step 4 Add the library path to the Gazebo plugin path
      • Step 5 Run the Gazebo World file
    • Output
  • Ch2 ROS Essential Lesson2
    • setup overview
    • tutlesim
    • project setup

Udacity Nanodegree: Robotics Software Engineer

Concept

video 1 concept

00:00
Robots perceive the world around them through the use of sensors.
00:04
You can think of robot sensors as analogous to
00:07
our human senses like sight, hearing, and touch.
00:12
There are many different types of sensors used in robotics.
00:16
Robots eyes might be analogous to cameras,
00:19
lidar, radar, or even ultrasound.
00:23
A microphone could be a robot's ears.
00:27
Giving a robot a sense of touch might be
00:29
achieved through the use of temperature or pressure sensors.
00:33
Even senses like taste and smell can be achieved using chemical analyzers.
00:39
Robots can also be equipped with sensors that have
00:42
no human analogue like GPS to establish exact position on earth,
00:47
a barometer to track altitude,
00:49
or even a magnetic field sensor with actinic.
00:52
In this program, you will gain experience with
00:55
a wide range of sensor modalities and sensor data.

video decision making the sensor

00:00
A robot needs to make decisions based on
00:03
the data from various sensors and its own internal state.
00:07
These decisions can be as simple as answering yes or no question.
00:12
Like is the target object present on the table?
00:15
Or the decisions can be extremely
00:17
complex like deciding how to navigate an unknown environment.
00:21
In practice however, the decision-making process in robotics can require answering
00:26
many questions to decide on one course of
00:28
action from among potentially infinite possibilities.
00:32
Along the way, sophisticated techniques might be used.
00:36
For example, special tools can extract information
00:39
from images or compensate for a measurement error.
00:43
A robot needs to using
00:44
motion planning algorithm to decide how to get from one place to another.
00:49
Then, using a control algorithm to stay on track.
00:52
In this program, we'll cover
00:54
decision-making techniques to give your robots the best brains possible.

Project 01: Build My World

Directory Structure

. Build_my_world                  # Workspace directory
├── CMakeLists.txt
├── docs                          # Results and notes
│   ├── my_world.png
│   ├── notes
│   └── with_output.png
├── LICENSE
├── model
│   ├── metal_hawk               # Model of robot
│   │   ├── model.config
│   │   └── model.sdf
│   └── my_building              # Model of environment
│       ├── model.config
│       └── model.sdf
├── README.md
├── script
│   └── welcome_message.cpp      # Gazebo World plugin C++ script
└── world
    └── my_world                 # Gazebo main World containing models

Steps to launch the simulation

Step 1 Update and upgrade the Workspace image

$ sudo apt-get update
$ sudo apt-get upgrade -y

Step 2 Clone the lab folder in /home/workspace/

$ cd /home/workspace/
$ git clone git@github.com:Suraj0712/Build_my_world.git

Step 3 Compile the code

$ cd /home/workspace/Build_my_world/
$ mkdir build
$ cd build/
$ cmake ../
$ make

Step 4 Add the library path to the Gazebo plugin path

$ export GAZEBO_PLUGIN_PATH=${GAZEBO_PLUGIN_PATH}:/home/workspace/Build_my_world/build

Step 5 Run the Gazebo World file

$ cd /home/workspace/Build_my_world/world/
$ gazebo my_world

Output

Ch2 ROS Essential Lesson2

setup overview

• Build Robots with ROS Building a robot used to be a long and cumbersome process. Essentially all of the components had to be built from scratch.

In this lesson, we’ll introduce the Robot Operating System, or “ROS”, which is a software framework that greatly simplifies robot development. There are many advantages to developing robots with ROS. Let’s start by illustrating some of its components and features.

• Components and Features ROS is an open-source software framework for robotics development. It is not an operating system in the typical sense. But like an OS, it provides a means of communicating with hardware. It also provides a way for different processes to communicate with one another via message passing. Lastly, ROS features a slick build and package management system called catkin, allowing you to develop and deploy software with ease. ROS also has tools for visualization, simulation, and analysis, as well as extensive community support and interfaces to numerous powerful software libraries.

• Summary Summary of ROS components and features:

• Open-source! Hardware abstraction of device drivers Communication via message passing Slick build and package management Tools for visualization, simulation, analysis Powerful software libraries Short Documentary Check out this awesome short documentary on ROS that Bloomberg published recently.

History Before diving deeper, let’s take a brief tour of the history of ROS.

tutlesim

More on the history of Turtles in Robotics As we mentioned in the video, William Grey Walter’s influence is still felt today. He referred to his robots as ‘turtles’ and, as you will see, the moniker stuck.

The image below is William Walter’s Elsie (the robot mentioned in the video) without her protective covering.

Long after William Walter’s work with Elmer and Elsie, Dr. Seymour Papert, a professor at MIT, began to use turtle robots for education. One of the characteristics of Papert’s robots was their ability to draw on paper.

In addition to being involved with the creation and development of MIT’s turtle robots, Dr. Papert is also known as the creator and evangelist for the educational programming language LOGO.

Despite being a general-purpose language, LOGO is known for its use of “turtle graphics”, a system that allows users to draw by sending simple commands to a robotic turtle. The robotic turtle mentioned here could be either a real turtle robot, or a virtual on-screen cursor within the LOGO programming environment.

The image below shows an example of Valiant Technology’s Turtle robot drawing on a sheet of paper.

project setup

Environment Setup Before we begin using ROS in a terminal, we must first ensure that all of the environment variables are present. To do this, we must source the setup script provided by ROS

Caveat Make sure you use the bash command source rather than ./. There’s a subtle distinction between the two commands, in that source executes the script in the current session, while ./ will start a new session, containing a copy of the current environment. When a script executed via ./ is exited, all environment variables set by it will be lost. We don’t want this. For more information on environment variables and terminal sessions, please see here.

Automatically Configuring the Environment Setting up the ROS environment every time you open a new terminal window can be painful and tedious. To avoid the tedium, we can simply add the command to source the workspace to our ~/.bashrc file. This will cause our environment to be sourced any time a new terminal session is created. Fortunately, this command has been already added for you.

• environment setup

• run tutlesim

• run commands

The following wiki, pages and posts are tagged with ros