On this page I will distill my insights from taking robot lab, so that you might be able to much more quickly make your way to where I am now in terms of understanding robotics simulation. While taking robot lab I focused entirely on the simulation side of the subject.Robotics Simulators can be sepereted into two groups based on their software licence. Currently the most developed and widely used open source simulator is player/stage/gazebo.indeed in general the player/stage/gazebo software package is considered by many to be the most widely used robotics simulation software on the market. While there are other simulators available few compare.
Summary of work
I spent the first three or four weeks trying to install player, stage, and gazebo as well as looking at some of the other options available to students for simulation of robotics. Once I installed and learned to use ROS i found that it was not necessary to install player, stage, and gazebo if your going to use ros because ros will do the work for you. After I had gazebo working with ros i spent two weeks working on learning urdf to make a simulated robot and then learning xacro to make it easier to alter and add to that simulated robot. After that I spent a week trying to learn how to control a robot in gazebo through ros but my efforts did not find any results so i began learning how to do so through player. As a result of that I learned how to define a world in stage. My last task was to learn to use player to control robots.
Before you can even consider installing player/stage/gazebo, you need to install ubuntu. whether it be with or without ros, at this point it is very unlikely that you will be able to get it to work on any other operating system other than ubuntu. Luckly for you even if you have a computer running windows or mac os x, you can have a virtulization of ubuntu which will be good enough provided you are not using gazebo.
Follow the following directions to install ubuntu on a virtual machine.
- download and install the most recent version of virtual box
- Now you need to download ubuntu
- Next you need to launch virtual box and choose new to make a new virtual machine. follow the wizard as it has you set up the virtual machine. I suggest that when it is time to choose a hard drive make it dynamically allocated, as it will only gain size as it grows larger and you should give it at least 8 gb but I would suggest 20 as a perfect amount.
- After hitting create you will see a new vertual machine with the name you gave it under the new/settings/start buttons. Before you can start the machine and install ubuntu you need to have a disk available with ubuntu on it. If you are able to mount the disk without burning it then do so now. Otherwise you will need to burn it to a dvd or flash drive. After this is done and you have booted the disk, click on your virtual machine and either press the start button. Now you will see the first run wizard. You will need to choose the disk with the version of ubuntu you downloaded and press continue.
- Next you will be given the option to try ubuntu or install it to your hard drive. Choose install. Overright the harddrive as there will not be anything on it. As ubuntu installs it lets you go through the basic user setup.
- You have now installed ubuntu. Congratulations. The last thing i suggest doing right after finishing installation is to stop the virtual machine and clone your vm. There is an option to take snapshots of what you have been doing but I would rather have a full copy. This may take some time depending on the size of your vm, but it should not be more than 20 minutes at most.
Ubuntu Linux Basics
For those who have not spent much time using command line, using linux can be confusing as many functions can only be done through the command line interface. To bring up a command line prompt either press the keyboard shortcut ctrl +alt+ t. to go to a directory type cd(change directory) and the address of the folder you wish to go to. to create a new directory type mkdir directoryName to change permissions for a file type chmod u(for user. other options are g for group and o for others) + (+ adds permissions - removes) r w x(read write execute)
Player, stage, gazebo Section
Installing Player/stage/gazebo standalone
If you are going to use stage or gazebo you must first install player. Player is essentially software which allows your computer to communicate with your robot, interoperate its sensor output, and give it commands to move. When used with stage or gazebo it allows you to
Installing Player/Stage/gazebo with ros
- installing ros
Installation of ros is comparatively simple. We currently have a distribution of ros with p2os already installed but as of this writing the installation page is already out of date, so It is best that we start from the beginning.
ros installation steps
- Go to the ros installation page and choose a supported operating system.(ubuntu is the only one currently)
- follow the installation instructions, but make sure to only do the actions which are specific for the version of ubuntu you are running. For example if it says Ubuntu 11.10 (Oneiric) that is only for ubuntu 11.10 and should otherwise be disregarded.
- install player in ros
- install stage in ros
- install gazebo in ros
Defining a robot
- for Stage
- for Gazebo
- building robots with URDF
- building robots with XACRO
Programing a Robot for use with Player
Other simulators to look at
In this section I will talk briefly about three other simulators I was able to look at.
Microsoft Robotics Developer Studio
The most recent version of microsoft robotics developer studio is available from their website here.
Microsoft developers studio is not the most intuitive piece of software to install but it is possible for someone with little programming experience to use it by mastering Microsoft's visual programming language. An editor for this is provided with the software, and this allows you to program a robot in simulation or with select hardware by working through the tutorials which are here. I spent most of my time playing with the example simulations provided with the suite, which shows the potential application for the kinect fairly well. The simulation itself looks very nice but It would not be particularly useful since it did not seem to have a point cloud library or support for the pioneer robot we were using.
V-Rep is a new robotics simulation that is currently still in developement. Students and anyone interested in the software can download a demo version which only disables the save function here
V-rep is a Virtual Robot Experimentation platform which provides a wide variety of features which I thought was most impressive. The features are described here. I thought of the most interesting to a student is that you can build the robot in the editor out of primitive shapes and then program the robot in the main editor through the lua scripting language.
In addition to being able to create your own robot in the simulator cad models can be loaded of robots, which clearly provides a level of accuracy that is missing in other simulators. V-rep includes a verity of robot models as well as other objects. All objects in v-rep are added the simulation by dragging and dropping from a list of objects.
The simulation comes with both mobile and fixed robots, so it can be used for a wider range of simulations, particularly since it has a wide range of physics interactions supported. Your robots actions can be programmed entirely within the simulator using a scripting language called lua and the built in api provides a large verity of functions including provides path planning. It has a wide verity of supported sensors and importantly has built in recording and monitoring of sensor data. Lastly v-rep application itself can be customized by either writing a custom main client application or by writing plugins.
Overall I would say the level of user friendly interaction combined with a fairly fully featured robotics simulation environment makes V-rep a very compelling choice of simulation particularly as a student who can easily be bogged down by dealing with getting the simulator installed and working.
Webots can be found here
Webots is the third simulation software I looked at and the one i spent the least amount of time looking at. With only a few mintues use I discovered that it does have some interesting advantages over player/stage/gazebo and microsoft developer studio in that the entire simulation and coding environment are integrated into a single piece of software. While for research purposes this might not be as signficiant as a student learning to program robots has been much harder to begin as one has to master the installation of the software and creating worlds before you can even consider learning to get a robot to do something. Webots allows the user to skip the more time intensive steps and get to learning to program a robot. I did not orginally look at the demo of webots until a week ago as it limits the user to two environments and does not allow the user to save. More importantly the price for the educational edition is $320 which would be fine for a class using it but not as such for a individual student to purchase.