Linorobot

[Lutgarda Briseno]

Ihave been recently developing a similar robot - the LoCoRo (low cost robot) project. I am using a Raspberry Pi 3 as the computer (others could be substituted). Similar to your Linorobot, the foundation is PWM motor drive and motor controllers. (The use of ESCs allow for high current motors). It too supports 2WD (akerman and differential drive) and 4WD (differential and Mecanum drive). (The mecanum drive currently used 3D printed wheels which I plan to open source soon). I am only at the teleop phase of development. I will read about your work to help with ideas for developing autonomous capabilities.

I choose the RPi for its ubiquity and with the expectation it will have more than enough CPU to handle computer vision (which I am learning is suboptimal). I only recently started to consider other proximity sensors for mapping.

Hi , This is Hemsingh, Its done wonderfully well by you. I appreciate ur hard work. But i have a doubt , How the localization can be achieved on linorobot2. amcl pose array particle cloud is not coming to fill and localize the bot. Im ready to donate if localization is done with linorobot (nav2).

A little research on the IoT determined that there is no ROS Kinetic available for the MATE version of Ubuntu! However Melodic, the latest version of ROS, is available for Ubuntu MATE and can be installed as the full desktop package. Since the ROS Melodic full desktop package is quite large, I recommend using a 64GB micro SD card, but remember you must reformat the micro SD card to FAT32 from exFAT before installing Ubuntu MATE.

Once you have burned the Ubuntu MATE image to your micro SD card, insert it into your Rpi 3B+ and apply power. When the Ubuntu OS has booted up, follow the on screen instructions until you have just the desktop displayed.

Then you are going to want to create a Virtual Network Connection (VNC) with your Ubuntu OS. I followed these instructions to create and install tightvncserver on the Ubuntu MATE. However I found that if you are going to want to use the ROS Visualizer (rviz) tightvncserver does not support Xserver or OpenGL which rviz requires.

I presently have the Tigervnc server working on my Ubuntu Mate OS and it definitely does support Xserver and OpenGL however it has the same problem as the tightvnc server in that it does not allow copy and paste into the Ubuntu Mate desktop terminal window so I will have to see how to correct that issue.

Eventually there will be Ubuntu and ROS software versions that will run on the Rpi 4B+ which is available with 1GB, 2GB, or 4GB of RAM and on a bigger robot chassis power consumption becomes a moot point as the chassis can carry bigger batteries like Li Ion.

I only plan to take this thread to point of getting a successful Ubuntu Mate/ROS Melodic combination up and running on a Rpi 3B+ as Ubuntu Mate/ROS Melodic are really not germane to the GoPiGo2/R4R operating environment at the moment.

The only problem I have encountered with this Ubuntu Mate 18.04/ROS Melodic combination is that I cannot copy and paste into any of VNC desktop windows include Mate Terminal. I have tried two different VNC Viewers (RealVNC and TigerVNC) and they both exhibit the same issue. I have also tried a number of different VNC servers (tightvnc, x11vnc, tigervnc, etc) on the Ubuntu Mate and either they allowed copy and past on the VNC Viewer desktop windows, but did not support the ROS Visualizer (rviz) and vice versa.

Right now I am using either RealVNC or TigerVNC as Viewer Clients and Tigervnc server as the server on the Ubuntu Mate OS. This combination has allowed me to run the RPLidar on the Rpi 3B+ (as setup in this DI Project link) and actually launch rviz to view a 2D real time display of the RPLidar scanning my dinning room.

As for the linorobot project, you linked to above, the main issue is that some of the present linorobot ROS packages are not supported by ROS Melodic and only by ROS Kinetic and there still are some minor issues. However the linorobot project does not require the ROS Kinetic desktop as it does not use the ROS Visualizer (rviz).

The fallback is to run Ubuntu Mate 16.0.4 and ROS Kinetic-Base (ROS Kinetic will not install on Ubuntu Mate 18.0.4) which to me is retrogressing, but that is the only way to get my larger than GoPiGo3 chassis running. ROS Kinetic-Base is readily available, but Ubuntu Mate 16.0.4 is tough to come by and I had to really search around on the IoT to locate an image copy.

Update: Turns out that the Ubuntu Mate 16.0.4 I downloaded will not boot on my Rpi 3B+. But not to worry as linorobot has created a modified linorobot installer app that ignores the two missing packages in ROS Melodic, which can be built from the source and installed later, after the linorobot installation has completed.

The ROS Visularizer display looked just like the one in the DI RPLidar Project, mentioned above, except that the scanner outline was that of my dinning room. While it was scanning, if someone walked by the scanner, you could see the dot outline ripple along as the person walked by.

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