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VPN-based instance with ROS and Brunel Hand

Summary

In this tutorial, you are shown how to instantiate a workspace that has a Brunel Hand and that is accessed over VPN. If you want to see an example video that you can reproduce, skip to the section Commanding motion.

If you think that something is missing, or if you find errors, please contact us or open a ticket.

Searching

To begin, sign-in to https://rerobots.net, and go to to the search page. It should look like the following:

screenshot of the search page

For this tutorial, we want to use a workspace deployment that has the type fixed_brunelhand. If one is not already listed, enter "brunel" into the search field, or try the following URL: https://rerobots.net/search?q=fixed_brunelhand

Click on the photo or the "deployment id" of one of the items in the search results. You will get a brief description of the workspace, which should look like the following:

screenshot of the workspace deployment summary

Requesting an instance

To request to use the workspace deployment that you are viewing, click the "request instance" button. The next page provides some choices about the instance that you will create. It should look like:

screenshot of the page to create a new instance

Under "kind of connection", select "VPN". Then, request it. A reservation system is under development, so your request might be denied if someone else started to use the same workspace. If you encounter difficulty here, please contact us.

If your request is accepted, then you will be redirected to a page that shows all of your active instances. Notice that there is a message at the top of the page:

Your new workspace instance is initializing! Because you did not use an SSH key that is already associated with your user account, a new key pair was generated for this instance. The following link can be used to download the private key precisely once.

When you are ready, select the link "Download private key.", which will download a file named key.pem. Be careful to only click the link when you are ready for the download.

In the table of your instances, you will find the one that you just created. Its status should be INIT, which indicates that it is initializing. If you select it, then details will be shown that look like the following:

status text of an initializing instance

Creating a new VPN server for your instance can require up to 12 minutes, more or less, because the certificate and key generation process is slow. Thus, consider taking a break for 10 minutes before clicking the refresh button. Eventually, the outcome should be READY or INIT_FAIL. If you get INIT_FAIL, then something broke during initialization. In this case, you can terminate the instance and repeat early steps of this tutorial, or contact us for help. Thanks for your patience as we try to make the rerobots service more robust.

If you get READY, then the workspace instance is ready for you!

Your first log-in

Now that the workspace instance has the status of READY, find the section "VPN" on the page and click the "add new client" button. The response might be slow (approx. 10 seconds). When completed, there will be a new entry in the list of "client identifiers" with a "one-time download" link. Like the URL for your SSH key, this can be used precisely once. When ready, select "one-time download" to get an OVPN file. If something goes wrong, then try "add new client" again. (You can generate VPN credentials for as many clients as you want.)

status text of ready instance

Import the OVPN file into your VPN client software. It contains client credentials with which you can connect to the VPN of your instance, namely, a CA certificate, a user certificate, and a user private key, along with VPN server details. The details depend on your computer. If you have Mac OS, try Tunnelblick. If you have Fedora or Ubuntu, then your network control panel should have an option to connect to a VPN. Besides these graphical tools, you can use the openvpn command-line program. On Linux, the command would be like: openvpn client.ovpn.

In many cases, the default configuration is to route all network traffic through the VPN of your instance. If you only want to route packets through it that involve VPN-specific hosts, then you might need to take some additional action that depends on your client software. For example, in the GNOME network configuration tool on Fedora, there is tab for "IPv4" in the "Add VPN" dialog, where you can check a box next to "Use this connection only for resources on its network".

When connected to the VPN, open a terminal, and try

ping rrc.local

Possibly after some delay, you should get successful pings. rrc.local is the one and only Linux host that is part of your instance of the fixed_brunelhand workspace type.

Recall earlier in the tutorial that you downloaded key.pem, which you must use to connect via SSH. As a security precaution, permissions on the file must prevent other users from reading it. Assuming that you moved key.pem into the directory where you have a terminal, try

chmod 600 key.pem

Now, start a SSH session using this key,

ssh -i key.pem [email protected]

Note that in your instance, you have the root account. There is no need to use sudo, so be careful. (You can create a new user account if you want.)

Installing the Brunel Hand CLI tool

Now we can install a small command-line program for the Brunel hand. To do so, enter the following to get necessary packages:

apt-get update
apt-get -y install python3 python3-virtualenv
python3 -m virtualenv -p python3 PY
source PY/bin/activate
pip install bhand

At the end of the above sequence, your instance will have installed the bhand tool, which we will use to command motions. Check that it is installed and that the Brunel Hand hardware is operational:

bhand

The output should be similar to the following:

Printing diagnostics. (Try `-h` for help.)

#
 System Diagnostics
____________________________

FW: Beetroot V1.01
Board:  Chestnut
Hand:   Right
OnTime: 00:00:01:77
CPU Temp:   26.61'C
IMU Temp:   29.31'C
Errors: No Errors
Mode:   None
Motors: DISABLED

ROS streaming of webcams

To visualize the space, we will start ROS nodes that stream images from the webcams. The instance already has the "desktop" installation of ROS Kinetic, but for this tutorial, the following packages must also be installed: cv_camera and web_video_server. To do so,

apt-get -y install ros-kinetic-cv-camera ros-kinetic-web-video-server

In this tutorial, the declaration of ROS nodes is through a roslaunch file. Create a text file on your computer called demo.launch and place the following in it:

<launch>
  <node name="video0" pkg="cv_camera" type="cv_camera_node">
<param name="device_id" value="0" />
  </node>
  <node name="video1" pkg="cv_camera" type="cv_camera_node">
<param name="device_id" value="1" />
  </node>
  <node name="webstreamer" pkg="web_video_server" type="web_video_server">
<param name="address" value="0.0.0.0" />
<param name="port" value="8080" />
<param name="ros_threads" value="2" />
  </node>
</launch>

Save it, and copy it into the instance host:

scp -i key.pem demo.launch [email protected]:/root/

Start an SSH session with rrc.local again, and enter

roslaunch demo.launch

Then, direct your Web browser at http://rrc.local:8080. The video streams listed are coming from the web_video_server ROS node.

Commanding motion

Start another SSH session (something like ssh -i key.pem [email protected]) and

source PY/bin/activate
bhand --raw A3

which should end with a confirmation like

Motors ENABLED

You can now send motion commands. For example,

bhand --raw G0

will cause a fist to form. Send the same command again to toggle between "open" and "close":

bhand --raw G0
bhand --raw G0

and watch the video stream in your Web browser. Depending on the speed of your Internet connection, there might be some delay in the video. If the video has extreme lag, hit the refresh button.

example video sequence showing the hand move

A brief help message for the CLI program bhand can be obtained by

bhand --help

and to get a help message from the firmware, try

bhand --fw-help

or, equivalently, bhand --raw \?. Technical specifications are available from the Brunel Hand product page by Open Bionics.

Conclusion

When you are done, return to https://rerobots.net/instances, find the instance that you created in the table, and push the terminate button.