Beluga POD

Beluga POD is a Rails-based web interface for the Beluga project developed at the Dynamical Control Systems Laboratory at Princeton University. It uses TCP sockets to connect to a Beluga IPC server (built with rhubarb). Both joystick and waypoint (point-and-move) style interfaces are provided that use AJAX to continuously update the user's view with the latest information from the tracking software while sending commands to the robots.

Adding a new interface

As an example, suppose that we want to add a new experimental interface that can be accessed at <thehost>/hitl. We'll add this task to the pages controller.

1. Add the route to config/routes.rb

   Add the following line below the match '/waypoint' => 'pages#waypoint line in config/routes.rb:

   match '/hitl' => 'pages#hitl'

   This tells Rails that whenever someone visits <thehost>/hitl, we want the application to execute the code found in the hitl action (aka function/method) in the PagesController controller.

   Optionally, if you want to disable the other interfaces, comment out the corresponding lines.

2. Add the action to PagesController

   Open up app/controllers/pages_controller.rb and add a hitl method to the PagesController class:

   class PagesController < ApplicationController
     # ...
     # existing code...
    
     # the new 'hitl' action
     def hitl
       # whatever code needs to go here
       # for example, if we need a waypoint:
       @waypoint = Waypoint.new(:id => 0, :x => 0, :y => 0, :z => 0)
     end
   end

   Take a look at the other actions to see what kind of code might need to go into this method. The basic idea is to set up any variables that you need in your view. Any instance variable (the ones with the @ in front) will be available in the view. It's entirely possible that you don't need any code at all here.

3. Set up the view

   Create a file app/views/pages/hitl.html.erb. Probably the simplest way to do this is to copy an existing view and rename the file. If you want to use custom css and/or javascript, set up the appropriate content_for blocks:

   <%= content_for :page_css do %>
     <%= stylesheet_link_tag "hitl" %>
   <% end %>
    
   <%= content_for :page_js do %>
     <%= javascript_include_tag "hitl" %>
   <% end %>

   This tells Rails to insert a css link to the file at app/assets/stylesheets/hitl.css and the javascript file at app/assets/javascripts/hitl.js. Note that this is optional and you can include multiple files here. For example, if you want to include the waypoint.js file as well, just add a duplicate javascript_include_tag line and replace hitl with waypoint.

   Note also that this is separate from using sass/scss. If you want to use scss, create a (for example) hitl.scss and then run sass hitl.scss hitl.css in the stylesheets directory. The bottom line is that rails will load the .css file - it's up to you to generate it however you want. (There are ways to automate this process, but that's beyond the scope of this note.)

That's it! You should now be able to launch the Rails server and see your new action at http://127.0.0.1:3000/hitl