If I understand what you are asking correctly.
You need to set the msg.topic after each of these nodes. Add change nodes after each and set msg.topic to robo , sensor and switch. This will allow the join node to join the incoming payloads.
I do not use IObroker so what the input of those nodes are I have no idea , can you provide debug output info, set the debug nodes to show the complete message objects. Use the copy value option in the debug nodes to copy the msg object and post here.
help full info follows
There’s a great page in the docs (Working with messages : Node-RED) that will explain how to use the debug panel to find the right path/value for any data item.
Pay particular attention to the part about the buttons that appear under your mouse pointer when you over hover a debug message property in the sidebar.
In order to make code readable and usable it is necessary to surround your code with three backticks (also known as a left quote or backquote ```)
```
code goes here
```
You can edit and correct your post by clicking the pencil 
icon.
See this post for more details - How to share code or flow json
