Automatic charging behaviour

[cwrx777]

When does RMF trigger the automatic charging task?
Consider the following scenario:
A delivery job is split into multiple tasks:

1. task 1: go to pickup location
2. task 2: perform docking and pickup a cart, read RFID tag for the destination
3. task 3: go to destination and drop off
4. task 4: go back to home location.

The tasks are sent to the AMR one by one, and only the previous task is complete.
When AMR is performing task 2, the battery level does below the threshold value defined in the fleet adapter config file.
Will RMF interrupt the task (task 2) and send the AMR to charger or is it after task 3 is queued for the robot (robot_task_request) RMF sends the AMR to charger (with the cart still on top of the AMR), or any other behaviour?

[mxgrey]

First, I strongly strongly recommend not breaking apart tasks like this. The current generation of Open-RMF has a baked in assumption that each task that can be assigned to a robot is self-contained and completely independent from any other task. After a robot has completed any task it should be in a good state to perform any other task that it is qualified for (unless battery recharging is needed).

So in your example, if the fleet adapter decides that the robot is too low on battery after it performs the pickup of task 2 then it might send the robot back to its charger before it issues task 3, which means the robot will be carrying the payload back to its charger, which is almost certainly something you do not want to happen.

But even worse than that, if you are using the dispatching system then it's possible for the fleet adapter to assign these tasks out of order, e.g. assign task 3 followed by task 2 followed by task 1. Or if there's another delivery that gets broken down into multiple tasks, the fleet adapter might end up shuffling those tasks together, which will result in especially bad outcomes.

There shouldn't be any technical reason to decompose a task like this anyway. Any sequence of activities that you might want to split across multiple tasks can always be expressed as one big composed task where each of your "tasks" is put in as one "phase". Let me know if you have any specific issue with making that work.