System analysis of a robot car for carrying heavy loads

Hi everyone!
I’m new at capella and I’m trying to model a robot car which have the main function of transport heavy loads. The car will be controlled by an operator via remote control, which send commands to a receiver at the car, and the receiver send the commands to the control unit.
I’m a little confused about some steps of the system analysis.
I’ve set some capabilities to the car: move/manage, carry/alocate load, modify structure, provide safety.
Considering the move capability move/manage, I’ve done a SAB diagram considering the operator and the system. The system function that I considered where “modify angle of the wheels”, “accelerate”, “brake”. And the functions of the operator where “Accelerate car”, “brake car”, “change direction”.
But really don’t know if this is right, because for me this is kinda ambiguous.
Also, I’m confused if for every capacibility I need to do a Scenario diagram, or i can just do a SAB diagram and uses functional exchanges to show the relations between the functions.
Can you guys help me to clarify this ideas?
I’ve saw some examples and books aboud arcadia and capella, but the examples there did not helped me in my project context.
I started to use capella to help me and my colleagues to develop the software for the Car.


Hi Lucian,
Quick answer: your system functions looks fine. What do you find ambiguous?
You do not need a scenario diagram for all your capabilities. Capabilities are either described by scenarios or functional chains. So you may choose one or another to describe your capabilities.

I hope this helps.

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Hi @StephaneLacrampe
thanks for your answer!
The abiguosity that I talked about was in relation to the operator function (for example accelerate car) and the system function (accelerate). Do the function exchange between these two functions can be something like “send command to accelerate”, for example?

Hi Lucian,

The “send command to accelerate” sounds more a function, that is, send is an action verb followed by the object.
If you try to capture what is sent between functions, then the functional exchange should be characterised, that is for example, functional exchange “accelerate cmd”, where accelerate command may be defined as data (e.g., discrete signal) or flow (e.g., voltage).

I hope that helps,
Hélder Castro


Hi @HelderCastro , thanks for the answer!
These answers are really helping me to clarify the my modelling.
Thank you guys!

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