Electronic project for a beginner.

Hello everybody, 

I'm a final year student in mechanical engineering. As part of my studies I chose to design an electronic device to improve welding processes.

to make it simple here is what I have to do:

We have a machine that holds a tube and rotate it at an adjustable speed. the issue is that we don't know the rotationnal velocity nor the tangential velocity at the surface of the tube (and we want to know the tangential velocity for welding productivity).

The machine was previously equipped with a perforated metallic disc that will also rotate. The idea is that we could calculate the rotationnal speed by mesuring the hole/metal alternance (using light or inductive sensors for example).

Knowing the rotationnal speed, we would be able to display the tangential velocity according to the diameter of the tube (previously selected through a short list of different choices).

The device should be adapted to an industrial site with vibrations and dust. It should also be as cheap as possible.

I guess that the simplest kind would be composed of a computer/microcontroller, a sensor, a display (7 segments, lcd?), and a button for selecting the diameter.

I thought of using an arduino but I'm afraid it would be too expensive and fragile. My research led me to think that the 8051 was a good option. I had some microcontroller courses but they were way too superficial. 

I have some notion of programming and electronics but the main point is to learn as much as possible as I really enjoy this kind of projects.

The main issue is that I don't really know where to start, the documentation I find on the 8051 is not very clear and I sense that I lack the main notions to understand properly what I should do or where I should start.

So if you guys have any good advice, tuto, ressource, similar project in mind that would be awesome.

Thank you for reading and sorry if it was not clear enough, english is not my first language.

Have a good day,

David