When and how do you create a whole-robot design?

[Siri]

Originally Posted by ohrly?

What I mean by this is, when do you transition from making mechanisms to putting those mechanisms together into a robot?

Traditionally, our team has struggled because we have built mechanisms, and then we put together a really bad combination of items that don't complement each other. Things like using mecanum wheels that don't actually have the traction to put out all the force our gearboxes can provide (we gear them too high, so we go slowly without any added push), especially when strafing offered us no strategic benefit. I'm frustrated by it, and I can't say I'm not part of the problem, but my team HAS to change the way we design our robot.

Any advice?

It sounds like you have three separate issues: strategy for design, systems integration, and detailed design (particularly verification to strategy). I think you'll find most perennially strong teams have their whole-robot strategy laid out and prioritized within the first week (maybe two if you have fast manufacturing). This is turned into functional objectives--not strafing when it's not useful, and making sure the mechanisms you focus on will actually help you perform to your best. You might like Karthik's Effective FIRST Strategies presentation (here's last year's) as well as the QFD presentation from FiM Championships.

Systems integration--putting the mechanisms together into a robot--is also something much easier/better done before and with mechanism development rather than after. When we nail down out strategy, we also roughly allocate things like space, weight and motors. As mechanism designs (both CAD and prototyping in our case) mature, the system integration matures with it. This is not an easy task, but it's worth it to have a better robot at the end. We're usually done the major integration decisions by week 4, though the chassis and drivetrain construction at least starts before then. It continues to change a bit until...well, this past Saturday. Actually, the Saturday of IRI.

Finally, you've learned that mechanism design needs to keep the strategy in mind. If you want to go fast but also strafe with mecanum, you need to work out your gear ratio based on that. The same goes for everything else--how high will your shooter mount? How ling can your climb take? etc. We constantly iterate this as well.