I mentioned in the first post of this series the importance of thinking carefully about what you're doing and not just going ahead and building something because it'll look right. If you know how to calculate something, like the expected strength of a joint, do so. At least estimate it. Please.
Turns out that I'm terrible at listening to my own advice, as this tale of woe will explain. Continue reading
How The Luggage moves will define the impact1 of this robot, so we've got to make sure that all the bits and pieces will work together to give the desired effect. We'll want it to move at a sensible rate, and to accelerate to that speed suitably to convey the "angry" emotion properly, and finally the hardware purchased should enable that.
So how fast should The Luggage go? Fortunately our requirements tell us that we're after "walking pace".
That's about 3mph. Let's do some sums... Continue reading
As this project had a few parallel activities some parts could be attacked in the few hours available mid-week after work. The Luggage's brain was one such of these activities.
As mentioned before, I'd decided that The Luggage would be controlled by an Arduino microcontroller. The exact flavour that I picked up was the Arduino Micro. It's very compact and would support control of motors / servos through the analogue (PWM) outputs.
Once you've got some idea of where you want to be you've got to come up with some clever ideas about how to get there. There's plenty of different ways to come up with a decent set of concepts like brainstorming, the five Ws and thinking-hats, just for starters. It's worth thinking about which method of concept generation is going to be best for your design and for the group of people that are doing it.
The Six Thinking Hats: Blue = Managing, White = Information, Red = Emotions, Black = Discernment, Yellow = Optimism, Green = Creativity
Design isn't a one-size-fits-all process.
Requirements are important. Really important. Too often though, this vital part of the engineering process is only partially completed or omitted all together.
This project is no exception. D'oh!
So what do we want to make? That's easy:
Ah, this isn't quite right. Whilst this is technically correct (the best kind of correct), it's not enough to go off and build something. Imagine you're trying to get a friend to build The Luggage for you, but they've not read any of the books. If you tell them to go and build a robot, without any details, who knows what they'll make? Might be a Wall·E (good news), might be a T-101 (definitely bad news).
Being the terribly social being that I am, I was invited to a party with several other real-life people in attendance. This party was for Halloween and, of course, obligatory fancy dress. My kind friends suggested that I (as I would be the eldest attendee of said party) should go as some sort of befuddled wizard.
The finished article, as functional as it ever likely to be.
Very quickly, the answer was obviously Rincewind, of Discworld fame, but the engineer in me realised that there was an opportunity to include an awesome accessory to this costume: Rincewind's faithful travelling companion The Luggage.
With my most optimistic engineering hat on, I decided that it would be well within my capability and resources to create a working robotic Luggage in the 6 weeks that I had before the party.
I'm going to split the design (I use the term loosely) and construction of this robot into several posts as there was an awful lot of "learning" (read: mistakes) that went on along the way. Hopefully it will serve as a decent record of what I did in case anyone out there would like to create a Luggage of their very own, and an archive of all the "learning" that I was able to do along the way.
Just in case you're impatient, here's the TL;DR synopsis:
- "Design" is something that should come before "Build".
- Mechanical losses will be more significant than you think.
- If you know how to calculate something, calculate it, don't just ignore it.