Some engineering modeling work

Well, I departed from game dev stuff a long while ago, but in my new area of study, mechanical engineering, I still get to model

So anyways, this past semester we had to design and build a robot which is essentially a mini garbage truck.. it had to maneuver through an obstacle course, lift up little dumpsters(2 in all) that weigh 1.3lb(.59kg) and empty 1lb(.45kg) of "trash"(steel bb's) into itself, then drive up a 30 degree incline and empty the "trash" into the "landfill". Anyways, here's some pictures of the model I made. Not as visually impressive as the stuff you guys make! But there are a lot more restrictions on how I can make this stuff, I can't just grab a vertex and move it around, its all extrudes, revolves, and rounds. Some pieces are up in the hundreds of extrudes/rounds/revolves. Each part is made individually then assembled into the completed robot. All the moving parts move together! It's pretty cool. The program is Pro/E, and is an absolute pain in the ass to use! It is entirely opposite of 3dsmax or rhino3d(the other program I have experience in). Certainly requires a different mindset when approaching making a part.

Anyways, pics!

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And a picture of my team; I'm holding the robot!

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I also have a video of the robot running the course, maybe I'll upload it to youtube or something.

Quote from Sa74n

looks like cad modeling. i never tried or even heard of pro/e but when it comes to cad modeling i definitely recommend having a look at solidworks. its probably the best cad tool out there and actually fun to use.

I've used solidworks, definitely easier to use than pro/e. Pro/E is the software that endorses our school, so we have access to more up-to-date versions as well as add on software(such as stuff for finite element analysis). We're also taught pro/e so I had more experience with it, more confidence that I could get the job done faster.

Quote from DUFFY

That's very cool. How far along are you in your discipline? This seems like something that would be difficult to create without some serious hand holding the whole way through. Was there any programming involved? I noticed the remote but can't tell if it's wireless or tethered.

I'm a second semester junior, so after this week of finals I'll be a senior. There was, kinda, handholding available if needed. More like the teacher is extremely set in his way of doing things, and if you listened to every recommendation he had you'd end up with the same robot as everyone else, boring . I basically ignored all of his (plentiful) criticisms and just told him I was confident it would work, did some math to prove to him it would, and eventually he approved the design. And it worked

There was no programming involved, we were not allowed to do true remote control.. needed to use a tether. I did as much as I could with the controller without going digital, doing full pulse-width modulated speed control and a set of 8 opamps to provide joystick control. Everyone else did simple switches and relays to control their motors, which is what the teacher encouraged; that kinda frustrated me, I mean switches and relays is like 5th grade science fair bullshit! Encourage the students to do something, you know, useful and challenging!

Next semester I get to do senior design, in which I get to pick my own project. I'm planning on doing a fretless bass, with both a mechanical and digital tuning system. I plan on having a set of motors control the tension of the strings to get it initially in tune, then have a digital system which will adjust the output frequency to match the nearest in-tune note. So I'm definitely going to be getting into some programming again, and microcontrollers. I have a little bit of C++ programming experience, and no microcontroller experience, so it should be interesting. I did some reading on the internet already, and it seems like there is a ton of information out there for getting started. Should be fun! I have a whole year to complete it so it shouldn't be too bad.

Yeah, I play bass and guitar. I also build basses, I've been working on a 5 string fretless lately. I've got the body and neck all carved up, still needs a head, fingerboard, and all the hardware. Hopefully after senior design I'll have made all that stuff

Quote from e-freak

you could always try to work with arduino and processing, it's pretty easy and slick.

Yeah I was looking into arduino for the motor control stuff. I'm not sure if it'd be able to handle digitally shifting an audio signal, but we'll see.. thats for next semester For now, I'm done with being a junior and just enjoying my time off! Although it seems I end up working on this project if I sit still for too long...they've made a workaholic out of me.

Quote from 2d-chris

cool stuff, you all look very smart in that picture

Dress a chimp up and he'll look smart :wink:

I have already designed a primary frequency detector circuit and a flowchart for processing logic. Finding the frequency determining the closest in-tune frequency shouldn't be too difficult. What I'm worried about is processing the input signal to produce an in-tune output. The 'proper' way to do this(maintaining all harmonics and character of the string/guitar/player/etc) is to record a short sample, speed it up/(slow it down), and 'add in'(or subtract out) a duplicated segment to fill in the gap created by speeding it up. The segment has to be sufficiently short so as to preserve the changing harmonics/intensity of the input signal and not cause a significant and noticeable delay between playing a note and hearing it, but sufficiently long to create nice sounding output signal. It is fairly elementary to write a frequency detection program for something like Arduino and from that determine an in-tune frequency, then just spit out a sine wave(or similar wave, sawtooth or whatever) in that frequency.. It'd be in-tune, but it would be a 'digital sound'. All the natural harmonics and character of the instrument would be lost, filtered out. I don't want this to sound any different than the instrument itself, just adjust the intonation on-the-fly.

I've been considering using the frequency detector circuit and string tensioning mechanism(which I was going to use just for initial tuning, then use the digital processing to do the on-the-fly tuning) to do all of the tuning, but there are some fundamental issues with that. I am doubtful of the speed and reliability of such a system. The digital system should only require one oscillation to determine what freq is being played, what the nearest in-tune freq is, and how much the signal needs to be sped up to produce that freq, and perform that speeding up. So theoretically it should be able to be in-tune within about 1/40th of a second(lowest frequency on a bass is roughly 40hz), regardless of how out-of-tune the signal is. The mechanical tensioning system will be able to determine whether it needs to be tensioned or de-tensioned in one oscillation, and have some idea of how far off it is, but it will be a continual process of tensioning and checking. I think with a good intelligent PID motor control system, with a lot of testing, it could probably get it right in maybe 5 or 10 oscillations, assuming the tensioning motors have enough balls to tension that quickly. That is assuming the note is reasonably close to in-tune; if it's a quarter-step out, well it might border on impossible, depending on the range of the tuners. But 10 oscillations is still a quarter of a second.. certainly audible/noticeable at that point. And then we have the issue of how long the motors will last, constantly working to keep it in tune.

The benefit of that system is the sound would be as 'true' as possible; all the harmonics and character of the bass would be preserved.

I'm sure it'll take some experimentation, but I have a year to get this done. I think the first half year will be spent playing with guitars and oscilloscopes, trying to get the note-determination and intonation processing figured out. Second semester will be designing and packaging everything into a reasonable size/weight, then of course putting it all in my bass

Quote from Sindwiller

That is ace stuff. Mind if you post a photo of your WIP 5 string fretless?

Sure, here's some. Taken with the iphone so not the greatest quality.. but you get the idea. Still need a lot of finishing work. The two slots in the neck are for truss rods.

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The head is also not carved up yet. I'm waiting until I decide what I'm doing for tuners. I might not need tuners at all, just something to hold the string ends. I do have a design for the head that I like, just need to make sure everything will fit before I go ahead with it.

The body wings are solid Bubinga, the neck is hard maple with two strips of Zebrawood. The fingerboard is also going to be zebrawood. The head is going to be the same wood as the neck, with a Bubinga veneer over the top of it. Its just going to have nice clear stain and waxing, no color. The bubinga really brightens up with the clear stain, deep red with a lot of curl. I'm contemplating doing piezo, optical, or capacitive pickups in the bridge to keep the look very clean, I really like the zebrawood stripes thru the body and I'd hate to carve them up to fit a pickup in there. I also have rather tight string spacing which limits the pickups I can use.. might as well make my own!