FCIWYPSC

Things you don’t learn in physics December 3, 2010

Posted by mareserinitatis in electromagnetics, engineering, grad school, physics.
Tags: engineering, physics, sea urchins, simulations
5 comments

One of my fondest memories of doing my masters degree was when I decided that I was going to prove out everything I’d been doing in my simulation work. This was in the days before we had our nice anechoic chamber.

I’d been designing antennas, so we took a cartful of antiquated equipment into the middle of a field, where we would ostensibly not have a lot of electrical interference and took a bunch of patterns.

When I got back in and was able to analyze my data, I realized that aside from the fact that my pattern seemed somewhat misaligned, I had something that looked like a sea urchin.

For all the effort of dragging that equipment around, it turned out that I’d managed to ruin things by having my cell phone in my pocket: it operates in approximately the same frequency range as my antennas, and the spikes were probably the phone attempting to communicate with a nearby tower.

That was the day that I learned how difficult it can be to go from equations or simulations to making something that actually works the way you want it to. When working on my undergrad in physics, I became adept at looking at analytical solutions at things, but I don’t think I got a really good handle on what they really meant by “ideal case” until I went into engineering.

Right now, I’m starting on a new project that involves building certain package components. I was discussing the project with the engineer who will be designing and building them (where I will be modeling and possibly testing them). We were discussing the electrical properties of one of the objects, and without thinking, I reached up, grabbed a textbook, and started discussing the theoretical behavior.

He made some comment about “that’s how grad students think”.

We have this problem. He is not sure what his yield will be, so he wants to make a whole bunch of variations on the design. However, each variation for me means a lot of time in terms of building my models and then computer time running them. I’d really like to keep my modeling work limited to about a dozen designs so that I’m not sitting there, still working on things next year at this time.

But when you build these devices, you don’t know what your tolerances are and how difficult it will be to make the device to spec. There may be problems with process, and so you may have to make a lot of changes to see what works.

It’s almost certain that it’s not going to operate the way it does in the simulations.

Sometimes it makes me think that modeling is a somewhat useless exercise. On the other hand, who has time to build and test hundreds of devices to see what works? (I mean…other than people like me and the other engineer.) At least with modeling, you have an idea of how it should work, and you can also tell if something is really amiss. Once you understand how your device deviates as it goes from simulation to testing, you may have something that makes it easy to predict what device will work for a particular application. Or maybe you can incorporate more and more of the real-life dynamics that affect your device into your model to make it increasingly realistic.

The scientist in me loves to come up with predictive models. It’s just that sometimes I feel like I’m trying to develop a perfectly spherical sea urchin.