Need MATLAB? No money? Don't want cracked software?

(Recovering from a hangover in a hotel room in Colorado... Had this written up a while ago, figure I might as well put it up.)

Try Octave. Wiki article describing it is here. You can get get a Windows-compiled version here.

Basically it's a freely-distributed program that's eerily similar to MATLAB. It's driven off *.m files and uses much of the same syntax. In fact, I was able to take a MATLAB script I had put together and run it in Octave with the only change being in the plot command. Does seem to run slower, at least with for-loops... probably on account of MATLAB's just-in-time compiler.

MATLAB is more polished, has a broad range of toolboxes, and is more user-friendly (believe it or not!), but if you need something in a pinch, Octave works well.

Lacking anything particularly cool and racecar-related to show off, I put in a Lorenz attractor. Fuck it, why not?

OK I lied - recommended reading and then I'm done for 2010

Yes, it is that boring sitting around on Christmas Eve in the boondocks of Colorado. To be honest, doesn't even feel like Christmas at all! In any event I'm assuming some of you folks might be in similar situations or have some spare time to screw off over the next couple days. As such, figured I'd share some good online reading material that I've been following.



Hyperbole and a Half

One of the funniest things on the internet. Suits my sense of humor perfectly. The title really describes the content quite well, and I'm not sure what else to really say! She's cute, too! But unfortunately (for me) not single.

If you like simple funny drawings and sarcastic hilarity, scope it out.




Smart Football

Believe it or not, American football at the professional level is a very cerebral game, and takes some definite mental capacity at every position (not just the quarterback, a la Peyton Manning). Even the 300lb offensive linemen have a lot they are responsible for knowing on every play. If you don't believe me, take a look at an except from the Cardinals playbook (10 pages, from ESPN)... or you can download all 463 pages of the 2000 New York Giants offensive playbook (10MB). 463 pages just for offense, let alone defense and special teams.

In any event, Smart Football by Chris Brown is a cool inside look at football strategies... how the plays are designed to attack different defensive schemes, or how to confuse and attack the quarterback. Really interesting shit, and has made me enjoy the game a lot more since going to games smashed while in college. Even gets into some statistics of analyzing different teams or coaches tendencies in certain situations, etc.



Scarb's F1 Blog

Craig Scarborough describes himself as "a freelance journalist\illustrator who focuses solely on the technology of F1." (and in this case, the Audi R18). Pretty good technical look at a variety of technical aspects of F1 development. Fantastic illustrations.

Includes anything from aerodynamic development, recent trends in setups (including the option of no rear corner springs), sensors, ancillaries, etc.



Vintage Metalworks Blog

Dave is one of my coworkers who enjoys metalworking and restoring old cars. Personally I've always been big into machining and TIG welding since college, but Dave takes it to the next level with some really fantastic sheet metal work. Only started blogging recently, but I expect this to have a lot of good content in the next year.

Incidentally, that photo on the right is the Fadal 3-axis VMC that currently resides in his garage. Fun little side venture - he picked up the bill on the machine, and I bought most of the tooling. While mechnically it's vintage 1987, the controller has been upgraded to a 2006 model. Need something machined? We'll do it for a fair price!

Allrighty. Merry Christmas, ladies and gents. I'm gonna have a beer, watch Law & Order, and play with the dog.

Last entry of 2010

I'm out in Durango, Colorado at the moment... visiting my folks for a week then spending a few days up in Boulder & Denver for shenanigans with college friends. As boring as staying with the 'rents is, I didn't bring much with me so I can't really do much racecar work. I do have a good update though!

On the simulation stuff, I made a huge step forward in the code. The previous cornering model was pretty crappy to be honest - constant velocity. I changed that up and have brake and throttle modulation working. I also changed the way it solved the straightaways. Check it, suckas-

I mean for Christ's sake, the previous version took longer to run than the lap itself! Cut it down to 5-6 seconds to solve. Also got the lap times much closer to reality... I had forgotten to make a conversion from feet per second to miles per hour so my lap times were off by 50%! Still, this isn't fully tuned... but I know the F1000 cars at Road America this year were running anywhere between 2'03"s and 2'20"s or so.. and I'm at 2'13". All is looking good.

Some interesting stats on the blog itself... with some of the stats Google started giving me:

• Total views: 12,285 (don't think it started counting until middle of year)
• Views in last month: 3,350
• Views back in September: 1,957
• Followers: 84... that I know of

I appreciate all the comments everyone has left - I try to reply to all of them. If you have a question or comment or whatever, feel free to leave it.

Despite the slow start this year, think I got a hell of a lot of momentum going here toward the end. Looking forward to 2011 - both personally and professionally. Hopefully making amends with some people (one person in particular), maybe making some decisions on what direction I want my life and career to take. Lot of things to consider.

In any event, I thank all for stopping by and hope everyone has a good holiday. I'll catch you all next year-

Jersey Tom - Giants fan, vehicle dynamics engineer, tire data guru, and all around cool guy

A thought - LoLTD vs. LaLTD

Been quiet here for a couple days. Got a call from my friend on Saturday morning telling me to drive the 460 mi / 740 km out east since he had scored Giants tickets from some random dude at Starbucks.

Unbelievably embarrassing loss to watch in the last seconds of the game, but hey, what can ya do. Play the next game, keep marching toward playoff contention. Thankfully we had Sorrento's (probably some of the best cold subs you can find in the entire goddamn universe, 100x better than anything in Ohio), so that dulled the pain. Personally I recommend the #1 with onions, lettuce, tomatoes, roasted peppers, oil and vinegar, salt and oregano. As for drinking at 930am? Don't judge.

Back to the point at hand, I wanted to get a couple notes down for my own reference here. In vehicle dynamics parlance, 'LLTD' commonly refers to lateral load transfer distribution - a key number for cornering balance. An extreme example of front LLTD bias is shown below. Boogity boogity boogity.

One would think that there's an analog to this in the longitudinal direction (hence Longitudinal Load Transfer Distribution versus Lateral Load Transfer Distribution). It might be nice, on-throttle when the car pitches back, to be able to transfer more load to the inside rear tire for extra forward bite (exit speed is king) at the expense of front axle lateral capacity. Yes, you can have power-on understeer even on RWD cars.

On a road course car I can't imagine having much difference in wheel rate left-to-right on the chassis. Can we do it with some tire rate and kinematic trickery like we talked about before? I suppose if you start with negative camber all around... as you go into roll in a corner and the tires all gain inclination in one direction the insides will have a softer rate than the outsides, and your LoLTD then biases itself to dump load on the outside rear. Pretty much stuck with that with a SLA suspension. Shit. Well, at least it's something to take into consideration and highlights the importance of having good tire rate data over a range of conditions.

I crack myself up

Good quote...

...by the infamous Bill Cobb. Don't roll your eyes too much.

Having a Matlab wizard on a race team is as important as having a tire or engine specialist. There ought to be plenty of work to keep them busy. This is New School Racing theory. Old School is struggling...

Trail-braking: AKA, "Not driving like an idiot"

Let's get ready for the meat of tonight's discussion. You'll probably need to put on some tunes, it gets lengthy. Credit to Laura for this one (an incredibly bright masters degree aerospace engineer with a passion for wedding planning and such - hence the blog).

If you've seen my earlier sim outputs, they drive the corners at constant speed (the apex speed - it's driven as a constant radius corner). In other words, all braking and accelerating is done in a straight line. Only reason for that was for simplicity, ease of coding, and getting something simple up and running. If you were to look at a plot of the driver's instantaneous inverse corner radius along the length of the track, it would look something like this:

In reality if you drive like that, you're going to be at the back of the pack. Not going to go into the details why here - feel free to read any number of racing or driving publications. In any event, given that trail-braking (and throttle modulation out of the corner) accounts for such a big improvement in lap time I was getting pretty skeptical that my sim in it's current form would give accurate direction results at all. As an aside, you can look at 'inverse corner radius' as a way to quantify the line your driver takes over the course of a lap, or a couple laps - even if speed and lateral acceleration change. If you're data logger is grabbing velocity and lateral acceleration it's a snap. Alternatively I believe it's a canned math channel in MoTeC i2. Can't say I came up with it.

Anyway, the other night while laying in bed and I got to thinking - I'm way behind on Christmas shopping, I haven't had Peking Duck in a damn long time, was completely boggled my some woman issues from this summer, and then the next logical thought in the progression was how to solve this combined acceleration problem. Might be easy.

First step - cut in the corner into two halves.

My corners already have an assigned value for apex radius and total length / duration. I'll have to set an additional variable for apex location as a percentage of the total corner duration. This way I can look at which corners benefit from early or late apex (if I'm crazy enough to do that later on). I pick some arbitrary way of defining how the radius transitions through the corner - maybe with a spline or parabola.

Second step - establish combined slip friction ellipse
I've talked about this before here. Earlier I was talking about the ellipsoid being stretched due to downforce but you'll have it from mechanical grip as well. Simple example - you have four tires to brake with, and only two (in this case anyway) to accelerate. In addition to having the ability to specify unique values for braking and acceleration I'll probably also have the ability to have unique values with left- and right-cornering. Don't think a road course car would have an asymmetric setup? Take a look at Lime Rock Park. Might as well be NASCAR in reverse. Only has one left turn, and six rights.

Third step - solve each half's forward velocity trace
Really similar to how you'd solve a straightaway... though this time my acceleration function is going to be based on the engine torque supplied and delivered at the wheels, or the combined slip ellipse (whichever is lower).

For braking, I can do the same shit in reverse for the first half of the corner. Honestly the only hard part is going to be putting in enough code  to make it do something realistic when you have a corner that you don't brake for and accelerate through. I'll have to figure that one out later. Once I get this corner thing figured out though, the straights on either end should still solve themselves just the same. All this work is going to have to be put off until another night anyway. Still got other stuff to do tonight. Apparently there's a pro open-wheel team starting to look for FSAE grads with vehicle dynamics and simulation experience. Hmmmm. Tough life and career decisions, just as I thought I was ready to settle a bit and move back east or west. Then again, who would want to leave the wonderful world of working at a tire company?

As a final note, you'll see that I slightly changed the name of the blog. I got a kick out of it. If you don't "get it," you're missing some good books in your library.