Downshift computer

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revsin
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Downshift computer

Post by revsin » Fri Jul 29, 2016 9:16 pm

I apologize in advance for the nerdy nature of this post but I've got autism and this is what makes me excited.

I'm new to driving a manual car and as we've all been there, gotta downshift. You've got enough going on between your two hands and feet that doing the simple math is your brain's last straw when you're braking for a right hander and you need to downshift from 4th to 2nd. Course with practice and experience you'd overcome that anyway. But why not simplify the task by overcomplicating your evenings with a homebrew technology? Because you can!

My thought is to use an Arduino microcontroller, ODB2 UART serial adapter connected to ODB2 port. Gather data from the ODB2 of your RPM and your wheel speed. Do the math to determine what gear would be the most appropriate for the wheel speed as well as calculating what the RPM should be for a perfect shift for that gear. All output to a realtime display.

It'd be hard coded to my particular vehicle, but it seems easy and approachable enough to make it work. I'm gonna give it a go even if the idea is overkill.

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Re: Downshift computer

Post by tankinbeans » Fri Jul 29, 2016 9:29 pm

I usually do a smash and shift not worrying or even striving for perfection. When I turn I don't pay much attention to the console or instruments panel, do my 6 to 3, and go. Sometimes I realize I should have done a 6 to 2, but usually it's all gravy.
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Re: Downshift computer

Post by IMBoring25 » Fri Jul 29, 2016 9:57 pm

Perfection is fickle and not really necessary, but I am also guilty of occasionally taking on silly projects for the novelty, challenge, or both.

The primary trick here would be the logic for what it thinks is the appropriate gear. There's a considerable amount of "art" involved in gear selection depending on how much acceleration you want to do, how long you're going to be traveling at a given speed, or whether you think you're going to have to stop at the traffic light up ahead. This is the same challenge the dual-clutch transmission designers face because you lose the advantages of the dual clutch if the transmission doesn't have the correct gear pre-selected. They build in throttle position, rate of acceleration, and even whether you're braking to decide if you're likely to upshift or downshift next. It's even trickier for you since you can block-shift, which a dual-clutch can't. Cruising along in sixth will look exactly the same to the Arduino regardless of whether you're on a two-lane and need to hit third to get the acceleration to get around someone or whether you want to hit fifth to slightly expedite a casual pass on a six-lane interstate.

On the driving front, you do have the option of doing a double-clutch, with which you use the engine to do the synchros' work. Shift to neutral, let the clutch up, rev the engine to approximately what you think you need, then press the clutch again and complete the shift. Not only can it be a little easier on the equipment when done well, but the feel of the shifter going into gear after a double-clutch can give you a little feedback of whether your RPM was too high or too low before you let the clutch out in gear and run the risk of bobbing heads around.

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Re: Downshift computer

Post by revsin » Fri Jul 29, 2016 10:03 pm

I will not agrue that the act isn't beyond a simple human like myself, but I love an excuse to play with nuts, bolts, volts, bits and bytes. So the fact that it's not needed is not reason enough for me not to want to do it anyways!

I love these two quotes:
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You learn a tremendous amount solving problems that don't necessarily exist, creating the problem to solve is often worth the journey. If human beings don't love creating problems, why do we keep getting married?

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Re: Downshift computer

Post by theholycow » Sat Jul 30, 2016 7:43 am

revsin wrote:If human beings don't love creating problems, why do we keep getting married?
Can't argue with that logic!

The big problem here is that it can't have access to all of the necessary data, much of which is in your mind. A major part of gear choice is looking far ahead to read the road/traffic and predicting, as well as integrating your emotional state. You could use fuzzy logic to get a vague reading of general emotional state for the day/hour/etc. If you want to go overboard you could build or integrate self-driving car systems to read the road ahead (and maybe navigation and topographical maps) and try to duplicate the types of decisions you would make, effectively attempting to process the same traffic and terrain data that your brain does to produce the same decisions. Going even more overboard you could pull in biometric data to help guess emotional state. If you really want to go to extremes, you could use a brain scanner for a more accurate guess...though I'm not sure if the technology can tell the difference between stressed/worried about getting there on time vs. stress/worry about a smooth ride (for that delicate wedding cake you're hauling) or fuel economy.

Automatics don't need to read your mind or the road because they can read your foot, but that data won't be available for manual drivers until after the shift has completed. Also, if wrong an automatic can complete a second shift much more quickly, though hunting annoys drivers and has largely been eliminated from computer-controlled automatics.

Of course you could include a switch for power/normal/economy mode (as was popular on automatics 15-20 years ago) or, even better, a dial/analog lever, but things change suddenly when driving. You could have the display offer three gear choices, color-coded appropriately for speed, normal, and economy/gentle driving with the center one being a larger font, or just use the system's output as a suggestion that you modify, but that would seem to make the system pointless by bringing human decision-making back into it.
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Re: Downshift computer

Post by tankinbeans » Sat Jul 30, 2016 7:48 am

Is it possible to crib some of the logic from the GTR, which does the revmatching for a person? Can that thing revmatch for a multiple gear downshift, or would one have to go through several gears sequentially?
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Re: Downshift computer

Post by theholycow » Sat Jul 30, 2016 7:49 am

^Tank, you must have read my mind...you posted that as I was typing this up:

Another thought: You know what would be more realistic and useful? How about a rev-match computer? There is prior art for those; the latest high-end systems include automatic rev-matching, which I assume reads shifter position as you are shifting to your desired gear, but if it's only going to display target RPM then it wouldn't have to wait for that data, it could display rev-match target RPM for every gear all the time...either format the display in the H-pattern or linearly, with a placeholder for the current gear in a larger font (if linear) and everything color-coded (whether linear or H).
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Re: Downshift computer

Post by Rope-Pusher » Sat Jul 30, 2016 9:49 am

...and what would the output be..if it's going to be digital, better round it to the nearest hundred rpm or it will be too busy to read as your vehicle speed changes.
Yanno, during transient speed periods, digital speedometers are not as easy to read as analog speedometers. You might find the same is true for the rev-match indicator.
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Re: Downshift computer

Post by revsin » Sat Jul 30, 2016 10:23 am

I did not word my idea as clearly as I had hoped, but rev-matching computer is really what I was trying to articulate.

Could use some hall effect sensors to determine what gear you're in. If I use a TFT display then I could easily display the desired RPM for each gear all at once as a float value. Making the assumption that the baudrate from the ODB2 is fast enough.

I've already ordered the UART pigtail so now it's just a matter of receiving it and start failing!

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Re: Downshift computer

Post by theholycow » Sun Jul 31, 2016 10:06 am

I would guess that OBD2's baud rate is fine, but the refresh rate of published data is definitely lame. You don't get a live stream of every variable; instead you can poll for updates every 1 to 3 seconds and the results may be laggy. That would be fine if you're climbing a hill and need a downshift to maintain speed or planning a pass and need the downshift for acceleration, but it won't help when you've suddenly braked off a lot of speed and need a downshift ASAP. However, even just using it for those purposes where it works well, it could make a nice training tool.

What about going a little lower-tech with the tachometer data? Before there was OBDII, engine speed came from a signal from the ignition system, and even with OBDII that's where the ECU gets the data that it uses to drive the tachometer and provide OBDII RPM data. You could tap that same upstream signal. Google will provide plenty of documentation on exactly how it works. That data is real-time and you can sample or ignore it on your own schedule.

For gear selection there is definitely prior art and you may do well to imitate it. I'm guessing that shift position is sensed with relatively low-tech mechanical switches.
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Re: Downshift computer

Post by Rope-Pusher » Sun Jul 31, 2016 11:20 am

Image
VW Beetle had this ages ago....or at least the original version of this.
Image
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Re: Downshift computer

Post by potownrob » Sun Jul 31, 2016 4:34 pm

tankinbeans wrote:Is it possible to crib some of the logic from the GTR, which does the revmatching for a person? Can that thing revmatch for a multiple gear downshift, or would one have to go through several gears sequentially?
if the GTR's anything like the DSG of the GTI (hey, they're only one letter off; must be related... :lol: ), it would only plan for one gear up or down and only be fully prepared for shifting one gear up or down, and only one way or the other. GTI is said to have gotten a lot better at predicting which way (up or down) the driver will want to go though, since the earlier DSGs of 10 years ago. If you go more than one gear up or down, or go the way the transmission/computer wasn't expecting, it is a little slower than going with the gear it was ready to shift into... :shock: :? 8)
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Re: Downshift computer

Post by tankinbeans » Sun Jul 31, 2016 5:02 pm

Rope-Pusher wrote:Image
VW Beetle had this ages ago....or at least the original version of this.
Image
That looks like a hot mess, and nothing I would want to attempt to decipher on the fly.
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Re: Downshift computer

Post by potownrob » Sun Jul 31, 2016 5:52 pm

tankinbeans wrote:
Rope-Pusher wrote:Image
VW Beetle had this ages ago....or at least the original version of this.
Image
That looks like a hot mess, and nothing I would want to attempt to decipher on the fly.
Autostick FTW?? FTL?!? :?
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Re: Downshift computer

Post by Rope-Pusher » Sun Jul 31, 2016 5:56 pm

Ees no sew bad. It's showing rpm in each gear for a given vehicle speed via a decal pasted atop the speedo lens.
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