Do servo driven transmissions that make better decisions than drivers exist?

Factual Questions
1

At it’s heart, the finding the gear problem is pretty simple. You know the exact power developed and the fuel consumption per unit of power developed at any RPM. You can update those numbers in real time from ECU data.

You know the vehicle speed, the derivatives for that speed, and running averages of speed and their derivatives.

So, anyways, given this information, you could calculate the shift points at the points that save the most fuel. You prevent “hunting” by making the downshift threshold a little more complex than just a simple number, you also track derivatives (so if the optimal threshold is 1400 RPM to downshift but the RPM is only dropping by 1 rpm/second, you don’t downshift right on 1400 rpm)

Anyways, I don’t really understand why manual transmissions are still a major thing, especially on 18 wheeler trucks. In solving the gear problem, you can take into account hundreds of variables, ultimately (most would feed into the ECU and be available indirectly), and much more exact information that humans can perceive. You ultimately only have a handful of possible output states to consider, and most of the time there are only 2 variables to optimize for : maximum fuel efficiency with mechanical wear per hour below a calculated maximum. (since there’s no point in saving the user fuel if you burn up your transmission with constant gear shifts)

2

Have you ever heard of cars with CVT? It stands for continously variable transmission and pretty much works as you describe. It costs a little more, but gives better mileage and needs less maintenance.

3

Trucks in Europe are almost all fully automatic these days. I think that many operators in the US are reluctant to move into the 21st century.

These gearboxes are not the kind you used to find in cars, with a couple of gallons of hydraulic fluid sloshing about, but dry plate with servo operation. The latest developments link the whole system to the GPS, so that the truck (when cruise control is operating) can anticipate hills and bends etc. and take the appropriate action. Radar to keep them in the right lane and slow them down if they get too close to another vehicle is almost commonplace too.

It may be a while before a clerk inputs a destination and the truck just takes itself there, but it will surely come.

4

I’m confused at what exactly you’re getting at here. It sounds like what you’re describing is pretty much how an automatic transmission works.

The traditional drawback to automatics wasn’t that they were bad at deciding when to shift, it’s that they transmitted power less efficiently than a manual. Granted the old hydraulically controlled ones weren’t as good at picking shift points as today’s electronic ones but that was only ever a driving feel issue, not really an efficiency one.

It is difficult to make a case for a manual these days. In addition to the efficiency issue, they also were cheaper to buy and operate and were generally more reliable, but modern automatics have mostly closed the gaps. With heavy-duty truck transmissions, I believe the purchase and maintenance cost numbers still slightly favor manuals whereas the automatics have a slight fuel efficiency advantage. So in North America they’re still mostly manuals, but in Europe they’re moving more towards automatics.

Slight nitpick here, but at least the current crop of CVTs have shorter service intervals than conventional automatics, and those services are generally more expensive because they take special fluid. It could be a case of the automakers being overly cautious with a technology that has flopped in the past, but for now they’re definitely higher maintenance.

5

There’s actually a self-driving 18 wheeler truck on the road now, Nevada is allowing it. Still has a human on board to monitor things and for unanticipated emergencies, and to take over driving if it crosses into a state that doesn’t allow self-driving vehicles. Point is, yes, it’s coming and a lot sooner than most people realize.

6

A salesman told me a couple days ago that CVT lasts the life of the car and doesn’t need any maintenance at all as long as you change your oil on time.

7

But what your gearbox does NOT have is the driver’s knowledge of what’s happening in the road ahead. Surely that’s one advantage of a manual box.

8

All this really means is that when the transmission goes out, it’s time to get a new car!

9

No - because the choice of gear ratio is a very small component in driver judgment. The driver should be free to take whatever basic action is needed, and have the machinery follow that lead.

My '07 Honda is surprisingly “intelligent” at giving me the right gear when I brake suddenly, accelerate etc. I don’t have to stop and add that judgment, action and distraction to the mix.

Highways are not an F1 track, where the absolute pinnacle of driving judgment and awareness trump everything else. (For that matter, most F1 cars these days are all but automated anyway, for precisely the same reason of giving the driver more time to apply to things the machinery can’t do.)

10

Not sure about this…GM gave up on CVTs, because of serious longevity issues. Audi had had a lot of trouble with theirs. They do not seem to be all that popular.

11

It used to be that automatic transmissions had several major disadvantages over a manual transmission.

First of all, they transmitted power through a thing called a torque converter. Imagine two fan blades, one connected to the engine and the other connected to the drive shaft that powered the wheels. Enclose the fan blades in a box and fill it up with fluid. As the engine’s fan blade spins, it spins the fluid around and causes the other fan blade to spin, which turns the wheels. The good thing about this is that, because of the fluid sloshing around in there, it’s possible for the wheels to stop but the engine can keep spinning (for comparison, you have to push in the clutch on a manual transmission whenever you stop). The bad thing is that you never get a good solid connection between the engine and the wheels. You always lose energy to sloshing fluid around.

Second, because of their mechanical complexity, automatic transmissions often had only three gears where a manual transmission had four or five. This made it much easier for a human to find a better gear than for the automatic transmission.

In more recent years, they’ve come up with a thing called a lock-up torque converter. This works like an ordinary torque converter when you are stopped or are shifting gears. But when your speed settles out and you are just cruising, the torque converter “locks”, which locks the engine to the drive shaft so you get that solid connection with the wheels like you do with a clutch. When you need to stop or shift gears, the torque converter unlocks and functions like an ordinary old torque converter. Now when you are cruising around, you are no longer losing energy to sloshing fluid around, so that gets the efficiency of automatic transmissions much closer to the efficiency of manuals.

Modern transmissions, with computer controlled shifting and much less clunky shifting mechanisms, now have many more gears internally (and we have CVTs, as was already mentioned) and can find an appropriate gear much more easily, again getting closer to a manual.

A driver who drives well can still manage to out-shift a modern automatic, but you have to be careful how you drive now to do it, where in the old days pretty much any idiot who could drive a stick could out-shift an automatic. The gap is a lot narrower now.

As was already mentioned, humans still can see the road ahead and can make adjustments accordingly, where an automatic transmission has less data to work with. I’m wondering if some of the road and traffic sensing that they are doing for automatically driving cars and trucks will make its way into automatic transmissions soon. That could close the gap even further.

12

I’m of two minds on this (waiting until someone like Rick shows up to the thread). When recently looking for a new-to-us car, we looked at several that have CVTs. The Nissan Versa comes with one in the more expensive trim types, and my reading indicated that the early versions are regarded near universally as a piece of shit. OTOH, we ended up with a Prius, which has a similar transmission, and the very high reliability of that model was what sealed the deal for us. 45 MPG doesn’t hurt either.

Edit, engineer comp geek, I thought that the latest auto trannies were in fact better than their manual equivalents? Thinking of things like the latest Porsches, Lambos, Ferraris, etc… More gears, faster shifts, better integration with launch control, etc…

13

There are automated manual transmissions for trucks…

http://www.roadranger.com/rr/ProductsServices/ProductsbyCategory/Transmissions/UltraShiftPLUS/index.htm

14

Most of the complaining about the current crop of CVT’s has been about how they drive. A lot of people really don’t like how they feel, particularly when mated to a fairly slow engine like in a Versa. Reliability-wise I haven’t heard of any major issues.

15

And they’re going back to CVTs in the near future. http://www.greencarreports.com/news/1096281_gm-to-fit-cvts-to-many-car-models-for-higher-fuel-economy

16

to answer the OP, yes, a modern computer-controlled automatic transmission is far better at “figuring out” how to operate most economically. people think manual transmissions are better for fuel economy because they used to be. but that was when you had a choice between a five speed manual and a three-speed automatic.

a manual transmission has performance advantages, for a skilled driver on a track. A skilled driver will know when to hold a gear where an automatic would upshift, or downshift when an automatic would hold a gear.

ever since automatics reached forward-gear parity, they’ve surpassed manuals in economy. and now that automatics have more forward gears than manuals, any supposed economy advantage of manuals is toast.