Accelerator Pedal Fedback?

Well, my wife and I just picked up our Prius yesterday, and I've been practicing my high-mileage techniques. What I'm wondering is if there's a good way to get some feedback on what state the car is in while driving without looking at the MFD.

Looking at things really simplistically, there are really three basic modes of operation in Drive without touching the brake pedal: accleration, gliding, and "simulated engine braking" regeneration. I understand why Toyota put the fake jake brake in - it makes the car drive like a regular machine, but efficiency-wise, it's infuriating. Ideally, I'd love to be able to disable it , but I doubt it's possible without major headache (and a voided warranty).

So what I though of was some sort of feedback from the accelerator position. This could either be physical, with a mild detent that makes it easy to find that sweet spot where all the arrows go away, or audible, with a tone that changes pitch or gets louder as you approach the gliding point. It might also be possigle to tap into the inputs for the MFD and sound a tone whenever the car enters gliding mode and another whenever it exits...

Anybody done anything like this? Any good ideas on how to do it?

 

Yeah, it's the same basic concept as a progressive linkage - just something to let you know what effect your inputs are having on the car's operation state. The audible idea came from variometers for sailplanes - basically, they give an audible indication of whether you're going up or down, and you can train yourself to react almost instinctively to the input.

I though about the Scangauge II (which is a really nifty unit), but it only reads out the TPS, so I'd have to look at the display and then process whether the value is what I'm looking for. I'd like something that I can react to at a reflexive level, and that doesn't distract from the road *at all*.

This is more of a gee-whiz question than anything else, as I'm sure I'll learn fairly quickly how to handle the machine. But strong feedback would sure accelerate that process.

 

The only trouble with displaying engine power is that it wouldn't tell me if it had dropped into regen "simulated engine" mode. Does the scangauge have any functionality to read back any of the hybrid behaviors?

Someone a lot better with microelectronics than me could probably whip out a PIC that would read both engine power and hybrid performance off the CAN network through the ODB port, crunch the numbers, and sound a tone...

That's way outside my league, though.

Really, I think I'm already getting pretty good at feeling the little lurch as the regen disengages - I still can't back down from a high "throttle" setting and find the glide spot without first dropping into braking momentarily and feeling my way back up to glide.

Oh, how I wish I could hack the power-control logic and remove the "make it drive like a normal car" features. The simulated "creep" catches me occasionally at stoplights, too. Why not just have it behave like the pedals are labeled - the accelerator only controls acceleration, and the brake only controls braking! What a concept!

It reminds me of a fellow I know who worked on the Joint Strike Fighter flight test team. When the Navy pilots flew the plane, they specifically requested that the flight control system add in the bad habits of the F-14, since the pilots were all used to them. Toyota's done the same thing with the gas and brake pedals in the Prius.

Seriously, we really need to get away from foot and wheel control and go to a center-mounted stick anyway. Reaction times are better, and steering is more instinctive (once the driver adjusts to the new control system)

Wow - let's see how far off topic I can take a post! B)

 

<div class='quotetop'>QUOTE(Frank Hudon @ Oct 18 2006, 11:31 PM) [snapback]334920[/snapback]</div>

Yeah, but without it, you'd end up doing more regnereation with the brake pedal, right? You still have to slow down sometime. With it, you often end up regenerating when you don't need to (unless you carefully modulate the pedal), right? As I understand it, that's the whole point behind pulse and glide driving. Gliding is more efficient, because you're only losing watts to rolling resistance, aerodynamic drag, and other totally unavoidable factors. When regenerating, you're also losing watts to the inefficency of the motor/generator, the DC/DC convertor, IR of the battery, and other electrical factors. It's still a heckuva lot better than caliper brakes, but I can't see how regen can be more than 45% efficient, and it's probably a lot less than that.

So at the end of the day, it wouldn't bother me if the ICE ran a bit more (in terms of time) to charge the battery, particularly if it did it while I was already at a fairly efficient throttle/RPM setting. I would posit, however, that it would not run more in terms of energy - simple first-law analysis. Since there is no other source of energy on the car other than the fuel (battery isn't a source, it's a storage system), then every watt-hour of energy the car carries, whether in terms of kinetic energy, physical potential energy (at the top of a hill, etc.), or chemical potential energy (battery SOC), had to come out of that fuel at some point. The key is to maximize the efficient extraction of that energy and minimize the loss of it to the car's necessary inefficiencies (which are much reduced on the Prius).

This is why pulse and glide works (in almost any car). Almost all engines are more efficient at higher output, so you accelerate strongly to maximize the kinetic energy that your car is developing when you're using the engine. Then you disengage as many systems as you can and let the car coast back down a bit, burning no fuel in a Prius and very little fuel in a stick-shift non-hybrid. Lather, rinse, repeat.

All I want to do is get better at the discernment of when I've acheived that "disengaged" mode, since there's no clutch pedal I can stomp on. Of course, I really wish the car would let me decide when I want to accelerate and when I want to decelerate - lose the bad habits of automatic transmissions, since this isn't one. Hey, there's a cool idea for a mod - software logic to make the car drive like a manual/tiptronic hybrid. "Upshift" and "downshift" controlled by the "gear selector" switch, along with a "clutch" on the floor to let the wheels spin freely. Upshift and downshift would only really be useful as a kind of "passing power" and "manual overdrive" mode, but the clutch pedal/button would be really useful for hypermiling.

(There I go again, taking the post far afield... )

Sorry for teaching my grandmother how to suck eggs - I find that I learn a lot more about a concept when I think out loud about it (or in this case, "think in type").

<div class='quotetop'>QUOTE(ken1784 @ Oct 18 2006, 11:50 PM) [snapback]334927[/snapback]</div>

Sounds pretty cool, ken, but so far I only speak English and a bit of German and Spanish. Ah, well...

 

That's a good point about neutral - do not know why I didn't think of that! DOH!
The foot is learning, but I'm sure it's got a long way to go...

I wonder how possible it would be to put in an electronic clutch - something that triggers neutral when stepped on, and drive when released - that would also work quite well, and eliminate the need for any foot dancing on the accelerator. It could be mounted on that left-foot rest... interesting...

I'm pretty sure we're back into warranty-voiding territory here, but it might only require an in-line harness on the back of the gear selector switch. In that case, you could remove it before taking the car in for warranty repairs, and nobody'd be the wiser.

I know you can do the same with your had on the selector, but this lets you use both hands for the wheel, and would be intuitive for those of us that have already learned pulse and glide with stickshifts...

I may have to seriously investgate this - a sewing machine pedal and a bit of wiring might be all it takes...

Oh, and will neutral engage at over 42mph - your post implies that it might not...

 

Just found the answer to my own question - if neutral is engaged at higher speeds, the ICE still runs - nonoptimal to say the least for mileage concerns. I guess I'll just have to learn to modulate the pedal for "warp stealth"....