GM Announces New Hybrid System

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Show me one that I can buy, then I may be interested, and take a look.

Until then, it's just "Pie in the Sky", and should stay in Popular Mechanics.

 

I just love to see that.

 

HSD is a brilliant system. But I don't see the technology transferring to the future. I don't believe GM will ever build the Volt, and their announced battery range for it is too short (they want you to still burn as much gas as they can force on you).

HOWEVER, the series-hybrid concept is what we really need for the future. Unlike HSD, the series hybrid would allow you to do all your city driving with 100% grid power and zero gasoline. This is a qualitative improvement, not merely a quantitative improvement in gas mileage. And as electric-storage methods improve, the series hybrid moves smoothly into pure EV.

HSD is as good as a gas-powered car gets. But its need to use the gas engine under some conditions even when the battery is still full makes it a poor choice for those of us who want to get away from gas, and not merely get incrementally-improved fuel economy.

Series hybrid also opens the way for 4 independent motors in the wheels, allowing for better traction (every wheel gets power when other wheels slip) and eliminating the problems some Prius drivers have with TC (the computer could just reduce power to the wheel that's slipping: no need to slow the whole engine to protect MG1).

 

put a bigger elec motor in the HSD ( and battery pack )

 

I'm not sure I really follow you. None of the things you mentioned are impossible with a full hybrid system. Now while the current formulation of HSD makes the gas engine necessary even for short trips, this is something that could be easily changed through software and other changes. As battery packs become bigger and better, then the software could be modified to allow for more and more miles driven on electric only (and higher speeds like the Li-On Prius test cars).

Full hybrids are already utilizing a larger battery than series hybrids, and as battery technology increases this could be easily taken advantage of via HSD (more so than it seems in current series hybrids). Now, I don't think the current HSD will be exactly the same in the next generation of vehicles, but it's flexibility in how it is implemented will be useful. As time goes on, better batteries and bigger electric motors could be introduced and changes made to further reduce the need for a gas engine until it is no longer needed.

As far as the four independent motors to the wheels why couldn't this be used in HSD? The TC problems appeared to be more due to faulty implementation rather than a widespread problem due to HSD design based on recent models (2005+) not reporting the same problems as early models.

 

First off, you cannot have independent wheel motors with HSD because HSD is defined by one gas engine, two electric motors, and the PSD linking everything together. With independent wheel motors there is no PSD. Therefore it's not HSD. It's a whole different animal.

Yes, you could enlarge MG2 and alter the geometry of the PSD to allow for more acceleration and higher speed with HSD. But this misses the whole point of HSD: HSD is a system designed from the ground up to use gas and electric simultaneously. EV or "stealth" mode is an accident of the fact that sometimes the battery becomes full and the car must run on electric for a few minutes to bring the battery back to the mid-range where it wants to be. A bigger battery is more efficient because it's better able to buffer the power needs of the car, but was not used due to the cost.

But as you move away from 100% gasoline power (as the current Prius is) to partial or full grid power, the rationale for a car designed to use gas and electric simultaneously disappears. Now you want a car optimized for electric use, where the gas engine is just a range extender. At this point the power from the engine is completely buffered, and when running, the engine can always be exactly at its most efficient rpm and power output. This is not possible with HSD due to the geometry of the PSD.

HSD is so efficient primarily because buffering its power output allows it to run closer to its most efficient rpm and power output, and some of the torque can be provided by the electric motor. But a full EV gets all its torque from the electric motor(s) and a plug-in series hybrid has total buffering of power from the engine (when the engine is needed at all) and so can be even more efficient than HSD.

The Prius is the easiest car for a backyard mechanic to convert to PHEV because it has the control circuitry and the electric motors already. But it can only ever get about half its energy from gas. And because of the way it gets its best operation by using gas and electric together, it's not a good design for a PHEV built by a company that has the resources to design a PHEV from the ground up.

 

Do you know Prius history?
NHW-10 40 modules 76 kg
NHW-11 38 modules 52 kg
NHW-20 28 modules 45 kg
The HV battery becomes smaller and lighter, but vehicle performance and mileage are insreasing.
That's the innovation.

Ken@Japan

 

And yet wasn't it Wayne Brown who first put a second battery pack in a Prius (not plug-in) and without making any other changes achieved a significant increase in efficiency (fuel economy)?

Toyota improved the hybrid system so much that even with a smaller battery they improved FE, but Wayne Brown showed that with a bigger battery FE would be even greater.

Toyota, however, has to take cost into account.

 

Have you bought that Saturn Aura Hybrid that you raved about a year ago yet? Or are you still motoring about in a Prius.....

 

I think the main issue of confusion is that you are assuming I meant HSD in it's current form is going to be same HSD that will be utilized in the next generation of vehicles. In the end, I am not entirely convinced that the next set of vehicles will be full EVs based on a number of factors and that extended-range plug-ins are going to be around for longer than many EV proponents think.

I don't think what it was designed to do be in in first iteration is the same it is going to be 3 or 4 steps downs the road. Even in the test plug-in Pri that Toyota has used in Tokyo and the US allow for an EV mode (that is purposeful, not accidental at higher speeds and for longer distances with just more batteries and software changes as already discussed http://priuschat.com/forums/prius-hybrid-news/42499-plug-prius-display-info.html.

Now when electric vehicles due arrive, I can't speak to what changes will be necessary into HSD to make it able to be used in such a vehicle since I'm not an automotive engineer. However, Toyota's engineers continue to make changes to the HSD to make it closer to what most of us hope for, EVs that will virtually eliminate the need for gas on a daily basis. My assertion is that the HSD up to this point has depended on gas and electric together because that was the most cost effective way to meet the goals of range, emissions, and convenience. The test PHEV's made by Toyota are enough evidence to me that they still left the door open for EV travel for a significant distance.

 

70% to 80% of the barking force comes from the front brakes. The regen system of the prius can slow the car without using the rear brakes. If you move the regen system to the rear, you'll have to make more use of the front brakes. Plus, there will be less energy for the system to capture at the rear.

You can have full EV with HSD, but with motors and engine physically geared together there will be losses with the engine being spun. You can include a clutch system to disengage the engine when it isn't needed. That's just something else to break, where as, the series hybrid already has the less moving parts advantage. The series hybrid genset also runs at peak efficiency 100% of the time. While minimized, the HSD engine still undergoes variable loads.

 

HSD is Toyota's brand name for the hybrid system used in the current generation Prius (2004 to present). The 2001, a very similar hybrid, was not HSD. It was called THD. The next generation hybrid, if it incorporates any significant changes other than software, will probably get a new brand name.

When I use the term HSD I am referring to specifically the design of the present Prius, because that seems to be what Toyota means by the term HSD.

Some posters above seem to feel that HSD is any hybrid from Toyota, even if it eliminates the PSD and puts motors in all 4 wheels.

My point above was that the Prius as presently designed (i.e. what Toyota calls HSD) is ill-suited to the transition to pure EV. I believe that the ideal EV has wheel motors, and this by definition is not HSD.

 

The Prius, in this old engineers opinion, is not a stop-gap measure, as previous posters have termed it. It is however, a transitional engineering solution in the effort to move beyond the oil dependence we
(in the industrialised countries) have become addicted to, especially with respect to transportation.

The engineering and economic constraints that had to be considered by Toyota in developing this car for the mass market were incredible, and they deserve accolades for the vehicle in its current form.

Of course it can be improved! Hell, the ICE has had 150 years of development behind its current incarnation, thanks in no small part to the availability of cheap oil; the Toyota Prius, as a workable concept, has had 10 years so far; it will improve!

The real constraint, as I see it, is the fundamental mismatch between the amount of energy that is packed into a gallon of gasoline, compared to the amount of electrical energy that can be packed into an equivalent battery volume. Right now, the energy ratio, however you measure it, is of the order of 100:1. In addition, that energy has to originate somewhere; the other question is where and how is it best and most efficiently produced?

Until battery storage capability (or its electrical equivalent ) is significantly enhanced, without excessive weight, volume, cost, safety, design or durability penalties, Toyotas hybrid approach will gain traction as battery technology improves, with increasing emphasis on the EV mode, but with the ICE in a support role for reasons of range and reliability.

ron

 

Toyota's current approach (HSD) is ideally suited for a car that runs entirely on gasoline or other liquid fuel. I continue to believe that a plug-in hybrid, which gets a significant portion of its energy from the grid, and only uses a gas engine as a range extender for infrequent longer trips, would be better if designed as a series hybrid.

 

The distinction makes sense, which is why I never said HSD until you kept mentioning it by name. When the debate started, I was referring to full hybrid systems, not just the current HSD. So to be fair, you seemed to be clouding the waters before other people got into using HSD. It really doesn't matter what the name changes to, if it is HSD III or some other designation, people see full hybrids as being able to be more than just a stop gap.

 

I'm not talking about removing the power split device. MG2 is directly geared to the wheels, there is always a constant ratio between the wheels and MG2, so by putting MG2 in the back wheels MG2 will still be turning at a speed directly related to wheel speed so no need for a clutch.

Maybe my idea is a little floored, what about two 15kW motors in the rear wheels and a smaller, say 30 or 40kW MG2 in the transmission. 3 channel traction control could send power to the wheels with the most grip and if there was front wheel spin de-power or generate power from MG2 to send to MG3 and 4 in the back wheels.

Daniel, why must an EV have wheel motors? Why not 1 motor and a conventional differential? I know there is no need for a gearbox with high torque electrics but if a differential is simpler or cheaper than a second motor, why not? Even MG2 with huge amounts of torque is geared down to drive the wheels so a drive train of some sort makes sense to me for shaft speed reduction and torque multiplication for a smaller high speed electric motor.

 

Notice how no one has actually clearly defined what the heck "stop gap" actually means?

It's a term coined with the specific intend of undermining the progress of hybrids. But at this point, it's pretty easy to argue that want having backfired. Using it originally implied a "temporary" solution. But now, enough time has went by since its origin that people are looking to replace their old hybrid with a new one. That transistion to next generation wrecks the idea of being "temporary".

Look at the economy now. Prius is already established as a mainstream solution. Sales will remain strong. Who's going to accept the idea that it isn't something which will continue to be available?

.

 

You originally said, " Why couldn't HSD mk II have 2 wheel motors on the back wheels of 25 to 35kW each to replace MG2 within the HSD?" I took to mean you were moving the MG2 in a way that left it disconnected from the PSD and thus the front wheel drive train. Without that connection, then the MG2 can't help with the front braking, and it was my understanding that it was the main dynamic brake in the Prius. So unless you intend have the MG2 still connected to the front wheels some way or enlarge the MG1 for braking, you have decreased the regen braking of the car and all its benefits for AWD.

The Highland AWD hybrid uses a third motor in the way you suggested, but we come to the fact that most people do not need AWD. It's a drain on efficiency for a sometimes benefit. You're increasing weight and drive train drag. As of now, the Prius can't capture all the energy in the current regen braking. Having it at the back also isn't going the net more recovered energy in the current system and batteries.

I think there might be weight savings and definite space savings when using hub motors, but they'll just add cost to a pure EV. The space they save might be more useful to a series hybrid for the genset.

 

You are right. I brought up HSD to make the point that in my opinion a series hybrid is a batter match for the transition to PHEV than is the system used presently by Toyota.

I am of the opinion that simpler is better, and I believe that wheel motors are simpler because they eliminate all the mechanisms for transferring power from motor to wheels.

Also, the system presently used by Toyota was designed from the ground up to integrate a gas engine with the battery and electric motors in a vehicle that gets all its energy from gasoline, and in which therefore it is intended that the gas engine runs nearly all the time, only shutting off at very slow speeds or when the battery is too full.

It is my opinion that a different design is preferable for a car intended to operate most of the time as an EV, which only uses the gas engine as a range extender. One of the principal ways Prius is superior is that the gas engine can run closer to its ideal RPM and power output. But in a series hybrid the gas engine need run only at exactly its ideal rpm and power output. But once you've done that, there is no longer any need for mechanical power transmission, and the motors can be in the wheels. This will also allow a whole new level of traction control, without any of the drawbacks some Prius owners have complained of.

You ask: What if mechanical power transmission turns out to be cheaper or more efficient? I argue that it is not. This is just my opinion, based on the notion that simpler is better.