GM-VOLT : Chevy Volt Electric Car Site

Electric cars are silent-running which for many people is a very good thing.  It can potentially lead to some risk to the visually-impaired and other pedestrians however as some studies show.

A study by the  National Highway Traffic Safety Administration published in September reveled bicyclists and pedestrians are struck at a significantly higher rate by hybrid as opposed to conventional cars.

GM has created a special pedestrian alert signal for the Chevy Volt.  ”It is an active system,” says Chief engineer Andrew Farah, meaning the driver must activate it.  Passive systems produce a sound at all times.  The Volt pedestrian alert sound is a light volume horn-like sound similar to the chirp of some cars keyless entry indicators.  ”It has to be automotive,” says Farah referring to the  quality of the tone.

The fist generation Chevy Volt will not be equipped with a passive alert system.  Competitor Nissan has reportedly developed a system for its upcoming LEAF EV which sounds like a floating car from the Bladerunner movie. GM is looking at the possibility of passive alert for future Volt generations.  Other electric automakers such as Tesla remain uncertain.

Today GM has announced that they formed a partnership with the National Federation for the Blind to identify what will be a “safe level of sound” for alerting visually impaired and other pedestrians to the approach of a silent running EV.

Meetings have begun earlier this year and are also aimed at protecting runners, cyclists, and children.

“We have significant background in the area of pedestrian alerts dating to our work on our first electric car, the EV1,” Farah said, “The most important thing is to listen to the people who will interact with these vehicles in everyday life.”

Deborah Kent Stein, who chairs the NFB’s Committee on Automobile and Pedestrian Safety, said, “A recent report from the National Highway Traffic Safety Administration (NHTSA) demonstrated that the silent operation of hybrid vehicles is an issue for all pedestrians, not just the blind. In certain situations, electric or hybrid vehicles are twice as likely to be involved in collisions with pedestrians. The NFB looks forward to working with the safety agency in the crafting of appropriate standards establishing an acceptable level of minimum vehicle sound.”

“The National Federation of the Blind appreciates the opportunity to work with General Motors on this problem,” said Dr. Marc Maurer, president of the National Federation of the Blind. “We urge all automobile manufacturers to work with the blind in designing vehicle sounds to alert us to the approach, speed and direction of vehicles so that both drivers and pedestrians can safely use America’s roadways.”

A low-level low-speed vehicular sound for EVs may be inevitable, though no formal federal regulations currently exist. Future legislation may arise in concert with input from the Society of Automotive engineers to develop a national standard.

A lack of consensus and standards among automakers could conceivably result in a virtual cacophony of discordant sounds once streets become filled with EVs from various automakers.  Thus all cars should produce similar sounds, likely ruling-out the possibility of customizable “car tones,” as some pundits have speculated about.

Like it or not, the sound of silence appears to be on its way.

Below is GM’s video on the sound of the Volt:

The two recent media test drives of the Chevy Volt’s in charge sustaining mode were seen as positive by 85% of GM-Volt.com readers.

Both reporters mentioned however that they could occasionally notice the generator revving after charge sustaining mode was well under way, though neither coud detect it when it first came on.

I was able to communicate with one of the reporters, Lindsay Brooke of the New York times, about his experience.

“Yes, when the ICE first kicked in (on an uphill climb) I could neither hear nor feel its engagement,” he said. “It was completely seamless. I only noticed it because I was keeping a close eye on the cluster—the icon noting battery charge changed over to the icon showing a gas pump which denotes the switchover and how much range remains using the generator.”

“The reason the ICE generator engages at random times is due to its current control regimen for charge-sustaining mode,” he said. “As the quote from Tony noted, the controls engaged the generator, then shortly thereafter called for another of the pre-set charging speeds (rather like, “Oops, I needed more juice than I previously anticipated.”).”

“It was not in situations where I was flooring the pedal, which as you know has no connection to the ICE’s throttle control. Nor was it necessarily in heavy-load situations. A couple times the ICE engaged when the car was going downhill, under what would be light load in a conventional vehicle,” he said.

Brooke added, “I think we’ll be pleasantly surprised when we drive the production-spec car.”

Andrew Farah, the Volt’s chief engineer explained to GM-Volt,” there are still points at which operation of the engine generator is more aggressive than we want it to be, and we want to make it operate less aggressively.”

He says the engine never generates more power than the car needs but may generate it more quickly than necessary. Engineers are able to vary power production by both varying the engine’s RPM and its load, and that along the RPM-load plane there is the third dimension of efficiency which has to be taken into account.

These variables are distinct from the NVH (noise-vibration-harshness) component which is what the customer actually perceives. The team must work within the constraint boundaries of the “NVH ceiling” at the high end and the permissible limit of dip into the battery reserve at the low end to achieve the lowest NVH possible at all times.

It is still at this point a work in progress.

Farah also notes that they don’t let the engine to run at all at low speeds because there is less ability to mask its noise.

Overall, 99% of driving in the integration prototypes is without audible engine noise, there are rare ocassional spikes of sound that the reporters noticed, which will be ironed out in time for production.

I had a discussion with Alex Cattelan, the Chevy Volt’s chief powertrain engineer about the engineering design and operation of the Chevy Volt’s charge sustaining mode.  This is the mode that occurs after the car has depleted the first 40 miles of  range and the gas generator has begun providing electric power.

When you first unveiled the Volt and it was a math model, the car was promoted as getting 50 MPG in generator mode. Now that there are real world parts and parallel hybrid like the Prius verse series. Can you speak about the efficiency difference between series and parallel hybrid operation?
We’re tuning our fuel economy right now. From an architectural perspective there are differences between series and parallel hybrids , there’s absolutely no doubt about that. The issue you mentioned the Volt is a series hybrid when we go into charge sustaining mode or when the engine comes on. We like to think of it not as a hybrid. You’ve got to understand that all of the decisions that we’ve made around this product are made because its an EV. That is the first and foremost thing that it needs to be. So because it is an EV some of the decisions that we’ve made around engine operation will be different than what Toyota makes in its parallel hybrid. For them they are always operating in hybrid mode so they need to optimize everything for engine operation.

In our case we’re optimizing everything for EV operation and the secondary is certainly going to be better than conventional vehicles, but were not necessarily totally optimizing the system for charge sustaining mode because we don’t want to compromise electric vehicle mode.

So to be optimally efficient in charge-sustaining mode you might compromise EV performance?
In the electric vehicle mode, and its not just performance, its efficiency in electric vehicle mode that we’re optimizing.

You mean those first 40 miles?
Right, so you’ve got to remember our principle promise is this is an EV and our engine is there as a range extender and so even when the engine is on, we operate as through we are in EV. All the primary propulsion is satisfied by the electric motor. The engine is really there to supplement power to keep the battery sustained. Now there are a couple of tricks of the trade that we do since we have the engine on more, but for example we don’t want to do a whole lot of gearing that you would do in a parallel hybrid, because none of that is beneficial to you in the EV state.

But doesn’t the fact that you could keep the engine at fixed RPMs also allow you better efficiency?
Actually we don’t keep it at a fixed RPM, we have a window of operation that is optimized. We have been able to optimize the engine for a window of efficiency but it is still best to charge your power and torque levels within that window as the customer torque request varies. We don’t want to always be operating at one state because really you may be putting too much energy into the battery or drawing too much energy out of the battery. It is still good to vary that engine power and torque. Not to follow exactly what the accelerator pedal does, but to optimize efficiency.

We actually have a very sophisticated efficiency calculator in our model within our software. It calculates on a very very short time scale what the driving conditions of the car are. Which mode you are in, whether you turning you engine on or off, and what power and torque you want to run than engine always with the optimization of efficiency in mind as well as managing trade offs for driveability and noise.

We took all of the model that’s in the two mode hybrid and we’ve basically been carving out pieces we don’t need, adding in pieces we do need for this architecture and optimizing that model for this particular vehicle. We didn’t build this from scratch, this is also software that we are using that is also on the 2-mode but we are modifying it for optimizing this architecture.

I’ve driven the 2-mode and notice you can see the switched in mode of operation without feeling it in the car.
Which is the goal, you don’t want you to feel it in the car, we don’t want the customer to know these transitions are taking place, but we need to be able to enable them for efficiency.

With the Volt, once you’re in CS mode you will have a few different windows of operation or just one window for the generator?
We’re optimizing the generator to have different power generating levels. But the beautiful piece of being able to decouple the engine or generator from the axle torque requirement is we can travel along and hit those power levels that we need to optimize the system for battery charging and discharging, we can maneuver across them at any rate of change we so choose.

So think of it as the beauty of being able to decouple the engine is we have a degree of freedom that we don’t have to follow the pedal at all. We can pick and choose the points that are most efficient, we can go between those point on the best path and the most pleasing path to the customer. Actually this is a lot of the work we are doing even on a Prius hybrid every hybrid does it to some extent but every engine is required to follow the pedal. It is much more coupled to the axle torque request than in our vehicle.

It seems to me then you should make CS mode even more efficient then in a car where the engine always has to turn the axle?
Right and it is more efficient than a conventional vehicle because they do have to have that engine coupled. Again were optimizing some of those efficiency point puts we are really doing is focusing on the optimization of the EV. There are trade offs because we absolutely consider this product an EV by nature.

I recently participated in a segment for the NBC Nightly News in the New York tri-state area. The piece is also being nationally syndicated.

The main thrust of the story was to illustrate how electric cars have already arrived on the streets and that in fact now is just the tip of the iceberg.

The reporter and I tooled around in my MINI E electric car and we discussed why it is important to me to drive on electricity.

I also took the opportunity to explain the concept of range anxiety and the value of the Chevy Volt.  According to BMW’s Rich Steinberg only two out of 450 MINI-E drivers have actually run out of charge to the point of needing to be towed, but also points out the car has a limp-home low power feature when for when battery level becomes critically low..

You can watch the video segment in the viewer below:

There is also an accompanied written story by the reporter Brian Thompson here.

Chevy Volt LCD Screen

It’s hard to believe after nearly three years of debate we have finally gotten some independent third party observations on what its like to drive a production-intent Chevy Volt in charge sustaining mode.

I thought it would be good to review and summarize what the reviewers said, seek some clarification from GM, and see what we all think of it.

Acceleration
LeBeu: low center of gravity and “sportier” feel when accelerating, not a sports cars, instant torque gives you responsiveness, will surprise skeptics
Brooke:sport mode delivers more oomph than normal mode

Handling
LeBeu:great handling that would surprise skeptics
Brooke: car feels solid and planted on the road, minimal body lean in tight corners, low rolling resistance tires provide excellent grip

Transition from EV to CS Mode:
LeBeu: transition is disconcerting, needs to be smoothed out, no fall off in power, jarring
Brooke:engine’s initial engagement is inaudible and seamless

Sustained CS Driving  Requiring Power
LeBeu: N/A
Brooke: intermittent momentarily disconcerting engine revs with immediate disappearance of sound even though generator still spinning

Instrument Panel
LeBeu: loves green to yellow efficiency gauge, overall great
Brooke: N/A

Overall Impression
LeBeu:  very impressed
Brooke: behaves admirably, extremely refined

I had the chance to discuss these journalist drives with Volt vehicle line executive Tony Posawatz who explained things the following way:

Both Phil LeBeau and Lindsay Brooke had wonderful drive experiences. I was in the car with both of them for their drives.

Neither was able to detect when the engine came on, much different than a hybrid. We are still fine tuning aspects of how the engine modulated under different load conditions.
We want to make it perfect. We have the unique challenge of balancing the customer pleasability, efficiency and regulatory requirements.

The engine has certain RPM efficiency points but does vary when you demand more power. Our work now is to feather in the RPM changes and refine which is simple calibration work.
The charge sustaining or range extending experience will be somewhat different to what people are accustomed to just like EV driving is a different experience.
Most of the time you will never know the engine is on.

On the same day the Today Show ran its piece on test driving the Chevy Volt integration prototype, Lindsay Brooke, a reporter from the New York Times published his.

Brooks was the only other journalist so far besides CNBC’s Phil Lebeau to test drive the Volt in generator or charge-sustaining mode and has written about it.

His brief article entitled Life After 40 tells us what we’ve been waiting to hear, but maybe not exactly what we wanted to.

Brooks writes:

Like other reporters, I had already driven Volt prototypes in the battery-powered mode, and they were predictably smooth and silent. But for eventual Volt owners, a crucial — and so far unanswered — question is how the car will perform when the battery’s charge is depleted and all electricity is provided by an onboard generator, driven by a gasoline engine, that has no mechanical connection to the wheels.

Then as he runs the car’s electric range meter dramatically down to the zero mark, the moment we’ve all been waiting for occurs:

With the dashboard icon signaling my final mile of range, I point the Volt toward a hill and wait for the sound and feel of the generator engine’s four pistons to chime in. But I completely miss it; the engine’s initial engagement is inaudible and seamless. I’m impressed.

Good so far.  He finds that as he pushed the accelerator, the sound of the engine didn’t change.

But later as he’s accelerating around the test track he gets a little shock that he calls disconcerting.

A few hundred yards later, as we snake through the track’s infield section, the engine r.p.m. rises sharply. The accompanying mechanical roar reminds me of a missed shift in a manual-transmission car. For a moment the sound is disconcerting; without a tachometer, I guess that it peaked around 3,000 r.p.m.

He asks GM’s Tony Posawatz driving with him what just happened.

“The system sensed that it’s dipped below its state of charge and is trying to recover quickly,” apologizes Posawatz. “The charge-sustaining mode is clearly not where we want it to be yet.”

Huh?

He goes on to write:

Immediately the engine sound disappeared, although it was still spinning the generator. A few times later in our test, the generator behaved in similar fashion — too loud and too unruly for production — but there is time for the programmers to find solutions.

So there we have it, the first reporter in history to write about the Volt’s operation in generator mode, and its a bit of a mixed picture.

It seem to go on flawlessly but throughout driving apparently has spikes of on/off engine roars that he finds disconcerting and unruly.

Though not exactly a happy report, he concludes:

Throughout my test, the prototype behaves admirably. At its current state of development, the Volt is an extremely refined vehicle.

Looks like GM has a little more work to do.  But then again the experience may be a bit subjecttive.  We’ll wait to see what others have to say.

Source (New York Times)