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Discussion Starter #1
I wonder if GM's Engineers would consider a different application for the "gas" pedal. Instead of a depression of the pedal being a call for additional power, how about a call for higher speed. That way constant pedal equals constant speed. Going down hill the system would use regenerative braking to maintain the speed called for by the pedal depression.
 

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that sounds like a cool/interesting concept, but if the Volt doesn't drive like a "regular" car it will hurt the overall success. people don't want to re-learn how to drive, they just want to stop paying so much for gas.
 

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Ambiguous velocity vs. well defined acceleration.

I wonder if GM's Engineers would consider a different application for the "gas" pedal. Instead of a depression of the pedal being a call for additional power, how about a call for higher speed. That way constant pedal equals constant speed. Going down hill the system would use regenerative braking to maintain the speed called for by the pedal depression.
One of the problems with this idea is that there then is no way to command how quickly the vehicle gets to the commanded speed. Another problem is loss of meaningful control range. For example, say you depress the pedal 3/4 down to command 90 mph. If you have 4 passengers going up a 15 degree road grade you'll never get to commanded speed. You press down further on the pedal, nothing happens. So 1/4 of your control range is meaningless.

An accelerator pedal has no such ambiguity. 50% down is half max acceleration and full down is max acceleration.

Tom
 

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I think that the accelerator pedal should command acceleration.

The question to me is what happens when you let go of the accelerator pedal. I'd like to see the car coast down hills (no regen) until you tap the brake, at which time it would enter a mode where it would use regen to keep from going any faster than the current speed. This mode is very useful when decending steep grades - it gives the driver a feeling of control. The coast mode is great for efficiency, and gives the driver a feeling of freedom.
 

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Discussion Starter #5
I think there is a missunderstanding of the suggested speed control.
The acceleration force for the "speed control" system would be a function of the difference between the speed requested by the pedal depression and the vehicle speed at the time. As such, the acceleration operating characteristics for a speed control would be indistiguishable from the characteristics of the conventional accelerator system.
Assuming the speed control system was programed to provide mild deceleration when the pedal was eased or released, the operating characteristics of both types of control would be identical except when the vehicle was going up or down hill.
When a vehicle with a conventional system starts up a hill, the accelerator must be further depressed to maintain a constant speed. with a speed control that would not be necessary. I doubt that many people would object to that feature.
Speed control going downhill would be more controversial. When a conventional system starts downhill one backs off on the accelerator to maintain a constant speed. When the slope becomes steeper the driver loses control of the speed untill he moves his foot to the brake pedal.
With a speed control the system would automatically reduce power and apply regenerative braking as required to maintain the requested speed. This would be a significant departure from present operating conditions but I suggest would be a safer mode of operation.

RLM
 

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I would rather not have regen automatically kick in when going down a hill, because maybe you wanted to increase speed, and regen is not as efficient as coasting. 80% from battery to wheel, multiplied by 80% from wheel to battery, gives 64% round trip efficiency. Better to coast up and down with the hills for efficiency, and if you have to hold down the accelerator pedal to reach this glide point, then most people will not bother.

Therefore, it seems to be better to give the operator the choice of glide or regen down hills, by engaging the regen only when the brake pedal is tapped.
 

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Isn't what you're suggesting just cruise control? I'm sure it will have that.
 

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Isn't what you're suggesting just cruise control? I'm sure it will have that.
That's not what I was talking about at least. The question I'm addressing is what happens when you let off the accelerator pedal when going down a hill. There are a lot of similar questions that come up with EVs. For instance, should the car creep forward at low speed when you let off the accelerator pedal? Certainly, the car should not slip backwards on a grade, for safety reasons.
 

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That's not what I was talking about at least. The question I'm addressing is what happens when you let off the accelerator pedal when going down a hill. There are a lot of similar questions that come up with EVs. For instance, should the car creep forward at low speed when you let off the accelerator pedal? Certainly, the car should not slip backwards on a grade, for safety reasons.
Yeah, I know. I was addressing the OP but failed to state that. However, why would anyone want the car to creep forward with your foot off the gas? That's just an annoying byproduct of current automatic transmissions with idling ICEs. This car should have no reason to do that. The hill holding feature is very possible. There are companies offering that now and it's not too tough to do. On the other hand, I've been driving manual transmissions for decades and don't really need it at all, so hopefully it can be an option.

The control on the regen braking is something I've wanted all along. I'd like to have a switch on the steering wheel so I can activate some amount of preset braking to use like I use engine braking in a manual car now. I think it should be freewheel when you take you foot off the gas and don't touch the brake, regen only when you use the button (possibly with user presets) and regen with friction brakes when you use the brake pedal.
 
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