Josh Tavel, Chief Engineer
"Adaptive cruise control – no, you would need the blended brakes to do that and we didn’t want to do that with this car."
And some learning for myself - one pedal it! The Bolt is not a Volt.
Bolt EV brake pedal operates hydraulic brakes and does not have a blended braking system.
And why no blended braking?
There has been complaints about what a Volt does when one front tire hits a slick surface, or you go into ABS mode. The regen shuts off completely and gives the illusion of a brake failure, which isn't what is happening.
Way back when the discussion of the missing ACC in Bolt started many months ago, the "lack of blended braking" as the reason for the omission did come up when the quote first appeared. Not to discount the claim, as it is basically an official rationale, but it seemed strange in a way.
Now, blended braking is mixing both regenerative braking and physical braking at the same time. You reclaim as much energy as possible with regenerative braking, while the physical brakes augment the deceleration force. Manually controlled, I remember Bolt EV being able to do blended braking - try coming to a quick stop by using both the regen paddle and the brake pedal and and I think the the power level still goes into regen, meaning both are at work.
What about the autonomous control? Bolt's ability to both make use of regenerative braking to keep speed constant in the cruise mode and execute emergency braking via physical brakes show that both types of brakes are autonomously controllable. It's then a matter of whether the system is willing to apply both at the same time as needed. What I see from the quotes is that this is not the case.
But I'm still unsure as to whether the such operation is truly crucial to make "adaptive" speed control possible. Wouldn't it still be possible with "either/or" mode (i.e. non-blended braking) anyway? Then it's more of a matter of having reliable awareness of the surroundings to make the right braking decision. And since Bolt has less sensors to work with than Volt, it's reasonable to suspect that the final decision swung to not including the ACC, to err on the side of safety.