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Discussion Starter #1
I tested the lane assist today - yes the wheel nudges me back into the center, along with a audio/visual warning. Haven't tested the braking yet, not sure how to do that safely.

Anyhow the 2018 Leaf is coming out with all sorts of autonomous features. Self parking (it really controls the wheel) and such. So I'm wondering, does anybody really know the capabilities of the steering wheel and braking control? For instance, is it possible they could OTA us self parking?

It seems that the steering and braking control are fully capable - that is I would doubt they installed just enough control to nudge the brakes and wheel. No, the way any engineer and team would do this is buy a standard wheel and brake control unit, then just to be cautious have the initial feature just barely use them, just to test the waters, while you develop more powerful features.

Don't know whether it's true but on a Volt forum it's been floated that the Bolt uses the Bosch iBooster system, which is capable of customizable braking (e.g. sport and standard), regenerative and autonomous braking. Given we know we have these features it isn't unlikely that this is the system we have. Any hints? Has anybody looked at the hardware?


 

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Discussion Starter #2
Some clarification on "Blended Braking". Doing some research I believe the following is true, please correct with anything you know better

  • Blended braking (in the Volt and Spark) is a type of brake where you get a continuous ramp between braking and regen. It starts off (probably) as full regen, then goes to full braking at the end of the depress.
  • The Bolt has more of a 'stair step' braking, when you first brake it's applying regen, then it shifts to brake pads.
  • This is probably because the Bolt is designed for aggressive regen, with L and the regen paddle, you can come to full stop on regen, unlike the Volt/Spark (my Volt friend commented on the aggressive Regen of the Bolt, he wishes he had it)
  • So GM probably figures Bolt drivers will generally use the brake only when they really need brake pads, hence the stair step function.
  • This is probably a pure software function that was not a hardware decision. Clearly with the iBoost and rest of the system they could have had it be more of a 'blended brake', which doesn't make much sense on the Bolt which is a pure long range BEV.
So that's my take on blended braking, it's a software enabled feature that Josh (lead Engineer) and team felt wasn't something they wanted to saddle us Bolt owners with, and I agree. The Bolt drives better with a either/or approach, either use aggressive regen or use the brakes when you need them. Now on to adaptive cruise control


  • I don't see any reason why blended braking is a necessity for ACC
  • On the Bolt, with iBoost braking the system could work in either L or D modes, the key being its ability to come to a full stop, either with regen or not
  • The Bolt appears to be using cameras and not any radar system for proximity detection. The question is whether this is sufficient for ACC
 

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Discussion Starter #3 (Edited)
Here's a somewhat more technical pdf of the device.

In there you can see an example chart of various ramps the designers can choose, from sport to comfort. Then down to the "Design of the iBoosters" you see the "EC motor", this is a energy efficient "electronically communicated" motor, basically it's a DC brushless motor controlled by a circuit, which allows fine tuning. The gearing (whatever it happens to be) gives a nice ratio between the motor and the brake.

So that's what is giving us the pedestrian braking, and which can give us more autonomous features. Something I thought of though is that GM is giving us hard buttons for many features (lane assist, sport mode, etc) and software settings for others (e.g. low speed pedestrian avoidance). Supposing they gave us some ACC with using just the cameras, there wouldn't be a hard button for it. Thought theoretically it could be enabled by some extra use of the steering wheel buttons, say pressing the center "Avoidance distance length", when in CC, to enable ACC.

Specifically from the PDF
Driver assistance
The electromechanical design of the iBooster also offers a host of bene ts for driver assistance systems. Using the electric motor, the iBooster can build up pressure independently, without the need for the driver to apply the brake pedal. Compared with typical ESP® systems, the required braking pressure is built up three times more quickly and is adjusted with much greater accuracy through the electronic control system. This o ers signi cant bene ts for automatic emergency braking systems, for example. In a critical situation, the iBooster can automatically build up the full braking pressure in approximately 120 millise- conds. This not only helps to shorten braking distan- ces, but, if a collision is unavoidable, it also helps reduce the impact speed and risk of injury to all parties involved.

In addition, the iBooster can ensure comfortable deceleration when adaptive cruise control (ACC) is active until the vehicle has reached a standstill — and it generates virtually no noise or vibration in the process. This is a signi cant bene t for quiet electric vehicles, as ambient sounds are much more noticeable in these vehicles.

Automated driving
In combination with the ESP® from Bosch, the iBooster provides the braking system redundancy required by automated vehicles for safety reasons. Both systems have a direct mechanical push-through mechanism on the brakes and can brake the vehicle independently over the entire deceleration range.
Interestingly the Tesla 70D also uses the iBooster, so it's probably the standard for EV's and braking assist.

Well that enough on the brakes, now we need more information on the steering control hardware.
 
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