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From: Don Y <blockedofcourse@foo.invalid>
Newsgroups: sci.electronics.design
Subject: Re: Speed limiters
Date: Sun, 7 Jul 2024 09:57:50 -0700
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On 7/7/2024 9:08 AM, KevinJ93 wrote:
> On 7/7/24 9:00 AM, Don Y wrote:
> <....>
>> Nothing for the cruise control touches the brakes.  It relies on the engine to
>> slow the vehicle.
>>
>> There are newer "collision avoidance" systems that will actively brake
>> if they sense you're approaching an object with which you may collide.
>>
>> Newer cruise controls will adaptively adjust speed to prevent you from
>> creeping up the backside of the vehicle in front of you.
> 
> <...>
> 
> Many adaptive cruise control systems (but not all!) have full authority down to 
> zero-speed; they control the brakes as well as the throttle.

This ---------^^^^^^^^^^^^^^^^^^^^^^^ is the difference between them and legacy
"cruise control" systems.  It can only control the vehicle's speed to the same
degree that a human can /with just the throttle/.

In The West, it is not uncommon to find yourself driving through varying
elevations (mountains).  Relying solely on the engine for braking often
won't allow you to comply with the posted speed limits *or* "safe driving
conditions".

[OTOH, being overly reliant on the brake can lead to brake overheating and
failure]

> This is separate from any collision avoidance functions.
> 
> Some adaptive cruise control systems (on for example older Audi and Nissan 
> vehicles) disengage at speeds around 10-15mph and just leave the car rolling 
> without any control. If you did not takeover they could collide with anything 
> in front.

I've not seen the limits for adaptive controls; whether they refuse to engage
at lower speeds AT ALL.  But, this would be consistent with legacy systems.