Many years ago, in Schenectady New York, I got into a pace line of
automobiles.

It was exhausting! I had to stand up on the pedals and brake at the
same time -- each driver would go a wee tiny bit faster than the car
ahead until he got too close, then go a wee tiny bit slower until he
felt the need to close the gap. He couldn't *match* the car ahead,
because that car, too, was wobbling to keep an on-the-average
comfortable space.

I rather suspect that cruise control also hunts, just as thermostats
do, feeding more gas when the car falls below the set speed, feeding
less when it is moving faster.

--
Joy Beeson
joy beeson at centurylink dot net
http://wlweather.net/PAGEJOY/

On 3/26/22 11:29 PM, Joy Beeson wrote:
>
> Many years ago, in Schenectady New York, I got into a pace line of
> automobiles.
>
> It was exhausting! I had to stand up on the pedals and brake at the
> same time -- each driver would go a wee tiny bit faster than the car
> ahead until he got too close, then go a wee tiny bit slower until he
> felt the need to close the gap. He couldn't *match* the car ahead,
> because that car, too, was wobbling to keep an on-the-average
> comfortable space.
>
> I rather suspect that cruise control also hunts, just as thermostats
> do, feeding more gas when the car falls below the set speed, feeding
> less when it is moving faster.
>

Used to be you had to keep cancelling/resuming the cruise control of the
vehicle in situations like that, which, over a period of time, ends up
having a driver (me) just turning the thing off.

Now days they have "adaptive" cruise control that will automatically
slow the vehicle up then speed up when clear. No driver input other
than determining a setting of how close you want to get to a vehicle in
front of you before the system backs off the speed.

My vehicle is too old for such high tech but it sounds like a wonderful
feature to have in a vehicle if you frequently drive in higher speed
traffic.

SMH

On 3/26/2022 11:29 PM, Joy Beeson wrote:
>
> Many years ago, in Schenectady New York, I got into a pace line of
> automobiles.
>
> It was exhausting! I had to stand up on the pedals and brake at the
> same time -- each driver would go a wee tiny bit faster than the car
> ahead until he got too close, then go a wee tiny bit slower until he
> felt the need to close the gap. He couldn't *match* the car ahead,
> because that car, too, was wobbling to keep an on-the-average
> comfortable space.

I agree, few people can intelligently handle clotted queues of traffic.
When that situation comes up on a freeway - say, because construction or
a crash has everyone slowly funneled into one lane - I generally leave a
large gap between me and the car in front. That allows me to take out
the bouncing accordion effect. Occasionally someone behind me will get
impatient, but I either ignore that senselessness, or I slow down a bit
more. (Tailgaters are idiots.)

> I rather suspect that cruise control also hunts, just as thermostats
> do, feeding more gas when the car falls below the set speed, feeding
> less when it is moving faster.

I'm sure modern cruise controls operate on a P-I-D scheme. That's
proportional, integral, derivative - it's a complicated scheme used to
control lots of industrial processes. If properly tuned, it shouldn't
hunt up and down; it should quickly settle to the required throttle
opening for constant speed.

Having said that, the first car we had with cruise control, a 1994
Saturn, did "hunt" under certain conditions. Since it happened only very
occasionally, I never bothered to take it to the dealer. I do wonder if
they would have been capable of fixing it. PID tuning can be tricky.

--
- Frank Krygowski

On 3/27/2022 7:03 AM, Stephen Harding wrote:
> On 3/26/22 11:29 PM, Joy Beeson wrote:
>>
>> Many years ago, in Schenectady New York, I got into a pace line of
>> automobiles.
>>
>> It was exhausting!  I had to stand up on the pedals and brake at the
>> same time -- each driver would go a wee tiny bit faster than the car
>> ahead until he got too close, then go a wee tiny bit slower until he
>> felt the need to close the gap.  He couldn't *match* the car ahead,
>> because that car, too, was wobbling to keep an on-the-average
>> comfortable space.
>>
>> I rather suspect that cruise control also hunts, just as thermostats
>> do, feeding more gas when the car falls below the set speed, feeding
>> less when it is moving faster.
>>
>
> Used to be you had to keep cancelling/resuming the cruise control of the
> vehicle in situations like that, which, over a period of time, ends up
> having a driver (me) just turning the thing off.
>
> Now days they have "adaptive" cruise control that will automatically
> slow the vehicle up then speed up when clear.  No driver input other
> than determining a setting of how close you want to get to a vehicle in
> front of you before the system backs off the speed.
>
> My vehicle is too old for such high tech but it sounds like a wonderful
> feature to have in a vehicle if you frequently drive in higher speed
> traffic.

My brief experience with adaptive cruise control (a rental car I had for
a few days) was less than satisfactory. Here's why:

On normal cruise, if I'm doing 70 and come upon someone doing 65 (i.e. 5
below the limit) my car begins to approach them, and I signal and change
lanes to pass.

With adaptive cruise, I found that my car would gradually decelerate
with no notification. I'd find myself following the slow driver, 5 below
the limit.

It wasn't a disaster, I guess, but I prefer to make the decision myself.

--
- Frank Krygowski

On Sat, 26 Mar 2022 23:29:40 -0400, Joy Beeson
<jbeeson@invalid.net.invalid> wrote:

>
>Many years ago, in Schenectady New York, I got into a pace line of
>automobiles.
>
>It was exhausting! I had to stand up on the pedals and brake at the
>same time -- each driver would go a wee tiny bit faster than the car
>ahead until he got too close, then go a wee tiny bit slower until he
>felt the need to close the gap. He couldn't *match* the car ahead,
>because that car, too, was wobbling to keep an on-the-average
>comfortable space.
>
>I rather suspect that cruise control also hunts, just as thermostats
>do, feeding more gas when the car falls below the set speed, feeding
>less when it is moving faster.

There is a minimum cruise control speed for older cars with cruise
control:
<https://www.quora.com/What-is-the-minimum-speed-required-for-a-cars-cruise-control-to-operate>
It varies by manufacturer, but mostly it's mostly around 25 mph. For
example, if you're crawling forward at 5 mph, the cruise control
cannot be turned on. If you're driving at over 25 mph, it can be
turned on. The exceptions are some of the modern electric/hybrid
cars, where the cruise control minimum speed is zero. For these, you
can be going any speed and activate the cruise control. If you want
to crawl forward at bumper to bumper speeds, buy a Tesla.

--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

On 3/27/22 1:57 PM, Frank Krygowski wrote:
> On 3/26/2022 11:29 PM, Joy Beeson wrote:
>>
>> Many years ago, in Schenectady New York, I got into a pace line of
>> automobiles.
>>
>> It was exhausting!  I had to stand up on the pedals and brake at the
>> same time -- each driver would go a wee tiny bit faster than the car
>> ahead until he got too close, then go a wee tiny bit slower until he
>> felt the need to close the gap.  He couldn't *match* the car ahead,
>> because that car, too, was wobbling to keep an on-the-average
>> comfortable space.
>
> I agree, few people can intelligently handle clotted queues of traffic.
> When that situation comes up on a freeway - say, because construction or
> a crash has everyone slowly funneled into one lane - I generally leave a
> large gap between me and the car in front. That allows me to take out
> the bouncing accordion effect. Occasionally someone behind me will get
> impatient, but I either ignore that senselessness, or I slow down a bit
> more. (Tailgaters are idiots.)
>
>> I rather suspect that cruise control also hunts, just as thermostats
>> do, feeding more gas when the car falls below the set speed, feeding
>> less when it is moving faster.
>
> I'm sure modern cruise controls operate on a P-I-D scheme. That's
> proportional, integral, derivative - it's a complicated scheme used to
> control lots of industrial processes. If properly tuned, it shouldn't
> hunt up and down; it should quickly settle to the required throttle
> opening for constant speed.
>
> Having said that, the first car we had with cruise control, a 1994
> Saturn, did "hunt" under certain conditions. Since it happened only very
> occasionally, I never bothered to take it to the dealer. I do wonder if
> they would have been capable of fixing it. PID tuning can be tricky.

A long time ago, a friend of mine bought a Sears cruise control to add
to her Chevy Impala. It would do the old slow down-speed up cycle in an
unsatisfactory way.

I took a look at it and found the control module had two set screws; one
that adjusted sensitivity and one for gain. These determined how
quickly the unit determined it needed to speed up or slow down to
maintain a speed and the other at how quickly it actually did the speed
up or slow down.

After 30 minutes of trial-test cycling in traffic, got it so it behaved
very nicely.

Not sure how modern units are controlled but there's probably AI in it
somewhere!

SMH