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.
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.
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.
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.
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.
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