I've always wondered about elevator algorithms. This is awesome.
Show HN: Elevators
71–80 of 426 posts
Re: Show HN: Elevators
#72Anybody knows what algorithm HITACHI is using on their elevators? Their elevators feels most “responsive” in high rises.
Re: Show HN: Elevators
#73Destination dispatch should be no worse than standard up/down buttons, right (at least in theory)? It provides additional information about the destination, but it should be possible for that information to be interpreted as if it were just an up/down button press, so RSR could still be used. I have a feeling a better algorithm could in fact make destination dispatch slightly better than RSR... or am I missing someth…
As the article says, the problem with destination dispatch is that it 'locks in' an elevator. The passenger gets told at call time what elevator to go to, and it can't change that mid flight. RSR has the advantage that the passenger has no idea which elevator will come, and so RSR can change the elevator they will get in real-time as conditions change. This was an insight I had not considered before reading the artic…
I think the problem with simulations like this is that it doesn't include the chaos of innatentive humans.
Forcing functions that dump people into well defined funnels can have such a high net positive effect it more than makes up for theoretical losses.
It's like narrow, hard road bike tires losing performance because of deflection from rough road surfaces and how long it took designers to factor that in to real bikes.
Re: Show HN: Elevators
#74In these various elevator algorithms, it's not commonly discussed the overall wear and tear on the elevator. More movements would typically translate to faster repair times. Hydraulic fluids needing to be replaced, parts breaking, etc.
Efficient elevator algorithms will often suggest moving an elevator into a preempted positioning strategy, based on time of day or peer elevator positions. The scheduler might move an elevator up to offset one coming down, for example. The demand-signal algorithms at least minimize movement in this way.
I think minimizing maintenance at the cost of increasing wait times is probably an important balance to get right. No doubt, the cost owners for maintenance are not going to perceive the wait time of passengers to be as important.
Re: Show HN: Elevators
#75My friend lives in a building with one of those super old elevators with the manual double doors and no queuing. It's the sort of elevator that someone probably got paid to operate once upon a time.
Using such a primitive elevator gave me a newfound appreciation for the complexity of modern designs. The queueing algorithms are subtle but clever, and the difference in efficiency is instantly obvious once you've dealt with the alternative.
Re: Show HN: Elevators
#76My biggest pet peeve is elevator banks where they don’t make some number of idle elevators automatically come back to the lobby. Half your traffic is over there! Everyone coming in has to wait an extra minute or two because all your elevators were chilling on the 35th floor and above.
My apartment building is replacing the elevators, and someone on staff revealed that the first renovated elevator is intended to pick up only from the lobby (i.e. if you summon an elevator from the 10th floor, one of the others will come). This has caused some grumbling or calling it an "express elevator". In an apartment it really is mostly trips to many floors from the lobby. The only time this maybe would be incon…
You should observe if it is the same elevator all the time and the building people just don’t understand it. Our building elevators (bank of 2) always seems to try to keep one in the lobby. About 75% of the time you get an elevator right away when you call it from the lobby. But it definitely isn’t the same elevator! Allocating an exclusive single elevator to that function would seem to be strictly worse from many angles. Like if you modeled having an algorithm like “elevator 2 only services calls from the lobby” you’d find it would be very inefficient and not every effective. But I can see having one in the bank always returning to lobby right away making sense.
My guess is whoever hinted at that didn’t fully understand what they were taking about.
Re: Show HN: Elevators
#77No mention of an algorithm/sensor for checking capacity of the car. It's a pain when your elevator car shows, it's full, and your request is canceled, meaning you have to press again. Better if the car was full and just moved on. I can see how that could be challenging when people get off on intermediate floors, making a full car available again, changing status. And, if 3 people are waiting and there is room for 1,…
Load penalty is part of the Otis RSR algorithm, it's in the article.
Re: Show HN: Elevators
#78Back in highschool, simulating different elevator algorithms was one of the projects I implemented during my CS class. It wasn't for the class — AP CS did not require anything like actual programming — but it was a fun project.
A cool connection is that a spinning-disk hard drive (HDD) is actually kind of like one really long elevator, just wrapped around a spindle instead of perfectly vertical. The SCAN algorithm is actually a disk-scheduling algorithm!
Re: Show HN: Elevators
#79One of the most frustrating assignments[1] (2011) in my computer science education was trying to build a better mousetrap for elevator control. [1]: https://clarkmoody.com/Moody_AgentBasedElevatorControl.pdf
Disk drive read/write algorithms have a lot in common with elevator algorithms. At least they did in the days of physical heads moving across a platter.
Re: Show HN: Elevators
#80Earlier quoted context omitted.
I don't think I've ever seen someone do that
Because most buildings now they just put one button so people stop clicking both
That has not been my experience, and logically it doesn't really make much sense. If you do so, you are making the problem strictly worse.