I don't think it was mentioned, but the algorithm would be different based on the behavior of the majority. In some buildings most traffic is either up from lobby or down to lobby, e.g. it's very rare for people to go from floor 5 to floor 6. In some it's the other way around, where majority of moves don't involve lobby.
Show HN: Elevators
111–120 of 426 posts
Re: Show HN: Elevators
#112In 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…
Not to mention maintenance means taking an elevator out of service, meaning average wait times go up during that period.
Someone needs to design an elevator that only breaks down between midnight and 5am. Maybe a different model to accommodate late night crowds returning to large residential buildings.
Re: Show HN: Elevators
#113I was on a Royal Caribbean ship a couple weeks ago (Utopia, 18 decks, 5,668 passengers). It has 24 main elevators split between front and back, left and right. So a bank of 6 in front of you each time you needed a lift. You press your floor on a touchpad and it assigns you an elevator A through F. I swear no matter if it was busy or not, it seemed like everyone was assigned to the same one or two elevators. The wait…
This type of system is mentioned in the article under the "Destination Dispatch" section.
Re: Show HN: Elevators
#114I was on a Royal Caribbean ship a couple weeks ago (Utopia, 18 decks, 5,668 passengers). It has 24 main elevators split between front and back, left and right. So a bank of 6 in front of you each time you needed a lift. You press your floor on a touchpad and it assigns you an elevator A through F. I swear no matter if it was busy or not, it seemed like everyone was assigned to the same one or two elevators. The wait…
Possibly to balance the hours on elevator banks. Common in buildings to leave some out of the cycle, since elevator maintenance can be a year out to schedule. Probably much worse out at sea
Re: Show HN: Elevators
#115[flagged]
Re: Show HN: Elevators
#116Oh my god, every time I'm waiting for the elevator, I think of how annoying it must be to be someone who's building the algorithm to make sure that you minimize the amount of wait times between picking up people and taking them to their destination. Then I also wonder if the people who apply the logic and program the logic into the elevators are actually evil sadists that are doing it on purpose to make us wait longe…
They might have other objective functions like wear-and-tear on the elevators, total energy usage, or something
Modern elevators have regen braking, so they can recover most of the energy spent on going down. Older elevators used braking resistors for that.
(BTW, going _down_ while empty is typically more energy-consuming for the elevators because they are counterweighted)
Edit: that's also why you shouldn't use elevators in a fire. If the brakes in the elevator machine room fail, the cab won't crash down. It will go _up_, possibly dragging you into the fire. Many firefighters died because of that.
Re: Show HN: Elevators
#117> Destination Dispatch [...] are in general worse I wonder if this is an artifact of how the author used random destinations. I worked in a building that used Destination Dispatch, and the common travel pattern seemed to be: - Everyone who is not on the ground floor generally want to go to the ground floor. - People who are on the ground floor generally travel in large groups to the same destination. This happens bec…
Is it because the criteria is wait time not travel time? Destination dispatch would avoid some extra stops on the trip.
I just visited a new building with destination dispatch, so it seems to be still around.
My EE roommate in college had to build an elevator circuit as a final problem. It was on a bread board and had a bunch of call buttons and had a motor and a clear disk with black squares so it could figure out where it was…. I think it was the simple algorithm…
Re: Show HN: Elevators
#118Earlier quoted context omitted.
What makes me more peeved about destination dispatch elevators are people who aren't used to them, and all pile into an elevator without hitting a floor, thinking one input is enough for everyone. Then, a totally full elevator stops at intermediate floors to pick up callers, but there's no room to get in. If everyone put the floor in as they arrive to the elevator lobby, then the elevator would know how many people a…
The elevators I've seen have a "group call" feature slightly hidden in the menu.
That’s awesome! I haven’t really played with them, only silently seethed when the elevator is crowded.
Re: Show HN: Elevators
#119We used to do this as an interview question at my current job. We didn't expect people to solve it necessarily, and we just specified to solve for a single elevator car. We just wanted to see how people would break down the problem.
Even at that relatively reduced level of complexity, it's quite tricky to figure out how to prioritize who gets served when.
Re: Show HN: Elevators
#120Over the years, I've witnessed numerous instances of poor elevator behavior:
- Two elevators ascending and descending in near lock step, in a two-elevator building, effectively reduced to one elevator.
- When going in a different direction from the requested one (e.g. called elevator to go up, but actually going down), the doors wastefully close, open and close again. Seen this in many elevators.
- At 3 a.m. you take the elevator to a parkade, like to get something from a car. When you return to the elevator a minute later, it is gone; it spontaneously moved away even though nobody is using it but you.