The Analog Elevator Brain

I remember watching a video a while back that poked fun at how uncomfortable people were with the idea of a machine having control over their immediate physical surroundings. It was used as a lead-in for the topic of self-driving cars, but before that they brought up some interesting historical analogies.

When elevators first switched from human operators (back then there were actual people hired to operate elevators) to automatic user-operation, a lot of folks didn’t like the fact that there wasn’t a person there controlling the movement anymore. Elevators were a new and scary technology with lots of potential risks, and even if automated control was verifiably safer, people really wanted other people to control those risks.

So, elevator engineers added some choice features to make people feel safer while riding (while not actually making them any safer): big, red emergency “stop” buttons, an in-elevator telephone, and even speakers offering soothing, pre-recorded human voice lines—“Hello. Which floor would you like to go to?”

Comparing this initial scare—which, of course, now feels almost silly—to the reservations that some have for self driving cars today is questionable (for one, the number of dimensions of free movement of a car vs. an elevator—imagine a self-driving airplane!), but it inspired this thought: Isn’t it weird that the technology required to generate and harness enough energy to move a giant, heavy metal container (and people inside) against Earth’s gravity came about before the technology required to figure out where it should go when it’s doing its job?

I think most people would say the former sounds more impressive, at least when they first hear it. But on second inspection, you would probably realize that a basic mechanics operation—regardless of how much energy it might need—will be, at the very least, figured out with much less mental effort than something complicated like machine logic.

And as it turns out, even an apparently simple operation like sending an elevator to the right floor based on the combination of requests and buttons pressed is pretty difficult to do automatically. Industrial Era powered elevators* were brought into mass use in the early 19th century, but completely automated ones weren’t available until almost a century after (it took a few more decades for people to widely accept them).

The first totally automatic elevators implemented something called relay logic, which was basically a predecessor of the transistor-based logic we use today for computing. These circuits did all the work a standard human operator would’ve done before they came along—detecting which floor the elevator was on, sending it to the correct floor based on its requests, positioning the elevator level with each floor, and opening and closing the doors when it arrived.

But of course, before we got the awesome technology of automatic elevators, humanity had to wait until all the necessary advancements required to make good circuits were made, right? Maybe. I would say that a sufficiently advanced/well-designed analog system could match many of the things a digital system might do (after all, analog computers—limited by the noise of a continuous process rather than discrete truncation—have been around for a while and have certainly proven their usefulness). At the very least, this definitely has the potential to be extended to an elevator “brain” (hence our title).

So here’s the challenge: Using only pre- or early Industrial Era technology, design a working analog elevator brain that can perform or outperform all the relevant tasks that a modern elevator control system does.

I admit solving the challenge is limited to a few people with very specific domain expertise. This is just a thought experiment.

If you recall that original thought (the weirdness of elevators being developed long before their control systems), you might realize that this challenge sets out to prove its premise: that automatic elevator control systems could’ve been developed earlier, without the need for any circuitry. After all, the energy required to perform these logic operations will probably be orders of magnitude less than the amount required to move the elevator itself—we only need to have a sufficiently advanced system.

You may have also realized that it totally makes sense that elevator control systems would be developed after the invention of a powered elevator, since there’s no need to control something that doesn’t exist yet—but to that I present two counterpoints:

First, a particularly forward-looking human could have come up with the design well before if it were possible, perhaps for another technology (remember the energy requirements for each). Second, a century of development is still a long time, and we can always try and prove that this could’ve happened much sooner.

To be clear, using electrical signals for this challenge is fine, but you would not be able to rely on any sort of processing through printed circuits. But before you set out to make your flowchart/schematic/blueprint/engineering draft, here’s a general set of three features I think a design should need for it to be considered fully automatic:

1. It needs a selector (Taken from elevatorpedia. And, before you ask—yes, there’s a wiki dedicated solely to elevators and their design), or some method to accomplish the same task of detecting which floor the elevator is on.
2. It needs to include a mechanism that will somehow stop it level to each floor, open both sets of doors, and release it when it needs to move again.
3. Most importantly, it will need some kind of brain to process this information along with the requests to output the correct floor option (if you could only design one of these features, it should be this one)

—the “correct” floor option can mean a lot of different things. Here are the most common elevator floor-choosing algorithms, but any method should be fine as long as it makes sense:

• First obey all the commands of those inside the elevator, until checking any external requests and then returning to the ground floor (not common in commercial elevators).
• Perform “sweeping” operations, moving up until the highest floor request is met, then turning around and moving downwards until the lowest floor request is met (what you’re probably used to).
• Bonus points for finding an analog implementation of more efficient algorithms.

If you think about it, you’re mostly just designing a basic computer made to do a specific task using really old parts. If that’s difficult, you can assume the computer itself is accounted for and just find a way to use the outputs of a computer to move an elevator and put inputs back in.

So there you have it—all the tools necessary to check if Industrial Era engineers were fools for not having made automatic elevators sooner. Have at it, and tell me how it goes.