Originally published at: Nissan demonstrates its new stop-and-start control with a countertop ramen-delivery vehicle | Boing Boing
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Incoming lawsuit from Nissin Foods for trademark confusion in 3…2…
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this is called “active damped harmonic motion” and the first time I saw the technique was for a motion control systems used in silicon manufacturing. it’s pretty incredible that they think they can make it work in a car with people.
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This is, in fact, pretty cool. Show us the delta-v and delta-a curves as compared to a regular car!!
Also: I wonder if it would work as well with curved bowls.
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Now I’m hungry for ramen. Thanks.
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me too. Why can’t I get decent ramen around here?
I would love to hear a BoingBoing commenter who knows a little bit about PID Curves tell us how what is going on here is different. I did enough tinkering with multirotors a few years ago to learn about how PID calculus is embedded in EVERYTHING, from cargo-ship autopilot to home thermostats to car cruise control.
Is what’s going on here a refinement of that? Is it something else altogether?
UPDATE: @mikest 's phrase “Active Damped Harmonic Motion” led to this article, which I’ll now go squint at for a long time. Thank you!
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I’m not sure I really understand the point of this?
Cars are not autonomous and I don’t notice any uncomfortable feelings when stopping.
If this can make my vehicle stop quicker, sure bring it on - but not at the expense of having expensive dampeners and controls. I’d rather not spend a small fortune to replace struts. I run EBC yellows because I care about stopping, not how smooth and nice it is. But then again, I drive a manual so I’m way way in the minority.
It’s probably a nice technology to have on hand though. I could see it in large applications, like a bus.
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I don’t want a Nissan. I want a little ramen delivery system for my kitchen.
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Your internal organs, body fluids, and soft tissue slosh forward until they impact the inner shell of your body (or whatever you want to call it).
I call it my clever disguise.
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I was waiting for them to suddenly toss another bowl of ramen in front of it to make it stop short. It didn’t seem like a fast way to stop in this marketing clip.
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Amen! Or at least a sushi boat restaurant that deploys little cars like this. I’ve seen a few model railroad sushi delivery systems so this can’t be far behind. I look forward to the fender benders.
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Or, just mount this on any transport device of your choice:
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German trains (ICE), at least the newer ones, have had this for years. You don’t notice them pulling up or stopping, except for the motion through the windows.
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A lot of things seem like they have PID control in them, but in most cases what you’re seeing is actually just hysteresis control. To take the thermostat example, the furnace comes on at X-2 degrees, but shuts off at X+4 degrees (for set temperature X). That’s a hysteresis of 6 degrees. This simple technique avoids hunting, chasing, and thrashing in systems with noisy data and a lot of interia. Another example is altitude control in airplanes. The first lesson they teach pilots is “don’t chase the altimeter” for this reason. The plane takes longer than you think to change altitude, and the altimeter itself is a noisy, slow instrument that takes time to reflect where you are.
Without a hysteresis, your furnace would click on at X-0.5 degrees, run for 1 minute until it hit X degrees, then shut off. However air currents in the room would shift the temperature around a little and suddenly the area around the thermostat would be X-0.5 again the furnace would click on again instantly. Even worse, the thermostat might be slow to detect the change due to air currents, and the furnace might shoot us up to X+2 and then the A/C would kick on to frantically try and get back down to X. It would then overshoot again and the heat comes on again at X-1.The whole system would be constantly thrashing itself, chasing X in a very inefficient way.
PID control is one level above this, but is only used when hysteresis isn’t enough (such as in multi-rotors). The advantage of PID is that it can react extremely quickly and copes well with imperfect data without doing too much hunting. What it’s really doing is pushing the hunting down to a smaller domain. In the thrashing furnace example, instead of hunting to hold ±2 degrees, it will hunt to hold 0.1 degrees. For systems that can react quickly, like the RPM of a small brushless motor, this is ideal. You get a stable result with minimal perceptible hunting. The downside PID control is that while it compensates for slow noisy inputs (eg altimeters) it requires a lot of CPU and fast-reacting positive-feedback outputs (or precise inputs for slow, noisy outputs). Great for BLDC motors, not so great for many other things (eg. ICE drones use different control systems for this reason). Mostly though it just isn’t necessary in most applications where a hysteresis is sufficient (and can be implemented with no CPU at all- old furnaces do it with a bimetallic strip holding a mercury switch. Reliable, no power required, and maintenance free for 100 years).
What Nissan is doing is PID control with better software, basically. If you know the exact physical properties of inertia in the thing (in this case a bowl of liquid) and have good accelerometers, you can PID your way to optimal deceleration while minimizing forces on that substance (ie. humans). ABS brakes are actually doing the same thing in a very primitive way. By maintaining wheel roll and not allowing them to lock up, you keep deceleration at maximum in a controlled way (if a wheel locks, it goes into static friction and deceleration decreases). The real benefit of ABS is really that you maintain steering control in a panic stop (most people don’t know this though and don’t try to steer around the object like they should) so it’s not a great analogy.
The catch with this is that it requires precise output control, like the BLDC motors again. So it isn’t going to work in non-perfect road conditions and probably works best with electric cars that can achieve very consistent braking control through regeneration. This is why high end trains do it, as observed above- regenerative braking and consistent predictable traction conditions exist. But this Nissan system isn’t going to work on black ice or while hydroplaning, for example.
I dunno if that answered your question. Process and motion control is not my field of expertise, but I’ve done some adjacent things like inverse kinematics and know enough to be dangerous and/or sound smart on the internet.
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!!! This makes SO MUCH SENSE. Especially how PID is appropriate for situations where the, uh… :waves hands: small stair-steps that a calculus-based approach gives are useful. As opposed to a situation where either the inputs or outputs are so big that really squinching the math down would be a waste of time, so good old addition and subtraction are where it’s at.
Your point about a bimetallic strip holding a mercury switch is REALLY well-taken; especially the part about how it’s maintenance-free for 100 years. Of course, now I’m wondering if the fact that the bimetallic strip is a coil means that the physics of an expanding and contracting coil actually embed some kind of deep geometric magic, and that the behavior of a bimetallic coil as it expands and contracts is actually extremely sophisticated… but all I’m doing is conjecture here!
I feel like modern elevators have opinions about how to slow down and speed up in a briefer, yet smoother way that seems similar to what Nissan is talking about here. Like, at the new Comcast Technology Center in Philadelphia, the elevators are stuffed with electronics and opinions. One of their swanky features is that they go from zero to “extremely fast” in a rapid, but smooth way that Douglas Adams would have described as “smug.” And they slow down the same way. Those have got to be big, precise, brushless motors(?) and a fairly well-understood domain (a box of people).
Anyhow, THANK YOU for your response. BoingBoing has the world’s best comment section.
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No magic, it’s just that the effect is small so you need a long strip to get enough motion to tilt the mercury enough. Coiling it lets it fit in the little box on the wall and also ensures you get a tilting action on the mercury switch.
Honestly, the primary feature of modern fast elevators is that they accelerate at all. Older elevators are literally a cable on a drum with a motor that turns on and off. Below a certain top speed, you don’t need to accelerate and decelerate. Think about you garage door opener, for example. It doesn’t have an intentional acceleration or deceleration curve. It just goes. However if your elevator is fast, you need to have an electronic controller to accelerate and decelerate at both ends so that you don’t terrorize the contents-I-mean-passengers and also because it’s easier on the equipment. No fancy PID or anything needed though, just a motor controller with an accel/decel curve in it. Most things in the modern world are simpler than most people think they are, in my humble experience. However they are definitely smug.
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This is a good description of the problem, but I would hazard to say that it’s less about the PID controller and more about what the PID controller is solving for and what it’s using for feedback.
In a system like this I’m imagining that the controller has some sense as to what the passengers in the seats are doing. The controller is probably then solving for a braking curve that minimizes deceleration in the passenger while also minimizing stopping distance.
A good human driver does this naturally. They will feather their braking to the point just before feeling themselves break away from the back seat. If they break too hard and release too hard and the passenger lurches, it’s uncomfortable and anxiety producing.
(Edit: @VeronicaConnor goes over this in more detail above.)
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