Yes correct, we use electric motors to directly control an efficient compact pump to bidirectionally pump fluid, or use back electromotive force to dampen motion (and capture energy while doing so). This eliminates the need for controlled valves, but requires advanced controls to mitigate system dynamics (hydraulic losses, etc).

For ride control, machine vision helps a bit, but it’s limited due to the need to determine high fidelity road z-measurements which requires very high resolution and clarity at speed, and no visual occlusion. It helps with simple problems like bump vs hill (which is not trivial to predict just with accelerometers), but we’ve figured out how to get most of the benefit of machine vision with just accelerometers and fast actuators. GM was able to use vision to improve pothole performance, but it’s still a semi-active system that only provides fast adjustable stiffness (damping).

For pre-crash, the system uses cameras to detect a collision-path vehicle and determine an optimized impact zone for that vehicle. For example, the frame or bumper has more structural rigidity which may be desirable in certain crash scenarios.

What a waste of people's health and workforce. Do they not have pneumatically sprung seats, at least, if the vehicle has no suspension? These have been available for a long time - my dad was a farmer and had one on his mid 80s Fendt tractor.

That was certainly how the original tech demo worked.

To create enough force to lift the car using linear motors requires massive copper coils and rare earth magnets, which is heavy and expensive. It’s also wasteful, because in real world drive cycles peak force is only needed for short periods of time and at relatively low linear velocities. Further, linear motors require significant packaging space which requires the chassis be designed around it. Instead, we use a much smaller motor and a high “gear ratio” using hydraulics to achieve high forces via mechanical gain. This reduces raw material cost by a factor of >10x while achieving similar performance.

If I recall it was heavy. I think speculation had it adding over 20% to the weight of the Lexus.

And those electric motors and control hardware would not have been cheap. But nobody knows how to estimate it - just that it would be prohibitively expensive.

> This video contains content from NBC Universal, who has blocked it in your country on copyright grounds

Why would you drive any vehicle on a road like that at 50mph? At some point a neglected road isn’t a road anymore and shouldn’t be considered as such.

That's going to destroy your tires regardless. The suspension isn't going to save your tires if you deliberately abuse them.

Citroën pulled out of the North American market in the 1970s, due to US regulations that required headlights maintained a consistent height. Since their suspensions allowed them to raise and lower their height, there was no way they could be compliant without massive changes to their system. Besides, the Citroën network was not big in the US anyway, and since the DS had few facelifts in its 20 years in production, it was falling out of favour with US consumers who didn't want to be seen driving yesteryear's car.

Their build quality is fine, at least contemporarily to the rest of the market; of course today, we would find its steel pitiful. It's not without reason that people who maintain Citroëns of that era tend to replace the panels with fibreglass ones.

Additionally, as Citroën pulled out, the maintenance network in North America began to falter, as the suspension system required significant know-how. There are still a dedicated group of Citroën fans in North America (albeit small), and I met a lot of them when I drove from coast to coast (and back again) back in 2017 in a 1998 Citroën Xantia. A car that may not seem particularly interesting to Europeans (although it was the Activa V6 model), but it was extremely rare in North America.

Just yesterday I was remembering the ride on a Citroen XM in the 90s which has the full blown hydropneumatic suspension (https://en.m.wikipedia.org/wiki/Hydropneumatic_suspension) . Decades later I haven’t been in a car with such a smooth ride

I can confirm. Was driving for a while, impervious to any sign of having a flat tyre before someone on the street signalled me to stop. And that was on a Citroen Saxo, which I don’t think had the suspension of C5 etc. Amazing car, lasted for 15 years with me, with only battery and frankly inconsistent oil changes. The lady who bought it when we immigrated still runs it 15 years later. Build quality is a hit and miss per model I think.

they even had a project for hydraulic-driven wheels - some kind-of water-mill in each wheel, and a huge pump, and that's it :)

p.s. long time ago i bought a 15y old hydraulic Citroen, drove it for 10 years.. the hydraulics was less breaking than the engine :/ . Now i have another (recent) Citroen but that "road-surface-ignorant" feeling of the hydraulics is completely gone.

It's not the same.

For a simple example, let's say you are simply driving in a circle. The car wants to lean toward the outside. The linear motors can provide a countering force, lifting the outside, lowering the inside, so the car stays level. Variable damping can only control the rate that it rolls. It will still roll in sub-second timescales, unless it completely locks down the suspension, which is terrible for both handling and comfort.

For another simple example: going over a speed bump. Linear motors can lift the front wheels over the bump, and then the rear wheels, so the body stays level the whole time. An active damper can go full-soft the moment the wheel hits the bump, but the compressed spring will still start lifting the front of the car. An active damper can do a better job managing the rebound on the far side so it doesn't oscillate, but it can't entirely prevent the bump from pitching the body up and down in the first place.

That's not to say it's worthless. Very fast active dampers can improve both handling and comfort. It's just nowhere near the level which is possible with linear motors.

It's easy to underestimate just how slow digital systems are in many real time scenarios compared to analog systems.

Consider it in the context of camera based self-driving cars, it's tangential to this discussion but it's an easy to visualize metaphor:

- A car traveling 60mph is traveling at 88 feet per second

- Assuming a 60hz camera, there would be a 16.67 ms gap between each frame

- The car is traveling 1.5 feet between each frame interval

- A certain amount of exposure time is necessary for the camera to generate even 1 frame or it will be blurry

- High framerate cameras often work around this by staggering/interlacing multiple sensors, but doing this implicitly increases the latency of each frame

- A 120hz camera might deliver double the frames per second, but each frame could be arriving 4 frames late in exchange

- 4 frames would be imperceptible to humans, it would be 3 feet for the car

- You haven't even processed any of these frames yet.

- Your off the shelf library introduces a random 1 second delay for some reason and costs you 88 miles in processing time

- The car can drive as fast as 120mph

All digital sensors implicitly have a sampling frequency, and the fundamental disconnect is always high sampling frequency =/= low latency. People constantly make this mistake over and over, and by the time you notice you are already too deep into development to make a change.

Decreasing latency is expensive, and requires specialized knowledge. Often you get expert software engineers who end up bottlenecked by the hardware limitations they can't even comprehend or the reverse, hardware guys bottlenecked by the software they can't introspect. The latency is only truly understood when you get to integration testing.

Nearly every step of the way you discover you need specialized hardware, software, operating systems, sensors. Every part of the chain each costing you more latency. It's like it's own ecosystem where almost everyone writes everything from scratch and doesn't share anything. It's gotten better in recent years though.

Full disclosure: I work in medtech and don't actually deal with cars, but it's a very similar problem space. We often use the same hardware/software cars use for this reason.

Precision, repeatability, responsiveness.

RAS syndrome is not actually a problem, it's never actually misunderstood, in fact it usually adds clarity as redundancy in language usually does.

>You did a finite element analysis analysis?

That'd what it's called when you put the FEA in the circular file because the part is an inconsequential revision of something that's been in production forever and works fine.

I knew someone was going to be pedantic when I wrote that.

I would guess this feels quite a bit different, the clearmotion tech puts electrohydraulic actuators in every corner of the vehicle and is proactively pushing and pulling wheels. MagneRide isn't even active (maybe semi-active, not sure) - never mind predictive and proactive.

Adjusting damping rates is very different from proactively lifting a wheel just as it reaches a bump.

I got a tour of Prof. Bose's factory as a student while taking his course on acoustics. Active suspension is basically a speaker voice coil but scaled up and pushing a car wheel instead of a cone. A lot of the physics and perhaps more critically, the manufacturing processes, were shared between speakers and suspension as they implemented it. I actually got to sit in the car as it drove over bumps, it was pretty magical. iirc you could flip a switch and set a suspension profile that made it emulate other cars road feel as well. Years later I built a toy model of it using an actual speaker to make a pushbutton switch that could emulate the feel of a broad range of other switches.

At one point, Bose was a few scientists who happened to have a consumer tech company.

that was the joke

Which is exactly why you want that suspension.

Both this and the Bose linear actuator one lift just the wheel that needs lifting, just enough to clear the obstacle, keeping everything perfectly steady, it's incredible.

The fact that it can also do silly jumps for marketing reasons is a different topic.

Even though they're the cream of the crop of a country of over a billion people, those silly engineers at BYD don't know what they're doing. We'd all be better off if they took tips about this problem they've spent years developing from random guy on the internet.

> While cool as a shower thought, in reality, having a 1200HP car jump and go airborne while you're swerving to avoid a pothole is just about the last thing you want it to be doing.

Surely the system takes cornering into account. Having a suspension that can use predictive motions to compensate for a pothole would ideally produce better handling by minimizing the disruption of a pothole imparting a massive disturbance to the vehicle.

If you're swerving in that car and clip any portion of that pothole, you're almost certainly going to lose control anyway. And if you've swerved around the pothole successfully, there's nothing for the suspension to have to jump. ;-)

> The Bose Magic Carpet was the original version of all of these powered suspension cars 20 years ago.

No, the Citroen Activa active suspension was in production from 1996.

Yes, this seems significantly more about the IP than a technology breakthrough…more TikTok than 60 Minutes.

I'm in the same boat regarding sound deadening, so when I was in the market for a car this was my #1 priority. But outside of the luxury segment, they do not even talk about sound deadening or noise isolation. This idea simply does not exist. It was very disappointing because this is a fairly low tech, inexpensive feature that could easily find its way to mainstream cars. Sure it adds some extra weight, but the improvement in riding comfort easily outweighs the fuel consumption. It's like flying with noise cancellation headphones. You don't know what you're missing unless you try it once, and then you can never go back.

I'm sure it does, but this just made me realize something.

I drive a Smart Fortwo, which goes in the opposite direction - there's not much suspension to speak of, and the short wheelbase means you rock around a lot more on uneven street surfaces, so you're very much connected to the outside world. One of the things I've noticed when switching back and forth between that and a normal sedan is that, if I'm not consciously thinking about it, I'll drive slightly more aggressively in the sedan than in the Smart. And I think it's precisely because of that difference in connection with the outside world.

The same happened when I rented a pickup truck a while back to move some furniture; I don't remember the model, but I think it was a fairly recent/common one. It was very clear that movements that would have felt pretty aggressive to me if I were walking or biking around felt less so from the driver's seat. And I bet the same is true of these luxury cars.

This is of particular interest to me because my day-to-day method of getting around is not driving but rather walking and biking, and it's worrying to me if drivers are subconsciously acting more aggressively just because they feel more disconnected from the world around them.

Rolls Royce made the Ghost so quiet testers called it nauseating. They had to remove some sound dampening to make it more comfortable.

Which is pretty neat considering it has a 6.7 liter bi-turbo under the hood.

The ABC system does more than the earlier hydropneumatic systems of Citroen etc. Those earlier systems have a slow response that can compensate for things like ride height, not to actually move the struts up and down rapidly like the ABC system.

For example see the "rodeo test" where the car moves each corner up and down to test the system. ABC involves active feedback control of the body and rapidly adjusts force/displacement of individual struts, just like what the Bose system does with electric actuators.

https://youtu.be/391IPl3LJOs

They just tried something like this in some city in Minnesota (I think) and had to revert after a month from the public outcry.

> so you can hit them at significant speed and not damage anything.

That’s the point. They’re not supposed to damage the car. They’re supposed to be a little uncomfortable if you’re going too fast.

It’s more reminder than a physical stopper.

> In fact the faster you hit them or the more load you're carrying the better the suspension handles it because you open up the high speed compression valves.

This is a case of knowing just enough about a topic to be dangerous.

Entering the higher shaft velocity part of the damper curve doesn’t mean the suspension is handling it “better”. The high speed behavior of the valving simply means the damping forces aren’t increasing linearly with shaft velocity. They trade extra travel for reduced peak forces.

Make no mistake, though. The faster you go, the higher the forces. The high speed valving (if the OEM dampers are even digressive) isn’t changing that.

If the speed bump is tall enough and the bump stops get completely compressed you could bottom out the damper, which is not good for it.

> I'll often hit them at 30mph+ with no issue.

Just because nothing immediately breaks doesn’t mean you’re reducing the life of the OEM dampers. Repeated high speed impacts and will shorten the life. Getting the wheels bumped up into the range where you’re compressed bump stops transfers a lot of energy into the bushings and other components.

> Rolling over them at a slower speed where your shocks stay uncompressed forces your whole car to go up and then down again, instead of absorbing the energy in the shocks.

That’s the ideal way to do it. This is better than the sudden sharp impact of high speed crossing. You’re not doing your car any favors by driving quickly over speed bumps. Fortunately for you, OEM replacement dampers aren’t too expensive but replacing prematurely worn bushings is kind of a pain.

Properly built speed bumps are most comfortable to traverse at posted speed, but are very well felt when you're speeding. In my experience they build them well in Northern Europe, less so in Eastern.

>I've never understood speed bumps as a concept. Almost every car has at least 4in of travel, so you can hit them at significant speed and not damage anything.

They only work because the average consumer doesn't know this.

If it's the posted speed that's exactly how the bumps are designed. You aren't supposed to brake.

Speed bumps are much rougher in my idiot monster truck than they are on my Mercedes station wagon, idiot monster truck spring rates and damping are engineered to tow heavy loads/carry heavy payloads so especially when unloaded speed bumps are quite jarring compared to a passenger car.