5 ms·

It's really smart though: Why spend a lot of energy moving the wheel up and down, when you can just control the damper and rely the spring to store energy.

deleted 1y ago
[deleted]
thrill 1y ago
Precision, repeatability, responsiveness.
yesco 1y ago
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.
- neom 1y ago
  88ft not 88 miles. I don't understand your 120hz camera line, I also have a degree in imaging tech and that part I do not understand, would you be so kind as to expand upon it??
  - yesco 1y ago
    Wew I'm getting a lot of pedantic replies here. Yeah I got the units wrong there my bad, you get the point I was making though right? In regards to the 120hz camera line, I would be happy to expand on that for you. To be clear, I'm specifically talking about how when you try to increase sampling rate by interlacing multiple concurrent digital sensors you need to deal with the following potential problems (this is a property of all digital sensors): - Real time synchronization between concurrent sensors requires additional processing time to ensure proper ordering. The samples need to be processed together in small batches. This adds latency and the more things you are trying to synchronize the more latency is introduced. - Inter-sensor calibration to account for variations between individual sensors can be used to reduce the latency introduced by synchronization but lacking this, you are bottlenecked by the slowest sensor. There are a lot of different ways to handle this though so I'm speaking very generally. - Broadly speaking most signals need to go through some kind of filter to remove noise, most digital filters have a certain amount of algorithmic latency built-in that is physically unavoidable. When you are interlacing multiple different sensors, you are getting more noise, so the likelihood of a filter being required starts to increase. I want to stress here that these are not impossible challenges. In fact they are largely solved problems. But they are not universally solved in the same way, you need to balance between precision manufacturing, signal quality and signal latency. In practice most people are not prioritizing latency, so a 120hz camera might be optimizing for video recordings and not live processing scenerios. So long as you know what you are looking for you can avoid this when choosing which camera to use. Computers can be fast, but fast can mean different things when dealing with real-time situations in high speeds. Bottlenecks need to be considered from all levels. The clock speed of the computers CPU often gives product managers weird ideas about what is possible. This was the main point I was trying to make here.
    - 1y ago
invalidator 1y ago
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.
- appreciatorBus 1y ago
  This is my biggest fear of technologies like these. The whole point of a speed bump, for example, is to ensure that behaviour that puts others at risk will, at the very least make the driver uncomfortable. If we then deploy technologies that make speed bumps “disappear” from the perspective of vehicle occupants, it’s going to enable people to comfortably drive a lot more aggressively at the expense the people on the other side of the windshield. Conversely, if we were to deploy technologies like speed governors, then we could do away with the speed bumps and the need for fancy suspension.
  - linsomniac 1y ago
    >technologies that make speed bumps “disappear” My 2004 Land Cruiser has such technology. It's called "being a Land Cruiser". As a sports car fan, I'm quite familiar with how hard it is to make speed bumps that work for every vehicle. You're not wrong, but also it's a pretty crude technology, speed bumps.
  - mindslight 1y ago
    The problem with speed bumps is that the level of annoyance is drastically higher for the already-slow prudent driver in a reasonable vehicle, compared to the lackadaisical latently-fast driver in an oversized monster SUV. So most of the intended targets get punished with "wow that was bouncy lol!" while the collateral damage gets comically slow crawling and/or frame damage. Speed bumps also draw the attention of drivers towards focusing on the obstacle, and away from staying alert for pedestrians. I just had an experience with a parking lot (at a place generally full of kids), that had added a horrible speed bump at the entrance and then removed it a few months later. As far as I know there was no problem with people speeding in the lot, it was likely just some busybody trying to make things "better". Thankfully someone more in charge saw the light of reason.

deleted 1y ago

[deleted]

thrill 1y ago

Precision, repeatability, responsiveness.

yesco 1y ago

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.

neom 1y ago
88ft not 88 miles. I don't understand your 120hz camera line, I also have a degree in imaging tech and that part I do not understand, would you be so kind as to expand upon it??
- yesco 1y ago
  Wew I'm getting a lot of pedantic replies here. Yeah I got the units wrong there my bad, you get the point I was making though right? In regards to the 120hz camera line, I would be happy to expand on that for you. To be clear, I'm specifically talking about how when you try to increase sampling rate by interlacing multiple concurrent digital sensors you need to deal with the following potential problems (this is a property of all digital sensors): - Real time synchronization between concurrent sensors requires additional processing time to ensure proper ordering. The samples need to be processed together in small batches. This adds latency and the more things you are trying to synchronize the more latency is introduced. - Inter-sensor calibration to account for variations between individual sensors can be used to reduce the latency introduced by synchronization but lacking this, you are bottlenecked by the slowest sensor. There are a lot of different ways to handle this though so I'm speaking very generally. - Broadly speaking most signals need to go through some kind of filter to remove noise, most digital filters have a certain amount of algorithmic latency built-in that is physically unavoidable. When you are interlacing multiple different sensors, you are getting more noise, so the likelihood of a filter being required starts to increase. I want to stress here that these are not impossible challenges. In fact they are largely solved problems. But they are not universally solved in the same way, you need to balance between precision manufacturing, signal quality and signal latency. In practice most people are not prioritizing latency, so a 120hz camera might be optimizing for video recordings and not live processing scenerios. So long as you know what you are looking for you can avoid this when choosing which camera to use. Computers can be fast, but fast can mean different things when dealing with real-time situations in high speeds. Bottlenecks need to be considered from all levels. The clock speed of the computers CPU often gives product managers weird ideas about what is possible. This was the main point I was trying to make here.
  - 1y ago

invalidator 1y ago

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.

appreciatorBus 1y ago
This is my biggest fear of technologies like these. The whole point of a speed bump, for example, is to ensure that behaviour that puts others at risk will, at the very least make the driver uncomfortable. If we then deploy technologies that make speed bumps “disappear” from the perspective of vehicle occupants, it’s going to enable people to comfortably drive a lot more aggressively at the expense the people on the other side of the windshield. Conversely, if we were to deploy technologies like speed governors, then we could do away with the speed bumps and the need for fancy suspension.
- linsomniac 1y ago
  >technologies that make speed bumps “disappear” My 2004 Land Cruiser has such technology. It's called "being a Land Cruiser". As a sports car fan, I'm quite familiar with how hard it is to make speed bumps that work for every vehicle. You're not wrong, but also it's a pretty crude technology, speed bumps.
- mindslight 1y ago
  The problem with speed bumps is that the level of annoyance is drastically higher for the already-slow prudent driver in a reasonable vehicle, compared to the lackadaisical latently-fast driver in an oversized monster SUV. So most of the intended targets get punished with "wow that was bouncy lol!" while the collateral damage gets comically slow crawling and/or frame damage. Speed bumps also draw the attention of drivers towards focusing on the obstacle, and away from staying alert for pedestrians. I just had an experience with a parking lot (at a place generally full of kids), that had added a horrible speed bump at the entrance and then removed it a few months later. As far as I know there was no problem with people speeding in the lot, it was likely just some busybody trying to make things "better". Thankfully someone more in charge saw the light of reason.