4 ms·

It is very troubling development when doing something so trivial even requires a computer. That's a matter readily solved by a PID controller made of a few doz

It is very troubling development when doing something so trivial even requires a computer. That's a matter readily solved by a PID controller made of a few dozen 74XXX parts. Possibly made n-times redundant. Even a more fancy LP solver probably wouldn't need a fully fledged computer.

SkyPuncher 5y ago
It's really easy to over react because of the silicone shortage, but in many cars these chips are replacing physically manufactured parts or significantly increasing efficiency in a way that isn't possible with physical based components. Electronic fuel injection is a _great_ example. Much of modern fuel efficiency stems from the fact that an engine can accurately control fuel in the cylinder based on a bunch of factors. Not only does this system require physically fewer materials, it uses less gas (in turn saving production effort).
- baybal2 5y ago
  I think you are misunderstanding me. What I mean under a computer is a Turing complete machine. A circuit just doing some LP solving, or PID is not necessarily a computer.
  - SkyPuncher 5y ago
    By that explanation, I actually 100% confident I'm understanding you correctly. Most of the functionality of these chips can be represented in some form of hardware. However, that hardware is often much more expensive, significantly less flexible, and likely significantly bulkier.
  - rcxdude 5y ago
    Very little applications strictly need a turing complete machine. However microcontrollers are ubiquitous because they are so flexible. One chip does the job of many, and without needing to be specialised, allowing all applications to take advantage of the economies of scale in semiconductor manufacturing. (Also as pointed out here you drastically underestimate the complexity of a modern ECU)
avianlyric 5y ago
There’s nothing trivial about a modern internal combustion engine. The throttle control system is doing quite a bit more work than just opening and closing a physical throttle valve.
dharmab 5y ago
ECUs are simpler to build than the mechanical components they replaced and do things impossible to do mechanically (given the space and weight limits of a car). Jadon Cammisa has a great series on this stuff. Here's just one episode on one topic, drive by wire throttle control: https://youtu.be/gKsCHx5NOMM https://youtu.be/gKsCHx5NOMM
- baybal2 5y ago
  Most drive by wire systems I seen are nothing, but a simplest closed loop PIDs. It's very close to what you are taught in the "How to write a PID controller" class without much extra creativity.
  - dharmab 5y ago
    Have you looked at any vehicle from the past 3-5 years? I own one with drive by wire and you can feel and hear it reacting to variables when you push it to the limits (either in inclement terrain or on a closed course). The linked video has specific video examples from production vehicles as well.
  - kevin_thibedeau 5y ago
    Deciding how much fuel will be injected each cycle is not just a simple PID. The throttle body control may just be a basic servo (although it probably isn't) but the system controlling it is more complicated.
    - baybal2 5y ago
      A separate circuit to map fuel/gas ratio for a given sensor input is also not a rocket science.
- joking 5y ago
  Simpler to build, and even simpler to overbill for them. Is insane to charge over 1000$ for some replacement logic board.
HeyLaughingBoy 5y ago
Let's start by assuming that the engineers are at least basically competent, shall we? I mean, I could implement a PID controller without any 74xxx logic at all: a basic op-amp, a handful of resistors and capacitors and boom I'm done! But there's a reason that engineering doesn't do that these days and it's not that engineers don't know how. My PID control built from an opamp? In 2021 that's almost always a stupid idea. We use computers because doing it digitally has many advantages. We don't use 74xx (or any other logic family) for this because microcontrollers are far more flexible, allow for behavior changes without reworking hardware, allow inventories to scale (the same component can be used in hundreds of products) and more reasons I won't detail. The reality is that in 2021, often the simplest, most robust and cost-effective way to do something trivial is by using a computer to do it.
- baybal2 5y ago
  > The reality is that in 2021, often the simplest, most robust and cost-effective way to do something trivial is by using a computer to do it. Very much not. Complicated MCUs are a very risky single vendor supply, and as we see now, people are now paying for an engineering overkill. 74xxx are available in every shape, and form, from dozens of suppliers.
tziki 5y ago
Ah the classic HN "just use this things I just came up with". https://xkcd.com/793/ https://xkcd.com/793/
- cycomanic 5y ago
  I actually believe programmers/software engineers are the new physicists in this regard.
kortex 5y ago
Ok, lets assume for a moment that throttle can be modelled by a PID plant (it can't) - is the circuit temperature stable? You don't want the characteristics changing as the engine. Now you need a compensator circuit. What about power supply stability and noise? Car power busses are hella noisy, due to alternator and spark coil. Now you need some serious conditioning and filtering. What about knocking? Modern ECUs adjust parameters on knock detection to reduce the damage from pre-ignition. Gotta put in a control system for that. Repeat for manifold air temp, exhaust temp, emissions, rev limiter, etc., and as you mention, make that 3x for redundancy. Now you have hundreds to thousands of components, in a high noise, vibration, and temperature environment, and you have something which is about as efficient as an 80s car. And you can't as easily simulate it cause it's analog. Or just use some digital chips and simulate all the tuning.
KZerda 5y ago
Okay, so you've designed it. Now, make sure it works with the dirty electrical signal of a typical car's power bus. Then make sure it fits in the space requirements of under the car's hood, or in the door, or any of the other tight places that these embedded systems go. Then make sure that it's verified to act over several years of vehicle life. Then, make sure your suppliers will guarantee you that they won't discontinue the part for at least 10-15 years because of legal requirements for spare parts. Just throwing discrete logic at the problem doesn't always help.
deleted 5y ago
[deleted]

SkyPuncher 5y ago

It's really easy to over react because of the silicone shortage, but in many cars these chips are replacing physically manufactured parts or significantly increasing efficiency in a way that isn't possible with physical based components. Electronic fuel injection is a _great_ example. Much of modern fuel efficiency stems from the fact that an engine can accurately control fuel in the cylinder based on a bunch of factors. Not only does this system require physically fewer materials, it uses less gas (in turn saving production effort).

baybal2 5y ago
I think you are misunderstanding me. What I mean under a computer is a Turing complete machine. A circuit just doing some LP solving, or PID is not necessarily a computer.
- SkyPuncher 5y ago
  By that explanation, I actually 100% confident I'm understanding you correctly. Most of the functionality of these chips can be represented in some form of hardware. However, that hardware is often much more expensive, significantly less flexible, and likely significantly bulkier.
- rcxdude 5y ago
  Very little applications strictly need a turing complete machine. However microcontrollers are ubiquitous because they are so flexible. One chip does the job of many, and without needing to be specialised, allowing all applications to take advantage of the economies of scale in semiconductor manufacturing. (Also as pointed out here you drastically underestimate the complexity of a modern ECU)

avianlyric 5y ago

There’s nothing trivial about a modern internal combustion engine. The throttle control system is doing quite a bit more work than just opening and closing a physical throttle valve.

dharmab 5y ago

ECUs are simpler to build than the mechanical components they replaced and do things impossible to do mechanically (given the space and weight limits of a car). Jadon Cammisa has a great series on this stuff. Here's just one episode on one topic, drive by wire throttle control: https://youtu.be/gKsCHx5NOMM https://youtu.be/gKsCHx5NOMM

baybal2 5y ago
Most drive by wire systems I seen are nothing, but a simplest closed loop PIDs. It's very close to what you are taught in the "How to write a PID controller" class without much extra creativity.
- dharmab 5y ago
  Have you looked at any vehicle from the past 3-5 years? I own one with drive by wire and you can feel and hear it reacting to variables when you push it to the limits (either in inclement terrain or on a closed course). The linked video has specific video examples from production vehicles as well.
- kevin_thibedeau 5y ago
  Deciding how much fuel will be injected each cycle is not just a simple PID. The throttle body control may just be a basic servo (although it probably isn't) but the system controlling it is more complicated.
  - baybal2 5y ago
    A separate circuit to map fuel/gas ratio for a given sensor input is also not a rocket science.
joking 5y ago
Simpler to build, and even simpler to overbill for them. Is insane to charge over 1000$ for some replacement logic board.

HeyLaughingBoy 5y ago

Let's start by assuming that the engineers are at least basically competent, shall we? I mean, I could implement a PID controller without any 74xxx logic at all: a basic op-amp, a handful of resistors and capacitors and boom I'm done! But there's a reason that engineering doesn't do that these days and it's not that engineers don't know how. My PID control built from an opamp? In 2021 that's almost always a stupid idea. We use computers because doing it digitally has many advantages. We don't use 74xx (or any other logic family) for this because microcontrollers are far more flexible, allow for behavior changes without reworking hardware, allow inventories to scale (the same component can be used in hundreds of products) and more reasons I won't detail. The reality is that in 2021, often the simplest, most robust and cost-effective way to do something trivial is by using a computer to do it.

baybal2 5y ago
> The reality is that in 2021, often the simplest, most robust and cost-effective way to do something trivial is by using a computer to do it. Very much not. Complicated MCUs are a very risky single vendor supply, and as we see now, people are now paying for an engineering overkill. 74xxx are available in every shape, and form, from dozens of suppliers.

tziki 5y ago

Ah the classic HN "just use this things I just came up with". https://xkcd.com/793/ https://xkcd.com/793/

cycomanic 5y ago
I actually believe programmers/software engineers are the new physicists in this regard.

kortex 5y ago

Ok, lets assume for a moment that throttle can be modelled by a PID plant (it can't) - is the circuit temperature stable? You don't want the characteristics changing as the engine. Now you need a compensator circuit. What about power supply stability and noise? Car power busses are hella noisy, due to alternator and spark coil. Now you need some serious conditioning and filtering. What about knocking? Modern ECUs adjust parameters on knock detection to reduce the damage from pre-ignition. Gotta put in a control system for that. Repeat for manifold air temp, exhaust temp, emissions, rev limiter, etc., and as you mention, make that 3x for redundancy. Now you have hundreds to thousands of components, in a high noise, vibration, and temperature environment, and you have something which is about as efficient as an 80s car. And you can't as easily simulate it cause it's analog. Or just use some digital chips and simulate all the tuning.

KZerda 5y ago

Okay, so you've designed it. Now, make sure it works with the dirty electrical signal of a typical car's power bus. Then make sure it fits in the space requirements of under the car's hood, or in the door, or any of the other tight places that these embedded systems go. Then make sure that it's verified to act over several years of vehicle life. Then, make sure your suppliers will guarantee you that they won't discontinue the part for at least 10-15 years because of legal requirements for spare parts. Just throwing discrete logic at the problem doesn't always help.

deleted 5y ago

[deleted]