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Old cars had fully mechanical steering systems which required a lot of physical effort by the driver to steer. As technology progressed, mechanical systems improved and became easier to use, but, to some extent, they were still "directly" controlled by the user (the steering system is mechanically linked to the user).

Even newer cars have fully electronic controls with controllers and actuators (the steering system is no longer mechanically linked to the user). However, some people claim that this newer technology is slow, citing input lag.


My question: Even if there is input lag today, couldn't electronic controls be significantly* faster than mechanical controls in theory?

After all, the latency in a mechanical system is limited by the speed of sound, whereas in electronic controls, this latency is limited by the speed of light.

*not necessarily perceptibly

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In theory, the fastest way to transmit the signal is the fastest. In practice, that isn't always electrical.

One key requirement for electronic controls is that they need to encode the state of the control, send it out, process it, send out the resulting output, and then actuate the hardware. These steps are not instantaneous. In fact, they can be slow enough to matter.

This is similar to a known issue with live audio. There's a lot of desire to use digital communications within a venue to transmit sound. Instead of needing gigantic snakes you can get away with Ethernet cables. It sounds great. However, there's a catch. Each processing step chews up about a millisecond (mostly due to the need to marshal data on the wires). Once you get to a handful of milliseconds of delay, you actually start to get nasty interference issues which can prevent performers from singing properly! If the data was transmitted continuously, there would be no problem, but with virtually all digital buses, there's a need to pack the data up into packets to be more efficient.

That being said, the real issues are input latencies and haptic feedback. The computer can now brake far faster than you can. However, it's easy to find the electric systems to feel "sluggish" because they often don't provide the haptic feedback we're used to. A skilled driver can feel the condition of the road in how the road vibration is transmitted through the steering wheel. Take that away, and they only get the sluggish feedback of the car actually visibly turning. This can make the car feel slower to respond, even if the car is actually faster in respose!

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  • $\begingroup$ Did you intend the first sentence to be a tautology? If so, I don't understand what message you are intending to convey. $\endgroup$ May 7 '17 at 18:48
  • $\begingroup$ @sammy gerbil, The first part is a tautology, yes. The issues that make electrical communications not always the fastest are practical issues with show where the limits of the theory lie. $\endgroup$
    – Cort Ammon
    May 7 '17 at 19:51

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