Can you or another electrical engineer assuage my discomfort upon reading the above?
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ALL CyberTruck discussion
- Thread starter Fact Checking
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Yeah, it means that if one motor/controller fails the steering will be very difficult when stopped or at low speed, especially with the brakes applied. They said that once moving a reasonable speed one motor provides more than enough force to be able to control the vehicle easily. (i.e. it would be way better than any other current Tesla if the single power assist motor failed in them, where people complain that the steering column feels like it is locked.)
Of course, you would be notified as soon as one failed.
Right. When actually driving, the failure of one motor won’t be a problem, it’ll work fine. It’ll only be a problem when stationary or very low speed. As Mp3Mike points out, it’s a safer system than our current no backup for power steering. I once was driving a van and the power steering went out. OMG, it was all I could do to not to crash into a light post.
One thing that was slightly surprising was how involved the software lead David was in all aspects of the truck.
The other amazing things which others have noted is how much information was freely shared including some of the logic behind the engineering trade-offs.
I imagine that a design team at a competitor would get something out of just watching this video, and that may prevent them going down a few dead-end streets,
No competitor is as integrated as Tesla is. They all buy modules from suppliers. It would take them ten years to try to do what Tesla is doing now. And then things like the tips about casting. It’s one thing knowing that tip, it’s another actually doing it yourself.
The first thing any GOOD engineer watching the video will think is, “I want to work at Tesla”.
I realize this is very different technology so there is a better chance here, but this is from the same company that said AWD had more redundancy because there were motors front and back. The non-broken one could get you home. Reality appears (from reading here) that the inverter is the most common failure and it takes out the HV system for safety.
Yes, it is very different.
The HV bus is not cheaply partitionable for faults. A short in either drive unit will blow the pack fuse.
The dual steering motors are on dual power feeds each with overcurrent protection. Additionally, 48V is less of a shock hazard than 400V (or higher), so there is no need for isolation checks and only the positive side needs to be switched.
To achieve the same on HV would require two more pyro fuses set to a lower current (which may or may not actually protect the main pack fuse) along with 4 additional contactors (or 3 fuses and 6 contactors on Plaid).
At a system level, the rear inverter is the main brain, so loss of it results in control issues. Steer by wire has triple wheel sensors along with motor, power, positional, and control redundancy.
If anyone has ever driven a car that lacks power steering (1984-88 Pontiac Fiero for me), turning into a turn was heavy/hard when still, but became easier when moving slightly and near effortless when returning to straight. Al it takes is a little throttle.
How Tesla handles a steering gear motor failure is yet to be seen. I’m sure they will knew it safe.
doghousePVD
My grandfather’s car
My wife and I have been driving our X with essentially no power steering for a few weeks. A bit of upper body strength, but we both managed. Finally got an appointment and now it's fixed.
jebinc
Well-Known Member
Just sharing.
teslamotorsclub.com
Cybertruck launch
Does anyone know how fast the cybertruck can charge at a V3 supercharger? The truck takes 800 V and those chargers only go up to 400 V. I haven’t heard if they use a DC to DC converter for this or split the pack in two.
teslamotorsclub.com
Stretch2727
Engineer and Car Nut
A Cybertruck failure will be completely different. You can't assist the one motor that is still working.
My guess is they will throw up an error message to tell you to creep forward to steer. Will be interesting to see if the steering feedback motor has enough resistance to resist heavy input to the steering wheel to give feedback that the wheels are not actually turning. Probably not as this would mean it's oversized just for a failure mode, usually not how Tesla designs.
Anyway, it just a limp mode to get you home. With the right error message I would think most people would understand.
I keep checking for the Cybertruck owners manual. Might help explain this along with how they implemented the 48 volt battery.
When they showed the left controller board, the mentioned 2 x 24V amps which will be upgraded eventually to 48V.
So ethernet and power goes into the board, and the amps on the board drive the speakers...
It is clear that the architecture is based on controlling the car though the controller boards which are connected to the ethernet loop, more connections on each controller means fewer controllers.
We can see plenty of connections on that board, they mentioned it was for the left size (left front) and it includes the window motor control.
It may control?
- Left headlights
- Left indicators
- Left front door opening
- Left front window motor
- Left front door speakers
So is the DAC/amp function on the controller, or is there only one main DAC feeding the controllers and they are amplifying the speakers? The former would give a lot more flexibility in being able to manipulate the sound, and probably implement noise canceling.
We would need to re-watch the video, but they stated that noise cancelling was part of the solution and data for noise cancelling was transmitted on the etherloop.
Buckminster
Well-Known Member
jebinc
Well-Known Member
OOF! More prospective customer “milking”. “Give me a grand now and we will provide you with an EDD of “TBD” or “in 2024” - Tesla
If true, Telsa will invite every reservationists! Yet another “early adopter” perk?
“Why not milk ‘em for another $1000 of interest free money” - Elon
Has anyone confirmed Sawyer’s claim?
Prospective Customers, falling in line (to be milked)…
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Star K1tty
Member
The etherloop stuff they mentioned sounds a lot like EtherCat or a slight variation on it. It’s an open standard used heavily in time critical control systems for things like particle accelerators. If you google around a bit you’ll find some good videos on how it works. It or something much like it is the perfect choice for a car network if you get to design one from scratch.
There is a central head media unit. The difference is that rather than having it direct wired to all speakers and/or amps and microphones, it links via Etherloop to local nodes with the speaker amps and DACs along with microphone amps/ ADCs. Toslink on steroids, if you will (copper vs optical, of course).
With deterministic jitter and latency, the nodes can include a fixed delay to resync the audio outputs, that's the easy part. The more performance requiring aspect is doing:
Microphone(s) -> ADC -> network -> headUnit -> processing -> network -> DAC -> speakers
Fast enough for noise canceling which is dependent on signal phasing of the live noise. Of course, the only new sections are the network transport ones. Signal processing and digital<->analog exist in both implementations.
For reference, on playback 1 uS at 20kHz is 7.2 degrees of phase shift. If noise cancelation is bounded to lower frequencies, that makes it easier, 1 uS at 10kHz is 3.6 degrees.
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