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Investor Engineering Discussions
- Thread starter MC3OZ
- Start date
JRP3
Hyperactive Member
Was thinking about drive by wire and every time they are brought up it seems like redundancy requirements are big. I think this is why the traditional steering assembly has lasted so long. But very possible Tesla pulls the plug with Cybertruck or Gen 3. The Gen 3 potentially lacking a steering wheel will clearly need to address this some other way.
Seems like they could run 2 buses, each would control one side of the vehicle and there would be a bus for each side. For most accessories, there wouldn’t be redundant signals, but for steering, braking, and other safety related equipment you would signal on both busses. Brakes and steering controllers would be able to act on signals from either bus.
Essentially making the actual brake pedal and steering wheel the only single point of failure. Even there Tesla could have FSD take control if there is a steering wheel failure.
Seems like they could run 2 buses, each would control one side of the vehicle and there would be a bus for each side. For most accessories, there wouldn’t be redundant signals, but for steering, braking, and other safety related equipment you would signal on both busses. Brakes and steering controllers would be able to act on signals from either bus.
Essentially making the actual brake pedal and steering wheel the only single point of failure. Even there Tesla could have FSD take control if there is a steering wheel failure.
Knightshade
Well-Known Member
If they're expecting to be building Gen3 in 2024 it's going to have a steering wheel. For certain.
Might well be modular and easily removed, but it'll be there. Pedals too.
Might well be modular and easily removed, but it'll be there. Pedals too.
JRP3
Hyperactive Member
More accurately installs the plug
I'm assuming the rear steering for Cybertruck is drive by wire with a default return to straight mechanism.Return to center, if powered. Assuming it uses this:More accurately installs the plug
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JRP3
Hyperactive Member
JRP3
Hyperactive Member
My thinking is there are very rare occasions where you need rear steering, obviously most vehicles don't have it, so getting somewhere is more likely to happen if the rear steering fails to the straight ahead position.
The wire harness patent seemed to indicate a bidirectional power flow loop, with each node potentially being able to receive data and power from 2 separate directions, Hence a single break in the harness would not necessarily knock a node offline, From the node to the device being controlled is likely to be a single set if wires, but a short run.
I'm not really convinced electronically controlled brakes will be less reliable than hydraulically controlled brakes. A single hole in the pipes can cause off a the brake fluid to leak out, potentially losing all 4 brakes at once. For electronic control, the most likely failure mode is 1 out of 4.
Like everything else it can be tested and the safest path is make the rear brakes electronic first, keeping the front brakes hydraulic until reliability is confirmed in real world use.
I'm not really convinced electronically controlled brakes will be less reliable than hydraulically controlled brakes. A single hole in the pipes can cause off a the brake fluid to leak out, potentially losing all 4 brakes at once. For electronic control, the most likely failure mode is 1 out of 4.
Like everything else it can be tested and the safest path is make the rear brakes electronic first, keeping the front brakes hydraulic until reliability is confirmed in real world use.
All brake systems are dual loop, one hole still gives braking on two wheels.
Good point, but I still wonder if there is a scenario (with a single hole) where all of the fluid can leak out, or at least where the fluid level can drop, or air bubbles can be introduced. They have probably though of that, I imagine there would be some kind of valve to shut the leaking section off from the good section?
Yep, master cylinders have two sections so you can't lose all the fluid in both.
JRP3
Hyperactive Member
I think electronic brakes might need 2 separate independent power feeds per caliper, each with it's own backup power source near the calipers, and redundant signal lines. That way if one power or signal line fails there is a backup, if both power feeds to a caliper fails there is still backup power, and if the main pack goes down there would still be enough power for at least one braking event on each wheel. Maybe overkill but the extra cabling seems like cheap insurance, and possibly a super capacitor could have enough power for a one time backup event.
bkp_duke
Well-Known Member
Or you could just have an independent power feed per brake. 4 points. One of them starts to fail you still have a lot of braking power in the other 3 to come to a stop.
I haven't read about Brembo's design, I would be interested to know what approach they take.
willow_hiller
Well-Known Member
Very curious to see some YouTubers test this:
Green seems to be implying it will start inferior to the USS-version, but eventually I imagine each approach will have strengths and weaknesses.
Green seems to be implying it will start inferior to the USS-version, but eventually I imagine each approach will have strengths and weaknesses.
Buckminster
Well-Known Member
Or Tesla is working/buying from Niron. They often speak in the present tense stuff that is 2 years away.
JRP3
Hyperactive Member
Yes that seems much more likely. I didn't get the impression that Tesla had these motors ready for production anytime soon.
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