Re:Preliminary NTSB report on Tesla crash
by niels_olson on Tuesday July 26, 2016 @05:53PM
(#12168993)
To answer the question, it's quite possible to have a braking system that engages in the event of power failure. I've heard of even double-redundant braking systems, so three total systems have to fail before the brakes fail. It was on a Rolls Royce as I recall. The owner was crowing about how his brake job cost more than my car.
I'm not saying it's infeasible technologically. I'm saying it's possibly a terrible idea to have brakes auto-engage upon failure of the power system.
Re:Preliminary NTSB report on Tesla crash
by outworlder on Tuesday July 26, 2016 @05:41PM
(#12168922)
> Additionally, since powered items like anti-lock brakes are now unavailable
Are they unavailable? Electric cars have a main traction battery plus the conventional 12V battery that all cars have.
If there is no power than chances see there is limited steering as well. Probably safer to have motionlessn 2-ton rock rather than a 2-ton ballistic missile.
Re:Preliminary NTSB report on Tesla crash
by stouset on Wednesday July 27, 2016 @07:22PM
(#12177255)
Power steering might be off, but that doesn't mean steering is limited.
A motionless 2-ton rock in the middle of a busy interstate because of a power blip is a terrible idea. And again, how hard exactly should the system brake? Pick a value between 0% braking and 100% braking that brakes maximally without locking up the brakes.
A 2-ton brick spinning down a busy interstate because the brakes locked up is arguably even worse than a motionless one.
If your battery dies while the car is running (say, even, that something causes a physical disconnect between the batteries and the rest of the car — a wiring fault, or whatever). Ideally you would be able to pull to the side of the road while your vehicle coasts, braking as necessary.
If the system detects a power disconnect and instantly engages all brakes, does that help or harm? Additionally, since powered items like anti-lock brakes are now unavailable, how hard should the brakes be engaged? Fully? Slightly?
Slamming on the brakes in a failure scenario is not automatically the right answer. Odds are it's probably the wrong answer more often than not.