Failsafe mechanisms in modern cars? - Page 1
Forum section: electronics / general

author: member_xyz
author_rank: Contributor
timestamp: January 09, 2014, 04:12:27 am
content: Woman locked inside Audi Q3 on 41-degree day.http://theage.drive.com.au/motor-news/woman-locked-inside-audi-q3-on-41degree-day-20140108-30hde.html"Technicians determined that electronic interference had blocked signals from the Porsche's wireless smart key and that had caused the doors and windows to lock."Hmmm.

author: notsob
author_rank: Frequent Contributor
timestamp: January 09, 2014, 04:50:24 am
content: So, if you saw the Mythbusters episode, you need to keep an automatic centre punch in your keyless car, so that you can break a window to get out in case of emergency.

author: peter.mitchell
author_rank: Super Contributor
timestamp: January 09, 2014, 05:05:03 am
content: I just keep a glass cutter in the glove box, never know when you'll need it, if some one has been in a car accident, if you crash into a river, or if the above situation is needed.

author: Unknown
author_rank: Unknown
timestamp: January 09, 2014, 05:51:48 am
content: QuoteThere's some critical details missing from this story somewhere. I call hoax.

author: amyk
author_rank: Super Contributor
timestamp: January 09, 2014, 01:10:31 pm
content: ...so the door handles and the locking stems on modern cars are no longer physically connected to the locking mechanism?

author: romantronixlab
author_rank: Regular Contributor
timestamp: January 09, 2014, 01:30:14 pm
content: Quote from: amyk on January 09, 2014, 01:10:31 pmNot possible, as it is a safety issue as for example electronic transmission they are fully electronics but still has a mechanical linkage for Park and Neutral just in case the car goes haywire. The same goes for the E-brake there are electronic systems using the ABS module to apply it but still there is a physical connection to the brakes.As the handle goes today's systems are very simplistic only a single wire from the handle to the latch and for safety I think it is going to be that way until who knows when also by pulling it automatically removes the lock (drivers side)on most cars.

author: dr.diesel
author_rank: Super Contributor
timestamp: January 09, 2014, 01:43:49 pm
content: My Mom got locked out of her 2013 Toyota, she left the keyfob in the front seat and locked the doors. Toyota said that wasn't possible, pift, nothing built on software will ever be 100% "failsafe".I NEVER lock my vehicle doors, anywhere, they could remove the door locks and I'd be OK with it.

author: SeanB
author_rank: Super Contributor
timestamp: January 09, 2014, 02:13:30 pm
content: A lot of modern cars have security locksets, such that if the vehicle is locked with the central locking the interior handles and unlock buttons are disabled either electrically or mechanically. This is to sow down car thieves and smash and grab artistes that break a window from unlocking the car and trunk to steal whatever is in it. As a safety feature though the SRS systems ( airbag controllers) often are programmed to automatically unlock the doors when deployed. Thus if the airbag deploys the doors are unlocked, so that the people can be rescued. Cars without airbags often still have an acceleration sensor to unlock the doors, so that the same can be done.

author: wiss
author_rank: Frequent Contributor
timestamp: January 09, 2014, 03:09:00 pm
content: What if the battery runs out? Just recently had an alternator failure and the warnings didn`t come on until the battery was almost run out.

author: SeanB
author_rank: Super Contributor
timestamp: January 09, 2014, 03:22:27 pm
content: Break a window....... I keep a tool in the car to do that on purpose, it will easily break a window from the inside or the outside.

author: peter.mitchell
author_rank: Super Contributor
timestamp: January 09, 2014, 03:31:55 pm
content: my car has no "stems" or "tabs" on the rear doors, they have to be locked by central locking; im unsure if you can unlock them from the inside just using the handle ( i don't spend much time in the back of my car with the doors locked)

author: member_xyz
author_rank: Contributor
timestamp: January 10, 2014, 12:23:37 am
content: Update to yesterdays newspaper article.http://theage.drive.com.au/motor-news/push-for-door-release-mechanism-after-driver-trapped-in-audi-20140109-30kkp.html"A spokeswoman for the NRMA said roadside assistance crews in NSW and the ACT were called out to about 2000 cases of people, mainly children, trapped inside cars in the 2012-13 financial year - a 12 per cent increase on the previous year."

author: Skimask
author_rank: Super Contributor
timestamp: January 10, 2014, 04:48:02 am
content: P.E.B.S.W.A.D.S.

author: Stonent
author_rank: Super Contributor
timestamp: January 11, 2014, 01:36:31 am
content: On my Jeep I can't open the back hatch without power. The handle is a rubber membrane with a button under it.That was annoying when my battery went dead and I couldn't get to my tool box to undo the cables.You first have to unlock all the doors using the electrical door lock button (that needs power) and that unlocks the back, but you also need electrical power to release the latch that keeps it closed.

author: mc
author_rank: Regular Contributor
timestamp: January 11, 2014, 02:54:18 pm
content: Quote from: romantronixlab on January 09, 2014, 01:30:14 pmThere are plenty electronic transmissions with no external mechanical linkages, and have been for a decade that I can think off. They simply have several failsafes programmed in, with the final one being the person behind the wheel.Electronic brake systems are a bit different. In the passenger car area, they're relying on the ABS module to pressurise brakes, but they've been doing that for years to implement traction control, so upping capacity to apply all brakes isn't really a major thing.The normal brakes are still relying on hydraulics to generate pressure. For all braking systems you still need a mechnical failsafe, so for car manufacturers, as they have to fit the hydraulic system, they may aswell keep using it.However modern lorries are where the real advances are. The first 80-90% of brake pedal travel is purely electronic, with a few modules around the vehicle activating air solenoids to apply pressure to brakes, with only the last 10-20% travel being where the EBS system gets overidden and a mechanical valve gets opened. The ABS system is seperate, so provided there's not a major electric failure (highly unlikely without some kind of prior warning, as truck electrics are pretty bulletproof), you don't lose all electronic braking aids.For truck manufacturers, EBS is dictated by legislation (certainly within the EU), however to simplify things they usually install it over entire ranges. Plus it's used for braking with collision avoidance systems, that become a requirement sometime this year.

author: Rigby
author_rank: Super Contributor
timestamp: January 11, 2014, 06:23:47 pm
content: Quote from: dr.diesel on January 09, 2014, 01:43:49 pmThat's not true at all. Software can indeed be 100% failsafe. If it interfaces with a physical system, then that physical system must also be 100% failsafe, of course.Making things failsafe is much harder than it sounds, and that's why few things are truly failsafe.

author: dr.diesel
author_rank: Super Contributor
timestamp: January 11, 2014, 06:52:14 pm
content: Quote from: Rigby on January 11, 2014, 06:23:47 pmBut software runs on physical hardware. Even if your code is perfect, multi-million dollar systems mess this up all the time, your faced with mystery bit flips.I have yet to see any software based system advertise 100% uptime, because it can't be done. Billion dollar power houses spending billions can't even do it, will never happen.

author: Unknown
author_rank: Unknown
timestamp: January 11, 2014, 07:10:40 pm
content: Quote from: dr.diesel on January 11, 2014, 06:52:14 pm100% uptime and failsafe are not the same thing.

author: dr.diesel
author_rank: Super Contributor
timestamp: January 11, 2014, 07:16:01 pm
content: Quote from: Lurch on January 11, 2014, 07:10:40 pmWell, when it's not up, how can it be safe? Or lock the doors, or unlock the doors, deploy the airbag, call for help etc?

author: Unknown
author_rank: Unknown
timestamp: January 11, 2014, 07:21:48 pm
content: Quote from: dr.diesel on January 11, 2014, 07:16:01 pmWell, depends on the failure mode and what constitutes a failure, and also depends how complex the electronics are. Take for example a solenoid door lock. Apply power - door locks. Power fails, door unlocks. Failsafe. So this is failsafe with uptime !=100%.Now if you add a process of external logic to control that voltage then it may not be failsafe, depends on the complexity of the logic.

author: dr.diesel
author_rank: Super Contributor
timestamp: January 11, 2014, 07:29:57 pm
content: Quote from: Lurch on January 11, 2014, 07:21:48 pmDoor locks are not held energized to lock anyhow, even if they were what if a short to power happened during a crash, locking the doors? Takes power to lock, power to unlock, what decides this action?

author: mc
author_rank: Regular Contributor
timestamp: January 11, 2014, 07:34:47 pm
content: Quote from: dr.diesel on January 11, 2014, 07:16:01 pmYou're right in that it's only failsafe when it's working, however part of the failsafe is it detecting that there's a fault and registering said fault. All critical systems have a failsafe. Airbags have two circuits in series which both need to be activated to detonate airbags. Any electrical ABS system fault doesn't stop your brakes mechanical system from working.Doors locking/unlocking is not critical. Modern cars should unlock doors in the event of an accident (it should happen around the time the airbags go bang, at which point power shouldn't of been wiped out), however if you're in that serious an accident where the doors don't unlock, I very much doubt you'd be able to get out the car yourself anyway.

author: Unknown
author_rank: Unknown
timestamp: January 11, 2014, 07:44:23 pm
content: Quote from: dr.diesel on January 11, 2014, 07:29:57 pmI never said they were.

author: saturation
author_rank: Super Contributor
timestamp: January 14, 2014, 07:37:31 pm
content: I've worried about the electronic locks in door and windows for decades, only recently have fail safe's been designed into some, not all. Many luxury cars tend to have it. My personal response to it is to own cars with manual controls for issues that are safety related: door locks, crank windows, seat adjusts, rear view and side mirrors, seatbelts etc.,

author: m100
author_rank: Regular Contributor
timestamp: January 14, 2014, 07:46:26 pm
content: Quote from: amyk on January 09, 2014, 01:10:31 pmA number of central locking mechanisms effectively fully disconnect the door handle from the rest of the lock mechanism. If locked then a pull on on the handle just moves a linkage that compresses a spring to protect a limit stop. Lose the electrics and you are locked out (or in) unless you have a backup mechanical key. Also the locking stems can retract fully into the door trim so are effectively useless for mechanical 'open' overrides.

author: Rerouter
author_rank: Super Contributor
timestamp: January 14, 2014, 07:48:15 pm
content: Crank style windows still work when your a few meters underwater and still sinking,

author: saturation
author_rank: Super Contributor
timestamp: January 14, 2014, 08:43:01 pm
content: Quote from: Rerouter on January 14, 2014, 07:48:15 pmhttp://mythbustersresults.com/episode72http://www.wishtv.com/news/local/car-window-type-crucial-when-sinkingIn many small islands [as well as highways in Florida], roads are very close to water and if you veer off in an accident, typically you'll land in beach deep water, about 3-10'. The deeper ones can drown you. But most cars in FSM or many undeveloped countries used to have manual doors and crank windows, and most all folks easily escape by rolling windows down before sinking, and crawling out. Also, power doors and windows malfunction far sooner than simple mechanical ones, and cost a lot to repair.

author: Rigby
author_rank: Super Contributor
timestamp: January 15, 2014, 08:43:48 pm
content: Quote from: saturation on January 14, 2014, 08:43:01 pmI don't know about that. I've never had to replace a power door lock or power window mechanism in any car I've owned, but I've had to replace numerous wind-up window cranks and manual lock handles. I've also never had a single issue with a power door lock, and lots of issues with manual door locks that prevented me from unlocking a locked door or locking an unlocked door.Anyone have stats on this? Anecdotally, power windows & door locks have been far, far more reliable for me.

author: BillyD
author_rank: Regular Contributor
timestamp: January 16, 2014, 04:06:21 pm
content: My last car was a Golf and it had the option of deadlocking the doors whereby for extra security you could disable the interior handles and buttons making it impossible to unlock the doors from inside. So it was certainly possible to at least trap someone inside, or theoretically even get accidentally trapped inside depending on the failure mode.Another observation on its locking system was that if you press the Lock button inside the car, the solenoid would not click if the doors were already locked. However if you press the Unlock button, the solenoid would always click, regardless of whether the doors were already locked. So I would consider that a simple and sensible fallback of sorts which meant that you couldn't get locked into the car if the car ever incorrectly 'thought' that the doors were already unlocked.A friend of mine has a new-ish Passat which has an electric parking brake. So instead of the traditional brake handle between the front seats, there is a push button on the dashboard and you can hear motors engaging the brakes in the rear hubs. There is no mechanical link to these brakes so without power you can't engage or disengage them. Personally I don't like that at all.