How an EMC problem can kill people and a company

[nctnico]

Earlier this month an electric cargo bike got hit by a train killing 4 small children:
https://nltimes.nl/2018/09/24/fatal-train-accident-prompts-cargo-bike-maker-inspect-3500-units
Or better put: the electric cargo bike kept moving (appearantly the brakes didn't work at all) and it ran through the fence of the railway crossing onto the railway where it got hit by a train.

Based on other news articles it seems this isn't an incident by itself and other users also complained about weird behaviour near railway crossings.  IMHO this clearly points towards EMC problems (probably together with some other bad design choices) and it shows how aware designers need to be about EMC problems and how to mitigate them. The company who produces these cargo bikes is likely to go under especially since the Dutch government has revoked the road safety declaration making it illegal to use the particular cargo bikes.

Let it be a warning not to take weird behaviour of an electric/electronic product lightly.

[coppercone2]

it's kind of like ignoring that weird eye twitch people seem to develop after being sprayed with zombie blood.

'it's fine the LCD does that some times'

you sure?

'yea we have been selling this for years'

we need some ww2 era propaganda/infographics signs for the mechanical engineering department that makes everyone's life difficult. 'cable routes WHERE?!?!?!'

[CM800]

"This device complies with Part 15 of the FCC rules. Operation is subject to the following two conditions: (1) this device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation."

I wonder if the train system is at fault also then? Surely it should not be causing harmful interference.

[Ampera]

I think the better question is who is making a road legal vehicle without some form of direct connection manual break, even a separate one for emergencies?

So you're telling me, these electronically controller breaks decided to just stop working in what should be a closed, shielded system, because of EMI from a railroad crossing.

RIP those 4 kids, that's some bullshit.

[glarsson]

I don't think FCC rules are used on train systems in the Netherlands.

Whst kind of bicycle brakes can be disabled by some weak electronic signal?

[rsjsouza]

I don't think FCC rules are used on train systems in the Netherlands.

Whst kind of bicycle brakes can be disabled by some weak electronic signal?

Quite interesting question; I wonder if such brake systems go through the same scrutiny as automotive systems with their dual Cortex R5s in lockstep or other similar crazy paraphernalia.

The EMC standard for EU is usually Directive 2014/30/EU, but it can share some similarities with FCC (probably not Class B for automotive systems).
http://ec.europa.eu/growth/sectors/electrical-engineering/emc-directive_en

[langwadt]

I don't think FCC rules are used on train systems in the Netherlands.

Whst kind of bicycle brakes can be disabled by some weak electronic signal?

it is likely that the brakes worked but it might seem like they didn't if the engine kept pushing when it wasn't expected,
like the Toyotas with "stuck" trottle problem. The rules for electric bike says the motor can only help when you turn the pedals,
so  a bit of noise of the crank sensor is probably enough to get the motor driving when you don't expect it

[coppercone2]

bit of noise causing life critical failure is shameful design

[amyk]

In a product like this, reasonable pressure on the brakes should be required to be capable of overpowering the motor.

[langwadt]

In a product like this, reasonable pressure on the brakes should be required to be capable of overpowering the motor.

and it probably can, but in the confusion and panic of the motor still pushing you might not realize that

https://en.wikipedia.org/wiki/2009%E2%80%9311_Toyota_vehicle_recalls

[Raj]

A complete electrical cutoff switch is a must in every device that has potential to kill.
Cars have keys, that you can turn to shut the off.
table saws have foot/knee kill switch.
petrol pumps have one too.

[nctnico]

A complete electrical cutoff switch is a must in every device that has potential to kill.
Cars have keys, that you can turn to shut the off.
table saws have foot/knee kill switch.
petrol pumps have one too.

According to other Dutch articles: In another near accident the driver was smart enough to turn the 'ignition key' off and thus stopping the cargo bike. IMHO the proper way to design something like this is to disengage the engine through a relay (either interrupting or shorting it) when the brakes are applied.

[Ice-Tea]

I've been following this as well. Seems to be an interesting tale to tell to those who go 'EMC, meh'. Or 'we'll just import some chinese crap, what could go wrong'.

[Raj]

A complete electrical cutoff switch is a must in every device that has potential to kill.
Cars have keys, that you can turn to shut the off.
table saws have foot/knee kill switch.
petrol pumps have one too.

According to other Dutch articles: In another near accident the driver was smart enough to turn the 'ignition key' off and thus stopping the cargo bike. IMHO the proper way to design something like this is to disengage the engine through a relay (either interrupting or shorting it) when the brakes are applied.

BTW, has anyone tried turning off their non electric car in any gear while it's moving.
It turns into a pneumatic abs break without the use of any break. the engine itself makes the car stop.Maybe something with a piston cylinder and a solenoid valve can introduce similar safety feature in electric car

[Ampera]

Or just have breaks that need power/pressure to be off, and have a cut off switch for that power/pressure.

[donotdespisethesnake]

It hasn't been proved that EMC is the cause, that is just a theory. Toyota proved that buggy software can be an issue by itself (which should be a surprise to absolutely no one).

Several design flaws have been identified in these electric vehicles anyway, not surprised they got banned https://nltimes.nl/2018/09/26/stint-cargo-bikes-safe-transport-kids-researcher-says

[Kjelt]

I am not sure it is EMC related but it could be.
AFAIK the reported incidents did not all occur in the vicinity of railroad crossings.

The revocation of the road license by the government was due to the fact that the manufacturer has changed the design since the approval and had not communicated these changes to the government agency. All I heard was that the electromotor was changed to a more powerfull version.
Perhaps the brakes were not upgraded as well, i don't know.

Anyway, the biggest issue is and was that these kinds of electrical equipment that can pose a danger to human life, if it is a cnc machine or other industrial machine or a vehicle like this, it should have an Emergency Stop Button activating a safety relais.
In this case the driver should have pulled the ignition key which was tuck somewhere not easy reachable and also on the brake side so if the brakes were activated the driver should use the other hand to pull the key. Too much trouble for panick situations IMO.
Just as with some other vehicles like lawnmowers it would have been a good idea to equip it with a cord acting like a kill switch.

We have to wait till the final report is in to draw conclusions but for now it looks like a flimsy safety design.

Edit: the way it should have worked is that the driver should release the throttle handle at the right and then the stint would shut down. This is illogical since if you have an emergency situation you want to control the verhicle with both hands, there should have been an easy reachable emergency button.

[coppercone2]

im sure the reason why they did not have a kill switch is because BOM.

No fucking way a manufacturing company that hired assemblers and managers and engineers managed to miss this detail. It was a design choice. There was a risk assessment matrix that someone decided to tick 'no risk'.

In those assessments, when you tick 'no risk' it tends to make design easier and cheaper. At least it assures you have a signed fall guy tho. I call it a hot potato matrix.

[nctnico]

I am not sure it is EMC related but it could be.
AFAIK the reported incidents did not all occur in the vicinity of railroad crossings.

The revocation of the road license by the government was due to the fact that the manufacturer has changed the design since the approval and had not communicated these changes to the government agency. All I heard was that the electromotor was changed to a more powerfull version.

I think this is just to make the legal part simpler at the government's side. It is much harder to prove the EMC issue is there especially if the vehicle has passed relevant EMC testing. It wouldn't surprise if it turns out the rules which apply to these kind of vehicles aren't strict enough. Anyway, by revoking the road license the vehicle has to be tested for safety again.

[Mr. Scram]

It sounds like how the reaction is to any new and relatively unknown thing when something goes awry. Driverless cars also get scrutinized a lot more than regular cars, even though many more people die horrible deaths in the latter every day. Yeah, this company is screwed.

[T3sl4co1l]

BTW, has anyone tried turning off their non electric car in any gear while it's moving.
It turns into a pneumatic abs break without the use of any break. the engine itself makes the car stop.Maybe something with a piston cylinder and a solenoid valve can introduce similar safety feature in electric car

I have.  With the particular (pretty average conventional, AFAIK) gasoline engine in my car, opening the throttle doesn't seem to do anything.  It moves air (the exhaust sound changes), but there is little backpressure, so the load isn't much more than the resistance of the engine moving alone.

A turbo diesel may be more effective, although there may be reasons not to do that (large air charge = high peak air temperature --> unintended combustion of residual fuel and engine oil --> actually generating more power than you're spending, or if your oil seals are very worn, runaway acceleration?).  AFAIK, engines designed for that kind of braking have an air release, which I guess would occur near TDC, or as an exhaust restriction, and it is the pressure drop that consumes power.  Downside being the incredibly loud noise thus generated, and the frequent sight of "engine braking prohibited" as you cross the city line...

Tim

[nctnico]

BTW, has anyone tried turning off their non electric car in any gear while it's moving.
It turns into a pneumatic abs break without the use of any break. the engine itself makes the car stop.Maybe something with a piston cylinder and a solenoid valve can introduce similar safety feature in electric car

I have.  With the particular (pretty average conventional, AFAIK) gasoline engine in my car, opening the throttle doesn't seem to do anything.  It moves air (the exhaust sound changes), but there is little backpressure, so the load isn't much more than the resistance of the engine moving alone.

Then I think your car is broken. Either gasoline or diesel engine brakes with the throttle closed due to compression. This is useful (and strongly recommended) when going down long slopes because your brakes will burn up if you use them. Having the ignition on or off doesn't matter if you have a mechanical coolant pump because that will keep circulating cooling water throughout the engine. Big trucks have an extra valve in the exhaust to create extra back pressure.

[langwadt]

BTW, has anyone tried turning off their non electric car in any gear while it's moving.
It turns into a pneumatic abs break without the use of any break. the engine itself makes the car stop.Maybe something with a piston cylinder and a solenoid valve can introduce similar safety feature in electric car

I have.  With the particular (pretty average conventional, AFAIK) gasoline engine in my car, opening the throttle doesn't seem to do anything.  It moves air (the exhaust sound changes), but there is little backpressure, so the load isn't much more than the resistance of the engine moving alone.

Then I think your car is broken. Either gasoline or diesel engine brakes with the throttle closed due to compression. This is useful (and strongly recommended) when going down long slopes because your brakes will burn up if you use them. Having the ignition on or off doesn't matter if you have a mechanical coolant pump because that will keep circulating cooling water throughout the engine. Big trucks have an extra valve in the exhaust to create extra back pressure.

Diesel engines doesn't have throttles, so they need different ways of achieving engine braking.
There are two kinds, one is a valve in the exhaust, the other noisy one opens the exhaust valve at the end
of the compression stroke dumping the compressed air out the exhaust

[nctnico]

This is getting off-topic but in a regular car the (high) compression in a diesel engine is enough to achieve engine braking. Remember movement is converted into heat which is dissipated in the cylinder head and the remaining hot air is dumped into the exhaust when the exhaust valve opens. Only trucks have extra measures to get more braking from the engine.

[langwadt]

This is getting off-topic but in a regular car the (high) compression in a diesel engine is enough to achieve engine braking. Remember movement is converted into heat which is dissipated in the cylinder head and the remaining hot air is dumped into the exhaust when the exhaust valve opens. Only trucks have extra measures to get more braking from the engine.

with the throttle open you don't get as much engine braking because the air acts like a spring and give you much of the energy used to compress air back in what would have been the power stroke