EUC causes minor car crash

[Tilmann]

1 hour ago, Mono said:

I didn't mean to reduce motor rpm as primary control action. I wrote controlled slow down and meant that the speed reduces while the wheel remains forward-backward balanced (assuming there is no further input from the possibly unmounted driver). This comes down to a (slightly?) more sophisticated implementation of tilt-back, AFAICS maybe not trivial but also not that very difficult to do (the Ninebot Mini can do it).

Forgive me, if I'm a bit slow comprehending today. I just don't get the concept of your controlled slow down. So, a sensor indicates, there is no rider on the wheel anymore. As this could be a false alarm, speed is not reduced but tilt back is applied gently enough, that a rider could maintain balance. In case a rider is still on the pedals, he leans back and thus provides the input for the slowdown for a controlled stop (i.e tiltback stays active all the way). I understand the scenario with a rider on the wheel.

I don't understand how that's supposed to work without a rider reacting to the tilt-back. Wouldn't the wheel maintain its speed and increase tilt-back angle until eventually the wheels shell scratches on the ground (or an angle limit cuts power)? As this is supposed to happen gentle enough for a rider to stay on top in case of a false positive, it will take several seconds to get there. At 25 kph and 4-5 seconds for this sequence, your wheel will be some 30 meters down the road and still traveling at 25 kph. What am I missing? Unfortunately, I don't have access to a ninebot mini to help me understanding.

1 hour ago, Mono said:

What we ask for is a small number of false signals, here, say, on average 1 false positive signal per 100000 operating hours. As a false positive doesn't even do any harm, as it just leads the wheel to slow down if the driver does not give any further input, even a much greater number seems perfectly acceptable. 

Agreed, if your theory is correct and the controlled slow down actually works effective enough while false positives remain harmless. 

My benchmark for any safety feature which can actually do harm when fired for no good reason is airbags in cars. Being German, I think of this analogy: At any given time, there may be about 100000 cars traveling on the Autobahn on average at 130 kph. If one of those 100000  driver airbags fires accidentally every hour, we're in for quite a show. Obviously, there are much higher reliability standards plus self monitoring in place to prevent this. Unfortunately, that's science fiction on an EUC scale ... sigh.

[Tim Koffler]

One important thing to remember is that DRIVING IS A PRIVELDGE, NOT A RIGHT.  When you get behind the wheel of a 4 wheeled vehicle (car/truck) you are committing to being responsible for your conduct when driving that vehicle. Period.  If you are stopped and someone hits you from behind that is the other drivers fault. BUT, if they push you into the car in front of you that is yours because you should have left a larger space between yours and the car forward of you.

It is unfortunate that the driver got in an accident.  The fact that there weren't any bikinis around for him to stare at says nothing because if there were would the accident be the woman's fault wearing the bikini?  No.  

The driver of that car is at fault for the accident because he wasn't paying attention to the road. Period. 

 

[Tim Koffler]

On 12/8/2016 at 1:15 PM, Scully said:

I was riding past a queue of traffic, one driver looked at me and rear shunted the car in front.... Ooopsey. lol. 

Again, drivers should be paying attention to the road. They accept that responsibility when they get behind the wheel of a car. Regardless of the type of distraction, they still have a responsibility to handle their car in a safe manner, otherwise they shouldn't be driving.

[Mono]

1 hour ago, Tim Koffler said:

if they push you into the car in front of you that is yours because you should have left a larger space between yours and the car forward of you.

how do you know this?

Here is my thought process: how could I possibly anticipate someone crashing into me from behind such that I could leave enough space? And what if the car crashes with 180mph into me, how much space could I possibly leave to prevent the consequences of this? I would be surprised if this turns out to be correct, if you can prove that someone crashed into you from behind and you were standing and on the brakes all the time. 

[Mono]

On 18/12/2016 at 0:22 AM, Tilmann said:

Forgive me, if I'm a bit slow comprehending today. I just don't get the concept of your controlled slow down. So, a sensor indicates, there is no rider on the wheel anymore. As this could be a false alarm, speed is not reduced but tilt back is applied gently enough, that a rider could maintain balance. In case a rider is still on the pedals, he leans back and thus provides the input for the slowdown for a controlled stop (i.e tiltback stays active all the way). I understand the scenario with a rider on the wheel.

I don't understand how that's supposed to work without a rider reacting to the tilt-back.

Do you know the Ninebot mini? You can steer it with a remote control without a driver. Which should answer the question whether this is possible even if you don't know how. Well, it's in fact exactly as (simple as) pole balancing.

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Wouldn't the wheel maintain its speed and increase tilt-back angle until eventually the wheels shell scratches on the ground (or an angle limit cuts power)?

Exactly to prevent this scratching (or angle), the wheel will (have to) slow down. 

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As this is supposed to happen gentle enough for a rider to stay on top in case of a false positive, it will take several seconds to get there.

How did you figure this out? Do you have the equations? 

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At 25 kph and 4-5 seconds for this sequence, your wheel will be some 30 meters down the road and still traveling at 25 kph.

Well, there are limits to braking from 25km/h to zero, for sure. I am pretty sure though these limits are in favour to the wheel remaining on its tire compared to when it slides on the side or you slide with it. I am also pretty sure that an EUC without driver has not a (much) longer stopping distance than with driver, though one would have to do the calculations to confirm. 

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What am I missing?

Not sure what it is exactly. Maybe you are stuck with the idea that there must be some physical information coming from the driver over the pedals to the wheel. You don't need a driver to let a Segway move around, accelerate and brake and all. For forward-backward control that's exactly the same for an EUC as long as it doesn't fall to the side. 

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Unfortunately, I don't have access to a ninebot mini to help me understanding.

Me neither, so let's dig up a video on youtube, the first which comes up is this one:

https://youtu.be/HEDQixonhcY?t=3m26s

Or this one:

https://youtu.be/WqObT8LAOlY?t=1m0s

[EUCMania]

Use a leach on a EUC will be like this: The teeth will be gone in a few minutes

[One]

On 16.12.2016 at 11:29 PM, Mono said:

It would be better if the wheel would quickly slow down to standstill when no rider is present

How can a wheel be braked without a counterweight (you!)? This seems to me physically impossible.

[Smoother]

21 hours ago, Mono said:

how do you know this?

Here is my thought process: how could I possibly anticipate someone crashing into me from behind such that I could leave enough space? And what if the car crashes with 180mph into me, how much space could I possibly leave to prevent the consequences of this? I would be surprised if this turns out to be correct, if you can prove that someone crashed into you from behind and you were standing and on the brakes all the time. 

@mono, your logic is impeccable as usual, however, after being hit from behind at 180mph, the last thing you need to worry about is "who's going to pay for the car "I" hit. ?

[Tilmann]

@Mono, @One : Now I get it - thanks. It is probably easier to understand looking at a very top heavy toy like this:

The counter weight to facilitate braking is its own weight. To brake, the center of gravity needs to be behind the axis. Starting from a constant motion, it takes a quick acceleration input to tip the center of gravity (CG) some angle to the back and then apply braking force to maintain the lean back angle almost to a stop. When almost at a stop, the controller increases brake force and causes the center of gravity to swing up. Ideally,  the CG is back to a perpendicular position above the axis when the vehicle stops.

I would guess, for most EUCs the CG sits a few inches above the axis due to the battery position, so it should work with EUCs, too. My knowledge of all the physics involved here is just to little to guestimate, how effective that braking action could be. Best angle for braking with good friction would be around 45° lean back, right? But most casual riders probably could not handle that in case a sensor failure triggers it with an unprepared person still on the pedals. Also, motor torque may not be sufficient to sustain braking at such extreme angle with a heavy rider on top. Pheeew, tricky questions galore  -->  --> 

[Tim Koffler]

@MonoI used to work at a car rental agency and would spend a lot of time picking up clients at autobody shops. That is the first time I heard about people getting rear ended and having to use their insurance to cover the vehicle they were pushed into.  Since then it has come up several times with people I know having similar experiences. 

Here's an entry from a legal site in Washington state:

• Because basic traffic laws mandate a driver must be able to come to a safe stop if the vehicle(s) ahead stops or slows down. Incidentally, this traffic rule also governs sudden stops. If the subsequent driver cannot come to a safe stop, chances are he or she is not driving in a safe manner and probably not as safely as the driver in front of him or her.   
• How Does Damage From a Rear-End Collision Belie the Basis of Liability?
• In nearly every rear-end collision insurance claim, vehicle damage tells a great deal about what happened. Specifically, resulting vehicle damage is able to demonstrate and even prove how the accident transpired. If one vehicle's front end is damaged and a second vehicle's rear end is damaged, there is usually no big mystery or doubt surrounding what type of accident occurred. Namely, a rear-end collision must have occurred, in which one vehicle struck the rear of the other vehicle.

I've seen reports of similar laws in Australia, India, England, etc.  So it's pretty much the same.  There are the random outliers where someone went through the courts and fought to not be found liable but those are few and far between.

[Mono]

3 hours ago, Tilmann said:

Best angle for braking with good friction would be around 45° lean back, right?

If you define good friction to mean 9.81m/s^2 limit deceleration, then that looks about right with a rider. Though I don't know why limit friction should be connected to the mass of the earth and it seems the optimal lean back should depend on the weight.

3 hours ago, Tilmann said:

But most casual riders probably could not handle that in case a sensor failure triggers it with an unprepared person still on the pedals. Also, motor torque may not be sufficient to sustain braking at such extreme angle with a heavy rider on top.

Right, but there is nothing to prevent the wheel to remain in its torque limits when decelerating with any rider weight including zero.

[Mono]

5 hours ago, One said:

How can a wheel be braked without a counterweight (you!)? This seems to me physically impossible.

good point. The shell, motherboard, batteries etc still have weight and can produce the necessary momentum. Yet it seems this is one of the rare situations where the weight of the batteries could have a positive effect, in that they could shorten the stopping distance of the driver less wheel. One would have to do the calculations.