Vehicles like Segway

[runway10]

Does anybody know about ANY other vehicle that has electric brakes only? Most EV-bikes, mopeds, scooters and cars have discbrakes as well... I've found lots of those but none without...

[Brandis]

For most vehicles there is no need for electric brakes only. The Segway couldn't use mechanical brakes, as this would result in a faceplant.

Marc

[Stan671]

Most sophisticated electric vehicles will use regenerative braking to some extent. This works by using the the motor to act like a generator to recharge the batteries when slowing down. But his is just not enough stopping force for these vehicles and therefore there are regular brakes also.

The Segway takes the regenerative braking one step further and the electronic controls not only pull power from the motors to charge the batteries, but will also provide a reverse current to the motors when needed to provide a stronger braking effect.

As someone else mentioned, this is the only way the Segway can do it without falling over. A mechanical braking system would not be able to be so fast acting and precisely controlled by the computers as the regenerative and reverse current braking system can be. The computers in the Segway need absolute control over even the tiniest movement of the wheels (motors) in order to keep the machine upright.

[runway10]

The reason for my question is the legislation process. If we can find another vehicle that only has electric brakes the chances for approval will improve. It seems some countries legislagtion require some sort of mechanical brakes . Another approved vehicle without mechanical brakes would be a good reference. A rumor is an older generation of Mercedes E-Klasse only has it, lots of problems too. Is this true?

[KSagal]

Interesting that you went to Germany for that Mercedes E Class...

I do not know of a vehicle, but one of my professional responsibilities over the past 12 years include being a representiative for the manufacturer of German paper handling equiptment. The Bowe paper cutter (A large high speed device that takes those huge rolls of paper printed on commercial printers, and cuts them into the 8.5 x 11 paper we expect to see in our bank statements and phone bills) uses a DC stepper motor that starts and stops thousands of times per hour, and it has electric only brakes, and incredible accuracy.

So, while I cannot offer up a vehicle, the technology has been used in other applications for some time now. I am sure there are other applications out there with similar stories...

[seglander]

I am not 100% sure but you might want to look at some hydraulic drives in industrial machinery such as excavators, florklifts, cranes, crawlers etc. I imagine that they will have some sort of mechanical brake also to prevent rolling when turned off but in regular operation they may not use it.

[Drewi216]

My dad owns a large sized landscaping company and we have several excavators and crawlers, but the way the break system works on the excavator is just the lack of movement in the hydraulic fluid. Since the fluid doesnt compress like air would, nothing in the machine would move.

[Sharkie]

Does anybody know about ANY other vehicle that has electric brakes only? Most EV-bikes, mopeds, scooters and cars have discbrakes as well... I've found lots of those but none without...

Well, my old mobility scooter had only electric brakes, although I'm not sure I'd call it a vehicle, more of a frustration generator! :-)

Jim

[dexter]

Many modern rollercoasters and pittfall-type amusement rides use only magnetic brakes.

Kingda-Ka at Six Flags Great Adventure for example has a hydraulic propulsion system and magnetic braking. Some launched coasters use magnets for propulsion and braking.

AFAIK the magnetic brakes on these rides are the "final word" i.e. they are used to brake the train at the end of the ride AND are used for emergency stopping should a failure occur... there are no "mechanical" brakes in place at all on these rides... again AFAIK.

[guyler]

The maglev (magnetic levitation) trains are propelled and braked by electrical magnetic force. They have wheels--which are used prior to levitation--which do not have brakes. These trains can be found in Germany, China, and Japan.

Comparing a Segway with a maglev train may be a stretch, but what do I know?

[Isidore]

What makes a Segway different is that the same mechanism that does the braking, also keeps the machine from falling over in normal operation. This means that it is impossible to operate a Segway with faulty brakes. This is the kernel of the issue and it is the point that the legislators miss. Any other vehicle with electric brakes can still go without it's braking system functional (even if just rolling downhill) so they need a backup mechanical braking system. If your segway brakes have failed, you will know it immediately by the sound of skin scraping on pavement

[KSagal]

I agree with this latest area of consideration and go one further... It will not only not work if the brakes don't work, but it is one of the only transportation devices that simply cannot coast...

When I have mentioned this in the past, I get a lot of raised eyebrows, and scratched heads...

The machine cannot coast at all. It powers up and down hills, or it would not be able to stand upright, so it not only will not work if the brakes go out, it cannot even roll down a hill, and therefore it needs no friction brakes to stop the coasting...

[bentbiker]

If your segway brakes have failed, you will know it immediately by the sound of skin scraping on pavement
I don't disagree with you, but I don't think that explanation would encourage them to see the unit as particularly safe.:)

[runway10]

One issue is parking. Once the power is off there is no braking unless the machine is in alarm mode. A handbrake would solve things. Again, only a stupid person would leave his Seg on a slope... well...

I suspect the lack of a pedal or grip contributes to the fear of acceptance...

One technical solution to that is to introduce a handle that simply trims the horizontal plane so the machine tilts backwards and brakes... It is of course against the dynamic principle of braking with a Segway and the basic idea. Technically its something that only Segway can do... But if that is what it takes to pass the machine, that is probably what Segway will do in the future.

Thanks Dexter and Guyler. Clever, clever! Thanks everbody else too. Keep coming with good ideas. Brings us hope.

[Sal]

If your segway brakes have failed, you will know it immediately by the sound of skin scraping on pavement

For those posters who implied on the "perceived lack of safety" of the Segway due to the lack of brakes. I think the gap in legislators deeming the Segway unfit for use because it doesn't have a brake doesn't rest with having Segway make any changes to the machine (many have been suggested herein), instead we should encourage the election of better-informed legislators, or educate those currently in office.

Getting back to the topic at hand: I think Karl said it best when he mentioned "the machine does not coast at all." That is exactly how I describe the machine to folks when they ask me how it works, and ask me if the machine has brakes... I never say that the machine doesn't have brakes, I say the machine does not coast, it's motors are always active in maintaining speed and stability no matter the situation.

-Sal

[BillPaxton]

My wife's Ford Escape hybrid has 100% electric braking and steering systems (as opposed to hydraulic) however I don't think that's really what you mean as they still rely on calipers pressing against a moving disc. I'm not sure about the braking on my Honda Civic hybrid although it does have regenerative brakings systems which activate both when actively braking as well as when coasting or decelerating. Same with the Ford.

[bystander]

My understanding is that brakes on electrics / hybrids are both mechanical and regenerative.

When gently braking, both sets of brakes are engaged simultaneously. When the system determines that the regenerative circuit is in fact functioning and drawing power, the mechanical brakes are eased off, and the regenerative system takes up the full load. If the brakes are "stomped on" the mechanical system is kept engaged at all times.

If the mechanical system only kicked in _after_ a fault was detected in the regenerative system, an unsafe braking distance would result.

If the mechanical system operated at all times, in tandem with the regenerative system, the regenerative system would not be as effective.

So it's a compromise, in order to keep things safe.

[BillPaxton]

My understanding is that brakes on electrics / hybrids are both mechanical and regenerative.

When gently braking, both sets of brakes are engaged simultaneously. When the system determines that the regenerative circuit is in fact functioning and drawing power, the mechanical brakes are eased off, and the regenerative system takes up the full load. If the brakes are "stomped on" the mechanical system is kept engaged at all times.

If the mechanical system only kicked in _after_ a fault was detected in the regenerative system, an unsafe braking distance would result.

If the mechanical system operated at all times, in tandem with the regenerative system, the regenerative system would not be as effective.

So it's a compromise, in order to keep things safe.

I wonder what happens when your battery is fully charged and you brake heavily. Someday a straight-faced winky will appear on my dashboard in bumber to bumber traffic and the steering wheel will start shaking...

Anyone know about the Tesla braking system? Probably the same as a hybrid but its the only "pure electric" I'm aware of besides those little ones that look like smart cars.

[KSagal]

I used to carry a small 5 pound boat anchor with me. If people got to the point where they really wanted to see the brakes, I could throw it out...

I threatened to throw it many times but only did one time... THat day I had a cord tied to it and to my beltloop...

I now have electronic brakes... So I carry an old computer monitor to toss... LOL... Actually this last entry is not true...

[BillPaxton]

I used to carry a small 5 pound boat anchor with me. If people got to the point where they really wanted to see the brakes, I could throw it out...

I threatened to throw it many times but only did one time... THat day I had a cord tied to it and to my beltloop...

I now have electronic brakes... So I carry an old computer monitor to toss... LOL... Actually this last entry is not true...
the visual image of you going down the road with a 5lb anchor in one hand and a foam brick in the other ...

[SEGsby]

The closest vehicle that I can find to the Segway, in terms of the electric motors directly actings as the breaks-- is the QED Mini Cooper Prototype.

Each wheel has it's own motor:

http://www.treehugger.com/files/2006/08/the_hybrid_mini.php

SEGsby

[runway10]

Thanks Segsby!

This is exactly what I'm looking for! One of those that are streetlegal would put an end to the mechanical brake issue...

[joe]

This is exactly what I'm looking for! One of those that are streetlegal would put an end to the mechanical brake issue...

Agreed. But... I'd like a parking break at least! Note the wooden wheel chocks in the picture! :rolleyes: :D

--
Johannes

[BillPaxton]

that article is almost a year old - I think it was only a concept. My car (Honda Civic Hybrid) claims to be the current 'highest MPG Hybrid' at 51mpg - don't know if that's true about it being the highest but I can tell you with my lead foot and 37 mile commute to work, I average 46mpg. If what Honda says is true tho, then either this article has factual problems and should not be considered a good source of data for a debate or it does not yet exist in production which again makes it not your best candidate. The Zap Obvio on the other hand(http://www.zapworld.com/ZAPWorld.aspx?id=388) is 100% electric - not a hybrid - and it is currently in production. Also - regenerative braking does not mean lack of a disc/caliper system as you will note in the Obvio pages, and I doubt any auto manufacturer would limit braking on a car that weights over 1000lbs to reversing current to motors. Half a ton capable of moving 70MPH needs some serious stopping power.

I'm also not sure a legislator would buy the leap from electric car to Segway even if it were 100% current induced braking - weight and size dissimilarity is enough to derail the argument if the legislator hearing you decided the debate needed to end quickly. I'm not saying don't try, I'm just saying don't just consider your logic being correct when arguing with a politician, consider how a politician can make your logic look fuzzy. To paraphrase Nick Naylor, "I didn't have to [prove I wasn't wrong]. I proved that you're wrong, and if you're wrong I'm right."

[KSagal]

Agreed. But... I'd like a parking break at least! Note the wooden wheel chocks in the picture! :rolleyes: :D

--
Johannes


That is the hallmark of this cutting edge technology. Segway uses the same parking "assistors".

[GadgetmanKen]

I personally wouldn't want electric braking on anything. Driving many 2nd hand, third gen autos I can think of numerous times when my car had died, or stalled and had to stop suddenly. With hydraulic brakes its no problem till you have the air boost systems in later models. With no air from the running engine its a guess if you will stop in time when they stall. Now, I can remember times when I had a loose or dying battery connection and the car stalled say after hitting a pothole, if I had electric brakes and had a loose connection, or an overloaded, or weak battery system I think I would be in a heap of trouble. As for having magnetos built into each wheel, rim, brake drum, or rotor, would be nice in the effect of regeneration storage power, but I would not rely on electronic brakes. I think of electronic brakes as in a Segway (which is basically switching the current the opposite direction) to stop you is OK for a Segway but not a car. Its just got too much weight and mass and momentum. For electric brakes to work IMO they would have to be similar to the way the new antilock brakes work with the multiple pulses say of a solenoid against the pads to work. But there in again, if you have a battery short, or connection cut off at the wrong time you're toast. Having electric assist for anti lock would to me be a better solution to add to hydraulic brakes. I'm from the old school. :)

[KSagal]

I personally wouldn't want electric braking on anything. Driving many 2nd hand, third gen autos I can think of numerous times when my car had died, or stalled and had to stop suddenly. With hydraulic brakes its no problem till you have the air boost systems in later models. With no air from the running engine its a guess if you will stop in time when they stall. Now, I can remember times when I had a loose or dying battery connection and the car stalled say after hitting a pothole, if I had electric brakes and had a loose connection, or an overloaded, or weak battery system I think I would be in a heap of trouble. As for having magnetos built into each wheel, rim, brake drum, or rotor, would be nice in the effect of regeneration storage power, but I would not rely on electronic brakes. I think of electronic brakes as in a Segway (which is basically switching the current the opposite direction) to stop you is OK for a Segway but not a car. Its just got too much weight and mass and momentum. For electric brakes to work IMO they would have to be similar to the way the new antilock brakes work with the multiple pulses say of a solenoid against the pads to work. But there in again, if you have a battery short, or connection cut off at the wrong time you're toast. Having electric assist for anti lock would to me be a better solution to add to hydraulic brakes. I'm from the old school. :)


I agree with some of your comments, but would put in a few caviots...

A weak or poorly maintained mechanical system, as you describe is hardly a good schematic for design, of course any system, regardless of what it is, when the operator knows it is weak and faulty and uses it anyway, puts that operator at risk...

Now, a system should be designed to minimise that risk, regardless of the operator, so the system should require a self check before allowing motion, and at regular intervals as well, and some of what you described will be minimised...

Next, the battery on an internal combustion engine car is not a primary system, in that you can remove the battery, push jump the car, and it will work fine, presuming all the other systems are working. If the battery is weak, because the alternator is weak and it is running the engine from the battery instead of it's own electrical power generation, as it is designed to do, then your problem is still one system that is bad, causing another to weaken, and again, self check before operation is allowed would minimise the exposure.

NOw, I have run a car long distances with weak charging, where I was aware enough to always charge the car before leaving, as a back-up... But that was decades ago, in a muscle car from the '60s. Most of us do dumb things as kids, and as we get older, we are supposed to do less of them... (I say, 'supposed to' because you may recall some of my skydiving stories, etc...LOL)

A major point to consider would be that of the electrical brakes on an electrical vehicle. The electrical brakes you described are binders. Currently, most binding brakes have a piston of some sort that applies pressure to the moving (Spinning with the wheel) part with a non-moving pad. THis is in drum brakes, disk brakes, transmission brakes (Just the drum is on the drive shaft instead of the wheel) and on the caliper style brakes on some bikes. By including an electric movement piston on this type of a brake, you simplify the electrical requirement but also add an easy place to fail.

Binding brakes require movement without drive, or coasting. Segways cannot coast. Because of this, the example you offer is not directly applicable to segways, but it is to cars, which do coast.

In order for cars to be available for a direct comparison, cars do not need to have electric brakes added, they need to have the ability to coast removed.

Now, I can imagine that it is not too hard, although I have never tried, to step on an upright segway, that is not turned on, head it down a hill, and balance yourself on it. I know people who can ride skate boards, and even unicycles, and imagine it is possible. In that case, more redundant braking systems may be in order.

One last point. If you really wanted to design an all electric braking system for a car, that is not too differently geared to what is on the road now, I would simply build the regeneration of the power directly into the brake system, similar to a magnito system... A magnetic system that generates power based solely on the rotation of the wheel is possible, and it would generate enough power to appy to that brake, and each would have enough storage to do just that. Excess power generation from each collector could be sent to a communal storage battery, but if each brake on each wheel had some storage capacity for one stop, then your problem would go away, in that each brake can be self powered, and not depend on the power system from the vehicle.

[GadgetmanKen]

A weak or poorly maintained mechanical system, as you describe is hardly a good schematic for design, of course any system, regardless of what it is, when the operator knows it is weak and faulty and uses it anyway, puts that operator at risk...


Most the time I knew it was going bad or was faulty, but the funds to fix it just wasn't there. It was a deal with as you go type of thing. Ya know?

Another example is a 93 Buick Centry my wife had that we bought at two years of age. At about the eighth year it kept dying, stalling whenever it hit a hard bump, but not always. It was intermittent. We took it to two different dealerships and couldn't get it to stall anytime when hitting bumps. We all thought my wife was nuts. We couldn't get it to do it on demand. They couldn't figure it out. We finally took it to a good local garage mechanic and he found out what it was. It had a short in the wiring harness inside the steering column where the brights, wiper and speed control, ignition were. Changed the harness with a new one and it stopped. They eventually had a recall on that part.

As for the bad connection on the battery. Sure you can take off the positive post off while the car is running and the generator, alternator takes over, but take the ground loose and the car will die.

But a good ole self check diagnostics wouldn't hurt, either..

[citivolus]

I don't think all-electric regenerative brakes are adequate for stopping a highway speed vehicle. Resorting to a little quick math, as I am wont to do, consider a very light 1100 lb vehicle going 67 mph. Converting to metric, because I picked numbers that look nice that way, gives 500 kg and 30 m/s. In order to stop this requires either storing or dissipating 225,000 Joules. If we assume a normal stop to be 0.5 g and a panic stop to be 1.0 g, this gives us stopping times of 6.12 seconds and 3.06 seconds respectively. Since a Watt is a Joule / second, we find through simple division that the normal stop has go get rid of 36,765 Watts and naturally the panic stop is going to be double that. While you might get 50-100 HP out of batteries, putting it back in is somewhat harder.

The Segway is rather different. Assuming the total weight of a fully loaded Seg is about 150 kg (~330 lb) at it's top speed of 5.6 m/s (~12.5 mph) has 4704 Joules to eliminate. Again, using the same 0.5 and 1.0 g standards just for comparison, stop times are 1.14 and 0.57 seconds meaning the power is a much more manageable 4116 and 8232 Watts. That still isn't to say that you can jam that much power in a battery just that it is much more manageable. Now, I don't know the real numbers but I'm sure the actual stopping time of a Segway has been discussed here before and anyone really interested can perform the experiment themself.

[KSagal]

Here's one for the Venice beach crowd...

You could use the numbers for a highway capable vehicle, and use all that extra wattage that needs to be instantly dissapated by stunning everyone within line of site distance with a large stunning field, just in case they were thinking of making a disparaging remark about your electric vehicle...

[quade]

I don't think all-electric regenerative brakes are adequate for stopping a highway speed vehicle. Resorting to a little quick math, as I am wont to do, consider a very light 1100 lb vehicle going 67 mph. Converting to metric, because I picked numbers that look nice that way, gives 500 kg and 30 m/s. In order to stop this requires either storing or dissipating 225,000 Joules. If we assume a normal stop to be 0.5 g and a panic stop to be 1.0 g, this gives us stopping times of 6.12 seconds and 3.06 seconds respectively. Since a Watt is a Joule / second, we find through simple division that the normal stop has go get rid of 36,765 Watts and naturally the panic stop is going to be double that. While you might get 50-100 HP out of batteries, putting it back in is somewhat harder.

The Segway is rather different. Assuming the total weight of a fully loaded Seg is about 150 kg (~330 lb) at it's top speed of 5.6 m/s (~12.5 mph) has 4704 Joules to eliminate. Again, using the same 0.5 and 1.0 g standards just for comparison, stop times are 1.14 and 0.57 seconds meaning the power is a much more manageable 4116 and 8232 Watts. That still isn't to say that you can jam that much power in a battery just that it is much more manageable. Now, I don't know the real numbers but I'm sure the actual stopping time of a Segway has been discussed here before and anyone really interested can perform the experiment themself.

Who says that all that energy has to go back into the batteries during a panic stop?

Why couldn't it be shunted off to a big chunk-'o-wire and a heat sink?

[hellphish]

Who says that all that energy has to go back into the batteries during a panic stop?

Why couldn't it be shunted off to a big chunk-'o-wire and a heat sink?


Where inside the sealed platform would you suggest they put it?

[bystander]

Where inside the sealed platform would you suggest they put it?Quade was responding to citivolus. And citivolus was talking about both EVs and PTs. So maybe Quade talking about electric vehicles in general.

On a PT, there may be a way (http://forums.segwaychat.com/showthread.php?t=16233) to add braking circuits externally. I know it's a bit of a reach. I still haven't done anything about it but think. I was thinking that there may be a way to make the augmented braking system with a few less brains by having the variable load proportional to it's own revolution rate, instead of trying to sense the current going to the PTs battery packs.

By adding this ("HBS"-type) accessory brake, it allows for additional EMF braking without putting further strain on the motors. After all, one of the limiting factors in regenerative braking is the peak power limit of the motor's windings.

[quade]

I was absolutely referring to the EV portion of the quote since the PT part of it doesn't really require any more of an energy sink than it already has.

citivolus had been talking about an energy sink for use during panic stops.

[hellphish]

Yeah, sorry about that. :) Now I see.

[citivolus]

Who says that all that energy has to go back into the batteries during a panic stop?

Why couldn't it be shunted off to a big chunk-'o-wire and a heat sink?
Oh, I didn't mean to imply the extra energy couldn't simply be dumped into some sort of power resistor only to wind up as heat. But if it's just going to wind up as heat, why not take the easy way and do it mechanically and not worry about heating the electronics and motors thereby reducing the efficiency?

That said, Karl's idea of charging the body shell does sound like it could have some rather "hair raising" applications. :p

[Five-Flags]

... That said, Karl's idea of charging the body shell does sound like it could have some rather "hair raising" applications. :p

And we're back to Tesla again. Amazing how that name keeps coming up...;)