Magnetic Breaking

[RatoN]

Could a modification of the controller timing, produce magnetic breaking effect using the motor power, on an Xlyte?

If yes

Could this ''effect'' be scalable on the fly, to create controlable magnetic breaking intensity?

[knightmb]

Do you mean using the battery power to produce a brake effect or using the power generated from the motor in reverse to do a "regen" braking effect?

[RatoN]

Hello Knight

Batteries.

The controller pulsate current at certain moments to make the wheel spin, depending on how fast the wheel spins. So there is a sensor(s) in the hub, right?

The throttle controls the power, but the controller decides when to pulsate it, right?

Now imagine high current, off timed, without reversing the current!

In other words, a current timing controller.

[xyster]

Hmmm...interesting.

A relay on the motor leads to reverse the motor voltage should work, but the effect might be quite abrupt! Perhaps with some sort of capacitor damping circuit hooked to a pot at the brake levers it could work.

[RatoN]

Reversing the power is totaly out of the question. I asked Justin about that many moons ago and he said that this is not good for the motor.

BUT

Imagine for a moment pluging the 72v directly to the motor. No contoller. Not only the wheel would not spin but that would create a huge resistance, all the ''elements'' being ''ON'' all around the wheel at the same time.

[RatoN]

double trouble

What IF, all that is needed is an on/off switch on the handle bars to the sensors wire, canceling the order to pulsate?

Would it be constant OFF or constant ON??

[xyster]

Reversing the power is totaly out of the question. I asked Justin about that many moons ago and he said that this is not good for the motor.

Reversing is fine I believe (the "reverse" key switch on the controller effectively does the same anyway)...it's full-on abrupt reversal that'd cause problems.

Would it be constant OFF or constant ON??

Constant OFF I think. In which case the motor would just coast as it does without any power.

[RatoN]

So, then solution resides in the controller. There is no bypassing it, because the controler also decides the + or - of the elements alternatively.

Must find a way to stop the pulsating, so that half of the elements stay positive and the other half stay negative and the intensity will be controlled by the throttle.

[fechter]

To get braking, you need to switch all the low side FETs on at the same time. This momentarily shorts the windings in the motor. When the switches open, the voltage kickback will circulate back to the batteries and charge them.
Then you use a PWM to control the amount of braking.

In order to do this, there would need to be a PWM for the braking and a way to re-route the gate drivers. This would be all low power logic stuff, so the parts wouldn't be too expensive.

Another possible way to do it would be to build a separate braking controller that has 3 banks of FETs and a PWM. You would tie into the 3 motor phase wires. You would also need some kind of interlock to prevent braking and acceleration at the same time. This way you wouldn't need to modify the controller, but you would need big $ FETs.

To control the braking, you would need some kind of control to activate it. A throttle that goes both directions from neutral would be cool. Sort of like an RC transmitter stick.

On my Zappy, I had a separate current limiter for the braking set it at a fixed level. This worked great. But that controller was already made for braking.

Another way, that might be easier, is to use a brake switch in the lever to activate the braking. That's pretty much how it's done on my Honda hybrid. When you hit the brakes, the regen kicks in. The amount of braking could ramp up so you don't get a sudden wheel lock.

It might be a good idea to have a circuit to disable the braking if the battery voltage gets too high. This was a problem on my Zappy if I started out on the top of a big hill with a full charge.

The really crude way to do it would be to use relays to switch some really big resistors across the phase wires. No regen, but serious braking.
The problem with this is the braking force will increase with speed. Not so good when you're going full speed down a big hill. I tried this on my Zappy a long time ago. I caught the resistor on fire one time.

[xyster]

God complex already?
That avatar's pretty scary!

I think this one is much nicer :-) :

[fechter]

Lock and Load, Baby!

[v_tach]

How do the little ESCs in electric hobby R/C vehicles accomplishing braking? I know my old stadium race trucks from a few years ago had the feature. Push the throttle trigger forward once and it activates the brakes, a quick double-push of the throttle trigger activated reverse throttle. Pulling the trigger on the transmitter controller was forward throttle.

[fechter]

SILENCE MORTALS!

You want to see something really scary, how about this one:

[fechter]

If that's too scary for Xyster, I could use this one instead:


On RC controllers, the brakes work by shorting out the motor. This is a bit rough on larger vehicles. Basically you need to short out the motor, but at a high frequency and with a limited duty cycle where it doesn't stay shorted for very long.

[Mathurin]

Scary is the thought of a grasshopper attempting to challenge your kung-fu.

Mr T. pities the fool... (Does not have time for jibba-jabba)




But serious, when the fet shorted in my controller, it madea pretty effective brake. I'd think this is a viable alternative to other forms of braking.

Interestingly at Velectris, the brakeing on their controller dishes out around 500w of regen at 30 km/h, but one can brake much harder then that except it regens less? And apparently the heat then dissipates within the motor.

[xyster]

You want to see something really scary, how about this one

Fairly scary, yes indeed-e. You should post your WTF emblem over on the new V :-) See how long it stays before being replaced with two pages of legalese.

Yet that emblem is not half as frightening as your avatar, which frankly looks like a half-man, half-elk hybrid in heat.


I'm still partial to the "Fechmaster" caricature posted on the previous page, but she needs some serious facial reconstructive surgery. And her skin is kind of blotchy :-)

[TylerDurden]

I don't have any schematics, but I believe some electric power tools like circular saws use electric brakes.

My battery powered Black and Decker lawnmower definately does: If I only partially release the handle, the blade will coast, if I release entirely, the blade stops instantly.

[fechter]

Putting a short across the motor definitely puts on the brakes. One time my Zappy blew a FET and it siezed the rear wheel. Threw me right off. The controller's original regen feature was so strong it would cause the belt to skip, so I had to put a current limiter on it to reduce the force enough to prevent skipping.

[RatoN]

Ah you see Fechter, faith has chosen you to design a new kind of controller.

* Scalable 36v, 48v, 72v, 96v modes.

* Magnetic braking capability. ON/OFF

* Many battery packs 12v and 24v extra inputs for accessories for lights and stuff. Seperate lines from the main batt packs.

* Many outs plug-in for accessories 3v, 6v, 12v, 24v.


What else...??

[fechter]

What else?........

How about sensorless! no more hall wires.

How about having a low battery cutout, motor overtemp and controller overtemp that work by gradually backing off the throttle rather than suddenly dying right as you pull out in front of that Hummer.

Built-in BMS?
I see you got built-in DC-DC converter.

User adjustable limits for current, low voltage, ramp-up rate
Current mode or speed mode throttle. Speed mode works like cruise control.

A cool display that works like a Drain Brain and allows programming in the field.

Now if it could only be affordable too, that's the kicker.