Motor braking.

[GriffinRU]

Motor takes the abuse.

Power goes to batteries if voltage higher then... and you can skip diode drop if utilize FET's instead. And as I said it is possible, but I haven't seen one yet from known brands, except claims by Novak on brushed ESC and mtroniks for all.

If you see direct connection between batteries,caps and FET's then such circuitry doesn't exist.

[BrianG]

So, I am correct that the FETs simply apply a controlled short to the motor? If that is the case, how can the voltage develop across a short (aside from FET rdson) to get any higher? I'm not disagreeing or arguing, just trying to understand how the braking works. The rest seems relatively easy from a macro standpoint...

[GriffinRU]

Originally Posted by BrianG

So, I am correct that the FETs simply apply a controlled short to the motor? If that is the case, how can the voltage develop across a short (aside from FET rdson) to get any higher? I'm not disagreeing or arguing, just trying to understand how the braking works. The rest seems relatively easy from a macro standpoint...

If controller doesn't open FET's then BackEMF from motor will be rectified by built-in diodes and will be charging battery, if battery voltage will be less then backEMF+voltage drop. You can optimize this process if you open FETs in sync with diodes, then you will cut off diodes voltage drop and losses.
If you noticed braking can be done with only one side, while recuperating involved both.

[silentbob343]

Quick question;

Would the ABS type of braking be more or less stressful than std. proportional braking?

[GriffinRU]

Originally Posted by silentbob343

Quick question;

Would the ABS type of braking be more or less stressful than std. proportional braking?

I don't think so, should be no difference as long as ESC can handle it.

[Serum]

No, i don't think so; an ABS is just a way of braking, with the intention not to lock the tires. A gentle finger on the brakes does the same.

[silentbob343]

Originally Posted by Serum

No, i don't think so; an ABS is just a way of braking, with the intention not to lock the tires. A gentle finger on the brakes does the same.

Yeah I was just wondering if an on-off pulse from ABS would be better.

[Procharged5.0]

Someone with an Eagletree and ABS will have to run tests for us on this!

[zeropointbug]

All motor braking is switching, it does switch on/off to create braking and not just short the motor and flip the car. I probably uses simple PWM with all three phases in switch at same time.

Procharged: We discussed that braking is a loop circuit with batteries NOT included. what are you going to pick with Eagletree?

[Serum]

I guess you missed quite a bit then zero..

batteries ARE included...

for the tenth time; where would you stuff your energy needed for braking? in the esc?

[zeropointbug]

what the.... the MOTOR takes the abuse, batteries are not involved with braking. Did you miss everything that was said? :032:

Serum, grab a brushless motor and give the shaft a spin. Now connect all three motor leads together and spin it again. Notice how much stiffer it is?

Now in that scenario tell us in what battery or ESC the energy is "being stuffed"?

[GriffinRU]

Most of it will be absorbed by motor, some by batteries...

It would be really hard to measure with eagletree what's going on with braking with normal approach, but if you add current sensor on one of the motor leads then you can measure what we are looking for. But to make it clear what has more or less harm ABS or proportional braking would be still difficult. And even with the last one it would be impossible with eagletree's resolution to see anything useful...

[BrianG]

Aragon, do you think this stiffness is enough to stop a vehicle as fast as it does? I figured the ESC would basically energize all phases at once effectively locking the rotor. Of course, this can be controlled via PWM.

If it's just the motor braking by shorting (more or less) the phases, then the motor is taking the majority of the abuse except whatever voltage is dropped across the FETs. This is the only way I can see any energy being fed back to the batteries, but the induced voltage has to be higher than the battery voltage for them to be charged. Maybe this is what Griffin explained above, but I seem to be too dense to understand it.

If the ESC locks the rotor by PWM energizing all phases at once, then the ESC seems like it would be taking the abuse.

[GriffinRU]

ESC only shorts motor phases.