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Electric Motors and Controllers
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Arlo1
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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Arlo1 » Mon Jan 23, 2012 2:10 pm

6.99k erpm max??? Thats only 699rpm for colossus....
My Leaf motor controller build. https://endless-sphere.com/forums/viewto ... 27#p963227
My YSR build http://www.youtube.com/watch?v=BRo8r5g4NBg
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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Lebowski » Mon Jan 23, 2012 2:29 pm

Arlo1 wrote:6.99k erpm max??? Thats only 699rpm for colossus....
These numbers are for my own motor, you can type whatever you want here. This
particular entry I think goes up to 255.99k and is not limited by the controller algorithm
but by the computation which takes the number you enter and transforms it into the
16 bits integer the algorithm uses. Is there a need to go higher than 256 k-erpm ?

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Farfle » Mon Jan 23, 2012 2:37 pm

The joby motors are some insane E-rpm iirc, but I cant find it.
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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Arlo1 » Mon Jan 23, 2012 2:43 pm

Lebowski wrote:
Arlo1 wrote:6.99k erpm max??? Thats only 699rpm for colossus....
These numbers are for my own motor, you can type whatever you want here. This
particular entry I think goes up to 255.99k and is not limited by the controller algorithm
but by the computation which takes the number you enter and transforms it into the
16 bits integer the algorithm uses. Is there a need to go higher than 256 k-erpm ?
I doubt it but colossus will need <100KERPM so we are good!
My Leaf motor controller build. https://endless-sphere.com/forums/viewto ... 27#p963227
My YSR build http://www.youtube.com/watch?v=BRo8r5g4NBg
RC and most types of Lithium batteries you MUST know your individual cell voltages charging and discharging.
Don't keep them were you cant afford smoke or fire!
Never above 4.2v never below 2.7v EVER!!!
HI power controller design. Game Changer

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by mauimart » Mon Jan 23, 2012 3:03 pm

Farfle wrote:The joby motors are some insane E-rpm iirc, but I cant find it.
From the Joby thread it appears we are looking at 26 pole pairs. That's 9800 mechanical rpm with the 255k-erpm. Seems like that will do...

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by c_a » Mon Jan 23, 2012 5:17 pm

I need only 5,000mrpm @ 15 polepairs = 75,000erpm or 1,250Hz field frequency :D

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Lebowski » Thu Jan 26, 2012 4:36 am

I'm busy now adding reverse for if someone wants to build a multi-motor car type vehicle. :D
Is kind of nasty as this also has to work over CAN bus and has to check motor speed
as we don't want to change direction on a fast spinning motor. I think I'll make it such
that when a controller receives a 'change direction' request it cuts the power and
only accepts regen until motor speed is low enough to change direction.

When you got all kinds of features adding an extra one isn't simple anymore :D

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Miles » Thu Jan 26, 2012 5:11 am

:D For my needs, the quicker the changeover, the better.....

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by whatever » Thu Jan 26, 2012 7:25 am

seems controllers with reverse also limit the max speed in reverse...more complexity

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Lebowski » Thu Jan 26, 2012 7:30 am

whatever wrote:seems controllers with reverse also limit the max speed in reverse...more complexity
Now that I think about it, good point, could be a safety hazard if it's not limited to a lower e-rpm than
forward. It's only 2 additional instructions anyway...

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Alan B » Thu Jan 26, 2012 9:26 am

Some transmissions shift gears by reversing the motor. Want it to be reasonably fast and may have the same RPM limit both ways.

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Teh Stork » Thu Jan 26, 2012 10:49 am

Long time lurker, first time poster in this thread - great work: gl further on :)
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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Lebowski » Thu Jan 26, 2012 11:14 am

about this fast reversal of direction, how would you imagine this ?

They way I see it, you cannot instantly change polarity of the voltages as it would
instantly dissipate all the motors rotational momentum in the windings
and (blow out all) FETs. You have to bring it to a controlled stop using
either the brakes of the vehicle (like in a car) or use regen to shuttle the energy
back into the battery. Then you reverse polarity and spin up the motor again in reverse.
This is how I have it in mind, I don't see how else it can be done ?

What I can do maybe is that when the direction switch is thrown the controller
automatically jumps to a preset regen level to shed the energy of the motor
before reversing it. As a user you would be able to stay on the throttle while
this automatic process happens....

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Miles » Thu Jan 26, 2012 11:25 am

In the case of using reverse to change gear, most parts of the transmission are freewheeling until the load is retaken in the opposite direction. The bulk of the inertia to overcome is in the rotor of the motor.
Lebowski wrote: What I can do maybe is that when the direction switch is thrown the controller
automatically jumps to a preset regen level to shed the energy of the motor
before reversing it. As a user you would be able to stay on the throttle while
this automatic process happens....
This sounds perfect.

Is a pause needed before reversal?

If the throttle is going to be held, it might be good to have a temporary torque limit after reversing, until the load is retaken.. :)

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Arlo1 » Thu Jan 26, 2012 12:15 pm

Jeremy harris listed a video of a bldc motor reversing at hi speed ! If nobody else finds it i will look tonight when i get back to my computer.
My Leaf motor controller build. https://endless-sphere.com/forums/viewto ... 27#p963227
My YSR build http://www.youtube.com/watch?v=BRo8r5g4NBg
RC and most types of Lithium batteries you MUST know your individual cell voltages charging and discharging.
Don't keep them were you cant afford smoke or fire!
Never above 4.2v never below 2.7v EVER!!!
HI power controller design. Game Changer

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Lebowski » Thu Jan 26, 2012 1:24 pm

Miles wrote:In the case of using reverse to change gear, most parts of the transmission are freewheeling until the load is retaken in the opposite direction. The bulk of the inertia to overcome is in the rotor of the motor.
Is a pause needed before reversal?

If the throttle is going to be held, it might be good to have a temporary torque limit after reversing, until the load is retaken.. :)
Well my motor got a 2 kg rotor, stopping it dead is violent :D
What pause do you mean ?

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Miles » Thu Jan 26, 2012 1:31 pm

Some sensorless controllers seem to need a pause of at least 100 milliseconds at zero rpm, before restarting in reverse.

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Alan B » Thu Jan 26, 2012 2:02 pm

Motor controllers often have a reversal input. A good controller will reverse at high power.

I would think to reverse quickly you would set PWM to zero, reverse the phasing of the commutation, and ramp the PWM back up. Clearly during this ramping the power is going to buck the motor EMF, but just like other situations the PWM is used to control the current to a safe level. Applying bucking power is the fastest way to reverse the motor while keeping voltages and currents at a safe level.

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Lebowski » Thu Jan 26, 2012 3:23 pm

Alan B wrote:Motor controllers often have a reversal input. A good controller will reverse at high power.

I would think to reverse quickly you would set PWM to zero, reverse the phasing of the commutation, and ramp the PWM back up. Clearly during this ramping the power is going to buck the motor EMF, but just like other situations the PWM is used to control the current to a safe level. Applying bucking power is the fastest way to reverse the motor while keeping voltages and currents at a safe level.
Ramping the PWM back up in your description comes down to the regen in my description,
it will not be a faster process. Both mean a negative current out of the motor, in your case via a negative
voltage and small PWM, in my case via a reduced positive voltage and a higher level of PWM. In
both cases the same amount of energy per second can be extracted from the rotor, giving equal
rates of deceleration.

As I see it, there is no real difference between your and my description.....?

An interesting puzzle for you guys to figure out how it works,
to reverse the direction of the motor a single assembly instruction
which XOR's the 16 bit phase variable with 7FFF hex is enough...
Last edited by Lebowski on Thu Jan 26, 2012 3:30 pm, edited 1 time in total.

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Lebowski » Thu Jan 26, 2012 3:24 pm

Miles wrote:Some sensorless controllers seem to need a pause of at least 100 milliseconds at zero rpm, before restarting in reverse.
no, there's no need for a pause like this. But, would you notice a pause like this ?

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Miles » Thu Jan 26, 2012 3:36 pm

I'm hoping for a total turnaround time of about 0.5 second (obviously not with a rotor the size of yours..) - so that would be 20%.... :)

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Alan B » Thu Jan 26, 2012 4:53 pm

When I looked into it I found that there was a not so subtle difference between regen braking and power reversing the motor. Regen is weak compared to power reverse.

Let's say we are putting 1KW into the motor. If we go into regen we take out somewhat less than 1KW which quickly diminishes as the motor slows. So the regen power over the deceleration period averages less than 0.5KW. If we instead do power reverse we stay at 1KW the whole time we are reversing, so in less time that regen has merely stopped the motor a power reverse has accelerated through stop and continued fully to reverse.

Normally the motor's back EMF is bucking the battery voltage and reducing motor current, when power reversing they are series aiding. So the current will be really high if not properly managed.

In regen the motor back EMF is boost converted up in voltage to flow current backwards into the battery, in power reverse battery power is applied to slow and reverse the motor. Perhaps a way to look at that is the regen/deceleration and the reverse acceleration are overlapped and going on at the same time.

At least that's my present understanding.

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Arlo1 » Fri Jan 27, 2012 12:15 am

I cant find the video jeremy harris posted but here is a ebike wheel reversing at full power.
My Leaf motor controller build. https://endless-sphere.com/forums/viewto ... 27#p963227
My YSR build http://www.youtube.com/watch?v=BRo8r5g4NBg
RC and most types of Lithium batteries you MUST know your individual cell voltages charging and discharging.
Don't keep them were you cant afford smoke or fire!
Never above 4.2v never below 2.7v EVER!!!
HI power controller design. Game Changer

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Lebowski » Fri Jan 27, 2012 1:46 am

In the end how fast it will be able to reverse depends on the setup, all variables influencing this process
are accessible to the user. You can set the regen current during slow down and the rpm below which
the reversal is made. You can try to make the reversal as fast as possible with these but it won't allow you to
violate certain current limits like phase wire current and battery regen current (though you can also change
these as well but you have to be sure your FETs/battery can take it).

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Re: #$%@$#@ <--- (insert favorite swearword here), IT WORKS

Post by Gordo » Fri Jan 27, 2012 1:56 am

Lebowski wrote:In the end how fast it will be able to reverse depends on the setup, all variables influencing this process
are accessible to the user. You can set the regen current during slow down and the rpm below which
the reversal is made. You can try to make the reversal as fast as possible with these but it won't allow you to
violate certain current limits like phase wire current and battery regen current (though you can also change
these as well but you have to be sure your FETs/battery can take it).
Isn't this getting a little goofy? How many people want to use this function? Maybe you could make it hover and levitate while spinning on it's axis?
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