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

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
 
seems controllers with reverse also limit the max speed in reverse...more complexity
 
whatever said:
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...
 
Long time lurker, first time poster in this thread - great work: gl further on :)
 
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....
 
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 said:
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.. :)
 
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.
 
Miles said:
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 ?
 
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.
 
Alan B said:
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...
 
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.
 
I cant find the video jeremy harris posted but here is a ebike wheel reversing at full power.[youtube]Pz5JmRBUsZU[/youtube]
 
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).
 
Lebowski said:
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?
 
Gordo said:
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?

Not really I think, I can imagine that also for use in a 4 wheel hub motor vehicle or a
rear wheel driven trike you want to (have the option to) actively and controllably slow
down the motor(s) when the driver flips the reverse switch.... That there's people out
there that want to abuse this funtion 'cause they got a two speed gearbox which works
on reversing the motor... :D

levitate, no :D but I'm kind of dying to get my hands on a 48V 500W induction motor
to try and to get that running as well, it should be possible with some small changes
but I can't develop this when I don't have a test subject to experiment with. I've been
eyeing my laundry machine but expect this has a 2 phase motor, not a 3 phase.

On the other hand, I think the controlled slow down for motor reverse is the last thing. I'll
finish it up now and run some tests, go over the whole thing one last time, draw a schematic,
write a manual for the setup menu and ship the IC's to the people that PM'ed me and want to try it out.
 
[youtube]lXGxe9H2-aE[/youtube]

This video shows the dissipating of the rotor energy into light bulbs when reversing the motor.
The menu option to actively apply regen to the motor when reversing is selected, so
every time I reverse the rotor energy is recovered with regen and (in this case) dissipated
in the bulbs. The amount of regen Amps can be set for gentle or hard braking, or anything
in between.

The bulbs are accross the supply of the output stage, which in turn is connected
to the power supply via a diode. During motoring the current flows from the power
supply via the diode into the motor and the lamps. On regen the current is reverse but,
because of the diode, can only take the route via the lamps, lighting them up more
brightly. This just to explain why the lamps are on all the time..

The noise is the freewheel of the bicycle hub that is my motor axle. You can see how
because of the need to spin up the freewheel and gear cluster the reversal in one way
takes longer than in the other.

The motor is running sensorless on 2 current sensors in this video. It also uses sensorless start.
 
Lebowski,
I understand you have built an incredible controller in a very short time. I also understand that there are a few people who have some very unique requirements. It is your choice if you want to send something out for field testing which will overjoy 95% of the people or continue to develop your software ad infinitum? We are now ready with a variety of motors to do a lot of work and provide you with feedback, if this is what you wish.
Thanks,
Gordon
 
Gordo said:
Lebowski,
I understand you have built an incredible controller in a very short time. I also understand that there are a few people who have some very unique requirements. It is your choice if you want to send something out for field testing which will overjoy 95% of the people or continue to develop your software ad infinitum? We are now ready with a variety of motors to do a lot of work and provide you with feedback, if this is what you wish.
Thanks,
Gordon

Well I thought it was finished last wednesday but then I saw the post from Hugues about his big bear chopper. I followed
the link in that post to the Kelly controller he wants to use. Reading through its specs I realized the only thing I was missing w.r.t.
the $1200 Kelly was reverse... so I decided to add it as well. And with reverse comes the problem of what to do when
reverse is selected when still moving forward, so I decided to put in an automatic regen option for this.

Adding something like reverse seems simple (the actual reverse is only 1 instruction) but it has to be integrated correctly
so that it also works over CAN bus in a multi-motor setup, a menu items have to be added etc etc.

But it's done now, I'm not adding any more features (for now :D ). I want to sit on it for one or 2 weeks to run tests and to make sure
that everything works as it should. I don't want the "oh #@$%@ I forgot such and such" thought 3 hours after mailing the
chips :D , I prefer not to ship IC's back and forth 3 times.

Before then I'll have the schematic finished so you can start soldering everything together, just use a standard 40 pins DIL
socket where the IC is supposed to go.
 
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