Paul and Sabrina's Cheap 3 Phase Inverter (AC Controller) with Field Oriented Control

[e*clipse]

I know motor temp can be really slow, even in human terms. I'd also make it a pretty rough (like 8bit number) Is that temp1 or temp2?
Throttle could also be pretty slow, but I'd probably sample every 1/10 second just to make it "feel" smooth, along with a finer resolution number. It may not even be possible to sample that infrequently...

It's kind of like Edward said - it's not a CNC machine or robot. Considering all the mass (not just the motor - the car) and lag times involved it can be pretty rough - and still WAY smoother than an IC car.

Originally Posted by MPaulHolmes

That sounds good. We will need to figure out the best arrangement for the A/D conversions. Current1, current2, sin (), cos (), throttle, temp1, temp2. we could always do currents and angles simultaneously, and maybe every 32 times we do current1, throttle, temp1, temp2.

[Astro]

Paul,
Thank you for all the progress updates. It is all very exciting.
The DC and AC controller threads are long and my memory is short so i was curious as to where you are at with your vehicles. Do you still have the beetle? Are you going to be putting one of these AC controllers in a vehicle of your own or is it all just for us?

[MPaulHolmes]

I don't have an ev anymore. I sold it before moving to I really want to do another one though. We have had some unexpected expenses though.

I've been doing a lot of deburging (holy cow the most recent software update on my cell phone insists on filling in the wrong words by default. I need a blender for this phone. Any time I depart from every day conversation words, it's a disaster). I'll just t y Pw and quit trying to fix it.

Ok, fixed an integer overflow problem in 2 places. The motor was spinning at 15 50 rim (there it goes again) at 72 volts dc. It is rated for 1400rpm (this piece of crap made me type 1400amp) at 680vdc. I think the back emf is a problem for smooth control when you refuse to weaken the field. Now I'm trying to figure how to smoothly know when field weakening is required. This may not be a major concern at higher voltage when the motor is heavily loaded and y Po u aren't near the peak rpm.

[Cyruscosmo]

Originally Posted by Astro

I have to deal with someone like that regularly. What i do is state my case, give all the reasons to do it my way then drop the subject totally. About a week later they come back and want to start the debate again yet now they are arguing to do it the way i originally suggested and claim i wanted to do it the opposite way. When i first had dealing with this person i started questioning my own memory until some independent observers confirmed that the person had reversed their position.
So now it is a running joke for everyone who watches it happen. I just state my case and wait for them to adopt it as their own.
This gets the job done but does mean the person has the impression that i am always wrong and that they are always right.
Maybe i should become a cat herder instead.

I "Had" the same problem with a guy I work with. I started carrying one of those small recording devices and when ever I had "those" discussions with him I just recorded them. After the third time I referred to what he "actually said" verses what he "thought" he said, he oddly stopped arguing with me and started listening...

[freebeard]

Washington's wiretapping law is a "two-party consent" law. Washington makes it a crime to intercept or record a private telephone call, in-person conversation, or electronic communication unless all parties to the communication consent. See Wash. Rev. Code § 9.73.030(1). Whether a conversation or other communications is "private" depends on a number of case-specific factors, such as the subjective intention of the parties, the reasonableness of their expectation that the conversation would be private, the location of the conversation, and whether third parties were present. State v. Townsend, 57 P.3d 255, 259 (Wash. 2002). You should always get the consent of all parties before recording any conversation that common sense tells you is private.

http://www.dmlp.org/legal-guide/washington/washington-recording-law

[MPaulHolmes]

thats hilarious cyruscosmo. I got the motor up to around 640 rev/sec×16 (the weird units I'm using). the motor is rated for 1400rpm at 480vac or 400vac. I forgot. this was at 72v dc.

[Astro]

Originally Posted by MPaulHolmes

... I got the motor up to around 640 rev/sec×16 (the weird units I'm using). the motor is rated for 1400rpm at 480vac or 400vac. I forgot. this was at 72v dc.

So is that 640 revolutions per 16 seconds?

[MPaulHolmes]

yes. you sure can write it that way. i hadn't thought about it. i had always just thought of it as multiplying the rps by 16 for more resolution. so, about 2400 RPM.

high rpm and field weakening have been a challenge, with some surprises. The PI loops were tuned very fast, which means huge voltage swings to get the current to match the desired current. The problem is, at 72vdc on that motor, at around 390 Rev/ (16sec), if you are commanding the torque and field components to be some fixed value, you run out of voltage. If you still insist on holding them constant, the PI loop blasts the Vd and Vq voltages to kingdom come. They of course have to be clamped, and transformed back to the 3 phase voltages, and theres the problem. unfortunately you can't clamp Vd and Vq separately. you have to clamp the distance of 《Vd,Vq》to the origin. So, when Vd goes stupidly big (like a jump from 800 to 6000), Vq wants to be left alone, holding the torque component constant at, say, 800. but now we have to clamp the distance 《6000, 800》to a radius of 1729 (that happens to be the radius). that means the new value of 《Vd,Vq》 is something like 《1700,220》. well, through no fault of his own, the torque component was cut way down. But the torque component PI loop is still trying to force Iq back to what was commanded (say, 800). So, you get angry fighting between the torque and field, trying to hog all available voltage so their respective current can be the commanded value. so the field is all over the place, and so is the torque component. this does not make for a very smoothly sounding motor when that happens!

So, I was trying various things so hitting the rpm ceiling doesn't cause a problem. Now this is like 50VAC on a 480VAC motor, so of course it would have an issue of running out of voltage. But it would be nice to deal with the high rpm case all the same. Here is what I have tried:
reduce Id linearly from rpm1 to rpm2. That works OK, but needs to depend on Iq too.
Each time a clamp is about to happen, reduce the clamped variable's current commanded value. That works really well, but it needs to be fine tuned.

[Astro]

Owie, owie, owie, i have sunscreen on my brain... at least that is what it feels like.

So does the clamped variables commanded current need to be reduced buy a larger percentage as the RPM increases?

[MPaulHolmes]

Yes! Well, what I have been doing is, when there is a gross violation of the clamping (VdClamped - Vd) > 100, knock down the commanded Id by 100. As if giving it another chance, allow the "commanded" current crawl back very slowly to the ACTUAL commanded current. If there's another violation of Vd or Vq, tar whoop them again!

The process needs to be cleaned up, but that has worked best. Another way is, I think I need to find the relationship between Id, Iq and RPM and load for all possible values (for a given AC voltage). Because that wouls be difficult, I'm trying to be content with only using Vd, Vq, Id, and Iq, since I have those.