Solar car races

Post and discuss your VESC projects here.
Thor
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Joined: 22 Jan 2017, 11:32
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Re: Solar car races

Postby Thor » 26 Mar 2017, 15:46

Attachments
low speed.png
flawless low speed run in duty cycle mode (D=0.1)
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sync loss.png
arrow keys multiple sync losses
sync loss.png (183.17 KiB) Viewed 3142 times
high speed.png
flawless high speed run (D=1)
high speed.png (178.28 KiB) Viewed 3142 times

lizardmech
Posts: 171
Joined: 19 Jan 2016, 10:54
Location: Australia
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Re: Solar car races

Postby lizardmech » 27 Mar 2017, 03:46

Why are there resistors and capacitors between the ina240 and the shunt, datasheet says not to do that I think. Also why are the drivers going into relatively weak BJTs? Is your board 4 layers throughout? It's easy to fix it if so.

Thor
Posts: 20
Joined: 22 Jan 2017, 11:32
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Re: Solar car races

Postby Thor » 27 Mar 2017, 09:26


pf26
Posts: 310
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Location: FR Valence
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Re: Solar car races

Postby pf26 » 27 Mar 2017, 13:46

With center-aligned 3 phase switching, your scope (and ears) see 10kHz while the windings switch at 20kHz since they are subject to 2 commutations per cycle.

Can you scope your current waveform, to see if there is a current measurement issue in your VESC, or if the current shape is really that funny.

lizardmech
Posts: 171
Joined: 19 Jan 2016, 10:54
Location: Australia
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Re: Solar car races

Postby lizardmech » 27 Mar 2017, 15:48

One thing I forgot, my ina240 board appears to prefer deadtime compensation of 0 rather than the default 0.08 us. I think the trace traveling over split ground planes and being long with various vias is no good. I always make the analogue current sensing circuits the highest priority when laying it out.

rew
Posts: 943
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.
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Re: Solar car races

Postby rew » 27 Mar 2017, 16:20

The current signal is tricky to view on a scope: There is a lot of switching noise on the signal, and the CPU tries to sample close to the optimal place, away from the switching noise. If you insert a current sense resistor in the phase and try to measure that differentially I still think you'll be swamped in switching noise....

Thor
Posts: 20
Joined: 22 Jan 2017, 11:32
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Re: Solar car races

Postby Thor » 30 Mar 2017, 23:48

Well, I got some realy good news to report. I started setting up the lab for benchmarking the controller yesterday and got my first results today.

Staring small with 12V in the intermediate circuit und 1A motor current limit delivered these results:

Note: The motor is controlled completely sensorless as the included sensors are incompatible to the standard VESC. Therefore the little nudge to get it running. The only load in the video is the freewheeling load simulator and inherent inertia. The spin up is very smooth.

Some testing later I can say that the controller runs this motor quit well up to 60V and 10A. The power stage gets unexpectedly warm for that load but this is most probably related to my overreaction relaxing the switch and dead times. I also hit a wall in the gui as I was not allowed to rise the max battery voltage above 60V. Hopefully the gui is the only thing that prevents higher voltages from being used. We will see after I patched the gui.

I also took another look at the current waveforms and was pleased to see nicely sin shaped currents. I guess the small low inductance inrunner I started with was not the best choice... :roll:

At the end there is still a fly in the ointment. I got a hard time to measure the lambda at higher input voltages. BLDC mode in neither integral nor delay mode seems to be working. This is most likely related as the FOC uses a delay mode run to determine lambda. Is there something I miss? Any tips?

Thor
Attachments
Benchmark.png
Benchmark.png (177.58 KiB) Viewed 3085 times

rew
Posts: 943
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.
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Re: Solar car races

Postby rew » 01 Apr 2017, 12:45

If you increase decimation to "2" in that plot, I'll tell you howmany poles your motor has.

edwardcolins
Posts: 1
Joined: 15 May 2017, 17:58
Location: Los Angeles
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Re: Solar car races

Postby edwardcolins » 15 May 2017, 18:13


Thor
Posts: 20
Joined: 22 Jan 2017, 11:32
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Re: Solar car races

Postby Thor » 15 May 2017, 19:07

At the moment both are 0 but you can try for yourself.

Let's write a little update if I am already at it:
I got the motor running pretty reliable now. A few issues are still unsolved. First up the voltage dividers are a bit finicky. I am running higher input voltages which requires a higher division factor. Unfortunately the BEMF sensing does not work properly with higher division factors. This is also the cause of the lambda sensing and BLDC mode running so poorly. I worked around this by using the old factors on the phase sensing and higher factors for the busvoltage sensing. The code for the duty cycle estimation while freewheeling needed a patch to cope with the unequal factors but this seems to work quit well. It seems like the resolution is just to low when selecting higher factors for phase sensing but maybe I just overlooked something in the code.

My best runs so far where 30A motor current at 120V bus. Temperature went up to 60°C. Most of the powerloss comes from the poor little IRFP260. I had a little - uhm - accident. ;) One half bridge of IXYS fets had a plasma eruption and needed replacment. The only replacments I had at hand where these IRs. I am pretty sure 60A phase current are possible with better fets. Next problem will be getting a bigger power supply. :)

A endurance run at 120V 5A for those who are interessted in spinning motors^^
https://www.youtube.com/watch?v=04ekDW2AEq0

Thor


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