CAN boost and fweak

[Peter]

Hi forum. Thinking of sending different value CAN messages to Olimex to change boost and fweak when in different gears? In 1st gear I can run high boost but not when setting off in 2nd. Already reading CAN so its just a few more lines of code. Any thoughts guys ?
It would be great to have the ability to assign a parameter to a pot, that way you could tweak a parameter value on the fly for testing whilst on the move ? Could this be too much to ask Johannes

[joromy]

This should be possible, have you looked at this:
https://openinverter.org/wiki/CAN_commu ... rs_via_SDO

If you have a arduino or something able to send configurable can messages, it would be possible to change parameter with a pot, switch or other input methods.

I would not have another pot input on the openinverter design, but I'm not Johannes H.

[Peter]

Hi joromy. Yes I do communicate via Arduino. I have not tried 'sending' CAN messages yet only receiving them so its my next playtime job Easy enough to assign a variable to the pot and use map to make the span correct so I will have a go. Watch this space for results

[Isaac96]

Hi Peter,
I was thinking about doing something similar (I have the same issue with boost..)

But what I was planning was sending different 'udc' values -- if you have udcnom set then the inverter scales boost and fweak according to the input voltage. Thus sending a higher-than-actual udc would result in lower boost and higher fweak, and lower-than-actual would be higher boost and lower fweak.
This might be the wrong combination for you but it is likely the easiest. Just be sure not to mess up the values on startup or you risk frying contactors or precharge resistor.

-Isaac

[joromy]

Hi joromy. Yes I do communicate via Arduino. I have not tried 'sending' CAN messages yet only receiving them so its my next playtime job Easy enough to assign a variable to the pot and use map to make the span correct so I will have a go. Watch this space for results

Yes please tell us how it goes, and some code example.
I'm interested in doing some similar, but to lacy

[Peter]

My aim is to have good initial acceleration and then increase fweak to give power higher up the rev range, but this may not work due to my pack voltage being low (220) relative to the motor rating voltage (208). However if it means I will not be stressing or blowing igbt's (please advise here) then I may use motor RPM as the reference and alter fweak accordingly. Any thoughts guys ?

[johu]

fweak by definition uses motor rpm as reference. Increasing fweak will not shift power higher up but will rather decrease available power. I would take it out of the equation for now and just play with boost

[Peter]

Thanks Johannes. How far into the initial rev range does boost play a part ? Also when I floor the throttle at any part of the rev range (0-9000) I get an initial surge (even up around 7500) which dies off quickly, can this be attributed to any parameter(s) please as I would like to be able to extend the power.
I could add another 50v to my pack, would this be the better choice? Thanks in advance. Peter

[Peter]

Hi Issac96. I checked Udcnom inputting values from 300v down to 50v in 50v steps. Interesting results too.
Boost 1830 to 303.
Fweak 131 to 791.
From this Boost is too low so I would have to send the Boost value via CAN and not use Udcnom, therefore Fweak would be sent separately too maybe.
My next test will be to set Boost lower than (3500) and Fweak higher than (125) and see how it runs then vice versa.
From this I hope to see what switching values with gear change will achieve.

[Peter]

Did some testing last eve.
Setting Boost lower (6500 > 3500) and Fweak higher (125 > 185) was a step backwards, sluggish acceleration but still got to top speed... eventually ! Raised Boost (6500 > 7000) and Fweak (125 > 150) together, better take off and acceleration slightly better throughout the rev range. Raised current limit too (420 > 440) which no doubt helped by stopping shut down with this higher Boost. Will try to lift both values again this evening and report back.
I am sure if I could raise current limit higher still it would be awesome.... higher rated igbt's and a higher rated fuse for Xmas ??

[jon volk]

If sending CAN commands for various parameters, they reset to the saved flash settings on power cycle, correct?

[johu]

If sending CAN commands for various parameters, they reset to the saved flash settings on power cycle, correct?

yes