BLDC FOC Acceleration time reduction

Discussions regarding the Field Oriented Control (FOC) implementation on the VESC.
anroop
Posts: 13
Joined: 28 Feb 2017, 12:45
Location: India, Chennai

BLDC FOC Acceleration time reduction

Postby anroop » 16 Mar 2017, 07:59

Hi,

End Application : Custom application to drive 200 Grams load from 0 to 12000 RPM in < 1.5 sec
Load type : 200 Gram 150 mm dia plastic disc
ESC : VESC 4.12 from maytech (http://www.maytech.cn/en/mtvesc50a/10331.html)
Motor : 449470 (http://www.maxonmotor.in/maxon/view/pro ... C-i/449470)

Inertia calculated : 5625 g/cm2
Torque required : 0.7 Nm

Present operation scenario :
FOC sensor mode, Shunts changed to 1 mOhm to 10 mOhm, Firmware remains the same (as for 1 mOhm shunt), 0-60 VDC power source (set to 52 VDC), 2 A continuous current - Using this we are able to accelerate a smaller load form 0 to 12000 RPM in 2~3 seconds. How do I achieve <1.5 Second acceleration from 0 to 12000 RPM for the smaller load (~50 grams, later would also try to check with 200 grams load). I assume the PID current control and parameters in the Advanced section somehow relates to the acceleration curve the prevent me from instantaneous acceleration (1.5 second). If someone could guide me to tweak these parameters that may improve my system will be helpful.

About the Firmware :
Since, I replaced 1 mOhm to 10 mOhm I have set current parameters on BLDC tool to be 10x of values rated by the motor (motor nominal continuous current is 2.5 A so I have set the motor max current to 60 A (6 A as max inrush and 10x of 6A gives 60 A)), similarly I have used scaled values for detecting the motor parameters and Hall sensors (FOC sensor operation). But if this would still affect my operations I would preferably change the values


Neither i have any platform to edit the firmware nor i have firmware files. All i have is the BLDC tool software and bin files of firmware.
I have worked in pic and avr platforms, so i can understand the code and change it accordingly. But I need to know where can i edit the code and where can i get the firmware codes. If changing the firmware would help me improve my units performance I'm glad to do it. please suggest me a suitable opensource compiler & "how to" for the same.



Anybody with possible relations and help are welcome...

pf26
Posts: 278
Joined: 28 Mar 2016, 14:37
Location: FR Valence

Re: BLDC FOC Acceleration time reduction

Postby pf26 » 16 Mar 2017, 10:02

I would use dutycylemode, lower the max motor current to get the required torque to accelerate as fast as needed, and set the dutycycle to the one needed to reach 12000RPM.

It is not a good practice to post twice the same subject in 2 different places.

rew
Posts: 904
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: BLDC FOC Acceleration time reduction

Postby rew » 16 Mar 2017, 22:34

anroop wrote:I have worked in pic and avr platforms, so i can understand the code and change it accordingly. But I need to know where can i edit the code and where can i get the firmware codes. .
Here is the firmware source code: https://github.com/vedderb/bldc

anroop
Posts: 13
Joined: 28 Feb 2017, 12:45
Location: India, Chennai

Re: BLDC FOC Acceleration time reduction

Postby anroop » 10 Apr 2017, 13:32

Hi,
I tried installing the some compilers for compiling the code after changing the code of shunt from 0.001 to 0.010, but failed. can someone please send the recompiled code for the same. so that I can load it and test it out. coz my ESC resets frequently when i decelerate it instantaneously.

refer attachment for Current values (actual values are [x/10] than listed, since using 10 m Ohm instead of 1 m Ohm resistor with 1 m ohm's code)
Attachments
125.png
125.png (19.88 KiB) Viewed 1557 times

rew
Posts: 904
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: BLDC FOC Acceleration time reduction

Postby rew » 14 Apr 2017, 06:37

Remind me: What power source are you using? What voltage?

arvidb
Posts: 206
Joined: 26 Dec 2015, 14:38
Location: Sweden, Stockholm

Re: BLDC FOC Acceleration time reduction

Postby arvidb » 14 Apr 2017, 08:00

anroop wrote:coz my ESC resets frequently when i decelerate it instantaneously.

Do you have anything that can sink the energy regenerated while braking? If you are using a lab power supply it probably cannot sink current, and if you cannot sink current you will get an overvoltage condition as soon as you do regenerative braking (which is the only kind of braking that the VESC can do). (This is why I built an energy dump circuit.)

anroop
Posts: 13
Joined: 28 Feb 2017, 12:45
Location: India, Chennai

Re: BLDC FOC Acceleration time reduction

Postby anroop » 21 Apr 2017, 10:45

rew wrote:Remind me: What power source are you using? What voltage?

Hi Rew,
I'm using 48VDC (Variable till 56 VDC), 10 A rated power supply (http://www.mouser.com/ds/2/260/mean%20w ... 342993.pdf).
Last edited by anroop on 21 Apr 2017, 10:49, edited 1 time in total.

anroop
Posts: 13
Joined: 28 Feb 2017, 12:45
Location: India, Chennai

Re: BLDC FOC Acceleration time reduction

Postby anroop » 21 Apr 2017, 10:48

arvidb wrote:
anroop wrote:coz my ESC resets frequently when i decelerate it instantaneously.

Do you have anything that can sink the energy regenerated while braking? If you are using a lab power supply it probably cannot sink current, and if you cannot sink current you will get an overvoltage condition as soon as you do regenerative braking (which is the only kind of braking that the VESC can do). (This is why I built an energy dump circuit.)

Hi arvidb,
I don't have any circuit/components added other than VESC itself (with inbuilt capacitors on the input supply lines). Have you tested this Power dump circuit of yours with load?. Is it reliable?
Last edited by anroop on 21 Apr 2017, 11:47, edited 1 time in total.

arvidb
Posts: 206
Joined: 26 Dec 2015, 14:38
Location: Sweden, Stockholm

Re: BLDC FOC Acceleration time reduction

Postby arvidb » 21 Apr 2017, 11:20

anroop wrote:Have you tested this Power sump circuit of yours with load?. Is it reliable?

I have tested it using a second power supply to apply overvoltage on the VESC side and checked that it caps the voltage and sinks current as it should (I've tested it to 5 A for 10-15 seconds or so). I've also used it successfully to dump the energy from a spinning motor, but that motor did not have any load except its own inertia.

I've only used it a few times so I cannot speak about its reliablility, but it seems to do what it should!

anroop
Posts: 13
Joined: 28 Feb 2017, 12:45
Location: India, Chennai

Re: BLDC FOC Acceleration time reduction

Postby anroop » 26 Apr 2017, 05:53

arvidb wrote:
anroop wrote:Have you tested this Power sump circuit of yours with load?. Is it reliable?

I have tested it using a second power supply to apply over-voltage on the VESC side and checked that it caps the voltage and sinks current as it should (I've tested it to 5 A for 10-15 seconds or so). I've also used it successfully to dump the energy from a spinning motor, but that motor did not have any load except its own inertia.

I've only used it a few times so I cannot speak about its reliability, but it seems to do what it should!


Hi Arvidb,
Thanks for your information and support. I'll try what you have suggested, could you mention the power ratings of the components you have used ? (possibly it'll take a little more time than expected).
Meanwhile, if there are any solutions on the software front that I could do to over come the issue I'm facing ?


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