Page 1 of 1

VESC 6, astroflight 3215, loosing sync with freewheel

Posted: May 10 2020 5:39pm
by Rouckie
Hello,



I have a mountainbike with a astroflight 3215 connected to the rear wheel with a 2 stage reduction. On the intermediate shaft I have a freewheel, the ratio from the motor to this shaft is 4:1.
motor controller is a vesc 6.4
Battery is 12s.
motor kv is 169
Phase current set to 60 A
throttle controls duty cycle


The motor wizard did a good job and the combination works great, except for one big problem.

Problem:

When I reapply throttle after coasting (wheel spinning at 10 - 30 kph. motor stopped, freewheel working.), it happens that the motor starts making a squeezing sound and doesn't move anymore.
I think the controller looses sync
seems only to happen at certain throttle position while reapplying it. low throttle or full throttle seems to work ok. Half throttle seems to give the problem.
squeezing sound continues until I disconnect the battery


What I think happens:

The motor spins up
when the motor speed matches the wheel speed, the freewheel engages abruptly and causes a big torque ripple.
controller looses sync


Is this a known issue?

Can I tweak some parameters to solve this problem?



thank you!



Roel

Re: VESC 6, astroflight 3215, loosing sync with freewheel

Posted: May 11 2020 1:46pm
by Pedrodemio
You shouldn't use duty cycle mode on VESC since it doesn't have free wheel, when you release the throttle it starts to brake since the duty cycle you want is now 0%

Try using current no reverse with brake

Re: VESC 6, astroflight 3215, loosing sync with freewheel

Posted: May 11 2020 2:14pm
by Rouckie
I belive the problem occurs when re-applying throttle, not when closing the throttle.
Anyway, I will try your suggestion and post the result.

Thank you

Re: VESC 6, astroflight 3215, loosing sync with freewheel

Posted: May 13 2020 2:13pm
by Rouckie
Hello,

just to let you know that the problem seems to be solved. However, I did only test for a short time, and also limited the power. Tomorrow I will do some more testing and certainly in the weekend.

thanks

Re: VESC 6, astroflight 3215, loosing sync with freewheel

Posted: May 15 2020 3:55am
by Rouckie
Did some more testing on full power. Problem did not occur once.

Seems solved. Thanks @ Pedrodemio !!

Re: VESC 6, astroflight 3215, loosing sync with freewheel

Posted: May 15 2020 8:17am
by Pedrodemio
Glad it's solved, the duty cycle mode on the VESC behaves completely different than what most people are used to on other ESCs