Motor Skipping When Held in Place, No Torque Applied

General topics and discussions about the VESC and its development.
hohungyi
Posts: 15
Joined: 03 Jun 2017, 12:19
Location: Singapore

Motor Skipping When Held in Place, No Torque Applied

Postby hohungyi » 10 Aug 2017, 09:20

Hi guys,

Would anybody be able to give guidance on what could be happening here?



When I hold the wheel/motor in place and apply a current to drive it, the motor will attempt to overcome the resistance holding it in place for a brief moment, before totally letting off on the driving force and only giving a clicking sound. Towards the end of the video there is no resistance anymore and I will have to put the remote back to neutral and drive again before the motor and wheel will start to move.

I checked against BLDC tool and there is no fault incurred (originally suspected it was over current but nope, no fault), so am confused as to what it might be.

Below are the settings used:

Battery 9S2P
Motor 5065

Motor and Batt Max 40A
Motor and Batt Min -20A
Absolute Max 130A

Everything else is default settings.

Would appreciate advice! Thanks!

linsus
Posts: 34
Joined: 24 Apr 2016, 10:20

Re: Motor Skipping When Held in Place, No Torque Applied

Postby linsus » 10 Aug 2017, 13:14

Hi,

What mode are you using? FOC or BLDC?
Is this only in the startup sequence or in other high load relations such as uphill?

I recognize the clicking sound, I had a some issues with my DRV and a resistor(or was it a cap?) Close to one of the FETs had flown of the PCB somehow. My motor didint rotate at all tho, just feint clicks like in the end there.

Even if you dont get a fault, did you try a different setting on the current limits to see if it still occured?

hohungyi
Posts: 15
Joined: 03 Jun 2017, 12:19
Location: Singapore

Re: Motor Skipping When Held in Place, No Torque Applied

Postby hohungyi » 10 Aug 2017, 16:03

Thanks!

Running it in BLDC, and yes it happens during high load up an incline as well. The video demonstrates the conditions for high load, hence it replicates the issue too.

Have played around on the current limits (up and down in 1A increments), also around in integrator limits (up and down in increments of 5), and BEMF coupling as well (increments of 50), at some stages it seems to get better (more load to induce the situation), but none completely eliminates this issue.

I'll take a look at my DRVs and FETs!

elux
Posts: 10
Joined: 15 Apr 2017, 00:33
Location: Detroit

Re: Motor Skipping When Held in Place, No Torque Applied

Postby elux » 12 Aug 2017, 00:46

In BLDC Tool on the Advanced tab you can try adding a few Amps of Startup boost (start with 5 Amps, no more than 20 Amps with a 5065 motor).

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

Re: Motor Skipping When Held in Place, No Torque Applied

Postby rew » 12 Aug 2017, 13:01

When you keep it in plave, you ARE applying torque.

The problem with BLDC motors is that you have to measure the back EMF to know where the rotor is. The back EMF is proportional to turning speed. So when the motor is at a standstill, there is literally nothing to go on. So... when starting from a standstill the only thing that the controller can do is to apply a rotating magnetic field and hope that the motor starts turning.

To get reliable startup at more-than-expected load, you need sensors.

hohungyi
Posts: 15
Joined: 03 Jun 2017, 12:19
Location: Singapore

Re: Motor Skipping When Held in Place, No Torque Applied

Postby hohungyi » 17 Aug 2017, 12:26

What I meant in the title is that at the end of the video, the motor just "gives up" and stutters without attempting to apply any torque.

I understand sensored motors will give more reliable motor positioning readings and low RPM power, but my concern is that in the case of riding up a hill and there is an application of a surge in current, will the motor also cut out like this.

FETs seem fine, checking DRVs now.

linsus
Posts: 34
Joined: 24 Apr 2016, 10:20

Re: Motor Skipping When Held in Place, No Torque Applied

Postby linsus » 21 Aug 2017, 08:21

Only one way to find out ;)

Grab a helmet and find a hill!


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