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Can't ajust braking torgue with Plettenberg Predator 30/8

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VescBuilder
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Can't ajust braking torgue with Plettenberg Predator 30/8

Hi,

I've got this powerful motor: http://www.plettenberg-motoren.net/index.php/en/plettenberg-motors/plett...

It is successfully connected to my VESC (HW 4.12, FW 3.33).

Motor is rotating well, but my task is to apply some user-defined braking torque when motor is used as generator.

I tried:

- use SuperCap power supply or standalone power supply

- set Handbrake current or Brake current to different values (when it is below 0.1A  there is no brake torque at all, else it equal to Full brake torque)

- use PPM application (the same result - zero torque or full torque)

- tweak some settings

Anyway I still have only two options: no brake torque or full brake torque.

May be somebody knows what I'm doing wrong? 
Thank you in advance.

Best regards

benjamin
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If you set a brake current when the motor is not moving it will switch to shorting all three phases as it cannot reach the desired braking current without movement, and if you move it after that the brake will be much stronger as the phases are still shorted. Changing this behavior is tricky as active braking has to be applied at low speeds before the motor stops, and it is not easy to tell if it starts moving in the other direction instead of just braking. Have you tried using one of the braking commands while the motor is moving?

VescBuilder
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Thank you for your reply.

"Have you tried using one of the braking commands while the motor is moving?"

I have tried and it works as it should be (braking torque depends on set value).

I guess what I need is: synchronous rectifier + dc/dc buck/boost converter + SuperCap battery (cause it can be charged with large current).

Can I use my VESC hardware to do that?

 

Best regards

VescBuilder
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So I made it works in the next steps:

1. Release motor (Switch off button)

2. Rotate motor with external motor

3. Brake with custom current (Brake current button)

The last problem is how to disable shortening phases function to achieve smooth braking torque from start?

Should I go to program STM32 or it is possible to do in some other way?

Thank you in advance for your reply.

br

benjamin
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to begin in a stopped braking state and get smooth braking when applying force is tricky without sensors as I mentioned before. It should be possible with an encoder and a firmware update, but it requires a bit of work. Easier would probably be to set a minimum RPM for when braking is used and skip the shorting of the three phases.

VescBuilder
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It is not a problem to install encoder and I will do it. 
The problem for me is to learn and modify firmware. I think it will take me weeks or even months and maybe several VESCs bricked.

Could you include this, I believe, useful function in your ToDo list? If not, point me which place in code I should learn and modify, please.

Thank you in advance.

 

 

benjamin
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I will have a look. It is in the software TODO list now:

http://vesc-project.com/node/110