Emergency braking concept for VESC

General topics and discussions about the VESC and its development.
kitewinder
Posts: 19
Joined: 29 May 2017, 20:47
Location: Bordeaux

Re: Emergency braking concept for VESC

Postby kitewinder » 27 Jun 2017, 19:42

Does somebody knows why it seems not possible to brake using bldctool at less than 1 Amps?
I'd like to use smooth brake , that is why being able to start breaking at 0.1 Amps will be much more interesting....
you can check by setting value between 0 and 0.99, nothing happens. then set it to 1 and then you start breaking .

e-biker
Posts: 18
Joined: 14 Aug 2016, 13:20
Location: Lithuania

Re: Emergency braking concept for VESC

Postby e-biker » 28 Jun 2017, 08:43

Go to motor configuration -> advanced -> current control -> min current and change to the value you want. By default it is set to 1 amp.

kitewinder
Posts: 19
Joined: 29 May 2017, 20:47
Location: Bordeaux

Re: Emergency braking concept for VESC

Postby kitewinder » 03 Jul 2017, 10:37

Thanks E-biker for your reply.
I tried this but it does not change anything, I can just break at a minimum of 1A.
Plus I notice that the effective measured current in the motor is not 1A but a lot more higher.
Did I miss something on the configuration on the board? There might be some sort of calibration for the current ?

e-biker
Posts: 18
Joined: 14 Aug 2016, 13:20
Location: Lithuania

Re: Emergency braking concept for VESC

Postby e-biker » 03 Jul 2017, 11:53

Auto calibration is implemented in software so i don't think that it is realted with that. What are you using FOC or BLDC?

Maybe later I can try to repeat it by my self.

pf26
Posts: 309
Joined: 28 Mar 2016, 14:37
Location: FR Valence

Re: Emergency braking concept for VESC

Postby pf26 » 03 Jul 2017, 12:25

If you want to control low currents, you should go for a higher shunt value. Otherwise it will be very difficult for the VESC to be accurate. Obviously this assumes that you don't also need high currents at other times for the same project.

kitewinder
Posts: 19
Joined: 29 May 2017, 20:47
Location: Bordeaux

Re: Emergency braking concept for VESC

Postby kitewinder » 04 Jul 2017, 06:55

Pf26 : what you say makes a lot of sense since i am using the vesc at a really lot current. In fact we use the VESC for a wind turbine project so that we mainly use regenerative braking. max current does not go higher than 5 amps.

Have you ever done that? i'm pretty sure a change of current measuring shunt implies a slight change in the software. do you know where this change shall be made ?

rew
Posts: 943
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: Emergency braking concept for VESC

Postby rew » 04 Jul 2017, 07:02

Yes. In conf_general.h you can select your hardware version.
Then in hwconf/hw_<yourversion>.h you can change the shunt value.

It would be best to first test-compile your own firmware before you start modifying firmware AND hardware.

kitewinder
Posts: 19
Joined: 29 May 2017, 20:47
Location: Bordeaux

Re: Emergency braking concept for VESC

Postby kitewinder » 04 Jul 2017, 09:33

Super , Thanks rew, I have seen were the modif shall take place.

i can also change the gain of the amplifier.

Now I have to change the shunt value to 0.01 ohms and this shunt with specific footprint does not exist in such value.... Damn

rew
Posts: 943
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: Emergency braking concept for VESC

Postby rew » 05 Jul 2017, 05:35

On my VESC-derived boards, I simply use a 2W 2512 SMD resistor. Dit does not survive blowing up the FETs, but then again, what use is it that the $0.10 component outlives the $2.50 FETs.

kitewinder
Posts: 19
Joined: 29 May 2017, 20:47
Location: Bordeaux

Re: Emergency braking concept for VESC

Postby kitewinder » 05 Jul 2017, 07:30

Rew. could you please send me a picture of your soldering.
That is what I order yesterday, 2512 case smd resistor.
I was thinking about soldering 2 of them side by side so that i get a 2524 like casing.

I think I will forst change the shunt value in firmware, check the impact on measure and comparing with lab power supply. then I will change the shunts.

I have never flashed the firmware. is there a tutorials for that ? so that changes in " hwconf/hw_<yourversion>.h " are taken it account?

thanks for the great help guys !


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