8i20 setup current limits etc.

So, i have my 8i20 card doing its reference thing ("iq") I'm not getting a lot of response from shifting the start angle, the encoders "z" isn't set to phase zero. It works once referenced but doesn't have as much force as it should. I have tried setting the max and min limit as below.

setp hm2_5i23.0.8i20.0.2.current-minlim -7.5
All this does is makes the motor roll in one direction and the pid tune dosent seem to do anything. (It does without the min/max current setp statements) just seems to not be putting out full current.

maxlim and minlim should have the same absolute value
If you want full current you should set maxlim to 30 and minlim to -30

The motor is rated at 8.4a, shorthand be enough? Or should it be 30 ?

Is that continous or peak current?
If continous, then drive can be set much higher, but i would stay in the 15A range untill everything is working properly, then decide if it needs to be higher.

Yes. peak current can be 3 to 6 x the continuous current.

You should set the current limit to the drives peak current.

Okay,  so the problem im realising now is that my encoder "z" signal isn't set to the motor zero point. ( I read somewhere that you need to apply a dc voltage to u, with v and w connected to the other polarity. To get the motor zero point). There doesn't seem to be any offset available to correct this.  Is there?

M4MazakUser wrote:

Okay,  so the problem im realising now is that my encoder "z" signal isn't set to the motor zero point. ( I read somewhere that you need to apply a dc voltage to u, with v and w connected to the other polarity. To get the motor zero point). There doesn't seem to be any offset available to correct this.  Is there?

Are you using the bldc component? If you are, that has a parameter bldc.N.encoder-offset s32 rw [if personality & 0x0A] (default: 0)The offset, in encoder counts, between the motor electrical zero and the encoder zero modulo the number of counts per electrical revolution

Yeah I've been using this.

I measured 781 counts from encoder zero this morning. Its an 8 pole motor so should the value be 269?
Subtract 512 for previous pole, etc

Should lead angle be 45deg?

Bldc scale for a 1024 encoder I've set to 4096?
It moves .4mm ish currently then stops until ferror of 20mm (set to 20 for testing)
Cant find anything to cause this.

M4MazakUser wrote:

I measured 781 counts from encoder zero this morning. Its an 8 pole motor so should the value be 269?
Subtract 512 for previous pole, etc

I tried to use science and maths setting up one of my axes (which had an offset) and gave up.
In the end I tweaked the value until the motor (unloaded) ran at equal speed in both directions for a fixed current command.

Should lead angle be 45deg?

For an 8i20 it should be zero, the 8i20 expects to the sent the _rotor_ angle and handles the phase angle offset internally.