8i20 setup current limits etc.

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.

bldc.N.rotor-angle float out (default: 0)

Rotor angle after encoder zeroing etc. Useful for angle/current drives which add their own phase offset such as the 8i20. This value has a range of 0 to 1 and measures electrical revolutions. It will have two zeros for a 4 pole motor, three for a 6-pole etc

so i should be sending it this??
or do you mean this? bldc.N.encoder-offset
ill try it out when im back at the workshop with a zero lead angle.

Thanks heaps,  moving on to the next problem now 
The issue was the angle should have been 0, and I changed the encoder input to bldc to negative to reverse the phase rotation.  -important to realise that there is phase rotation direction,  and encoder direction. The encoder-offset turned out to be the figure i got from connecting the motor to a 12v battery. U to +, v w to negative.  
after all this, I did a quick torque mode tune and it was great!
Next issue is the x axis brake dosent want to let go. May be a broken wire...