Reference Manual

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PMAC 2 Software Reference

106 PMAC I-Variable Specifiation

In the manual technique, give the motor an O0 command. Put a bias on the A phase

(higher-numbered DAC of a PMAC1 pair) by setting Ix29; use a positive bias if Ix72=171

or 192 (2000 is usually a good value); use a negative bias if Ix72=85 or 64. Also put a bias

in the opposite direction of the same magnitude on the B phase by setting Ix79. The motor

should lock in on a position like a stepper motor.

Now remove the A-phase bias by setting Ix29 back to zero, or at least to the value you

have found to force zero current in the phase, and the motor should lock in on another

position. This position is the zero position of the phasing cycle.

In either technique for forcing the motor to its zero commutation position, after you are

sure the motor has settled, read the position of the absolute sensor by querying its M-

variable value.

Take the negative of this value, multiply it by Ix70, and put the resulting value in Ix75.

Now, with Ix79 returned to zero or the proper bias, and Ix81 pointing to the absolute

sensor, give the motor a $ command. The motor should be properly phased. Remember to

save these variable values before doing a full reset on the card.

For use with the SETPHASE command, define an M-variable to the the phase position

Execute the above sequence with Ix29 and Ix79 to force the motor to the zero-point in its

phase cycle. Set the M-variable to zero (e.g. M171=0). Now move the motor to the

known position in its cycle (usually with a homing search move), let it settle, and read the

M-variable value. This value will be put in Ix75.

Example

On a brushless motor #1 commutated from PMAC with Ix70 =1 and Ix72 = 171, using an

R/D converter at location 0 of a board at multiplexer address 0, the following on-line

commands can be used to set Ix75:

M171->TWR:0,0 ;Resolver position

#1O0 ;Open-loop zero command

I129=2000 ;Pos bias on first phase output (Neg if Ix72=85 or 64)

I179=-2000 ;Neg bias on second phase output (Pos if Ix72=85 or 64)

I129=0 ;Remove bias from first phase output

M171 ;Query sensor position

223 ;PMAC responds

I175=-223 ;Set phasing position offset (223*-1*Ix70)

I179=0 ;Remove bias from second phase

I181=$000100 ;Set power-on position address

I173=0 ;Make sure no phasing search move is done

I174=0 ;Make sure no phasing search move is done

SAVE ;Store I-variables in non-volatile memory

$ ;Try phasing from absolute position sensor