User's Manual

PMAC User Manual
94 Setting Up PMAC Commutation
Saving Values
Once confirmed that the proper phasing can be reached with the $ command, save the parameters into
permanent memory with the SAVE command and do a full card reset with the $$$ command. If Ix80
was saved as 1, the motor should be enabled and in closed-loop position control immediately after the
reset, although if the servo loop has not been tuned, it may not be very stiff. Regardless good response
should be received from open-loop commands.
If Ix80 was saved as 0, the absolute phase position will have been done during the reset, but the motor
will be left in the disabled (killed) state. It can be enabled with either open loop or jog commands. A $
command will also enable the motor (closed-loop), doing another absolute position read in the process.
If the motor performs open-loop commands well in both directions at this point, the commutation setup is
finished, and the motor is ready for servo-loop tuning.
Phasing Referenced to Hall-Effect Sensor
PMAC can use hall-effect commutation sensors or their equivalent for an approximate phase referencing
on power-up. This phase referencing is good to +/-30
o
of the commutation cycle, which is enough to get
reasonable torque and reasonable smoothness without any phasing search. The final phase reference can
then be done when the index pulse is found. Usually the index pulse is part of the home position trigger,
so after the homing search move is done, the phase position is adjusted based on a measurement that was
done during development.
Setting bit 23 of Ix81 to 1 specifies a hall-effect power-on phase reference. In this case, the address
portion of Ix81 specifies a PMAC X-address, usually that of an otherwise unused flag register matching
the second DAC output for the motor. For example, a motor using DACs 1 & 2 for the commutated
outputs would use Flags 1 at X:$C000 for its main flags and Flags 2 at X:$C004 for its hall-effect inputs.
PMAC expects to find the hall-effect inputs at bits 20, 21, and 22 of the specified register. In a flag
register, these bits match the HMFLn, -LIMn, and +LIMn inputs, respectively. Traditionally hall-effect
inputs are labeled U, V, and W. The U input is bit 22 (+LIMn), V is bit 21 (-LIMn), and W is bit 20
(HMFLn).
The hall-effect signals must each have a duty cycle of 50% (180
o
e). PMAC can use hall-effect
commutation sensors separated by120
o
e. There is no industry standard with hall-effect sensors as to
direction sense or zero reference, so this must be handled with software settings of Ix81.
Bit 22 controls the direction sense of hall-effect sensors as shown in the following diagram, where a value
of 0 for bit 22 is standard and a value of 1 is reversed:
U
V
W
-30 30 90 -150 -90
1
0
1
0
1
0
30 -30 -90 90150
Sta
n
da
r
d
:
R
e
v
e
r
sed
:
1
3
2
150
-150
6
4
5
Figure 16 Hall Effect Waveform Diagram