Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
116
Setting Up Turbo PMAC-Based Commutation and/or Current Loop
Establishing a Phase Reference
Purpose
When commutating a synchronous multi-phase motor such as a permanent-magnet brushless motor, the
commutation algorithm must know the absolute position of the rotor. With an absolute sensor such as a
resolver, the phase referencing must be done just once, on assembly of the system. With an incremental
sensor such as an incremental optical encoder, the phase referencing must be done every time the system
is powered up. If incremental sensor power on signal is lost, even if controller power is retained, the
phase referencing must be done again before enabling the signal.
commutation algorithm must know the absolute position of the rotor. With an absolute sensor such as a
resolver, the phase referencing must be done just once, on assembly of the system. With an incremental
sensor such as an incremental optical encoder, the phase referencing must be done every time the system
is powered up. If incremental sensor power on signal is lost, even if controller power is retained, the
phase referencing must be done again before enabling the signal.
Hall-effect commutation sensors, or their equivalent on an optical encoder, are absolute, but of a very low
resolution (+30oe). In a high-performance application, they are suitable to create a rough, temporary
phase reference, permitting movement until a more accurate reference is established.
resolution (+30oe). In a high-performance application, they are suitable to create a rough, temporary
phase reference, permitting movement until a more accurate reference is established.
The index pulse on an incremental encoder is absolute with high accuracy, but in general, there must be
movement before this pulse is reached. This requires at least a rough phasing, either from a low-
resolution absolute sensor such as hall effect, or from a power-on phasing search.
movement before this pulse is reached. This requires at least a rough phasing, either from a low-
resolution absolute sensor such as hall effect, or from a power-on phasing search.
WARNING:
It is important for the safety of the machine that a reliable phase referencing
method be used, whether with an absolute or incremental sensor. If the phase
reference is incorrect by more than 1/4 of the phasing cycle, runaway will occur
when the servo loop is closed. Test the phase referencing carefully with a bare
motor before attaching a load, to make sure the method is reliable. Before
attaching a load, make sure that the Turbo PMAC fatal following error limit
parameter Ixx11 and the amplifier overcurrent fault are active and working
properly. Also make sure that required mechanical protections are in place.
method be used, whether with an absolute or incremental sensor. If the phase
reference is incorrect by more than 1/4 of the phasing cycle, runaway will occur
when the servo loop is closed. Test the phase referencing carefully with a bare
motor before attaching a load, to make sure the method is reliable. Before
attaching a load, make sure that the Turbo PMAC fatal following error limit
parameter Ixx11 and the amplifier overcurrent fault are active and working
properly. Also make sure that required mechanical protections are in place.
Preparation
These tests require that both the commutation and current loop be working properly. Double-check that
the setup variables are correct for these actions, especially ones that may have been changed for earlier
tests. For motor 1, make sure:
the setup variables are correct for these actions, especially ones that may have been changed for earlier
tests. For motor 1, make sure:
•
I100=1 to activate the motor
•
I101=1 to enable commutation
•
I170 and I171 are set to their proper value
For these tests, we will want access to the motor phase position register, where Turbo PMAC keeps track
of where it is in the phase cycle. The phase position register is 48 bits long, using both X and Y memory.
The Y-memory portion of this register has only fractional information, so we will use only the X-memory
portion. Its units are (counts*Ixx70). The registers are:
Phase Position Angle Registers
of where it is in the phase cycle. The phase position register is 48 bits long, using both X and Y memory.
The Y-memory portion of this register has only fractional information, so we will use only the X-memory
portion. Its units are (counts*Ixx70). The registers are:
Phase Position Angle Registers
Motor
#
1 2 3 4 5 6 7 8
Address X:$00B4
X:$0134
X:$01B4
X:$0234 X:$02B4 X:$0334 X:$03B4 X:$0434
Motor
# 9 10 11 12 13 14 15 16
Address X:$04B4
X:$0534
X:$05B4
X:$0634 X:$06B4 X:$0734 X:$07B4 X:$0834
Motor
#
17 18 19 20 21 22 23 24
Address X:$08B4
X:$0934
X:$09B4
X:$0A34
X:$0AB4 X:$0B34 X:$0BB4 X:$0C34
Motor
#
25 26 27 28 29 30 31 32
Address X:$0CB4
X:$0D34
X:$0DB4
X:$0E34 X:$0EB4 X:$0F34 X:$0FB4 X:$1034