Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
Setting Up Turbo PMAC-Based Commutation and/or Current Loop
123
M171=I171/12
; Set phase angle to 30 deg
P170=1
; Phasing OK flag
ENDIF
IF (M128&7=0 OR M128&7=7)
; Invalid states
P170=0
; Phasing not OK
ENDIF
IF (P170=1)
; Phasing OK?
M148=0
; Clear phasing error bit
CMD"#1J/"
; Enable motor
ELSE
CMD"#1K"
; Not OK; disable motor
ENDIF
DISABLE PLC 1
; So program will not repeat
CLOSE
Notes on this program:
•
The reason for the &7 (bit-by-bit AND with 7 [0111]) operation is to remove the effect of the T-flag
input, which is the most significant bit of the 4-bit M-variable.
input, which is the most significant bit of the 4-bit M-variable.
•
This phasing estimate has a potential error of +30oe.
This tentative phasing will serve until we move the motor to the encoder index pulse, at which time we
will force M171 to the value we found with the fine phasing.
will force M171 to the value we found with the fine phasing.
Power-On Phasing Search
If a non-absolute sensor is used for commutation, Turbo PMAC must perform a search move for the
proper phasing reference every time it powers up (with an absolute sensor, this needs to be done only
once in the development of the system). There are several ways to do this phasing search. Turbo PMAC
has two automatic methods executed by firmware; other methods or enhancements of these methods can
be executed with PLC programs.
proper phasing reference every time it powers up (with an absolute sensor, this needs to be done only
once in the development of the system). There are several ways to do this phasing search. Turbo PMAC
has two automatic methods executed by firmware; other methods or enhancements of these methods can
be executed with PLC programs.
A power-on phasing search permits commutation of permanent-magnet brushless motors without the need
for a more expensive and possibly less accurate absolute sensor. However, a phasing search may not be
dependable in some applications; in these cases an absolute sensor will be required.
for a more expensive and possibly less accurate absolute sensor. However, a phasing search may not be
dependable in some applications; in these cases an absolute sensor will be required.
The estimate from a power-on phasing search should be within +1-2oe of the true zero position, so many
people will just use the phasing established here throughout the application. It is possible also to adjust
the estimate when settled at the index pulse, using the results of the fine phasing test described above.
people will just use the phasing established here throughout the application. It is possible also to adjust
the estimate when settled at the index pulse, using the results of the fine phasing test described above.
WARNING:
An unreliable phasing search method can lead to a runaway condition. Test the
phasing search method carefully to make sure it works properly under all
conceivable conditions. Make sure the Ixx11 fatal following error limit is active
and as tight as possible so the motor will be killed quickly in the event of a serious
phasing search error.
phasing search method carefully to make sure it works properly under all
conceivable conditions. Make sure the Ixx11 fatal following error limit is active
and as tight as possible so the motor will be killed quickly in the event of a serious
phasing search error.
When properly phased, a positive O-command should cause movement in the positive direction; a
negative O-command should cause movement in the negative direction. If the opposite results are
received, there will be a dangerous runaway condition when the servo loop is closed.
negative O-command should cause movement in the negative direction. If the opposite results are
received, there will be a dangerous runaway condition when the servo loop is closed.
Two-Guess Phasing Search
Turbo PMAC’s first automatic phasing search method is called the two-guess phasing search, because it
makes two arbitrary guesses as to the phase position, briefly applies a torque command using each guess,
and observes the response of the motor to each command. Based on the magnitude and direction of the
two responses, Turbo PMAC calculates the proper phasing reference point. It then starts the commutation
based on this reference, and closes the servo loop to hold position.
Turbo PMAC’s first automatic phasing search method is called the two-guess phasing search, because it
makes two arbitrary guesses as to the phase position, briefly applies a torque command using each guess,
and observes the response of the motor to each command. Based on the magnitude and direction of the
two responses, Turbo PMAC calculates the proper phasing reference point. It then starts the commutation
based on this reference, and closes the servo loop to hold position.