Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
Setting Up Turbo PMAC-Based Commutation and/or Current Loop
117
This register normally varies from -Ixx71/2 to +Ixx71/2, although if monitoring it, sometimes it will jump
by Ixx71 units and be temporarily outside this range. This is normal behavior. Access to this register is
useful in many ways for establishing a phase reference. Define the suggested M-variable for the Motor 1
phase position register:
by Ixx71 units and be temporarily outside this range. This is normal behavior. Access to this register is
useful in many ways for establishing a phase reference. Define the suggested M-variable for the Motor 1
phase position register:
M171->X:$00B4,0,24,S
; Motor 1 phase position (counts*Ixx70)
Add this M-variable to the Watch window.
Current-Command Six-Step Test
The basic technique we will use here, either for a one-time phase reference with an absolute sensor or
power-up phase reference with an incremental sensor, is all or part of the current command six-step test.
This is similar to the voltage command six-step test described above, except the current loops are active.
We use the ADC input offset registers to bias the phase current feedback, and hence the phase command
outputs, to drive the motor as a stepper motor to a particular location in the commutation cycle, usually
the 0
power-up phase reference with an incremental sensor, is all or part of the current command six-step test.
This is similar to the voltage command six-step test described above, except the current loops are active.
We use the ADC input offset registers to bias the phase current feedback, and hence the phase command
outputs, to drive the motor as a stepper motor to a particular location in the commutation cycle, usually
the 0
o
position. Then we can write a 0 to the phase position register.
Ixx29 is the A-phase offset; Ixx79 is the B-phase offset. The third phase is not directly commanded;
Turbo PMAC will command it automatically as part of the digital current loop to balance the first two
phases. For motor 1, the following sequence of commands for the current six-step test, and the expected
results, could be:
Turbo PMAC will command it automatically as part of the digital current loop to balance the first two
phases. For motor 1, the following sequence of commands for the current six-step test, and the expected
results, could be:
#1O0
; Open loop command of zero magnitude
I179=3000 I129=0
; Step 1: (A) 0
o
elec.; (B) 180
o
elec.
I179=3000 I129=-3000
; Step 2: (A) -60
o
elec.; (B) 120
o
elec.
I179=0 I129=-3000
; Step 3: (A) -120
o
elec.; (B) 60
o
elec.
I179=-3000 I129=0
; Step 4: (A) 180
o
elec.; (B) 0
o
elec.
I179=-3000 I129=3000
; Step 5: (A) 120
o
elec.; (B) -60
o
elec.
I179=0 I129=3000
; Step 6: (A) 60
o
elec.; (B) -120
o
elec.
I179=3000 I129=0
; Step 1: (A) 0
o
elec.; (B) 180
o
elec.
Case (A) is the proper result for all direct PWM setups (Ixx82>0), regardless of the setting of Ixx72. It is
the proper result for sine-wave output setups (Ixx82=0) with Ixx72<1024. Case (B) is the proper result
for sine-wave output setups (Ixx82=0) with Ixx72>1024.
the proper result for sine-wave output setups (Ixx82=0) with Ixx72<1024. Case (B) is the proper result
for sine-wave output setups (Ixx82=0) with Ixx72>1024.
These commands will force about 1/10 of maximum current into phases to drive the motor to known
positions in the phase cycle. Remember to clear the offsets when you are finished with this test:
positions in the phase cycle. Remember to clear the offsets when you are finished with this test:
I179=0 I129=0
Direction-Balance Fine-Phasing Test
The stepper motor phasing test will establish a phase reference typically to within 1 or 2 degrees. This is
adequate for many purposes, but for complete optimization of the motor phase reference, it is necessary to
perform another test, described below. This test finds the best phase reference by making sure that key
performance measures are the same in both directions. Usually the improvement seen in performance
from this fine phasing is better smoothness, not increased torque.
adequate for many purposes, but for complete optimization of the motor phase reference, it is necessary to
perform another test, described below. This test finds the best phase reference by making sure that key
performance measures are the same in both directions. Usually the improvement seen in performance
from this fine phasing is better smoothness, not increased torque.
The use of current-loop integrator registers as explained below can be used only in direct PWM systems.
The tests can still be run on sine-wave output systems, but the measurement to be compared in both
directions is the motor velocity. This can simply be read in the position window of the PMAC Executive
Program. This measurement, which is also possible on direct PWM systems, is not quite as sensitive to
phase differences as the measurement explained below, but can still result in an improvement.
The tests can still be run on sine-wave output systems, but the measurement to be compared in both
directions is the motor velocity. This can simply be read in the position window of the PMAC Executive
Program. This measurement, which is also possible on direct PWM systems, is not quite as sensitive to
phase differences as the measurement explained below, but can still result in an improvement.
This test needs to be performed only once for a given motor. Its purpose is to establish a relationship
between the motor phase angle and an absolute sensor on the motor (e.g. resolver or incremental encoder
index pulse). Most motor manufacturers who mount feedback devices in the factory do not specify a
mounting repeatability tolerance (between motor phase angle and sensor angle) tighter than 1 or 2
degrees, so the results of this test do not necessarily carry from one motor to another of a given design.
between the motor phase angle and an absolute sensor on the motor (e.g. resolver or incremental encoder
index pulse). Most motor manufacturers who mount feedback devices in the factory do not specify a
mounting repeatability tolerance (between motor phase angle and sensor angle) tighter than 1 or 2
degrees, so the results of this test do not necessarily carry from one motor to another of a given design.