Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
Setting Up Turbo PMAC-Based Commutation and/or Current Loop
107
Establishing Basic Current Loop Operation
Once the proper operation of the Turbo PMAC PWM output circuits, the Turbo PMAC ADC input circuits,
and all of the drive and motor circuitry between them have been established, close the current loop.
and all of the drive and motor circuitry between them have been established, close the current loop.
The Turbo Setup program has both auto-tuning and interactive tuning procedures for the digital current
loop. Most people will use one or both of these procedures to tune the current loop. These procedures
can confirm the proper polarity of the current loop readings also. However, issue the commands
manually as explained in this section.
loop. Most people will use one or both of these procedures to tune the current loop. These procedures
can confirm the proper polarity of the current loop readings also. However, issue the commands
manually as explained in this section.
Purpose
The purpose of these next tests is to set the current loop gains for quick but stable current response. This
is done by giving the motor a current command and observing the current response.
is done by giving the motor a current command and observing the current response.
The key to testing the current loop is the use of Turbo PMAC’s O commands, which close the current
loops while leaving open the position and velocity loops. The magnitude of the O-command value is that
of the torque-producing quadrature current command, expressed as a percentage of Ixx69; Ixx77 controls
the magnitude of the direct current command.
loops while leaving open the position and velocity loops. The magnitude of the O-command value is that
of the torque-producing quadrature current command, expressed as a percentage of Ixx69; Ixx77 controls
the magnitude of the direct current command.
It is safest not to create any movement while testing the current loop; this can be done by commanding
only direct current, accomplished by setting Ixx77, then issuing an O0 command.
only direct current, accomplished by setting Ixx77, then issuing an O0 command.
Digital Current Loop Gains
Ixx61, Ixx62, and Ixx76 are the gains of the PI (proportional-integral) current loop. They are used for
both phases of a multi-phase motor. Ixx61 is the integral gain term. There are two proportional gain
terms: Ixx62 is the forward-path proportional gain, and Ixx76 is the back-path proportional gain. Ixx62 is
multiplied by the current error (commanded minus actual) and the result is added into the output
command. Ixx76 is multiplied by the actual current value and subtracted from the output command. All
three gain terms have a range of 0.0 to 2.0, with 23-bit resolution for positive values.
both phases of a multi-phase motor. Ixx61 is the integral gain term. There are two proportional gain
terms: Ixx62 is the forward-path proportional gain, and Ixx76 is the back-path proportional gain. Ixx62 is
multiplied by the current error (commanded minus actual) and the result is added into the output
command. Ixx76 is multiplied by the actual current value and subtracted from the output command. All
three gain terms have a range of 0.0 to 2.0, with 23-bit resolution for positive values.
PMAC2 Digital Current Loop
Ix66
K
pf
K
i
1 - Z
-1
K
pb
Voltage
Command
(V
d
or V
q
)
-1.0 < U < 1.0
U
PFM
Scale
Factor
+
+
+
Forward Path
Proportional
Gain
Integral
Gain
Back Path
Proportional
Gain
+
Measured
Current
(I
d
or I
q
)
-
+
Current
Command
(I
d
or I
q
)
Prescaled to
range
-1.0 < I < 1.0
K
pb
= Ix76 x 4 (0.0 < Ix76 < 1.0)
K
pf
= Ix62 x 4 (0.0 < Ix62 < 1.0)
K
i
= Ix61 x 4 (0.0 < Ix61 < 1.0)
Usually only one of Ixx62 or Ixx76 is used on a given motor; the other gain is set to 0.0. It is more
common to use Ixx61, the forward-path gain, because it provides greater responsiveness and bandwidth.
If Ixx76 is used instead of Ixx62, only the Ixx61 integral gain term directly connects the current command
to the output, and its integration effect filters the command, reducing responsiveness.
common to use Ixx61, the forward-path gain, because it provides greater responsiveness and bandwidth.
If Ixx76 is used instead of Ixx62, only the Ixx61 integral gain term directly connects the current command
to the output, and its integration effect filters the command, reducing responsiveness.