Operation
48
Atlas
®
Digital Amplifier Complete Technical Reference
4
4.5.2.1
Reading Current Loop Values
To facilitate tuning there are a number of current loop values that can be read back as well as traced. To read back
these values the command
GetCurrentLoopValue
is used. See
Section 4.11.1.3, “Trace Variables”
to specify these
values for trace during automatic trace capture.
The variables within the current loop that can be read or traced when the control loop mode is set to individual phase
control are summarized in the following table. Refer to
when viewing this table.
4.5.2.2
Individual Phase Control with Step Motors
The Atlas unit’s individual phase control mode is designed to work with both 3-phase brushless DC motors and 2-
phase step motors. When operating step motors in this mode (see
Section 4.9, “Step Motor Control”
for more
information on operations with step motors), the basic method is identical. The same three current loop parameters
described in
Section 4.5.2, “Individual Phase Control”
are set, and the readable parameters are also the same.
4.5.2.3
Individual Phase Control in Voltage Mode
If Atlas is operated in individual phase control mode with the current loop disabled, then after commutation
(Brushless DC motors) or microstep signal generation (step motors) the phase-specific commands are output directly
to the power stage with no current loop performed.
For example, if the incoming torque command provided by the external controller is 25% full scale, then for an Atlas
that is operating with a bus voltage of 24V, the average voltage presented at the motor coil will be 25% of 24V or 6V.
Variable Name
Function
Phase A Reference, Phase B Reference
Brushless DC & microstepping motor:
These registers hold the commanded (reference) currents for
the phase A and phase B coils.
DC Brush motor:
Phase A Current holds the commanded (reference) current for
the motor.
Phase A Current, Phase B Current, Phase C Current
Brushless DC:
These registers hold the measured actual currents for the phase
A, phase B, and phase C coils.
Step motor:
These registers hold the measured currents for the phase A, and
phase B coils.
DC Brush motor:
Phase A Current holds the measured current for the motor.
Phase A Error, Phase B Error
Brushless DC & microstepping motor:
These registers hold the difference between the current loop
reference and the measured current value (Phase A Current,
Phase B Current).
DC Brush motor:
The Phase A Error register holds the difference between the
current reference and the measured current value (Phase A
Current).
Phase A Integrator Sum, Phase B Integrator Sum
Brushless DC & microstepping motor:
These registers hold the sum of the integrator for the phase A
and B current loops.
DC Brush motor:
Phase A Integrator Sum holds the sum of the integrator for the
current loop
Phase A Output, Phase B Output
Brushless DC & microstepping motor:
These registers hold the output command for the phase A and B
current loop.
DC Brush motor:
Phase A Output holds the output command for the current loop
