Operation
50
Atlas
®
Digital Amplifier Complete Technical Reference
4
To set these parameters the command
SetFOC
is used. To read back these parameters the command
GetFOC
is used.
The values set using this command are buffered and are activated using the SPI header. See
for details.
4.5.3.1
Reading FOC Loop Values
To facilitate tuning there are a number of FOC loop values that can be read back as well as traced. To read back these
values the command
GetFOCValue
is used. See
to specify these values during
automatic trace capture.
for an overview of the FOC loop. The variables within the FOC loop that can be read or traced
are summarized as follows:
4.5.3.2
FOC with Step Motors
The Atlas unit’s field oriented control algorithm 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 FOC parameters described
in
Section 4.5.3, “Field Oriented Control”
are set, and the readable parameters are also the same.
4.5.3.3
FOC in Voltage Mode
If Atlas is operated in FOC 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.
However unlike the independent phase control mode, a space vector modulation scheme is used to generate the PWM
signals and control the switching bridge. Space vector modulation is recommended for most applications because it
provides a larger effective range of voltage drive capacity.
for more information on power stage operations.
It is the responsibility of the user to determine control parameters that are suitable for use in a given application.
Variable Name
Function
q Reference, d Reference
Are the commanded values input into the q and d loops. Note
that d is always set to 0 (zero).
q Feedback, d Feedback
Are the measured values for the q (quadrature) and d (direct)
force after re-referencing from the actual measured current in
the phase A, phase B coils.
q Error, d Error
Are the differences, for the q loop and the d loop, between the
loop reference and the loop measured value.
q Integrator Sum, d Integrator Sum
Are the integrator sums for the d and q loops.
q Output, d Output
Are the output commands of the q and the d loops.
FOC
Output, FOC
Output
Are the FOC outputs in the
,
reference frame.
Phase A Actual Current, Phase B Actual Current
Are the measured currents for the phase A and phase B coils.
