Operation
49
4
For single phase motors such as DC Brush, the PWM generator directly outputs this external controller-commanded
value to the power stage. For multi-phase motors such as brushless DC or step motor, the PWM generator outputs
this commanded value after commutation (brushless DC motors) or microstep signal generation (step motors) to the
power stage.
for more information on power stage operations.
4.5.3
Field Oriented Control
Figure 4-7:
Field Oriented
Control
Calculation
Flow
provides an overview of the calculation flow when field oriented control (FOC) is selected. Instead of
separating phases as individual phase control mode does, FOC combines them and “re-references” them to what are
known as d (direct torque) and q (quadrature torque) reference frames.
To enable field oriented control mode the command
SetCurrentControlMode
is used. The value set using this
command can be read back using
GetCurrentControlMode
.
For each control loop (d and q) three parameters are set by the user, Kp, Ki, and I limit. Two of these are gain factors
for the PI (proportional, integral) controller that comprises the heart of the FOC controller, and the other is a limit
for the integral contribution.
Atlas
®
Digital Amplifier Complete Technical Reference
2
Kpq
qOutput
AOutput
Phase
Angle
Phase A Actual Current
Phase B Actual Current
BOutput
Inverse
Park
Transform
Clarke,
Park
Transform
64
Motor
Command
qReference
qError
Kpd
dOutput
64
dReference
0 (zero)
dFeedback
qFeedback
dError
256
256
Kiq
ILimitq
q Integrator
sum
Z
-1
256
256
Kid
ILimitd
d Integrator
sum
Z
-1