S
PI
PI
3-phase
Inverter
Rotor Flux
Angle
Calculator
PI
SV
PWM
D,Q
D,Q
d,q
d,q
d,q
a,b,c
PWM1/2
PWM3/4
PWM5/6
-
+
W
ref
W
r
+
+
Inv. Park
Park Tr.
Clarke Tr.
-
-
ACI
Motor
ID
ref
IQ
ref
S
S
V
Q
V
D
Vq
Vd
W
r
I
Q
I
D
i
a
i
b
q
r
W
r
I
q
I
d
www.ti.com
Software Tools
Once a rich set of library modules is available with a well-defined and proven interconnect methodology,
systems can be realized fairly quickly. The logical extension is that various “what-if” scenarios of system
topologies and/or configurations can be explored relatively easily and with little overhead. As a more basic
or fundamental need, this same ease of module connection allows a system designer to have a number of
incremental build levels, ranging from a rudimentary system (3-4 modules) used to check out key life
signs, to a fully featured final system with a large number of connected modules. This is analogous to the
commissioning steps or process which is typical in large engineering projects. This approach to system
software commissioning is invaluable during the system integration phase and can greatly reduce the time
and effort required.
2.3.1
Consistency Between Software Modules and Control Block Diagrams
It is well known that systems and control engineers like to visualize systems or control strategies in the
form of signal flow block diagrams. It makes good sense to separate main functions and to show how
each is interrelated by explicit connection to other functions. Each function should be self-contained, and
its boundaries or interface clearly delineated. A digital motor control system is a good example of this
interrelation of functions.
Figure 2
shows a typical signal flow block diagram of an AC induction motor
controlled by a field-oriented control strategy. This is a useful representation, and it is found in many
classical texts on motor control. However, several limitations are evident when attempting to realize this
diagram in software form.
Figure 2. ACI Sensored FOC - System Block Diagram
It is not usually clear how software variables are related to the signal parameters on the diagram, nor
where in the software these parameters can be found and accessed. Moreover, the boundary between
software and hardware is blurred (i.e., where the software controls the on-chip peripheral and where the
peripheral output pins control the external hardware, such as the PWM-to-inverter interface). By adopting
a modular strategy and enforcing some clear definitions, the classic block diagram shown in
Figure 2
can
be rearranged and redrawn to reveal a great amount of information about the actual software which is
used to implement such a system. This new style of system representation can be seen in
Figure 3
. The
advantages and features of such a representation will be expanded upon in later sections, but a summary
of key points are given here:
•
The system block diagram has a clear one-to-one mapping to the modular system software.
•
Each module graphic or block represents a self-contained software function or object of the same
name.
•
Input and output terminals of each module correspond exactly to global variables within the software
function.
7
SPRUGI6 – September 2010
TMS320C2000 Motor Control Primer
Submit Documentation Feedback
Copyright © 2010, Texas Instruments Incorporated
