AN-1090 데이터 시트보기 (PDF) - International Rectifier
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AN-1090 Datasheet PDF : 15 Pages
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15
Speed Controller
The speed controller is the most outer-loop controller in a cascaded speed drive system. Figure 6
shows the cascaded control dynamics of the speed control loop. In practice, the inner current
loop has much higher control bandwidth than the speed controller, therefore for speed control
dynamic purpose, the inner current loop can be ignored as shown in Figure 7. Parameter M
(Figure 7) relates command current digital counts to actual current in Amps. The motor
mechanical dynamic is a first order function with mechanical time constant equals to J/F
(Inertia/Friction). Pole-zero cancellation technique (outlined in current regulator tuning section)
can be used to simplify tuning of the speed controller proportional and integral gains (KpSreg,
KxSreg). In practice, information on mechanical friction (F) is difficult to obtain. In addition,
temperature dependent friction characteristic is present in some applications. Therefore, manual
speed tuning may be required to achieve optimal speed response. Some applications cannot
tolerate high speed regulator bandwidth due to mechanical resonance present in mechanical
arrangement.
Speed
Regulator
KxSreg
+
1
-
S
Speed
+
Command
-
KpSreg
Filter
SpdFiltBW
+
+
-
+
Speed
Estimator
KxIreg
Controller
Current
Regulator
11
+
A
S
+
KpIreg
B
Motor
V
1
R (1 + S T)
Load
-
I
1
Kt
1/J
+
S
-
F
Speed
J - Inertia
F - Friction
Kt - Torque constant
A, B, C - Conversion Gains
Figure 6. Cascaded Control Dynamics
Speed
Command
Speed
Regulator
KxSreg
+
-
+
-
KpSreg
controller
1
+
S
+
Motor
Load
-
+
1
M
Kt
1/J
-
S
J - Inertia
F
F - Friction
Kt - Torque constant
C, M - Conversion Gains
Filter
C
SpdFiltBW
Figure 7. Simplified Speed Control Loop Dynamics
Speed
www.irf.com
AN-1090
6
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