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CONTROLLER
X
R
Σ
C
Figure 10.4 - Functional Elements of a Servo Control System
The motor amplifier may be configured in three modes:
The operation and modeling in the three modes is as follows:
The amplifier is a voltage source with a gain of Kv [V/V]. The transfer function relating the input
voltage, V, to the motor position, P, is
P V
where
T
and
T
and the motor parameters and units are
K t
R
J
L
When the motor parameters are given in English units, it is necessary to convert the quantities to MKS
units. For example, consider a motor with the parameters:
K t = 14.16 oz - in/A = 0.1 Nm/A
R = 2 Ω
J = 0.0283 oz-in-s 2 = 2.10 -4 kg . m 2
L = 0.004H
DMC-1000
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Y
DIGITAL
ZOH
FILTER
ENCODER
Motor-Amplifier
1. Voltage Drive
2. Current Drive
3. Velocity Loop
Voltage Drive
[
(
=
+
K
K S ST
1
V
t
m
=
2
RJ K
[s]
m
t
=
L R
[s]
e
Torque constant [Nm/A]
Armature Resistance Ω
Combined inertia of motor and load [kg.m 2 ]
Armature Inductance [H]
V
DAC
]
)(
)
+
ST
1
e
Chapter 10 Theory of Operation • 135
E
AMP
MOTOR
P
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