Motor-Amplifier; Dmc-14X5/6 - Galil Motion Control DMC-14 5 Series Manual

Motor-Amplifier

The motor amplifier may be configured in three modes:
1. Voltage Drive
2. Current Drive
3. Velocity Loop
The operation and modeling in the three modes is as follows:
Voltage Drive
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
Then the corresponding time constants are
T m = 0.04 sec
and
T e = 0.002 sec
Assuming that the amplifier gain is Kv = 4, the resulting transfer function is
P/V = 40/[s(0.04s+1)(0.002s+1)]
Current Drive
The current drive generates a current I, which is proportional to the input voltage, V, with a gain of Ka.
The resulting transfer function in this case is
P/V = K a K t / Js 2

DMC-14x5/6

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[
(
= + 1
K K S ST
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]
]
)( )
+
ST 1
e
Chapter 10 Theory of Operation 141
i