Objectives:
The objective of this experiment is to calculate the velocity and position transfer function
of armature controlled DC motor. This should establish a basis for future design of
control applications.
Step 1:
The electric circuit consists of the resistance ® and inductance (L) of the armature
winding and back emf (eb) induced in the armature winding. Armature current (ia) flows
in the circuit. Applying KVLK to the loop provides armature current, which is defined by
the equation:
b
a
a
a
e
Ri
dt
di
L
e
+
+
=
Step 2:
The armature current (ia) produces torque (
T
) as defined by equation:
a
T
i
K
T
=
Where K
t
= torque constant, N.m/A
Step 3:
The motor torque acts on the motor inertia (Jm) and viscous friction (Bm) and is related
to the speed of the motor in time domain as defined by the equation:
n
m
n
m
B
dt
d
J
T
ϖ
ϖ
+
=
Step 4:
The back emf of the motor is related to the motor speed as
m
E
b
K
e
ϖ
Where Ke = Voltage constant, V.s/rad
Step 5:
The motor position (0m) is obtained by taking the integral of the motor speed as
∫
=
dt
m
m
ϖ
θ
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 Spring '11
 grubb
 Velocity, Electric motor, Eb

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