M51971FP Mitsubishi, M51971FP Datasheet - Page 11

• Manufacturer Part Number: M51971FP
• Description: MOTOR SPEED CONTROL
• Manufacturer: Mitsubishi

Hint for designing a stabilized speed control
system
(Method for determining the filter constants (C
pin
The filter constants at pin
system stability.
1. Transfer Function of the Motor Speed Control
The motor speed control system is a negative feedback system
including a control circuit and a motor.
As the condition necessary for stable negative feedback, the phase
must be generally 180˚ or less in the frequency area where the
gain of open-loop transfer function (G
2. Transfer Function of Motor
If the motor armature current and angular velocity are assumed to
be la and
If the number of poles in the tacho-generator is assumed to be P,
the relation of
frequency
motor transfer function (transfer function including motor and
tacho-generator) G
follows:
System
8
Where: T
Where:
G
)
T
M
g
(S) =
= K
Control circuit
- G
v, respectively, the following equation is established.
K
T •
J : Inertia moment of Motor and load
D : Coefficient of viscosity friction
K
C
g
and motor angular velocity
T
M
M
(S)
: Torque generated in the motor
: Proportional constant between the torque genera-
=
l
l
ted in the motor and the armature current
= P
=
a
a
= (SJ+D)
M
P
Motor speed control system
=
=
D
J
(S) takes a single-pole transfer function as
D
•
•
D
K
1 +
T
•
• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
v exists between tacho-generator angular
(1+S
K
P
M
• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
•
8
S
•
M
K
T
•
must be determined to satisfy the
D
J
v
• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
)
• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
C
• • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
(S)
•
Motor
G
G
M
M
v and, therefore, the
(S)
(S)) is 1 or more.
F1
, C
F2
and R
F
) at
(2)
(3)
(4)
(5)
(1)
3. Transfer Function of Control Circuit Using the
If input information is assumed to be given continuously (the tacho-
generator frequency is assumed to be infinitely high), the transfer
function from the input at pin
Where : T
If the gain of the circuit connected to the back of pin
M51971 is assumed to be K
entire circuit is as follows:
G
C
M51971
(S) = K
G
C(M51971)
F2
F1
l
l
CP
8
8
R
R
MITSUBISHI <CONTROL / DRIVER IC>
C
d
F •
F •
x
C
: Timer pulse width
: Charging current at pin
: Discharging current at pin
(S)
=
F1
1
C
C
T ( I
Approximate transfer function of control circuit
T ( I
F2
F1 •
+ C
C
Approximate motor transfer function
F2
C
C
F1
8
(output voltage at pin
(input frequency at pin
F2
F1
C
8
+ C
C
+ C
+ I
MOTOR SPEED CONTROL
F2
+ I
4
F2
F1
8
CP
log
d
to the output at pin
8
d
, transfer function G
log
~ ~
)
)
1.10 x R x C
x
M51971L/FP
M
x
S(1 + S/
8
S(1 + S/
1 + S/
1 + S/
8
9
4
F2
)
F1
)
F2
F1
F2
)
9
)
• • • • • • • • • • • • •
is as follows:
• • • • • • • • • • •
C
(S) for the
9
of the
(6)
(7)