AN1625 APPLICATION NOTE

28/39

(

for a given speed, the speed reference voltage to apply is:

a good compromise between static performance, dynamic performance, stability and torque ripple:

2.15.1 Static performance - Speed Regulation vs. Resistant Torque:

speed. To minimize the resistant torque effect the term (D + G

possible.

Figure 31 shows how the speed changes with the load torque, and percentage regulation error.

Due to the op-amp output voltage saturation, beyond a certain load torque value the system cannot produce

further torque, then the motor speed drastically decreases.

1 .10

3

0.01

0.1

1

10

100

50

25

0

25

50

f [Hz]

fc

0

1 . 10

3

0.01

0.1

1

10

100

135

90

45

f [Hz]

fc

180

ω

M

V

spee d

1

G

op

a mp

–

1s

τ

I

+

-------------------------

+



 G

1

k

T

T

b

–

⋅⋅

⋅

D1 s

τ

M

⋅

–

G

1

k

T

G

op

amp

–

1s

τ

I

+

-------------------------

⋅⋅

⋅

++

-----------------------------------------------------------------------------------------------------------

=

V

speed

ω

M

–

G

1

k

T

G

op

a mp

–

⋅⋅

⋅

+

() T

b

+

⋅

1G

op

amp

–

+

() G

1

k

T

⋅⋅

------------------------------------------------------------------------------------------------------------

=