Velocity loop
bandwidth
The velocity loop bandwidth (f
vc
) is given by the equation:
f Hz
KVP K
J
KVP
K
J
vc
T
TOT
T
TOT
(
)
*
*
.
*
*
=
≈
3
2
2
0138
π
where:
KVP
is the velocity loop proportional gain in amps/(rad/sec)
K
T
is the 0-peak line-line motor torque constant in lb-in/amp
J
TOT
is the total inertia (motor total + load total) in lb-in-sec
2
.
(Any consistent set of units for K
T
, J
TOT
, such as MKS, that
yields K
T
/J
TOT
in rad/sec
2
/amp will work)
The motor torque constant is the value of K
T
peak published in
the Pacific Scientific Motion Control Solutions catalog.
Note:
f
vc
is the unity gain open-loop crossover frequency of the
idealized rigid single mass system. See hardware specifications
for maximum f
vc
value.
Default
bandwidths
When creating a new program, the selections made set
KVP
to
achieve the velocity loop bandwidths shown below, assuming
there is no load on the motor shaft and the motor has no
mechanical brake or other secondary devices installed.
Note:
The bandwidth depends upon the user’s selection for
desired system response:
Gentle
Medium
Stiff
f
vc
Velocity Loop
Bandwidth (Hz)
25
75
200
4 - 2
MA950
