Lenze SX-1 - KV-factor and Gain Break points in general

7.1.2
KV-factor and Gain Break points in general
The aim of each positioning movement is:
1. To have as small a difference between the Required and Actual positions as possible,
e. to reach final position as quickly as possible.
2. To reach the required position with high accuracy.
You can achieve both aims by using a high value of KV.
Co nsider:
Vref= KV.(W~X)j
Vref = Velocity demanded
KV = Position Loop Gain
W = Required Position
X = Actual Position
W - X = Difference Required/Actual Position = Following Error
The SX-l numerical control produces an analog voltage output which is the product of the
following error and the KV factor. This output is used to produce movement ot the servo
drive in such a way as to reduce the following error to zero.
Vref=KV•ds
ds = Following Error
Speed then increases linearly with time:
w = angular speed
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NOTE:
1. The higher the KV factor, the smaller the tollowing error required to produce a given
speed of the drive (drive responds quickly).
2. When even a small change in the actual position occurs, e. g. due to a disturbing force,
then a arge change in analog output is produced to resist the disturbance.
The upper limit ot the KV value is determined by the drive dynamics, and the natural
trequency ot the bad. lt the KV value is too large, then the drive becomes unstable.
A starting-point for determining KV is to assume constant accelerating torque Tmax and
resultant acceleration.
533constant
a = angular acceleration
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