Velocity Loop Tuning - Allen-Bradley 1395 Troubleshooting Manual

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Velocity Loop Tuning

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The three parameters which are used to tune the Velocity Loop include:
• Parameter 659 (KI Velocity Loop) - Integral gain term; This parameter is
scaled so that a value of 8 represents a gain of 1. This value will effect
the time recovery response to a velocity disturbance or reference change
so that, a reference change of 1 per unit will produce 1 per unit velocity
error.
• Parameter 660 (KP Velocity Loop) - Proportional gain term; This
parameter is scaled so that a value of 8 represents a gain of 1. This value
will effect the magnitude response to a velocity disturbance or reference
change, so that a reference change of 1 per unit will produce 1 per unit
velocity error.
• Parameter 661 - KF Velocity Loop - Velocity reference proportional trim
term; This parameter represents some level of attenuation to the velocity
reference used in the proportional gain calculation. 65365 is a gain of 1,
and 0 is a gain of 0. The portion of KF specified will cause the velocity
regulation to be "finished" by the integral term only, this can be seen in
the following formula:
(Pos Ref - Pos Fdbk) x KI + (Vref x KF - Vfdbk) x KP = Vel Error.
Where: Pos Ref = > Position Reference (integrated velocity reference)
Pos Fdbk = > Position Feedback (integrated velocity feedback)
Vref = > Velocity reference
Vfdbk = >Velocity Feedback
Vel Error = > Velocity error (current loop reference)
If KF = 0.7 = 45874; as velocity feedback reaches 70% of velocity
reference, KP begins to have a negative feedback effect, causing the Integral
term KI to be responsible for finishing the regulation. The net effect of this
activity is to cause an overdamped response, ie: No Overshoot.
Practical value range and initial settings:
Armature Voltage Feedback
KP = > 20 to 100 Initial setting 15
KI = >30 to 500, Initial setting 60
KF = >32767 to 65535, Initial setting 45874
D.C. Tachometer Feedback
KP = > 50 to 250, Initial setting 64
KI = >100 to 2500, Initial setting 256
KF = >32767 to 65535, Initial setting 45874
Encoder Feedback
KP = > 50 to 350, Initial setting 100
KI = >250 to 10,000, Initial setting 400
KF = >32767 to 65535, Initial setting 65535
These values and ranges represent typical values, and actual system
requirements will vary greatly depending on influences such as system
inertia, system friction, smoothness of load and "noise" on the feedback
signal. In general, the values can be set at these initial settings depending on
the feedback device, and can be tuned as follows:
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Manually Tuning the 1395 Drive 5-3