CONTREX CX-1200 - Manual (Page 142)

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POSITION LOOP P1/2
The Position Loop screen includes parameters for the loop-type selection, the PID parameters for the
Position Loop (Kp, Ki, Kd), and four tuning monitor parameters
Cntrl Loop
Control Loop (MP-49) displays the present operating mode of the CX-1200. Only one type of loop can be active at a
time. These modes are automatically selected depending on the present system State (MP-50).
3 = Psn Hld (H-Stop Position Loop)
2 = Position Loop
1 = Velocity Loop
0 = Open Loop
Kp PL
Kp PL (CP-325) is the proportional gain constant for the PID position loop. Increasing Kp PL (CP-325) will have a
quicker the response and a smaller position error. However, a value that is too large could result in overshoot and
instability. You can eliminate most or all of the error in the position loop with the proportional term (Kp PL). Use an
integral only if Kp PL (CP-325) alone can not eliminate the error to your specification.
Ki PL
Ki PL (CP-326) is the integral constant for the PID position loop. Integral action provides for zero steady state error.
Increase Ki PL (CP-326) for a faster convergence to zero error. However, a value that is too large will cause instability.
Use Ki PL (CP-326) first to eliminate the error to your specification. If this produces unacceptable results, then
decrease Kp PL (CP-325) and introduce the integral by gradually increasing Ki PL (CP-326).
Kd PL
Kd PL (CP-327) is the derivative constant for the PID position loop. Derivative action damps out overshoots, however,
its effect is limited and is highly dependent on Kp PL (CP- 325), Ki PL (CP- 326) and the given process dynamics. A
value that is too large can cause instability.
FeedFwd
Feedforward (MP-35) displays the estimated voltage command to the drive required achieve the commanded RampedRef
(MP-31). It is usually the major portion of the CO Volts (MP-37) signal.
Intgrl
Integral (MP-34) displays the value of the integral term (i.e., integrated error times the Ki constant) of the PID compen-
sator. Intgrl (MP-34) is displayed in Volts. Intgrl (MP-34) is a conditioned error signal that serves to adjust the CO Volts
(MP-37) to help achieve the desired speed. It is part of the PID error correction algorithm.
Trim Out
Trim Out (MP-36) displays the value of the output of the PID compensator. Trim Out is displayed in Volts. Trim Out is
the sum of the conditioned error signals that, combined with the FeedFwd (MP-35), become the CO Volts (MP-37). Trim
Out is the combination of all three terms of the PID error correction algorithm.
CO Volts
Control Output Volts (MP-37) displays the present value, in volts, of the Control Output (CO_Sig) signal to the drive.
It is the combination of FeedFwd (MP-35) plus Trim Out (MP-36).
PosnErr
Position Error (MP-33) displays the value, in engineering units, of the accumulated position error between the lead
(FI1) and the feedback (FI2) input signals. The placement of the decimal point is the same as the placement of the
decimal point in EU FI2 (CP-268).