Lenze PLC Designer PLC Designer (R2-x) - Manual (Page 669)

L-force | PLC Designer
PLC Designer Libraries
DMS 3.2 EN 02/2011 TD29 667
Inputs of the function block:
Variable Data type Description
ACTUAL REAL Current value of the controlled variable
SET_POINT REAL Desired value, command variable
KP REAL Proportionality coefficient, unity gain of the P-part
TN REAL Reset time, reciprocal unity gain of the I-part;
given in seconds, e.g. "0.5" for 500 msec
TV REAL Derivative action time, unity gain of the D-part in seconds, e.g. "0.5" for
500 msec
Y_MANUAL REAL Defines output value Y in case of MANUAL = TRUE
Y_OFFSET REAL Offset for the manipulated variable Y
Y_MIN, Y_MAX REAL Lower resp. upper limit for the manipulated variable Y. If Y exceeds
these limits, output LIMITS_ACTIVE will be set to TRUE and Y will be
kept within the prescribed range. This control will only work if
Y_MIN
MANUAL BOOL If TRUE, manual operation will be active, i.e. the manipulated value will
be defined by Y_MANUAL.
RESET BOOL TRUE resets the controller; during reinitialization Y = Y_OFFSET.
Outputs of the function block:
Variable Data type Description
Y REAL Manipulated value, calculated by the function block (see below)
LIMITS_ACTIVE BOOL TRUE indicates that Y has exceeded the given limits (Y_MIN, Y_MAX).
OVERFLOW BOOL TRUE indicates an overflow (see below)
Y_OFFSET, Y_MIN und Y_MAX serve for transformation of the manipulated variable
within a prescribed range.
MANUAL can be used to switch to manual operation; RESET can be used to re-initialize
the controller..
In normal operation (MANUAL = RESET = LIMITS_ACTIVE = FALSE) the controller
calculates the controller error e as difference from SET_POINT – ACTUAL, generates
the derivation with respect to time δe/δt and stores these values internally.
The output, i.e. the manipulated variable Y unlike the PD controller contains an
additional integral part and is calculated as follows:
Y = KP ⋅ (Δ + 1/TN ∫edt + TV δΔ/δt) + Y_OFFSET