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Functions
(
continued)
Software
Unity Pro software
Small/Medium/Large/Extra Large
Programmable process control
Process control in machines
Unity Pro contains
CONT_CTL,
a library of 36 function blocks used to create control
loops for machine control.
All requirements for closed loop control functions in machines are adequately met by
Modicon M340, Premium and Quantum platforms thanks to the wealth of functions in
the library and the flexibility with which function blocks can be linked together
through programming. This solution therefore eliminates the need for external
controllers and simplifies the overall control architecture of the machine, as well as
its design, roll-out and operation.
The EFs or EFBs can be used in all Unity Pro languages (LD, ST, IL and FBD). FBD
is particularly suitable for accessing control processing operations in Unity Pro
through its wizard for entering and viewing parameters and function block variables.
CONT_CTL library functions
The library consists of five function families:
b
Input data conditioning
b
Controllers
b
Mathematical functions
b
Process value processing
b
Output value processing
Input data conditioning
DTIME
Pure time delay
INTEGRATOR
Integrator with limiting
LAG_FILTER
First order time lag
LDLG
Lead/lag function with smoothing
LEAD
Lead function with smoothing
MFLOW
Mass flow calculation based on the measurement of differential
pressure or flow speed with pressure and temperature compensation
QDTIME
Dead time term
SCALING
Scaling
TOTALIZER
Integrator (typically of flow) until a limit (typically a volume) is
reached, with automatic reset
VEL_LIM
Velocity limiter, with manipulated variable limiting
Controllers
PI_B
Basic PI controller: PI algorithm with a mixed structure
(
series/parallel)
PIDFF
Complete PID controller: PID algorithm with a parallel or mixed
structure (series/parallel)
AUTOTUNE
Automatic tuner setting for the PIDFF (complete PID) controller or
the PI_B (simple PI) controller
v
Identification using Ziegler Nichols type method
v
Modelling based on first order process
v
Building of control parameters with criterion for prioritizing
either the reaction time to disturbance (dynamic) or the stability of
the process
IMC
Model-based controller. The model is a first order model with
delay. This corrector is useful:
v
When there are serious delays compared with the main time
constant of the process; this scenario cannot be satisfactorily
resolved by standard PID process control
v
For regulating a non-linear process
IMC can handle any stable and aperiodic process of any order.
SAMPLETM
Control of controller startup and sampling
STEP2
Simple two-position controller
STEP3
Three-position controller for temperature regulation
Mathematical functions
COMP_DB
Comparison of two values, with dead zone and hysteresis
K_SQRT
Square root, with weighting and threshold, useful for linearization
of flow measurements
MULDIV_W
Weighted multiplication/division of 3 numerical values
SUM_W
Weighted summing of 3 numerical values
CONT_CTL, programmable process control integrated in
Unity Pro
AUTOTUNE
PV
SP
RCPY
START
PREV
PARA
TR_I
TR_S
PV_O
SP_O
PARA_C
TRI
TRS
INFO
STATUS
TT18_PV
TT18_SP
TC18_OUT
TC18_START
TC18_PREV
TC_PARA
TC18_PARA
TC18_OUT
1
TC2_OUT
TC2_OUT
TC18_OUT
PV
SP
PARA
TR_I
TR_S
PIDFF
FF
RCPY
MAN_AUTO
OUT
OUT
OUTD
MA_O
INFO
STATUT
TC2_OUT
MS
TC18_OUT
IN
PARA
TR_I
TR_S
FORC
MA_FORC
MAN_AUTO
OUT
OUT
OUTD
MA_O
STATUT
Example: PID controller with MS manual control
Selection guide:
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