Micromod Micro-DCI: 53SL6000 Single Loop Controller - Manual (Page 59)

7.1 Control Scheme Block
The control scheme block, which is the primary
functional element of the controller, provides the
capability to select and implement any one of five
control schemes. Each control scheme is the basic
building block for many control strategies. The five
control schemes are described as follows:
• SnGl - For control strategies requiring single
loop standard PID functional capabilities.
•
cASc - For control strategies requiring tighter
control of processes using dual PID loops in a
cascade configuration.
• L.LiM - For control strategies with two interde-
pendent loops where one of the two variables
must not exceed a safe low limit.
•
h.LiM - For control strategies with two interde-
pendent loops where one of the two variables
must not exceed a safe high limit.
• i n . L d - F o r a p p l i c a t i o n s t h a t r e q u i r e a n
auto/manual selector, or a manual loader, or a
two/three variable indicator with process vari-
able re-transmission capabilities
When used in conjunction with the path selections,
configuration parameters, characterizer block,
math function block, discrete logic blocks 1-4, and
I/O blocks, the five control schemes are able to
address most standard control applications. Each
of the control schemes, with the exception of the
indicator/loader (in.Ld), have a setpoint generator
with deviation calculator, a PID algorithm, and an
auto/manual output selector. The in.Ld control
scheme does not implement the setpoint generator
or the PID algorithm, as its primary functions are
signal display, selection, signal re-transmission,
and manual output control.
Control scheme information presented in this sec-
tion covers the cS.A - cS.L input signal selectors
for each of the control schemes, the control
scheme logic, the three major parts (SP generator,
PID, A/M selector) of a control scheme with SnGL,
cASc, L.LiM, and h.LiM exceptions noted, and the
in.LD control scheme.
Also covered are all control scheme related pa-
rameters and input selections.
7.2 Control Scheme Inputs
The five control schemes with their inputs are illus-
trated in Figure 7-1. In the figure, the L.LiM and
h.LiM control schemes are shown in the same illus-
tration, as these two control schemes have the
same inputs. Each control module (cn.1, cn.2) is
also identified in the figure by loop number.
The A-F inputs loaded via the cS.A - cS.F input
selectors for all five of the control schemes are
dedicated to analog signals. These analog signals
can come from the analog inputs or the math func-
tion block and may be modified with the charac-
terizer block. The h-L inputs loaded via the cS.h -
cS.L input selectors are the control signal enables
that cause the control schemes to perform specific
functions (e.g., AE for auto enable, RE for remote
enable, etc.). The control signals are digital logic
values which can come from the discrete inputs,
the math function block, or the logic blocks.
7.3 Control Scheme Control Signals
Table 7-1 describes the operations for the logic
control signals contained in control modules cn.1
and cn.2. These signals are derived from both,
digital input logic values and push button. They
control analog signal switches which in turn affect
the operations and thus the outputs of the control
modules. Also provided, is Figure 7-2, which illus-
trates the interrelationships between digital inputs,
push buttons entries, control scheme switches, and
other control signals. As shown in the figure, the
control signal priorities are oVtS having prece-
dence over Aut, and SPtS having precedence over
rMt. The control signals are depicted in hexagons.
Other analog signal switches are controlled by the
conF-cn.1(cn.2) module parameters, which are de-
picted as circled inputs; and the ProG-cS module
parameters, which are depicted as diamond inputs.
7.0 Control Scheme Block
Section 7. Control Scheme Block 53SL6000 Instruction Manual
7-1