Page 169 - Electrical Engineering Dictionary

charts. Control charts are used to aid in iden- control memory a semiconductor mem-
tification of special causes of variation, re- ory (typically RAM or ROM) used to hold
duction in product variability, and keeping the control data in a microprogrammed CPU.
good records. This data is used to control the operation of
the data path (e.g., the ALU, the data path
control horizon end time of the control busses, and the registers) in the CPU. If the
interval over which the operation of the con- control memory uses RAM, the CPU is said
trol system is considered; if the control inter- to be microprogrammable, which means that
val is infinite then the control horizon is also the CPU’s instruction set can be altered by
infinite. the user and the CPU can thus “emulate” the
instruction set of another computer. Same as
control store and micromemory.
control input See manipulated input.

control instruction machine instruction control policy See control rule.
thatcontrolstheactionsofaprocessorsuchas
setting flags to enable specific modes of oper- control problem a design problem con-
ation. Generally, control instructions do not cerned with constructing a device called the
perform computations. Sometimes control controller whose goal is to force the con-
instructions include instructions that can ef- trolled variable of the plant or process to be-
fect sequential execution of a program, such have in a desired manner. The elements of
as branch instructions. the control problem are control objective, a
model of the process to be controlled, admis-
sible controllers, and a means of evaluating
control interval time interval over which
the performance of a control strategy. See
the operation of the control system is consid-
also controller, controlled variable.
ered; control interval can be finite or infinite.
The notion of a control interval is essential
when the controlled process features various control rod an assembly of neutron-
accumulation phenomena. absorbing material, typically boron, which is
extended into the core of a nuclear reactor to
dampen the chain reaction.
control layer part of the controller re-
sponsible for performing tasks associated
with a particular aspect of the control; par- control rule decision mechanism (se-
ticular control layer results from vertical de- quence of such mechanisms), used — within
composition of the controller into a multi- the considered control layer — to specify on-
layer control structure; the layers may differ line the values of the control inputs; for ex-
in their function, or the control interval con- ample, the values of the manipulated inputs
sidered, or both. Typical examples of control in case of the direct control layer or the set-
layers would be regulation layer of a continu- point values in case of the optimizing control
ous industrial process (see direct control) and layer. Also known as control policy.
set point control layer of such process. See
also optimizing control layer. control scene initial entity, a given
“world,” which is then partitioned into the
control line in a bus, a line used in a controlled process and its (process) environ-
computer bus to administrate bus transfers. ment; control scene is the initial “world”
Examples are bus request (a device wants to which is of interest to a control engineer or a
transmit on the bus), or bus grant (the bus system analyst.
arbiter gives a device transmit access on the
bus). control store See control memory.

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2000 by CRC Press LLC