Page 125 - Electrical Engineering Dictionary

before they cross the imaging plane or pho- ities for bus access, so if more than one de-
tographic plate. vicewantsbusaccesssimultaneously, theone
with the highest priority will get it first. This
central absolute moment for random prioritization is handled by the bus arbiter.
variable x, the pth central absolute moment
p
is given by E[|x − E[x]| . See also central centrifugal switch a speed-sensitive
moment, absolute moment, expectation. switchoperatedbycentrifugalforce, mounted
on the shaft of a motor, used to perform a cir-
central limit theorem (CLT) in proba- cuitswitchingfunction. Usedinsingle-phase
bility, the theorem that the density function of induction motors to disconnect the starting
some function of n independent random vari- winding when the motor approaches operat-
ables tends towards a normal curve as n tends ing speed.
to infinity, as long as the variances of the vari-
ables are bounded: 0 <σ ≤ v i ≤ γ< ∞. centripetal force force that is present
Here σ and γ are positive constants, and v i is during the robot motion. The force depends
the variance of the ith random variable. See upon the square of the joint velocities of the
also Gaussian distribution. robot and tend to reduce the power available
from the actuators.
central moment for random variable X
the nth central moment is given by centroid (1) a region in the pattern space
to which a remarkable number of patterns be-
Z
∞
2 2
E[(X − m) ]= (x − m) f X (x)dx long.
(2) the center of a mass.
−∞
where f X (x) is the probability density func- (3) description of the center of a particle
tion of X. See also central absolute moment, beam profile.
absolute moment. See also expectation.
centroid defuzzification a defuzzifica-
central processing unit (CPU) a part tion scheme that builds the weighted sum of
of a computer that performs the actual data the peak values of fuzzy subsets with respect
processing operations and controls the whole tothefiringdegreeofeachfuzzysubset. Also
computing system. It is subdivided into two called height defuzzification.
major parts:
1. The arithmetic and logic unit (ALU), centroid method a widely used method
which performs all arithmetic, logic, and of defuzzification whereby the centroid of the
other processing operations, membership function of the fuzzy set is used
2. The control unit (CU), which sequences as the defuzzified or crisp value. It is also
the order of execution of instructions, fetches known as the center of gravity method or the
the instructions from memory, decodes the composite moments method.
instructions, and issues control signals to all
other parts of the computing system. These centroidal profile a method for charac-
control signals activate the operations per- terizing and analyzing the shape of an object
formed by the system. having a well defined boundary. The cen-
troid of the shape is first determined. Then
centralized arbitration a bus arbitration a polar (r, θ) plot of the boundary is com-
scheme in which a central bus arbiter (typ- puted relative to this origin: this plot is the
ically housed in the CPU) accepts requests centroidal profile, and has the advantage of
for and gives grants to any connected device, permitting template matching for a 2-D shape
wishing to transmit data on the bus. The con- to be performed relatively efficiently as a 1-D
nected devices typically have different prior- process.

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2000 by CRC Press LLC