Page 219 - Electrical Engineering Dictionary

lite receiving antennas and down-converter direct drive a drive in which no gear re-
receivers. ducer is used.

F(dB) = 10 log (SNR in /SNR out )
10 direct drive robot a mechanical arm
where all or part of the active arm joints are
actuated with the direct drive. Due to the fact
direct burial (1) the practice of burying a
that many actuators are best suited to rela-
specially-armored power or communications
tively high speeds and low torques, a speed
cable in a ditch without the use of a surround-
reduction system is required. Gears are the
ing conduit.
most common elements used for reduction.
(2) a term applied to any cable which is
A robot with a gear mechanism is called a
meant for direct burial.
geared robot. Gears are located at different
joints; therefore, usually geared robots have
direct control bottom, first, control layer
a transmission system, which is needed to
of a multilayer controller, directly responsi-
transfer the motion from the actuator to the
bleforadjustingthemanipulatedinputstothe
joint.
controlled process; typical example of direct
control is the regulation layer of an industrial
direct dynamics the direct dynamics
control system, where the manipulated inputs
problem consists of determining the joint
are used to make the controlled variables fol-
generalized accelerations ¨q(t) assuming that
low the desired set point values.
joint generalized forces τ(k), joint positions
q(t), and joint velocities ˙q(t) are known. So-
direct control layer See direct control.
lution of the direct dynamics leads to the dy-
direct converter a frequency converter namicsimulationwhichisdefinedasfollows:
that converts an RF signal to a baseband sig- for a given set of joint generalized forces and
nal directly in receivers. It converts a base- initial values of the joint positions and veloci-
band signal to an RF signal directly in trans- ties integrate the equations of motion in order
mitters. to find a set of joint accelerations, velocities,
and positions. The dynamics simulation is
direct current machine a DC machine very useful for manipulator simulation.
is an electromechanical dynamo that either
converts direct current electrical power into direct fuzzy control the use of fuzzy con-
mechanical power (DC motor), or converts trol directly in the inner control loop of a
mechanical power into direct current electri- feedback control system.
cal power (DC generator). Some DC ma-
chines are designed to perform either of these direct kinematics direct kinematics (or
functions, depending on the energy source to forward kinematics) for an arbitrary manip-
the dynamo. ulator and given the joint variables vector
T
q(t) = [q 1 (t), q 2 (t),...,q n (t)] and the ge-
direct current motor a rotation machine ometriclinkparametersfindsthepositionand
energized by DC electrical energy and used orientation of the end-effector of the manip-
to convert electrical energy to mechanical en- ulator with respect to a reference coordinate
ergy. frame. The direct kinematics problem can
be solved by successive multiplication of the
direct digital synthesizer an oscillator D-H transformation matrices from the base
that generates sinusoidal wave by digital cal- of the manipulator towards its end-effector.
culation and digital to analog conversion. It More precisely the kinematics can be repre-
can generate an arbitrary frequency signal in sented mathematically as a continuous map
a fine channel step. assigning to every joint position (configu-

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2000 by CRC Press LLC