Page 332 - Concise Encyclopedia of Robotics

Three Laws of Robotics
voltage is directly proportional to the temperature difference within a lim-
ited range. The function of voltage in terms of temperature difference can
be programmed into a robot controller,allowing the machine to determine
the temperature difference by measuring the voltage. Compare THERMISTOR.
See also TEMPERATURE SENSING.
THREE LAWS OF ROBOTICS
See ASIMOV’S THREE LAWS.
TIME-OF-FLIGHT DISTANCE MEASUREMENT
Time-of-flight distance measurement, also called time-of-flight ranging, is a
common method by which a robot can determine the straight-line distance be-
tween itself and an object.A wave or signal pulse,which travels at a known,con-
stant speed, is transmitted from the robot. This signal reflects from the
object,and a small amount of energy returns to the robot.The distance to the
object is calculated on the basis of the time delay between the transmission
of the original signal pulse and the reception of the return signal, or echo.
Suppose the speed of the signal disturbance, in meters per second, is
denoted c, and the time delay, in seconds, is denoted t. Then the distance
d to the object under consideration, assuming the signal travels through
the same medium throughout the span between the robot and the object,
is given by this formula:
ct
d
2
Examples of systems that use time-of-flight ranging are ladar, radar, and
sonar. These use laser beams, microwave radio signals, and acoustic
waves, respectively. The speed of laser beams or radio waves in Earth’s
8
atmosphere is approximately 300 million (3.00 10 ) m/s; the speed of
acoustic waves in air at sea level is approximately 335 m/s.
See also LADAR, RADAR, and SONAR.
TIME SHIFTING
In communications, time shifting refers to any system in which there is a
significant delay between the transmission of a signal at the source and its
receipt or utilization at the destination.The term applies especially to com-
puter networks and remotely controlled robotic systems. Time shifting
does not allow a computer or robot and the operator to converse, but
commands and telemetry can be conveyed.
Time shifting is best suited for the transmission of data at high speed,
and in large blocks. This is the case, for example, when monitoring condi-
tions at a far-off space probe. In computer systems and networks, time

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