Page 114 - Concise Encyclopedia of Robotics

Error Signal
DF response curve
North
Robot
To beacon East

South
Error-sensing circuit

the robot turns off course, the beacon is no longer in the null, and a signal
is picked up by the RDF receiver. This signal goes to the robot controller,
which steers the robot to the left and right until the beacon signal once
again falls into the null.
See also DIRECTION FINDING and SERVOMECHANISM.
ERROR SIGNAL
An error signal is a voltage generated by an error-sensing circuit. This signal
occurs whenever the output of the device differs from a reference value.
Error signals can be used in purely electronic systems, and also in electro-
mechanical systems.
In the RDF device described under ERROR-SENSING CIRCUIT, the output
might look like the polar-coordinate graph shown in the illustration. If
the robot is pointed on course, the error signal is zero. If it is off course,
either to the left or the right, a positive error signal voltage is generated,
as shown in the accompanying rectangular-coordinate graph. The voltage
depends on how far off course the robot is headed. In general, as the
heading error increases, so does the error-signal strength.

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