Pictorial Handbook of Technical Devices by: Otto B. Schwarz and ...

‘i MAGNETICS & ELECTRQNIW
C--Electrical
‘7-SERVQMECWNISMS. Only the position servo will be explained. A
servomechanism positions an object with respect to ar inpl!t, and the
operation depends on the difference of the position of the object and the
desired position. A motor in this set-up tries to reduce this difference to
zero. Servomechanisms belong to the feedback control system group.
a-Blockdiagram oi a simple position servo. The pario comprising the
system are shown, as well as the flow path. The input command is given to
a potentiometer. Depending on the position of the arm of this potentiometer
a given reference voltage will result, shown as “L.” The second
potentiometer also has an output. The difference between these two
voltages is an error voltage, “e:” u,nless (r - b) is zero, then error voltage
“e” goes into the amplifier. The amplifier amplifies this v&tage by driving
the motor. The motor, through its gearing drives the second (feedback)
potentiometer in a direction to make the error signal “e” zero.
b-A mixed schematic diagram of the block diagram. Input to comn,and
potentiometer iS a handcrank, as used in school experiments. Normally it
will come from some other gear train.
c-Electric schematic diagram for the above unit.