Aviation Electronics Technician 1 - Historic Naval Ships Association

amplifies the signal to develop enough motor drivepower to steer the receiver head to the azimuthbearing selected on the IRDSC by the operator.Four feedback signals are involved in ensuringthe receiver head maintains the correct LOS. Anazimuth tachometer signal from the receiverconverterazimuth drive unit is fed back to the modelogic module. The mode logic module produces agimbal rate signal for the azimuth rate compensationmodule. An azimuth position signal from the sameazimuth drive unit is fed back to the azimuth positioncompensation module. The mode logic modulecompares the azimuth position signals with theIRDSC azimuth input and, as applicable, outputs aposition error signal to the azimuth rate compensationmodule. An azimuth gyro rate signal from thereceiver-converter’s gyro unit is fed to the azimuthrate compensation module. Also, an azimuth currentdrive signal is fed back to the rate compensationmodule. The rate compensation module processes allof the feedback signals (position error, gimbal rate,gyro rate, and current drive signals) and develops anoutput signal. This output signal, if necessary,maintains the receiver head at the correct selectedheading.FORWARD MODE (FWD).— The FWD modecommand is processed by the azimuth mode logicmodule. This module outputs a FWD mode commandsignal to the azimuth position compensation module.This module will process the command signal. It thenoutputs a position loop command and a gimbal anglesignal to the azimuth rate compensation module. Thismodule then sends an azimuth drive signal to steer thereceiver head to 0° azimuth. The azimuth drive signalis amplified by the azimuth heat sink module toproduce the motor power to drive the motors in thereceiver-converter. The stabilization/positioningfeedback circuits work the same as the circuits in theposition mode previously explained.MANUAL TRACK MODE.— The manual trackmode command signal is processed by the mode logiccircuit. This circuit sends a manual track commandsignal and an azimuth rate inhibit signal to theazimuth rate compensation module. These signalscause the circuits to accept only azimuth rate signalsfrom the target tracking sight control assembly. TheTTSC assembly is a pistol grip unit. The operatoruses the thumb control on the pistol grip unit to aimthe receiver head to the desired LOS. The azimuthdrive output signal from the circuit is controlled bythe TTSC, and no feedback is used for stabilization.Action of a comparator circuit in the azimuth ratecompensation module determines when thereceiver-converter gimbals reach their electricallimits and produce limit signals (CW and CCW).These limit signals prevent the manual track modeand computer track mode commands from developingthe azimuth drive signal. The limit signals are fedback to the mode logic module that outputs a CW orCCW signal to the azimuth position compensationmodule. This signal causes the module to develop anerror signal that, in turn, develops appropriateazimuth drive.COMPUTER TRACK MODE.— The aircraftcomputer supplies gimbal control data bits (azimuthand elevation position rate commands) from itsprogram to the decoder storage module. This moduledemultiplexes and stores 12-bit azimuth and elevationrate commands. It also provides azimuth andelevation data outputs to the digital-to-analog (D/A)converter module. The purpose of storage is to allowthe decoder to output data bits to the D/A converter,while the computer updates itself from feedbackinformation before issuing new gimbal control signalsto keep the receiver head at the programmed LOS.When the computer track mode is selected on theIRDSC, the computer track command is processed bythe mode logic module. This module will send acomputer track mode command to the D/A converterand to the azimuth rate compensation module. Thesignal enables the D/A converter to process azimuthdata bits into analog azimuth position rate signals,which are fed to the azimuth rate compensationmodule. The D/A converter also sends a computertrack mode status signal to inform the aircraftcomputer that the D/A converter is operating in thecomputer mode. The computer track command signalenables the azimuth rate compensation module toaccept azimuth position rate signals from the D/Aconverter only. The azimuth rate compensationmodule disables inputs from the azimuth positioncompensation module. This means no feedbackinformation can be processed in the computer mode.The rate compensation circuit processes the azimuthposition rate signal from the D/A converter andoutputs an azimuth drive signal. This signal goesthrough the azimuth heat sink circuit to slew thereceiver head to the azimuth position programmedinto the computer.An azimuth resolver in the receiver-converterfeeds back four-wire resolver position informationsignals to the azimuth rate compensation module6-20