-Two virtually identical channels, the COMMAND channel and the MONITOR channel
-One independent channel which performs the FIDS functions.
The command channel receives analog data, ARINC sensor data and discrete
signals in order to compute the control laws. It then generates the
flight commands used to drive the corresponding servo actuators.
The interfaces between the computer and the actuators, as well as the
position feedbacks, are of the analog type.
Similarly, the monitor channel receives the sensor data required to
compute the control laws.
Its role is:
-
To consolidate the computations of the command channels
-
To monitor the servo loops to be able to change over to the opposite
FAC.
Each channel includes a digital part and an analog part:
-
The digital part is based on a 16-bit microprocessor and performs input/output system and control law computation.
-
The analog part performs sensor acquisition ; only the command channel assumes power amplification for the three servo loops : yaw damper, rudder trim and rudder travel limiting.
The FAC performs five types of functions:
-Input management and monitoring
-Control law computation and synchronization
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FAC - Component Location
Figure 001
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1 1
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General Architecture
Figure 002
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1 -Control rudder-surface servo-loop
-Engage logic
-Output management.
In addition, each channel has its own power supply.
(1)
Input management and monitoring This part, which is doubled, is responsible for the acquisition of the input parameters. These take various forms:
-Analog AC signals from various control rudder-position sensors (inductive pick-off type)
-ARINC signals from various systems (ADIRS, LGCIU, ELAC, FMGC, SFCC) and from the opposite FAC
-Discrete signals, from engagement pushbutton switches and landing gear data
-Analog DC signals.
These inputs are monitored and some of them are consolidated before
being used by the control laws.
(2)
Control law computation The actuator position commands are computed by the CPU on the basis of the above ARINC and analog data and the embedded control laws. A real-time monitor supervises the sequencing of the various tasks and the activation of a watchdog to protect the processing unit itself against incorrect program running.
(3)
Control rudder-surface servo-loops This function provides current signals for actuator control. These signals are generated from the computed software orders and the feedback position of the sensors (LVDT and RVDT) for the three analog power loops (yaw damper, rudder trim and rudder travel limiting).
(4)
Engage logic The function consolidates the statuses of the various monitors and makes possible to pressurize the servos if all the required conditions have been met. In the event of a fault, this engage logic can cut off the control signals to the servos.
(5)
Output management This part, which is doubled, is responsible for the generation of the output parameters. These are of various types:
-
To the monitoring channel to implement the various cross-monitors,
-
To the other aircraft systems (FAC opp, FMGC own, FMGC opp, DMC 1, 2, 3, trim indicator).
-Analog outputs
1EFF : ALL 1 22-66-00Page 5 1 1 Feb 01/98 1 1 1CES 1 A current amplifier provides the interface between the digital servo error and each servo after D/A conversion.
-Discrete outputs These make it possible to indicate the status of the computer and to command the engage relays.
(6) Power supplies Each channel has its own power supply which, from the 28VDC aircraft network, provides the voltages used by the channel : +5V, +15V, -15V. Each power supply is monitored by the other channel.
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