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control unit stack consists of two boards: the large power
board and on top the micro-controller board. The pilot
has a control interface with switches, buttons and LEDs
which is connected to the micro-controller board. The
limit switches, which detect the motion of the landing
flap, are also connected to the micro-controller board.
There is a power stage for the DC brush motor; there is
an additional power switch for the power-off motor brake.
The micro-controller derives from these inputs the
required signals for the power stages (for motor and
brake).
The micro-controller
drives the motor power stage according to the commanded
direction ("UP" or "DOWN"). The micro-controller
also reads the current sensor signals of the motor
current and the input current and limits both to
acceptable levels. This prevents excessive large loads (by
the inrush current pulse) on the flaps and the aircraft
structure, compared to a motor drive unit without current
control. The micro-controller also activates the power-off
motor brake which blocks the motor in the final positions.
The status and the movement of the flap are signalled by
LEDs.
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