LCT, CC DA, and DASH Actuator Simulator Circuits

TM 55-4920-430-13

1-15. LCT, CC DA, and DASH Actuator Simulator Circuits. Circuit card A2 includes three cir-

cuits which simulate LCT, CCDA, and DASH electromechanical actuators and their feedback devices.

a. Longitudinal Cyclic Trim Actuator (LCT) Simulator Circuit. (See fig. 1-7.) LCT actuator static/

dynamic gains are simulated by amplifiers U1 through U4 and their associated resistors, capacitors,

and diodes. The electrical load of the split-field motor of the actuator is simulated by 8.06-ohm resis-

tors R20, R21, R22, and R23 (not shown). Resistors R20 and R21, in series to ground, simulate the

extend winding of the actuator motor. Resistors R22 and R23, also in series to ground, simulate the

retract winding.

(1) Amplifier U4, with resistors R1 through R3, form an inverter. The inverter develops opposite

directional sense for the retract and extend inputs, both of which are +28-volt dc. The gain of amplifier

U4 is -0.43, providing a -12-volt dc output for a +28 volt-dc input at pin 26.

(2) Amplifier U3 is a summing amplifier. Gain for the extend signal is -1, gain for the retract

signal is -0.43. As a result, gain for the extend input from pin 26 to TP2 is +0.43. Gain for retract input

from pin 27 to TP2 is -0.43. The rc characteristic of the motor is simulated by the 0.2-second lag in re-

sistor R8 and capacitors C2 and C3.

(3) Amplifier U2, resistor R10, and capacitor C6 form an integrator which similates the steady-

state velocity characteristic of the motor and gear train. Gain from the output of U2 to TP4 is 0.01 volt-

dc. Actuator limit switches are simulated by diodes VR1 and CR3. Zener diode VR1 limits output to

-6.8-volt dc nominal. Diode CR3 passes only the negative output. As a result, the output swing is 0 to

-6.8-volt dc. Integrator drift rate is set to zero by resistor R4.

(4) Amplifier U1 is connected as a voltage follower to isolate the integrator from the external

load at pin 58. Output impedance is fixed at about 58 ohms by load isolation resistor R14.

(5) When a positive voltage, an actuator extend signal, is applied to pin 26, the output at pin 58,

increases in a negative direction. This simulates the feedback signal from the actuator. The opposite oc-

cur when a negative voltage, an actuator retract signal, is applied to pin 27.

(6) During extend self-test, pin 25 is connected to ground at pin 4 by SELF TEST switch S16 (not

shown). This operates lct self-test relay K1 and connects a self-test extend signal from pin 29 to the

input of amplifier U4. Relay K1 also disconnects the extend signal circuit at pin 26 from the input of

U4 during retract self-test. SELF TEST switch S16 connects pin 25 and 28 to ground at pin 4. This

operates self-test relay K1 and polarity relay K2, connecting a self-test retract signal to amplifier U3.

Relay K2 also disconnects the retract signal circuit at pin 27 from the input of amplifier U3.

b. Cockpit Control Driver Actuator (CCDA) Simulator Circuit. (See fig. 1-8. ) Integrated circuits U9

and U11 through U15 simulate the collective CCDA actuator. This actuator includes a 2-phase motor, a

servo amplifier, two clutches, a gear train, and an ac feedback device.

(1) The CCDA output of the AFCS computer is a 400 Hz voltage, leading, or lagging a 400 Hz

reference by 90. This voltage is demodulated and amplified by amplifiers U15 and U13. The gain of

the demodulator-amplifier is 2 volt/volt. The output at TP10 is negative when input voltage is leading.

Output is positive when input voltage is lagging.

(2) The gain of amplifier U12 is -1.82. The time constant, fixed lag resistor R57 and capacitor

C15, is 0.1 second nominal. Zener diodes VR8 and VR9 limit the output of U12 to 10.5-volt dc.

(3) Analog multiplier U9 is connected as a modulator. The transfer function of the multiplier is

(X1-X2) (Y1-Y2)

10. The voltage applied at Y1 is fixed by resistors R62, R63, and R64 at 6.8 volts

nominal. Resistors R60 and R61 form a 9:1 voltage divider. As a result, the gain from the output of am-

plifier U12 to pin 40 is 0.9 x 6.8 10 = 0.61-volt rms/volt dc. The simulated servo limits are 10.5 vac x

0.81=6.4-volts rms nominal. The output of U9 at pin 40 is in phase with the reference voltage applied

at pins 1 and 31 when the input signal applied to pin 41 leads the reference by 90. The output is out-of-

phase when the input signal lags. This simulates the feedback from the actuator.

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