An electronic control for an electrohydraulic active control landing gear for the F-4 aircraft

CONTENTS (Continued)

Page

APPENDIX

A DIGITAL SCALING . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..*.....*

B MICROPORCESSOR PROGRAM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

FIGURES

Illustration of Variables in Nonlinear

3-1

Simulation of Simplified Vertical Drop Case .........

3-2 F-4 Landing Gear Metering Pin Area Versus

Strut Stroke

3-3 Open-Loop,

F-4 Gear, Open-Loop, No Compensation Frequency

3-4

Response

F-4 Gear, Open-Loop, No Compensation Frequency

3-5

Response

3-6

Open-Loop Nonlinear Model, 2200 LBF Input ...........

3-7

3-8 Compensation

3-10 Nyquist Plot-Compensation

3-11 No Compensation.

iv

CONTENTS (Continued)

Page

............................

90 Hz Notch and Lead/Lag

3-13

............................

3-14 Totally Compensated Loop

3-15 Case 2 Comp: Notch at 90 Hz ........................

Compensation-Notch 8 90 Hz + Lead/Lag 8 617,

3-16

........................................

6170 rad/sec

...........................

3-17 Totally Compensated Loop.

..................

3-18 Block Diagram of Linear Math Model

Case 1 ..............................................

3-19

3-20 Case I..............................................

.................................

Case 1 Passive Gear

3-21

..................................

3-22 Case 1 Active Gear

.................................

3-23 Case 1 Passive Gear

..................................

3-24 Case 1 Active Gear

..................................

Case 1 Active Gear

3-25

..................................

3-26 Case 1 Active Gear

3-27 Case 2 ..............................................

3-28 Case 2 ..............................................

.................................

3-29 Case 2 Passive Gear

..................................

Case 2 Active Gear

3-30

................................

3-31 Case 2 Passive Gear.

..................................

3-32 Case 2 Active Gear

V

CONTENTS (Concluded)

Page

3-33 Case 2 Active Gear

3-36 Bomb Crater Landing

3-38 Bomb Crater Landing Passive Gear

3-40 Bomb Crater Landing Passive Gear

3-43 Bomb Crater Landing Active Gear

5-l

vi

1.0 SUMMARY

The electronic controller described in this report is a

modification of the controller which was designed under NASA Contract

NASI-14459 and fully documented in Reference 1.

As in the original design, the controller continuously

compares the kinetic energy of the aircraft with the work potential of

the gear until the work potential exceeds the kinetic energy. The

wing/gear interface force present at this condition becomes the

command force to a servo loop which maintains the wing/gear interface

force at this level by providing a signal to an electrohydraulic

servovalve to port flow into or out of the landing gear.

Analytical results indicate that the controller provides

significant reductions in forces sustained by the aircraft during

vertical drops and radical reductions in forces during rollout over

repaired bomb craters.

2.0 INTRODUCTION

Hydraulic Research Textron (HRT) was retained under NASA

Contract NASl-16420 to design a controller for an active control

landing gear (ACLG) to be used on the F-4 aircraft. The design was a

modification of the controller originally designed for a 2948 kg.

(6,500 lb) aircraft and described in detail in Reference 1.

The design was to be based on a digital computer simulation

using a linear model of the aircraft and landing gear. However, it

became apparent early in the program that the linear model was not

adequate by itself to predict performance under certain phases of

landing where nonlinear relationships prevail. Therefore extensive

use was made of the HRT nonlinear model as well as the linear model to

achieve the final design. The parameters of the aircraft/landing gear

system were supplied by NASA.

The problem was similar to that encountered in the original

design. However, the aircraft is heavier and the stroke of the strut

is greater so that new scaling requirements are imposed. These are

discussed in Appendix A.

3.0 DYNAMIC ANALYSIS OF F-4 ACTIVE CONTROL LANDING GEAR

3.1 PREFACE

This section presents the dynamic analyses that were

performed for the development of an electrohydraulic active control

system for the F-4 landing gear.

The main objective of these analyses

was to develop a loop compensation network for the active control

landing gear concept applied to the F-4 aircraft and to evaluate the

performance of the active control gear with respect to the passive

(conventional) F-4 landing gear.

Section 3.2 contains a list of

symbols and section 3.3 describes the analytical tools used in these

studies, which are the linear and nonlinear vertical drop dynamic

simulation models of the landing gear, without aircraft equations of

motion included. Section 3.4 presents the correlation between the

linear and nonlinear simulations.

Section 3.5 presents the

development of the loop compensation network.

Section 3.6 presents

analytical results for specific landing impact cases and cases of

rollout over "repaired bomb craters", using the nonlinear vertical

drop model, for both the passive gear and the active control gear.

3.2 SYMBOLS

area of orifice in shock strut orifice plate, see Figure 3-l.

AO landing gear metering pin area, see Figure 3-2.

AP

shock strut hydraulic area (piston area), 0.01024 m2

A1

(15.87 in2)

shock strut pneumatic area (cylinder area), 0.01494 m2

A2

(23.16 in2)

annular area in shock strut between piston and cylinder

A3

walls, 0.00761 m2 (1.179 in2)

ATIRE constant in tire deflection force equation, 1.20

discharge coefficient for active control servovalve orifice,

'd

0.62

discharge coefficient for shock strut orifice, 0.60

'do

orifice coefficient for shock strut orifice

cO

= CdoAo J 2gc/p, m4secw1,N1b (in3/sec/ps&)

CP Linearized orifice coefficient for active control servovalve

=

- g$E 3.16 x 10-11m5.N-l

l sec-l(0.01334 in3/sec/psi)

linearized orifice coefficient for shock strut orifice

cpO

=aQO=

1 901 x 10-gm5*N-1*sec-1

(0.8 in3/sec/psi)

co/w pp9, l

apl

linearized orifice coefficient for active control servovalve:

CQ

~QSV =

=

C,,J( P3+PR)/2, 8.61m2/sec(13,340 in3/sec/in)

axsv

orifice coefficient for active control servovalve:

C

sv

= CdWsvJ 2gc/p, 0.00268m3* set

-'*N (344.4 in3/(in lbf

lh >>

f coulomb friction between shock strut piston and cylinder, 222.N

(50.lbf)

vertical force exerted on shock strut by the runway surface, N

Fa

(lbf)

impact phase limit force, N (lbf)

Fli

limit force, N (lbf)

Flim

shock strut force, N (lbf)

FS

F wing-gear interface force, N (lbf)

wg

acceleration due to gravity, 9.81m/sec2(386.in/sec2)

g

gravitational acceleration constant

gC

1 kg*m*N-1*sec-2(12 slug*in*lbf-1*sec-2)

input signal to electronic compensation networks, A

il

output signal from electronic compensation networks, or input

i2

signal to active control servovalve, (f0.040 A maximum)

amplifier gain in active control loop, 0.000020 A/V

Ka

position feedback gain in strut position control loop, 563 V/m

Kf

(14.29V/in)

fraction of total strut stroke assumed available when computing

KFDGE

impact phase force, 1.0

K position gain of servovalve in active control loop, 0.0635 m/A

sv

(2.50 in/A)

KTIRE constant in tire deflection force equation 1727.1 kN/m

(9862 lbf/in)

gain in strut position control loop, 1.0 m/m (1.0 in/in)

Kx

L total lift force, N (lbf)

M mass of airplane per gear, 8345 kg (18398 lbm)

mass of upper portion of landing gear (cylinder plus orifice

MC

plate attachment, kg (slugs)

mass of lower portion of landing gsar (piston plus tire), 204.

AIL

kg (13.99 slugs = 1.166 lbf . set /in = 450. lbm)

upper mass, 8143. kg (558. slugs = 46.5 lbf. sec2/in = 17948.

%J

lbm)

potential energy stored in tire due to compression, N . m (ft .

PEt

lbf)

hydraulic supply pressure, 2.07 x lo7 N/m2 (3000 .

Psi 1

p&9

hydraulic return pressure, 0.0 N/m2 (0.0 psi)

pR

hydraulic pressure in shock strut piston, N/m2 (psi)

p1

pneumatic pressure in shock strut cylinder, N/m2 (psi)

p2

pressure in vslume betweeen walls of shock strut piston and

p3

cylinder, N/m (psi)

flow rate t rough shgck strut orifice from piston to

QO

cylinder, m /set (in /set)

flow rate from active control servovalve to shock

Qsv

strut piston, linear model, m3/sec (in3/sec)

Q flow rate through active control servovalve from

svl

supply pressure to the shock strut piston, m3/sec (in3/sec)

flowrate through active control servovalve from shock

Q

sv2

strut piston to return pressure, m3/sec (in3/sec)

the slope of the limit force with respect to time during

RS

transition phase, 444800. N/set (100000. lbf/sec)

S LaPlace operator, set-l

t time, set

V velocity, m/set (in/set)

sink rate, m/set (in/set)

vS

hydraulic volume in shock strut piston and lines up to

Vl

the active control servovalve, 0.00497 m3 (303.in3)

pneumatic volume, 0.00742 m3 (453. in3) for fully extended

V2

strut

volume between shock strut piston and cylinder, 0.0 m

V3

(0.0 in3) for fully extended strut

W window width of orifices on third stage spool of active control

sv

servovalve, 0.0884 m (3.48 in)

displacement of lower mass of shock strut or axle, m (in)

‘a

commanded position of shock strut, 0.216 m (8.50 in)

xC

ground level displacement, m (in)

xg

shock strut stroke, m(in) X, = 0 fully extended, X, = 0.403 m

xS

(15.88 in) fully compressed

displacement of wing gear interface, m (in)

xw

bulk modulus of hydraulic fluid, 6.89 x lo8 N/m2 (1 x lo5 psi)

B

ratio of specific heat of gas at constant pressure to that at

V

constant volume, 1.06

mass density of hydraulic fluid, 838 kg/m3 (0.000941

P

slugs/in = 0.0303 lbm/in3)

time constant in strut position feedback loop, 0.10 set

=f

time constant in compensation, 0.001621 set

?

time constant in compensation, 0.0001621 set

=2

time constant in compensation, 6.464 x 10B4

set

T3

-5

time constant in compensation, 6.464 x

10 set

T4

w

corner frequency in active control servovalve transfer

C

-1

function, 1263 set

w

natural frequency in active control servovalve

sv

transfer function, 655.5 see-'

-1

natural frequency of notch network, 565 set

al

c

damping coefficient in active control servovalve transfer

sv

function, 0.436

damping coefficient in denominator of notch network, 5.1

cl

damping coefficient in numerator of notch network, 0.1

C2

Subscripts:

i initial conditions before impact

im impact phase

L lower mass

max maximum value

min minimum value

r rollout phase

S shock strut relative motion of lower mass (piston) with respect

to the upper mass (cylinder)

sv servovalve

tr transition phase

U

upper mass

Miscellaneous:

indicates the differential of a variable

d( >

indicates difference or change in a variable

A( )

) dots indicate differentiation with respect to time

(. 1, C..), c...

3.3 DYNAMIC SIMULATION MATH MODELS

The main analytical tools used in these studies are the linear

(s-domain) and nonlinear (time domain) vertical drop dynamic

These models simulate motion

simulation models of the landing gear.

Aircraft equations of motion are not

in the vertical axis only.

included, and aircraft mass (per gear) is simulated as a lumped mass

resting on top of the landing gear.

3.3.1 Linear Model

The linear model simulated the dynamics of the active control

landing gear system in the frequency domain for small perturbations

about the condition where the airplane mass (per gear) is resting on

top of the gear with the gear always in contact with the ground and

with the lower cylinder hydraulic pressure at a value halfway between

The input disturbance

the hydraulic supply and return pressures.

variable is command limit force. Airplane lift and ground level are

assumed constant. The linear model is a valuable tool since it allows

rapid evaluation of system modifications or the effect of variation in

system parameters in the areas of system stability and frequency

response. A detailed description of the linear model, including

equations, is presented in Reference 1, and will not be repeated

here. The values of the constants used in the simulations for this

study are given in Section 3.2 of this report.

3.3.2. Nonlinear Model

The nonlinear model is developed from the time-dependent

algebraic and differential equations of the system. The response of

the system to input disturbances is obtained by integrating the

Controller laws

differential equations with respect to time.

(including switching logic) and all other identifiable nonlinear

attributes of the system of significance are simulated. Thus, the

nonlinear model represents a more accurate simulation of the actual

physical case than the linear model. This however, comes at the

expense of considerably longer computational times. The nonlinear

model accepts input variations in airplane lift, ground level, and

command limit force (for vertical drop impact transients, however, the

controller automatically sets the command limit force subsequent to

initiation of active control). A detailed description of the

nonlinear model, including equations, is presented in Reference 1.

The nonlinear model used herein is identical to that described in

Reference 1 except the values of the system constants are different

and the linear spring tire force assumption was modified to a

nonlinear spring, according to the relationship:

KTIRE(XA -XG)ATIRE for XA > XG

Fa= I.

0 for XA < XG

where KTIRE and ATIRE are constants. This equation replaces the

expression for F, in Equation 4 of Reference 1.

The values of the constants used in the linear and nonlinear

simulations for this study are given in Section 3.2.

The important variables are shown in Figure 3-l.

3.4 CORRELATION OF LINEAR AND NONLINEAR MODELS

Since both the linear and nonlinear models were utilized in the

development of the loop compensation, the first task was to correlate

the linear model with the more precise nonlinear model to ensure that

it would give at least reasonably credible results. Figures 3-3, 3-4,

and 3-5 show frequency response results obtained from the linear and

nonlinear models, without compensation. The loop is opened at the

point of wing/gear force feedback, and the strut position feedback

loop is not included. The input is command limit force and the output

is the wing/gear force response. The nonlinear runs were made with

zero lift and for command amplitudes of f890 N (f200 pounds), and the

amplitude and phase angle at each frequency were computed from a

Fourier analysis of the resultant input and output waveforms.

The

linear model results were obtained using a linearized ogifice

coefficient for the shock strut orifice (CP,) of 0.8 in /set/psi.

This value seemed to give the best overall correlation between the

linear and nonlinear models. Note that the agreement is reasonably

good out to a frequency of about 150 Hertz. At higher frequencies,

the nonlinear model shows considerably more phase lead and less

amplitude response than the linear model. Figures 3-6 and 3-7 show

open loop Nyquist diagrams for these same results, for the linear and

nonlinear models, respectively. Again, reasonably good correlation is

indicated.

TOTAL UPPER MASS, =M, = M + M, M (Al RPLANE MASS) M, (CYLINDER MASS) INPUTS CYLINDER \WA A 9- STRUT STROKE:

x,= xwg-x

a

I I

+‘a AXLE t TIRE GROUND FIGURE 31 ILLUSTRATION OF VARIABLES USED IN NONLINEAR SIMULATION OF SIMPLIFIED VERTICAL DROP CASE STRUT STROKE - m 0.8 - - - - .

0.6 Oh-5 0.4 0.3 0.2 0.1 A “0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 STRUT STROKE - in.

t t FULLY-EXTENDED GEAR FULLY-COLLAPSED GEAR @X=0 in.

@ X = 15.88 in.

FIGURE 3-2. F-4 LANDING GEAR METERING PIN AREA VERSUS STRUT STROKE +30 LINEAR MODEL, CP, = 0.8 / +20 +10 % O i= 0 z OUTPUT = FWG INPUT FLIM 2 -10 @ NONLINEAR MODEL, + 200 Ibf INPUT -20 -30 “9 FREQUENCY -Hz FIGURE 3-3 OPEN-LOOP, NO COMPENSATION ‘FfdEQUENCY RESPONSE -20 m P 0 -40 Ill l- ? -60 % a @ NONLINEAR MODEL -80 -100 -120 1 10 100 1000 10,000 FREQUENCY -Hz FIGURE 3-4. F-4 GEAR, OPEN-LOOP, NO COMPENSATION FREQUENCY RESPONSE OUTPUT = FWG FLIM INPUT kj -200 KA = 0.014 I n -300 @ NONLINEAR MODEL -400 -500 0.1 1 10 100 1000 FREQUENCY -Hz FIGURE 3-5. F-4 GEAR, OPEN-LOOP, NO COMPENSATION FREQUENCY RESPONSE

LOOP COMPENSATION

3.5

The open-loop Nyquist diagrams of the uncompensated system

presented in the previous section (Figures 3-6 and 3-7) indicate that

Thus, compensation is deemed

the system is unstable around 100 Hertz.

The compensation that was developed for this system is

necessary.

implemented in the forward path of the control loop, and has the

transfer function:

following

2(.100)s+1

S

565. 1547.+l

=

(3-l)

T(S)

S

S

2(5.10)s+1

+

6170. +' 15470. +l

L L I

It consists of a notch filter at 90 Hertz and two first-order

The frequency response of the compensation

20 dB lead/lag networks.

is shown in Figures 3-8 and 3-9 and the Nyquist plot including

compensation is shown in Figure 3-10.

To understand the effect of each part of the compensation

network on system dynamics, open-loop Nyquist diagrams obtained from

the linear model are presented with successive portions of the

compensation network incorporated. Figure 3-11 shows the

uncompensated Nyquist diagram (this is the same as the results in

Figure 3-6 except that the amplifier gain has been adjusted).

Figure 3-12 shows the effect of including the compensation notch

The system is now stable, but rather low damped at a frequency

only.

around 60 Hertz. The first lead/lag network was included to add phase

lead in this frequency range. The Nyquist diagram with the notch and

this lead/lag incorporated is shown in Figure 3-13. The second

The

lead/lag was included to add phase lead in the 190 Hertz range.

open-loop Nyquist diagram with the entire compensation network

included is presented in Figure 3-14.

The effect of each part of the compensation network on system

dynamics was also evaluated using the nonlinear model on a typical

The conditions of the case are as follows: vertical drop case.

1. The sink rate. prior to impact is 1.83 m/set (72 ins/set)

2. The lift is equal to airplane weight at initial impact,

then linearly reduced to 10 percent of the airplane

weight over the next 1 second, then held constant at 10

percent thereafter.

3. The ground level is held constant.

-1 > 2 -2 G a -3 I -4 -5 -6 -7 -8 -9 -10 / 0 1 4 5 6 7 8 9 10 -4 -3 -1 2 3 -5 -2 REAL FIGURE 3-6. OPEN-LOOP LINEAR MODEL WITHOUT COMPENSATION > z 0 G -1 2 -2 -3 -4 -5 -6 \ -7 ' \ / -8 7 -9 -10 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 REAL FIGURE 3-7. OPEN-LOOP NONLINEAR MODEL, 889.6N (k 200 LBF) INPUT 0 10 ’ 10-l 100 10’ 102 103 104 105 FREQUENCY - Hz FIGURE 3-8 COMPENSATION -40 -60 10' 102 103 104 106 10-l loo FREQUENCY-Hz FIGURE 3-9 COMPENSATION h) > 40 z I: z 30 200 Hz 20 40 60 80 REAL FIGURE 3-10 NYQUIST PLOT-COMPENSATION -I” 5 6 7 6 9 10 11 12 13 14 -6 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 REAL FIGURE 3-11 iu0 COMPENSATION > $ -1 G 2 -2 t -3 , -4 -5 -6 -7 -8 -9 .

-2 -1 0 1 3 4 5 6 7 REAL FIGURE 3-12. 90 Hz NOTCH $ Q -1 z c7 a -2 z -3 -4 -5 -6 -7 -8 -9 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 '12 13 REAL FIGURE 3-13. 90 Hz NOTCH AND LEAD/LAG I 1. 1 I I I 4.

-6 -8 I -2 -1 0 .I 2 3 4 5 6 7 8 9 10 11 12 13 REAL FIGURE 3-14 TOTALLY COMPENSATED LOOP v) 5000 z 4000 E LL 3000 -1 E3 1 .o 0.4 0.5 0.6 0.7 0.8 0.9 1.1 1.2 0 0.1 0.2 0.3 TIME -SECONDS FIGURE 3-15 CASE 2 COMP: NOTCH AT 90 Hz 40 - 30 - .I 5000 r W iii g 20- A ?

ti LL 3000 10 - \ O- I I I I I I I I I I I

J

-1 E3 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 .o 1.1 1.2 TIME - SECONDS FIGURE 3-16 COMPENSATION - NOTCH @ 90 Hz + LEAD/LAG @ 617,617O RAD/SEC

9ooc

“u 20

4ooa

I?

d -1E3 0.1 0.2 1.1 1.2 0.5 0.6 0.7 0.8 0.9 1.0 0.3 0.4 TIME -SECONDS FIGURE 3-17 TOTALLY COMPENSATED LOOP The resultant force transients are shown in Figures 3-15, 3-16,

and 3-17 for the notch compensation only, the notch plus the first

lead/lag compensation only, and the entire compensation network, respectively. The results show that the notch stabilizes the system,

and the lead/lag networks effectively reduce the oscillatory behavior

of the system at the higher frequencies. It should be noted that the

amplifier gain was set at 0.028 milliamperes per volt for each of

these runs, which is higher than the final design value of 0.020.

Note from Figures 3-15 through 3-17 that the system exhibits a

low damped oscillatory behavior at about 15 Hertz. This behavior is

also exhibited in the Nyquist diagrams already presented. The linear

model Nyquist diagram results predict a somewhat lower frequency of

oscillation than the nonlinear results, however, (compare Figures 3-6

and 3-7) an attempt was made to increase the damping of these

oscillations by adding some phase lead in that frequency range using

another 20 dB lead/lag network. Although the resultant linear model

Nyquist diagram looked promising, the nonlinear vertical drop results

showed marginal improvement in the low-frequency oscillatory

behavior. The resultant compensation also possessed significantly

greater high-frequency amplification, an undesirable result. The

approach was thus taken to employ the compensation network described

previously (Equation 3-l), and improve the low frequency oscillations

by reducing the loop gain as much as possible without significantly

degrading the performance of the active control concept. It was found

that the amplifier gain of 0.028 milliamperes/volt used in

Figures 3-15 through 3-17 could be reduced to 0.020 mA/V without

significantly affecting the ability of the active control gear to

for all the cases run herein.

reduce the wing/gear forces, The block diagram of the system is shown in Figure 3-18.

3.6 VERTICAL DROP ANALYTICAL RESULTS

The nonlinear model was used to simulate various vertical drop

landings and rollouts over repaired bomb craters using active control

on the F-4 landing gear.

In all cases the passive gear was also

simulated in order to evaluate the effectiveness of active control in

reducing the loads transmitted through the wing/gear interface. The

compensation developed in Section 3.5 (Equation 3-l) was employed in

all active'control cases, and the amplifier gain used was 0.020 mA/V.

3.6.1 Vertical Drop, Case I

The conditions for vertical drop case number 1 are as follows: 1. The sink rate prior to impact is 1.83 m/set (72 in/set).

2.

The lift equals airplane weight (per gear) at all times.

3.

The ground level remains constant.

F LEAD-LAG WI NETWORKS SERVOVALVE NOTCH NETWORK - KS” co Ka s* + *t*w, s+u:) il Flim + +’

4A-y

+ ,*t2~,w,stw~) ( COMPENSATION I i FIGURE 3-18 BLOCK DIAGRAM OF LINEAR MATH MODEL 50 - 11

ia

E

40 -

a

Ei i 8 30- z

c 5 -

?

W

t 5 -

u a 2 20-

I -

.

. 3 -

I

I

10 -

1 z I-

I

O- 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 TIME -SECONDS FIGURE 3-19 CASE 1 0.3 .

ACTIVE GEAR PASSIVE GEAR .

0.6 0.7 U.8 U.Y I 0.1 0.2 0.3 0.4 0.5 TIME -SECONDS FIGURE 3-20 CASE 1 GROUND LEVEL -- O- - -1 .E ?

5 -2 W r -3 \ $ .I - -4 \ ul \ \ 0 -5 \ /‘\ WING/GEAR INTERFACE \ -6 , - \ \ \ -7 \ 1’ \ / .2- \ 4 I- ‘.

/ N-- / - -9 I I I I I I I I

I

I- -10 O 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 TIME -SECONDS FIGURE 3-21 CASE 1 PASSIVE GEAR 2 2 GROUND LEVEL GROUND LEVEL l- l- -/ -/ 0 0 / / -1 -1 /’ /’ -2 -\ -2 -\ \ \ / / yT yT \ \ AXLE AXLE -3 -3 \ \ 1’ 1’ \ \ -4 - -4 - I’ I’ \ \ \ \ 1’ 1’ \ \ -5 - -5 - \ \ /’ /’ \ \ WING/GEAR INTERFACE WING/GEAR INTERFACE -6 - -6 - \ \ 1’ 1’ \ \ \ \ /’ /’ -7 - -7 - \ \ / / J J / / -8 - -8 - \ \ / / \ \ / / \ \ -9 - -9 - /’ /’ \ \ \ \ \ \ -10 - -10 - \ \ #” #” ‘. ‘.

\ \ -11 - -11 - #/ #/ -W-C- -W-C-

I I I I I I I I

I

-12 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 TIME z SECONDS FIGURE 3-22. CASE 1 ACTIVE GEAR g 450 n ?

!ti $3 400 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 .o TIME -SECONDS FIGURE 3-23 CASE 1 PASSIVE GEAR LOWER CYLINDER HYDRAULIC PRESSURE (Pl) UPPER CYLINDER PNEUMATIC PRESSURE (P2) : 0. 300 200( !

m w 5 250 ii iTi!

a 200 E E 1OO( 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 TIME - SECONDS FIGURE 3-24 CASE 1 ACTIVE GEAR 0.1 0.08 0.06 0.04 0.02 -0.2 -0.04 -0.06 -0.08

I

-0.1 -0.12 0 0.1 0.2 0.3 0.4 0.5 0.7 0.9 1.0 0.6 0.8 TIME -SECONDS FIGURE 3-25 CASE 1 ACTIVE GEAR

r

-100 :: m .r -200 2 -300 E g -400 J IL 5 i -500 > -600 -700

I I

I I I

I I

I I

-800 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 TIME -SECONDS FIGURE 3-26 CASE 1 ACTIVE GEAR Command limit force is set automatically by the controller.

Figure 3-19 shows the resultant wing/gear force transients for the

active and passive gears. Active control reduces the peak force 20

percent below the passive gear case. Figure 3-20 compares the strut

stroke between the two cases. The active gear uses significantly more

stroke than the passive gear. Figures 3-21 and 3-22 show the vertical

displacements of the ground level, landing gear axle, and wing/gear

interface for the passive gear and the active gear, respectively. The

displacements are positive in the up direction, and are all referenced

to the condition where the gear is fully extended and barely in

contact with the ground with zero tire compression. Thus, at the

point of impact (at time = 0) all the variables are zero. When the

axle displacement is below the ground level (which is constant), the

tire is in compression; when it is above, the landing gear is off the

ground. Also, when the wing gear interface displacement is the same

the gear is fully extended.

as the axle displacement, Thus, in

Figure 3-21 for the passive gear, the landing gear becomes fully

extended at 0.548 second and rebounds (i.e., leaves the ground) at

0.560 second. Note from Figure 3-22 that the active control causes

the gear to remain in contact with the ground longer and when it

rebounds, it does so at a lower upward velocity.

Figures 3-23 and

3-24 show the lower and upper cylinder pressure transients for the

passive and active gears, respectively. The pressures are

significantly reduced in both cylinders as a result of active

control. Finally,

Figures 3-25 and 3-26 show the valve third stage

spool displacement and the valve hydraulic flow rate to the gear

respectively, for the active control case.

3.6.2 Vertical Drop, Case 2

The conditions for vertical drop case number 2 are as follows: 1. The sink rate prior to impact is 1.83 m/set (72 in/set).

The lift equals airplane weight (per gear) prior to and

2.

up to the point of impact,

then lift is linearly reduced

to 10 percent of airplane weight during the first second

after impact, and lift is held constant at ten percent

thereafter.

3. The ground level remains constant. Figures 3-27 through

3-34 show the transient response of the various

variables of interest for the passive and active gear

simulations. Active control in this case reduces the

peak wing/gear force 22 percent below the passive gear

case.

n / PASSIVE GEAR

r

GEAR Ej -\ \ LIMIT FORCE COMMAND z 3 z x 2 10 f? 2 i ’ g LL 0 f? -1 -2 -10 -3 -4 -20 -5 -6 -7 -8 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 TIME -SECONDS FIGURE 3-27 CASE 2 ACTIVE GEAR 0.3 - E 0.2 - ?

s 0.

iFi : O.l- o- 0.6 0.7 0.8 0.9 1.0 1.1 1.2 0 0.1 0.2 0.3 0.4 0.5 TIME -SECONDS FIGURE 3-28 CASE 2 GROUND LEVEL

-- -H -

0 0 -1 -2 -3 : 0.1 -4 -5 : -6 , WING/GE, -\ -7 ; 0.2 -8 -9 -10 -11 0.3 -12 -13

I I I I I I I I I I I

-14

- _

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.9 1.0 1.1 1.2 0.8 TIME -SECONDS FIGURE 3-29 CASE 2 PASSIVE GEAR

-- - ALEGROUND LEVEL- - - - - --

-1 -2

.\

-\

* ‘1

-3 AXLE

E \

t 0.1 \ -4 \ \ Ill -5 \ \ -6 \ WING/GEAR INTERFACE s: \ ii!

.

\ -7 \ : 0.2 \ / -8 \ \ \ -9 \ \ m -10 \ \ \ -11 \ 0.3 \ \ .

-12 ‘\ ‘.

s \ -13 ___-,- --------------w .----,- +- --W--B-- I I I I I I I I -14 0.4 0.8 0.9 1 .o 1.1 1.2 0.3 0.5 0.6 0.7 0 0.1 0.2 TIME - SECONDS FIGURE 3-30 CASE 2 ACTIVE GEAR 6000 - 5000 - m LOWER CYLINDER HYDRAULIC PRESSURE (PI) z 4000 - z E 3000 - UPPER CYLINDER PNEUMATIC PRESSURE (P2) 2000 - 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 U 0.1 TIME -SECONDS P FIGURE 3-31 CASE 2 PASSIVE GEAR CD 6000 - 5000 - LOWER CYLINDER HYDRAULIC PRESSURE (PI) 0” Y UPPER CYLINDER PNEUMATIC PRESSURE (P2) g 4000 - z : n 3000 - I 2000 - I I I I I I I

I I I I

I 0 0.1 0.2 0.3 0.4 0.6 0.5 0.7 0.8 0.9 1.0 1.1 1.2 TIME - SECONDS FIGURE 3-32 CASE 2 ACTIVE GEAR 0.08 0.06 .c 0.04 z F 0.02 g d fh -0.02 2 -0.04 -0.06 -0.08 -0.1 -0.12 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 TIME - SECONDS FIGURE 3-33 CASE 2 ACTIVE GEAR -5 -400 -500 -600 ,I0 -700

-800 L

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 TIME -SECONDS FIGURE 3-34 CASE 2 ACTIVE

3.6.3 Rollout Over Repaired Bomb Crater

_--

Simulation of aircraft rollout over a repaired bomb crater

(subsequent to an impact landing) was accomplished using the nonlinear

vertical drop model. Initial conditions are calculated assuming the

aircraft is in contact with the ground and the landing gear has

reached an equilibrium condition in supporting the aircraft weight

minus its lift. Assuming some horizontal speed for the aircraft,

actual physical changes in ground level can be represented as

transient changes which can be input into the nonlinear model. For

this case a Class I repaired bomb crater was used. This was chosen

because it was the worst-case profile out of all those supplied by

NASA in support of this project. A diagram of the bomb crater is

shown in Figure 3-35. The horizontal speed of the aircraft was

assumed to be 51.8 m/set (170 ft/sec). The command limit force is set

to zero with a force deadband of ,+8.9 kN (22000 lbf) throughout the

transient, consistent with the assumption that the disturbance occurs

during rollout, subsequent to an impact landing. The lift is set to

10 percent of the aircraft weight (per gear) throughout the transient.

Figures 3-36 through 3-43 show the transient response of the various

variables of interest for the passive and active gear simulations.

Active control in this case reduces the peak wing/gear force 74

percent below the passive gear case. Note also from Figures 3-38 and

3-39 that the passive gear leaves the ground three separate times

during the transient, while the active gear leaves the ground only

once, very briefly.

METERS 5 IO I I I I 0 10 20 30 40 50 60 70 HORIZONTAL DISTANCE -FEET FIGURE 3-35. BOMB CRATER PROFILE 300 70

fl

- II

I I

I I

PASSIVE GEAR ACTIVE GEAR S =

-1

/

\

%I -I

1’

\

F -100 -20 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 .o TIME -SECONDS FIGURE 3-36 BOMB CRATER LANDING 0.4 - APTI\,C PCAC) PASSIVE GEAR

f14----

0’

/’

0.3 -

/

E

I’

?

c

0.2 - Li : 8-

bi

7- r 6- E CA 5- n 0.1 - t O- 1 .o 0.1 0.4 0.5 0.7 0.8 0.9 0.2 0.6 TIME -SECONDS FIGURE 3-37 BOMB CRATER LANDING /-\ GROUND LEVEL E o t . .z -2 5!

t ‘.

: \ 5 -4 -0.1 --d 5 \ WING/GEAR INTERFACE ci 2 -6 -I EY -8 -0.2 \ \ -10 -12 -14 -16 -18 0.1 0.5 0.2 0.3 0.4 0.6 0.7 0.8 0.9 1.0 TIME -SECONDS FIGURE 3-38 BOMB CRATER LANDING PASSIVE GEAR 0.2 - 0.1 - E GROUND LEVEL

\

t \ IAXLE

5 2 / \

g o- ti 4 i c--e-N----.----‘--‘- -----,

\J\\/-b-

% WING/GEAR INTERFACE -- -0.1 - -- ---- 4- 4- -6 -7 -0.2 - -8 -9 -10 I I I I I I I I I I -11 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 TIME -SECONDS FIGURE 3-39 BOMB CRATER LANDING ACTIVE GEAR 40,000 30,000 LOWER CYLINDER HYDRAULIC PRESSURE (PI) LOWER CYLINDER HYDRAULIC PRESSURE (PI) h Y u Lu z 3000 5 20,000 ii Lu ! 5 t-2 ! 2000 UPPER CYLINDER PNEUMATIC PRESSURE (P2) UPPER CYLINDER PNEUMATIC PRESSURE (P2) 10,000 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 TIME - SECONDS FIGURE 3-40 BOMB CRATER LANDING PASSIVE GEAR 2000 , 1900 - 1800 - 12,000 1700 - LOWER CYLINDER HYDRAULIC PRESSURE (PI) 1600 - 1500 - 10,000 UPPER CYLINDER PNEUMATIC PRESSURE (P2) / 1400 - : 1300 n 1200 - / ii 1100 -- 1 1000 -- / \ E -- 900 800 z .+ 1’ \ 700 - \ I I 600 - 500 - 400 - 300 - 200 - 100 - I I I I I I I I o- 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 TIME -SECONDS FIGURE 3-41 BOMB CRATER LANDING ACTIVE GEAR 0.1 0.08 n 0.06 .E ? 0.04 z F 0.02 v, i z!5 -0.02 F z-3 -1 < -0.04 > -0.06 G -2 -0.08 L -0.1 -3 -0.

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 .o TIME -SECONDS FIGURE 342 BOMB CRATER LANDING ACTIVE GEAR -200 -400 -600 -800 -1 E3 -1.2E3 -1.4E3 -1.6E3 U 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 TIME -SECONDS FIGURE 3-43 BOMB CRATER LANDING ACTIVE GEAR 4.0 HARDWARE The analog electronic hardware is the same as that designed during the Reference 1 investigation (HR drawing 88000080-201) except for the following circuit changes: c3 ,, 0.001 pF 0.1 pF

T

* c4 0.1 uF Ria 16.2K c5 0.01 /.LF II - Ull R24 u12 R26 2K The original hardware mechanization of Reference 1 did not include provisions for a force deadband. These provisions were subsequently added and consist of the following : -LIMIT R98 R99 !4 FORCE I CMD I COMPUTER 1 “YVCn’

----

r 1

I Rll 20K !6 7; I R22 I I 20K I U6 FORCE FEEDBACK L + w ENABLE

c

R97 10K a+ 68.

5.0 SOFTWARE

The digital software of the system described in Reference 1 was

modified to be compatible with the F-4 landing gear. Changes were

incorporated to reflect the new scaling which was necessitated by the

new weight and strut stroke. The scaling is discussed in detail in

Appendix A.

In addition, program changes made by NASA were incorporated,

including a force deadband which is effective in the takeoff mode as

well as the landing mode.

The software flow chart is shown in Figure 5-l and the complete

program is listed in Appendix B.

6.0 CONCLUSION

An analysis has been made on the active control landing gear

concept applied to the F-4 aircraft. Servocontrol loops and signal

shaping have been defined.

The results of the analysis show that the

active control landing gear can significantly reduce the loads

transmitted to the aircraft for both landing impact cases and rollout

over ground level perturbations. For the vertical drop landing impact

cases analyzed, reductions in wing/gear interface force of 20 to 22

percent were achieved from the conventional passive gear case. For the

case of rollout over a repaired bomb crater,

a reduction of 74 percent

was achieved.

7.0 RECOMMENDATIONS

Based on the conclusion of this report it is recommended that

the study be continued by investigating the following areas:

1. The benefits of the ACLG vs. any penalties involved such

as cost, weight,

and the effect on aircraft structure

and hydraulic systems.

2.

The possibility that under extremely uneven landing

conditions the gear could be depleted of fluid and the

effect of such depletion.

3. Requirements for landing at higher sink rates, i.e., 3.05 m/set (10 ft/sec).

4. The design of a flightworthy ACLG for the F-4 aircraft.

5. The application of the results of this analysis to other

aircraft systems.

a FIGURE 5-l SOFTWARE FLOW CHART

APPENDIX A DIGITAL SCALING Since the stroke of the strut is 0.4034 m (15.88 in) it is anticipated that a (0.51m) potentiometer will be used to measure strut displacement.

It is further anticipated that the wing/gear interface accelerometer will be the same as that used in the system described in Reference 1.

Based on these assumptions the digital scaling is as follows: (1) W/G acceleration: The scale factor of the accelerometer is 2.85 v/g. The accelerometer signal is attenuated to 0.6316 of its value and then amplified by,a factor of 6 in the analog circuitry to produce a scale factor of 10.8 4095 bits the digital acceleration scale factor is: Since 10 v = v/g- 10.8 x 409.5 = 4423 bits/g.

Since the aircraft weight is: 8.184 x lo4 N (18,398 lb) the scale factor in terms of force is: 0.05404 bits/N (0.2404 bits/lb) (2) W/G Velocity: As stated above, the accelerometer scale factor is 2.85 v/g or 2.85~ or: 0.2907 v/m/sec2(0.00738 v/in/sec2) 9.807m/sec2 In the analog circuitry this signal is amplified by a factor of (0.6316)(21.47) = 13.56 and integrated to produce w/g velocity. The velocity scale factor is then: (0.2907)(13.56) = 3.94 v/m/set/ (0.1 v/in/set).

Digitally the scale factor is: (3.94 v/m/sec)(409.5 bits/v) = 1614 bits/m/set (40.95 bits/in/set).

(3) Sink rate The sink rate is scaled at 3.94 v/m/set (0.1 v/in/set) or digitally at 1614 bits/m/set (40.95 bits/in/set) to match the scaling of the w/g velocity signal.

(4) Strut displacement: The strut potentiometer produces 10 v for 0.508 m (20 in).

Its scale factor is then 19.96 v/m. (0.5 v/in).

The potentiometer signal is multiplied by 0.715 in the analog circuitry to produce a scale factor of: 19.96 (0.715) = 14.08 v/m (0.3575 v/in).

Digitally the scale factor is (14.08 v/m (409.5 bits) = 5766 bits/m (146.4 bits/in).

V The maximum strut displacement is equivalent to: (0.4034 m)(5766 bits/m) = 2325 bits which is 0915 HEXADECIMAL (H).

(5) Work potential of the strut: Fwg (Xmax - Xs) = bkwg (Xmax WP = - Xs) If i;wg = 1 g and X max - Xs = 0.0254 m (1 in) then &wg= 8.184 x lo4 N (18,398 lb.)

2079 N-m (18,398 lbf ins) WP is then (8.184 x 104*0.0254 = As pointed out in (1) and (4) above, 1 g is equivalent to: 10.8 v and 0.0254 m (1 in) is equivalent to 0.3575 v.

Digitally then, WP = (10.8 v)(409.5 bits)(0.3575 v)(409.5 bits) = 6.4745 x lo5 bits.

V V The scale factor of WP is therefore: 6.4745~10~ = 3.114x102bits/N-m (35.19 bits/lbf.in) (6) Kinetic Energy: I" ** =$W/g (V tot)2 where V tot KE = V touchdown + o Xwgdt If vtot = 0.0254 m/set (1 in/set) then KE ~$2 (8*184x104N) (0.0254 m/set) 2 = 2.692 Nm (23.83 lb in) (9.807 m/sec2) Digitally, from (2), vtot = (0.0254 m/sec)(3.94 v/m/sec)(409.5 bits/v) = 40.95 bits.

Then KE = (40.95)2 = 1676.9 bits.

Therefore the scale factor for KE is: 1676.9 bits = 622.9 bits/N-m = (70.37 bits/lb in) 2.692 N-m which is twice the scale factor of WP, from (5) above.

This is Therefore, to compare KE to WP it must be divided by 2.

accomplished in the software by a right shift.

(7) Decrease of limit force command during transition: 10 v. corresponds to: 8.184 x lo4 N (18,398 lbsf) of FlI, so that the scale factor of FlI is: 8184 N/v (1840 lbsf/v.)

Digitally the scale factor is: (8184 N/v) = 19.98 bit = 0.05 bit/N (0.22 bit/Ibf) N (4.49 lbf/bit) 409.5 bits/v During transition FlI is decreased at a rate of 4.448105 N/set (lo5 lbf/sec) or digitally at a rate of 2.226 x lo4 bits/set.

(8) Transition velocity (Vt): F112 Vt = 2(W/g)R W = 8.178 x lo4 N (18,398 lb) and R = 4.445 x lo5 (lo5 lb/set) then: F112 = 1.348 x 10-l' FII2 vt = 2(9.178 x 104/9.8)(4.445)105 Therefore: 4.445 N (1 lb) produces: 2.663 x lo-' m/set (1.049 x 10m7in/sec) From (7) the digital scale factor of FII is 0.05 bit N so that the digital signal produced is: (4.445 x 0.05)2 = 0.0494 bits.

The scale factor of Vt is therefore: 0.0494 = 1.86 x lo7 bits/m/set (4.724 x lo5 bits/in/set) 2.663x10-' From (2) and (3) the scale factor for Vtot is: 1614 bits/m/set (40.95 bits/in/set) Therefore, in order to compare Vtot to Vt, Vt must be multiplied = 0.00008669 - 1.885 x lo7 in the arithmetic board which is accomplished as follows: 0.0000869 DECIMAL (D)= 0.0000000000000101101011100110101010101101110000001 Binary (B) which equals: 1.01101011100110101010110 x 2-14(B) The exponent is -14(D) The bias in the arithmetic board is: 07F HEXIDECIMAL (H) or 127 (D) Therefore the number must be applied with a bias of 127 -14 = 113 (D).

In addition, a factor must be applied due to the fact that the numbers from the A/D converter are stored in the most significant 12 bits of the 16 so that the n2mber for Vtot is too high by a facto5 of 16. Vt The net is a function of FL1 and is too high by a factor of (16) .

result is that Vt is too high y a factor of 16. It must therefore be reduced by a factor of 16 or 2 .

Therefore the exponent of the applied number is: 113 - 4 = 109(D) = 6D (H) = 01101101 (B) A sign bit ("0" for positive) must precede the exponent. The format 'of the applied number is: Fraction Sign Exp.

A \ 1011100110101010110 Therefore, if this is stored in memory starting at address M, the contents of memory are: M 36(H) h.li+l J=(H) M+2 CD(H) M+3 56(H)

APPENDIX B

MICROPROCESSOR PROGRAM

The microprocessor program is listed in the following pages.

It should be pointed out that for three-byte instructions, the listing

of the last two bytes is in an order which is reversed from the order

This is a peculiarity of the

in which the bytes are stored in memory.

assembler which was used.

ASSEMBLED AT 0000 MACRO-SO 3.34 04-NOV-79 PAGE 1 ;~************************************/********~**~**** 00001 00002 PROGRAM FOR AN BLECTROHYDRAULIC ACTIVE ; 00003 CONTROL AIRCRAFT LANDING GEAR ;********************************************~********* 00004 00005 NOTES: ; 00006 ; RAM LOCATION BDOEH ADDED AS A TE?rQ' LOC 00007 FOR FLIM 2/13/80 ; ;**************************************************~*** 00008 00009 ; REVISED FOR F4 GEAR 6/28/81 00010 ORG 00 0000' F3 00011 START: DI ;DISABLE INTERRUPTS 0001' 21 3FFF 00012 LX1 H,3FFFH ;INIT. STACK 0004' F9 00013 SPHL 0005 3E a2 00014 WI A,82H ;INIT. MATH BOARD D3 EB 0007' 00015 OUT OEBH 0009' 3E 00 00016 MVI A,00 ;SET MEM. BASE ADD.

OOOB D3 Al 00017 OUT OAlH OOOD' 3E 80 00018 WI A,80H OOOF' D3 A2 00019 OUT OA2H 0011' 21 0092 00020 LX1 H,0092H ;STRUT THRESH.=1 IN, 00021 ;MULT THRESH BY 16 0014' CD 0289' 00022 CALL ANM ;FOR LATER USE 22 3F8A 0017' 00023 SHLD 3F8AH :LABLE BXTHR OOlA' 3E 4C 00024 MVI A,4CH ;SET LIGHTS,SWITCHES OOlC' D3 EA 00025 OUT OEAH ;****************************************************** 00026 00027 OUTPUT MUXO-MUX4 FOR A/D BOARD CHECK 00028 ALSO LOOK FOR CONTROLLER ENABLED ;*********t******************************************** 00029 OOlE' 16 03 00030 TLl: MVI D,3 0020' 06 FF 00031 B,OFFH TL2: NV1 0022' OE 05 00032 WI C,5 0024' 7A 00033 TL3: NOV A,D 0025' CD 0251' 00034 CALL IN1 0028' 22 F708 00035 ;OUTPUT TO DACO SHLD OF708H 002B' DE E9 00036 IN OE9H :CONTROLLER ENABLED?

002D' 1F 00037 RAR 002E' DA 0042' 00038 JC Ll ;YES,JUMP TO Ll 00039 B 0031' 05 DCR C2 0024' 00040 0032' JNZ TL3 0035' 06 FF 00041 WI1 B.OFFH 0037' OD 00042 DCR C' 0038' C2 0024' 00043 JNZ TL3 003B' 15 00044 D DCR 003c FA OOlE' 00045 JM TLl 003F' c3 0020' 00046 JMP TL2 MACRO-80 3.34 04-NOV-79 PAGE l-l ;****************************************************** 00047 00048 CONTROLLER HAS BEEN ENABLED ; ;*****,************************************************ 00049 0042' 3E 02 00050 Ll: MVI A.02 0044' CD 0251' 00051 CALL IN1 ;GET STRUT POS FOR LAND/TO. DEC.

;GET STRUT THRESHOLD 0047' 2A 3FaA 00052 LHLD 3F8AII 00053 004A' EB XCHG :PUT IN DE 004B' 2A 3F86 00054 LHLD 3FB6H ,L~AD HL WITH STRUT POSITION 004E' CD 0282' 00055 CALL SUB2 ;CALC. THRESHOLD-STRUT 0051' DA OlBD 00056 JC L12A ;YES, JUMP TO 12A :***************************************************** 00057 00058 LANDING - MAKE PREPARATIONS ; ~***************************************************** 00059 0054' 3E 03 00060 NV I A,03 0056' CD 0251' 00061 CALL IN1 ;GET SINK RATE 0059 ' 22 3F88 00062 SHLD 3F88II ;STORE IT 005C' 21 0915 00063 LX1 H,0915H ;MULT XMAX BY 16 TO SHIFT INTO 005F' CD 0289' 00064 CALL ANM ;UPPER 12 BITS 0062' 22 3F8C 00065 SHLD 3F8CH ;STORE IT ;***************************************************** 00066 00067 ENABLE INTEGRATOR 00068 START ENERGY CALCULATIONS ;***************************************************** 00069 0065' 3E 9E 00070 MVI A,SEH 0067' D3 EA 00071 OUT OEAH ;ENABLE INTEGRATOR 0069' CD 0220' 00072 IN3 L8: CALL 006C EB 00073 XCHG 2A 3F8C 006D' 00074 LHLD 3F8CH 0070' EB 00075 XCHG 0071' 7B 00076 NOV A,E 0072' 95 00077 SUB L 0073' 6F 00078 NOV L,A 0074' 7A 00079 MOV A,D 0075' 9c 00080 SBB H 0076' 67 00081 NOV H,A 0077' 22 8004 00082 SHLD 8004H 007A' AF 00083 XRA A CD 028E' 00084 CALL MATH 007B' 2A 8000 00085 LHLD 8000H 007E' 3F8EH 0081' 22 3F8E 00086 8002H 0084' 2A 8002 00087 LHLD 0087' 22 3F90 00088 SHLD 3F90H 3F88H 008A' 2A 3F88 00089 LHLD 008D' EB 00090 XCHG 3FS4H 008E' 2A 3F84 00091 LHLD 0091' CD 0282' 00092 CALL SUB2 .I MACRO-80 3.34 04-NOV-79 PAGE l-2 22 8000 0094' 00093 SHLD 8000H 0097' 22 8004 00094 SHLD 0004H 009A' AF 00095 XRA A 009B' CD 028E' 00096 CALL MATH ***************************+*+*+*************************** 00097 00098 DIVIDE KE BY 2 THEN DO A BYTE BY BYTE COMPARE 00099 TO TEST IF PE)KE. DON'T BOTHER TO TEST LSB-IT 00100 CONTAINS NO USEFUL DATA ***************************************************** 00101 009E' B7 00102 ORA A ;CLEAR CARRY 009F' 06 03 00103 MVI ;SET A BYTE COUNTER B,3 OOAl' 21 8003 00104 LX1 H,8003H ;GBT KINETIC ENERGY OOA4' 7E 00105 MOV A,M ;SHIFT RIGHT 3 BYTES AND L8A: OOA5' 1F 00106 RAR :RE-SAVE OOA6' 77 00107 MOV N , A OOA7' 2B 00108 DCX II OOAS' 05 00109 DCR B OOA9' c2 00114' 00110 JNZ LSA OOAC' 06 03 00111 MVI B,03 OOAE' 21 3F91 00112 LX1 H,3FDlH OOBl' 11 8003 00113 LX1 D,8003H OOB4' 1A 00114 L9: LDAX D 00115 hi OOB5' BE CMP OOBG' c2 OOC2' 00116 JNZ LlO 00117 OOB9' 1B DCX D 00118 OOBA' 2B DCX H 00119 OOBB' 05 DCR B 00120 OOBCf C2 OOB4' JNZ L9 00121 OOBF' c3 OOC5' JMP Lll 00122 OOC2' D2 0069' LlO: JNC LB ~***************************************************** 00123 00124 TIME TO INITIATE ACTIVE CONTROL ~***************************************************** 00125 00126 OOC5' 2A 3F80 Lll: LHLD 3FBOH 00127 OOCS' 22 F70A SHLD OFPOAH 00128 OOCB' 22 3DOE SHLD 3DOEH ;SAVE ORIGINAL "FLIM" 00129 OOCE' EB XCHG ;FLIH TO DE FOR COMPARE 00130 OOCF' CD 0220' CHACEL: CALL IN3 ;GET W/G ACCEL.

00131 OOD2' 2A 3F80 LHLD BFSOH ;PUT NEW ACCEL INTO HL 00132 OOD5' CD 0282' CALL SUB2 ;DE-HL IS NEW W/G ACCEL.

00133 ;GREATER THAN FLIM?

00134 OODS' F2 OOCF' JP CHACEL ;NO-LOOP TILL IT IS 00135 :CALL SPTH ;HAS GEAR STARTED STROKE?

(OODB-OOEO) = 00 (NCP) 00136 ;JP CHACEL ;LOOP TILL GEAR ) THRESHOLD 00137 OOEl' 3E 9F MVI A,SFH 00138 D3 EA ;ENABLE SERVOLOOP OOE3' OUT OEAH MACRO-80 3.34 04-NOV-79 PAGE l-3 00139 00140 GEAR IS NOW UNDER ACTIVE CONTROL r****************************************************** 00141 OOE5' 2A 3DOE 00142 LHLD SDOEH ;GET ORIGINAL FLIM TO CALCULATE OOE8' 22 8000 00143 SHLD SOOOH ;TRANSITION VELOCITY OOEB' 21 0000 00144 LX1 H,0000 OOEE' 22 8002 00145 SHLD 8002H OOFl' 3E 08 00146 MVI A.08 OOF3' CD 028E' 00147 CALL MATH OOF6' 3E 06 00148 MVI A.06 OOFS' CD 028E' 00149 CALL MATH OOFB' 3E 36 00150 MVI A,36H OOFD' 32 8004 00151 STA S004H 0100 ' 3E B5 00152 MVI A,OBSH 0102' 32 8005 00153 STA 8005H 0105' 3E CD 00154 MVI A,OCDH 0107' 32 8006 00155 STA 8006H OlOA' 3E 56 00156 WV1 A,56H OlOC' 32 8007 00157 STA 8007H OlOF' 3E 02 00158 MVI A,02 0111' CD 028E' 00159 CALL MATH 0114' 2A 8000 00160 LHLD SOOOH 0117' 22 3F92 00161 SHLD 3392H OllA' 2A 8002 00162 LHLD 8002H 0111)' 22 3F94 00163 SHLD 3F94II :****************************************************** 00164 00165 TRANSITION VELOCITY STORED AS FLOATING PT,32 BIT 00166 NUMBER. START COMPARING THIS AGAINST (SINE RATE 00167 -W/G VEL.) TO DETERMINE START OF TRANSITION ;****************************************************** 00168 0120' 2A 3F88 00169 L4: LHLD 3F88H 0123' EB 00170 XCIIG 0124' 3E 00 00171 WI A,00 0126' CD 0251' 00172 CALL IN1 0129' CD 0282' 00173 CALL sUi32 012c 22 8000 00174 SHLD SOOOH 012F' 21 0000 00175 LX1 H,OOOO 0132' 22 8002 00176 SHLD 8002H MVI 0135' 3E 08 00177 A.08 0137' CD 028E' 00178 CALL NAT11 013A' 2A 3F92 00179 LHLD 3F92H 013D' 22 8004 00180 SHLD 8004H 0140' 2A 3F94 00181 LHLD 3F94H 0143' 22 8006 00182 SHLD 8006H 0146' 3E OA MVI 00183 A,OAH 0148' CD 028E' 00184 CALL NAT11 MACRO-80 3.34 04-NOV-79 PAGE l-5 OlB3' 3E 9D 00231 L14: MVI A,9DH OlB5' D3 .EA 00232 OUT OEAH :CLOSE FORCE FEEDBACK OlB7' LX1 B,lSOOH iSET BC TO 1600 LBS 01 1800 00233 OlBA' c3 017F' 00234 JNP L15 00235 .****************************************************** , 00236 ; TAKEOFF MODE ~****************************************************** 00237 OlBD' 21 0000 00238 i12A: LX1 H,OOOO OlCO' 22 F70A 00239 SHLD ;SET LIMIT FORCE CMD='O LBS.

OF70AH OlC3' 3E A9 00240 MVI A,OASH OlC5' D3 EA 00241 OUT OEAH ;ENABLE SERVOLOOP & OPEN F FDBK OlC7' CD 020E' 00242 FLOA: CALL SPTH ;CHECK STRUT POSITION OlCA' F2 OlC7' JP 00243 FLOA OlCD' 01 1EEO 00244 LX1 B,lEEOH ;SET l3C TO 2000 LBS OlDO' CD 0220' 00245 L15A: CALL IN3 OlD3' 2A 8000 00246 LHLD SOOOH F708 OlD6' 22 00247 SHLD OF708H ;OUTPUT W'IIG ACCEL TO DACO OlD9' CD 027D' 00248 CALL FTEST OlDC' D2 OlFE' 00249 JNC L13A OlDF' 01 lEE0 LX1 ;SET BC TO 2000 LBS 00250 B,lEEOH OlE2' L16A: CD 0266' 00251 CALL IN4 OlE5' 22 F708 00252 SHLD OF708H ;OUTPUT WIG ACCEL TO DACO OlE8' CD 027D' 00253 CALL FTEST OlEB' DA OlBD' 00254 JC L12A OlEE' 21 lEE0 00255 H,lEEOH LX1 ;SET HL TO 2000 LBS OlFl' 3E A5 00256 A.OASH NV1 ;CLOSE F FDBK & REVERSE SIGN OlF3' D3 EA OEAH OUT :OF LIFtIT FORCE CMD (ANALOG) 00257 OlF5' ;SET LIMIT FORCE CMD=2000 L&S 22 F70A OF70AH SHLD 00258 ;SET BC TO 1600 LBS OlF8' 01 1800 B,lSOOH LX1 00259 OlFB' C3 OlE2' LlGA JMP 00260 OlFE' 21 lEE0 H,lEEOH LX1 00261 L13A: ;SET HL TO 2000 LBS 0201' ;SET LIMIT FORCE CMD=2000 LBS 22 F70A OF70AH SHLD 00262 0204' 3E AD A,OADH MVI 00263 L14A: 0206' D3 EA 00264 OEAH OUT ;CLOSE FORCE FEEDBACK 0208' 01 1800 00265 B,1800H LX1 ;SET EC TO 1600 LBS 020B' C3 OlDO' 00266 L15A JMP ~****************************************************** 00267 00268 ; ROUTINE TO SUBTRACT STRUT POS'N FROM THRESHOLD ;****************************************************** 00269 020E' E5 SPTH: PUSH H ;SPTH SETS SIGN FLAG POSITIVE 00270 020F' D5 00271 PUSH D ;UNTIL STRUT POS'N ) THRESHOLD 0210' CD 024F' 00272 CALL STP ;GET STRUT POSITION 0213' 21 OB20 00273 LX1 H,OB20H ;THRESIIOLD 0160H=.05" 02DOH=.l" 00274 ; 0590H=.2" 00275 ; 00276 ; OB20H=.4" I - MACRO-80 3.34 04-NOV-79 PAGE l-4 014B' DB Al 00185 IN OAlH 014D' E6 20 00186 AN1 20H 014F' CA 0120' 00187 JZ L4 :***************************************************** 00188 00189 TRANSITION PHASE ;***************************************************** 00190 0152' 2A 3DOE 00191 LHLD 3DOEH ;FLIM 0155' 11 FFFE 00192 LX1 D,OFFFEII 0158' 22 F70A 00193 L5: SHLD OF70AH 19 00194 015B' DAD D 00195 ;ClIECK (THRESH.-STRUT POS'N) 015C' CD 020E' EXST: CALL SPTH F2 016C' Od196 015F' JP L12 0162' 01 1BDO 00197 LX1 B,lBDOH 0165' 7D 00198 MOV A,L 00199 0166' 91 SUB C 0167' 7c 00200 NOV A,H 0168' 98 00201 SEE B 0169 ' D2 0158' 00202 JNC L5 ~****************************************************** 00203 00204 ROLLOUT PHASE ~****************************************************** 00205 016C' 21 0000 00206 i12: HI0000 LX1 016F' 22 F70A 00207 OF70AI-I :SET FLC=O LBS. SHLD 0172' 3E 99 00208 MVI A,99H ' 0174' D3 EA 00209 OEAH ;OPEN FORCE FEEDBACK OUT CD 020E' 00210 FLO: CALL SPTH ;CHECK STRUT POS'N.

0176' F2 0176' 00211 JP FL0 0179' B,lEEOII ;SET BC TO 2000 LBS.

017C' 01 lEE0 00212 LX1 IN3 017F' CD 0220' 00213 CALL L15: 0182' 2A 8000 00214 LHLD SOOOH 0185' 22 F708 00215 SHLD OF708H :OUTPUT W/G ACCEL. TO DACO 0108' CD 027D' 00216 CALL FTEST 018B' D2 OlAD' 00217 JNC L13 018E' 01 lEE0 00218 LX1 B,lEEOH ;SET BC TO 2000 LBS.

0191' CD 0266' 00219 CALL L16: IN4 0194' 22 F708 00220 SHLD OF708II ;OUTPUT W/G ACCEL TO DACO CD 027D' 00221 CALL FTEST 0197' 019A' DA 016C' 00222 JC L12 21 1EEO 00223 H,lEEOH ;SET HL TO 2000 LBS.

019D' LX1 ;CLOSE F FDBK & REV. SIGN OlAO' 3E 95 00224 MVI A,95H 00225 ;OF LIMIT FORCE CMD (ANALOG) OlA2' D3 EA OEAH :SET LIMIT FORCE MD=2000 LBS OlA4' 22 F70A 00226 OF70AH SHLD OlA7' 01 1800 00227 LX1 B,~~OOH ~SET BC ~0 1600 LBS OlAA' c3 0191' 00228 JMP L16 OlAD' 21 lEE0 00229 L13: LX1 H,lEEOR ;SET HL TO 2000 LBS 22 F70A 00230 SHLD OF70AH ;SET LIMIT FORCE CMD=2000 LBS OlBO' MACRO-80 3.34 04-NOV-79 PAGE l-6 0216' EB 00277 XCHG ;GET STRUT POSITION 0217' 2A 3F86 00278 LHLD 3F86H 021A' CD 0282' 00279 CALL SUB2 :SUBTRACT STRUT FROM THRESH.

021D' Dl 00280 POP D 021E' El 00281 POP H 021F' C9 00282 RET ;****************************************************** 00283 00284 ROUTINE TO INPUT AND STORE DATA FROM MUXO,l & 2 ; .*****************************+***************** 00285 0220' 3E 01 00286 iN3: IV1 A,01 0222' 21 F701 00287 LX1 H,OF701H 0225' 77 00288 MOV N , A 0226' 29 00289 DCX H 0227' 36 01 00290 MVI M,Ol 0229’ 7E 00291 Ml : !dOV A,M 0226' 07 00292 RLC 0229' D2 0229’ 00293 JNC Ml 022E' 36 00 MVI 00294 N , 00 0230' 2A F704 00295 LHLD OF704H 0233' 22 8000 00296 SHLD SOOOH 0236' 22 3F80 00297 SHLD 3F80H 0239’ 3E 00 00298 MVI A,00 023B' 21 F701 00299 LX1 H,OF701H 023E' 77 00300 MOV AI, A 023F' 2B 00301 DCX H 0240' 36 01 00302 MVI hI,Ol 0242' 7E 112: NOV 00303 A, M 0243' 07 00304 RLC 0244' D2 0242' 00305 JNC M2 0247' 36 00 00306 MVI M,OO 0249 ’ 2A F704 00307 LHLD OF70411 024C' 22 33?84 00308 SHLD 3F84H 024F' 3E 02 00309 ST-P: MVI A.02 0251' 21 F701 00310 INl: LX1 H,OF701H 0254' 77 00311 MOV M,A 0255' 2B 00312 DCX 11 0256' 36 01 00313 MVI B4,Ol 0258' 7E 00314 M3: MOV A, M 0259' 07 00315 RLC 025A' D2 0258' 00316 JNC 13 025D' 36 00 00317 IV1 M,OO 025F' 2A F704 00318 LHLD OF704H 0262' 22 3F86 00319 SHLD 3F86H 0265' C9 00320 RET ;****************************************************** 00321 00322 ROUTINE TO INPUT AND STORE DATA FROM MUX4 ;

I -

MACRO-80 3.34 04-NOV-79 PAGE 1-7 ;****************************************************** 00323 0266' 3E 04 00324 IN4: MVI A.04 0268' 21 F701 00325 LX1 H,OF701II 026B' 77 00326 MOV 14 ,A 026C' 2B 00327 DCX II 026D' 36 01 00328 MVI M,Ol 026F' 7E 00329 M4: MOV A.M 0270' 07 00330 RLC 0271' D2 026F' 00331 JNC M4 0274' 36 00 00332 WI M,OO 0276' 2A F704 00333 LHLD OF704H 0279 ' 22 3F96 00334 SHLD 3F96H 027C' c9 00335 RET ;*********************************t********************* 00336 00337 ROUTINE TO SUBTRACT BC FROM HL ;*t**************************************************** 00338 027D' 7D 00339 FTEST: MOV A,L 027E' 91 00340 SUB C 027F' 7c 00341 MOV A ,H 0280' 98 00342 SBB B 0281' c9 00343 RET ;**********t******************************************* 00344 00345 ROUTINE FOR DOUBLE PRECISION SUBTRACT 00346 HbDE-HL ;*********t******************************************** 00347 0282' 70 00348 SUBP: MOV A,E 0283' 95 00349 SUB L 0284' 6F 00350 MOV L,A 0285' 7A 00351 MOV A,D 0286' 9c 00352 SBB H 0287' 67 00353 MOV H,A 0288' c9 00354 RET ;*************t**************************************** 00355 00356 ROUTINE TO SHIFT VALUE IN HL LEFT 4 PLACES ;****************************************************** 00357 0289' 29 00358 ANM: DAD H 028A' 29 00359 DAD H 028B' 29 00360 DAD H 028C' 29 00361 DAD II 028D' c9 00362 RET :****************I*********+**t***t******************** 00363 00364 ROUTINE TO ACTIVATE MATH BOARD & WAIT FOR RESULT ; 00365 ACCUMULATOR HAS OPCODE ; :*************************************t*************** 00366 028E' D3 A0 00367 MATH: OUT OAOH 0290' DB A7 00368 WAIT: IN OA7H MACRO-80 3.34 04-NOV-79 PAGE l-8 E6 01 00369 0292 ’ AN1 01 0294’ c2 0290' 00370 JNZ WAIT 0297’ c9 00371 RET ;****************************************************** 00372 .****************************************************** 00373 00374 THE FOLLOWING ARE SPECIAL CHECK-OUT ROUTINES 00375 AND NOT PART OF THE MAIN PROGRAM ;****************************************************** 00376 ;****************************************************** 00377 00378 ; 00379 , .****************************************************** 00380 00381 ROUTINE TO INPUT A VALUE FROM A/D & STORE IN RAM ;****************************************************** 00382 0298 ’ F3 00383 DI 0299’ 3E 00 00384 MVI A.00 029B' CD 0251' 00385 CALL IN1 CF 00386 029E' RST OlH 029F' 00 00387 NOP 02AO' 00 00388 NOP ************************************************ 00389 , 00390 ROUTINE TO DO PGA TEST ON A/D :****************************************************** 00391 02Al' F3 00392 DI 02A2' 21 F701 00393 LX1 H,OF701H 00394 02A5' 36 00 PGA: MVI hl,OO 02A7' 36 CO 00395 MVI EI, OCOH 02A9' C3 02A5' 00396 JMP PGA 00397 02AC' 00 NOP ;****************************************************** 00398 00399 ROUTINE TO OUTPUT A VALUE TO DACO & DACl ;********************************tS**************** 00400 F3 00401 DI 02AD' 02AE' 00 00402 NOP 02AF' 21 0000 00403 R2: LX1 H,OOOO 02B2' 22 F708 00404 SHLD OF708H 00405 02B5' 22 F70A SHLD OF70AH 02B8' 00 00406 NOP 02B9' 00 00407 NOP 02BA' 00 00408 NOP 02BB' C3 02AF' 00409 JMP R2 00410 END MACRO-80 3.34 04-NOV-79 PAGE S MACROS: SYMBOLS: EXST ANM 0289 ’ CHACEL OOCF' 015c FLC 0176' FLOA OlC7' FTEST 027D' IN1 0251' IN3 0220' IN4 0266' Ll 0042' LlO OOC2' OOC5' Lll L12 OlBD' 016C' L12A L13 OlAD' L13A OlFE' L14 OlB3' L14A 0204' L15 017F' L15A OlDO' L16 0191' LlGA OlE2' L4 0120' 0158' L8 0069 ' L8A OOA4' L9 OOB4' M"s 0229' M2 0242' M3 0258' M4 026F' MATH 028E' PGA 02A5' R2 02AF' SPTH 020E' START 0000 ' STP 024F' 0282' TLl SUB2 OOlE' TL3 0020' TL3 0024' WAIT 0290' NO FATAL ERROR(S) ...--. . ... . . .

. ,.. .

ASSEMBLED AT 3DlO MACRO-80 3.34 04-NOV-79 PAGE 1 ****************************************************** 00001 00002 PROGRAM FOR AN ELECTROHYDRAULIC ACTIVE 00003 CONTROL AIRCRAFT LANDING GEAR ****************************************************** 00004 00005 NOTES: 00006 RAM LOCATION 3DOEH ADDED AS A TEMP LOC 00007 FOR FLIM 3/13/80 ;****************************************************** 00008 00009 ; REVISED FOR F4 GEAR 6/28/81 00010 ORG 3DlOH 3DlO' F3 00011 START: DI ;DISABLE INTERRUPTS 3Dll' 21 3FFF 00012 LX1 II,JFFFII ;INIT. STACK 3D14' F9 00013 SPHL 3D15' 3E 82 00014 UVI A.82H :INIT. MATH BOARD 3D17' D3 EB 00015 OUT O&H ' 3D19' 3E 00 00016 MVI A,00 ;SET MEM. BASE ADD.

3DlB' D3 Al 00017 OUT OAlII 3DlD' 3E 80 00018 MVI A\8001 3DlF' D3 A2 00019 OUT OA2H 3D21' 21 0092 00020 H,OO92II ;STRUT THRESH.=1 IN.

LX1 00021 ;IlULT THRESH BY 16 3D24' CD 3F99' 00022 CALL ANM :FOR LATER USE 3D27' 22 3F8A 00023 SHLD BFSAII ; LABLE BKTHR ;SET LIGHTS,SWITCHES 3D2A' 3E 4C 00024 EfVI A,4CII 3D2C' D3 EA 00025 OUT OEAH ;****************************************************** 00026 00027 OUTPUT HUXO-MUX4 FOR A/D BOARD CHECK 00028 ALSO LOOK FOR CONTROLLER ENABLED :****************************************************** 00029 3D2E' 16 03 00030 TLl: MVI D'3 3D30' 06 FF 00031 TL2: MVI B,OFRI 3D32' OE 05 00032 WI C'5 3D34' 7A 00033 TL3: MOV A,D 3D35' CD 3F61' 00034 CALL I Nl 3D38' ;OUTPUT TO DACO 22 F708 00035 SHLD OF708II 3D3B' IN ;CONTROLLER ENABLED?

DB E9 00036 OE9H RAR 3D3D' 1F 00037 3D3E' DA 3D52' 00038 JC Ll ;YES,JUMP TO Ll 3D41' 05 00039 DCR B 3D42' C2 3D34' 00040 JNZ TL3 3D45' 06 FF 00041 MVI B.OFFH 3D47' OD 00042 DCR C- 3D48' C2 3D34' 00043 JNZ TL3 3D4B' 15 00044 DCR D 3D4C' FA 3D2E' 00045 JM TLl 3D4F' 00046 JMP TL2 C3 3D30' MACRO-80 3.34 04-NOV-79 PAGE l-l 00047 00048 CONTROLLER HAS BEEN ENABLED :****************************************************** 00049 A,02 3D52' 3E 02 00050 il: MVI 3D54' CD 3F6l' 00051 CAL.L IN1 ;GET STRUT POS FOR LAND/TO. DEC.

3D57' 2A 3F8A 00052 LHLD 3F8AH ;GET STRUT THRESHOLD 3D5A' EB 00053 XCHG ;PUT IN DE 3D5B' 2A 3F86 00054 LHLD 3F86II ;LOAD HL WITH STRUT POSITION 3D5E' CD 3F92' 00055 CALL SUB2 ;CALC. THRESHOLD-STRUT 3D61' DA SECD' 00056 JC L12A ;YES, JUMP TO 12A .****t**t+*****t+*t*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 00057 00058 LANDING - MAKE PREPARATIONS ;+*$*,*****,***t*~****t+***+******t*+***~~~~~~~~~~~~~~ 00059 3D64' 3E 03 00060 MVI A,03 3D66' CD 3F61' 00061 CALL IN1 ;GET SINK RATE 3D69' 22 3F88 00062 SHLD 3F88II ;STORE IT 3D6C' 21 0915 00063 LX1 H,0915H ;MULT XMAX BY 16 TO SHIFT INTO 3DGF' CD 3F99' 00064 CALL ANM ;UPPER 12 BITS 3D72' 22 3F8C 00065 SHLD 3F8CH ;STORE I?

;***************************************************** 00066 00067 ENABLE INTEGRATOR 00068 START ENERGY CALCULATIONS :*******,***+~+**~****t*****$*+*+***++t*~~~~~~~~~~~~~~ 00069 3D75' 3E 9E 00070 MVI A,SEH 3D77' D3 EA 00071 OUT OEAH ;ENABLE INTEGRATOR 3D79' CD 3F30' CALL IN3 00072 L8: 3D7C' EB 00073 XCHG 3D7D' 2A 3F8C 00074 LHLD 3F8CH 3D80' EB 00075 XCHG 3D81' 7B 00076 MOV A,E 3D82' 95 00077 SUB L 3D83' 6F 00078 FhOV L,A 3D84' 7A 00079 Alov A,D 3D85' 9C II 00080 SBB MOV 3D86' 67 00081 H,A 3D87' 22 8004 00082 SHLD B004H 3D8A' AF 00083 XRA A 3DBB' CD 3F9E' 00084 CALL MATH 3D8E' 2A 8000 00085 LHLD 8000H 3D91' 22 3F8E 00086 SHLD 3F8EH 3D94' 2A 8002 00087 LHLD 8002H 3D97' 22 3F90 00088 SHLD 3F90H 3D9A' 2A 3F88 00089 LHLD 3F88H 3D9D' EB 00090 XCHG 2A 3F84 LHLD 3F84H 3D9E' 00091 CALL SUB2 3DA1' CD 3F92' 00092 MACRO-80 3.34 04-NOV-79 PAGE l-2 3DA4' 22 8000 00093 SHLD 8000H 3DA7' 22 8004 00094 SHLD 8004H SDAA' AF 00095 XRA A 3DAB' CD 3F9E' 00096 CALL MATH ;t**************************************************** 00097 00098 DIVIDE KE BY 2 THEN DO A BYTE BY BYTE COMPARE 00099 TO TEST IF PE)KE. DON'T BOTHER TO TEST LSB-IT 00100 CONTAINS NO USEFUL DATA ;***t************~**+*******t***********~~*~~*~**~~~~* 00101 SDAE' B7 00102 ORA A ;CLEAR CARRY 3DAF' 06 03 00103 MVI ;SET A BYTE COUNTER B'3 3DBl' 21 8003 00104 LX1 H,8003H :GET KINETIC ENERGY 3DB4' 7E 00105 L8A: MOV A _1.1 :SHIFT RIGHT 3 BYTES AND 3DB5' 1F 00106 RAR ;RE-SAVE 3DB6' 77 00107 thov El, A 3DB7' 2B 00108 DCX H 3DB8' 05 00109 DCR B 3DB9' C2 3DB4' 00110 JNZ L8A 3DBC' 06 03 00111 MVI B,03 SDBE' 21 3F91 00112 LX1 H,3F91H 3DCl' 11 8003 00113 LX$ D,8003H 3DC4' 1A 00114 LDAX D L9: 3DC5' BE 00115 CMP 11 C2 3DD2' 00116 3DC6' JNZ LlO 3DC9' 1B 00117 DCX D

3DCA' 2B 00118 ncx H

SDCB' 05 00119 DCR B 3DCC' C2 3DC4' 00120 L9 C3 3DD5' 3DCF' 00121 Lll 3DD2' D2 3D79' 00122 LlO: JNC L8 ;*********t******************************************* 00123 00124 TIME TO INITIATE ACTIVE CONTROL ;*********************~******************************* 00125 3DD5' 2A 3FSO 00126 Lll: LHLD 3F80H 3DD8' 22 F70A 00127 SHLD OFi'OAH 3DDB' 22 3DOE 00128 SHLD BDOEH ;SAVE ORIGINAL "FLIM" SDDE' EB 00129 XCHG ;FLIM TO DE FOR COMPARE SDDF' CD 3F30' 00130 CHACEL: CALL I N3 ;GET W/G ACCEL.

3DE2' 2A 3FBO 00131 LHLD 3P8OH ;PUT NEW ACCEL INTO HL 3DE5' CD 3F92' 00132 CALL ;DE-HL IS NEW W/G ACCEL.

SUB2 00133 ;GREATER THAN FLIM?

3DE8' F2 SDDF' 00134 JP CHACEL ;NO-LOOP TILL IT IS 00135 ;CALL ;HAS GEAR STARTED STROKE?

(3DEB-3DFO) = 00 (NOP) SPTH ;JP ;LOOP TILL GEAR ) THRESHOLD 00136 CHACEL 00137 MVI 3DFl' 3E 9F A,SFH 3DF3' D3 EA 00138 OUT OEAH ;ENABLE SERVOLOOP MACRO-80 3.34 04-NOV-79 PAGE l-3 .***************************************************~**** 00139 00140 GEAR IS NOW UNDER ACTIVE CONTROL ;****************************************************** 00141 3DF5' 2A 3DOE 00142 LHLD SDOEH ;GET ORIGINAL FLI?J TO CALCULATE 3DF8' 22 8000 00143 SHLD 8000H :TRANSITION VELOCITY 3DFB' 21 0000 00144 LX1 H,OOOO ' SDFE' 22 8002 00145 SHLD 8002H 3E 08 3EOl' 00146 MVI A,08 3E03' CD 3F9E' 00147 CALL MATH 3E06' 3E 06 00148 MVI A.06 3E08' CD 3F9E' 00149 CALL MATH 3EOB' 3E 36 00150 MVI A,36H 3EOD' 32 8004 00151 STA 8004II 3ElO' 3E B5 00152 MVI A,OB5H 3E12' 32 8005 00153 STA 8005H 3E15' 3E CD 00154 MVI A,OCDH 3E17' 32 8006. 00155 STA 8006H 3ElA' 3E 56 00156 MVI A,56H 3ElC' 32 8007 00157 STA 8007H 3ElF' 3E 02 00158 MVI A.02 3E21' CD SFDE' 00159 CALL MATH 3E24' 2A 3000 00160 LHLD 80OOH 3E27' 22 3F92 00161 SHLD 3F92H 3E2A' 2A 8002 00162 LHLD 8002II 3E2D' 22 3F94 00163 SHLD 3F94H :****************************************************** 00164 00165 TRANSITION VELOCIT'I STORED AS FLOATING PT,32 BIT START COMPARING THIS AGAINST (SINK RATE 00166 NUMBER.

00167 -W/G VEL.) TO DETERMINE STAR? OF TRANSITION ~****************************************************** 00168 3E30' 2A 3F88 00169 i4: LHLD 3F88H 3333' EB 00170 XCHG 3334' 3E 00 00171 MVI A,00 3E36' CD 3F61' 00172 CALL IN1 3E39' CD 3F92' 00173 CALL SUB2 3E3C' 22 8000 00174 SHLD DOOOH 3E3F' 21 0000 GO175 LX1 I! .oooo 3E42' 22 8002 00176 SHLD 8002H 3E45' 3E 08 00177 MVI A,08 3E47' CD 3F9E' CALL MATH 00178 3E4A' 2A 3F92 00179 LHLD 3F92H 3E4D' 22 8004 00180 SHLD 8004H 3E50' 2A 3F94 00181 LHLD 3F94H 3E53' 22 8006 00182 SHLD 8006H 3356' 3E OA 00183 MVI A,OAH 3358' CD 3F9E' 00184 CALL MATH MACRO-80 3.34 04-NOV-79 PAGE l-4 3E5B' DB Al 00185 IN OAlII 3E5D' E6 20 00186 AN1 2OII 3E5F' CA 3E30' 00187 JZ L4 :***************************************************** 00188 , 00189 TRANSITION PHASE ; ;*****************)************************************* 00190 3362' 2A 3DOE 00191 LHLD BDOEII ;FLIM 3E65' 11 FFFE 00192 LX1 D.OFFFEH 3368' 22 F70A 00193 L5: SHLD OF70AH 3E6B' 19 00194 DAD D 3E6C' CD 3FlE' 00195 EXST: CALL SPTH :CHECK (THRESH.-STRUT POS'N) 3E6F' F2 3E7C' 00196 JP L12 3372' 01 lBD0 00197 LX1 B.lBDOII 3375' 7D 00198 NOV A;L 3376' 91 00199 SUB C 3E77' 7c 00200 MOV A,H 3378' 98 00201 SBB B 3E79' D2 3368' 00202 JNC L5 ~****************************************************** 00203 00204 ROLLOUT PHASE ;****************************************************** 00205 3E7C' 21 0000 00206 L12: LX1 H,0000 3E7F' 22 F70A 00207 SHLD OF70AH :SET FLC=O LBS.

00208 En'1 A,99H 3E82' 3E 99 OEAH ;OPEN FORCE FEEDBACK 3384' D3 EA 00209 OUT CD 3FlE' 00210 FLO: CALL SPTH ;CHECK STRUT POS'N.

3386' FL0 3E89' F2 3E86' JP 00211 3E8C' 01 lEE0 LX1 00212 B,lEEOH ;SET BC TO 2000 LBS.

IN3 3E8F' CD 3F30' CALL 00213 L15: 3E92' 2A 8000 LHLD 00214 SOOOII 3E95' 22 F708 SHLdD 00215 OF708H :OUTPIJT \'//G ACCEL. TO DACO 3398' CD 3F8D' CALL 00216 FTEST 3E9B' D2 3EBD' JNC 00217 L13 B,lEEOB ;SET BC TO 2000 LBS.

3E9E' 01 lEE0 LX1 00218 3EAl' CD 3F76' CALL 00219 L16: IN4 3EA4' 22 F708 SHLD 00220 OF708H ;OUTPUT W/G ACCEL TO DACO 3EA7' CD 3F8D' CALL 00221 FTEST 3EAA' DA 3E7C' JC 00222 L12 SEAD' 21 lEE0 LX1 00223 H,lEEOH ;SET HL TO 2000 LBS.

3EBO' 3E 95 MVI 00224 A,95H ;CLOSE F FDBK & REV. SIGN 3EB2' D3 EA OUT 00225 OEAH ;OF LIMIT FORCE CMD (ANALOG) 3EB4' 22 F70A SHLD 00226 OF'IOAH ;SET LIMIT FORCE CMD=2000 LBS 3EB7' 01 1800 LX1 00227 B,1800H ;SET BC TO 1600 LBS 3EBA' C3 3EAl' JMP 00228 L16 LX1 00229 H,lEEOH ;SET HL TO 2000 LBS 3EBD' 21 lEE0 L13: SHLD 00230 OF70AH ;SET LIMIT FORCE CMD=2000 LBS 3ECO' 22 F70A MACRO-80 3.34 04-NOV-79 PAGE l-5 3EC3' 00231 L14: MVI A,DDH 3E 9D 00232 OUT OEAH ;CLOSE FORCE FEEDBACK D3 EA LX1 ;SET BC TO 1600 LRS 00233 B,lBOOH 01 1800 00234 JMP L15 C3 3E8F' 00235 ~****************************************************** , 00236 ; TAKEOFF MODE 00237 ;*******************************~~**~~**~~~***~*~****** 00238 L12A: LX1 SECD' 21 0000 H,OOOO 00239 SHLD OP70AH ;SET LIMIT FORCE CMD= 0 LBS. 3EDO' 22 F70A 00240 MVI 3ED3' 3E A9 A,OASH 00241 OEAH OUT ;ENABLE SERVOLOOP & OPEN F FDBK 3ED5' D3 EA 00242 FLOA: CALL ;CHECK STRUT POSITION 3ED7' CD 3FlE' SPTH 00243 JP SEDA' F2 3ED7' FLOA BEDD' 01 lEE0 00244 ;SET BC TO 2000 LBS B,lEEOH LX1 00245 L15A: 3EEO' CD 3F30' IN3 CALL 3EE3' 2A 8000 SOOOH 00246 LHLD 3EE6' 22 F708 00247 SHLD ;OUTPUT W/G ACCEL TO DACO OF708H 3EE9' CD 3F8D' FTEST CALL 00248 3EEC' D2 3FOE' L13A 00249 JNC SEEF' 01 1EEO B.lEEOH 00250 LX1 ;SET BC TO 2000 LBS 3EF2' CD 3F76' IN4 00251 L16A: CALL 3EF5' 22 F708 00252 ;OUTPUT W/G ACCEL TO DACO OF708H SHLD 3EF8' CD 3F8D' FTEST CALL 00253 SEFB' DA SECD' L12A JC 00254 BEFE' 21 lEE0 H.lEEOH LX1 00255 :SET HL TO 2000 LBS 3FOl' 3E A5 A;OA5H MVI 00256 fCLOSE F FDBK & REVERSE SIGN 3F03' D3 EA OEAH OUT 00257 :OF LIMIT FORCE CMD (ANALOG) 3F05' 22 F70A OP7OAH SHLD 00258 ;SET LIMIT FORCE CMD=2000 LBS 3F08' 01 1800 LX1 00259 ;SET BC TO 1600 LBS B,lSOOH 3FOB' C3 3EF2' LlGA JMP 00260 3FOE' 21 lEE0 H.lEEOH LX1 00261 L13A: ;SET HL TO 2000 LBS 3Fll' 22 F70A SHLD 00262 ;SET LIMIT FORCE CMD=2000 LBS OF70AH 3F14' 3E AD MVI 00263 L14A: A,OADH 3F16' D3 EA OEAII OUT 00264 ;CLOSE FORCE FEEDBACK 3F18' 01 1800 00265 LX1 B,1800H ;SET BC 'TO 1600 LBS 3FlB' C3 3EEO' 00266 JMP L15A ~****************************************************** 00267 00268 ROUTINE 'TO SUBTRACT STRUT POS'N FROM THRESHOLD ;****************************************************** 00269 3FlE' E5 SPTH: ;SPTH SETS SIGN FLAG POSITIVE PUSH H 00270 3FlF' D5 PUSH D ;UNTIL STRIJT POS'N ) THRESHOLD 00271 3F20' CD 3F5F' CALL STP ;GET STRUT POSITION 00272 3F23' 21 0020 LX1 H,OB20H ;THRESHOLD 0160H=.05" 00273 02DOH=.l" 00274 05908=.2" 00275 OB20H=.4" 00276 MACRO-80 3.34 04-NOV-79 PAGE l-6 3F26' EB 00277 XCHG 00278 LHLD 3F86H ;GET STRUT POSITION 3F27' 2A 3F86 3F2A' CD 3F92' 00279 CALL ;SUBTRACT STRUT FROM THRESH.

SUB2 3F2D' 00280 D Dl POP 3F2E' El 00281 POP H 3F2F' c9 00282 RET ~**********************************************~**~**** 00283 00284 ROUTINE TO INPUT AND STORE DATA FROM MUXO,l & 2 ; :****************************************************** 00285 3F30' 3E 01 00286 iN3: MVI A,01 3F32' 21 F701 00287 LX1 H.OF701H 3F35' 77 00288 Mov M; A 3F36' 2B 00289 ncx H 3F37' 36 01 00290. MVI M,Ol Ml: MOV A, M 3F39' 00291 3F3A' it 00292 RLC 3F3B' D2 3F39' 00293 JNC Ml 00294 MVI M,OO 3F3E' 36 00 3F40' 2A F704 00295 LHLD OF704H 3F43' 00296 SHLD 22 8000 SOOOH 3F46' 22 3F80 00297 SHLD 3F80H 3F49' 3E 00 00298 MVI A,00 3F4B' 21 F701 00299 LX1 H.OF701H 3F4E' 77 00300 !hOV 11 ; A 3F4F' 2B 00301 DCX H 00302 MVI 3F50' 36 01 M,Ol 3F52' 7E 00303 M2 : MOV A,M 3F53' 07 00304 RLC 3F54' D2 3F52' 00305 JNC ML?

3F57' 36 00 00306 MVI M.00 3F59' 2A F704 00307 LHLD OF704H 3F5C' 22 3F84 00308 SHLD 3F84H 3F5F' 3E 02 00309 STP: MVI A,02 3F61' 21 F701 00310 INl: LX1 H,OF701H 00311 EhOV El, A 3F64' 77 3F65' 2B 00312 DCX H MVI hl , 01 3F66' 36 01 00313 3F68' 7E 00314 M3: MOV A;El 3F69' 07 00315 RLC 3FGA' D2 3F68' 00316 JNC M3 3FGD' 36 00 00317 MVI M.00 00318 LHLD OF704H 3F6F' 2A F704 00319 SHLD 3F86H 3F72' 22 3F86 00320 RET 3F75' c9 ;******S**************************+********~************ 00321 00322 ROUTINE TO INPUT AND STORE DATA FROM MUX4 ; a3 MACRO-80 3.34 04-NOV-79 PAGE l-7 .**********+*************************+***************** 00323 3F76' 3E 04 00324 iN4: MVI A,04 3F78' 21 F701 00325 LX1 H.OF701H 3F7B' 77 00326 MOV M;A 3F7C' 2B 00327 DCX H 3F7D' 36 01 00328 MVI M,Ol 3F7F' 7E 00329 M4: MOV A,M 3F80' 07 00330 RLC 3F81' D2 3F7F' 00331 JNC M4 MVI 3F84' 36 00 00332 M,OO 3FB6' 2A F704 00333 LHLD OF704H 3F89' 22 3F96 00334 SHLD 3F96H 3F8C' c9 00335 RET ;****************************************************** 00336 00337 ROUTINE TO SUBTRACT BC FROfh HL -****************************************************** 00338 3F8D' 7D 00339 HTEST: MOV A,L 3F8E' 91 00340 SUB C 3FSF' 7c 00341 MOV A,H 3F90' 98 00342 SBB B 3F91' c9 00343 RET ;****************************************************** 00344 00345 ROUTINE FOR DOUBLE PRECISION SUBTRACT 00346 HL=DE-HL ;****************************************************** 00347 3F92' 7B SUB2 : 00348 MOV A,E 3F93' 95 00349 SUB L 3F94' 6F 00350 MOV L,A 3F95' 7A 00351 FhOV A,D 3F96' 9C 00352 SBB II 3F97' 67 00353 FhOV II, A RET 3F98' C9 00354 .****************************************************** 00355 00356 ROUTINE TO SHIFT VALUE IN HL LEFT 4 PLACES :*************~**************************************** 00357 3F99' 29 00358 ~NM : DAD H 3F9A' 29 00359 DAD H 3F9B' 29 DAD H 00360 H 3F9C' 29 00361 DAD 3F9D' C9 00362 ‘ RET .**************************************************~*** 00363 '00364 ROUTINE TO ACTIVATE MATH BOARD & WAIT FOR RESULT ; 00365 ACCUMULATOR HAS OPCODE ; ~****************************************************** 00366 3F9E' D3 A0 00367 MATH: OUT OAOH 3FAO' DB A7 WAIT: IN 00368 OA7H - MACRO-80 3.34 04-NOV-79 PAGE l-8 00369 3FA2' E6 01 AN1 01 3FA4' C2 3FAO' 00370 JNZ WAIT 3FA7' c9 00371 RET ;****************************************************** 00372 ;****************************************************** 00373 00374 THE FOLLOWING ARE SPECIAL CHECK-OUT ROUTINES 00375 AND NOT PART OF THE MAIN PROGRAM ;****************************************************** 00376 ;****************************************************** 00377 00378 00379 ;************************************************~***** 00380 00381 ROUTINE TO INPUT A VALUE FROM A/D & STORE IN RAM ;****************************************************** 00382 00383 3FA8' F3 DI 00384 3FA9' 3E 00 MVI A,00 3FAB' CD 3F61' 00385 CALL IN1 3FAE' CF 00386 RST OlH 3FAF' 00 00387 NOP 3FBO' 00 00388 NOP ;****************************************************** 00389 00390 ROUTINE TO DO PGA TEST ON A/D ;****************************************************** 00391 3FBl' F3 00392 DI 3FB2' 21 F701 00393 LX1 H,OF701H 00394 3FB5' 36 00 PGA: MVI h1,OO 3FB7' 36 CO 00395 MVI M,OCOH 3FB9' C3 3FB5' 00396 JMP PGA BFBC' 00 00397 NOP ;****************************************************** 00398 00399 ROUTINE TO OUTPUT A VALUE TO DACO & DACl ;****************************************************** 00400 3FBD' F3 00401 DI 3FBE' 00 00402 NOP 3FBF' 21 0000 00403 R2: LX1 H,0000 3FC2' 22 F708 00404 SHLD OF708H 22 F70A 00405 SHLD OF70AH 3FC5' 3FC8' 00 00406 NOP 3FC9' 00 00407 NOP 00408 NOP SFCA' 00 00409 3FCB' C3 3FBF' JMP R2 00410 END MACRO-80 3.34 04-NOV-79 PAGE S MACROS: SYMBOLS: 3DDF' EXST 3E6C' FL0 3386' ANM 3F99' CHACEL IN1 PX3 FLOA 3ED7' FTEST 3F8D' 3F61' 3F30' IN4 3F76' Ll 3D52' LlO 3DD2' Lll 3DD5' L12 L12A SECD' L13 3EBD' L13A 3FOE' 3E7C' L14A 3E8F' L15A 3EEO' L14 3EC3' a ' L16 3EAl' Ll6A :cF;i ' ii" 3E3D' L5 3E68' L8 3D79' L8A 3DB4' L9 3DC4' Ml 3F39' M3 3F68' M4 M2 3F52' 3F7F' MATH 3F9E' PGA 3FB5' R2 3FBF' SPTH 3FlE' START 3DlO' STP 3F5F' SUB2 3F92' TLl 3D2E' TL2 3D30' TL3 3D34' WAIT '3FAO' NO FATAL ERROR(S)

8.0 REFERENCE

1. Ross, Irving and Edson, Ralph: An Electronic Control

for an Electrohydraulic Active Control Aircraft Landing

Gear. NASA Contractor Report 3113, April, 1979.

1. Repon No. 2. Govcrnmrnr Acctssion No. 3. Recipient’s Ca?alog No.

NASA CR-3552 4. Ti:lc and Subfitlc 5. Rccm-~ Datr April 1982

An Electronic Control for an Electrohydraulic

6. Pcriorming Organization Co&

Active Control Landing Gear for the F-4 Aircraft

8. Performing Organization Repwt No.

7. Author(s) / 5 5 v ,; HR 74600000

Irving Ross and Ralph Edson

10. Work Unit No.

9. Performing Organization Name and Address 11. Contract or Grant No.

Hydraulic Research Textron, Inc.

NASl-16420

Valencia, CA 91355 13. Type of Repon and Period Covered 12. Sponsoring Agency Name and Address

Contractor Report

National Aeronautics and Space Administratibn 14. Sponsoring Agency Code Washington, DC 20546 5. Supplementary Notes

Langley Technical Monitor: John K. McGehee Final Eeport

Final Report 6. Abstract

HR Textron Inc., under NASA Contract NASl-14459, has

developed and designed a controller for an electro-

hydraulic active control landing gear for the F-4

aircraft. A controller, developed under NASA Contract

Simu- NASl-14459, was modified for this application.

lation results indicate that during landing and

rollout over repaired bomb craters the active gear

effects a force reduction, relative to the passive of approximately 70%.

gear, 7. Key Words Euggerred by Author(s)) 18. Distribution Statement Aircraft Landing Gear Unclassified - Unlimited

Electronic Controls

Active Controls

Landing Loads

Subject Category 05 -. --- 9. Security Qauif. [of this repxt] 22. Rice 20. Security Classif. (of this pagej 21. No. of Pages

Unclassified Unclassified 92

A05

For sale by Ihe Nalional Technical lnformatlon SewIce. Sprqlleld. Vuguxa 22161 NASA-Langley, 1982