Report of the Second Piloted Aircraft Flight Control System - Acgsc.org

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~dditional means were tried in laboratory tests to improve performance. Damping in the feedback loop was tried, although better results were obtained, the installation complications did not warrant its use. The use of a double om rlng piston also helped to reduce phase lag by reducing backlash of the system. Although the improvement did not reach the magnitude desired, the double ROW ring piston was installed since bacldash uill deterlorate aw system. The main problem, that of low spring rates of the system, still remained, and prevented necessary increase in system gain to obtain better response. This problem can be illustrated by referring to a basic type power operated control system using a direct feedback linkage as shown schematically in figure 4. It can be seen that external disturbance to the control surface or mass results in deflection of the reaction structure. If the input system is held fixed while the reaction structure is deflected, the followup linkage opens the control valve in a direction to oppose this disturbance. ~f the system has high gain, the control 'valve may admit enough energy to cruse the system to over correct the surface position. Due to the inertia of the surface the over correction causes a deflection of the structure In the opposite direction which in turn again opens the valve and again excess energy is admlttecl ad the cycle is repeated. If the energy admltted per cycle is equal to or greater than that extracted by aerodynamic damping and friction of the system, the surface will continue to oscillate. The amount of energy that is added to the gystem is prinudly detelc mined by the flow characteristics of the mstering vahe and mry be kept small if the flow per unit deflection is emall. Stability mey, therefore, be achieved by ube of a law gain valve. This improvement in stabil%ty of the system is obtained at the expense of speed of response. As very little can be done about the hydraulic spring rate and as the structure stiffness can be increased only to a limited degree, it was evident that some other means should be coxwidered to compensate for all of the system spring rates. ADDITION OF STRUCTURAL COMPE2SATION TO THE BASIC TYPE SISTBl High performance of a servomechanism cannot be obtained if lack of stability lindts the allowable gain. Therefore, the stability of the system is the gwerning factor. Improvement can be obtained by increasing either spring rate or damping or by reducing the mass. For this system the mass could not be reduced and adding damping to the output was not considered practical or desirable, leaving the reaction spring rate as the factor to be considered in order to Improve stability.
The overall reaotien rpring rate ir due to a rerier of rpringr. In tho sohematio. figure 4, they were grouped into 2 min rpringr, K8 rtruotural rpring rate and Kh hpdraulio and other spring rater. The firrt problem ir to find a rsnr for Garuring tho rpring deflmotion thon seeond to find a ma- of uring this rgring defleotien to rtabiliw the rymtem. The rtruotural defleotion ir a oonvmiently rarurable quantity* It om be ured to represent the -tire rpring ryrtem defbotim if the propor ratio ir applied. Hw thir defleotim ir ured will be 8h.m analytioally. However, in order to provide the baris for the analytioal treatment of the subjeot, the rystem and it8 speratiaa will be explained first. Roof for thir explanation will then be given. In thir ryrter a mohanieal linkage is used te modify the ryrtem error in aooordanoe rith the defleotien of the reaotien rtruoture. Tha bario system of figure 4 rlth the addition of rtru0tur.l defl~~tion oempensatirn ir rhcnn in figure 5. AU external dirturban00 to the oontrol surfaoe or maor rill defleot the reaotien rtruoture* The follarr-up linkage rlll mols the oontrol valve to oppore th. disturbanoe in the same manner a8 illurtratad for the unoampenrated syrtem. The ooqtonratian linkage, horswp new alre add8 te the valve rignal. The direotion of the valve movemnt due to the oompenratiag linkage in opporite to tha valve movement introduoed through the follm-up linkage. By the proper urangsmsnt of the ratio between the reaotien oompenrating linkage and the follsr-up linkage the direotien and mmitude ef oontrol valm rovemont 01~) be varied. Tho mwemsnt of the oontrol valw ar a rerult of' an external dirturbanoe oan be aade to reduoe tb amount of energy added to the syltem or to extraot energy From the ryetom. For a rpoial linkage arrangemnt, energy rlll be neither added to or extraoted from the ryrtem. The added linkage oarr be mde to rtabilire the ryrtem regardlerr of the mpitude, dlreotion or origin sf the dirturbing foroe. Thir pormitr m inoreare in system gain te obtain improved porfo~oe. An malyrir of the ryrtem rhuur that the ryrtem atability ir dependent on a derived term whioh rlll be referred te a8 the 'Coqtonratien Faotor ."
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-3-a'uo#Su!qs~~ MVN 3Hl 4 0 lN3WlIJ
Page 3 and 4:
CONTENTS 1, Centering Charauteristi
Page 5 and 6:
CENTERING CHARACTERISTICS OF POWER
Page 8:
Since pilqt effort and s*face force
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The centering characteristics excep
Page 18:
-mtla= etlq 30 pwdo o q m ~APA opl
Page 21 and 22:
HELICOPTER POWERED CONTROL SYSTEM P
Page 23 and 24:
Returning to the discussion of the
Page 25 and 26:
loaded by-pass valve closes, and fr
Page 27 and 28:
FUGET RESEARCH ON FORCE WHEEL CONTR
Page 29 and 30:
precisely. The fir at demonstration
Page 31 and 32:
to hare thq coakpit controle comman
Page 33 and 34:
conrtsnt speed). While this ryrtem
Page 35 and 36:
I I SURFACE I AIRCRAFT DYNAMICS LOA
Page 37 and 38:
AUTOMATIC PUT DYNAMICS a LOAD DISTU
Page 39 and 40:
FORCE ME- SERVO. \ - = AMPLIFIER =
Page 41 and 42:
The configuration described above r
Page 43:
AN ANALYSIS OF FULLY-POWERED AIRCRA
Page 46 and 47:
"W@J@tI pendm ao poqtmeard euofenfo
Page 48 and 49:
Ooeo red em;Co* ey tg areqm - a d m
Page 50 and 51:
Variation of Valve Flcnr with Press
Page 52 and 53:
p - instantaneons density (mare per
Page 54 and 55:
where %, , %+ , fi , and A r' are p
Page 57 and 58:
The error equation (l), with XI * i
Page 61 and 62:
C C U P m ZERO - (Bulk Modulus infi
Page 63 and 64:
Canparing equation (32) vith eqatio
Page 66 and 67: EFFECT OF ADDRIG A SPEUNC IllbD AT
Page 70: The outtmt 4 is then -tion (a) may
Page 74 and 75: 71 It is of interest to anmine the
Page 77 and 78: It w ill now be shrnm that the quad
Page 79: tp = 4 1' ( 4 include. aU flaxibill
Page 83 and 84: Frequancy Response of Another prore
Page 85 and 86: or, ii the pinton s p w A, in f ~ t
Page 88 and 89: $ - BZ~W~ pfY88WC)* - presstam on e
Page 90 and 91: INTRODUCTION PARAMETERS FOR THE DES
Page 92 and 93: to the piston. When the spool membe
Page 94 and 95: Figure 2 shows an oscillographlc re
Page 96: lication of equations. - The method
Page 99 and 100: The solution to equation (11) , is
Page 101 and 102: I RATIO OF PEAK TRANSIENT CYLINDER
Page 103 and 104: Equations (21) and (22) are written
Page 105 and 106: variation of this rise time with T
Page 107 and 108: CHART ILLUSTRATING EFFECT OF INERTI
Page 109 and 110: pa lo=$ $8 uoy$eyQd moy pamwam $ndq
Page 111 and 112: IMPROVEMENT OF POWER SURFACE CONTRO
Page 113 and 114: FIG. 2 INSTALLATION - POWER OPERATE
Page 115: AMPLITUDE RATIO- DB I 0 I 0 I cn 0
Page 119 and 120: FIG.5 - SCHEMATIC -- BASIC TYPE POW
Page 122 and 123: With theae substitutions into equat
Page 124: Although only one type of power oon
Page 127 and 128: 0 AMPLITUDE RATIO- D8 I I I I rU rU
Page 129: In the range ai airplane natural fr
Page 132 and 133: Figure 1. anticipation of the targe
Page 134 and 135: The constant k helped to improve th
Page 137 and 138: to determine if there was behaviora
Page 139 and 140: SYNTHESIS OF FLIGHT CONTROL SYSTEMS
Page 145 and 146: The hydraulic system itself is a hi
Page 147: P :: 7 OT- a- ' 06- 09- . I
Page 150 and 151: Zeros introduced by resonance of th
Page 152 and 153: explicit set of specifications-or a
Page 155: her@ is to lnake the push-rod as st
Page 160: particular problem. We then choose
Page 164 and 165: changing flight corditions. Idea-,
Page 166 and 167:
A,. Area of bydraullc jack giston.
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