A new concept in actuation for aerospace mechanisms is presented. This actuator, called an 'eccentuator', features unique output characteristics, installation and envelope efficiencies, and relative simplicity. The actuator can be powered by either hydraulic or mechanical inputs. Potential applications of the 'eccentuator' and development efforts are discussed

Musgrove, R. G.

English

NASA Technical Reports Server

./
!7
__i_,, ,..-25
..... N80 2350 1
TrlE {.CC_NTUATOR A NEW CONCEPT IN ACTHATION
.__ Robert G, HuagroVo
-_ Vought Corparation
ABSTRACT
A now concept In actuation for aOrogpaco mOchan_m_ is presented. Thl_
actuator, called an EcecntuaLor, features unique outpu_ characteristics,
installation and envolopo effictencies, and _el,attvo 8impliclty. The
actuator cat, b_ powered by either hydraulic or machanlcal inputs. Potential
applications of tim Eccgntuator and development efforts are discussed,
INTROI)UCTION
The new actuation concept was dlscoverod during research for metbods of
actuating varlable camber surfaces on Supercrltlcal wings- The supercrltlcal
contour in the region of the control surface hinge llne is thinner than a
conve_tional airfoil contour. The aft air loading of the supeDcrltical
co.tour causes large hinge moments on the control surfaces. The thin
lJ contours and large hinge monents coupled with an aerodynamic requirement to
keep both the upper and lower surfaces free from protuberances created a need
for an actuation system which did not resolve the hinge moments wltb a force
couple parallel to the surface reference plane. The actuation system also
had to be mechanically and hydraulically stiff and have good positioning
resolution.
An attractive possibility for such a system was a bent beam situated
along the surface reference plane and supported in the wing by a two bearing
socket. Rotation of the bent beam in the w/ng socket would cause angular
motion of the free end of the beam about a hinge line. ilowever, attachment
of the fiap to the free end of the beam with an acceptable bearing structure
presented a problem. The free end of the beam not only moved in an arcuate
motion about the hinge line, but it also had lateral motion along the hinge
line. Previous use of bent beam actuators employed rollers on the beam in
spanWise tracks i_ the flap to accommodate this lateral motion.
The Eccentuator is a bent beam actuator that compensates for the lateral
motion of the beam w_th an eccentric bearing on the support end of the beam.
A unique indexing gear arrangement employed with the bent beam arid the
eccentric bearing keeps the free end of the beam in a plane normal to the
hinge llne. Not only does the bent beam/eccentrlc bearing combination result
i: in planar arcuate motion, but the arcuate motion is twice that achievable by
rotating the bent beam alon_.
The Eccentuator actuator exhibits load carrying capabilities much llke a
straight, fixed-end beam between the flap and the wing. For small surface
deflection angles around 24°, the Eccentuator carries 90%-I00% of the hinge
i( moment through its structural elements dependln_ on the deflection position.
00000001-TSE13
https://ntrs.nasa.gov/search.jsp?R=19800015010 2020-03-21T03:09:51+00:00Z
Tim r_maintng IOZ_OZ h_nge mamont ls r,_act_d by an acruartan systems, Tl_l_
reduced actuation forc_ roqulrem.nr is a ro_ulr of th_ _nhoron_ w_rl_blo
moch_m_tcal advantage in the E¢conruntor, The Eccontuator system c,an thoro_
fare he tho.ght of as w_rlab:le geometry structure.
Th_ larg¢1 tnho,ron_ mechanical advantage whlch ronulr_ in a tow aeruatlnn
requircm_n_ allows 8ovoral unique actuation con_optt_. A _mall !n_,_r_l
rotary hydraulic actuator can he placed between the _wo movln_ part_ and
apply actuator force, directly _o the load carryl.n_ member,s. For meehanleal
drive 8ya_omg, the lnhoren_ mechanical advantage redneoo _he load on th_
::: dr_ve gears allowing _heao to be smaller, The inherent mechanical advantage
reduces the effegt o_' gear freeplay on the surfact_.
The drawing in figure I illustrates a basic slnglo_ended hydraulic
Eccentuator. The eccentric support b_arin8 is called a carrier. The
indexing rln8 g_ar is _ounted onto tlte grounded suppoct housing while the
indexing gear is fixed to the beam,
CONCEPT SIblPLICITY
Tlle drawing in figure 2 illustrates the basic motion of the Eccentuator.
In figur_ 2(a) the motion generated by rotating the beam alone ts shown. The
angular output is twice the beam bend angle. The lateral motion along th_
htnge line is also noted. Figure 2(b) shows the carrier location with
respect to the hinge lln_ aP.d illustrates with a theoretlcal stre lght beam
the effect on a beam of rotating the carrier in the opposite direction from
that of the beam. The free end of the theoretical beam moves in the same
angular direction as the bent beam, but the lateral fnovement is in the
opposite direction. The eccentric bearing centerllne is displaced fro.. the
carrLer centerllne such that it generates an angle with respect to the
car_ler eenterllne equal to the bend angle of the beam. Figure 2(c)
illustrates that when the bent beam is combined with the carrier, and the two
are rotated in opposite directions, the carrier's lateral displacement
compensates for the beam's lateral displacement and the angular motion adds
to produce a total-planar angular displacement of four times the beam bend
angle.
ENVEI,OPE EFFICIENCY
One of the p_Incipal features of the EcCentuator concept is its
installed envelope efficiency. Figure 3 compares the Eccentuator
installation with that of a linear actuator in a flap configuration. The
Eccentuator is centered about the hingelit_e and lies along the eenterllne of
the contour. Hinge moments a_e resolved normal to the wing reference plane
rather than parallel to the reference plane as in most actuation concepts.
The moment arm is therefore not a function of the wing thickness.
O0000001-TSE14
ACTUATION LOADS
Th_ haA_c _truct_ral advan_g_ of _h_ Eec_atuator is that th_ h_ngc
momon_ of the nloving surface Is tl_afl_farrod to the 8uppartin_ structure
pctmarlly through fltrugture. The poflitlonlng actuator thOrefore _uat react
only a. A,_I]. percent af Oio 1odd. The flap hinge moment (Mlt) ts reuolvod aa
shown tfl figure 4, _.nto a couple load on the flap end of the b_am and tranB-
f_r_od _n bonding through th_ beam to a r0actlon couple on the support side.
The couple reaction on the bea_ by tim ca_riar in th_ mtd-_raval position
shown ia not on the conterline of the Eccentuator assembly by the amount of
eccont_i_ity in the carrier. This eccentric loading causes a rotational
torque on the beam in one direction and an equal and opposite torque on the
carrier ..... The actuation torque (MA) on eithe_ tl_--_eam or carrier is
MA = Mil tan 0 cos _ (1)
Whe_: _ = beam bend a_gle
= rotation angle from mld-tvavel position
When the beam IS in the mld-travel position, the actuation torque
requirements are great=st. At the actuator travel extremes where _ is 90u,
the actuation torque requirements diminish to zero. Small beam bend angles,
such as 6° which produce actuator outputs of 240, require a maximum actuation
torque on both the beam and the carrier of only approximately one tent_ of
the hinge moment. As the Eccentuator is posltlon_d away from the mid-travel
setting, the actuation torque requirement decreases for a given hinge moment.
INHERENT MECHANICAL ADVANTAGE
The reduced actuation torque requirements are a result of an inherent
mechanical advantage. This mechanical advantage varies from a maximum value
of infinity at the actuator travel extremes to a minimum value at the
mld-travel position. The inherent mechanical advantage is calculated by the
following equatlo_:
Mechanical Advantage = tan O ¢off _ (2)
From this relation it can be seen that the mechanical advantage doubles,
from its minimum value at mid-travel, when the beam and carrier have been
cotated 60° from the mid-travel position. Full actuator travel and an
infinite mechanical advantage occur at 90o rotation _rom mld-travel. Figure
5 is a typical mechanical advantage Curve for a 6 degree beam bend angle.
This inherent mechanical au_antage can be applied to reduce the input
torq,e requirement at the trawl extremes whe_ encounteri,_g a constant hinge
moment load, or produce an ever increasing output torque, with a constant
input torque, as the actuator is positioned away from center.
59
OUTPUT MOTION CIIARACTERI_TIC_
The output d_floctlon angle ( _ ) a_ a function _ tha rotation of
_ithet tile beata-ar the._carrier iB given by tho f_ll_ln8 _quat_on of motion;
- 2_ (I- 8in _) (3)
Large anflulag motion of the beam and e_tr£er at the ands of travel
p[odU_ llttl_ output motion. Therefore, aVOidance of these areas of v_ry
lar-g_ m_chanlcal advantage.will not produce slgnlflc_nt-autput motlon los_.
DRIVE SYSTEMS
The Eccentuator can be actuated by an integral hydra_llc actuator-at by
external power sources through a unlqBe gear drive system. Figure 6
illustrates these two drive systems. BOth of these systems operate on the
actlon-reaction principle wl_ere the £orce that produces the torque to torn il
the beam also produces the torque to turn the carrier.
Hydraulic Eccentuat_r
The hydraulic Eccentuator is produced by incorporating a rotary
hydraulic actuator between the beam and the carrier as shown in figure 6(a).
The beam becomes the shaft of the actuator and has one of the vanesattached.
_he caxr-ler extension forms the actuator h_u_ing with a vane.
Section A-A o£ figure 6(a.) sho_s that introduction of fluid under
pressure into the a_tuator housing between the vanes produce_ a force on the
beam vane and an equal and opposite force on the carrier. The hydraulic
Eccentuator produces a surface Inst .!arian whleh is very stiff hydrau-
lically. The surface hydraulic stlffaess is a function of the square of the
mechaniaal advantage between the Surface and the hydraulic chamber. Thus, a
24 degree output Eccentuator with its i0:I inherent mechanlcal advantage will
appear to be i00 times as stifl as it would be if the actuator were operating
directly on the hinge line. Since the rotary actuator is one tenth the size
required at the hinge llne, the stiffness increase offered by the Eccentuator
over a votary actuator is approximately tenfold. This factor increases as
the mechanical advantage increases for--posltlon away from the mld-travel
setting.
Mechanical Eccentuator
The preferred mechanical system utilizes a gear on the beam and a pinion
gear mounted on the carrier as shown in figure 6(b). The gear set operates
as a planetary system with the pinion gear being th_ sun gear. The system
gear ratio is the product of the inherent mechanical advantage and that of
the planetary gear set as follows: i
Ng
Gear Ratio = Itlherent Mech Adv x (%77+ i) (4)
--p
Where: Ng = Number of gear teeth
Np = Number of plnlon teeth
60
UUUUUUUl lOl-U I
The _nherent mocllan_cal adva_tag_ amplifies the _y_tem gear ratio and
minimiZeS the cffeeav-_.zmy gaa_ f_de_lay on the drlv_n s_trfaca.
Other mechsnlcai Systems are Indlcat_d by the fact thst rotation of
eLt_mr she beam o_ the ca_xiar will transmit opor_tlonal torque to the other
member though the indexing gears. Driving th_oogh only one part requi_es
inputting twice as much to_qua a_ is requlr_d by _he preferred system
_..scribed above since the to_qu_ of th_beam aa_the c_rrler are additive,
,,, INSTALLATION FLEXIBILITY
The Ecce_tuater can be installed in a _mber of different configura-
tions. •he three shown in figure 7 differ with each oth_r only at the hinge
" llne bearLng on the fixed structttre side. The arrangement in figure 7(a)
shows the structure side h£ngeline bearing to be a part of the carrier.
< Another bearing between the carrier and the beam, which is skewed to the
outer bearing, allows the beam to rotate as well as pivot Within the
structure.
The configuration in f_gure 7(b) allows the beam to rotate and pivot by
.... Use of a spherical bearing.
The configuration of figure 7(c) provides the same functions as the two
_ above, an_ allows for the elimination of one bearing on the beam. The hinge
_. structure on _Ither side of ghe beam provides the loadpath from the support
_ structure reaction to the flap beam rea_tlon bearing. The elimination of _he
_ bearing on the structure Side _llows the beam to be larger in the high
bending load area. The actuation friction associated with turning the beam
_ is reduced.
_ The concepts i_ figure 7 (a) and (b) are structural hinges and a hinge
is not required for the surface.
CONFIGURATION FLEXIBILITY
%:
The Eccentuator concept discussed has been that of a slngle-ended basic
Eccentuator. Two of these basic units can be Joined at the pivot point to
form a double-ended Eceentuator. These two concepts are depicted in figure 8.
The double-ended unit will allow twice as mhch deflection as a slngle-ended
_, unit with the same design beam angle. This dooble-ended arrangement allows
D the hydraulic Eccentuator to have d_al hydraulic chambers, each of wblch can
drive the unit full-travel with half of the load capability,
Shown in figure 8 are multiple units. The tandem arrangement has two
beams and a common carrier. This system has two hinge lines. Multiple hinge
_ lines can be achieved with multiple carriers and beams.
CAPABILITIES
4 The double-ended hydraulic Eccentuator with a design angle of 6 degrees
_ (48 degrees total output motion) can operate against a 4868.5 newton-meter
00000001-TSF03
(100000 Ib-ln) ult_t_ momen_ load and be housed wlthln an estlmatcd
cyllnd_i_al _nVelope 10.4 cm (4.1 in) i_ diameter and 43 cm (17 in) lon_.
The _OVelo_e will increase in size as the d_Ign de_lectlon angle Increases
becaua_ of the necessary growth Of th_ rOtary actuato_ The double-_ndOd
Bcce_tuatoz has _,,ptae_ic_l angular m_tio_ capability of around .90--de_rees.
:, A slngle-ended mechanlCal Eccentoator with an output an_le of 64 degrees
il has been pro_otyped for commercial use. However, to take advantage of the
I inherent mechanical advantage of the Eccentuator to reduce the size of the
drive system and thus the installed envelope in an aircraft, the design
i_ output angle should be limited to around 30 degrees for a single-ended unit
i: and 60 degrees for the double-ended Eccentuator. The ECcentuator concept
offers numerous trade-o_f parameters which allow tailoring the design to
varlou_-requirements.
INSTALLATION AItVANTAGES
Typical installation of a mechanical Ec=entuator in a leading edge flap
application is illustrated in figure 9. In the flap up position the
EccentuatOr is in an overcenter posi.tion and all of the cruise flight loads
are transntltted through, the structural elements of the Eccentuator leaving
the gear drive systems unloaded. This condition also occurs in the flap dow_
pesltio_.
:_ Figure i0 illuStr_tes a typical double-ended hydraulic Eccentuator in a
trailing edge surface application. The Eccentuator is in the mld-travel
position in the control surface neutral pOsitlOn. As deflection of the
surface occurs on either side of Oeutral, the Eccentuator's variable i_herent
_ mechanical advantage increases the Integral rotary hydraulic actuator output
aS the airloads increase. This characteristic allows the Eccentuator to be
designed to lower actuating loads than the normal maximum deflectlo_
airloads.
CONCLUDING REMARKS
Studies have found the Eccentuator to be applicable to many other
actuation problems on aircraft in addition to the thin wing surfaces. Other
aerospace mechanisms on missiles, helicopters and space vehicles also present
application opportunities. The Joints of space and industrial robots have
been identified as potential uses for the Eccentuator. Many agricultural and
industrial applications have been forecast.
A working model of a double-ended hydraulic Eccentuator has been modeled
in both a unit surface and a _dder application. It is demonstrated by using
pressurized Freon. An electric motor powered Eccentuator missile fin control
model demonstrates electro-mech_nlcal operation. Vehicle Steering with a I
manual Eccentuator System has been modeled and prototyped on a late model l
automobile. Other applications are being either modeled or prototyped in the
prOCeSS of developing the Eecentuator concept into a mature actuation system
that wlll meet the demanding requirements of the aerospace _ndustry. i
................ 0000000q-TSF04
O_AT_ PAG_XS
Support Bearing....
-Seam
Carrier
_g Actuator ------_
riming Gear
Set
Figure 1.- Single-ended Eccentuator.
!
20
Lateral DisplaCement
2O
(b)
180o
Clockwise
Rotation
o! (c)Beam
+
1800
COuflterolockWlae
ROtation _
ot
Carrl0r = Eccentuator KinematiCs
Figure 2,- Eccentuator kinematics.
63
O0000001-TSF05
i :
i
! Figure 3.- Installation envelop_ efficiency.
_ Actuator Moment (M A)
_ for Beam//_/!i
:, _CL
Hinge •
i '_ A M ..tan# Cos
i 0
_: _ .....Carrier
Actuator Moment (MA)!
i. for Carrier
i_ Figur_ 4.- Actuation loads analysis.
!
t_ 64
_ ........ ' ....... _ ............. _ _ _ "_ .......... 0 0 0 0 0 0 0 1 TSFO(
i:
O_ POOR QUALI/,_
4O
10.88
Mechanical,., 9.84
Advantage 20 9.5l 02
10 .45
gO. 60 30 0 30 00 90
Beam_Rotatlon._(degreeS)
Figure 5.- Inherent mechanical advantage.
I _Carrler
_Beam _,_
A.A Beam,,,_/_/
!_'__ '/ . Beam
Drive
integral Rotary Gear
I/ HydraulicActuator
[: (a) MechanicAlDrive
(b)
Figure 6.- Drive systems.
65
r
00000001-TSF07
4 Piano Bearings
rio s
3 Plane BearingS___
Structural Hinge +
Hinge
Figure 7.- Installation _lexibility.
_i__ i_.i. • T.iceoU,put
angle of basic
Ecoentuator
,_lngle-Ended. Double.Ended
"Basic"
Tandem • Single carder
Single drive pointTwo hinge lines
• Single or multiple
• Multiple beams drive points
• Multiple carriers • Multiple hinge llfleA
Figure 8.- Configuration fl_.xibility.
66
00000001-TSF08
_,_:._,_.< __i
t.---_
Figure 9.- Leading edge installation.
:__ =___.............fA_ 2___a=e__ ,:_q
_: k > I- I
_ Figure lO.- Trailing edge installation.
_", OI{ILijt'gALPAGB IS
_; Ok"POOR QUALITY
i_"' 67
00000001-TSF09


The Eccentuator: A new concept in actuation

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server