Note: Descriptions are shown in the official language in which they were submitted.
~Z~ '7
This invention relates to an improvement o
an actuator for operating a manipulator (artificial
hand) or the like for treating or handling radioactive
substances surrounded by shield walls or hot cells for
05 protecting from contamination of radiativity in storing
replacing and distributing the radioactive substances
and for other purposes as experiments and working.
Various kinds of actuators have been proposed
for manipulators provided for the above mentioned hot
lo cells. Among these proposaIs, electric systems including
electric motors require reduction gears to increase
total weight and make their construction complicated,
and moreover unavoidably generate sparks in operation,
which make impossible to use the electric systems at
locations requiring explosion-proof. Hydraulic systems
have disadvantages in that hydraulic units are expensive
and heavy and oils used in the units tend to contaminate
themselves J other parts and rooms.
Pneumatic systems are preferably used in case
particularly requiring explosion-proof. Howeverg
pneumatic actuators in general do not provide smooth
movements due to sliding resistance between cylinders
and pistons which are worse still usually made of
steel, so that the self weights of their operating or
movable parts are too large in comparison with their
operating forces, resulting in lower operating accuracy.
With these hitherto used driving systems,
outputs are usually constant during displacements, so
- 2
123~X~7~7
that positioning in strokes cannot be effected smoothly.
As a result, arms accidentally collide against objects
to damage them and, therefore, these systems require
great skill.
0S On the other hand, air bag type actuators
have been known. In such actuators, operating forces
are obtained from axial contracting forces of the air
bags due to enlargement of their diameters when applying
controlling pressure to them. In addition to the light
weight of the bags themselves, they have advantages of
no risk of air leakage and no problems due to friction
because of no sliding parts. The amount of air enclosed
in the bag for the application of the controlling pressure
becomes great due to the expansion of the bag in
comparison with the pneumatic cylinders and is dissipated
into the atmosphere when it is released. It is disad-
vantageous to consume such a great amount of air for
operating. Moreover, the above controlling pressure
acts upon all over inner surfaces of cavity walls in
the air bag, so that the effective axial contracting
forces are reduced by resistance representative of
a product of the control pressure and cross-sectional
area perpendicular to the axis of the bag subjected to
the control pressure at least during an initial period
of its operation.
A pneumatic actuator of such an air bag type
for example as shown in Fig. l has been publicly known
disclosed in Japanese Patent Application Publication
~31~7
No. 40,37~/77.
The pneumatic actuator as shown in Fig. 1
comprises a tubular body 1, a reinforcing braided
structure 2 externally thereon, closure members 3 at
05 both ends and a clamp sleeve 4. The tubular body 1 is
preferably made of a rubber or rubber-like elastomer
which is air-impermeable and flexible. However, other
materials equivalent thereto, for example, various
kinds of plastics may be used for this purpose.
The reinforcing braided structure 2 reinforced by cords
is somewhat similar to, for example, those conventional
in pressure-resistant rubber hoses, whose braided
angles are approximate to what is called an angle of
repose (5444'). With the braided structure of the
pneumatic actuator initial braided angles 0O are
preferably of the order of 20 in order to obtain the
above angle of repose when the reinforcing structure is
expanded to the maximum diameter due to inner pressure
filled or supplied in the tubular body 1. In this
case, used conditions are determined so as to permit
a strain under normally used conditions to be of the
order of 0.3
The reinforcing cords used in the braided
structure 2 are organic or inorganic high tensile
fibers, preferably, for example, twisted or nontwisted
filament bundles of aromatic polyamide fibers (trade
name, KEVLAR) or very fine metal wires.
With a considerably small angle of the initial
~23~
braided angle JO such as 20, it is not necessarily
easy to braid the outer circumference of the tubular
body l. For example, however, a braided structure
obtained by a conventional hose braiding machine is
05 stretched in its axial direction to be commensurate
with the above initial value and is then fitted on the
tubular body l under the stretched condition, thereby
obtaining the desired braided structure. In this case,
a suitable adhesive may be applied the outer circum-
ference of the tubular body l. An outer sheath ofa weatherproof or injury-protective film may be
preferably provided on the braided structure 2.
Each the closure member 3 comprises a nipple
5 adapted to be closely fitted in each end of the
tubular body l preferably with an adhesive for sealing
the tubular body from the atmosphere, a flange 6 for
positioning the closure member relative to the tubular
body, and an eye or yoke 7 having an aperture for
a connecting pin (not shown). The nipple 5 is preferably
provided on its outer periphery with annular protrusions
8 each having a steep taper surface toward the eye 7
and a gentle taper surface in an opposite direction for
preventing the nipple 5 from being removed. One of the
closure members 3 is formed at least on one side with
a connecting aperture ll communicating with an inner
cavity l0 of the tubular body l through an aperture 9
formed in the nipple 5 in its axial direction. A fitting
12 is fitted in the connecting aperture ll of the
AL23~2~
closure member 3.
Each the clamp sleeve 4 is a cylindrical
metal member engaging the flange 6 so as to cover the
end outer circumference of the tubular body 1 and
05 having a flare 13. The clamp sleeve 4 is partially
pressed toward the nipple 5 in its radial directions to
sealingly unite the closure member 3 with the tubular
body 1. A reference numeral 14 in Fig. 1 denotes axial
depressions caused by a caulking tool in its process.
To the fitting 12 is connected an operating
pressure source, for example, an air compressor through
a line having a three-way valve (not shown).
When a controlled pressure P is applied into
the inner cavity lO of the tubular body 1 through the
fitting 12, the braided structure 2 is expanded from
the position shown in solid lines to that shown in
phantom lines in Fig. 1 to enlarge the initial braided
angles 00 to x or in a pantograph movement of the
reinforcing cords of the braided structure 2 so as to
cause an enlargement of the diameter of the tubular
body 1 and a contraction in its axial direction caused
thereby. A force F of the contraction is given by the
following equation (1)
-- 6 --
~L~3~ 7~7
F = p~4d2( x)2( 2 - l
... (1)
or P4d (3cos2~X - 1)
On the other hand, when the controlled
pressure in the cavity 10 of the tubular body 1 is
released through the three-way valve into the atmosphere,
the tubular body 1 of course regains its length with
decrease of the braided angle ox
It is therefore understood that such a
pneumatic actuator can bring about bending and extending
movement or articulate movements between two pivotally
connected or articulated operating arms to which the
eyes or yokes 7 of the closure members 3 of the pneumatic
actuator are connected by means of pins.
In general, the reinforcing braided structure
2 includes the reinforcing cords embedded in the
proximity of an outer surface of the tubular body
of a rubber-like elastomer so as to be securely united
with each other. With this arrangement, however, the
movement of the reinforcing cords in articulated
movements of arms is restrained by the rubber-like
elastomer to reduce the force of contraction. It is,
therefore, preferable to separate the reinforcing cords
from the tubular body so as to permit free movements of
the cords. However, such a construction permitting the
-- 7
IL ~JiL Ir
reinforcing cords to separate from the tubular body
encounters another problem. Each the reinforcing cord
consists of a number of fine filaments lS having
diameters of 0.02-0.03 mm which are twisted or nontwisted
05 as shown in Fig. 2. Upon expansion of the elastic
tubular body, the fine filaments are likely to bite
into the tubular body due to the greatly changed braided
angles of the cords. Accordingly, the filaments injure
the surface of the tubular body, as if they were very
sharp knives, resulting in breaking down of the tubular
body.
Even if the pneumatic actuator includes the
tubular body with reinforcing cords embedded therein so
as not to separate therefrom, there is in general
a tendency of the cords to penetrate into the elastic
tubular body to reduce the service life of the tubular
body and hence the actuator, because its diameter
increases to 2-3 times of its original diameter and its
axial length contracts to 20-40% of its original length
so as to cause maximum stresses acting upon the reinforc-
ing cords.
In general, with the above conventional
construction of the actuators, there is a relation
between the initial braided angles 00, changed braided
angles ox upon contraction and contractive strains .
~23~27'~),
COS~o - COST
= COS~o (2)
Moreover, there are a relation as the following
equation (3) between original diameters Do of the
braided structure 2 and contracted diameters D and
a relation as the following equation (4) between the
contractive forces F and the other parameters including
controlled pressure P.
D = DOsin~o ... (3)
F = -Do2P l ~3(1-~)2cos~0-l} ... (4)
These relations hold true at approximate
center zones of the actuators. However, these relations
do not hold true at both the ends of the actuators,
because the diameters at the ends are restrained from
changing. As shown in Fig. 4 schematically illustrating
an expanded braided structure 2 from an original
condition shown in Fig. 3, the ends of the braided
structure 2 are prevented from expanding to cause
unnatural strains of the structure which would give
rise to fatigue failure of the structure and obstruct
the occurrence of the expected contractive force.
A solid line A in Fig. 5 illustrates a relation
between the contractive force F and the strain obtained
~L;23~ 7
from the equation (4) when the controlled pressure P is
constant. A broken line B in Fig. 5 was obtained by
actually measuring contractive forces and s-trains with
actuators of the prior art having constant diameters of
05 the brained structures and constant braided angles.
The broken line B is fairly different from the theo-
retical line A due to the restraint of both -the ends of
the braided structure 2. A dot-and-dash line C and
a two-dot line I will be explained latter.
0 As above described, the actuator radially
expansible and simultaneously axially contractible with
the aid of controlled pressure applied therein has the
various advantages of light weight as a whole, smooth
movements in operation and reliable performance of
positioning which are not obtained by the systems using
electric motors or hydraulic piston and cylinder
assemblies. Various applications are considered
utilizing these superior characteristics of the expan-
sible and contractible actuator.
Fig. 6 illustrates a linear driving system
actuated with pneumatic pressure including a servo-valve
having a torque motor 21, nozzles 22 and 23, a flapper 24
and throttle valves 25 and 26, and two elastic actuators
27 and 28 arranged in series with aligned axes.
With this arrangement, for an operation the
torque motor 21 is energized and the flapper 24 is
deflected for example in a direction shown by an arrow D,
so that a clearance between the nozzle 22 and the
- 10
23~ 7
flapper 24 becomes smaller and a clearance between the
nozzle 23 and the flapper 24 becomes correspondingly
larger. Accordingly, a back pressure on a side of the
nozzle 22 approaches the supplied pressure of the air
05 and a back pressure on a side of the nozzle 23 approaches
the atmospheric pressure, respectively. As the result,
the pressurized air is supplied into the actuator 27,
while the pressurized air in the actuator 28 is exhausted,
so that a mass point 29 is driven in a direction shown
by an arrow E. When the flapper 2~ is deflected in the
direction opposite to the arrow D, it should be under-
stood that the mass point 29 is driven in the direction
opposite to the arrow F.
There has been proposed a driving system
similar to the above linear driving system, wherein
back pressure of nozzles is changed so as to move
a spool of a guide valve to change air flow.
However, the above systems are expensive to
manufacture due to high cost torque motors used therein,
complicated in construction and slow in response.
Under a steady condition, moreover, the pressurized air
leaks at nozzles to cause noise and to increase consump-
tion of the pressurized air. In addition, exact
positioning canno-t be easlly effected with these systems.
It is a primary object of the invention to
provide an improved actuator for a manipulator, which
eliminates the disadvantages of the prior art.
It is another object of the invention to
3L~3~2~'7
provide an improved actuator comprising braided structure
whose cords do not bite into a tubular body upon
expansion, thereby decreasing damage of the tubular
body to elongate its service life.
05 In order to achieve these objects, the
pneumatic actuator including a tubular body made of
a rubber-like elastic material, closure members sealingly
closing ends of said tubular body and a braided structure
reinforcing an outside of said tubular body and made of
lo braided cords of high tensile fibers, said braided
structur being expanded in its radial direction and
being simultaneously contracted in its axial direction
together with said tubular body when pressurized fluid
is supplied in a cavity of said tubular body through
one of said closure members, according to the invention
said braided cords of said braided structure comprises
monofilaments each having a smoothly rounded outer
surface of a large radius of curvature.
In a preferred embodiment of the invention,
a protective layer is provided between the tubular body
and the braided structure.
It is a further object of the invention to
provide a pneumatic actuator whose braided structure
has an improved con-tracting performance and high fatigue
2s strength and can greatly save air consumption to
eliminate the disadvantage of much air consumption of
the air-bag type actuator without adversely affecting
the advantages of the air-bag type actuator.
- 12 -
3~3~
This object can be achieved by the actuator
constructed according to the invention in a manner that
diameters of both ends of the braided structure and
braide angles at both the ends are made larger than
05 those at a substantially mid portion of the braided
structure, and that a filler is provided in the cavity
of the tubular body without obstructing the expansion
and contraction of the tubular body.
In a preferred articulated arm for a manipu-
lator including at least two pneumatic actuators
according to the invention, first and second arm members,
one ends of the actuators being connected to the first
arm member and the other ends o-f the actuators being
connected to the second arm member.
A preferred driving control system for
a connection of two pneumatic actuators according to
the invention comprises flowing-in control valves for
controlling the fluid flowing into the actuators,
respectively and flowing-out control valves for con-
trolling the fluid flowing-out of the actuators,
respectively, the flowing-in and flowing-out control
valves for each the actuator being operated reversely
in a manner such that when the flowing-in valve is
opened, the flowing-out valve is closed and vice versa,
zs and the flowing-in control valves for the actuators
being operated reversely in a manner such that when one
of the flowing-in control valves is opened, the other
is closed and vice versa.
- 13 -
The invention will be more fully understood
by referring to the following detailed specification
and claims taken in connection with the appended
drawings.
05 Fig. 1 is a front elevation partially in
section of an air-bag type actuator of the prior art;
Fig. 2 is a schematic cross-sectional view of
a cord constituting a braided structure for a pneumatic
actuator of the prior art;
Fig. 3 is a schematic sectional view of
a pneumatic actuator of the prior art for explaining
operation of the actuator of the prior art;
Fig. 4 is a schematic sectional view of the
actuator shown in Fig. 3, when expanded;
Fig. 5 is a graph illustrating relation
between contractive force and strain of pneumatic
actuators;
Fig. 6 is a schematic view of a linear driving
device of the prior art;
Fig. 7 is a schematic sectional view of
a cord for constituting a braided structure of a pneumatic
actuator according to the invention;
Fig. 8 is a schematic sectional view of
a preferred embodiment of the cord used for the actuator
according to the invention;
Fig. 9 is a schematic sectional view of
another embodiment of the cord used for the actuator
according to the invention;
~3~'7,
Fig. 10 is a partial perspective view of
a preferred embodiment of the actuator having a protec-
tive layer according to the invention;
Fig. 11 is a partial perspective view of
os a modified embodiment of the actuator shown in Fig. 10;
Fig. 12 is a partial sectional view of
an actuator comprising the protective layer shown in
Fig. 10 or 11;
Fig. 13 is a partial sectional view of
lo a preferred embodiment of the actuator comprising
a modified braided structure according to the invention;
Fig. 14 is a schematic sectional view of the
pneumatic actuator shown in Fig. 13 for explaining its
operation;
Fig. 15 is a schematic sectional view of the
actuator shown in Fig. 14, when expanded;
Fig. 16 is a partial sectional view of
a further preferred embodiment of the actuator comprising
a filler according to the invention;
Fig. 17 is a partial sectional view of
a modified embodiment of the actuator according to the
invention;
Fig. 18 is a perspective view of an articulated
arm or mechanical hand for a manipulator to which
actuators (only one shown) according to the invention
are applied;
Fig. 19 is another embodiment of the articu-
lated arm shown in Fig. 18;
Fig. 20a is a further embodiment of the
articulated arm shown in Fig. 18;
Fig. 20b is a side view of the articulated
arm shown in Fig. 20a;
05 Fig. 21a is a modification of the articulated
arm shown in Figs. 20a and 20b;
Fig. 21b is a side view of the articulated
arm shown in Fig. 21a;
Fig. 22a is a perspective view of a modifica-
0 tion of the articulated arm shown in the preceding
drawings comprising means for detecting angularly moved
angles of arm members of the articulated arm;
Fig. 22b is a view illustrating the angular
movement detecting means shown in Fig. 22a;
Fig. 23 illustrates a schematic arrangement
of a driving control system to which are applied
actuators according to the invention;
Fig. 24 is a sectional view of an electro-
magnetic flow control valve to be used in the control
system shown in Fig. 23;
Fig. 25 shows a preferred feedback compensation
circuit for use in the control system shown in Fig. 23;
Fig. 26 is a block diagram of a feedback
compensation circuit to be used in the system shown in
2s Fig. 23 when used for positional controlling; and
Fig. 27 is a schematic view of a modification
of the control system shown in Fig. 23.
Figs. 7-9 illustrate in section preferred
- 16 -
7~
reinforcing cords having smooth rounded outer surfaces
used for the actuator according to the invention.
Fig. 7 shows the cord comprising a monofilament or
steel wire 16 of a circular section having a diameter
oS of the order of 0.5-2 mm. Fig. 8 illustrates a rein-
forcing cord comprising a number of fine filaments 35
twisted or nontwisted to form a bundle 37 and a rubber-
like elastomer or synthetic resin 38 coated on said
bundle. Fig. 9 shows a flat yarn 39 having an elongated
lo circle or elliptical cross-section. These reinforcing
cords are made to have smooth surfaces to avoid sharp
edges contacting surfaces of elastic tubular bodies and
to have wide surfaces contacting -the tubular bodies as
much as possible to reduce contacting surface pressure,
thereby greatly reducing damage to the -tubular bodies
due to penetration of sharp filaments into the bodies.
In order to compare these reinforcing cords
and those of the prior art, the inventors have carried
out a durable test of actuators including rubber tubular
bodies having inner diameters 8 mm, thicknesses of
walls 1 mm and lengths 300 mm and braided structures
secured about the tubular bodies and having braided
density of 90%. In this experiment, monofilaments made
of polyester each having a diameter of 0.4 mm according
to the invention were used as reinforcing cords, while
reinforcing cords consisting of three bundles each
consisting of 44 filaments having a diameter of 0.02 mm
according to the prior art were used. In measuring,
3~'7
pressure of operating air was changed from 2 kg/cm2 to
zero kg/cm2 or atmospheric pressure with cycles once
per one second. Each the actuator was subjected to
a load of 1 kg hanging from the actua-tor during
os measuring. The rubber tubular bodies having braided
cords of the prior art were broken down at 13,600 cycles
of pressure change, while the tubular bodies according
to the invention were broken down at 67,000 cycles.
As above described, according to the invention
lo the reinforcing cords constituting the braided structure
are monofilament cords having smoothly rounded outer
surfaces of large radii of curvatures to reduce contact
surface pressure with surfaces of elastic tubular body,
thereby decreasing damage of the tubular body to elongate
its service life two or more times.
Fig. 10 illustrates another preferred embodi-
ment of the invention, wherein a protective layer 33 is
provided between a tubular body 1 and a braided
structure 2 such that even if the tubular body is
expanded 2-3 times, the tubular body 1 and the braided
structure 2 are not brought into contact with each
other and the protective layer 33 does not provide any
resistance to the expansion of the tubular body 1.
Fine fiber filaments similar to those used in the
braided structure 2 are made dense as high as possible,
for example, near to 100% and the filaments are finely
braided so as to be expansible and contractible as
in a tricot weave to form the protective layer 33.
- 18 -
3~
Fig. 10 illustrates such a protective layer of the
tricot weave.
With this arrangement, the tubular body does
not directly contact the reinforcing braided structure,
05 thereby eliminating the damage of the tubular body by
the reinforcing braided structure to remarkably improve
the life of the tubular body and hence the actuator.
Fig. 11 illustrates a further embodiment of
the invention, wherein a tubular body consists of two
elastic bodies in a double construction which are
a tubular body 1 and a protective layer 33 made of
materials different from each other. The material for
the protective layer 33 is an elastic material which is
high resistant to injury or damage and does not obstruct
the expansion and contraction as much as possible, for
example, a high molecular plastic material such as
urethane or the like. The protective layer 33 may be
glued to the tubular body 1 with a bonding agent or not.
Fig. 12 shows an actuator to which the
embodiment shown in Figs. 10 and 11 are applied, wherein
the like parts have been designated by the same reference
numerals as those in Fig. 1.
With the embodiments shown in Figs. 10-12,
the protective layer is provided between the tubular
body and the reinforcing braided structure to elongate
the life of the tubular structure to the order of
several million times of expansion and contraction
which is substantially near to times of inherent fatigue
- 19 -
~2
failure of the tubular body. With the simple and
inexpensive construction, a long life pneumatic actuator
is provided.
Referring back to Fig. 5, the broken line B
is fairly different from the theoretical line A due to
the restraint of both the ends of the braided structure 2.
Assuming that initial braided angles ~0 is
20, when contractive strains are 20%, a contracted
diameter D of the braided structure is obtained by
substituting the values of ~0 and into the equations
(2) and (3) as follows.
D - 1.93Do (~=41)
Therefore, if diameters of both ends of
a braided structure are previously set as twice as
a diameter of at its mid portion, constructive forces
should be substantially coincident with the theoretical
values as shown in a dot-and-dash line C in Fig. 5.
Braided angles at the ends having the twice diameters
are 41.
In consideration of this fact, according
to a further embodiment of the invention diameters at
ends of a braided structure are previously made larger
by an amount 10-20%.
In making such a braided structure 'naving
larger diameters at its ends, larger sized nipples may
be forced into a straight tubular body in assembling.
- 20 -
However, it is preferable to initially make a tubular
body having a configuration integrally with nipples as
shown in Fig. 13. Fig. 14 schematically illustrates
a braided structure 2 with nipples 5 made in this
05 manner, which will be radially expanded and axially
contracted as shown in Fig. 15.
With this arrangement shown in Figs. 13-15,
the diameters and braided angles at ends of a braided
structure are larger than those at its mid portion,
0 thereby improving the contracting performance and
fatigue strength of the braided structure and hence of
the actuator.
Referring to Fig. 16, wherein like parts have
been designated by the same reference numerals as those
in Figs. 1, 12 and 13, a filler 45 is filled in an inner
cavity of a tubular body 1 substantially without
obstructing the expansion and contraction of the tubular
body. The Eiller is preferably an incompressible fluid
substance having no constant shape as a whole, for
example, solid grain such as sand or ballast, a liquid
such as water or grease-like sticky substance or pellets
capsuled such a liquid therein, or a bar-like or
cylindrical elastic body flexible only in expanding and
contracting directions. With the solid grains, particu-
larly, they preferably form a mass having a grain sizedistribution so as to be filled in the cavity under the
densest condition.
With this arrangement of the filler assuming
- 21 -
~3~ '7
the cavity of the tubular body, the amount of the
controlled air corresponding to the total volume of the
filler can be saved.
This fact will be explained in more detail by
calculating the air volume to be used. When the cavity
of the tubular body is filled with a filler whose
volume is substantially equal to an initial volume of
the cavity, an inner volume Vc of the cavi-ty upon
applying the controlled air thereinto can be indicated
by -the following.
sin 2 COST
VC = 4d2(S1~.COS~1X - 1)Q ... ~5)
where d : inner diameter of the tubular body
Q: effective length of the tubular body
JO: initial braided angles
Hx: changed braided angles
On the other hand, an inner volume V of the
cavity without the filler upon applying the controlled
air is indicated by the following.
sin 2 COST
V = 4d2(sin~02 cost) ... (6)
Accordingly, a ratio fe of the used air for
expanding the tubular body in the above two cases is
obtained by the following equation (7).
to
sin 2 cosH
f = Vc = ( æ05~ - (7)
(sin~O 2 COST o )
As a contractive stress is indicated by the
cos~O -cOsa
equation = COST o . . . ( 2) as above mentioned,
cos~x is given by an equation (8)
cos~x = (l-)cos~O -- (8)
Substituting the equation (8) into the
equation (7) gives the following equation (9).
sin2~xcos~X - sin2~0cos~0
f = sin2~y cos~X
(l-cosæ~x)cos~x - sin2~0cos~0
(1-cos2~x)cos~
= {I )2COS2~ l-)cos~"-sin2~,,cos~"
-)2COS2~o}(,1-)COS~o
-- (9)
From the equation (9), values of fe are
obtained depending upon various values of in actual
cases with a constant initial braided angle 20 as
shown in Table 1.
Tablel
0.1 0.2 0.3
fe ~.59 0.73 0.79
As can be seen from the Table 1, using the
filler according to this embodiment can save the air to
be used per one operation by 30% or more in comparison
with those without the filler. Accordingly, the total
air consumption in operation can be considerably
economized.
The actuator shown in Fig. 16 is filled in
the cavity with the solid grains 45 as an incompressible
fluid substance having no constant shape as a whole,
and having a grain size distribution so as to be filled
in the cavity under the densest condition. In this case,
the cavity is separated from the center apertures 9 by
means of strainers 44 each having vent holes 43 located
at inner end of the nipple 5.
Fig. 17 illustrates an embodiment using
as a filler a bar-like elastic body 46 flexible only in
its expanding and contracting directions.
According to these embodiments shown in
Figs. 16 and 17, the actuator filled in its cavity with
a filler can greatly save its air consumption without
adversely affecting the advantages of the air-bag type
actuator to eliminate its disadvantage of much air
- 24 -
A 'rJI'r~la i
consumption.
Instead of the filler in the embodiments,
there may be in the tubular body an axially expansible
and contractlble tube made of a high pressure resistant
o5 corrugated membrane having an outer diameter substan-
tially equal to an inner diameter of the tubular body,
the corrugations being axially side by side with each
other, or a pneumatic or hydraulic damper in the form
of a piston and cylinder assembly.
lo Fig. 18 illustrates an articulated arm or
mechanical hand to which actuators according to the
invention are applied (only one actuator is shown),
wherein first and second arm members 51 and 52 are
connected by means of a universal joint 59. A holding
member 53 is fixed to the first arm member 51. To the
second arm member 52 is fixed a bracket 54 having three
protrusions 55 (only two protrusions are shown in the
drawing) arranged spaced apart 120 about an axis of
the bracket 54. The bracket may be integrally formed
with or separately formed from -the protrusions 55.
A stud 56 is pivotally connected to each the protrusion
55. Fittings 57 each having an opening for introducing
pressurized fluid or air into the actuator 58 (only one
shown) are connected to the stud 56, respectively.
The actuator 58 is provided at its one end with
an engaging portion adapted to engage the holding
member 53 and at the other end with a connecting portion
to be connected to the fitting 57 and is pivotally
- ~5 -
~3~L2~7
connected to the first and second arm members by means
of the holding member 53 and the fitting 57.
In this embodiment, although the three
actuators 58 are arranged spaced apart 120 about the
05 arm members, two actuators may be arranged spaced apart
180~ about the arm members as shown in Fig. 19.
The operation of the articulated arm will be
explained hereinafter referring to Fig. 19 for the sake
of simplicity. When pressurized fluid or air is supplied
o into the actuator 60, it is radially expanded but
axially contracted. As the result, the second arm
member 52 is subjected to a force owing to a contractive
force of the actuator 60, so that the second arm member
52 is rotated in a direction shown by an arrow F.
S If it is required to rotate the second arm member 52 in
a direction shown by an arrow G, the pressurized fluid
or air is supplied into the actuator 61. When it is
required to return the second arm member 52 to its
original position, the pressurized fluid or air supplied
in the actuator 10 is exhausted therefrom, while
pressurized fluid or air is supplied into the other
actuator 61.
In this embodiment, the first and second arm
members 51 and 52 are connected to each other by means
of the universal joint 59. The same operation may be
apparently accomplished in case of an articula-ted joint
permitting arm members to move pivotally in a plane.
Although the operation has been explained by
- 26 -
2~
referring to the embodirnent having the two actuators in
Fig. 19, the same operation can be achieved in the
embodiment having the three actuators in Fig. 18.
In the arrangement in Fig. 18, however, as the three
05 actuators are secured to the first and second arm
members 51 and 52 connected by the universal joint, the
second arm member 52 can be located at a desired position
in a space by suitably introducing the pressurized
fluid into the respective actuators.
0 Figs. 20a and 20b illustrate a preferred
embodiment of the invention. To one end of a second
arm member 52 is fixed a sheave or pulley 70 whose axle
71 is rotatably mounted in a first arm member 51.
One ends of two actuators 62 and 63 are pivotally
connected to the first arm member 51 by the use of
a holding member 53. The other ends of the actuators
62 and 63 are connected by a wire or rope 22 extending
about the pulley 70.
The operation of the arrangement shown in
Figs. 20a and 20b will be explained. When pressurized
fluid or air is introduced into the actuator 62, it is
axially contracted. As the result, the wire 72 is
pulled in a direction in which the actuators 62
contracts, so that the pulley 70 is rotated. Accordingly,
the second arm member 52 having the pulley 70 fixed
thereto is rotated in a direction shown by an arrow H.
If it is desired to return the second arm member 52 to
its original position, the pressurized fluid supplied
- 27 -
~Z3~7~
in -the actuator 62 is exhausted therefrom, while
pressurized fluid is supplied into the actuator 53.
Continuous supply of the pressurized fluid into the
actuator 63 brings the second arm member 52 into
05 a position shown in broken lines in Fig. 20a.
Although only one pulley 70 is used in this
embodiment, pulleys 70 whose axes are perpendicular to
each other may be fixed to ends of an intermediate arm
member 73 which connects first and second arm members
as shown in Figs. 21a and 21b. Two pairs of actuators
62, 63 and 64, 65 are connected to first and second arm
members, respectively to form an articulated arm capable
of operating in the same manner as in the articulated
arm for a manipulator as shown in Fig. 18. With the
embodiment shown in Figs. 21a and 21b, there is
an advantage in that large rotating angles of the arm
members are obtained.
As can be seen from the graph in Fig. 5, the
larger the contractive strain , the smaller is the
contractive force F. In other words, when the contrac-
tive strain iS small or the arm members start to
move, large forces act thereupon. On the other hand,
when the strain becomes larger, the contractive force
becomes smaller. tamely, in the event then the strain
iS larger, a smaller force suffices to rotate arms, so
that the arms can easily be moved to desired positions
even if the amount of the pressurized fluid is somewhat
changed. When using hydraulic or pneumatic cylinders,
- 2~
1~3~7~;~
such a preferable effect cannot be obtained, as shown
by a two-dot line I in Fig. 5 which is a relation
between displacement of the cylinder and output.
Figs. 22a and 22b illustrate a further
05 embodiment of the articulated arm for a manipulator.
One ends of shafts 80 and 81 pivotally connecting arm
members 51 and 52 extend outwardly of arm portions 83
of connecting members 82. Detecting means 84, for
example, potentiometer rotary encoders are fixed to the
arm portions 83 and adapted to engage the extending
ends of the shafts 80 and 81, respectively. With this
arrangement, angularly moved angles of the arm members
51 and 52 can be detected to determine their positions.
Moreover, the articu-lated arm can be moved in any
desired manner by controlling amount of the pressurized
fluid to be introduced into the actuators depending
upon the output of the detecting means 84.
As can be seen from the above embodiments
shown in Figs. 18-22, the articulated arm utilizes the
actuators shown in Figs. 7-17 so as to eliminate any
sliding resistance and loss at reduction gears and
thereby to operate very smoothly. As the actuators are
much lighter than other driving means, the articulated
arm does not require high strength arm members and
couplings, thereby enabling the articulated arm itself
to be very light.
Moreover, the articulated arm according to
the invention is driven by pressurized fluid without
- 29 -
~Z3~27~7
generating sparks, so that it can be used where there
is risk of inflammation and explosion. Furthermore,
the actuator according to the invention has the charac-
teristics in that the contractive force is larger when
05 the contractive strain is smaller but the contractive
force decreases, as the contractive strain increases.
Accordingly, when the articulated arm is started, the
large force acts on the arm members and the force
driving the arm members becomes smaller as the articu-
lo lated arm approaches a target. Such a movement of thearticulated arm approaching to the target is very
similar to the movement of a hand of a man toward
a target. Therefore, the manipulation of the articulated
arm according to the invention to a desired position is
so easy that an unskilled operator is able to manipulate
the arm with a very short exercise. Moreover, the
rotated angles to the arm members are detected by
monitoring means secured to the arm members to position
the arm members more exactly. Furthermore, the
articulated arm according to the invention can be
constructed so as to be able to automatically position
the arm members.
Fig. 23 illustrates a preferred driving
control system to which is applied the actuators
according to the invention. The actuators 110 and 111
have one end fixed to fixed walls and opposite ends
connected to a connecting member or mass point 112.
Reference numerals 113, 114, 115 and 116 denote flow
- 30 -
23~2~7
control valves preferable for the actuators, which are
electromagnetic flow control valves for controlling the
flow rate of pressurized fluid or air flowing in and
out of the actuators according to control signals from
05 control means.
Fig. 24 illustrates one example of the control
valve which is capable of changing coil voltage acting
upon an electromagnet 117 to continuously change the
force urging a valve body 118 toward a valve seat 119
lo against the energy of the pressurized fluid, thereby
controlling its flow rate. Other flow control valves
may be applied to the present system so long as they
can continuously control flow rate according to control
signals.
The operation of the arrangement shown in
Figs. 23 and 24 will be explained. When controlled air
pressure P is applied to the actuators, contractive
force F is indicated by the equation (4) above mentioned
and is modified as an equation (10).
F 4Do P {3(]-)2cos~0-l~ ... (4)
. KlP - K2P~ ... (10)
where
- 31 -
~L~Z~2~
1 4D sin2~0
... (11)
K2 = ~D2~
Under an equilibrium condition that reference
pressure Pl is applied to both the actuators 110 and
111, in order to move the mass point 112 through
distance the flowing-in control valve 113 is opened
and flowing-out control valve 114 is partially closed
to further apply a pressure LP to the actuator 110 is
response to a control signal from the control means.
On the other hand, the flowing-in control valve 115 is
partially closed and the flowing-out control valve 116
is opened to apply a pressure -UP to the actuator 111.
Accordingly, the actuator 110 is subjected to -the
pressure Pa=Pl+~P and the actuator 111 is subjected to
the pressure Pb=Pl-~P-
The force acting upon the mass point 112 isnewly assumed as F and calculated from the equation
(10) in the following manner.
F = Kl(Pl+~P)-K2(pl+Qp)a
- Kl(Pl-~P)+K2(Pl-~P)b ... (12)
where
- 32 -
7~7
on - Q - x
... (13)
~b Qo
where QO is a length of the actuators under a normal or
unloaded condition (the lengths of the actuators are
made equal for the sake of simplicity).
Substituting the equations (11) and (13) into
the equation (12) and arranging give the following
equation (14).
F = Kp~P - P1KXX ... (14)
where
p 2sin2~0~(Q - 3~cos2~ - 1}
... (15)
3~D2 cos2 û
x QOsin290
The equation (14) indicates a relation between
the force, pressure and displacement of the mass point
in Fig. 2.
In this case, the pressure is given in the
following.
3~3~
PoA fal a a2
... (16)
PoA - if I- poA - b2
al, fa2' fbl and fb2 are electromagnetic forces
of the flow control valves, respectively and A is
an effective sectional area of a nozzle portion 120 of
the electromagnetic flow control valves.
Assuming that input voltage Va to the coil is
proportional to electromagnetic force, input voltage is
applied to the electromagnetic control valves 113 and
114 of the actuator 110 so as to achieve the relation
of fal=PoA-KVa and fa =KVa (K is proportional constant).
From these relations, the following equation (17) is
obtained in consideration of the equation (16).
PoA~(PoA-KVa) < PaA KVa ... (17)
The equation (17) is modified to obtain
Pa=AVa which means that the input voltage can control
the pressure Pa of the actuator 110.
In general, however, the relation between the
input voltage and electromagnetic force involves the
problems of hysteresis and is non-linear. Accordingly
a control circuit for this system according to the
invention comprises a circuit for feedback compensation
shown in Fig. 25. An element GC(S) in the drawing
- 34 -
lX;~ 7
is a forward element, such as an integral or integral-
differential element. For example, when it is the
integral-differential element, the forward element is
Gc(S~=(l+TDS)/TIS. As the result, the input voltage Va
is proportional to the pressure Pa. Although there is
delay between Va(S) and Pa(S), it is a time-lag of
first order as shown in an equation (18), so that it
gives an approximate value without any trouble.
Pa(S) = Ts-+lVa(S) ... (18)
where Kv is a proportional sensitivity.
The similar compensation is effected as to
the actuator 111 to obtain the following equation (19~.
Pb(S) = TS+lVb(S) ... (19)
The force F acting on the mass point 112 is
given by F=Kp~P-PlKxx ... (14), a kinematic equation of
this system is indicated by the following equation (20).
mx+cx+PlKxx = Kp~P+D ... (20)
where m is mass of the mass point 112, c is an equivalent
coefficient of viscosity and D is an external force
acting upon this system. Fig. 26 illustrates a block
- 35 -
23~7~diagram for effecting positional control by -the system
representative of the equation (20) or shown in Fig. 23.
Accordingly, providing one integral element in each the
compensation element makes zero the steady-state deviation
05 of the system.
As can be seen from the equation (14), moreover,
with the driving control system according to the
invention, the force acting upon the mass point is
determined only by the pressure difference UP independ-
o ently from the reference pressure which may be set atvarious values. The system according to the invention
is insusceptible to external disturbance acting upon
actuators and exhibits a high compliance.
Although the system according to the invention
has been explained with the linear driving system, the
invention may be applicable to a rockable or swingable
system as shown in Fig. 27 or a system for controlling
force acting on a connecting portion. Flowing-in and
flowing-out control valves may be provided directly on
actuators. Valves formed integrally with fitting are
more preferable because they eliminate pipings for
supplying pressurized fluids.
The above driving control system according to
the invention comprising the four electromagnetic flow
control valves for controlling flow rate by changing
coil voltage acting upon electromagnets is superior in
responsibility in comparison with prior art systems and
able to do positional control of arms without being
- 36 -
~33L27~7
affected by inherent non-linearity of the system.
The flow control valves are inexpensive in comparison
with hitherto used servo-valves to greatly contribute
decrease of manufacturing cost. The system according
oS to the invention does not leak the pressurized fluid
under steady-state condition, so that the consumption
of the pressurized fluid is minimum and noise of exhaust
fluid is eliminated. In hitherto used systems adapted
to control pressure, higher the used pressure, larger
is the force acting on the system. In contrast herewith,
according to the invention, pressure difference is
utilized to change the force, so that the compliance of
the system can be changed by changing reference pressure
as the case may be.
While the invention has been particularly
shown and described with reference to preferred
embodiments thereof, it will be understood by those
skilled in the art that the foregoing and other changes
in form and details can be made therein without departing
from the spirit and scope of the invention.
