U.S. patent application number 16/913913 was filed with the patent office on 2020-10-15 for devices and systems for producing rotational actuation.
The applicant listed for this patent is QUALITY MANUFACTURING INC.. Invention is credited to Raymond Cooper, Kevin Richardson, Jeffrey A. Rose, Stephen Rose, Jeffrey John Sweda.
Application Number | 20200325918 16/913913 |
Document ID | / |
Family ID | 1000004926255 |
Filed Date | 2020-10-15 |
View All Diagrams
United States Patent
Application |
20200325918 |
Kind Code |
A1 |
Rose; Jeffrey A. ; et
al. |
October 15, 2020 |
DEVICES AND SYSTEMS FOR PRODUCING ROTATIONAL ACTUATION
Abstract
Devices and systems for producing rotational actuation are
described. More specifically, hydraulic and pneumatic actuators
that can produce and control rotational or joint-like motion are
described. An actuator may include a torus shaped cylinder
configured to enable rotation of the actuator. An actuator may
further include both a piston configured to rotate from a first end
of the torus shaped cylinder to a second end of the torus shaped
cylinder and a piston rod coupled to the piston.
Inventors: |
Rose; Jeffrey A.;
(Lexington, KY) ; Cooper; Raymond; (Irvine,
KY) ; Richardson; Kevin; (Louisville, KY) ;
Rose; Stephen; (Lexington, KY) ; Sweda; Jeffrey
John; (Lexington, KY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
QUALITY MANUFACTURING INC. |
Winchester |
KY |
US |
|
|
Family ID: |
1000004926255 |
Appl. No.: |
16/913913 |
Filed: |
June 26, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15235923 |
Aug 12, 2016 |
10718359 |
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16913913 |
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62208250 |
Aug 21, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B25J 9/146 20130101;
F15B 15/125 20130101; B25J 9/046 20130101; B25J 15/0009
20130101 |
International
Class: |
F15B 15/12 20060101
F15B015/12; B25J 9/14 20060101 B25J009/14; B25J 9/04 20060101
B25J009/04; B25J 15/00 20060101 B25J015/00 |
Claims
1. A dual directional actuator comprising: a torus shaped cylinder
configured to enable rotation of the dual directional actuator, the
torus shaped cylinder having a first end and a second end, the
first end including a first endcap and the second end including a
second endcap; a piston configured to rotate from the first end of
the torus shaped cylinder to the second end of the torus shaped
cylinder, the piston including a first piston chamber and a second
piston chamber; and a piston rod coupled to the piston, the piston
rod extending from the first chamber of the piston to the second
chamber of the piston.
2. The dual directional actuator of claim 1, wherein the piston and
the piston rod form a continuous uninterrupted torus.
3. The dual directional actuator of claim 1, wherein the dual
directional actuator comprises a hydraulic actuator for producing
rotary motion.
4. The dual directional actuator of claim 1, wherein the endcaps
include a through-hole that matches a radius of the piston rod and
is configured to receive the piston rod.
5. The dual directional actuator of claim 1, wherein the torus
shaped cylinder includes a first fluid port on the first end and a
second fluid port on the second end.
6. The dual directional actuator of claim 5, wherein the first
fluid port is in the first endcap and the second fluid port is in
the second endcap.
7. The dual directional actuator of claim 1, wherein the piston rod
includes a first piston rod end and a second piston rod end, the
first piston rod end being connected to the second piston rod end
by a linkage mechanism.
8. The dual directional actuator of claim 1, wherein the first
piston chamber comprises a piston extension chamber and the second
piston chamber comprises a piston retraction chamber.
9. The dual directional actuator of claim 8, wherein the piston rod
comprises a continuous toroidal piston rod extending from the
piston extension chamber to the piston retraction chamber.
10. The dual directional actuator of claim 9, wherein torus shaped
cylinder has a matching tongue and groove with the first endcap and
the second endcap, the matching tongue and groove being configured
to keep the torus shaped cylinder in alignment with the first
endcap and the second endcap.
11. The dual directional actuator of claim 1, wherein the piston
separates the torus shaped cylinder into a first chamber configured
to fill the torus shaped cylinder with a fluid media and a second
chamber configured to drain the fluid media from the torus shaped
cylinder to thereby cause rotational motion.
12. The dual directional actuator of claim 11, wherein the torus
shaped cylinder includes a port for filling and draining each of
the first chamber and the second chamber.
13. The dual directional actuator of claim 1, wherein the piston
rod includes a linkage mechanism configured to apply torque from
the actuator.
14. The dual directional actuator of claim 1, further comprising a
housing configured to retain the torus shaped cylinder inside the
housing.
15. The dual directional actuator of claim 14, wherein the housing
couples the first endcap and the second endcap to the torus shaped
cylinder.
16. A dual directional actuator comprising: a piston comprising a
piston extension chamber and a piston retraction chamber; and a
piston rod coupled to the piston, the piston rod extending from the
piston extension chamber to the piston retraction chamber, the
piston and piston rod comprising a continuous uninterrupted
torus.
17. The dual directional actuator of claim 16, further comprising a
torus shaped cylinder that includes the piston and piston rod.
18. The dual directional actuator of claim 17, wherein an end cap
is inserted onto the piston rod and coupled to the torus shaped
cylinder of claim, the endcap including a through-hole having a
radius approximately a same size as a radius of the toroidal piston
rod.
19. The dual directional actuator of claim 17, wherein the torus
shaped cylinder includes a first endcap and a second endcap.
20. The dual directional actuator of claim 19, wherein the first
endcap includes a first fluid port and the second endcap includes a
second fluid port, the first fluid port and the second fluid port
being configured to facilitate actuation of the dual directional
actuator using fluid media.
Description
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application 62/208,250, filed Aug. 21, 2015, and titled "DEVICES
AND SYSTEMS FOR PRODUCING ROTATIONAL ACTUATION," the entire
disclosure of which is hereby incorporated herein by this
reference, and to U.S. patent application Ser. No. 15/235,923,
filed Aug. 12, 2016, and titled "DEVICES AND SYSTEMS FOR PRODUCING
ROTATIONAL ACTUATION," the entire disclosure of which is hereby
incorporated herein by this reference.
TECHNICAL FIELD
[0002] This disclosure relates to devices and systems for producing
rotational actuation. More particularly, this disclosure relates to
actuators for producing and controlling rotational motion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] Non-limiting and non-exhaustive embodiments of the
disclosure are described, including various embodiments of the
disclosure with reference to the figures, in which:
[0004] FIG. 1 is a torus-shaped dual directional actuator,
according to one embodiment of the present disclosure with two
single actuation cylinders.
[0005] FIG. 2 is a piston of a dual directional actuator disposed
in an extension and retraction chamber, according to one embodiment
of the present disclosure with one dual actuation cylinder.
[0006] FIG. 3 is a piston and a piston linkage assembly with a
support guide/bearing, according to one embodiment of the present
disclosure.
[0007] FIG. 4A is a perspective view of a two pistons coupled to a
piston linkage mechanism according to one embodiment of the present
disclosure.
[0008] FIG. 4B is a single piston coupled to a linkage assembly,
according to the embodiment of FIG. 4A.
[0009] FIG. 4C is a perspective view of the piston linkage
mechanism of FIG. 4A.
[0010] FIG. 4D is a perspective view of a piston of FIG. 4A.
[0011] FIG. 5 is a perspective view of an internal actuator hose
path, according to one embodiment of the present disclosure.
[0012] FIG. 6A is a perspective view of a joint assembly with two
actuators, according to one embodiment of the present
disclosure.
[0013] FIG. 6B is another perspective view of the joint assembly of
FIG. 6A.
[0014] FIG. 6C is another perspective view of the joint assembly of
FIG. 6A, with two piston linkage mechanisms coupled by an actuator
linkage mechanism.
[0015] FIG. 7 is a simplified exploded view of a portion of a
hydraulic joint, according to some embodiments.
[0016] FIG. 8 is a simplified view of an example of a plastic
rotating joint, according to some embodiments.
[0017] FIG. 9 illustrates a portion of the plastic rotating joint
of FIG. 8 as a full assembly, as an assembly with a housing
removed, and as an assembly with the housing, end caps, and a-rings
removed.
[0018] FIG. 10 is a simplified perspective view of a pair of molded
actuators, according to some embodiments.
[0019] FIGS. 11A and 11 B illustrate views of a robotic arm,
according to some embodiments.
[0020] FIG. 12 is a simplified perspective view of a robotic
finger, according to some embodiments.
[0021] FIGS. 13A and 13B are simplified side views of a robotic
hand in a fully extended position and in a flexed position,
respectively, according to some embodiments.
[0022] FIG. 14 is a fluid containment system, according to some
embodiments.
[0023] FIGS. 15A-15D illustrate different views of the lip seal
assembly of the fluid containment system of FIG. 14.
[0024] FIGS. 16A and 16B are simplified perspective views of a
robotic hand, according to some embodiments.
[0025] FIG. 17 is a simplified hydraulic circuit diagram of a
hydraulic control circuit of a robot hand and/or a robotic arm,
according to some embodiments.
[0026] FIG. 18 is a simplified circuit diagram of a hydraulic
control circuit, according to some embodiments.
[0027] FIG. 19 is a simplified hydraulic circuit diagram of a
hydraulic control circuit for a robotic hand, according to some
embodiments.
[0028] FIG. 20 is a simplified hydraulic circuit for a two-finger
robotic hand with one sensor module between each of the four joints
per finger, according to some embodiments.
[0029] FIG. 21 is a simplified perspective view of a six-fingered
robotic hand, according to some embodiments.
[0030] FIG. 22 is a simplified circuit diagram of another
embodiment of a hydraulic circuit to operate joints of a robotic
hand, according to some embodiments.
[0031] FIG. 23 is a simplified flowchart illustrating a method of
controlling speed of a robotic arm, hand, or finger, according to
some embodiments.
[0032] FIG. 24 is a simplified circuit diagram of a control circuit
configured to control a robotic hand, according to some
embodiments.
[0033] FIG. 25 is a simplified block diagram of control circuitry
configured to perform embodiments disclosed herein.
[0034] FIGS. 26A and 26B are a simplified perspective view and a
simplified exploded view, respectively, of a robotic joint,
according to some embodiments.
DETAILED DESCRIPTION
[0035] The embodiments of dual directional actuators described
herein may include a toroidal actuation chamber formed by at least
one actuation cylinder. Coupled pistons may be disposed in the
actuation chamber. A fluid media (e.g., hydraulic fluid or air) may
flow into the actuation cylinders and may cause operation of the
dual directional actuator. Further, certain embodiments may include
coupling a plurality of dual directional actuators together to
increase an effective rotational range of the coupled actuators or
to increase the torque of rotational actuation.
[0036] The embodiments of the disclosure will be best understood by
reference to the drawings, wherein like parts are designated by
like numerals throughout. Components of the disclosed embodiments,
as generally described and illustrated in the figures herein, could
be arranged and designed in a wide variety of different
configurations. Thus, the following detailed description of the
embodiments of the systems and methods of the disclosure is not
intended to limit the scope of the disclosure, as claimed, but is
merely representative of possible embodiments of the disclosure. In
addition, the steps of a method do not necessarily need to be
executed in any specific order, or even sequentially, nor need the
steps be executed only once, unless otherwise specified.
[0037] In some cases, well-known features, structures, or
operations are not shown or described in detail. Furthermore, the
described features, structures, or operations may be combined in
any suitable manner in one or more embodiments. It will also be
readily understood that the components of the embodiments as
generally described and illustrated in the figures herein could be
arranged and designed in a wide variety of different
configurations.
[0038] While specific embodiments and applications of the
disclosure have been illustrated and described, it is to be
understood that the disclosure is not limited to the precise
configuration and components disclosed herein. Various
modifications, changes, and variations apparent to those of skill
in the art may be made in the arrangement, operation, and details
of the methods and systems of the disclosure without departing from
the spirit and scope of the disclosure.
[0039] FIG. 1 is a torus-shaped dual directional actuator 100,
according to one embodiment of the present disclosure. The actuator
100 includes two actuation cylinders 120, an inner (e.g., piston)
assembly 130, and a guide mechanism 102. The actuation cylinders
120 may be defined by a body or housing 110 of the actuator 100,
and may be coupled together in a toroidal shape.
[0040] A cross-section of the toroidal shape may be circular,
elliptical, or polygonal and may or may not be symmetrical and/or
include one or more flattened surfaces. Each actuation cylinder 120
may include a fluid port (not shown) to allow a fluid media (e.g.,
hydraulic fluid, air, or other suitable fluid) to flow into or out
of each of the actuation cylinders 120.
[0041] The piston assembly 130 may include two pistons 132. Each
piston 132 may be disposed within an interior of the toroidal
actuation cylinders 120 (e.g., within a single cylinder or portions
of both cylinders). The piston assembly 130 may further include a
linkage mechanism or more specifically a piston linkage mechanism
150. The linkage mechanism 150 may couple the pistons 132 together.
More specifically, the linkage mechanism 150 may connect, support,
and guide rotation of the two pistons 132 during operation of the
dual directional actuator 100.
[0042] In certain embodiments, the pistons 132 may form a single
piston with two piston heads. The single piston may travel between
the two actuation cylinders 120 as part of a dual actuation
bi-directional actuator 100. In some embodiments, the linkage
mechanism 150 may rotate in-line with the pistons 132, with the
pistons 132 and the linkage mechanism 150 rotating about a common
radius of rotation (e.g., the center of the diskshaped actuator
housing 110).
[0043] The guide or support mechanism 102 may act as a bearing or
sidewall of the actuator 100. Further, the guide mechanism 102 may
support or guide the coupled pistons 132 as they travel within the
actuation cylinders 120 (e.g., during operation of the dual
directional actuator 100). The guide mechanism 102 may be coupled
to the actuator housing 110 by a series of pins, screws, clamps, or
other suitable fasteners.
[0044] Certain embodiments of a dual directional actuator may
operate via hydraulic or pneumatic means. More specifically,
certain embodiments may pump hydraulic fluid through the actuation
cylinders 120, and other embodiments may pump air or other fluids
through the actuation cylinders 120. Accordingly, the actuator 100
may include seal components and configurations thereof which may
facilitate retention of any fluid traveling within the actuator 100
or actuation cylinders 120.
[0045] For example, one or more sealing components or fluid
channels may be integrated into or formed by one or more actuation
cylinders 120 or pistons 132 of the embodiment. Additionally, the
pistons 132 may be configured to couple with seals, O-rings,
washers, and other suitable sealing components or wear ring
technologies, which may prevent or substantially inhibit leakage of
fluid from the actuation cylinders 120.
[0046] In some embodiments, the piston assembly 130 can be
initially inserted into the actuation cylinders 120 as discrete
uncoupled parts. Stated differently, the piston assembly 130 may be
inserted into the actuator 100 as individual and uncoupled pieces
or components. Once inserted, the pistons 132 may be coupled
together by the piston linkage mechanism 150 and the support
mechanism 102 may be coupled to the actuator 100.
[0047] FIG. 2 is a perspective view of a dual directional actuator
according to one embodiment of the present disclosure. A dual
directional actuator may also be described as a rotating cylinder
configured with hydraulic and/or pneumatic seal rings. Stated
differently, a dual directional actuator may be described as a
torus-shaped hydraulic cylinder with a piston extension and a
retraction chamber.
[0048] The actuator of FIG. 2 is a dual directional hydraulic
actuator and includes two fluid ports 222, 224, with a fluid port
on either end of a piston 232 (e.g., proximal to the piston base
and proximal to the piston head). The piston 232 may travel in a
forward or backward direction within an actuation cylinder 220
based on the direction of fluid flow into or out of each of the
fluid ports 222, 224. Piston seals and rod seals (not shown) may be
incorporated into the actuator.
[0049] The actuation cylinder 220 may be filled and drained of a
fluid media through the fluid ports 222, 224 which may control
and/or produce rotation of the piston 232 (and the actuator as a
whole). The dual directional actuator may be coupled to a valve
assembly (not shown). The valve assembly may include fluid flow
direction controls and/or switching components to determine which
actuation cylinder receives the fluid media (e.g., from a pump in
fluid communication with the corresponding fluid port).
[0050] Simultaneously, the valve assembly may determine which
actuation cylinder communicates or drains fluid (e.g., to a fluid
reservoir in fluid communication with the corresponding fluid
port). The valve assembly, while coupled to one or more dual
directional actuators, may control the direction of rotation of the
actuators by producing a flow of a fluid media in the corresponding
direction within the actuation cylinders.
[0051] FIG. 3 is a perspective view of a piston assembly 300 that
has been removed from an actuator housing. The piston assembly 300
includes a linkage mechanism 350 coupling two pistons 332 together,
and a guide mechanism 302.
[0052] Some embodiments of a dual directional actuator may include
a connector or fastener (not shown) between individual pistons and
the linkage mechanism coupling the pistons together. The fastener
or connection between each piston and the linkage mechanism may
stabilize rotation of the pistons and may be configured with a
snap-in connection or a friction fit to facilitate assembly and
coupling of the pistons and linkage mechanism.
[0053] FIG. 4A is a perspective view of a two pistons 432 coupled
to a piston linkage mechanism 450 according to one embodiment of
the present disclosure. FIG. 4B is a single piston 432 coupled to a
linkage mechanism 450, according to the embodiment of FIG. 4A. FIG.
4C is a perspective view of the piston linkage mechanism 450 of
FIG. 4A. The linkage mechanism 450 may include a utility aperture
disposed in a center portion of the linkage mechanism 450. FIG. 4D
is a perspective view of a piston 432 of FIG. 4A.
[0054] The utility aperture 454 of the linkage mechanism 450 may be
configured to receive a shaft or coupling pin to enable a transfer
of rotational power from an actuator to another device, object, or
joint (e.g., a robotic limb or the like). Further, the utility
aperture 454 may receive a coupling pin to facilitate coupling the
linkage mechanism 450 to a linkage mechanism of an additional
actuator.
[0055] FIG. 5 is a perspective view of a dual directional actuator
500 illustrating an internal actuator hose path, according to one
embodiment of the present disclosure. As described, a dual
directional actuator 500 may include an actuator housing 510 to
define one or more actuation cylinders 520 or other components of
the actuator 500.
[0056] FIG. 5 illustrates two internal flow paths or channels 512,
514 incorporated into or defined by an actuator housing 510. The
flow paths 512, 514 defined by the actuator housing 510 may allow
fluid to flow to the actuation cylinders 520 and may control the
direction of fluid flow to and from the actuation cylinders 520.
Further, the internal flow channels 512, 514 may operate in place
of or in tandem with one or more hydraulic hoses (not shown)
coupled to one or more fluid ports of the actuator 500. In certain
embodiments, the internal flow channels 512, 514 shown in FIG. 5
may be replaced by hydraulic hoses (not shown) coupled to the fluid
ports and disposed along an outer perimeter of the actuator housing
510.
[0057] A dual directional actuator 500, with each of its components
or subcomponents, may be manufactured using one or more
three-dimensional printing technologies or injection molding. In
such cases, any hydraulic hoses to be coupled to the actuator may
be integrated as one or more internal flow channels 512, 514
coupled to one or more fluid ports.
[0058] The actuator housing 510 may define one or more internal
flow channels 512, 514 to prevent or limit internal leakage of a
fluid media. In other words, an actuator 500 may utilize one or
more internal fluid channels 512, 514 to communicate a fluid media
from a pump to one or more actuation cylinders 520 and into a fluid
reservoir, or vice versa.
[0059] One or more surfaces of an actuator 500 may be configured
with hard plating (e.g., nickel) after a three-dimensional print of
the actuator 500, or a portion thereof, has been completed. Hard
plating a portion of the actuator 500 may increase a hardness or a
density of one or more surfaces (e.g., interior and/or exterior
surfaces) of the plated portion of the actuator 500.
[0060] FIG. 6A is a perspective view of a joint (e.g., a robotic
joint) assembly 600 with two dual directional actuators 601, 603
coupled together, according to one embodiment of the present
disclosure. FIG. 6B is another perspective view of the joint
assembly 600 of FIG. 6A. FIG. 6C is another perspective view of the
joint assembly 600 of FIG. 6A, with two piston linkage mechanisms
650, 651 coupled together by an actuator linkage mechanism 656.
[0061] FIGS. 6A-6C generally and collectively illustrate a robotic
joint or joint assembly 600 formed by two dual directional
actuators 601, 603 coupled together. The actuators 601, 603 are
coupled together by a pin 656 disposed in the linkage mechanisms
650, 651 of each actuator 601, 603. The coupled actuators 601, 603
may rotate in the same direction and about the same radius of
rotation. Further, any suitable plurality of dual directional
actuators may be stacked or coupled together, and each individual
actuator may rotate approximately 90 degrees.
[0062] In a plurality of coupled dual directional actuators each
individual actuator may rotate 90 degrees in either direction
(e.g., clockwise or counterclockwise). Accordingly, two coupled
actuators (e.g., actuators 601, 603) may collectively rotate up to
180 degrees. Stated differently, the coupled actuators may enable a
rotational range of the robotic joint 600 that is approximately
equal to 180 degrees.
[0063] More specifically, two or more actuators may be coupled
together by a coupling pin 656 disposed through a utility aperture
or lumen of the linkage mechanism 650, 651 of each actuator. Two or
more coupled actuators may operate in a parallel configuration, and
may be free floating.
[0064] A joint assembly 600 may include a plurality of linkage
mechanisms 650, 651, 656, with a first linkage mechanism 650
coupling together two pistons of a single dual directional actuator
601, a second linkage mechanism 651 coupling two pistons of another
actuator 603, and a third linkage mechanism 656, or coupling pin
656, coupling two or more dual directional actuators 601, 603
together. Further, the coupled actuators 601, 603 may rotate in
phase or out of phase with one another, while still causing a joint
to rotate in substantially the same direction. By way of
non-limiting example, the actuators 601, 603 may rotate in an
opposite direction for a series connection (e.g., increasing
degrees of rotation), or in a same direction for a parallel
connection (e.g., increasing torque).
[0065] As described, a single actuator (e.g., the actuator of FIG.
1) may rotate approximately 90 degrees. However, a plurality of
actuators hydraulically and mechanically connected to rotate in
series may be coupled together to enable a rotational range greater
than 90 degrees. A tee may connect the ports of additional
actuators such that the port alignment of a second actuator is a
mirror image of a first actuator. For example, two actuators may be
coupled to one another and may enable a rotational range of 180
degrees. Similarly, three actuators may be coupled to one another
and may allow a rotational range of 270 degrees, and so on in
greater multiples of approximately 90 degrees.
[0066] Additionally, coupling a plurality of actuators together may
allow movement in complimentary or opposite directions (e.g.,
clockwise and counterclockwise rotation). The rotation of each
actuator may be controlled by a single directional valve or valve
assembly 660. The valve assembly 660 may be coupled to a plurality
of ports of the actuators. Further, the valve assembly 660 may
couple (e.g., fluidly couple or enable fluid communication between)
similar ports (e.g., input port) in a common or parallel
configuration (e.g., via at-connector).
[0067] As described, the coupling pin disposed in the linkage
mechanisms may couple the actuators together. The coupling pin may
extend to couple a greater number of actuators (e.g., three
actuators, four actuators, etc.). One actuator may form a first
half of the joint assembly, and another actuator may form a second
half of the joint assembly.
[0068] A joint assembly may include a touch sensor or an array of
touch sensors (e.g., linear sensor array) that may be used to
describe an object being grasped by a gripping system. The sensor
comprises a sensing cell that contains a stationary electrode and a
movable electrode. The sensing cell is filled with a conductive
fluid. The conductive fluid may convey charge between the
electrodes to prevent a potential difference between the electrodes
from causing an accumulation of charge. A dielectric fluid may
optionally be used instead of a conductive fluid. Dielectric and
conductive fluids may be referred to as electrically operative
fluids. A power source is connected to the two electrodes to form a
completed circuit through the conductive fluid.
[0069] Many different kinds of conductive fluid are possible
including water mixed with sodium chloride, calcium chloride, or
any other salt that creates an electrolyte when mixed with water;
vinegar; gallium; gallium alloys; wood's metal; gallium aluminum
alloy; sodium potassium alloy; and sulfuric acid. In general, the
conductive fluid may comprise any salt, acid, and/or base.
Non-toxic antifreeze, such as propylene glycol or glycerol, and/or
toxic antifreeze, such as ethylene glycol may be added to
water-based conductive fluids. Many conductive fluids are
commercially available including: Indium Corporation's Gallium
Alloy 46L with a melting point of 7.6 degrees Celsius; Rotometal's
Gallinstan with a melting point of -19 degrees Celsius. These
metals become liquid at warm temperatures and offer high
conductivity. Potassium chloride is available commercially from
sources, such as ColeParmer KCL 3M with saturated AgCl.
[0070] The choice of conductive fluid may depend on the cost,
safety, and precision desired. Gallium alloys and sodium potassium
alloy may be expensive. Sodium potassium alloy reacts violently
with air when heated, but then forms an oxide coating that inhibits
further reaction. Gallium aluminum alloy reacts violently with
water releasing hydrogen gas and does not have any inhibiting
activity. Additionally, the choice of conductive fluid will affect
the requirements of the power source and electrical property
measuring device. A highly conductive fluid may consume more energy
unless a low voltage source is used. A more resistive fluid may
consume more energy when a constant current source is used. A more
sensitive electrical property measuring device may also be required
for more highly conductive fluids.
[0071] One or more linear sensor arrays of the joint assembly
and/or the rotational hydraulic actuators may contain conductive
hydraulic fluid and prevent leaks. The hydraulic fluid in the
linear sensor arrays may have positive pressure. When contact
pressure is applied to the linear sensor arrays fluid may be forced
out of the sensor arrays. The force from the contact pressure may
act like a spring to remove the fluid, and cause the linear sensor
arrays to conform to the object applying the contact pressure. The
conformity may allow a geographic model to be determined from the
displacement measurements of the linear sensor arrays.
[0072] Displacement measurement devices may be configured to
measure displacement linearly, rotationally, and/or along any curve
or shape with any desired units of measurement. A magnetic or
optical encoder may be used to measure displacement for positions
where the distance to voltage curve is flat or has a very small
slope, such as may occur for large joints. The processor may
compute the angle between various locations of the joint based at
least partially on the electrical property measurements and may
account for the different displacement-angle relationships in each
cavity. The processor may also reconcile the angles computed from
the measurements by averaging the results or the like.
[0073] A calibration process may be used to calibrate the angle
measurements; Electrical property measurements from the maximum
extension, minimum extension, maximum retraction, and/or minimum
retraction positions may be compared with stored maximum and
minimum joint angles and/or measured maximum and minimum joint
angles to calibrate electrical property measurements from the
rotational hydraulic joint. The computed angles for one or more
joints may allow the processor to accurately determine the position
and/or location of one or more other components or items associated
with the joint, such as grippers, one or more skeletal components,
the limbs of the robot, hands, feet, and/or an object being gripped
using trigonometry. The computed angles may allow the geometry of
an object being gripped to be determined, and/or may enhance
control over movements of the robot.
[0074] In large joints, the displacement measurements may require a
higher degree of accuracy than can be provided by fluid
measurement. An encoder may be attached to large joints to measure
the displacement of the electrodes relative to one another, for
example, when the distance is greater than 1 or several inches. The
encoders may measure displacement for positions where the
displacement to voltage relationship of the cell is flat. The
measurement of electrode separation, in radial and/or linear sensor
cells, may switch between measurements by opposing cells,
measurements by magnetic encoders, averaging of measurements from
multiple methods, or any combination thereof. A magnetic or optical
encoder may be mounted to the axis of a relatively large joint. The
encoder may be an AMS22U5A 1 CLARL336 rotary position sensor
available from Bourns.
[0075] Any of the embodiments, materials, manufacturing techniques,
usages, variations, sensors, measurement devices, calculations,
processes, and/or other described attributes above may be modified
by any of the embodiments, materials, manufacturing techniques,
usages, and variations, sensors, measurement devices, calculations,
and/or processes described in U.S. patent application Ser. No.
13/854,693 filed on Apr. 1, 2013 and/or U.S. patent application
Ser. No. 13/854,710 filed on Apr. 1, 2013 attached hereto as
Appendices A and B, respectively. Moreover, many of the embodiments
described in Appendices A and B can utilize one or more of the
embodiments of the actuator described herein, and vice versa.
[0076] FIG. 7 is a simplified exploded view of a portion 700 of a
hydraulic joint (e.g., a robotic hydraulic joint), according to
some embodiments. In some embodiments, a complete robotic joint
will have another matching portion like the portion 700 illustrated
in FIG. 7. The portion 700 includes a housing 710 and an inner
actuator 720. The inner actuator 720 includes actuation cylinders
722A, 722B, pistons 724A, 724B, a piston linkage mechanism 726, and
a guide mechanism 728, similar to the actuation cylinders 120, the
pistons 132, the piston linkage mechanism 150, and the guide
mechanism 102, respectively, of FIG. 1.
[0077] A second mirror-image inner actuator (not shown) and housing
(not shown) would connect to the inner actuator 720 and housing 710
by an axle (not shown). The axle would be affixed to one side of
the housing 710. The second mirror image housing is free to rotate
around the axle in relation to the housing 710 with the assistance
of ball bearings (not shown). Thrust bearings (not shown) are
affixed between the inner actuator 720 and the second inner
actuator in order to allow reduced friction during rotation. An
inside of the actuation cylinders 722A, 722B may be
electro-polished to create a good surface finish. To decrease the
friction between the actuation cylinders 722A, 722B and seals of
the pistons 724A, 724B, a Teflon coating may be added to the inside
of the actuation cylinders 722A, 722B.
[0078] To reduce the cost of a robotic joint and increase the
degrees of rotation, a rotating joint actuated by fluid may be made
from plastic. The plastic joint may be molded from a high-strength
plastic such as polyether ether ketone (PEEK), and the PEEK
material may be compounded with Teflon to reduce friction. PEEK is
an example of a material that is able to withstand high pressures
that may be encountered while operating the portion 700 of the
hydraulic joint of FIG. 7.
[0079] FIG. 8 is a simplified view of an example of a plastic
rotating joint 800, according to some embodiments. The plastic
rotating joint 800 includes a continuous toroidal piston rod 808
that extends from an extension chamber 834 into a retraction
chamber (e.g., defined by a housing 810) of a toroidal cylinder
822. A linkage mechanism 826 for the piston rod 808 functions as
both a piston rod connector and a drive pin to apply torque for
joint actuation between the actuators or housing 810. The piston
rod 808 connects to both sides of a piston. The cylinder 822 can be
made from tubes of PEEK formed (e.g., thermoformed) into the shape
of a torus cylinder. The piston rod 808 and piston assembly can be
made from molded PEEK material. The piston's face of each chamber
can be connected by a center connection piece 826 attached to each
piston rod 808.
[0080] In some embodiments, the center connection piece 826
connects the actuating torus cylinder 822 to additional torus
cylinders to provide more rotation or torque. In some embodiments,
a connection pin 838 connect the actuator to a second half of a
rotating joint, when only a single actuator inside the joint 800 is
used. The connection pin 838 is perpendicular to the direction of
rotation and parallel to the axis of rotation. The connection pin
838 is the applicator of the joint torque between the actuators.
Accordingly, an actuator is connected to each housing 810 and the
actuators are connected together by the connection pin 838.
[0081] The toroidal cylinder 822 includes end caps 840, which
include piston rod seals 842 configured to prevent fluid leaking
out of the cylinder 822 in order to maintain pressure. Additional
seals may be added between the endcap 840 and the cylinder 822 to
prevent leakage between the endcap and the housing 810. A piston
rod bearing 844 external to the cylinder, made from material such
as PEEK, is used to support the piston rod 808 outside of the
toroidal cylinder 822. Additional bearings can be molded into the
piston 808 and endcaps 840 to further support the piston rod 808
and to reduce the force on the seals 842. Adding bearings on the
piston 808 and endcaps 840 on each side of a seal 842 is commonly
employed to increase seal life. Here a difference may be that the
piston, piston rod 808, and wear rings (e.g., rod bearing 844) are
all molded together as a single unit. The external rod bearing 844
prevents bending of the piston due to side loading from rotational
torque forces. The piston rod bearing 844 may be on both sides of
the piston rod 808, even though the piston rod bearing 844 of FIG.
8 is only illustrated on one side of the piston rod 808.
[0082] The torus cylinder 822 includes ports 846 used for
actuation, the cylinder, endcaps 840, the bearing 844, piston and
piston rod 808. The actuator is molded into a containment
encasement 810, which locks the endcaps 840 into position relative
to the cylinder 822. The encasement 810 may not make contact with
the piston rod 808 in order to eliminate friction between the
encasement 810 and piston rod 808. The endcap 840 and cylinder 822
may have matching tongue and groove to keep the endcap 840 and
cylinder 822 in alignment. A through-hole of the endcap 840 for
receiving the piston rod 808 may match the radius of the piston rod
808 to ensure a leak-free fit. While FIG. 8 illustrates the ports
846 in the side of the cylinder 822, the ports 846 may also be
through the endcaps 840 in some embodiments.
[0083] FIG. 9 illustrates a portion of the plastic rotating joint
800 of FIG. 8 as a full assembly 800A, as an assembly 800B with a
housing 810 removed, and as an assembly 800C with the housing 810,
end caps 840, and a-rings 952 removed. In the embodiment of FIG. 9,
piston 824 is a single molded piece with bearings (not shown) on
both sides of a piston seal groove.
[0084] The portion 800C illustrates a piston 956 including an
a-ring 952. In some embodiments, the piston seal 956 may be added
after the molding before insertion into molded cylinders 822. The
torus shaped cylinder 822 may include a solid rod or tube of PEEK
material, which is machined to tolerance and thermoformed into the
torus cylinder 822.
[0085] Once the torus cylinder 822 is shaped, the one piece molded
piston 824 and piston rod 808 is inserted into the torus cylinder
822. Next, the molded endcaps 840 with inserted a-ring seals 952
are slid over the piston rod into contact with the cylinder 822. In
some embodiments, the cylinder 822 may have a 15-30 degree lead in
chamfer to prevent seal damage upon insertion of the piston
assembly 824. A matching 15-30 degree angle on the endcap 840
presses into the 30 degree lead in chamfer of the cylinder 822. The
endcap 840 may also have an alignment tongue and groove, since a
hole inside the endcap 840 will have a radius that matches the
radius of the piston and rod assembly 824. This alignment groove
will ensure that the angle of the cylinder 822 is continued through
the endcap 840 so that the piston rod 808 will experience the same
radius throughout its rotation.
[0086] Once the cylinder 822, seals 952, piston 956 and rod 808,
endcap 840 and rod connector are assembled, this complete actuator
assembly 800B may be used as an insert for a housing 810 injection
molding operation (e.g., an encasement molding). The housing 810
may be molded around the actuator 800B in order to complete the
housing 810. The housing 810 is further used to maintain the endcap
840 in correct position with the torus cylinder 822. A notch 858
(FIG. 8) is provided in the endcap 840 so that the high strength
plastic housing 810 may act as a pressure containment vessel to
ensure the endcap 840 and cylinder 822 maintain integrity while
pressurized. The Full Assembly 800B is inserted into the housing
810, similar to the assembly 720 being inserted into the housing
710 of FIG. 7.
[0087] The joint design of FIGS. 8 and 9 with molded actuator 800
functions essentially the same as the joint half 700 of FIG. 7, and
the molded actuator 800 simply replaces the two-cylinder actuator
700 of FIG. 7. The molded actuator 800 of FIGS. 8 and 9 may still
employ a similar axle and thrust bearings between the actuators, as
illustrated in FIG. 7. The actuator 800 of FIGS. 8 and 9 may be
bolted to 1/2 of a joint cover/housing. In this configuration, the
actuation causes the joint to rotate 800. An advantage of the
molded design of FIGS. 8 and 9 is that rotation is increased to 160
degrees in comparison to 90 degrees of rotation afforded by the
actuator 700 of FIG. 7.
[0088] FIG. 10 is a simplified perspective view of a pair of molded
actuators 800D, 800E, according to some embodiments. Each one of
the molded actuators 800D, 800E includes a joint half similar to
those 800, 800A, 800B, 800C of FIGS. 8 and 9, and without showing
housings 810 (FIGS. 8 and 9) for simplicity. FIG. 10 illustrates
piston connectors 826 of the actuators 800D, 800E. A drive pin 1054
operably couples the piston connectors 826 of the actuators 800D,
800E together. Each side of the piston 824 is connected together by
the piston connectors 826. The piston connectors 826 are connection
mechanisms, via the drive pin 1054, for the actuators 800D,
800E.
[0089] An actuation force is applied from one of the joint halves
800D, 800E to the other of the joint halves 800D, 800E by the drive
pin 1054, which is attached to the piston connectors 826. To ensure
that the cylinder 822 and piston 824 operate properly throughout a
broad temperature range, a coefficient of thermal expansion must be
similar for both the piston rod 810 (FIG. 8) and cylinder 822. One
way to ensure uniform thermal expansion of components is to use the
same material for as many components of the actuators 800D, 800E as
possible.
[0090] In some embodiments, disclosed is a hydraulic actuator for
producing rotational motion. The hydraulic actuator includes a
piston rod and a piston, the piston rod attached to both sides of
the piston such that the piston rod extends from a piston extension
chamber into a piston retraction chamber. The piston rod is
attached to both sides of the piston. Together, the attached piston
and piston rod are a continuous uninterrupted torus.
[0091] In some embodiments, disclosed is a hydraulic actuator for
producing rotary motion including a torus shaped cylinder. The
torus shaped cylinder includes a fluid port on each end of the
torus cylinder. In some embodiments, the fluid port is in an endcap
on each end of the torus cylinder.
[0092] In some embodiments, the torus cylinder enables 180 degrees
of rotation or less. The piston rotates from one end of the torus
shaped cylinder to the other end of the torus shaped cylinder.
[0093] In some embodiments, The torus shaped cylinder is molded
from an engineering plastic. In some embodiments, this engineering
plastic includes a PEEK composite.
[0094] In some embodiments, a piston, piston rod, and wear ring are
molded into a single piece. In some embodiments, piston seals are
the only externally added component of the piston and rod
assembly.
[0095] In some embodiments, disclosed is a one-piece molded torus
shaped piston and piston rod assembly. In some embodiments, the
ends of the piston rod are connected together by a linkage
mechanism to create a continuous torus assembly.
[0096] In some embodiments, the piston and piston rod are a molded
thermoplastic of the same material as the cylinder. In some
embodiments, the molded piston and piston rod include a PEEK
composite.
[0097] In some embodiments, an end cap is inserted onto the piston
rod and attached to the torus shaped cylinder. In some embodiments,
the endcap has a through hole that has a radius that is about the
same as a radius of the toroidal piston rod.
[0098] In some embodiments, the cylinder includes a groove that
matches a slot in the endcap for assembly to maintain alignment of
the endcap in relation to the cylinder and piston.
[0099] In some embodiments, the actuators are inset molded into an
outer housing containing the torus cylinder and endcap. A through
port is molded through the housing to the port of each end of the
torus shaped cylinder.
[0100] In some embodiments, the endcap includes a groove on the
outside thereof into which flows a material forming an outer
housing, and which permanently affixes the endcap to the cylinder
and housing. In some embodiments, the endcap may not be
disassembled from and reassembled to the cylinder.
[0101] In some embodiments, disclosed is a hydraulic toroidal
actuator that is attached to half of a housing of a hydraulic
joint, and another hydraulic toroidal actuator is attached to
another half housing of the hydraulic joint.
[0102] In some embodiments, a pin may connect the actuator to a
second housing half (with approximately 160 degrees rotation) if
only one actuator is used.
[0103] In some embodiments, a linkage mechanism connects one
actuator to a second actuator inside a hydraulic joint. In some
embodiments, the linkage mechanism also secures each end of the
toroidal piston rod together. In some embodiments, the hydraulic
actuators can be stacked in parallel/series to increase the degrees
of rotation or the torque of a hydraulic joint. These actuators are
connected together by additional linkage mechanisms.
[0104] In some embodiments, a plastic torus cylinder and endcap
molded into a support housing encase both the cylinder and endcap
in a permanent assembly.
[0105] In some embodiments, Rotational joints with the actuators
700, 800 of FIG. 7 or 9 can be utilized in robotic arms and hands.
FIGS. 11A and 11 B illustrate views of a robotic arm 1100,
according to some embodiments. The robotic arm 1100 includes a
stationary base and horizontal rotary joint 1130, joints 1110A,
1110B, 1110C, and 1110D (sometimes referred to herein simply
together as "joints" 1110 and separately as "joint" 1110), and
links 1120A, 1120B, 1120C, 1120D, and 1120E (sometimes referred to
herein simply together as "links" 1120 and separately as "links"
1120). Each of the joints 1110 includes a pair of actuators (e.g.,
the actuators 700 and/or the actuators 800 of FIGS. 7 and/or 8,
respectively). The actuators of each joint 1110 may, in some
embodiments, be operably coupled together using a drive pin 1054,
as illustrated in FIG. 10.
[0106] The joints 1110 are coupled between the links 1120. For
example, link 1120A, which is connected to the stationary base
1130, is connected to the link 1120B by joint 1110A. Also, link
1120B is connected to link 1120C by joint 1110B. Further, link
1120C is connected to link 1120D by joint 1110C. Further, link
1120D is connected to link 1120E by joint 1110D.
[0107] One half (i.e., one of the actuators 700, 800) of each joint
1110 is coupled to one link 1120, and another half of the same
joint coupled to another link 1120. In this way, actuation of the
joint 1110 causes rotation of the robotic joints 1110 and links
1120. For example, half of joint 1110A is connected to link 1120A,
which is attached to the stationary base and horizontal actuator
1130. The other half of joint 1110A is connected to link 1120B.
When the joint 1110A is actuated, an angle of the link 1120B with
respect to the link 1120A will change. The same will occur upon
actuation of the other joints 111 OB, 111 OB, 1110C, and 111 OD,
affording a large degree of multi-joint maneuverability of the
structure of the robotic arm 1100.
[0108] FIG. 12 is a simplified perspective view of a robotic finger
1200, according to some embodiments. The robotic finger 1200
includes a stationary base 1230, links 1220, and joints 1210,
similar to the stationary base 1130, links 1120, and joints 1110,
respectively, as discussed with reference to FIG. 11. The robotic
finger 1200 of FIG. 12 includes four joints 1210. It should be
understood, however, that in some embodiments, the robotic finger
1200 may employ other numbers of joints 1210, depending on a
desired maneuverability of the robotic finger 1200. By way of
non-limiting example, the robotic finger 1200 may include only a
single actuator and still attain 90 or 170 degrees rotation
(corresponding to actuators 700, 800 respectively of FIGS. 7 and
8), depending on the internal actuator used or additional actuators
for each joint may be used to increase the degrees of rotation or
torque.
[0109] In some embodiments, disclosed is a robotic joint including
a toroidal hydraulic actuator connected to a housing. A first half
of the housing is connected to a single actuator, and a second half
of the housing is connected to a second actuator.
[0110] In some embodiments, however, only a single actuator is
used. In some such embodiments, the second half of the robotic
housing is connected to an actuator of the first half of the
housing by a drive pin.
[0111] In some embodiments, a robotic joint includes multiple
stacks of actuators inside a robotic joint housing. In some such
embodiments, each additional actuator is connected to an actuator
connected to a first housing by additional drive pins. The
additional actuators are also connected to a second housing
actuator by a drive pin.
[0112] In some embodiments, a first joint housing actuator is
connected to a first actuator and a second joint housing is
connected to a second actuator. In some such embodiments,
additional actuators are connected to a first housing actuator and
second housing actuator by additional drive pins.
[0113] In some embodiments, disclosed is a hydraulic robotic arm.
Valves for robotic joint actuation are located on the arm. The
valves are located on links between the joints.
[0114] In some embodiments, a hydraulic circuit (e.g., the full
hydraulic circuit) is mounted on a robotic arm. In some such
embodiments, a power unit (e.g., a power supply) for the hydraulic
circuit may be mounted off the robotic arm.
[0115] FIGS. 13A and 13B are simplified side views of a robotic
hand 1300 in a fully extended position and in a flexed position,
respectively, according to some embodiments. The robotic hand 1300
includes robotic arms 1340 stacked in parallel to create robotic
grippers. Each of the robotic arms 1340 includes at least one joint
1310 coupled between links 1320, similar to the joints 1110 and
links 1120 discussed above with reference to FIG. 11. While
conventional robotic arms do not typically function as a gripper,
as illustrated in FIG. 13, the power to weight ratio of the
actuators 700, 800 of FIGS. 7 and 9, which the joints 1310 include,
enables the robotic arms 1340 to function as both alone as an arm
or together as a hand (i.e., the robotic hand 1300).
[0116] In some embodiments, each of the joints 1310 may include the
same diameter of torus shaped cylinder 722, 822 (FIG. 7, FIG. 8)
for the internal actuators 700, 800 (FIG. 7, FIG. 8). Accordingly,
uniform actuation of the joints 1310 would result in a uniform
pressure applied to an object being grasped by the robotic hand
1300, assuming that the links 1320 are about the same length.
[0117] In some embodiments, different volume cylinders 722, 822
(FIG. 7, FIG. 8) may be used in the various joints 1310 of the
robotic hand 1300. For example, where two or more robotic arms 1340
function as a robotic hand 1300, a larger robotic arm 1340 may
allow actuation of the robotic arms 1340 as a robotic hand 1300. In
some embodiments, each of the robotic arms 1340 of the robotic hand
1300 may have its own robotic hand at the end thereof (not shown).
As a result, in some embodiments, the robotic hand 1300 may include
robotic arms 1340, each having its own robotic hand, and robotic
arms of these hands function as hands of a larger robotic arm 1340.
Accordingly, there may be three robotic arms and three robotic
hands in a single robot. These robotic arms as hands may use only
three of the joints 1310 for a gripping and the other joints 1310
may control another gripping system.
[0118] Referring now to FIGS. 11 A, 11 B, 12, and 13 together,
fluid of the robotic arms 1100, 1340, fingers 1200, joints 1110,
1210, 1310, and hands 1300 may be contained in an encapsulation
structure. The encapsulation structure starts at the inside of the
joints 1110, 1210, 1310. A lip seal around the joints 1110, 1210,
1310 seals fluid from escaping the robotic joints 1110, 1210, 1310.
The fluid is further funneled into the area of the joints 1110,
1210, 1310 where the ports (e.g., ports 846 of FIG. 8) are
connected to the joints 1110, 1210, 1310. The fluid is then run
through an additional fluid leakage port and hose back to the fluid
reservoir. The result is three hoses to the joint 1110, 1210, 1310;
a hose to the joint 1110, 1210, 1310 from a pump line of the valve,
a hose from the joint 1110, 1210, 1310 to the reservoir line of the
valve, and a separate hose for the fluid leakage containment
system. The hose from the valve to the reservoir and the hose to
the reservoir from the fluid containment system may join into a
single line to the reservoir past the flow valve of the meter out
speed controller of each joint 1110, 1210, 1310. Accordingly, only
two hoses from the hydraulic power unit to each joint 1110, 1210,
1310 of the arm 1100, 1340 may be sufficient. Alternatively, the
fluid containment hose may connect with other fluid containment
hoses from other joints 1110, 1210, 1310, which may all channel to
the fluid reservoir directly.
[0119] In some embodiments, disclosed is a robotic arm including a
hand on the end of the robotic arm. In some embodiments, the
robotic arm functions as the fingers of another (e.g., larger)
robotic arm. In some embodiments, the robotic arm functions
independent of other robotic arms. In some embodiments, the robotic
arm functions together with other robotic arms as a single robotic
hand.
[0120] FIG. 14 is a fluid containment system 1400, according to
some embodiments. The fluid containment system 1400 may be employed
to prevent fluid from leaking out of a robotic joint 1110, 1210,
1310 (FIGS. 11, 12, and 13), which may occur from leaking seals
inside a hydraulic cylinder. Additional benefits of a sealed
hydraulic joint is the reduction or elimination of contaminates
entering the cylinders, which creates a failure mode for
hydraulics.
[0121] The fluid containment system 1400 includes a first joint
shell 1472, a second joint shell 1484, thrust bearings 147 4, a
joint axle/shaft 1476, an encoder 1480, an encoder guard 1478, ball
bearings 1482, and a lip seal assembly 1500. The lip seal assembly
1500 keeps the fluid contained inside the robotic joint 1110, 1210,
1310. A port (not shown) is connected to the housing of the robotic
joint 1110, 1210, 1310. This port will receive all leaked fluid
inside the joint and allow the leaked fluid to flow to the
reservoir. Further, all the port fittings may be contained in a
housing so that any fitting leakage is also funneled into the fluid
containment hose port. In this manner, little to no fluid leakage
will leave the contained robot environment. In some embodiments,
halves of housing/shells 1484 and 1472 may be sealed. The drive pin
between the actuators would have a seal as it is the only component
that is mechanically rotating between the half shells/housings. The
drive pin may have a permanent seal that rotates through a seal
housing (not shown).
[0122] FIGS. 15A-15D illustrate different views of the lip seal
assembly 1500 of the fluid containment system 1400 of FIG. 14. FIG.
15A is a perspective view of the lip seal assembly 1500. FIGS.
15B-15D are different cross-sectional views of the lip seal
assembly 1500. The lip seal assembly 1500 includes a rigid (e.g.,
aluminum) band 1592 defining a groove 1594 therein. The lip seal
assembly 1500 also includes a lip seal 1590 inserted into the
groove 1594 of the rigid band 1592. In some embodiments, the lip
seal 1590 may be bent at about a 90.degree. angle, as illustrated
in FIGS. 15A-15D.
[0123] In some embodiments, the lip seal 1590 may include a
rubber-type material designed to seal leaked fluid inside the
hydraulic joint. The complete lip seal assembly 1500 of FIGS.
15A-15D is affixed to the second joint shell 1484 of FIG. 14. The
90 bent lip seal 1590 is free to slide relative to the rotation of
the first joint shell 1472 of FIG. 14. In this manner, the fluid is
sealed within the joint.
[0124] As illustrated in FIG. 15C, the lip seal assembly 1500 also
includes a stationary seal 1596 inside a first joint half 1586. The
stationary seal 1596 is stationary and may be attached by cap
screws 1598. The lip seal 1590 of second joint half 1588 is held in
place by the rigid band 1592, within the groove 1594. The lip seal
1590 remains stationary with reference to the first joint half
1586, and the second joint half 1588 rotates along the lip seal
1590 to entrap all fluid leakage inside the joint.
[0125] In some embodiments, disclosed is a hydraulic joint
providing rotational motion, the hydraulic joint including a fluid
sealing mechanism. The fluid sealing mechanism isolates fluid
leakage from an actuator inside the joint.
[0126] In some embodiments, a fluid sealing mechanism includes a
port to transfer fluid out of the joint to a fluid reservoir. In
some such embodiments, the port includes a sealed housing that
includes ports (e.g., all ports) for joint actuation. A fluid
containment port has fittings attached to the port containment
housing.
[0127] The port to transport leaked fluid out of the joint is
connected to a fluid reservoir.
[0128] In some embodiments, a hydraulic robotic joint is sealed to
prevent internal joint leakage from escaping a robot including the
robotic joint. The robot includes a fluid leakage line ported from
the joint. A fluid leakage port connects to a common tank line from
robotic joints after the meter out flow control valve, so that a
pressure of a fluid containment hose is the same as a reservoir
pressure.
[0129] In some embodiments, a fluid leakage port includes an
isolated hose that transports the fluid directly to the fluid
reservoir. In some embodiments, multiple hydraulic joints may be
connected to the isolated fluid reservoir hose.
[0130] In some embodiments, the fluid sealing mechanism includes a
lip seal between actuator half sections. In some embodiments, each
actuator half section of a robotic joint is sealed
individually.
[0131] In some embodiments, a joint half section includes a rubber
seal that extends from a first joint half to a second joint half. A
joint of the second joint half rotates inside the rubber seal to
contain fluid leakage. The rubber seal may is stationary and
affixed to the first joint half.
[0132] FIGS. 16A and 16B are simplified perspective views of a
robotic hand 1600, according to some embodiments. The hand fluid
containment system includes a string of joints 1610 and links 1620,
similar to the joints 1110, 1210, 1310 and links 1120, 1220, 1320
of FIGS. 11, 12, and 13. As illustrated in FIG. 16A, the links 1620
include sensor pistons 1630 configured to extend from the links
1620. Also, as illustrated in FIG. 16B, the links 1620 include PEEK
coiled tubing 1680 thereon.
[0133] The system 1600 also includes a robotic skin 1670 covering
at least a portion of the string of joints 1610 and links 1620. The
robotic skin 1670 is designed to contain leakage of hydraulic
fluid, enclose hydraulic components of a robotic arm and/or robotic
hand (e.g., all the components of the robotic arm and robotic
hand), and cushion impact of the robotic arm and/or the robotic
hand with objects and people. The robotic skin 1670 may include a
soft resilient material, such as silicon or rubber. The robotic
skin 1670 is also designed to function as a fluid transport system
to contain any leakage of hydraulic fluid.
[0134] The robotic skin 1670 includes joint bellows 1650 configured
to accommodate for rotation of the joints 1610. The robotic skin
1670 also includes sensor piston bellows 1660 configured to
accommodate for extending and retracting of the sensor pistons
1630. For example, sensor piston bellows 1660A is illustrated in a
flexed position, and the other sensor piston bellows 1660 are
illustrated in an un-flexed position.
[0135] In some embodiments, disclosed is a robot skin for a robot.
The robot skin includes hydraulic fluid of the robot. The robot
skin is sealed with a connection to a hydraulic fluid reservoir.
Leaked fluid is transported to the hydraulic fluid reservoir inside
the robotic skin.
[0136] In some embodiments, the robot skin includes a port to
connect to the hydraulic fluid reservoir for fluid leakage.
[0137] In some embodiments, the robot skin encases hydraulic hoses,
electrical circuits, hydraulic circuits, sensors and wires (e.g.,
all the hydraulic hoses, electrical circuits, hydraulic circuits,
sensors, and wires).
[0138] In some embodiments, the robot skin applies a pressure on a
robotic arm and/or hand covered thereby in order to force fluid to
the hydraulic fluid reservoir.
[0139] FIG. 17 is a simplified hydraulic circuit diagram 1700 of a
hydraulic control circuit of a robot hand and/or a robotic arm,
according to some embodiments. The hydraulic circuit 1700 is
configured to allow manual teaching of a robot. During a teach
mode, a float center valve 17 40 is moved to a center position, a
flow control valve 1730 (e.g., an electro-proportional flow control
valve) is closed, and a two-way valve 1770 is open. In this state,
fluid channels of rotating actuators 1760 (e.g., actuators 700, 800
of FIGS. 7 and 8) are connected together so that there is little or
no pressure difference between the rotating actuators 1760 of a
hydraulic joint.
[0140] The flow control valve 1730 may be opened to lower the
pressure in the actuators 1760 to a desired pressure for manual
manipulation or a pressure to the arm may be controlled by
controlling pump pressure to the arm for lift assist, when a
direction of manual teaching is known. The pressure in the
actuators 1760 may be monitored by pressure transducers 1750, or
the like. The float center valve 17 40 is shifted to the center
position so that a person can manually move the robotic arm, but
the direction valve 17 40 may be dithered between a direction and
center position for lift assist active control. In a manual teach
mode operation, the two way valve 1770 is set in the open position
to allow flow through the two way valve 1770. A force/torque sensor
(not shown) can measure the force that a human pushing on a robotic
joint exerts. With the use of force/torque sensors (not shown), a
robot control program (e.g., implemented on a processor operably
coupled to a computer-readable storage medium including
computer-readable instructions stored thereon, the
computer-readable instructions configured to instruct the processor
to perform functions of the robot control program) may perform lift
assist in order to make the robotic arm easier to manipulate for
the teach mode operation. The force/torque sensor makes possible
the use of active control for lift assist of the robotic arm for
manual teaching by a human operator. An electro proportional
pressure control on a variable displacement pump may be used to set
the pressure to compensate and cancel the torque applied to a
robotic joint/arm/hand from gravity. The gravity canceling through
hydraulic pressure control enables gravity free manual
manipulation. Regulating the flow control valve of each joint and
dithering the directional valve can accomplish additional pressure
control. The pressure is set to exactly balance the arm with
respect to weight of the arm and payload.
[0141] FIG. 18 is a simplified circuit diagram of a hydraulic
control circuit 1800, according to some embodiments. The simplified
hydraulic circuit 1800 includes five hydraulic control circuits
1700, as discussed with reference to FIG. 17, for a teach mode
robot. Each of the hydraulic control circuits 1700 may be
configured to control a different joint of a robotic arm and/or
hand.
[0142] FIG. 19 is a simplified hydraulic circuit diagram of a
hydraulic control circuit 1900 for a robotic hand, according to
some embodiments. The robotic hand includes a rotating actuator
1960. A hydraulic circuit branch controls the fluid in the linear
electrochemical sensor and another branch controls the finger
joints. The pressure in the linear sensors is controlled by a
pressure reducing valve 1910 and a pressure relief valve 1920. In
some embodiments, the pressure to the hand may be reduced from pump
pressure by a single pressure reducing valve 1910. The linear
sensors may require a lower pressure or a variable pressure, which
is different than the pressure in the robotic joints. This is
because a specified gripping force may be used in the robotic
joints, and the pressure may be specified lower in the sensors so
that the sensors may conform to the shape of an object being
gripped.
[0143] In the example illustrated in FIG. 19, a two-way valve 1970
may be energized in such a way as to stop flow to the sensors.
Then, the pressure may be lowered in the sensor by setting the
pressure relief valve 1920 to the desired pressure of the linear
electrochemical displacement sensors. This variable pressure
control will ensure the sensors conform to the object and apply the
exact desired pressure to the object. An accumulator 1980 may be
connected directly to the hydraulic linear displacement sensor
modules instead of pressure supplied from the pump. The accumulator
bladder in the circuit 1900 acts as a spring to allow the sensors
to conform to the shape of an object, and the pressure in the
accumulator 1980 is used to apply pressure to an object through the
sensor module.
[0144] FIG. 20 is a simplified hydraulic circuit 2000 for a
two-finger robotic hand with one sensor module between each of the
four joints per finger, according to some embodiments. Finger
joints 2010 of the robotic hand are connected in pairs 2012 so that
a one-directional valve 2014 controls the set 2012 of equivalent
joints 2010 of each finger of the robotic hand. A first directional
valve 2014 controls a first set 2012 of joints 2010 for each
finger. A second directional valve 2014 controls a second set 2012
of joints 2014 from each finger, and so on. As a result, each pair
2012 of joints 2010 of the circuit 2000 includes a separate
one-directional valve 2014. FIG. 20 illustrates the simultaneous
control of a joint of each finger for more than one finger. In some
embodiments, more than one actuator may be used to increase the
degrees of rotation or torque, and these would be added with
fittings and porting with no additional valves.
[0145] A pressure transducer (not shown) can be inserted in the
linear electrochemical sensor hydraulic hose line and/or the
hydraulic joint hose line to evaluate and control pressure. FIG. 16
illustrates one embodiment of a hydraulic joint pair configuration.
Pressure compensated flow control valves may be employed to ensure
that each joint of the finger pair move at the same speed.
[0146] FIG. 21 is a simplified perspective view of a six-fingered
robotic hand 2100, according to some embodiments. The six-fingered
robotic hand may operate such that a first two fingers 2130A, 2130B
have individual joint control or joint control in pairs 2012 (i.e.,
2012A, 2012B, 2012C, 2012D). The remaining four fingers 2130C,
2130D, 2130E, and 2130F may have individual or pair 2012 control of
the joints 2110. However, often only grasping is needed for the
remaining fingers 2130, and therefore the remaining fingers 2130
may all open and close with a single directional valve 2014 per
finger 2130.
[0147] FIG. 22 is a simplified circuit diagram of another
embodiment of a hydraulic circuit 2200 to operate joints 2210 of a
robotic hand 2230, according to some embodiments. The hydraulic
circuit 2200 may be used to control a single joint 2210, a joint
pair, a robotic finger 2232 of the robotic hand 2230, or multiple
robotic fingers 2232 of the robotic hand 2230.
[0148] In some embodiments, disclosed is a hydraulic circuit for a
robotic arm. The hydraulic circuit is designed to allow manual
teaching of the robotic arm by moving the robot manually and
recording the movements for playback.
[0149] In some embodiments, for teach mode operation, a meter out
flow control valve to tank is closed, a pump line to a joint is
closed, a two-way valve between actuators of the joint is opened to
enable flow between extension and retraction chambers of a
hydraulic actuator of the joint. These valve positions are set
during a teach mode command.
[0150] In some embodiments, hydraulic robotic joints are moved
manually and the movements are recorded for playback.
[0151] In some embodiments, active control of a hydraulic joint is
implemented during a teach mode operation to assist the manual
operation.
[0152] In some embodiments, active control in the teach mode
operation will work to cancel the forces of gravity, payload, and
hydraulic stiffness by switching the valve in response to force
torque sensors to zero the torques of the robotic arm.
[0153] In some embodiments, a pressure transducer measures pressure
in a hydraulic robotic joint, and a flow control valve is opened to
lower the pressure in the joint to make the joint easier to
move.
[0154] In some embodiments, a force/torque sensor zeroes forces
(e.g., all forces) on the robotic arm through directional and flow
control valves except the force applied by a human to manually move
the robotic arm.
[0155] In some embodiments, disclosed is a hydraulic circuit for a
robotic gripper including hydraulic linear displacement sensors. In
some embodiments, hydraulic rotary joints and the hydraulic linear
displacement sensors are pressurized from a same hose from a pump.
In some such embodiments, the hydraulic circuit is connected to a
hydraulic circuit of a hydraulic robotic arm. The hydraulic circuit
operates at a lower pressure than a hydraulic arm circuit. A
pressure reducing valve lowers the pressure to the hydraulic
circuit for the robotic gripper. In some embodiments, a pressure
relief valve is connected between a tank and a supply line of the
hydraulic linear displacement sensors. The pressure of the
hydraulic linear displacement sensors is set by the pressure relief
valve, which may be different than the pressure of the joints or of
the gripper.
[0156] In some embodiments, a two-way valve is added to a hydraulic
circuit of the hydraulic linear displacement sensors to isolate the
pressure of the sensors from the pressure of the pump and robotic
hand hydraulic joints.
[0157] In some embodiments, a flow meter is located at a pump
outlet to measure flow out of a hydraulic pump. A flow meter is at
a reservoir of a hydraulic power unit to measure flow going into
the reservoir. If the flow leaving the pump is not substantially
equal to the flow entering the reservoir, the pump and flow to the
hydraulic circuit is turned off, as such conditions indicate that a
leak has occurred.
[0158] In some embodiments, disclosed is a hydraulic circuit for a
robotic hand. The robotic hand includes robotic fingers including
joint pairs that are controlled by a single hydraulic directional
valve. In some embodiments, the joint pair includes a flow
regulator to ensure that flow to all the joint pairs is equal.
[0159] In some embodiments, disclosed is a robotic hand hydraulic
circuit. Linear hydraulic cylinders make contact with an object and
a rotating joint applies rotational force to the object. The linear
hydraulic cylinders control an applied force to the object by the
robotic hand by controlling a pressure in the linear cylinders
independently of a pressure in the finger joints. In some such
embodiments, the linear hydraulic cylinders have a different
pressure than a pressure of the rotating joints.
[0160] In some embodiments, disclosed is a robotic hand configured
to individually control a hydraulic joint of two fingers, and
control remaining fingers with open and close hydraulic control
only.
[0161] In some embodiments, disclosed is a robotic arm with
hydraulic actuation. Hydraulic control valves (e.g., all of the
hydraulic control valves) for the motion of each hydraulic joint
are located on the robotic arm at each individual joint.
[0162] FIG. 23 is a simplified flowchart illustrating a method 2300
of controlling speed of a robotic arm, hand, or finger, according
to some embodiments. One issue confronted by designers of robotics
is momentum and speed with varying loads. A simple method to
control both the momentum and speed of a hydraulic robotic arm is
with a speed control method 2300. This method 2300 is specific to
hydraulic control. To execute the speed control algorithm, the
hydraulic circuit 2200 (FIG. 22) uses an encoder at each robotic
joint 2210. A processor (e.g., a microprocessor) sets the desired
speed of the robotic joints 2210, which may be a kinematic function
of end effectors speed and position.
[0163] The method 2300 includes setting 2310 the desired speed,
monitoring 2320 each individual joint speed, and controlling 2330
the joint speed. Controlling the joint speed includes taking 2332
an encoder reading, incrementally opening 2334 a joint flow control
valve if the joint speed is too slow, and incrementally closing
2336 the joint flow control valve if the joint speed is too high.
The taking 2332 an encoder reading and incrementally opening 2334
and closing 2336 the joint flow control valve depending on the
joint speed is repeated during operation.
[0164] This method 2300 is used with both ramp down and ramp up
speed control to slowly stop and start joint 2210 (FIG. 22)
movements. The method 2300 automatically compensates for load,
momentum, and kinematic end effectors' speed. The repeatability can
be increased by correcting for the error in accuracy by adding or
subtracting the undershoot or overshoot to the next operation. For
example, if the programmed movement is 60 degrees, and the encoder
reads a movement of 60.1 degrees, the return position would move
back 60.1 degrees with an error of plus 0.1 added to the move back
to 0 degree position. This effectively increases the repeatability
of the movements and the accuracy of subsequent movements.
[0165] In some embodiments, disclosed is a velocity control
algorithm that monitors the speed of hydraulic robotic joints from
a preset speed. In some embodiments, the algorithm includes opening
a flow control valve to increase the joint speed if the speed is
too slow. In some embodiments, the algorithm includes closing the
control valve to slow the joint speed if the speed is too fast. In
some embodiments, the speed control algorithm is applied to each
joint of a robotic arm and/or hand individually.
[0166] FIG. 24 is a simplified circuit diagram of a control circuit
2400 configured to control a robotic hand, according to some
embodiments. The control circuit 2400 includes joints 2410 and
links 2420 of a robotic hand, according to embodiments disclosed
herein. The control circuit 2400 also includes two-way valves 2422
operably coupled to the joints 2410, as illustrated in FIG. 24. The
control circuit 2400 also includes a hydraforce closed center valve
2414 operably coupled to the links 2410, the two-way valves 2422, a
flow control needle valve 2416, and a pressure reducing valve 2418.
The two-way valves 2422 can be pulse width modulated (PWM) to
control the speed of each joint 2410 of the robotic hand. In this
way, the robotic joints 2410 can be made to close at the same speed
regardless of payload, gravity, or frictional variances internal to
the joints 2410. The two-way valves also enable positional control
of each individual joint 2410.
[0167] FIG. 25 is a simplified block diagram of control circuitry
2500 configured to perform embodiments disclosed herein. For
example, the control circuitry 2500 may be configured to implement
the method 2300 of FIG. 23, and other methods disclosed herein. The
control circuitry 2500 includes one or more processors 2504
operably coupled to one or more data storage devices 2502 and
hydraulic circuitry 2506 (e.g., hydraulic circuitry disclosed with
regards to FIGS. 17-20 and/or 24).
[0168] In some embodiments, the processors 2504 may include a
microcontroller, a central processing unit (CPU), a programmable
logic device (e.g., a field programmable gate array (FPGA), a
programmable logic controller, etc.), or other device configured to
execute computer-readable instructions.
[0169] The data storage devices 2502 include non-transitory data
storage. By way of non-limiting example, the data storage devices
2502 may include one or more of random access memory (RAM), read
only memory (ROM), Flash, electrically programmable read only
memory (EPROM), optical discs and disc drives (e.g., compact disc,
digital versatile disc, a hard drive, a solid state drive, other
data storage devices, or combinations thereof. The data storage
devices 2502 are configured to store computer-readable instructions
configured to instruct the processors 2504 to perform embodiments
disclosed herein.
[0170] FIGS. 26A and 26B are a simplified perspective view and a
simplified exploded view, respectively, of a robotic joint 2610,
according to some embodiments. The robotic joint 2610 includes a
center section 2612 and two outer sections 2614. The center section
2612 is configured to rotate, and the two outer sections 2612 are
configured to remain stationary. Outer housing halves of the two
outer sections 2614 are attached together (e.g., by a connecting
member 2616) so that the inner center section 2612 rotates in
relation to the outer housing halves.
[0171] Each of the outer sections 2614 includes an actuator 2684
(e.g., hydraulic actuators), which may be similar to any of the
actuators previously discussed herein. In contrast to embodiments
disclosed above (in which actuators are shown connected in series
to increase degree of rotation), however, the actuators 2684 are
connected in parallel to increase a total torque in rotating the
center section 2612 (e.g., analogous to series and parallel
connected electrical circuits).
[0172] The center section 2612 is a parallel hydraulic connection
that adds the torque from each actuator 2684 together. Thus
connected, higher power is delivered to the center section 2612
than if only a single actuator 2684 were driving the center section
2612. Both actuators 2684 may rotate together, and the torque of
each actuator 2684 is cumulative to the center section 2612. The
rotation of the joint 2610, however, is not cumulative. Rather, the
torque generated by each actuator 2684 is cumulative.
[0173] One difference between parallel connected actuators and
series connected actuators is that the actuators are bidirectional
and move incrementally in proportion to the amount of fluid added
to the actuator cylinders. The parallel configuration may have the
actuators located in the center with rotating section located in
the housing as an alternative design.
[0174] In some embodiments, disclosed is an arc-shaped piston guide
exterior to torus shaped cylinders, the arc-shaped piston guide
configured to support, guide, and provide a low wear surface for a
piston. The piston guide may be on one or both sides of the piston
external to the torus cylinder.
[0175] In some embodiments, an axle supports dual actuator
assemblies. The axle is fixed and stationary with respect to a
first actuator and housing on one end of the axle. A second
actuator and housing is free to rotate on the axle on a second end
of the axle.
[0176] In some embodiments, an axle aligns and supports two
actuators in which the two actuators remained in fixed stationary
alignment. A rotating member is located between the two stationary
actuators, in which the rotating member rotates on the axle. The
rotating member is driven by the rotation of torus pistons of the
actuators. Drive pins are connected to the rotating member from
each stationary actuator piston to cause rotation.
[0177] In some embodiments, disclosed is a plastic rotating joint
including a piston rod, a rotatory actuator, and a torus cylinder.
The piston rod extends through an extension chamber of a rotatory
actuator into a retraction chamber of the same rotary actuator. The
piston rod connects to a piston, which traverses through the torus
cylinder, on both the retraction chamber side of the piston and the
extension chamber side of the piston. The piston rod has a torus
shape that centers inside the torus cylinder, and connects to both
sides of a piston face in the retraction and extension chambers of
the torus cylinder. The ends of the piston rod are connected
together by a linkage mechanism.
[0178] In some embodiments, the cylinders, which may be aluminum,
may be anodized. The anodized surface may be Teflon impregnated to
decrease friction of piston seals and rod seals. Electrodes may be
placed in both an end cap and piston for displacement measurements.
The electrodes may only cover a portion of the piston and endcap in
a crescent shape.
[0179] In some embodiments, an alignment tongue and groove on a
torus cylinder and endcap maintain alignment of the endcap in
relation to the torus cylinder during assembly. A radius of
curvature of a through hole of the end cap matches a radius of the
torus-shaped piston rod, which maintains alignment by the tongue
and groove of the endcap and cylinder assembly.
[0180] In some embodiments, a plastic rotating torus actuator
wherein an external molded housing permanently affixes an endcap to
a cylinder. A static seal may be placed between the cylinder and
endcap to prevent leaking.
[0181] In some embodiments, disclosed is a rotating fluid actuated
joint. The joint is sealed from external leakage. A sealing
mechanism affixes a stationary seal on one joint housing half and a
second joint half rotates inside the stationary seal. A rubber lip
seal allows rotation of a second joint housing inside a stationary
seal of a first half joint housing. A fluid port on a robotic joint
returns leaked fluid to a fluid reservoir.
[0182] In some embodiments, disclosed is a robotic finger with a
robotic skin for containment of leaked fluids with fluid ports to
return leaked fluid to a fluid reservoir.
[0183] In some embodiments, disclosed is a robotic joint including
a plurality of joint halves. Each joint half is sealed to prevent
leaking fluids from exiting the joint half. A drive pin of each
actuator of each joint half is sealed to prevent leakage from the
joint half. A fluid hose captures leaked fluid and returns the
leaked fluid to a fluid reservoir.
[0184] In some embodiments, disclosed is a hydraulic circuit
configured to enable manually teaching a robotic arm or finger. The
hydraulic circuit equalizes a pressure between an extension chamber
and a retraction chamber of the robotic arm or finger. A hydraulic
pressure from a hydraulic pump may regulate the pressure such that
a force of gravity and friction can be cancelled. The hydraulic
pressure from the pump is set to equal the force of gravity. A
force from manual manipulation by a human is measured such that a
force of hydraulic actuation is used to assist the human through
actively controlling the pressure to cancel all forces except the
force from human manipulation. A force/torque sensor is used to
measure the force from human manipulation. A flow regulator is set
to limit maximum velocity of the manual manipulation by an
operator. The velocity is determined from encoder readings.
Regulating a flow control valve provides additional pressure
control.
[0185] In some embodiments, disclosed is a robotic hand. A
hydraulic force applied to an object by the robotic hand is
controlled by controlling a pressure of actuators of the robotic
hand. The pressure is controlled by a pressure reducing valve.
[0186] In some embodiments, disclosed is a rotating joint actuated
by a fluid media. Actuators of the rotating joint are connected
fluidically in series such that the degrees of rotation from one
actuator are added to degrees of rotation of subsequent
actuators.
[0187] In some embodiments, disclosed is a rotating joint actuated
by a fluid media. Actuators of the rotating joint are connected
fluidically in parallel such that the torque from one actuator is
added to the torque of subsequent actuators.
[0188] In some embodiments, disclosed is a torus-shaped piston rod
that extends from a retraction chamber of a torus cylinder into an
extension chamber of the torus shaped cylinder.
[0189] It will be apparent to those having skill in the art that
many changes may be made to the details of the above-described
embodiments without departing from the underlying principles of the
invention. The scope of the present invention should, therefore, be
determined only by the following claims.
* * * * *