U.S. patent application number 16/035182 was filed with the patent office on 2018-11-08 for arm using a two-joint module.
The applicant listed for this patent is ENGINEERING SERVICES INC.. Invention is credited to Andrew A. GOLDENBERG, Xiaojia He, Ziren LU.
Application Number | 20180319012 16/035182 |
Document ID | / |
Family ID | 61513353 |
Filed Date | 2018-11-08 |
United States Patent
Application |
20180319012 |
Kind Code |
A1 |
He; Xiaojia ; et
al. |
November 8, 2018 |
ARM USING A TWO-JOINT MODULE
Abstract
A robotic arm includes at least two two-joint modules and at
least a first link. Each two-joint module includes a housing, a
pair of hollow rotary actuator assemblies and a pair of motor
drives. Each actuator assembly has an axis and a hollow shaft and
the axes are arranged at an angle to each other. The pair of hollow
rotary actuator assemblies are arranged such that a back end of the
actuator assemblies is inside the housing and a front end of the
actuator assemblies extends outwardly of the housing, and attached
to the housing such that cables can be fed from the outside of one
of the actuator assemblies to the inside thereof and to the inside
of the other actuator assemblies to the outside thereof. The pair
of motor drives are operably attached to the actuator assemblies
and the motor drives are outside the housing.
Inventors: |
He; Xiaojia; (Toronto,
CA) ; LU; Ziren; (Thornhill, CA) ; GOLDENBERG;
Andrew A.; (Toronto, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ENGINEERING SERVICES INC. |
Markham |
|
CA |
|
|
Family ID: |
61513353 |
Appl. No.: |
16/035182 |
Filed: |
July 13, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15499604 |
Apr 27, 2017 |
10022861 |
|
|
16035182 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B25J 19/0075 20130101;
B25J 9/126 20130101; B25J 19/0029 20130101 |
International
Class: |
B25J 9/12 20060101
B25J009/12; B25J 18/04 20060101 B25J018/04 |
Claims
1. A robotic arm comprising: at least two two-joint modules wherein
each two-joint module includes: a housing; a pair of hollow rotary
actuator assemblies each having an axis and a hollow shaft and the
axes being arranged at an angle to each other and the pair of
hollow rotary actuator assemblies being arranged such that a back
end of each of the hollow rotary actuator assemblies is inside the
housing and a front end of each of the hollow rotary actuator
assemblies extends outwardly of the housing, and attached to the
housing body such that the cables can be fed from the outside of
one of the pair of hollow rotary actuator assemblies to the inside
thereof and to the inside of the other of the pair of hollow rotary
actuator assemblies to the outside thereof; and a pair of motor
drives operably attached to the pair of hollow rotary actuator
assemblies and the motor drives being outside the housing; and at
least a first link.
2. The robotic arm of claim 1 further including a third two-joint
module and a second link, and the two-joint modules are a shoulder
module, an elbow module and a wrist module and shoulder module and
the elbow module are operably attached to opposing ends of the
first link and the elbow module and the wrist module are attached
to opposing ends of the second link.
3. The robotic arm of claim 1 wherein each the axes of the pair of
hollow rotary actuator assemblies are arranged orthogonally.
4. The robotic arm of claim 3 wherein each hollow rotary actuator
assembly is a combo actuator.
5. The robotic arm of claim 4 wherein each hollow rotary actuator
assembly includes a brushless DC servo motor having a hollow
central portion, an encoder having a hollow central portion, a
brake having a hollow central portion and an encoder having a
hollow central portion.
6. The robotic arm of claim 1 wherein housing of each two-joint
module includes a housing body and a housing cover releasably
attachable to the housing body.
7. The robotic arm of claim 6 wherein each housing body includes a
pair of generally cylindrical compartments for housing the pair of
hollow rotary actuator assemblies.
8. The robotic arm of claim 7 wherein each housing body further
includes center compartment between the two generally cylindrical
compartments.
9. The robotic arm of claim 1 wherein the axes of the pair of
hollow rotary actuator assemblies are arranged at an obtuse angle
therebetween.
10. The robotic arm of claim 1 wherein the power, speed and torque
of the pair of the hollow rotary actuator assemblies is the
same.
11. The robotic arm of claim 1 wherein the power, speed and torque
of the pair of the hollow rotary actuator assemblies is
different.
12. The robotic arm of claim 1 wherein the first link is a shoulder
link.
13. The robotic arm of claim 12 wherein the shoulder link includes
a body and a hollow cover and having a first port and a second
port.
14. The robotic arm of claim 13 wherein the first port and the
second port of the shoulder link are generally in the same
plane.
15. The robotic arm of claim 14 wherein the at least two two-joint
modules are three two-joint modules being a shoulder module, an
elbow module and a wrist module and further including a second link
being a wrist link and wherein the shoulder module is attached at
one end of the shoulder link and the elbow module is attached at
the other end thereof and the elbow module is attached a one end of
the wrist link and the wrist module is attached at the other end
thereof.
16. The robotic arm of claim 15 where in the wrist link has a first
and second port that are generally orthogonal to each other.
17. The robotic arm of claim 1 further a motor drive operably
attached to each of the hollow rotary actuator assemblies and the
motor drives being outside the housing.
Description
FIELD OF THE DISCLOSURE
[0001] This disclosure relates to robotic arms and in particular an
arm using a two joint module having two degrees of freedom and
having a generally L-shape.
BACKGROUND
[0002] Two degree-of-freedom (2-DOF) joint modules used in robotic
arms are becoming more common due to several advantages such as:
compact size, light weight and lower cost. Joint modules are
designed to meet certain requirements and constraints and these are
transformed into the design specifications. For industrial
applications, the requirements of payload range, speed, accuracy,
reliability, lifetime, safety, ease of assembly and maintenance are
very important.
[0003] There is a type of 2-DOF joint module, called Powerball
ERB.TM. designed by Schunk GmbH & Co. KG. This joint module is
housed in a ball shape enclosure that contains all the components
needed to control the joint: servo motor, encoder, motor drive,
harmonic drive, holding brake and hollow shaft for internal
cabling. The joint module is not sealed as ventilation is needed to
dissipate heat generated by the electronic components such as
motor, motor drive and brake. The module is light weight, compact
and is highly integrated. However, this design has limitations.
[0004] First, the Powerball ERB.TM. joint module consists of many
mechanical and electronic components and this increases the
complexity of the structure while also creates a heat dissipation
problem. Since all electrical and control components are integrated
in the module housing, the heat generated by these components
requires a relatively large space to dissipate. However, since this
joint is designed to be a compact joint, the power consumed by the
electronic components is constrained by the heat that is generated.
This in turn limits the output power of the joint module. Hence,
the application of this type of joint module in terms of payload
range is limited.
[0005] Second, to solve the issue of heat dissipation, openings or
slots are made on the housing. This limits the applications of the
joint module under certain harsh industrial environments such as
dusty, humid, and explosive environments. These joints could not be
used in robot arms for painting, coating and welding. For example;
the explosive gases and sparks that may be present in such
industrial applications could get into the joint module and cause
explosions.
[0006] Third, the Powerball ERB.TM. can be used to build a robotic
arm, LWA-4P.TM.. The LWA-4P arm comprises three Powerball joint
modules and two links. Since the joint modules have limitations on
heat dissipation and power capped issues, the arm cannot work under
some harsh industrial environments and the payload of the arm is
limited.
[0007] There is another 2-DOF joint module, designed by Engineering
Services Inc. (ESI) with patent number U.S. Pat. No. 9,044,865.
This joint module is designed for large torque and low speed
applications. The joint module includes a module housing and two
joints. Also, one of joints has a hollow shaft gearhead, an
off-axis drive, a servo motor, and internal cables extending
through the hollow shaft gearhead. Since the joint module is
designed to connect with a link, it has an active side and a
passive side with electronic connectors. The active side is
mechanically connected to the link and the electronic connectors of
the passive side are operably connected to the link cables. The
joint is used to build a robotic arm. There are limitations with
this design as discussed below.
[0008] First, since all the components needed to control the motion
of the joint are integrated into the module, it has the same heat
dissipation problem mentioned in the Powerball EBR.TM..
[0009] Second, the cable routing inside the module is complicated
because of the internal structure of the joint module. One of
joints uses a non-hollow shafted motor and gearhead for providing
the torque. Because of the internal structure of the joint, the
cables go into one end of the module and inside the module turn 90
degrees and go out the other side of the module. In this case, the
cables will be squeezed inside the housing. This may cause large
torsional forces on the cables.
[0010] There is another type of 2-DOF joint module, designed by
Fanuc Robotics North America as shown in a patent U.S. Pat. No.
5,293,107. Each module housing accommodates two hollow shafted
rotary actuators, other electronic components and internal cables.
The joint is used to build a robotic arm. However, this design also
has limitations.
[0011] First, the installation process of rotary actuators and
electronic components is complicated because it requires too many
assembly steps. The two actuator sets are installed inside the
housing, with their output shaft facing outside and the motor
facing inside of the housing. The two actuators will be fixed to
the housing wall by bolts and screws. To mount the two actuators in
the housing, the two actuators cannot be put in from outside to
inside of the housing. Instead, the actuators must be installed
from the inside. So, the entire housing must be dissembled. Once
the actuators are installed the housing is reassembled as one piece
with screws and bolts. Therefore, the installation process is
complicated.
[0012] Second, the joint module housing of Fanuc is not made of one
piece. The housing box is made of several pieces and these pieces
are fixed by screws and bolts to form the housing. So, the
structure of the housing is not as strong as the one-piece
housing.
[0013] Third, the maintenance process of the joint module is
complicated. To access the actuators and other electronic
components, a user needs to dissemble the housing case, conduct the
maintenance, and resemble the housing once the maintenance is
finished.
[0014] All of the aforementioned approaches to modular joints have
limitations for industrial applications. It would be advantageous
to design a new type of 2-DOF joint module which will have features
such as compact, low heat generation, sealed and rigid housing,
large payloads, ease of installation and maintenance process and
assembly.
SUMMARY
[0015] The present disclosure relates to a two joint module. The
two joint module includes a housing and a pair of hollow rotary
actuator assemblies. Each actuator assembly has an axis and a
hollow shaft and the axes are arranged at an angle to each other.
The pair of hollow rotary actuator assemblies are arranged back to
back and attached to the housing such that cables can be fed from
the outside of one of the pair of hollow rotary actuator assemblies
to the inside thereof and to the inside of the other of the pair of
hollow rotary actuator assemblies to the outside thereof.
[0016] The axes of the pair of hollow rotary actuator assemblies
may be arranged orthogonally.
[0017] Each hollow rotary actuator assembly may include a brushless
DC servo motor having a hollow central portion, an encoder having a
hollow central portion, a brake having a hollow central portion and
an encoder having a hollow central portion. Each hollow rotary
actuator assembly may be a combo actuator.
[0018] The housing may include a housing body and a housing cover
releasably attachable to the housing body. The housing body may
include a pair of generally cylindrical compartments for housing
the pair of hollow rotary actuator assemblies. The housing body may
further include a center compartment between the two generally
cylindrical compartments.
[0019] The axes of the pair of hollow rotary actuator assemblies
may be arranged at an obtuse angle therebetween.
[0020] The power, speed and torque of the pair of the hollow rotary
actuator assemblies may be the same. Alternatively, the power,
speed and torque of the pair of the hollow rotary actuator
assemblies may be different.
[0021] The two joint module may include a pair of motor drives
operably attached to the pair of hollow rotary actuator assemblies
and the motor drives are outside the housing.
[0022] The disclosure also relates to a robotic arm. The robotic
includes at least two two joint modules wherein each two joint
module is as described above and at least a first link.
[0023] The robotic arm may include a third two joint module and a
second link, wherein the two joint modules are a shoulder module,
an elbow module and a wrist module. The shoulder module and the
elbow module are operably attached to opposing ends of the first
link and the elbow module and the wrist module are attached to
opposing ends of the second link.
[0024] The first link may be a shoulder link. The shoulder link may
include a body and a hollow cover and having a first port and a
second port. The first port and the second port of the shoulder
link are generally in the same plane.
[0025] The second link may be a wrist link. The wrist link may have
a first and second port that are generally orthogonal to each
other.
[0026] The robotic arm may include a motor drive operably attached
to each of the hollow rotary actuator assemblies and the motor
drives being outside the housing.
[0027] Further features will be described or will become apparent
in the course of the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The embodiments will now be described by way of example
only, with reference to the accompanying drawings, in which:
[0029] FIG. 1 is a perspective view of a two degree of freedom two
joint module which is generally L-shaped;
[0030] FIG. 2 is a cross sectional view of the housing for the two
degree of freedom L-shaped two joint module of FIG. 1;
[0031] FIG. 3 is a front view of the two degree of freedom L-shaped
two joint module housing of FIG. 2;
[0032] FIG. 4 is a perspective view of an embodiment of a hollow
rotary actuator assembly having a central axial hole therethrough
and for use with the two degree of freedom L-shaped two joint
module of FIG. 1;
[0033] FIG. 5 is a side view of the hollow rotary actuator assembly
of FIG. 4;
[0034] FIG. 6 is a sectional view of the hollow rotary actuator
assembly of FIGS. 4 and 5;
[0035] FIG. 7 is a front view of the two degree of freedom L-shaped
two joint module of FIG. 1;
[0036] FIG. 8 is a side view of the two degree of freedom L-shaped
two joint module of FIGS. 1 and 7;
[0037] FIG. 9 is a top view of the two degree of freedom L-shaped
two joint module of FIGS. 1, 7 and 8;
[0038] FIG. 10 is an exploded perspective view of the two degree of
freedom L-shaped two joint module of FIGS. 1, 7, 8 and 9;
[0039] FIG. 11 is a cross sectional view of the two degree of
freedom L-shaped two joint module of FIGS. 1, and 7 to 10 and
showing the cable routing;
[0040] FIG. 12 is an exploded perspective view of an embodiment of
an arm using the two degree of freedom L-shaped two joint module of
FIGS. 1 and 7 to 11;
[0041] and
[0042] FIG. 13 is a side view of the arm of FIG. 17 shown in a
different orientation;
[0043] FIG. 14 is an exploded view of the shoulder link shown in
the arm of FIGS. 12 and 13 as viewed from one side thereof;
[0044] FIG. 15 is an exploded view of the shoulder link of FIG. 14
but viewed from the other side thereof;
[0045] FIG. 16 is an exploded side view of the elbow link shown in
the arm of FIGS. 12 and 13 as viewed from one side thereof;
[0046] FIG. 17 is a perspective view of the elbow link of FIG.
16;
[0047] FIG. 18 is a cross section view of the elbow link shown in
FIGS. 16 and 17;
[0048] FIG. 19 is a perspective view of an alternate embodiment of
the L-shaped two joint module shown in FIGS. 1 and 7 to 11 but with
different sized hollow rotary actuator assemblies;
[0049] FIG. 20 is a side view of the L-shaped two joint module of
FIG. 18;
[0050] FIG. 21 is a perspective view of a further alternate
embodiment of the L-shaped two joint module shown in FIGS. 1 and 7
to 11 and 18 and 19 but with different sized hollow rotary actuator
assemblies, different from those shown in FIGS. 18 and 19;
[0051] FIG. 22 is a side view of the L-shaped joint module of FIG.
21;
[0052] FIG. 23 is a perspective view of a further alternate
embodiment of a two joint module similar to those shown in FIGS. 1
and 7 to 11 and 19 to 22 but with an obtuse angle between the two
hollow rotary actuator assemblies;
[0053] FIG. 24 is a side view of an alternate embodiment of an arm
similar to that shown in FIG. 18 but having different sized links;
and
[0054] FIG. 25 is a top view of an arm using the L-shaped joints of
FIGS. 1 and 7 to 11 and 19 to 22 but showing the offset.
DETAILED DESCRIPTION
[0055] Referring to FIG. 1, a two degree of freedom two-joint
module which is generally L-shaped is shown generally at 10.
L-shaped two joint module 10 includes a housing 12, a pair of
hollow rotary actuator assemblies 14 arranged orthogonally in the
housing 12.
[0056] As best seen in FIGS. 2 and 3 the housing 12 is composed of
two parts: a housing body 16 and a housing corner cover 18 that is
releasably attachable to the housing body. The housing body 16
contains three compartments: two generally cylindrical compartments
20 and 22 for accommodating the pair of hollow rotary actuator
assemblies 14 which may be turret and shoulder actuators; a center
compartment 24 is located in between compartments 20 and 22 and is
for accommodating the electronics components. Compartments 20 and
22 each have a center axis 26 and 28 respectively. Center axes 26
and 28 are orthogonal to each other. The corner cover 18 is
detachable from the housing body 16. The housing body 16 includes a
flange 36
[0057] FIG. 3 shows the front view of the L-shaped two joint module
joint module housing 12. The housing body 16 allows two hollow
rotary actuator assemblies 14 to have orthogonal axes by means of
compartments 20 and 22. A plurality of holes or apertures 26 are
formed in the housing body 16 around the opening to the
compartments 20 and 22 to allow the hollow rotary actuator
assemblies to be mounted therein with screws. Cavity or compartment
20 has a hole 30 on the inside thereof for electronics connection
to the hollow rotary actuator assembly 14 (not shown). Similarly
cavity or compartment 22 has a hole 32 on the inside thereof for
electronics connection to the hollow rotary actuator assembly 14
(not shown). An example of a hollow rotary actuator assembly for
use in the L-shaped two joint module 10 is shown in FIGS. 4 to 6.
Hollow rotary actuator assembly 14 has a hollow shaft along its
central axis. Hollow rotary actuator assembly 14 includes a
brushless DC servo motor 40, an encoder 42, a brake 44 and a gear
head 46. The hollow rotary actuator assembly 14 has an output shaft
48 for attaching it to the housing 12. Each of the elements of the
hollow rotary actuator assembly 14 is generally donut shaped such
that the hollow rotary actuator assembly has a hollow central
shaft. More specifically the servo motor 40 has a hollow central
portion. The encoder 42 is an absolute encoder and has a hollow
central portion. The brake 44 has a hollow central portion. The
gear head 46 has a hollow central portion. Preferably the hollow
rotary actuator assembly 14 is a combo actuator and each element is
connected together to form a single combo actuator. Each element is
operably connected to cables 47. The combo actuator or hollow
rotary actuator assembly 14 has the advantages of compact size, and
the hollow shaft feature allows cables to be passed therethrough.
The cross-roll bearing 43 is embedded in the flange 45 as best
shown in FIG. 6. The cross-roll bearing 43 is used on the mounting
flange 45 to simplify the assembly of the combo actuator 14, and
reduces its weight and size.
[0058] Referring to FIGS. 1, and 7 to 11, a two-joint L-shaped
module is shown generally at 10. Module 10 includes two hollow
rotary actuator assemblies 14 and a joint housing 12 having a
housing body 16 and a housing corner cover 18. The joint housing 12
is shown in FIGS. 2 and 3. The combo actuator 14 has a hollow shaft
50. The axes of the hollow shafts of the two combo actuators 14 are
collinear with the center axes 26 and 28 of compartments 20 and 22
of the housing 12, shown in FIG. 2. A plurality of screw holes 52
are formed in the output shaft 48 of the combo actuator 14. The
screws holes 54 are formed in the flange plate. The cross-roll
bearings 43 form part of the flange plate 45 and the screw holes 54
only go through the flange plate 45. The cross-roller bearing 43
provides support to the output shaft 48 in bending. The output
shaft 48 provides the output torque.
[0059] Holes 52 are used for connecting the joint module 10 to a
robot arm link 102 as described below in relation to FIGS. 12 and
13. A plurality of screws 54 are used to mount the combo actuator
14 to the housing 12. Circular flange 36 may function as a part of
a robotic arm mechanical hard stop described in more detail below.
A plurality of screws holes 56 are the screw holes for fixing the
cover 18 to the joint housing body 16. The combo actuator 14 has an
output side defined by the output shaft 48 and an inside 49.
[0060] FIG. 10 presents the exploded view of a 2 DOF L-shaped two
joint module 10. Module 10 includes two rotary actuators,
preferably combo actuators 14, a module housing 12 including a
housing body 16 and a housing cover 18. The axes 26 and 28 of the
compartments 20 and 22 are co-linear with the axes of the two combo
actuators 14. The axes 26 and 28 are orthogonal to each other. The
two combo actuators 14 are made of a combo actuator which is shown
in FIGS. 4 to 6. The two combo actuators 14 are installed to the
housing 12 by being inserted from outside to inside of the housing
compartments 20 and 22 (as best seen in FIG. 10). Then, the combo
actuators 14 are fixed to the housing 12 with the screws 54. A
washer 62 is positioned between of the screw 54 and actuator 14.
Internal cable holders may be used to stabilize the cables 66
(shown in FIG. 11). Cable bundles 66 are passed through the housing
12 from one end to the other. More specifically the cables go from
the outside side defined by the output shaft 48 of one combo
actuator 14 to the inside thereof 49 through the central
compartment 24 to the inside 49 of the other combo actuator 14 to
the outside thereof defined by the output shaft 48. The cable
bundles 66 may be held in place with cable holders attached to the
inside of the module housing body 16. An electronic component 72
may be mounted on the inside of the cover 18. If present the
electronic component 72 is used to distribute signals such as the
voltage divider. Alternatively this may be done wirelessly. The
cables 47 of the combo actuator 14 are operably connected to cable
66. Similarly the electronic component 72 is operably connected to
the cable 66. FIG. 11 shows cable routing through the joint module
10. The cable routing process is simplified with the structure
design of the joint module. A bundle of cables 66 is designed to
pass the joint module 10 from one end to another end. The sequence
is as follow: The cable bundle 66 passes through a combo actuator
14, located in housing compartment 22, through the combo actuator's
hollow shaft 50 from one end to another. Then, the cable bundle
reaches the compartment 24. After that, the cable bundle 66 passes
through the other combo actuator 14, located in housing compartment
20, through the combo actuator's hollow shaft 50 from one end to
another.
[0061] In addition, as shown in FIG. 11, the maintenance process of
the joint module 10 is very easy. For cable connection and
electrical parts maintenance, users can simply open the housing
cover 18 to access the electronic components placed in the housing
compartment 24. For mechanical parts maintenance, users can take
the combo actuators 14 out from housing compartment 20 and 22.
[0062] As shown in FIGS. 12 and 13, a robotic arm 100 uses a
plurality of the 2 DOF joint modules 10. The joint modules 10 may
be used as a turret-shoulder 104, elbow 106, and wrist 108 modules
respectively. These modules can be used with two links 102 and 110
respectively to form a six degree of freedom robotic arm 100. The
turret shoulder module 104 of the arm 100 is attached to a seat
112. An electronic box 114 is attached to the seat 112. The
electronic box 114 or control cabinet includes a plurality of
drives 124 (shown in FIG. 13) one for each of the hollow rotary
actuator assemblies 14. Each hollow rotary actuator assembly 14 is
operably attached to a motor drive 124. The turret-shoulder module
104 is attached to shoulder link 102 at one end thereof. One side
of the elbow module 106 is attached to the other end of shoulder
link 102. The other side of the elbow-wrist module 106 is attached
to one side of an elbow link 110. The other side of the elbow link
110 is attached to wrist module 108.
[0063] An internal cable bundle 66 goes in to the arm 100 and is
electronically connected to the electronic box 114. The cable
bundle 116 passes through the following components: the turret seat
112, the turret-shoulder module 104, the shoulder link 102, the
elbow-wrist module 106, the elbow link 110 and the wrist module 108
as shown in FIG. 12.
[0064] Referring to FIGS. 14 and 15 the shoulder link 102 includes
a link base 126 and a link cover 128 attached together with a
plurality of screws 130. The shoulder link 102 provides a first
port 132 and a second port 134 at opposed ends thereof which are
attachable to the joints. The first port 132 and the second port
134 are generally in the same plane. The link base 126 is basically
a plate and the link cover 128 is basically hollow cover. It will
be appreciated by those skilled in the art that the design shown
herein is both easy to use and easy to scale. It would be
relatively inexpensive to change the length of the shoulder link
102. As can be seen the drawings the cable bundles 66 can easily
pass through the shoulder link 102.
[0065] Referring to FIGS. 16-18, the elbow link 110 has a generally
tubular hollow body 136 and a cover 138. Elbow link 110 includes a
first port 140 and a second port 142. The first port 140 and second
port 142 are generally orthogonal. The elbow link 110 can easily be
elongated to increase the length of the link. As can be seen in the
drawings since the link is hollow the cable bundles 66 can easily
pass through the elbow link 110.
[0066] By using the combo actuators and placing motor drives 124
outside joint module, the 2-DOF joint module 10 is more compact and
light weight.
[0067] Also, since the motor drives 124 are outside joint module
10, the influence of heat from the motor in the motor drive is
external to the joint module and this allows the joint module to be
designed in compact manner. These features enable the new joint
modules to be used by robot arms working in industrial
environments. This design overcomes the aforementioned heat
dissipation problem in the prior art joints discussed above and
specifically the Powerball ERB.TM. and U.S. Pat. No.
9,044,865B2.
[0068] It will be appreciated by those skilled in the art that to
achieve larger power, torque and higher speed of the joints, the
size of the joint module increases proportionally for the different
purposes, such as accommodation of bigger components and heat
dissipation. However, once the heat generation inside the joint
module housing is reduced, within the original module space, each
joint can be designed to achieve larger power, torque and higher
speed. As shown in Table 1, each joint of L-shaped 2 DOF joint
module 10 described herein is designed with larger motor power,
torque and higher speed in comparison to SCHUNK's POWERBALL.TM.
joint.
[0069] In addition the joint modules 10 may be sized for the
particular purpose. As shown herein the turret-shoulder 104, elbow
106, and wrist 108 modules are sized for their particular purpose.
For example the wrist module 108 has a smaller payload so the wrist
module may be smaller. As well, the power, speed and torque of the
hollow rotary actuator assemblies may be chosen for the specific
purpose. The power, speed and torque characteristics may be
different in one of the two degree of freedom joint module 10. As
shown in Table 1 in the turret-shoulder module 104 the power, speed
and torque of the hollow rotary actuator assemblies 14 for the
turret joint and the shoulder joint are the same. In contrast in
the elbow module 106 the power, speed and torque of the hollow
rotary actuator assemblies 14 are different. As can be seen in
FIGS. 19 and 20 the housing 12 of the elbow module 106 is the same
as that shown in FIGS. 1 to 11 but the characteristics of the
hollow rotary actuator assemblies 14 is different. In contrast in
the wrist module 108 shown in FIGS. 21 and 22 the different arms of
the L-shaped housing is different. Specifically one arm 150 is
smaller than the arm 152 and the characteristics of the hollow
rotary actuator assemblies 14 are different.
TABLE-US-00001 TABLE 1 Specification comparison between joint
module 10 and SCHUNK's joints Motor Power (W) Speed (deg/s) Torque
(Nm) Joint 104 SCHUNK 104 SCHUNK 104 SCHUNK Turret 480 72 70 72 382
35 Joint Shoulder 480 72 70 72 382 35 Joint Joint 106 SCHUNK 106
SCHUNK 106 SCHUNK Elbow Pitch 308 72 180 72 178 35 Joint Elbow Roll
207 72 180 72 81 35 Joint Joint 108 SCHUNK 108 SCHUNK 108 SCHUNK
Wrist pitch 109 72 180 90 43 7 Joint Wrist twist 109 72 180 90 35 7
Joint
[0070] The two degree of freedom joint module 10 may be varied by
changing the angle between the two hollow rotary actuator
assemblies 14 as shown in FIG. 23. The module 160 shown herein is
similar to modules 10, 104, 106 and 108 but the angle between the
assemblies 14 arms 162 and 164 is an obtuse angle. It will be
appreciated by those skilled in the art that the angle shown herein
is by way of example only and the user may choose whatever angle
fits their particular purpose. The angle may be chosen if the joint
is for use in a particularly awkward location where the convention
right angle is not the optimal solution.
[0071] As discussed above the lengths of the links may vary
depending on the needs of the user. An example of this is shown in
FIG. 24 which shows an alternate arm 170. This arm is similar to
that shown in FIG. 13 but with elongated shoulder link 172 and an
elongated elbow link 174. In the example shown herein the sizes of
the shoulder module 104, elbow module 106 and wrist module 108 are
the same as those shown in FIG. 13 however as will be appreciated
by those skilled in the art that the sizes of the joints may be
varied depending on the needs of the user and the anticipated
payload.
[0072] In the configuration shown in FIG. 25, the axis 118 of the
roll joint elbow module 106 is not aligned along the axis 120 of
the twist joint of the wrist module 108. Axis 118 is offset 122
from axis 120 by a defined amount. This offset structure has not
been seen in prior art robot arms even when these prior art robotic
arms use a use a 2-DOF joint modules in their design.
[0073] The structure of the new joint module is of "L-Shape", which
is not seen in the prior art. The "L-Shape" two joint module 10,
consisting of two cylindrical tubes with their central axes
orthogonal to each other is manufactured in one piece so its
mechanical structure is very sturdy. As discussed the size of the
cylindrical tubes may be the same or vary depending on the combo
actuators 14 sized to be used therein.
[0074] Due to the "L-Shape" structure of the module housing, the
installation method of joints for each module is simpler than that
of the prior art. The installation method is shown in FIG. 10. The
two combo actuators 14 are inserted into the tubes of the "L-Shape"
housing body 16 from outside to inside direction, with actuators'
head/(shaft end or output shaft 48) facing outside and tail/(brake
end 44) facing inside. The rotational axes of the two actuators are
aligned with the tubes' axis 26, 28, which are orthogonal to each
other and the tails of actuators are back-to-back to each other.
Once the two actuators 14 are inserted into the tubes of the
housing body 16, they are fixed to the housing with screws.
[0075] There are at least two advantages of this installation
method. First, when installing the combo actuators 14 to the
housing 12, the entire housing is not taken apart and the module
remains in one piece. The firmness and stability of the structure,
therefore, will remain. This feature overcomes the shortcoming of
Fanuc design described above, whose actuators are installed from
inside to outside and the entire joint is has to be taken apart for
installation or maintenance. Second, since the two actuators 14 are
back-to-back, the hollow shaft structure allows for simple cable
routing and cable management. As shown in FIG. 11, cables go in
from the head end of the first joint or combo actuator 14, and pass
through the actuator 14 from the back end and then turn 90 degrees
towards the second joint or combo actuator 14. Then, the cables go
in from the back end of the second actuator 14, and go all the way
out from the head end of the actuator 14.
[0076] Due to the structure of the module housing 12 and the simple
installation method of joint module 10, the maintenance process of
the joint and arm is relatively easy. As shown in FIG. 11, in the
"L-Shape" housing, the two actuators are back-to-back to each
other, so the electronic components of two actuators are all
gathered and placed in the center corner compartment of the
housing. Users can easily access the electronic components in the
center compartment by taking the cover piece away without taking
the entire joint module apart. Therefore, this design reduces the
complexity of maintenance. As shown in FIG. 12, the 2 DOF joint
modules 104, 106 and 108 can be used in a robotic arm 100. The
joint modules 104, 106 and 108 represent the turret-shoulder,
elbow-wrist, and wrist-pitch and wrist-roll modules respectively.
The shoulder module 104 and the elbow module 106 are attached to
opposing ends of the first or shoulder link 102 and the elbow
module 106 and the wrist module 108 are attached to opposing ends
of the second or elbow link 110. This design of the robotic arm has
advantages.
[0077] Robotic arm 100 has a different structure from the robot
arms the prior art robotic arms that use single joint modules or 2
DOF joint modules. Robotic arm 100 is configured such that the
rotation axis of elbow-roll of the elbow joint 104 is not aligned
or is offset with the rotation axis of wrist-twist of the wrist
joint 108 as shown in FIG. 12. This configuration solves the
singularity issue for wrist joint module, and thus expands the arm
working space.
[0078] In addition the manufacturing and assembly processes of
robotic arm 100 are greatly simplified. The arm uses same type of
joint modules, the assembly between joint modules and links can be
done in few steps. The number of components is lower than other
robot arms using modular joints.
[0079] Generally speaking, the systems described herein are
directed to 2-DOF joint modules and robotic arms that use same.
Various embodiments and aspects of the disclosure will be described
with reference to details discussed below. The following
description and drawings are illustrative of the disclosure and are
not to be construed as limiting the disclosure. Numerous specific
details are described to provide a thorough understanding of
various embodiments of the present disclosure. However, in certain
instances, well-known or conventional details are not described in
order to provide a concise discussion of embodiments of the present
disclosure.
[0080] As used herein, the terms, "comprises" and "comprising" are
to be construed as being inclusive and open ended, and not
exclusive. Specifically, when used in the specification and claims,
the terms, "comprises" and "comprising" and variations thereof mean
the specified features, steps or components are included. These
terms are not to be interpreted to exclude the presence of other
features, steps or components.
[0081] As used herein the "operably connected" or "operably
attached" means that the two elements are connected or attached
either directly or indirectly. Accordingly the items need not be
directly connected or attached but may have other items connected
or attached therebetween.
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