US 2020/0086501 Al

Mar. 19, 2020 Sheet 19 of 33

Patent Application Publication

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US 2020/0086501 Al

constrained in the X direction and the Y direction. An
internal dimension of aligner 258 can be the same as internal
dimension of aligner 258.2. In an embodiment, aligner 258
is an element on substratum 202; aligner 258.2 is an element
of body cap 248; are of the same polymer as substratum 202;
are cylindrical with an internal diameter, with an external
diameter, and with a thickness to mechanically contact and
constrain body 246.

[0069] Position verification sensor 200 can be made in
various ways. In an embodiment in FIG. 9, a process for
making position verification sensor 200 includes: providing
substratum 202, wherein substratum 202 and aligner 258 can
be made by additive manufacturing using a polymer; dis-
posing receiver pad 238 on substratum 202; disposing body
246 on substratum 202 and aligner 258; disposing spacers
256 on substratum 202 and fastening spacers 256 to sub-
stratum 202 using fasteners 254; disposing compliant mem-
ber 204 inside body 246 such that compliant member 204 is
in mechanical communication with substratum 202; dispos-
ing switch housing 252, receiver pad 238, and electrical
contacts 240.1 and 240.2 in housing 204 where switch
housing 252 is mechanically fastened to housing 204; dis-
posing housing 204 on compliant member 214 whereby
housing 204 is in mechanical communication with compli-
ant member 214; keyway aperture 208 can be formed in
aperture cap 206 by a subtractive machining process; dis-
posing aperture cap 206 on housing 204 using fasteners 254
to mechanically bind aperture cap 206 to housing 204; body
cap 248 and aligner 258.2 are made by additive manufac-
turing using a polymer; disposing body cap 248 on top of
housing 204; mechanically binding body cap 248 to spacers
256 using fasteners 254. The process for making position
verification sensor 200 can include disposing pad support
232 on substratum 202; and disposing receiver pad 238 on
pad support 232. Electrical contacts 240 can be attached to
aperture cap 206 or receiver pad 238. Electrical conductor
242 can be attached to aperture cap 206 or receiver pad 238.
‘A spring constant of compliant member 214 or pad support
232 can be adjusted

[0070] The process for making position verification sensor
200 with a plurality of receiver pads 238, with reference to
FIG. 32, can include additively manufacturing substratum
202 and aligner 258 as a single element; wherein spacers 256
are in mechanical communication with substratum 202; four
spacers 256 are mechanically fastened to substratum 202
using four fasteners 254; body 246 is disposed on substra-
tum 202 and in mechanical communication with aligner 258;
body 204B is disposed on bottom housing cap 204A;
compliant member 214.2 is disposed on bottom housing cap
204A; switch housing 252, receiver pad 238, and electrical
contact 240 are all of the same part; switch housing 252 is
mechanically fastened to housing 204.2 using fasteners
provided with switch housing 252; housing 204.2 is dis-
posed on compliant member 214.2 and housing 204.2 is in
mechanical communication with body 204B; compliant
member 214.3 is disposed on housing 204.2; an additional
switch housing 252, receiver pad 238, and electrical contact
240 are mechanically fastened to housing 204.1 using fas-
teners provided with switch housing 252; aperture cap 206
is in mechanically contact with housing 204.1; aperture cap
206 is mechanically fastened to housing 204.1 using fasten-
ers 254; housing base 260 is mechanically fastened to
housing 204.1 with fasteners; housing 204.1 with the above
elements fastened to it are disposed on compliant member

Mar. 19, 2020

214.3; top housing cap 204C is disposed on body 204B;
aperture cap 206 is mechanically fastened to top housing cap
204C using fasteners 254; compliant member 214.1 is
disposed on substratum 202 within body 246; body cap 248
and aligner 258 are disposed on body 246; and body cap 248
is fastened to spacers 256 using fasteners 254.

[0071] Position verification sensor 200 has numerous
advantageous and unexpected benefits and uses. In an
embodiment, a process for determining an accuracy of
mutual mechanical positioning of key 236 and position
verification sensor 200 includes: moving key 236 relative to
the position verification sensor 200; contacting position
verification sensor 200 with key 236 by key 236 contacting
cap surface 207 or receiver pad 238; producing null output
228 if key 236 does not contact receiver pad 238 by instead
contacting cap surface 207; and producing target output 230
ifkey 236 contacts receiver pad 238. From target output 230,
the accuracy can be determined by subtracting the numerical
dimensional value of the key 236 from the numerical
dimensional value of the keyway aperture 208. In an
embodiment, key 236 is a cylinder with a diameter of 0.250
inches; keyway aperture 208 is a circular hole with a
diameter of 0.251 inches; key 236 achieving target output
230 by passing through keyway aperture 208 to contact
receiver pad 238 yields accuracy of 0.001 inches which is
the difference between the diameter of the keyway aperture
208 and the diameter of key 236.

[0072] The process for determining accuracy can include
providing key 236 and position verification sensor 200 with
key 236; providing a plurality of keys 236 and a position
verification sensor 200; providing a key 236 and a plurality
of position verification sensors 200; and providing a plural-
ity of keys 236 and a plurality of position verification
sensors 200. A plurality of keys 236 can be mounted to the
same apparatus to interact with position verification sensor
200; and can be mounted to a plurality of apparatus to
interact with position verification sensor 200.

[0073] Position verification sensor 200 and processes dis-
closed herein have numerous beneficial uses, including
quickly, compared to vision or laser-based methods, ascer-
taining the accuracy and repeatability of a positioning ele-
ment (e.g., robot); being a cost-effective solution compared
to vision-based or laser-based methods or technologies that
are used to ascertain robot accuracy and repeatability; and
being minimally invasive in that the position verification
sensor 200 is can be relatively small in form factor. Advan-
tageously, position verification sensor 200 overcomes limi-
tations of technical deficiencies of conventional articles in
that vision-based and laser-based technologies that are used
to determine accuracy and repeatability require calibration
which can be time-consuming and require specific skills. A
benefit of position verification sensor 200 is that once
position verification sensor 2007 is mounted in a work
volume, location of receiver pad 238 to key 236 mounted on
an apparatus is taught and a program is created where the
apparatus moves key 236 to the receiver pad 238. This
program can be repeated whereby key 236 will either
achieve target state 226 with receiver pad 238, or key 236
will achieve null state 224 with cap surface 207.

[0074] Moreover, position verification sensor 200 and
processes herein have numerous advantageous properties. In
an aspect, position verification sensor 200 includes a plu-


US 2020/0086501 Al

sensor, can determine presence of the key when the key is
communicated through the keyway aperture. According to
an embodiment, the pad support does not depress, and, when.
the key contacts the receiver pad, a sensing circuit is closed
showing a positive result, i.e., the key contacts the receiver
pad. An additional depressive force can depress the compli-
ant member if present, and the target output is produced in
response.

[0046] According to an embodiment, with reference to
FIG. 5, position verification sensor 200 includes electrical
contact 240 disposed on the aperture cap 206 and in elec-
trical communication with the receiver pad 238. It is con-
templated that position verification sensor 200 can include a
plurality of electrical contact 240. In an embodiment, with
reference to FIG. 6, position verification sensor 200 includes
second electrical contact 240.2 disposed on the receiver pad
238 and in electrical communication with the electrical
contact 240.1. Electrical conductor 242 can be in electrical
communication with electrical contact 240 to provide an
electrical path for detection of a position (e.g., primary
position 218, depressed position 220) of aperture cap 206
relative to receiver pad 238 and substratum 202. Electrical
conductors (242.1, 242.2) communicate a signal, e.g., null
output 228 or target output 230, as a discrete output 210 that
corresponds to state (e.g. null state 224 or target state 226)
and position (e.g., primary position 218 or depressed posi-
tion 220) of aperture cap 206 and receiver pad 238 in
position verification sensor 200.

[0047] Position verification sensor 200 can include a
nested configuration of aperture caps 206, receiver pads 238,
housings 204, and compliant members 214. In an embodi-
ment, with reference to FIG. 7 and FIG. 16, position
verification sensor 200 includes second receiver pad 238.2
disposed on cap surface 207 of aperture cap 206, wherein
aperture cap 206 is interposed between second receiver pad
238.2 and first receiver pad 238.1. Second receiver pad
238.2 can include second keyway aperture 208.2 that com-
municates key 236 through second keyway aperture 208.2 to
aperture cap 206 when key 236 has a size and orientation
that are compatible with a size and orientation of second
keyway aperture 208.2. Second receiver pad 238.2 can
receive contact with key 236 when key 236 is communicated
through third keyway aperture 208.3 and when key 236 is
not aligned with second keyway aperture 208.2; can produce
second target output 230.2 in response to contact with key
236; and can produce second null output 228.2 in absence of
contact with key 236. Second aperture cap 206.2 can be
disposed over second receiver pad 238.2, wherein second
receiver pad 238.2 is interposed between second aperture
cap 206.2 and aperture cap 206. Second aperture cap 206.2
can be disposed on second housing 204.2. Second aperture
cap 206.2 can include second cap surface 207.2; and third
keyway aperture 208.3 disposed in second aperture cap
206.2 and bounded by second wall 209.2 of second aperture
cap 206.2. Third keyway aperture 208.3 includes a shape
and size selected to receive and selectively communicate
key 236 through third keyway aperture 208.3. In this con-
figuration, second aperture cap 206.2 selectively communi-
cates key 236 through third keyway aperture 208.3 to second
receiver pad 238.2 when key 236 and third keyway aperture
208.3 are compatibly aligned; and receives key 236 on
second cap surface 207.2 when key 236 and third keyway
aperture 208.3 are incompatibly aligned so that: key 236
contacts second cap surface 207.2 instead of being commu-

Mar. 19, 2020

nicated through third keyway aperture 208.3 and receives
depression force 212 from key 236. Second housing 204.2 is
disposed on substratum 202 and in which second receiver
pad 238.2 and receiver pad 238 are disposed; and on which
second aperture cap 206 is disposed. Second compliant
member 214.2 is interposed between substratum 202 and
second housing 204.2 and is through which substratum 202
and second housing 204.2 are in mechanical communica-
tion. Second compliant member 214.2 rests in second pri-
mary position 218.2 in an absence of key 236 disposed on
second cap surface 207.2 of second aperture cap 206;
receives depression force 212 from second aperture cap
206.2; reciprocatively depresses, from second primary posi-
tion 218.2 to second depressed position 220.2, in response to
receiving depression force 212 and being pushed by depres-
sion force 212 from key 236; and reciprocatively returns,
from second depressed position 220.2 to second primary
position 218.2, when key 236 is removed from contact with
second aperture cap 206.2.

[0048] With reference to FIG. 8, FIG. 9, and FIG. 10,
position verification sensor 200 can include various other
features including, e.g., body 246 disposed around housing
204 and receiver pad 238. Body 246 can be disposed
between substratum 202 and body cap 248 that can be
separated by spacer 256 and mechanically coupled with
fastener 254. Aligner 258 can be disposed on substratum 202
to align components of position verification sensor 200.
[0049] In position verification sensor 200, substratum 202
provides a supporting structure for disposition of other
elements thereon. It is contemplated that substratum 202 can
include aligner 258 to bound body 246, which can be a flat
surface upon which body 246 is disposed and holes to enable
mechanical connection to spacer 256. Exemplary substrata
202 include metal, polymer, glass, and the like. Moreover,
substrata can be fabricated within tolerances to provide a
selected level of measurement precision. Dimensions of
substrata include a diameter of aligner 258, diameter of
holes to mechanically couple spacers, flatness of bottom
face of substrata, and flatness of surface that body 246 rests.
A size, e.g., a largest linear dimension of substratum 202,
can be selected for a particular application such as several
microns to meters. In an embodiment with reference to FIG.
9, substratum 202 includes aligner 258 to bound body 246,
a bottom flat surface, a flat surface which body 246 rests,
holes to mechanically couple spacer 256, and holes to
mechanically couple the substratum 202 to an external
surface for practical use

[0050] Body 246 can include an external surface to protect
sensor 200 components from environmental forces such as
moisture, dust, and debris; internal surface to encapsulate
and appropriately constrain internal elements of sensor 200;
bottom surface to mechanically rest on substratum 202, and
top surface to mechanically receive body cap 248. Exem-
plary bodies 246 include metal, polymer, glass, and the like.
Moreover, body 246 can have a low internal friction to
provide unobstructed movement of housing 204. The outer
diameter of body 246 should be nominally smaller than the
inner dimension of aligner 258 so that the body 246 is firmly
constrained in X and Y directions. The inner diameter of
body 246 can be larger than the outer diameter of housing
204 such that housing 204 can move in a Z-direction but not
move in X- or Y-directions in a Cartesian frame. In an
embodiment with reference to FIG. 9, body 246 is a
machined plastic cylinder that has an outer diameter nomi-


US 2020/0086501 Al

5. The position verification sensor of claim 1, further
comprising an electrical contact disposed on the aperture cap
and in electrical communication with the receiver pad.

6. The position verification sensor of claim 5, further
comprising a second electrical contact disposed on the
receiver pad and in electrical communication with the elec-
trical contact.

7. The position verification sensor of claim 1, further
comprising a second receiver pad disposed on the cap
surface of the aperture cap, wherein the aperture cap is
interposed between the second receiver pad and the receiver
pad,

the second receiver pad comprising a second keyway

aperture that communicates the key through the second
keyway aperture to the aperture cap when the key has
a size and orientation that are compatible with a size
and orientation of the second keyway aperture.

8. The position verification sensor of claim 7, wherein the
second receiver pad:

receives contact with the key when the key is communi-

cated through a third keyway aperture and the key is not
aligned with the second keyway aperture;

produces a second target output in response to contact

with the key; and

produces a second null output in absence of contact with

the key.

9. The position verification sensor of claim 8, further
comprising a second aperture cap disposed over the second
receiver pad, wherein the second receiver pad is interposed
between the second aperture cap and the aperture cap, the
second aperture cap disposed on a second housing and
comprising:

a second cap surface; and

the third keyway aperture disposed in the second aperture

cap and bounded by a second wall of the second
aperture cap, the third keyway aperture comprising a
shape and size selected to receive and selectively
communicate the key through the third keyway aper-
ture, such that the second aperture cap:
selectively communicates the key through the third
keyway aperture to the second receiver pad when the
key and the third keyway aperture are compatibly
aligned; and
receives the key on the second cap surface when the
key and the third keyway aperture are incompatibly
aligned so that:
the key contacts the second cap surface instead of
being communicated through the third keyway
aperture; and
receives the depression force from the key.

Mar. 19, 2020

10. The position verification sensor of claim 9, further
comprising a second housing disposed on the substratum
and:

in which the second receiver pad and the receiver pad are

disposed; and

‘on which the second aperture cap is disposed.

11. The position verification sensor of claim 10, further
comprising a second compliant member interposed between
the substratum and the second housing through which the
substratum and the second housing are in mechanical com-
munication and that:

rests in a second primary position in an absence of the key

disposed on the second cap surface of the second
aperture cap;

receives the depression force from the second aperture

cap;

reciprocatively depresses, from the second primary posi-

tion to a second depressed position, in response to
receiving the depression force and being pushed by the
depression force from the key; and

reciprocatively returns, from the second depressed posi-

tion to the second primary position, when the key is
removed from contact with the second aperture cap.

12. A process for determining an accuracy of mutual
mechanical positioning of a key and the position verification
sensor of claim 1, the process comprising:

moving the key relative to the position verification sensor;

contacting position verification sensor with the key;

producing the null output if the key does not contact the
receiver pad; and

producing the target output if the key contacts the receiver

pad to determine the accuracy of the mutual mechanical
positioning of the key and the position verification
sensor.

13. A process for determining an accuracy of mutual
mechanical positioning of a key and the position verification
sensor of claim 11, the process comprising:

moving the key relative to the position verification sensor:

contacting position verification sensor with the key;

producing the null output if the key does not contact the
receiver pad; and

producing the second target output if the key contacts the
second receiver pad to determine the accuracy of
mutual mechanical positioning of the key and the
position verification sensor.

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US 2020/0086501 Al

Mar. 19, 2020 Sheet 13 of 33

Patent Application Publication

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US 2020/0086501 Al

Mar. 19, 2020 Sheet 23 of 33

Patent Application Publication

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US 2020/0086501 Al

rality of receiver pads 238 to provide a selected accuracy of
measurement with a plurality of aperture caps 206 and
keyway apertures 208

[0075] Position verification sensor 200 and processes
herein unexpectedly provide determination of accuracy of a
positioning system prior to accuracy degradation that can
negatively impacting a manufacturing process and provide
ascertainment of change in accuracy of a robot work cell
prior to a change in accuracy resulting in a negative impact
on a manufacturing process that decreases part quality,
process productivity, or asset availability below acceptable
thresholds. Further, position verification sensor 200 can
include a plurality of keys 236 disposed in a plurality of
locations including a tool flange of a robot, the physical
body of the tool, a dynamic face of the tool (i.e., moving
fingers of a gripper), and on an exemplar part that the robot
manipulates.

[0076] The articles and processes herein are illustrated
further by the following Example, which is non-limiting,

EXAMPLE

[0077] Examining Work cell Kinematic Chains to Identify
Sources of Positioning Degradation

[0078] Automated industrial work cells are becoming
increasingly complex and varied due to greater accessibility
of advanced robotic and sensing technologies. Degradation
monitoring and diagnostics can improve to reduce the
impact of increased system complexity on troubleshooting
faults and failures and to optimize system operations. A
position verification sensor monitors kinematic chains com-
monly found in robot work cells and provides identification
of degraded components that contribute to relative position-
ing accuracy error between moving objects, tools, devices,
and other components. Industrial robot users and integrators
can integrate the position verification sensor to examine
kinematic chains within work cells. With the position veri-
fication sensor, degradations can be identified at a selected
resolution for improved maintenance planning and produc-
tion control.

[0079] Robotics, along with supporting sensing and auto-
mation technologies, are used for a variety of tasks through-
out the manufacturing industry. As robotic and sensor tech-
nologies have evolved, the diversity and complexity of use
cases have grown. There is a need to better understand the
health and wear of these automation systems, as the manu-
facturing community increases their reliance on advanced
technologies. Systems can be maintained more efficiently,
leading to a more robust process when health information is
generated,

[0080] An element of industrial robot work cells is reliable
and repeatable positioning. In some robot work cells, a six
degree of freedom (6DOF) industrial robot arm is used as a
macro positioner for an end effector as tooling mounted to
the tool flange of the robot. The tool may be a gripper in a
material handling application, or it could be a welding gun,
paint applicator, or tooling for another operation. A work cell
can be configured such that the end effector is changed
during operations to enable a single robot to serve as the
macro positioner for multiple tasks. Reliability of position
ing accuracy for robots is provided by position verification
sensor.

[0081] ‘The position verification sensor provides informa-
tion germane to monitoring kinematic chains found in
robotic work cells. The position verification sensor can be

Mar. 19, 2020

used in many environments including a 6DOF industrial
robot arm work cell and is a low-cost, minimally invasive
article that determines health of a robot work cell and
provides where in a kinematic chain positional errors are
originating. The position verification sensor can verify and
validate health monitoring of work cell technologies.
[0082] The Prognostics and Health Management (PHM)
community is focused on advancing monitoring, diagnostic,
and prognostic capabilities to maintain or improve asset
availability, product or process quality, and productivity of
a range of operations, including those within manufacturing.
PHM has been actively applied to manufacturing factories
with varying success. This has included the development
and implementation of numerous strategies to minimize
reactive maintenance and optimize the balance between
preventive and predictive maintenance.

[0083] Most manufacturing robot work cells can be con-
sidered complex systems of systems. The overall physical
system can be broken down into sub-systems, components,
sub-components, etc. Decomposing the physical elements of
a robot work cell into a hierarchy of elements offers a means
of defining boundaries that can drive maintenance activities.
This physical hierarchy can be connected with functional
and informational hierarchies to provide a means of under-
standing complex relationships and identifying metrics and
measures of work cell health. The more complex a system,
the more critical it becomes to understand its inherent
relationships to see how the state of mechanical degradation
of physical elements impacts process performance.

[0084] Research has been performed in monitoring the
health, including positioning, of a robot, itself, separate from
the work cell. Vision and laser tracker systems are two types
of technologies that have been paired with PHM algorithms
to enhance health awareness. There is a need to expand the
health monitoring capabilities beyond the robot, itself, and
to consider the entire robot work cell. Understanding and
monitoring the positioning health of all elements of kine-
matic chains is a necessary part of a comprehensive PHM
system for robot work ceils. Prior research has been per-
formed in monitoring the health of robot work cells, yet
research has not been found that focuses specifically on
monitoring kinematic chain health. Existing robot monitor-
ing approaches present unique solutions that are either too
high-level and lacking specific guidance or rely upon poten-
tially costly technology. The position verification sensor
provides monitoring and analyzing the kinematic chain for
positional degradation in a cost-effective and minimally-
intrusive manner to increase benefit for the robot work cell
owners and users.

[0085] Kinematic chains can be documented at various
levels of complexity for the same mechanism. At the most
detailed level, a kinematic chain contains all bodies, includ-
ing components and sub-components, fasteners, and other
parts. The documentation of some kinematic chains may
only include links between actuated joints or express entire
actuated assemblies as single links.

[0086] It is beneficial to observe multiple points along a
kinematic chain in a serial manipulator to monitor position-
ing accuracy and identify the source of positioning errors
By inspecting repeatability at multiple points along a chain,
the source of repeatability degradation can be narrowed
down to the component(s) located between adjacent inspec-
tion points. To facilitate this, a way of representing a
kinematic chain is needed that provides sufficient detail to



Patent Application Publication Mar. 19, 2020 Sheet 4 of 33 US 2020/0086501 Al

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US 2020/0086501 Al

POSITION VERIFICATION SENSOR WITH
DISCRETE OUTPUT

CROSS REFERENCE TO RELATED
APPLICATIONS

[0001] The application claims priority to U.S. Provisional
Patent Application Ser. No. 62/732,059 filed Sep. 17, 2018,
the disclosure of which is incorporated herein by reference
in its entirety.

STATEMENT REGARDING FEDERALLY
SPONSORED RESEARCH

[0002] This invention was made with United States Gov-
ernment support from the National Institute of Standards and
Technology (NIST), an agency of the United States Depart-
ment of Commerce. The Government has certain rights in
the invention. Licensing inquiries may be directed to the
Technology Partnerships Office, NIST, Gaithersburg, Md.,
20899; voice (301) 301-975-2573; email tpo@nist.gov; ref-
erence NIST Docket Number 18-067US1

BRIEF DESCRIPTION

[0003] Disclosed is a position verification sensor that
produces a discrete output for determining an accuracy of
mutual mechanical positioning with a key, the position
verification sensor comprising: a substratum; a housing
disposed on the substratum; a receiver pad disposed in the
housing and that: receives contact with the key when the key
is communicated through a keyway aperture; produces a
target output in response to contact with the key: and
produces a null output in absence of contact with the key; an
aperture cap disposed on the housing and comprising: a cap
surface; and the keyway aperture disposed in the aperture
cap and bounded by a wall of the aperture cap, the keyway
aperture comprising a shape and size selected to receive and
selectively communicate the key through the keyway aper-
ture, such that the aperture cap: selectively communicates
the key through the keyway aperture to the receiver pad
when the key and the keyway aperture are compatibly
aligned; and receives the key on the cap surface when the
key and the keyway aperture are incompatibly aligned so
that: the key contacts the cap surface instead of being
communicated through the keyway aperture; and receives a
depression force from the key, the receiver pad being
interposed between the substratum and the aperture cap; and
a compliant member interposed between the substratum and
the housing through which the substratum and the housing
are in mechanical communication and that: rests in a pri-
mary position in an absence of the key disposed on the cap
surface of the aperture cap; receives the depression force
from the aperture cap; reciprocatively depresses, from the
primary position to a depressed position, in response to
receiving the depression force and being pushed by the
depression force from the key; and reciprocatively returns,
from the depressed position to the primary position, when
the key is removed from contact with the aperture cap.
[0004] A process for determining an accuracy of mutual
mechanical positioning of a key and position verification
sensor, the process comprising: moving the key relative to
the position verification sensor; contacting position verifi-
cation sensor with the key: producing the null output if the
key does not contact the receiver pad; and producing the
target output if the key contacts the receiver pad.

Mar. 19, 2020

[0005] A process for determining an accuracy of mutual
mechanical positioning of a key and position verification
sensor, the process comprising: moving the key relative to
the position verification sensor; contacting position verifi-
cation sensor with the key; producing the null output if the
key does not contact the receiver pad; and producing the
second target output if the key contacts the second receiver
pad

BRIEF DESCRIPTION OF THE DRAWINGS.

[0006] The following description should not be considered
limiting in any way. With reference to the accompanying
drawings, like elements are numbered alike

[0007] FIG. 1 shows a perspective view of a position
verification sensor;

[0008] FIG. 2 shows an exploded view of a position
verification sensor;

[0009] FIG. 3 shows a plan view of a position verification
sensor;
[0010] FIG. 4 shows a cross-section of the position veri-

fication sensor shown in FIG. 3;
[0011] FIG. 5 shows a position verification sensor in a
primary position in panel A and a depressed position in panel

[0012] FIG. 6 shows a position verification sensor in a
primary position in panel A and a depressed position in panel

[0013] FIG. 7 shows a position verification sensor with a
plurality of receiver pads;

[0014] FIG. 8 shows a position verification sensor in plan
view (panel A), perspective view (panel B), side view (panel
©), and cutaway view (panel D);

[0015] FIG. 9 shows an exploded view of the position
verification sensor shown in FIG. 8;

[0016] FIG. 10 shows a position verification sensor with a
button switch as a receiver pad:

[0017] FIG. 11 shows a plurality a position verification
sensors with different configurations of a receiver pad rela-
tive to an aperture cap;

[0018] FIG. 12 shows (A) an aperture cap in top view, (B)
a cross-section along line A-A shown in panel A for an
embodiment of the aperture cap, (C) a cross-section along
line A-A shown in panel A for another embodiment of the
aperture cap, and (D) a plurality of an aperture caps with
different shapes of a keyway aperture;

[0019] FIG. 13 shows a layout of elements of a position
verification sensor relative to a key and radial and rotational
tolerance with respect to the key;

[0020] FIG. 14 shows exemplary tolerances for elements
of a position verification sensor;

[0021] FIG. 15 shows (A) a plurality of relative positions
ofa key with respect to a position verification sensor and (B)
corresponding exemplary null output and target output for
the position verification sensor;

[0022] FIG. 16 shows (A) a plurality of relative positions
ofa key with respect to a position verification sensor and (B)
corresponding exemplary null output and target output for
the position verification sensor;

[0023] FIG. 17 shows a plurality of mutual mechanical
positioning of a key relative to a position verification sensor;
[0024] FIG. 18 shows a plurality of mutual mechanical
positioning of a key relative to a position verification sensor;
[0025] FIG. 19 shows a plurality of mutual mechanical
positioning of a key relative to a position verification sensor;


Patent Application Publication Mar. 19, 2020 Sheet 20 of 33. US 2020/0086501 Al

(a) Link Representation

LHS
(or f | Link jor)
| RHS
(b) Example: Robot
Robot Base |
[ _— Robot ao
Tool Flange

(c) Example: Gripper

Gripper Mounting |
f Gripper -——~)
| Gripper Fingers

Figure 20


US 2020/0086501 Al

Mar. 19, 2020 Sheet 26 of 33

Patent Application Publication

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Patent Application Publication Mar. 19, 2020 Sheet 22 of 33. US 2020/0086501 Al

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Figure 22


US 2020/0086501 Al

[0026] FIG. 20 shows a kinematic chain individual link
(A) for a generic link, (B) for a robot with permanent
connections at both interfaces, and (C) for a gripper with
intermittent connection on an element (¢.g., part) and per-
manent connection to another element (e.g., robot);

[0027] FIG. 21 shows a kinematic chain of two links (A)
in generic representation and (B) for a robot and gripper;
[0028] FIG. 22 shows (A) a material handling robot mov-
ing a part to a work fixture, (B) a drawing robot drawing on
the part, and (C) a material handling robot moving a
completed part to an output;

[0029] FIG. 23 shows a material handling robot kinematic
chain (A) in a graphical representation, (B) in a long-form
text representation, and (C) in a short-form text representa-
tion;

[0030] FIG. 24 shows material handling robot relation-
ships (A) for a robot base to a table, (B) for a robot tool
flange to a gripper mounting, (C) for gripper fingers to a part
when ona fixture, and (D) for a fixture to table;

[0031] FIG. 25 shows annotated generic link inspection;
[0032] FIG. 26 shows a measurement point selection;
[0033] FIG. 27 shows a binary decision tree to identify a

degraded component;

[0034] FIG. 28 shows perspective view of a position
verification sensor with a plurality of receiver pads:

[0035] FIG. 29 shows a side view of the position verifi-
cation shown in FIG. 28;
[0036] FIG. 30 shows a cutaway view of the position
verification sensor shown in FIG. 28;

[0037] FIG. 31 shows a plan view of the position verifi-
cation sensor shown in FIG. 28:

[0038] FIG. 32 shows an exploded view of the position
verification sensor shown in FIG. 28; and

[0039] FIG. 33 shows a graph of output voltage versus
receiver pad depth for a position verification sensor 200.

DETAILED DESCRIPTION

[0040] A detailed description of one or more embodiments
is presented herein by way of exemplification and not
limitation.

[0041] It has been discovered that position verification
sensor 200 herein includes compliant member 214 and that,
when key 236 is presented to position verification sensor
200, position verification sensor 200 provides a binary
output that depends on whether key 236 is presented within
a selected tolerance of nominal value. Position verification
sensor 200 and key 236 pairing provides verification of
repeatable positioning of key 236 by a device, e.g., a robot,
on which key 236 is attached.

[0042] It is contemplated that position verification sensor
200 and key 236 can be paired so that they interact in a very
specific geometrical way, wherein target output 230 or nuil
output 228 is produced by position verification sensor 200
based on the interaction. That is, when key 236 is presented
by relative physically motion to provide interact with posi-
tion verification sensor 200, the geometry and interaction
between key 236 and position verification sensor 200 deter-
mine which output of position verification sensor 200 is
produced. If key 236 is presented and positioned within a
selected tolerance, position verification sensor 200 produces
target output 230. Further, if key 236 is presented outside of
the selected tolerance, position verification sensor 200 pro-
duces null output 228.

Mar. 19, 2020

[0043] The industrial robotics industry has a need for more
precise work cells, e.g., a robotics work cell, that include
robots and surrounding equipment. During a lifetime of a
conventional robot work cell, components can degrade and
positioning of components can become less precise, wherein
a relative position among components in repeated tasks can
drift. Maintenance can conserve precision of robotic move-
ments and can occur by replacement or recalibration of
components. Therefore, there is a need to measure and track
degradation of positioning precision, provided by position
verification sensor 200. Advantageously, position verifica-
tion sensor 200 provide a cost-effective and easy-to-inte-
grate article for environments such as the manufacturing
community, wherein position verification sensor 200 can be
deployed or operated to detect changes in precision of
positioning of components within a work cell.

[0044] Position verification sensor 200 produces a discrete
output 210 for determining an accuracy of mutual mechani-
cal positioning with a key 236. In an embodiment, with
reference to FIG. 1, FIG. 2, FIG. 3, FIG. 4, and FIG. 15,
position verification sensor 200 includes: substratum 202;
housing 204 disposed on substratum 202; and receiver pad
238 disposed in housing 204. Receiver pad 238 receives
contact with key 236 when key 236 is communicated
through keyway aperture 208; produces target output 230 in
response to contact with key 236; and produces null output
228 in absence of contact with key 236. Aperture cap 206 is
disposed on housing 204 and includes: cap surface 207; and
keyway aperture 208 disposed in aperture cap 206 and
bounded by wall 209 of aperture cap 206. Keyway aperture
208 includes a shape and size selected to receive and
selectively communicate key 236 through keyway aperture
208, such that aperture cap 206: selectively communicates
key 236 through keyway aperture 208 to receiver pad 238
when key 236 and keyway aperture 208 are compatibly
aligned; and receives key 236 on cap surface 207 when key
236 and keyway aperture 208 are incompatibly aligned so
that: key 236 contacts cap surface 207 instead of being
communicated through keyway aperture 208; and receives
depression force 212 from key 236. Receiver pad 238 is
interposed between substratum 202 and aperture cap 206.
Compliant member 214 is interposed between substratum
202 and housing 204 through which substratum 202 and
housing 204 are in mechanical communication. Compliant
member 214 rests in primary position 218 in an absence of
key 236 disposed on cap surface 207 of aperture cap 206;
receives depression force 212 from aperture cap 206; recip-
rocatively depresses, from primary position 218 to
depressed position 220, in response to receiving depression
force 212 and being pushed by depression force 212 from
key 236; and reciprocatively returns, from depressed posi-
tion 220 to primary position 218, when key 236 is removed
from contact with aperture cap 206.

[0045] In an embodiment, pad support 232 is mechani-
cally interposed between receiver pad 238 and substratum
202. Pad support 232 depresses in response to contact of key
236 with receiver pad 238 so that receiver pad 238 can move
away from or toward aperture cap 206 and substratum 202
In some embodiments, as shown in FIG. 11, receiver pad
238 is disposed on aperture cap 206 in an absence of pad
support 232. It further is contemplated that movement of the
pad support can be replaced with an electrical or optical
interaction. For an optical interaction, a light beam can be
intersected by the key or an optical sensor, e.g., an infrared


US 2020/0086501 Al

Mar. 19, 2020 Sheet 17 of 33

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Patent Application Publication Mar. 19, 2020 Sheet 6 of 33 US 2020/0086501 Al

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US 2020/0086501 Al

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Patent Application Publication Mar. 19, 2020 Sheet 24 of 33. US 2020/0086501 Al

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as) United States

US 20200086501A1

a2 Patent Application Publication 1) Pub. No.: US 2020/0086501 A1

Klinger et al.

(43) Pub. Date: Mar. 19, 2020

(54) POSITION VERIFICATION SENSOR WITH
DISCRETE OUTPUT

(71) Applicant: Government of the United States of
America, as represented by the
Secretary of Commerce, Gaithersburg,
MD (US)

(72) Inventors: Alexander Scott Klinger, Silver

Spring, MD (US); Brian Adam Weiss,

Boyds, MD (US)

16/572,847
Sep. 17, 2019

Related U.S. Application Data

Provisional application No. 62/732,059, filed on Sep
17, 2018.

(21)
(22)

Appl. No.:
Filed:

(60)

Publication Classification

Int. Cl.
B25J 13/08
GOIB 7/31
B25J 9/16

(51)
(2006.01)
(2006.01)
(2006.01)

207.1.

207.2

(52) US. CL
CPC eevee -B23SF 13/087 (2013.01); B25F 9/1653
(2013.01); GOLB 7/31 (2013.01)

(57) ABSTRACT

A position verification sensor produces a discrete output for
determining an accuracy of mutual mechanical positioning
with a key and includes: a substratum; a housing; a receiver
pad that: receives contact with the key; produces a target
output in contact with the key; and produces a null output in
absence of contact with the key; an aperture cap having: a
cap surface; and the keyway aperture that selectively com-
municates the key; and a compliant member that: rests in a
primary position in an absence of the key disposed on the
cap surface; receives the depression force from the aperture
cap; reciprocatively depresses, from the primary position to
a depressed position, in response to receiving the depression
force and being pushed by the depression force from the key;
and reciprocatively returns, from the depressed position to
the primary position, when the key is removed from contact
with the aperture cap.

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US 2020/0086501 Al

Mar. 19, 2020 Sheet 11 of 33

Patent Application Publication

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Patent Application Publication Mar. 19, 2020 Sheet 10 of 33. US 2020/0086501 Al

so 236

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US 2020/0086501 Al

positions. After the RHS of the second link is tested suc-
cessfully, the interface between the first and second link can
be declared nominal and all parts of the second link are
positioned nominally. This is represented in FIG. 25(b).

[0096] The decision of whether a component is being
positioned nominally and a test is successful will depend on
the designed allowance in the system. Due to tolerance
stacking, it is not unusual to expect the allowance of
components further from the reference in the kinematic
chain to be higher and must be considered when choosing
the sensor(s) used for inspection. It can also be beneficial to
choose inspection points other than the RHS of links in the
kinematic chain depending on the work cell. To help choose
these points, an analysis of modes of positioning degrada-
tion is recommended.

[0097] With regard to identifying positioning degradation
modes along the kinematic chain, sources of positional
relationship issues can be identified once the kinematic
chain and the interactions between components are mapped.
The type and cause of positioning error will vary based upon
the components within the work cell. Degradation modes
can be found by assessing each link and the interactions
between the links.

[0098] A link can be actuated, like a robot, or rigid, like a
part. These two types of links can degrade in many ways
which can be classified as either rigid body deformations, or
degraded actuation and positioning. With an actuated link,
such as a robot arm, if any joint in the robot is not
positioning itself correctly, the tool flange and end effector
will not be positioned correctly. These positioning errors can
present themselves instantaneously after crashes or over
time after wear. Likewise, deformation of rigid bodies can
occur instantaneously or over time. For example, gripper
fingers may bend when colliding with a foreign object in the
work cell as compared to the fingers fatiguing and bending
over time after repeated use. Each link is susceptible to
degradation and will influence how that component and the
rest of the work cell performs.

[0099] In addition to the positioning error modes from the
links, themselves, the interactions between the links must be
studied to assess the impact of link degradation on the
relationships. Many different interactions can exist within
the work cell. Couplings between components are either
permanent or intermittent. Generally, the interface between.
two components is critical when the components’ interaction
is intermittent. This type of interaction requires the compo-
nents to be in their designed positions and may involve a
specific actuation for coupling. This means that if a com-
ponent is positioned improperly, the geometry is inaccurate
or unexpected, or a component cannot actuate as intended to
successfully execute the interaction, the process can be
considered degraded and may not perform nominally. For
example, when a part is being grasped by a gripper, the part
must have the expected geometry and be properly positioned
for the gripper which must be in the expected position and
actuate as designed to successfully grasp the part.

[0100] A variety of positioning degradation modes were
identified within the use case. Degradation modes were
identified for the components of the kinematic chain as well
as the interactions between components. Starting at the
world frame and examining the kinematic chain of FIG. 23,
moving left to right, modes are identified. The Table lists
identified degradation modes.

Mar. 19, 2020

TABLE

Kinematic Chain Section Degradation Mode(s)

World Frame][Robot Base Loose Connection

[Robot Base, ROBOT, Robot Too! Flange] Robot Wear
Robot Too! Flange|[Gripper Mounting Loose Connection
[Gripper Mounting, GRIPPER, Gripper Fingers] Gripper Wear
Gripper Fingers)(Part Geometry Gripper Wear,
Bad Part*
[PART] Bad Part®
Part Geometry)(Fixture Geometry Bad Part",
Bad Fixture**
[Fixture Geometry, Fixture, Fixture Mounting] Bad Fixture*®

Fixture Mounting)[World Frame Loose Connection

From either part innecuraey or damage
‘**From cither fixture positioning inaccuracy or fixture wear‘damage

[0101] The modes internal to components, including robot
wear, gripper wear, bad parts, and fixture wear are expressed
as between the LHS and RHS of their respective compo-
nents. The connection is assumed as the only failure mode
between two links that are permanently fixed to one another
and other modes are considered as part of the components

For the intermittent interactions between the part and the
gripper, and the part and the fixture, any of the components
can contribute to positioning error leading to multiple modes
listed.

[0102] With regard to selection of key measurement points
to identify points or areas of degradation and the position
verification sensor, discrete points along the kinematic chain
can be selected for inspection to detect positioning devia-
tions from nominal or verify nominal positioning. These key
measurement points were tested in one or more degrees of
freedom to determine if they can be positioned within
designed limits. Each point was chosen to provide informa-
tion on the source of a positioning error when measured in
a specific order. A starting point in a LHS-referenced kine-
matic chain is the RHS of each link in the chain. Inspecting
the RHS of each link will provide insight into the repeat-
ability of each component. However, if a component such as
an end effector is actuated, it may be beneficial to inspect
both the RHS and another point earlier in the kinematic
chain. Inspecting before an actuation point of a particular
component, the source of repeatability degradation can be
isolated to within the component or to the connection
between the component and the preceding component. Addi-
tionally, an actuated component can be inspected in multiple
configurations or states to provide further isolation of deg-
radation.

[0103] Applying this methodology to the use case, the key
points selected were the robot tool flange, gripper fingers,
and part geometry because they are the RHS of the compo-
nents of the chain. Because the fixture link is directly
connected to the world frame on its RHS, the LHS of the
fixture link, fixture geometry, should be selected as a key
point. Examining the gripper further, it is actuated and can
have multiple states (ie. open, gripping a part, closed)
throughout its operations and can be inspected in more
places than only the RHS. By selecting the gripper body as
a key point before the finger actuation in the chain, the
gripper mounting can be tested independently of the finger
actuation. Likewise, testing the fingers in both an open and
closed state, the operation and positioning of the gripper
fingers can be tested independently of the gripper mounting.
To test the part geometry. the system must grasp an ideal part
so the part position can be tested in-situ. To test the fixture


Patent Application Publication Mar. 19, 2020 Sheet 31 of 33 US 2020/0086501 Al

254

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Figure 31


Patent Application Publication Mar. 19, 2020 Sheet 30 of 33. US 2020/0086501 Al

208 a9 307 254
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Patent Application Publication Mar. 19, 2020 Sheet 7 of 33 US 2020/0086501 Al

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Patent Application Publication Mar. 19, 2020 Sheet 21 of 33. US 2020/0086501 Al

{a) Generic Chain Representation  gerensnn sees:
: Physical
: interface
LHS 1)
Reference ]f : Link 2 }
- " RHS 2
{b) Example: Robot and Gripper
{Reference Frame |
\. Robot Base; | Gripper M
‘World Frame i Robot 4 : Gripper )

Gripper Fingers

Figure 21


US 2020/0086501 Al

positions (¢.g., 218.1, 218.2, and the like) can occur with a
plurality of target outputs (e.g., 230.1, 230.2, and the like).
[0056] Compliant member 214 provides displacement
motion of aperture cap 206 and housing 204 relative to
substratum 202 or receiver pad 238.

It is contemplated that the receiver pad is disposed in
housing 204 such that, when the receiver pad is subject to
pressure from key 236, the receiver pad maintains compli-
ance via compliant member 214 such that depressive force
212 of key 236 does not break receiver pad 238. In an
embodiment, receiver pad 238 is directly disposed on sub-
stratum 202 so that displacement of receiver pad 238 is less
than displacement of key 236 in contact with receiver pad
238. Compliant member 214 can include a material having
a selected spring force constant such as a spring or other
elastically or inelastically deformable material including
foam. Exemplary compliant members 214 include metal,
polymer, and the like. Moreover, the geometry of the spring
coils may be uniform, non-uniform, and the like. In an
embodiment, compliant member 214 includes a metal spring
made up of a stainless steel cylindrical coil; a coil diameter
that is less than the inner diameter of housing 204 such that
the lower surface of compliant member 214 mechanically
contacts the top surface of substratum 202 and the upper
surface of compliant member 214 mechanically contacts the
internal surface of housing 204 and compliant member 214
surrounds switch housing 252 and may not contact switch
housing 252.

[0057] It is contemplated that aperture cap 206 or receiver
pad 238 move in reciprocation direction 216 between pri-
mary position 218 and depressed position 220. Reciproca-
tion direction 216 can be linear, non-linear, rotary, diagonal,
ora selected trajectory path with respect to keyway aperture
208. Moreover, reciprocation direction 216 can be achieved
through velocities that are constant, linear, non-linear, and
the like; can be achieved through accelerations that are
constant, linear, non-linear, and the like.

[0058] With reference to FIG. 1, FIG. 2, FIG. 4, FIG. 5,
FIG. 6, and FIG. 11, pad support 232 is disposed on
substratum 202 and receiver pad 238 is disposed on pad
support 232. It is contemplated that pad support 232 can
include a compliant member that moves according to
depression force 212 in mechanical communication with
receiver pad 282 where receiver pad 238 would return to its
original state, position, or orientation upon removal of
depression force 212 from receiver pad 238. Exemplary pad
support 232 include metal, polymer, and the like.

[0059] With reference FIG. 1, FIG. 4, FIG. 7, FIG. 10, and
FIG. 15, key 236 presents a physical geometry to keyway
aperture 208 such that key 236 moves in reciprocation
direction 216, wherein key 236 applies depression force 212
on receiver pad 238 to achieve target state 226 or key 236
applies depression force 212 on cap surface 207 yielding
null state 224. It is contemplated that key 236 includes, e.g.,
a geometry shown in panel D or E of FIG. 12. Exemplary
key 236 include metal, polymer, glass, and the like. More-
over, key 236 can have dimensions that is less than or equal
to that of keyway aperture 208. With a plurality of keyway
apertures, the cross-sectional dimension of key 236 can be
equal to or less than the dimension of any keyway aperture.
In an embodiment, key 236 is a metal cylindrical pin with a
length of one inch and a diameter of 0.250 inches.

[0060] In position verification sensor 200, receiver pad
238 receives mechanical contact from key 236 through

Mar. 19, 2020

depression force 212 if key 236 communicates through
keyway aperture 208. Mechanical communication between
receiver pad 238 and key 236 produce target state 226
resulting in target output 230. It is contemplated that
receiver pad 238 can include an electrical contact or a
surface for mechanical coupling. Exemplary receiver pad
238 include metal, polymer, and the like. In an embodiment,
as shown in FIG. 9, receiver pad 238 is a push button switch
that is mechanically coupled to switch housing 252: is
connected to electrical contacts 240.1 and 240.2; mechani-
cally coupled to housing 204; directly below keyway aper-
ture 208 of aperture cap 206; produces a target output 230
when key 236 applies depression force 212 to receiver pad
238 and a null output 228 when key 236 does not apply
depression force 212 to receiver pad 238.

[0061] In FIG. 5, FIG. 6, and FIG. 17, electrical contact
240 is disposed on receiver pad 238 and remains in contact
with aperture cap 206 or second electrical contact 240.2 that
is disposed on aperture cap 206 and yields null state 224
producing null output 228. When receiver pad 238 receives
depression force 212, electrical contact 240 loses mechani-
cal communication from aperture cap 206 or electrical
contact 240.2 thereby producing target state 226 thus gen-
erating target output 230. Exemplary electrical contact 240
include metal and the like. Electrical contact 240 provides
suflicient electrical conductivity so that position verification
sensor 200 produces null output 228 and target output 230.
In an embodiment in reference to FIG. 5, FIG. 6, and FIG.
17, electrical contact 240 is a metal washer that is in
mechanical communication with electrical contact 240.2,
also a metal washer. In an embodiment, when depression
force 212 is applied to receiver pad 238, electrical contact
240 loses mechanical communication with 240.2 thereby
producing a target output in the form of opening an electrical
circuit.

[0062] In position verification sensor 200 in FIG. 5, FIG.
6, electrical conductor 242 transmits null output 228 and
target output 230 according the presence or absence of
depression force 212 on receiver pad 238 and receipt of
depression force 212 by receiver pad 238. A plurality of
electrical conductors 242 in presence of a plurality of
receiver pads 238 can include a plurality of target outputs
230. Exemplary electrical conductors 242 include metal and
the like. Moreover, electrical conductor can include suffi-
cient electrical conductivity to communicate null output 228
and target output 230. In an embodiment, electrical conduc-
tor 242 are comprised of electrical conductor 242.1 and
electrical conductor 242.2; electrical conductor 242.1 is in
mechanical communication with electrical contact 240.1;
electrical conductor 242.2 is in mechanical communication
with electrical contact 240.2; electrical conductor 242.1 and
electrical conductor 242.2 present an open 8V DC circuit
when receiver pad 238 is not in mechanical communication
with depression force 212; electrical conductor 242.1 and
electrical conductor 242.2 present a closed 8V DC circuit
when receiver pad is in mechanical communication with
depression force 212. In an embodiment with a plurality of
receiver pads 238, there is a plurality of electrical conductor
242.1 and electrical conductor 242.2.

[0063] Retainer 244 can be disposed on aperture can 206
opposing cap surface 207 to retain receiver pad 238 on
aperture cap 206. In reference to FIG. 9, body cap 248 is in
mechanical communication with body 246 and spacers 256,
and mechanically fastened in position with fasteners 254. It


US 2020/0086501 Al

is contemplated that body cap 248 can include a lower
surface to enable mechanical communication with body 246
to bind body 246 from translational movement in the Z
Direction; lower surface contains an aligner 258 to mechani-
cally constrain the top of body 246 such that body 246 does
not move in the X Direction and Y Direction; holes to allow
fasteners 254 to pass through body cap 248 to mechanically
fasten spacers 256; and has a center hole sufficiently large
enough to enable key 236 to apply depression force 212 to
receiver pad 238 or key 236 to apply depression force 212
to aperture cap 206. body cap 248 Can include aligner 258
disposed thereon and opposing body 246 and substratum
202. It is contemplated that body 246 can be constrained
from having rotary motion about receiver pad 238, wherein
mechanical constraint can be accomplished through a mono-
lithic structure of body 246 and body cap 248 or a mechani-
cal obstructer such as a protuberance (e.g., a pin) that
engages body 246 or by a press fit to cause frictional forces.
Exemplary body caps 248 include metal, polymer, glass, and
the like. Moreover, body cap 248 have a rigidity so such that
mechanical communication with spacers 256 and body 246
through fasteners 254 do not substantially deform body cap
248 that otherwise might compromise its functions. In an
embodiment in reference to FIG. 9, body cap 248 is addi-
tively-manufactured plastic; has four symmetric holes
allowing four fasteners 254 to mechanically fasten to four
spacers 256; has an aligner 258 that mechanically con-
straints body 246 in the X and Y directions; has a lower
surface that mechanically constrains body 246 in the Z
direction; and has a center hole with diameter nominally
smaller than the diameter of aperture cap 206 such that
aperture cap 206 cannot rise above body cap 248.

[0064] With reference to FIG. 10, it is contemplated that
retainer member 250 is in mechanical communication with
housing 204 and provides structural support to electrical
contacts 240 and switch housing 252. Exemplary retainer
members 250 include metal, polymer, glass, and the like. In
an embodiment in reference to FIG. 9, retainer member 250
can be disposed on housing 204; is made of machined
stainless steel; is structured with a cylindrical hole having a
diameter that is larger than receiver pad 238 or smaller than
the diameter of switch housing 252 such that the switch
housing 252 and receiver pad 238 are mechanically con-
strained within housing 204

[0065] With reference to FIG. 9, FIG. 10, and FIG. 19, it
is contemplated that switch housing 252 can support
mechanical communication between receiver pad 238 and
electrical conductors 240.1 and 240.2. Exemplary switch
housings 252 include metal, polymer, glass, and the like.
The switch housing 252 is in mechanical communication
with retainer member 250. With reference to FIG. 32, for a
plurality of receiver pads 238, there can be a corresponding
quantity of switch housings 252 such that for every receiver
pad 238 there is a switch housing 252. In an embodiment as
shown in FIG. 9, switch housing 252 is constructed to be a
single part with receiver pad 238 and electrical conductors
240.1 and 240.2; is in mechanical communication with
retainer member 250; held in place with a fastener nut above
retainer member 250 and threaded around switch housing
252; held in place with a fastener nut below retainer member
250 and threaded around switch housing 252; is encapsu-
lated by compliant member 214 yet not switch housing 252
is not in mechanical communication with compliant member
214.

Mar. 19, 2020

[0066] With reference to FIG. 8 and FIG. 9, it is contem-
plated that fastener 254 binds mechanical communication
between aperture cap 206 and housing 204; fastener 254
binds mechanical communication between substratum 202
and spacer 256; fastener 254 binds mechanical communi-
cation between body cap 248 and spacer 256; fastener 254
can removable; and fastener 254 binds mechanical commu-
nication between aperture cap 206 and housing 204 and can
be different from fastener 254 that binds mechanical com-
munication between spacer 256 and substratum 202 and
body cap 248. Exemplar fasteners 252 include metal, poly-
mer, and the like. In an embodiment, with reference to FIG.
9 and FIG. 32, fastener 254 that binds mechanical commu-
nication between aperture cap 206 and housing 204 is a
metal socket head cap screw of screw size 1-72; fastener 254
that binds mechanical communication between substratum
202 and spacer 256 is a metal button head cap screw of
screw size 10-32; fastener 254 that binds mechanical com-
munication between substratum 202 and spacer 256 is a
metal button head cap screw of screw size 10-32: fastener
254 can be removed with an Allen wrench tool of appro-
priate size for a 1-72 socket head cap screw; and fastener
254 can be removed with a commonly-available Allen
wrench tool of appropriate size for a 10-32 button head cap
screw. For a plurality of aperture caps 206, fastener 254
remains a metal socket head cap screw of screw size 1-72 for
binding all aperture caps 206 with all housings 204.

[0067] With reference to FIG. 8, FIG. 9, FIG. 28, FIG. 29,
FIG. 30, and FIG. 32, spacer 256 provides support for body
246 and elements internal to body 246 with a plurality of
spacers 256 to provide an structural support around body
246 and its internal elements; spacer 256 is in mechanical
communication with substratum 202: spacer 256 is fastened
to substratum 202 with fastener 254; spacer 256 is in
mechanical communication with body cap 248; spacer 256
is fastened to body cap 248 with fastener 254; and spacer
256 has a hole and internal surface to bind fastener 254.
Exemplary fasteners 254 include metal, polymer, and the
like. In an embodiment in reference to FIG. 8 and FIG. 9,
four spacers 256 are shown; are hexagonal female threaded
standoffs capable of receiving 10-32 machine screws; are
made of metal; are 1/2" in length; are in mechanical com-
munication with substratum 202; are in mechanical com-
munication with body cap 248; and spacers 256 are each
fastened to fasteners 254 that are 10-32 button head cap
screws. In an embodiment, with reference to FIG. 28, FIG.
29, FIG. 30, and FIG. 32, a plurality of receiver pads 238 and
four spacers 256 are shown with hexagonal female thread
standoffs that receive 10-32 machine screws; are made of
metal; are 4" in length; are in mechanical communication
with substratum 202; are in mechanical communication with
body cap 248; and spacers 256 are each fastened to fasteners
254 that are 10-32 button head cap screws.

[0068] With reference to FIG. 8, FIG. 9, FIG. 28, and FIG.
32, aligner 258 is in mechanical communication with sub-
stratum 202 and body 246 to constrain movement of body
246 in the X direction and the Y direction; aligner 258.2
(disposed on body cap 248 opposing substratum 202) is in
mechanical communication with body cap 248 and body 246
to constrain movement of body 246 in the X direction and
the Y direction. Exemplary aligners 258 include metal,
polymer, glass, and the like. Dimensions of aligner 258 can
be selected such that its internal dimension is larger than the
external dimension of body 246 such that body 246 is


Patent Application Publication

Test Robot Tool
Flange

Test Gripper Body

Pass
. An

Test Gripper

Mar.

19, 2020 Sheet 27 of 33. US 2020/0086501 Al

4 c

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Figure 27


US 2020/0086501 Al

Mar. 19, 2020 Sheet 3 of 33

Patent Application Publication

207

206

ford
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a

ns a Oe ae cans

a San a See

Figure 3


US 2020/0086501 Al

geometry, a sensor can be mounted to or embedded in the
fixture. These points are represented in FIG. 26.

[0104] Appropriate tolerancing or analysis thresholding
was chosen for the pass or fail classification of each of the
key points selected. Given the tolerance and monitoring
requirements of the use case, appropriate sensors were
chosen. The key points were tested in a sequence following
the kinematic chain, left-to-right, once the sensors were
integrated. The feedback from testing provided a series of
binary decisions to identify degraded components. Decision
trees and testing criteria can be dependent on the use case.
The decision tree and testing flow for use case is shown in
FIG. 27. This series of tests can be performed at any interval
and records kept, aiding in the tracking of degradations and
predicting future degradation. If the tests are done in the
prescribed order, according to FIG. 27, a failed test indicates
where, in the kinematic chain, a degradation is originating,
providing a target component to repair or replace. After a
failure of a test point, all points tested further along the
kinematic chain may be unreliable without understanding of
the cause of the failed test.

[0105] Measuring or testing the selected key points along
the kinematic chain can be done in many ways. Regardless
of the specific details, there will be a sensor and a target,
which the sensor measures. Measurements can be made
through physical contact, visual imaging, or another type of
measurement technology. In the position verification sensor,
the position verification sensor outputs information on the
position of a specific point or object.

[0106] While one or more embodiments have been shown
and described, modifications and substitutions may be made
thereto without departing from the spirit and scope of the
invention. Accordingly, it is to be understood that the present
invention has been described by way of illustrations and not
limitation, Embodiments herein can be used independently
or can be combined.

[0107] All ranges disclosed herein are inclusive of the
endpoints, and the endpoints are independently combinable
with each other. The ranges are continuous and thus contain
every value and subset thereof in the range. Unless other-
wise stated or contextually inapplicable, all percentages,
when expressing a quantity, are weight percentages. The
suffix “(s)” as used herein is intended to include both the
singular and the plural of the term that it modifies, thereby
including at least one of that term (e.g., the colorant(s)
includes at least one colorants). “Optional” or “optionally”
means that the subsequently described event or circumstance
can or cannot occur, and that the description includes
instances where the event occurs and instances where it does
not. As used herein, “combination” is inclusive of blends,
mixtures, alloys, reaction products, and the like.

[0108] As used herein, “a combination thereof” refers to a
combination comprising at least one of the named constitu-
ents, components, compounds, or elements, optionally
together with one or more of the same class of constituents,
components, compounds, or elements.

[0109] All references are incorporated herein by reference.
[0110] The use of the terms “a” and “an” and “the” and
similar referents in the context of describing the invention
(especially in the context of the following claims) are to be
construed to cover both the singular and the plural, unless
otherwise indicated herein or clearly contradicted by con-
text. “Or” means “and/or.” It should further be noted that the
terms “first,” “second,” “primary.” “secondary,” and the like

Mar. 19, 2020

herein do not denote any order, quantity, or importance, but
rather are used to distinguish one element from another. The
modifier “about” used in connection with a quantity is
inclusive of the stated value and has the meaning dictated by
the context (e.g., it includes the degree of error associated
with measurement of the particular quantity). The conjunc-
tion “or” is used to link objects of a list or alternatives and
is not disjunctive; rather the elements can be used separately
or can be combined together under appropriate circum-
stances.

What is claimed is:

1. A position verification sensor that produces a discrete
output for determining an accuracy of mutual mechanical
positioning with a key, the position verification sensor
comprising:

a sub stratum;

a housing disposed on the substratum;

a receiver pad disposed in the housing and that:

receives contact with the key when the key is commu-
nicated through a keyway aperture;

produces a target output in response to contact with the
key; and

produces a null output in absence of contact with the
key;

an aperture cap disposed on the housing and comprising:

a cap surface; and
the keyway aperture disposed in the aperture cap and
bounded by a wall of the aperture cap, the keyway
aperture comprising a shape and size selected to
receive and selectively communicate the key through
the keyway aperture, such that the aperture cap:
selectively communicates the key through the key-
way aperture to the receiver pad when the key and
the keyway aperture are compatibly aligned; and
receives the key on the cap surface when the key and
the keyway aperture are incompatibly aligned so
that:

the key contacts the cap surface instead of being
communicated through the keyway aperture;
and
receives a depression force from the key,
the receiver pad being interposed between the substra-
tum and the aperture cap; and

a compliant member interposed between the substratum

and the housing through which the substratum and the

housing are in mechanical communication and that:

rests in a primary position in an absence of the key
disposed on the cap surface of the aperture cap;

receives the depression force from the aperture cap;

reciprocatively depresses, from the primary position to
a depressed position, in response to receiving the
depression force and being pushed upon by the key;
and

reciprocatively returns, from the depressed position to
the primary position, when the key is removed from
contact with the aperture cap.

2. The position verification sensor of claim 1, further
comprising a pad support mechanically interposed between
the receiver pad and the substratum.

3. The position verification sensor of claim 2, wherein the
pad support depresses in response to contact of the key with
the receiver pad.

4. The position verification sensor of claim 1, wherein the
receiver pad is disposed on the aperture cap.


US 2020/0086501 Al

Mar. 19, 2020 Sheet 14 of 33

Patent Application Publication

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Patent Application Publication Mar. 19, 2020 Sheet 16 of 33. US 2020/0086501 Al

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US 2020/0086501 Al

Mar. 19, 2020 Sheet 2 of 33

Patent Application Publication

Figure 2


US 2020/0086501 Al

nally smaller than the aligner 258; has an inner diameter that
is larger than the outer diameter of housing 204 enabling
housing 204 to move in the Z-direction based upon depres-
sion force 212; and is mechanically constrained by substra-
tum 202 and body cap 248.

[0051] Housing 204 can include an external surface such
that it can be reasonably constrained by body 246; a down-
ward facing surface that is in mechanical communication
with compliant member 214; provides a hole or surface for
mechanically coupling to switch housing 252; provides a
surface for mechanical communication with aperture cap
206; and provides a mechanical coupling to aperture cap
206, Exemplary housings 204 include metal, polymer, glass,
and the like. Moreover, housing 204 can have a smooth outer
diameter surface so that Z movement of housing 204 within
body 246 is not hindered frictionally and can have dimen-
sional tolerances that provides minimal X or Y movement
during operation. In an embodiment with reference to FIG.
9, housing 204 is machined stainless steel; includes an outer
diameter that is nominally smaller than the inner diameter of
body 246; an outer surface that has a relatively low surface
roughness to promote low friction and smooth Z movement
with body 246; a hole or surface to mechanically constrain
switch housing 252; a surface to mechanically contact
aperture cap 206; and machined holes to appropriately
accept fasteners 254 to mechanically bind aperture cap 206
to housing 204.

[0052] Aperture cap 206 is disposed on housing 204 and
includes cap surface 207 and keyway aperture 208. Aperture
cap 206 can include a material such as a metal, polymer,
glass, and the like. It is contemplated that aperture cap 206
can accept a plurality of contacts with key 236. In this
respect, aperture cap 206 can have a hardness selected to
withstand contact with key 236 in an absence of deformation
of aperture cap 206 to avoid artificial movement of receiver
pad 238 in lieu of direct contact by key 236. Moreover,
aperture cap 206 can have a shape and size for use in a work
cell, including those that involve robotics. With reference to
panel B of FIG. 12, a first size D1 of keyway aperture 208
can be some dimension larger than the dimension of key
236. A second size D2 of keyway aperture 208 can be some
dimension identical to or smaller than dimension of first size
D1. Moreover, with reference to panel C, aperture cap 206
can include bevel angle 234 for keyway aperture 208 with
respect to cap surface 207. Bevel angle 234 can be between
0 and 180 degrees. It is contemplated that keyway aperture
208 can have a shape that constrains key 236 to a particular
angle, size, orientation, and the like for alignment to keyway
aperture 208 so that key 236 can be communicated through
keyway aperture 208 if key 236 and keyway aperture 208
compatibly aligned. Otherwise, key 236 is intercepted by
cap surface 207 and not communicated through keyway
aperture 208 so that key 236 cannot contact receiver pad
238. Exemplary shapes for keyway aperture 208 are shown
in panel D of FIG. 12. An aperture cap 206 can include a
plurality of keyway apertures 208, wherein keyway aper-
tures independently can include a shape, e.g., a shape shown
in panel D of FIG. 12. As shown in panel E of FIG. 13, a
plurality of keyway apertures 208 can be disposed such that
a plurality of keys, having a same or different shape, can be
tested or a key that includes a combination geometry (e.g.,
a square cross-sectional shape in one portion of the key and
a circular cross-section at another portion of the key) can be
tested. Also shown in panel E of FIG. 13, keyway apertures

Mar. 19, 2020

208 can be disposed in aperture cap 206, wherein keyway
apertures 208 have the same geometry and different dimen-
sions. Key 236 can interact with keyway apertures 208 to
with null output or target output being produces. In an
embodiment with reference to FIG. 9, keyway aperture 208
has a round shape with bevel angle 234 of 90° and is made
from machined stainless steel. In an embodiment with
reference to FIG. 32, a plurality of receiver pads 238
provides a plurality of aperture caps 206 such that the
number of aperture caps 206 is equal to the number of
receiver pads 238,

[0053] Aspects of tolerance, e.g., radial tolerance, rota-
tional tolerance, and the like of key 236 with respect to
aperture cap 206 and housing 204 are shown in FIG. 13 and
FIG. 14. It is contemplated that a safety factor SF (e.g.,
SF=F fai/F gino» Wherein F,,,,i8 a failure limit, and F,,,, is an
allowable limit such that if a radial tolerance is 100 cm+/-1
cm, SF=50) with respect to tolerance of key 236 to keyway
aperture 208 can be from 0.5 TO 10000 or an intermediate
value thereof or a value selected for a particular technologi-
cal application for determining an accuracy of disposal of
key 236 into keyway aperture 208. In this regard, the
tolerance can include a radial tolerance, rotational tolerance,
angular tolerance, or a combination thereof.

[0054] With reference to FIG. 15 and FIG. 16, position
verification sensor 200 produces discrete output 210 as a
function of contact between key 236 with aperture cap 206
or receiver pad 238. With key 236 not in contact with
position verification sensor 200, aperture cap 206 is in
primary position 218 so that position verification sensor 200
has null state 224 and produces null output 228 as discrete
output 210. It is contemplated that discrete output 210 can
be an electrical response where a change in signal indicates
achange from a null output to a target output; a mechanical
response where a mechanical motion, physical connection,
or lack thereof indicate a change from a null output to a
target output; or an optical response resultant from the
presence of key 236 encapsulated or through keyway aper-
ture 238. Exemplary discrete outputs 210 include an elec-
trical signal, mechanical response, optical signal, or a com-
bination thereof. The electrical signal can be a selected
voltage or current. The mechanical response can be a
movement or positioning of a physical member. The optical
signal can be a change in signal measured, e.g., from an
optical device. Further, null output 228 can include an
absence or presence of an electrical signal, mechanical
response, or optical signal. When key 236 is communicated
through keyway aperture 208 and contacts receiver pad 238,
aperture cap 206 can remain in primary position 218 with
position verification sensor 200 transitioning from null state
224 to target state 226 so that position verification sensor
200 produces target output 230 as discrete output 210.
Further, target output 230 can include an electrical signal,
mechanical response, and optical signal. When key 236
moves out of contact from receiver pad 238 or aperture cap
206, position verification sensor 200 is in null state 224 with
discrete output 210 being null output 228. When key 236
contacts cap surface 207 and depresses aperture cap 206 by
depression force 212, aperture cap 206 moves and com-
presses compliant member 214 so that position verification
sensor 200 maintains null state 224 with null output 228.
[0055] For nested or stacked receiver pads 238, e.g., as
shown in FIG. 7 with reference to FIG. 16, a plurality of
depressed positions (220.1, 220.2, and the like) or primary


Patent Application Publication Mar. 19, 2020 Sheet 25 of 33. US 2020/0086501 Al

{a} Link 1 Inspection

: RHS 2 TESTED and SUCCEEDS ‘
‘

' Link 1 to Link 2 Interface Confirmed Nominal |
' Link 2 Confirmed Nominal '

wane nee x.
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Figure 25


US 2020/0086501 Al

Mar. 19, 2020 Sheet 1 of 33

Patent Application Publication

Figure 1


Patent Application Publication

Output voltage

Vi4

VO4

2044

24-4

238~L ~

Mar. 19, 2020 Sheet 33 of 33

236

US 2020/0086501 Al

202

Receiver Pad Depth

Figure 33


US 2020/0086501 Al

choose relevant inspection points to meet monitoring objec-
tives. To develop this representation, a suggested starting
point is to document the chain at the component level while
identifying the relationships between components through
their interfaces.

[0087] The kinematic chain is made of links which can be
connected to other links or a reference frame. Each compo-
nent or element of the system is considered a link in the
kinematic chain. Each link has a left-hand side (LHS) and a
right-hand side (RHS) which correspond to that compo-
nent’s interfaces with other links in the chain. It is important
to note that LHS and RHS elements are physical pieces of
the link, itself. For example, if a robot is a link, the LHS
would likely be the robot’s base since that would be physi-
cally connected to a mounting surface and the RHS would
likely be the robot's tool flange since this is where an end
effector would be joined. At the LHS and RHS boundaries
of each link, permanent connections are represented by
brackets ‘[,]’ and intermittent connections with parenthesis
*()’. For example, a gripper, which is permanently fixed to
a robot tool flange, will have a ‘[’ on its LHS corresponding
to the permanent connection to a robot and a ‘)’ on its RHS
corresponding to an intermittent connection to a part as
shown in FIG, 20.

[0088] When individual links are joined to form a kine-
matic chain, the physical interfaces, represented by the LHS
and RHS of adjacent links and the type of connection
(permanent or intermittent), are identifiable as seen in FIG.

21. A reference frame exists at a boundary at either the far
left or far right (or both) of the chain to provide a basis of
measurement. Using this convention also allows for the
kinematic chain to be represented in text. A single link can
be represented as [LHS, Link, RHS] or more simply [Link]

For example, the chain in FIG. 21(@) can be represented as
*Reference] [LHS 1, Link 1, RHS 1] [LHS 2, Link 2, RHS
2) or in a simpler form ‘Reference] [Link 1] [Link 2).’

[0089] A variety of components are typically chosen by a
machine integrator for specific tasks during industrial robot
work cell design and integration. This variety can pose a
challenge in expressing the range of possible configurations.
A robotic work cell can include an industrial robot arm and
an end effector. These components will serve as the starting
point of the kinematic chain as shown in FIG. 21(6). Not all
kinematic chains remain intact throughout the entirety of a
manufacturing process. In use cases where there are mul-
tiple, swappable end effectors, multiple chains will exist
throughout the overall process. Likewise, an end effector
may perform two or more functions. Each function will
generate a unique kinematic chain which includes the inter-
actions that are specific to those functions. Additional chains
will need to be documented and analyzed in these scenarios.

[0090] Beyond the robot arm and end effector, additional
work cell components are considered part of the kinematic
chain if they impact the positional accuracy of any compo-
nent or action within the process. These components include
elements that are not actuated or actively controlled yet are
critical in the relative positioning of parts and equipment
during operation. For example, a hard stop may be used to
orient a part. If the hard stop is not properly positioned, the
part will not be oriented properly when aligned with the
stop. Therefore, the hard stop should be included in the
kinematic chain. Additional components can also include
parts being worked on and the fixturing that is holding them.

Mar. 19, 2020

[0091] A material handling robot and a path-following
robot was a platform to support robotic work cell PHM
research. The use case begins with the material handling
robot, with a gripper end effector, picking parts from an
input, and placing them on a work fixture (FIG. 22(a)). The
path following robot, with a pen holding end effector, then
draws on the part (FIG. 22(6)). Once the drawing operation
is complete, the part is then picked by the material handling
robot and placed in an output location (FIG. 22(c)).
[0092] As seen in FIG. 23, for this use case, the world
frame is the reference frame and is set by the table which the
robot and fixtures are rigidly mounted on. The robot is the
first link, followed by the gripper, then the part, and finally
the fixture. The critical relationships in this kinematic con-
figuration include the robot base to a table—a permanent
connection shown in FIG. 24(a), the robot tool flange to the
gripper mounting—a permanent connection shown in FIG.
24(b), the gripper fingers to the part—an intermittent con-
nection shown in FIG. 24(c), the part to the fixture—another
intermittent connection, and the fixture to the table—a
permanent connection highlighted in FIG. 24(d).

[0093] When the robot is in position to pick or place a part,
there is a constrained relationship between the part and the
gripper, as well as the part and the fixture. The robot must
position the gripper in a designed relationship to the fixture
(and part) during part pick and placement because of these
physical constraints. The interfaces of the intermittent con-
nection between the gripper and part are shown as the RHS
of the gripper (gripper fingers) and the LHS of the part (part
geometry) respectively. Likewise, interfaces of the intermit-
tent connection between the part and the fixture are shown
as the geometries of the part and the fixture.

[0094] With regard to inspecting the kinematic chain to
identify degradation, identifying and tracking degradation of
work cell components includes measuring positioning
repeatability of key points along kinematic chains. By
inspecting the positioning repeatability of individual com-
ponents relative to a reference frame, components which
have degraded in their ability to position repeatedly beyond
a design limit can be identified. The position verification
sensor included treating kinematic chains as open loop
chains due to the nature of serial manipulators. There may be
work cell configurations where the kinematic chain is rep-
resented as a closed loop, as in the use case, but by
inspecting individual points along the chain. This does not
pose an issue. In cases where the chain is a closed loop,
which is typically due to multiple components interfacing
directly with the same reference frame as the robot, inspec-
tions may need to be carried out working from both the LHS
and RHS reference frames.

[0095] Inspection of components starts at a reference
frame. The measurement sensor(s) is in a known location to
the reference frame and is assumed to be positioned and
operating properly. Working left-to-right in the kinematic
chain, the sensor(s) is fixed in the left most reference frame.
Inspection begins at the RHS of the first component (link)
with the testing of the position of the RHS of the component
at a taught position. This assesses if the first component is
maintaining sufficient repeatability to succeed. If the test is
successful, then all parts of the first link are being positioned
nominally. This is represented in FIG. 25(a). After the first
component is tested to be within specification the process
continues, from left to right, by inspecting each component
to confirm that each link is achieving its nominal test


Patent Application Publication Mar. 19, 2020 Sheet 28 of 33. US 2020/0086501 Al

209

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Figure 28


Patent Application Publication Mar. 19, 2020 Sheet 12 of 33. US 2020/0086501 Al

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