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Claims  |
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What is claimed is:
1. A system for use in sensing the relative angular orientation of at least
two movable adjacent skeletal link segments of a living body joined
together at a joint, said system comprising:
first and second links coupled together about a first pivot axis so that
said links are pivotable relative to one another about said axis so as to
define a variable angle between said links about said first pivot axis;
securing means for securing said first and second links relative to said
skeletal link segments so that said links pivot about said first pivot
axis when said skeletal link segments pivot about said joint, wherein said
securing means includes an attachment assembly for attaching said links to
each of said skeletal link segments so that said links pivot relative to
said attachment assembly about two degrees of freedom and follow the
relative angular movement of the skeletal link segments with reduced
artifacts due to motion between said attachment assembly and said skeletal
link segments; and
sensor means for sensing said angle between said skeletal link segments.
2. A system according to claim 1, wherein said attachment assembly includes
means for attaching said link so that said link is pivotable about second
and third, mutually perpendicular pivot axes relative to said attachment
assembly with reduced artifacts due to motion between said attachment
assembly and said skeletal link segments.
3. A system according to claim 1, wherein said sensor means includes a Hall
effect sensor.
4. A system according to claim 1, wherein said attachment assembly includes
means for accommodating changes in the cross-section of each skeletal link
segment as the adjacent skeletal link segments are bent about the joint,
while preventing relative movement between said skeletal link segments and
said attachment assembly so as to substantially reduce artifacts due to
motion between said attachment assembly and said skeletal link segments.
5. A system according to claim 1, further including means for correlating
the angle sensed by said sensor means with said angular orientation made
by said adjacent skeletal link segments.
6. A system according to claim 1, wherein said means for securing said
first and second links secures said links so that said first pivot axis is
displaced from and substantially parallel to the pivot axis of said joint.
7. A system according to claim 5, wherein said links are adapted to be
positioned so that said first pivot axis is above the pivot axis of said
joint.
8. A system according to claim 5, wherein said means for correlating said
angle between said links with the angle made by said skeletal link
segments includes means comprising a lookup table containing the
correlation between said angle between said links, and the angle between
said skeletal link segments.
9. A system according to claim 5, wherein said means for correlating said
angle between said links with the angle made by said skeletal link
segments includes means containing a set of simultaneous equations for
determining the correlation between said angle between said links and the
angular orientation made by said skeletal link segments.
10. A system for use in sensing the relative angular orientation of the
fingers and thumb of a hand, said system comprising:
(A) an exoskeletal unit adapted to be secured to said hand, said
exoskeletal unit comprising:
(a) a plurality of pairs of links, each pair for use with a corresponding
joint of the fingers and thumb, the links of each pair being coupled
together so that said links of each pair are pivotable relative to one
another about a first pivot axis so as to define a variable angle between
said links of said pair about said axis;
(b) securing means for securing said pairs of links to said hand so that
each pair of links is secured relative to the adjacent skeletal link
segments of the fingers and thumb of said hand joined at the corresponding
joint with which said pair of links is used so that said pair of links
pivot about said pivot axis when said adjacent skeletal link segments
pivot about said joint, wherein said securing means includes an attachment
assembly for attaching said links to each of said skeletal link segments
so that said links pivot relative to said attachment assembly about two
degrees of freedom and follow the relative angular movement of the
skeletal link segments with reduced artifacts due to motion between said
attachment assembly and said skeletal link segments; and
(c) sensor means, secured to each pair of links, for sensing said angle
between said links; and
(B) means for correlating the angle sensed by said sensor means with the
angle made by the corresponding adjacent skeletal link segments.
11. A system according to claim 10, wherein said sensor means includes a
Hall effect sensor.
12. A system according to claim 10, wherein said means for correlating said
angle sensed by said sensor means with the angle made by said skeletal
link segments includes means comprising a lookup table containing the
correlation between said angle sensed by said sensor and the angle made by
said corresponding adjacent skeletal link segments.
13. A system according to claim 10, further including means for sensing the
relative angular position of each of said fingers and thumb relative to
one another.
14. A system according to claim 10, wherein said securing means includes a
plurality of attachment assemblies for attachment to corresponding ones of
said skeletal link segments, wherein each of said attachment assemblies
includes means for accommodating changes in the cross-section of each
skeletal link segment as the adjacent segments are bent about the joint,
while preventing relative movement between said skeletal link segments and
said attachment assembly so as to reduce artifacts due to motion between
said attachment assembly and said skeletal link segments.
15. A system for use in sensing the relative angular orientation of two
movable adjacent skeletal link segments of a living body joined together
at a joint, said system comprising:
first and second links;
attachment assembly means for coupling said links relative to said adjacent
skeletal link segments so that said links are movable relative to one
another as said skeletal link segments move relative to one another as
said skeletal link segments move relative to one another wherein said
attachment assembly means cooperates with said links and said adjacent
skeletal link segments so that artifacts due to motion between said
attachment assembly means and said skeletal link segments are reduced;
signal generating means, responsive to the relative position of said links,
for generating a sensor signal representative of the relative angular
orientation of said links;
means for storing data regarding the physical features of said skeletal
link segments; and
means for generating a finger angle signal representing the angular
orientation of said joint as a function of said sensor signal and said
stored data.
16. In a system for use in sensing the relative angular orientation of two
movable adjacent skeletal link segments of a living body joined together
at a joint, said system comprising: (a) first and second links coupled
together about a pivot axis so that said links are pivotable relative to
one another about said axis so as to define a variable angle between said
links about said axis; (b) securing means for securing said links with
respect to said skeletal link segments so that said links pivot about said
pivot axis when said skeletal link segments pivot about said joint; (c)
sensor means, secured to said first and second links, for sensing said
angle between said segments; and (d) means for correlating the angle
sensed by said sensor means with said angular orientation made by said
skeletal link segments; wherein the improvement comprises:
said securing means including an attachment assembly for securing said each
of said links relative to the corresponding skeletal link segment, each
said attachment assembly including means for accommodating changes in the
cross-section of said corresponding skeletal link segment as the skeletal
link segments are bent about the joint, while preventing relative movement
between said one skeletal link segment and said attachment assembly.
17. The system according to claim 16, wherein each said attachment assembly
includes (a) an attachment base, (b) a post fixed to said base, (c) a
strap mount slidably mounted on said post relative to said base, (d) means
for biasing said strap mount away from said base, and (e) a strap, secured
to said strap mount and adapted to be secured around said one skeletal
link segment, for securing said assembly to the corresponding skeletal
link segment, wherein said mount and base move relative to one another as
the cross-section of said corresponding skeletal link segment varies.
18. The system according to claim 16, wherein said base includes a groove
shaped to engage the surface of said corresponding skeletal link segment.
19. The system according to claim 18, wherein said groove is V-shaped.
20. In a system for use in sensing the relative angular orientation of two
movable adjacent skeletal link segments of a living body joined together
at a joint, said system comprising: (a) first and second links coupled
together about a pivot axis so that said links are pivotable relative to
one another about said axis so as to define a variable angle between said
links about said axis; (b) securing means for securing said links with
respect to said skeletal link segments so that said links pivot about said
pivot axis when said skeletal link segments pivot about said joint; (c)
sensor means, secured to said first and second links, for sensing said
angle between said segments; and (d) means for correlating the angle
sensed by said sensor means with said angular orientation made by said
skeletal link segments; wherein the improvement comprises:
said securing means including an attachment assembly for securing each of
said links relative to a corresponding one of said skeletal link segments,
each said attachment assembly including means for pivotally attaching a
corresponding link to said attachment assembly relative to two degrees of
freedom so as to reduce artifacts due to motion between said link and said
corresponding one of said skeletal link segments.
21. In a system for use in sensing the relative angular orientation of the
skeletal link segments forming the proximal and distal joints of the thumb
of a hand, said system comprising:
first, second, third and fourth links coupled together so that (a) said
first and second links are pivotal relative to one another about a first
axis so as to define a first variable angle, (b) said second and third
links are pivotal relative to one another about a second axis, and (c)
said third and fourth links are pivotal relative to one another about a
third axis so as to define a second variable angle;
means for securing said firs, second, third and fourth links with respect
to said skeletal link segments so that said links pivot about said pivot
axes when said skeletal link segments pivot about said joints;
sensor means, secured to said first and second links and to said third and
fourth links, for sensing said first and second variable angles; and
means for correlating the angles sensed by said sensor means with said
angular orientation made by said skeletal link segments.
22. The system according to claim 21, wherein said means for securing said
first, second, third and fourth link segments includes means for securing
said first and fourth link segments relative to said hand. |
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Claims |
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Description |
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The present invention relates generally to a system for measuring the
relative angular orientation of two relatively movable skeletal links or
segments of a living body joined together at a joint, and more
specifically to an improved, input device for generating signals
representative of the relative angles of the finger and thumb links of the
hand.
Devices and systems are well known for measuring or monitoring one or more
characteristics of an anatomical part (see for example, U.S. Pat. Nos.
3,258,007 and 3,364,929), and specifically, a human joint (see, for
example, U.S. Pat. Nos. 1,590,499; 3,717,857; 3,786,458; 4,037,480;
4,046,262; 4,436,099; 4,444,205; and 4,667,685). A human controlled
position sensing device for use in the field of robotics is also well
known (see, for example, U.S. Pat. Nos. 4,328,621; 4,534,694; 4,608,525;
and 4,674,048).
The present invention generally relates to such a system and is
specifically adapted to have at least two applications. The system is
useful in measuring the angle between two skeletal links so that the
system can be used to measure joint range of motion. It is also useful in
generating electrical signals representative of various positions of an
anatomical part, most notably the hand, so that the positions can be
replicated for control of a robot.
At least two systems, adapted to be worn on the operator's hand for
generating electrical signals representative of hand position, recently
have been proposed. Generally, each of these systems includes a plurality
of sensors for sensing movements of various parts of the hand. The outputs
of the sensors are used to provide various electrical signals
representative of the position of various parts of the hand. For example,
one such system, which is currently commercially available, is the
DATAGLOVE MODEL 2 SYSTEM sold by VPL Research Inc. of Redwood City, CA.
This system includes various sensors secured to a glove. The user wears
the glove so that as he or she moves each finger and thumb, the sensors
generate signals representative of the hand gestures. While the glove
provides limited stretching to conform to the size and shape of the user's
hand, the sensed movements may not be very accurate. The sensors are
secured to the glove so that movement between the hand and glove (and thus
the sensors) will create motion artifacts and thus errors in the signals
generated by the sensors. Such motion artifacts tend to occur during
normal motions of the hand for two reasons. Firstly, the glove does not
securely affix the sensors to the hand due to fit problems. Secondly, the
fingers and thumb actually may change shape (i.e., each segment may change
in its cross-sectional dimension) as the fingers and thumb are moved.
An exoskeletal sensor unit has been developed by Sarcos, Inc. of Salt Lake
City, UT. The Sarcos unit utilizes links secured to the segments of each
finger and thumb. A pair of links are rigidly secured to adjacent finger
segments forming each joint (including each knuckle). Each pair of links
are joined about a pivot axis, above the finger joint so that the two
links pivot when the finger segments are pivoted about the finger joint. A
potentiometer is used at the pivot axis for sensing relative angular
movement between the links and for generating a signal representative of
the angle between the two links (in a similar manner to the devices shown
in U.S. Pat. Nos. 3,258,007; 4,046,262; 4,667,685). The signal is applied
directly to a robotic hand for controlling the angular orientation of
corresponding joint segments of the robotic hand.
While this prior art system helps reduce motion artifacts inherent in the
glove type system, this exoskeletal sensor system cannot provide accurate
measurements and/or control signals. The angle sensed by the potentiometer
is a function of both the angular movement of the particular joint to
which the corresponding links are attached, the geometry and dimensions of
the links and hand, and the manner in which the sensor unit is attached to
the hand. Additionally, the exoskeletal unit is bulky and difficult to
wear. The individual links are rigidly secured to the finger and thumb
segments so that the construction assumes each finger and thumb is
straight and that, when bent, the pivot axes of all the joints remain
parallel throughout the range of motion. Neither assumption is usually
correct since the long axis of a person's finger can be and is often bent
so that the finger may twist as it bends causing the axes of the various
finger joints to move in a non-parallel fashion. Further, under such
circumstance, with the exoskeleton unit being secured to solid blocks
which are not contoured to adapt to different finger sizes and each block
being secured with an elastic band to the fingers and thumb of the hand,
as the fingers and thumb are bent, motion artifacts are introduced because
of relative movement between the hand and the exoskeletal unit attributed
to stretching of the elastic strap in different directions and rocking of
the block on the finger as a result of the hand movement.
Accordingly, it is a general object of the present invention to provide an
improved system for measuring the angular orientation at a movable joint
of a living body, which unit substantially reduces or overcomes the
foregoing problems.
A more specific object of the present invention is to provide an improved
system for measuring the angular orientation at a movable joint of a
living body with improved accuracy and greater resolution, while
minimizing errors attributed to motion artifacts.
Another specific object of the present invention is to provide an improved
system for measuring the relative angle between a pair of links secured to
joint segments forming a movable joint of a living body, and correlating
the measurement with the geometry of the mechanical system and the
particular joint to which the links are used.
And another specific object of the present invention is to provide an
improved system for measuring movement of the fingers of a hand and
adapted to calibrate the angular measurements made by the system with the
corresponding angular measurements of the joints of the fingers.
Yet another object of the present invention is to provide an improved
exoskeletal system for sensing the angular movement of the fingers, the
unit being light weight, comfortable to wear and adapted to conform to any
size hand and various finger movements.
These and other objects of the present invention are achieved by an
improved system for sensing the relative angular orientation of two
movable adjacent joint link segments of a living body joined together at a
joint. The system comprises:
first and second links coupled together about a pivot axis so that said
link segments are pivotable relative to one another about said axis so as
to define a variable angle between said segments about said axis;
means for securing said first and second link segments respectively to said
joint segments so that said link segments pivot about said pivot axis when
said joint segments pivot about said joint;
sensor means, secured to said first and second link segments, for sensing
said mechanical angle; and
means for correlating the mechanical angle sensed by said sensor means with
the angle made by said joint segments.
Other objects of the invention will in part be obvious and will in part
appear hereinafter. The invention accordingly comprises the apparatus
possessing the construction, combination of elements, and arrangement of
parts which are exemplified in the following detailed disclosure, and the
scope of the application of which will be indicated in the claims.
For a fuller understanding of the nature and objects of the present
invention, reference should be had to the following detailed description
taken in connection with the accompanying drawings wherein:
FIG. 1 is a block diagram of the preferred computerized system for
obtaining and storing relative finger and thumb positions and movement of
an operator's hand;
FIG. 2 is a perspective view of the preferred exoskeletal unit designed for
use and shown on a human hand;
FIG. 3 is a side view of the portion of the exoskeletal unit of FIG. 2
attached to a finger;
FIG. 4 is a top view of the portion of the exoskeletal unit of FIG. 2
attached to a finger;
FIG. 5 is a side view, with a portion cut away, of one finger base assembly
of the exoskeletal unit of FIG. 2;
FIG. 6 is a cross-sectional view taken along line 6--6 of FIG. 5;
FIG. 7 is a top view of the finger base assembly of FIG. 5;
FIG. 8 is a cross-sectional view taken along line 8--8 of FIG. 5;
FIG. 9 is a cross-sectional view taken along line 9--9 of FIG. 4;
FIG. 10 is a cross-sectional view taken along line 10--10 of FIG. 3;
FIG. 11 is a cross-sectional view taken along line 11--11 of FIG. 9; and
FIG. 12 is a block diagram of the flow chart of the control processor unit
of FIG. 1.
The same numerals are used throughout the drawings to designate the same or
similar parts.
Referring to FIG. 1 the block diagram generally shows the preferred system
including the exoskeletal unit 20, the latter being adapted to be
supported on the operator's hand. The exoskeletal unit 20 preferably
includes a plurality of sensors, one for each joint of the fingers of a
hand for measuring the angle of each joint. Sensors are also provided for
measuring the angle between any two fingers or between the index finger
and thumb. Each sensor is used to provide an extremely accurate, high
resolution output signal instantaneously representative of the actual
relative angle of the corresponding finger or finger joint of the hand at
any one instant of time.
All of the sensor outputs are transmitted to a control processor unit (CPU)
22 for processing the signals. As will more evident hereinafter, one
function of the CPU 22 is to generate look up tables during an initial
calibration procedure so that the angle sensed by each sensor (e.g., angle
B in FIG. 3) can be quickly and accurately correlated with the actual
angle of the corresponding joint or finger with which the sensor is being
used (e.g., angle A in FIG. 3). Accordingly, memory 24 of suitable size is
provided so as to store all of the calibration data generated during the
initial calibration procedure.
Following the initial calibration procedure the output of the CPU 22 can be
suitably connected to a display 26 for displaying data, and/or to a
controlled unit 28, e.g., a robotic hand, whereby the exoskeletal unit 20
can be used to remotely control the controlled unit. It can also be
connected to memory 24 to store the sensor signals which can be used as a
measurement of the range of motion of the various joints of the fingers
and thumb.
The preferred exoskeletal unit 20 is shown in FIG. 2, with details being
shown in FIGS. 3-11. Unit 20 includes a hand clip 40 including a plate 42
and a spring clip (shown in phantom at 44). A button 46 secured to the end
of the clip 44 is adapted to fit in the palm of the user's hand so that
the clip 40 rests comfortably, yet tightly on the hand. The spring clip 44
is made of spring metal so that the hand clip comfortably fits on the hand
40 as shown, without moving relative to the hand.
A linkage assembly 52 for each finger 32 and thumb 34 is connected to the
clip 40 and is adapted to be secured to the respective finger and thumb.
Each linkage assembly includes two or three attachment assemblies 54, each
adapted to be secured to a finger or thumb segment 36. Each linkage
assembly 52 includes a plurality of links 56 and 57, or 56a and 57a
supported by the clip 40 and attachment assemblies 54 so that a pair of
links form a linkage pair 56 and 57, pivotally supported on opposite sides
of each finger and thumb joint, and pivotally supported with respect to
one another above the corresponding joint. For the thumb, one linkage pair
56a and 57a, with a sensor at each end to measure the angular displacement
of each link independently, is interconnected by a passive pivot 97 with
respect to the middle thumb joint (indicated at 38) and the proximal joint
(indicated at 39) since an attachment assembly cannot be easily secured to
the skeletal link provided between these two joints. The two sensors
provide sufficient information to calculate the angles of the middle and
proximal thumb joints even though no attachment is made to the segment
connecting them. For the other joints means, coupled to each pair of
links, are provided for sensing the relative angle between the two links,
as will be more evident hereinafter, so that measurements can be made of
the angles formed at the distal, middle and proximal joints of each finger
and the distal joints of the thumb.
Referring to FIGS. 5-8 each attachment assembly 54 includes an attachment
base 58, a strap post 60, a strap mount 62 and at least one pivot post 64
(the assembly 54 adapted to be secured to the distal end segment of each
finger and thumb is provided with one pivot post, while the other
assemblies are provided with two posts). As shown in FIGS. 6 and 8, the
bottom of attachment base 58 is formed with a groove 66 of triangular
cross-section adapted to align with and receive the portion of the finger
or thumb segment to which the base member is secured. The triangular
cross-section provides a stable base which accommodates fingers of
different sizes thereby avoiding the problems of earlier designs. The
attachment base also includes a side groove 68 (see FIGS. 5, 7 and 8)
formed on each side of the attachment base. An aperture is formed in the
center of the base member from the top surface to the bottom groove 66 for
receiving the strap post 60 (see FIG. 8). Preferably, the post 60 is
maintained in place by snap rings 78 adapted to fit into grooves provided
at both ends of the post.
The strap mount 62 is a U-shaped bracket including intermediate portion 74
formed with a hole. The hole is large enough to freely receive the shaft
of the strap post 60 but smaller than the snap ring 78 so that the mount
will be retained by the snap ring when the mount is positioned on the base
assembly. The side portions 80 of the strap mount 62 are adapted to fit
within the side grooves 68 so that the mount is slidable in a vertical
direction between the two pivot posts 64. Suitable bias means, preferably
in the form of a compression spring 82 (see FIG. 8), biases the strap
mount from the attachment base 58. This mounting accommodates changes in
finger diameters as they are flexed by allowing motion in one direction
only thereby providing a significantly more stable mounting than provided
by an elastic strap which can stretch in any direction. The side portions
80 of the strap mount 62, each includes a slot 86 for receiving a strap
88. The strap 88 is sufficiently long and is provided with suitable
fastening means, such as the material manufactured under the trademark
VELCRO, so that the strap can be secured through one slot, tightly wrapped
around the finger or thumb segment, threaded through the other slot, and
secured to itself so as to maintain the attachment assembly 54 in a secure
and stable position on the finger or thumb segment.
The two pivot posts 64 are secured in the attachment base 58 on opposite
sides of the strap mount 62 so that the vertical axes 90 of the posts are
substantially parallel to one another (see FIG. 6). A cylindrical element
92 is pivotally mounted on each post 64 so as to pivot about the
corresponding axis 90, while being suitably restrained from axial movement
with a snap ring 78. Each cylindrical element 92 includes a shaft portion
94 so that the axis 96 of the shaft portion is perpendicular to the
vertical axis 90 of the corresponding post to which the cylindrical
element is pivotally secured. One end of a link 56 or 57 is secured to the
shaft portion 94 so that the link can pivot about the axis 96 and pivot
with the cylindrical element 92 about the axis 90.
All of the parts for the base assembly and links are preferably made of a
non-magnetic material, such as anodized aluminum, non-magnetic stainless
steel and plastic.
As shown in FIGS. 2-4, the attachment assemblies 54 on the distal ends of
the thumb and fingers include only a single pivot post 64 with an
identical cylindrical element and pivot pin 94 so that the link connected
to the attachment assembly pivots about a corresponding axis 90 and 96.
Referring to FIG. 2, the linkage used to measure the angle of the middle
joint 38 and proximal joint 39 of the thumb includes two linkage pairs
secured about a passive pivot 97 since the unit cannot be easily secured
to the skeletal link segment of the hand between the middle and proximal
joints 38 and 39. One linkage pair is accordingly secured to the
attachment assembly 54 attached between the distal thumb joint and middle
thumb joint 38, while the other linkage pair is secured to an assembly 110
(described in greater detail hereinafter), which in turn is adjustably
secured to the support rod 55 so that the assembly can be properly
positioned relative to the proximal joint 39. Rod 55 is in turn secured to
the plate 42 of the clip 40 by any suitable means such as bolt and wing
nut 59. As shown in FIGS. 4 and 9, each linkage pair, formed by the links
56 and 57, is pivotally secured together about a pivot axis 100 by any
suitable means (such as bearing elements 101, 103 and cap 105 as shown
best in FIG. 9). Each linkage pair is provided with magnetic means
preferably in the form of two magnets 102a and 102b secured at the end of
the link 56, and a Hall effect sensor 104, secured the link 57, for
accurately detecting the relative angular position of the two links about
the pivot axis 100. Each sensor is provided with output leads 106. As is
well known, the sensor will generate an electrical signal as a function of
the strength of the magnetic field sensed by the sensor. As best shown in
FIGS. 9 and 11, the two magnets are "horseshoe" in shape and are
positioned in link 56 on opposite sides of the pivot axis 100. The magnets
are identical to one another with the poles of the magnets being axially
spaced from one another, except that the polarity orientation of one
magnet is the opposite of the polarity orientation of the other magnet so
that the sensor is disposed a predetermined distance from the south pole
of one magnet and the north pole of the other magnet. The magnet
assemblies are custom made and purchased from Sarcos, Inc. of Salt Lake,
UT. The magnets are shaped so that the magnetic field sensed by the Hall
effect sensor 104 varies 360.degree. around the pivot axis. Thus, the
amplitude of the output signal of sensor 104 will vary as a function of
the relative angular orientation of the two links. Sensors manufactured by
the Microswitch division of Honeywell Corporation under model SS9 Series
may be used. Such sensors when used with the magnets 102a and 102b will
provide a substantially linear output signal as a function of angle over a
180.degree. range with +/-0.1.d | | |
