U.S. patent application number 11/881964 was filed with the patent office on 2008-02-21 for instrumented prosthetic foot.
Invention is credited to Stephane Bedard, Pierre-Olivier Roy.
Application Number | 20080046096 11/881964 |
Document ID | / |
Family ID | 34574330 |
Filed Date | 2008-02-21 |
United States Patent
Application |
20080046096 |
Kind Code |
A1 |
Bedard; Stephane ; et
al. |
February 21, 2008 |
Instrumented prosthetic foot
Abstract
The present invention discloses an instrumented prosthetic foot
for use with an actuated leg prosthesis controlled by a controller,
the instrumented prosthetic foot comprising a connector to connect
the instrumented prosthetic foot to the leg prosthesis, an ankle
structure connected to the connector, a ground engaging member
connected to the ankle, at least one sensor for detecting changes
in weight distribution along the foot, and an interface for
transmitting signals from the sensor to the controller.
Inventors: |
Bedard; Stephane;
(Saint-Augustin-de-Desmaures, CA) ; Roy;
Pierre-Olivier; (US) |
Correspondence
Address: |
SEYFARTH SHAW LLP
131 S. DEARBORN ST., SUITE2400
CHICAGO
IL
60603-5803
US
|
Family ID: |
34574330 |
Appl. No.: |
11/881964 |
Filed: |
July 31, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10715989 |
Nov 18, 2003 |
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11881964 |
Jul 31, 2007 |
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Current U.S.
Class: |
623/53 ; 600/553;
623/52 |
Current CPC
Class: |
A61F 2/66 20130101; A61F
2/72 20130101; A61F 2002/764 20130101; A61F 2/70 20130101; A61F
2002/5001 20130101; A61F 2002/6621 20130101; A61F 2002/6642
20130101; A61F 2002/5007 20130101; A61F 2002/7685 20130101; A61F
2002/7635 20130101; A61F 2002/5003 20130101; A61F 2002/6685
20130101; A61F 2002/665 20130101; A61F 2002/705 20130101 |
Class at
Publication: |
623/053 ;
600/553; 623/052 |
International
Class: |
A61F 2/68 20060101
A61F002/68; A61B 19/00 20060101 A61B019/00 |
Claims
1. An instrumented prosthetic foot for use with an actuated leg
prosthesis controlled by a controller, the instrumented prosthetic
foot comprising: an elongated body comprising a foot plate and a
heel plate being cantilevered from the foot plate, the foot plate
comprising a toe region thereof; a connector to connect the
instrumented prosthetic foot to the leg prosthesis, the connector
being mounted on the elongated body; and a pair of first and second
sensors mounted on the elongated body, the first sensor being
positioned at the underside of the heel plate and the second sensor
being positioned at the underside of the foot plate at the toe
region; wherein the pair of first and second sensors is configured
to detect changes in weight distribution along the prosthetic
foot.
2. An instrumented prosthetic foot according to claim 1, wherein
the first and second sensor include a strain sensor.
3. An instrumented prosthetic foot according to claim 1, wherein
the first and second sensor include a pressure sensor.
4. An instrumented prosthetic foot according to claim 3, wherein
the pressure sensor is a force-sensing resistor.
5. An instrumented prosthetic foot according to claim 1, further
comprising a rigid plate placed on at least one side of the first
and second sensor.
6. An instrumented prosthetic foot according to claim 1, wherein
the first and second sensor are sandwiched between respective first
and second pairs of rigid plates.
7. An instrumented prosthetic foot according to claim 6, wherein
the first pair of rigid plates is interposed between a first
resilient pad and the heel plate and the second pair of rigid
plates is interposed between a second resilient pad and the foot
plate.
8. An instrumented prosthetic foot according to claim 1, wherein
the first and second sensor transmit signals to the controller
using a wired connection.
9. An instrumented prosthetic foot according to claim 1, wherein
the first and second sensor transmit signals to the controller
using a wireless connection.
10. An instrumented prosthetic foot according to claim 1, wherein
the first and second sensor transmit signals to the controller
using an optical interface.
11. An instrumented prosthetic foot according to claim 1, wherein
the connector removably connects the instrumented prosthetic foot
to the leg prosthesis.
12. An instrumented prosthetic foot for use with an actuated leg
prosthesis controlled by a controller, the instrumented prosthetic
foot comprising: an elongated body comprising a foot plate and a
heel plate being cantilevered from the foot plate; a connector to
connect the instrumented prosthetic foot to the leg prosthesis, the
connector being mounted on the elongated body; and a pair of first
and second sensors mounted on the elongated body, the first sensor
being positioned between the connector and the elongated body, the
second sensor being positioned at the foot plate; wherein the pair
of first and second sensors is configured to detect changes in
weight distribution along the prosthetic foot.
13. An instrumented prosthetic foot according to claim 12, wherein
the second sensor is positioned at a junction of the heel plate and
the foot plate
14. An instrumented prosthetic foot according to claim 12, wherein
the first and second sensor include a strain sensor.
15. An instrumented prosthetic foot according to claim 12, wherein
the first and second sensor include a pressure sensor.
16. An instrumented prosthetic foot according to claim 15, wherein
the pressure sensor is a force-sensing resistor.
17. An instrumented prosthetic foot according to claim 12, further
comprising a rigid plate placed on at least one side of the first
and second sensor.
18. An instrumented prosthetic foot according to claim 12, wherein
the first and second sensor are sandwiched between respective first
and second pairs of rigid plates.
19. An instrumented prosthetic foot according to claim 12, wherein
the first and second sensor transmit signals to the controller
using a wired connection.
20. An instrumented prosthetic foot according to claim 12, wherein
the first and second sensor transmit signals to the controller
using a wireless connection.
21. An instrumented prosthetic foot according to claim 12, wherein
the first and second sensor transmit signals to the controller
using an optical interface.
22. An instrumented prosthetic foot according to claim 12, wherein
the connector removably connects the instrumented prosthetic foot
to the leg prosthesis.
Description
TECHNICAL FIELD
[0001] The present invention relates to a prosthetic foot for use
with a control system and/or a method for controlling an actuated
leg prosthesis.
BACKGROUND
[0002] As is well known to control engineers, the automation of
complex mechanical systems is not something easy to achieve. Among
such systems, conventional powered artificial limbs are notorious
for having control problems. These conventional prostheses are
equipped with basic controllers that artificially mobilize the
joints without any interaction from the amputee and are only
capable of generating basic motions. Such basic controllers do not
take into consideration the dynamic conditions of the working
environment, regardless the fact that the prosthesis is required to
generate appropriate control within a practical application. They
are generally lacking in predictive control strategies necessary to
anticipate the artificial limb's response as well as lacking in
adaptive regulation enabling the adjustment of the control
parameters to the dynamics of the prosthesis. Because human limb
mobility is a complex process including voluntary, reflex and
random events at the same time, conventional prostheses do not have
the capability to interact simultaneously with the human body and
the external environment in order to have minimal appropriate
functioning.
[0003] Accordingly, it is an object of the present application to
obviate or mitigate some or all of the above disadvantages.
SUMMARY
[0004] According to the present invention, there is provided an
instrumented prosthetic foot for use with an actuated leg
prosthesis controlled by a controller, the instrumented prosthetic
foot comprising a connector to connect the instrumented prosthetic
foot to the leg prosthesis, an ankle structure connected to the
connector, a ground engaging member connected to the ankle, at
least one sensor for detecting changes in weight distribution along
the foot, and an interface for transmitting signals from the sensor
to the controller.
BRIEF DESCRIPTION OF THE FIGURES
[0005] Embodiments of the invention will be described by way of
example only with reference to the accompanying drawings, in
which:
[0006] FIG. 1 shows the lower body of an individual provided with a
prosthesis and an instrumented prosthetic foot on one side and
having a healthy leg on the other side.
[0007] FIG. 2 is a block diagram showing a control system for a
prosthesis having an actuating mechanism.
[0008] FIG. 3 is a perspective view, from the front and slightly
above, of a instrumented prosthetic foot.
[0009] FIG. 4 is an exploded perspective view of the instrumented
prosthetic foot of FIG. 3.
[0010] FIG. 5 is a perspective view, from the front and slightly
above, of an alternative embodiment of the instrumented prosthetic
foot of FIG. 3.
[0011] FIG. 6 is an exploded perspective view of the instrumented
prosthetic foot of FIG. 5.
[0012] FIG. 7 is a perspective view, from the front and slightly
above, of another alternative embodiment of the instrumented
prosthetic foot of FIG. 3
[0013] FIG. 8 is an exploded perspective view of the instrumented
prosthetic foot of FIG. 7.
[0014] FIG. 9 is schematic view of forces exerted on a foot.
[0015] FIG. 10 is a perspective view, from the front and slightly
above, of a further still alternative embodiment of the
instrumented prosthetic foot of FIG. 3
[0016] FIG. 11 is an exploded perspective view of the instrumented
prosthetic foot of FIG. 10.
[0017] FIG. 12 is a perspective view, from the front and slightly
above, of a yet further still alternative embodiment of the
instrumented prosthetic foot of FIG. 3
[0018] FIG. 13 is an exploded perspective view of the instrumented
prosthetic foot of FIG. 12.
[0019] FIG. 14 is a perspective view, from the front and slightly
above, of a further alternative embodiment of the instrumented
prosthetic foot of FIG. 3
[0020] FIG. 15 is an exploded perspective view of the instrumented
prosthetic foot of FIG. 14.
DETAILED DESCRIPTION
[0021] The appended figures show a instrumented prosthetic foot
(20) having sensors (22A, 22B) for use, in cooperation with
possible additional sensors (24A, 24B, 26), with a control system
(100) for controlling a prosthesis (14) having an actuating
mechanism (16). It should be understood that the present invention
is not limited to the illustrated implementation since various
changes and modifications may be effected herein without departing
from the scope of the appended claims.
[0022] Referring therefore to FIG. 1 an individual (10) has a pair
of legs (26) and (28), one of which, (26), is amputated above the
knee. A prosthesis (14) is attached to the leg (26) and includes an
actuating mechanism (16), which may be either passive or active. An
instrumented prosthetic foot (20) is attached to the prosthesis
(14) and includes sensors (22A, 22B). Additional sensors (24A, 24B)
are located on the healthy foot and additional sensors (26) located
on the individual (10) and/or the prosthesis (14). A passive
actuating mechanism may be generally defined as an
electro-mechanical component that only absorbs mechanical energy in
order to modify dynamics of mechanical joints of the prosthesis,
while an active actuating mechanism may be generally defined as an
electro-mechanical component that absorbs and supplies mechanical
energy in order to set dynamics of mechanical joints of the
prosthesis.
[0023] An example of a passive actuating mechanism is described in
U.S. patent application Ser. No. 09/767,367, filed Jan. 22, 2001,
entitled "ELECTRONICALLY CONTROLLED PROSTHETIC KNEE". Examples of
active actuating mechanisms are described in U.S. patent
application Ser. No. 10/463,495 filed Jun. 17, 2003, entitled
"ACTUATED PROSTHESIS FOR ABOVE-KNEE AMPUTEES", by Stephane Bedard
et al., the entire disclosure of which is hereby incorporated by
reference herein.
[0024] The prosthesis (14) is controlled, as shown schematically in
FIG. 2, by a basic control system (100) comprising sensors (22A,
22B, 24A, 24B, 26), connected through an interface (30) to a
controller (40). The controller (40) provides signals to an
actuating mechanism (16) in the prosthesis (14), such as shown in
FIG. 1. The purpose of the control system (100) is to provide the
required signals for controlling the actuating mechanism (16). To
do so, the control system (100) is interfaced with the amputee (10)
using sensors (22A, 22B, 24A, 24B, 26) to ensure proper
coordination between the amputee (10) and the movements of the
prosthesis (14). The sensors (22A, 22B, 24A, 24B, 26) capture
information, in real time, about the dynamics of the amputee's
movement and provide that information to the controller (40) via
the interface (30). The controller (40) then uses the information
to determine the resistance to be applied to a joint, in the case
of a passive actuating mechanism, or the joint trajectories and the
required angular force or torque that must be applied by a joint,
in the case of an active actuating mechanism, in order to provide
coordinated movements.
[0025] The sensors (22A, 22B, 24A, 24B, 26) may include myoelectric
sensors, neuro-sensors, kinematic sensors, kinetic sensors, strain
gauges or plantar pressure sensors. Myoelectric sensors are
electrodes used to measure the internal or the external
myoelectrical activity of skeletal muscles. Neuro-sensors are
electrodes used to measure the summation of one or more action
potentials of peripheral nerves. Kinematic sensors are used to
measure the position of articulated joints, the mobility speed or
acceleration of lower extremities. Kinetic sensors are used to
measure angular forces at articulated joints or reaction forces of
lower extremities. Strain gages are used to measure the strain
forces at a specific underfoot area. Plantar pressure sensors are
used to measure the vertical plantar pressure of a specific
underfoot area. Of course, additional types of sensors which
provide various information about dynamics of human locomotion may
be used. For a given application, the use of sensors (22A, 22B,
24A, 24B, 26) is not restricted to a specific type of sensor,
multiple types of sensors in various combinations may be used.
[0026] As illustrated in FIG. 1, the sensors (22A, 22B) may
comprise localized plantar pressure sensors located at spaced
locations on the prosthetic foot (20) to measure the vertical
plantar pressure of a specific underfoot area. Similarly, the
plantar pressure sensors (24A, 24B) located on the side of the
healthy foot may be provided at spaced locations in a custom-made
insole, preferably in the form of a standard orthopedic insole,
that is modified to embed the two sensors (24A, 24B) for the
measurement of two localized plantar pressures. The sensors (22A,
22B, 24A, 24B) are operable to measure the weight transfer along
the foot as the individual moves which may be combined with other
sensors (26) such as kinematic sensors to measure the angular speed
of body segments of the lower extremities and kinematic sensors to
measure the angle of the prosthesis (14) knee joint.
[0027] Each sensor (22A, 22B, 24A, 24B) may comprise a thin
Force-Sensing Resistor (FSR) polymer cell directly connected to the
interface (30) of the control system (100) or indirectly using an
intermediary system (not shown), for instance a wireless emitter.
Of course, other types of communication link technologies may be
used, such as, for example, optical. The FSR cell has a decreasing
electrical resistance in response to an increasing force applied
perpendicularly to the surface thereof. Each cell outputs a time
variable electrical signal for which the intensity is proportional
to the total vertical plantar pressure over its surface area. The
size and position of the plantar pressure sensors (22A, 22B, 24A,
24B) may be defined in accordance with the stability and the
richness (intensity) of the localized plantar pressure signals
provided by certain underfoot areas during locomotion. For example,
it was found by experimentation that the heel and the toe regions
are two regions of the foot sole where the Plantar Pressure Maximum
Variation (PPMV) may be considered as providing a signal that is
both stable and rich in information.
[0028] Accordingly, the controller (40) may use the data signals
from the four localized plantar pressure sensors (22A, 22B, 24A,
24B), as well as the information gathered from the data signals of
the other sensors (26) such as kinematic sensors, in order to
decompose the locomotion of the individual (10) into a finite
number of states, and generate the appropriate control signals for
controlling the actuating mechanism (16) according to the
locomotion. Of course, the controller (40) is not limited to the
use of the preceding data signals.
[0029] An example of a controller (40) and control system (100)
using sensors comprising plantar pressure sensors as well as
kinematic sensors is described in U.S. patent application Ser. No.
10/600,725 filed Jun. 20, 2003, entitled "CONTROL SYSTEM AND METHOD
FOR CONTROLLING AN ACTUATED PROSTHESIS", by Stephane Bedard, the
entire disclosure of which is hereby incorporated by reference
herein.
[0030] To facilitate the acquisition of the data in a repeatable
and dependable manner, the sensors (22A, 22B) are incorporated in
to the structure of the foot (20). An embodiment of the
instrumented prosthetic foot (20) is shown in more detail in FIGS.
3 and 4. The instrumented prosthetic foot (20) includes a foot
plate (53), forming an elongated body, with a connector (51) at one
end, a toe plate (55A) and a heel plate (55B) that is cantilevered
from the foot plate (53). Such an arrangement is provided by, for
example, a Vari-Flex.RTM. prosthetic foot from Ossur. Pressure
sensors (22A, 22B) are located at longitudinally spaced locations
on the underside of the foot plate (53) and heel plate (55)
respectively. The sensors (22A, 22B) are covered by rigid plates
(52A, 52B) and resilient pads (54A, 54B). The pressure sensors
(22A, 22B) are located so as to be responsive to loads imposed on
the instrumented prosthetic foot (20) at the regions corresponding
to the toe area and the heel area respectively.
[0031] The rigid plates (52A, 52B) covering the sensors (22A, 22B),
although not essential, help to optimize the pressure distribution
on the entire surface of the sensors (22A, 22B) as well as
inhibiting any shearing and may be made of 85 A durometer
polyurethane. Of course, other type of material may be used as
well.
[0032] The pads (54A, 54B) wrap up the rigid plates (52A, 52B) and
the sensors (22A, 22B), forming a ground engaging member, in order
to optimize the contact between the instrumented prosthetic foot
(20) and the ground. The pads (54A, 54B) may be made of 40 A
durometer polyurethane. Of course, other type of material may be
used as well.
[0033] In operation, therefore, as the foot (20) traverses the
ground, the force applied to the heel plate (55B) is measured by
the sensor (22B) and a corresponding signal forwarded to the
controller (40). The force applied to the toe plate (55A) is also
measured by the sensor (22A) and the relative loading between the
two locations is measured. As the foot (20) continues to traverse
the ground, the force applied to the toe area increases and that at
the heel decreases to provide a pair of signals from which the
disposition of the leg may be determined and the appropriate
control provided to the actuator (16).
[0034] An alternative embodiment of the instrumented prosthetic
foot (20) is shown in FIGS. 5 and 6. The instrumented prosthetic
foot (20) includes connector (61), foot plate (63), toe plate (64A)
and heel plate (64B), such as provided by, for example, a
Vari-Flex.RTM. prosthetic foot from Ossur. Pressure sensors (22A,
22B) are located between the foot plate (63) and rigid plates (62A,
62B). The pressure sensors (22A, 22B) are located so as to be
responsive to load imposed on the instrumented prosthetic foot (20)
at the regions corresponding to the toe area and the heel area
respectively. More specifically, pressure sensor (22A) is
sandwiched between a pair of rigid plates (62A), which in turn are
positioned between the heel plate (64B) and the foot plate (63).
Pressure sensor (22B) is sandwiched between a pair of rigid plates
(62B), which in turn are positioned between the foot plate (63) and
the connector (61).
[0035] As for the previous embodiment, rigid plates (62A, 62B)
covering the sensors (22A, 22B), although not essential, help to
optimize the pressure distribution on the entire surface of the
sensors (22A, 22B) as well as inhibiting any shearing and may be
made of 85 A durometer polyurethane. Of course, other type of
material may be used as well.
[0036] Another alternative embodiment of the instrumented
prosthetic foot (20) is shown in FIGS. 7 and 8. The instrumented
prosthetic foot (20) includes connector (71), top foot plate (75),
foam cushion core (73) and bottom foot plate (74), such as provided
by, for example, a LP Talux.RTM. prosthetic foot from Ossur.
Pressure sensors (22A, 22B) are sandwiched between pairs of rigid
plates (72A, 72B). The pressure sensors (22A, 22B) are located so
as to be responsive to load imposed on the instrumented prosthetic
foot (20) at the regions corresponding to the toe area and the heel
area respectively. More specifically, pressure sensor (22A) is
sandwiched between a pair of rigid plates (72A), which in turn are
positioned within gap (76A), which is located between a bottom foot
plate (74) and a foam cushion core (73). Pressure sensor (22B) is
sandwiched between a pair of rigid plates (72B), which in turn are
positioned within gap (76B), which is located within the foam
cushion core (73).
[0037] Again, as for the previous embodiments, rigid plates (72A,
72B) covering the sensors (22A, 22B), although not essential, help
to optimize the pressure distribution on the entire surface of the
sensors (22A, 22B) as well as preventing any shearing and may be
made of 85 A durometer polyurethane. Of course, other type of
material may be used as well.
[0038] In the previous embodiments, the force (or pressure) at the
toe and heel areas, F_toe and F_heel respectively, was obtained by
positioning pressure sensors (22A, 22B) directly at those areas.
More specifically, referring to FIG. 9, F_toe and F_heel were
obtained as follows: F_toe=F_toe_meas Equation 1 F_heel=F_heel_meas
Equation 2
[0039] In other possible embodiments of the instrumented prosthetic
foot (20), sensors (22A, 22B) may not be restricted to being
positioned directly at the toe and heel areas, the equivalent
information may be obtained by measuring the equivalent torque at
the ankle and the axial force at the connector of the instrumented
prosthetic foot (20). F_toe and F_heel may be defined in terms of
the torque measured at the ankle, M_ankle_meas, and the force
measured at the connector, F_conn_meas, using the following
equations: F_toe = M_ankle .times. _meas + ( F_conn .times. _meas
I_heel ) ( I_heel + I_toe ) Equation .times. .times. 3 F_heel = -
M_ankle .times. _meas + ( F_conn .times. _meas I_toe ) ( I_heel +
I_toe ) Equation .times. .times. 4 ##EQU1## [0040] where [0041]
I_heel is the distance between the center of the connector and the
center of the heel area; [0042] I_toe is the distance between the
center of the connector and the center of the toe area.
[0043] Following the previous discussion about the locations of
sensors (22A, 22B), a further alternative embodiment of the
instrumented prosthetic foot (20) is shown in FIGS. 10 and 11. The
instrumented prosthetic foot (20) includes connector (81), foot
plate (83), toe plate (84A) and heel plate (84B), such as provided
by, for example, a Vari-Flex.RTM. prosthetic foot from Ossur, and
load cells (22A, 22B). Load cells (22A, 22B) are located below
connector (91), load cell (22A) being slightly biased towards the
toe area of the foot and load cell (22B) being slightly biased
towards the heel area. Since the sensors (22A, 22B) are not located
directly at the toe and heel areas, Equation 3 and Equation 4 may
be used, for example by controller (40), to compute the equivalent
pressures at the toe and heel areas by defining the equivalent
torque at the ankle and the axial force at connector (81) as
follows: F.sub.--conn.sub.--meas=F.sub.--22B+F.sub.--22A Equation 5
M_ankle.sub.--meas=F.sub.--22BI.sub.--22B-F.sub.--22AI.sub.--22A
Equation 6 [0044] where [0045] F.sub.--22B is the force measured at
sensor 22B; [0046] F.sub.--22A is the force measured at sensor 22A;
[0047] I.sub.--22B is the distance between the center of the
connector (81) and the center of sensor 22B; [0048] I.sub.--22A is
the distance between the center of the connector (81) and the
center of sensor 22A.
[0049] In the previous embodiments of the instrumented prosthetic
foot (20), the force (or pressure) at the toe and heel areas, F_toe
and F_heel respectively, was obtained either by positioning
pressure sensors (22A, 22B) directly at those areas or by
positioning pressure sensors or load cells (22A, 22B) in other
areas and obtaining the equivalent information by computing the
equivalent torque at the ankle and the axial force at the
connector. Other types of sensors may also be used to obtain the
equivalent torque at the ankle and the axial force at the
connector. Such an example is illustrated by a further still
embodiment of the instrumented prosthetic foot (20), which is shown
in FIGS. 12 and 13. The instrumented prosthetic foot (20) includes
connector (91), mounted on pivoting ankle (93). Bumpers (92A, 92B)
are positioned between the pivoting ankle (93) and rocker plate
(95) located on a foot plate (94). The pivoting ankle (93) is
connected to the rocker plate (95) by a pivot pin (96). Such an
arrangement is provided by, for example, an Elation.RTM. prosthetic
foot from Ossur. A load cell (22A) and an optical encoder (22B) are
incorporated into the foot (20) to provide measurement of the
distribution of forces along the foot (20). Load cell (22A) is
positioned between connector (91) and pivoting ankle (93). Optical
encoder (22B) comprises reader (221) and disk (223). Reader (221)
is located on pivoting ankle (93) while disk (223) is located on
rocker plate (95) and encircles pivot pin (96). Once again,
Equation 3 and Equation 4 may be used, for example by controller
(40), to compute the equivalent pressures at the toe and heel areas
by defining the equivalent torque at the ankle and the axial force
at connector (91) as follows: F_conn_meas=F.sub.--22A Equation 7
M_ankle.sub.--meas=R_ankle.sub.--measR.sub.--const Equation 8
[0050] where [0051] F.sub.--22A is the force measured at sensor
22A; [0052] R_ankle_meas is the rotation measurement of pivoting
ankle (93) about pivot pin (96) as measured by optical encoder
(22B); [0053] R_const is a constant associated with the resistance
of bumpers (92A, 92B) to compression, which constant varies
depending in the material used.
[0054] A yet further alternative embodiment of the instrumented
prosthetic foot (20) is shown in FIGS. 14 and 15. The instrumented
prosthetic foot (20) includes connector (101), mounted on pivoting
ankle (103). Bumpers (102A, 102B) are positioned between the
pivoting ankle (103) and rocker plate (105) located on a foot plate
(104). The pivoting ankle (103) is connected to the rocker plate
(105) by a pivot pin (106). Such an arrangement is provided by, for
example, an Elation.RTM. prosthetic foot from Ossur. Pressure
sensors (22A, 22B) and load cell (22C) are incorporated into the
foot (20) to provide measurement of the distribution of forces
along the foot (20). Pressure sensor (22A) is positioned between
rocker plate (85) and bumper (82A) while pressure sensor (22B) is
positioned between rocker plate (85) and bumper (82B). A load cell
(22C) is positioned between connector (91) and pivoting ankle
(93).
[0055] In this embodiment, Equation 6 is used to compute the
equivalent torque at the ankle, while the axial force at connector
(101) is computed using the following equation:
F_conn_meas=F.sub.--22C Equation 9
[0056] Load cell (22C) is required to compute the axial force at
connector (101) since when there is no torque at the ankle, i.e.
the wearer of the prosthesis is standing still, the axial force is
being exerted in its entirety onto pivot pin (96).
[0057] In all of the described embodiments, the sensors (22A, 22B)
may be directly connected to interface (30) of control system (100)
or indirectly using an intermediary system (not shown), for
instance a wireless emitter. Of course, other types of
communication link technologies may be used, such as, for example,
optical.
[0058] Other types of non-articulated or articulated prosthetic
foot may be used as well as long as the selected prosthetic foot
provides approximately the same dynamical response as the ones
mentioned here above. Nevertheless, an articulated foot offers the
best performances. The instrumented prosthetic foot (20) may
further have an exposed metal or composite structure or it may have
a cosmetic covering that gives it the appearance of a human ankle
and foot.
[0059] It should be noted that the present invention is not limited
to its use with the mechanical configuration illustrated in FIG. 1
or the control system (100) illustrated in FIG. 2. It may be used
with a leg prosthesis having more than one joint. For instance, it
may be used with a prosthesis having an ankle joint, a
metatarsophalangeal joint or a hip joint in addition to a knee
joint. Moreover, instead of a conventional socket a
osseo-integrated devices could also be used, ensuring a direct
attachment between the mechanical component of the prosthesis and
the amputee skeleton. Other kinds of prostheses may be used as
well.
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