FIELD OF INVENTION
This invention relates to a contra lateral limb controlled
prosthetic knee joint to regulate the knee joint movement with
variable walking speeds including an additional hardware of
wireless transmission, system which does not add to the cost
significantly but promises a speed adaptive low cost prosthetic knee
joint and also presents embedded system and algorithm
development for heel switch implementation.
BACKGROUND OF INVENTION
Knee actively requires a programmed sequential action of
muscles, tendon and ligaments. Voluntary muscles at knee joint
are responsible for regulating the walking speed. There are 4 main
neural levels of locomotion-spinal cord, brainstem, cerebellum and
the cerebral cortex. Of these, the spinal cord is responsible for
setting the pace and rhythm of walking. A group of spinal
interneuron's, called V3 neurons, form complex networks and .act
as central pattern generators (CPG) which control the rhythm and
timing of walking. They relay signals from the spinal cord to the
motor neurons causing the relevant muscle to contract, producing
either flexion or extension. V3 neurons also make sure that the
intensity of activity in both the legs matches. This sets the pace of
motion and makes activities like .fast walking and running a smooth
affair.
Knee joint has q significant role in most of the locomotion
activities. While walking, the regulation of knee joint with change in
walking speed is desirable to make it an economic walking. The
networked muscles coordinate in a specific pattern for movement of
knee joint. The quadriceps group is responsible for extension and
the hamstring for flexion of the knee.
The control strategies applied with the current prosthetics
perform well with the limited environment. For example, EMG
controlled prosthetic knee joint does not work efficiently in the
tropical regions due to sweating. Hence, the input variables for the
implementation of control strategy vary from EMG to kinematic
variables of normal as well as prosthetic limb.
(i) EMG based control:
From simple mechanism/control strategy to lock and unlock
the prosthetic knee flexion joint through algorithms using EMG, the
research has been carried out to explore high pattern recognition
algorithm and complex control strategy using soft computing
techniques. Earlier research focuses on switching control of flexion
and extension and identifying terrain and speed of walking using
EMG signals and its simplest feature like mean frequency from
muscles like Rectus Fernoris and Semi-membranosus. The other
t
muscles of interest to recognize intent and posture has been Rectus
Fernoris, Gluetus maximus, Gluetus Medius, Addictor Longus,
tensor fascii later and hamstring muscle, especially or the intent to
change from one mode to other. The energy of EMG of femur
muscle was used as a feature to estimate the knee joint extension
and flexion. Pattern recognition algorithms and soft computing
techniques have got special attention for identification and
prediction of postures to control the AK prosthesis. Varol et. al.,
(2010) proposed Gaussian Mixture Model (GMM) as a classification
tool for multiclass intent recognition from EMG, preprocessed by
dimension reduction 'techniques Principal Component Analysis
(PCA and Linear Discriminant Analysis (LDA). Slavica Jonic el. al.,
(1999) employed three machine learning techniques, namely
Multilayer perception with Levenberg-Marquardt modification of
back propagation algorithm, an adaptive neurofuzzy inference
system inference system (ANFIS) and Inductive activation pattern
and joint angles from the past history of EMGs and joint angle of
strides parameters. To make the system/algorithm more robust
they trained the network with different length of strides and
achieved the cross correlation coefficient of more than 0.9 1 between
estimated and measured patterns, of EMG and joint angels. The
drawback with this type of system is that long training period is
required for the amputee to generate a control command using
EMG signal strength.
(ii) Kinematic variable control:
Kinematic variables represent walking phase and control the
knee damping. However, very limited research has used the knee
angle measurement of normal limb for the control of prosthetic
knee joint. The accuracy of gait identification depends on so many
factors, especially the sensor and required signal processing. The
poor performance of the sensors and highly complex algorithms are
the obstacles in designing reliable prosthesis. Three types of Force
Resistive Sensors (FSR) and an inclinometer have been used for
discriminating and walking with the accuracy of more than 90%.
The other sensors of popular choice are foot switches,
accelerometers, pendulum resistors and goniometers. The
overburdening of sensors leads to discomfort to the amputee. A
flexible kinematic-based modeling was developed to reduce the
number of sensors. Being a measured variable from mechanical
sensor; kinematic variables have been popular choice to detect the
gait phase. Fuzzy inference System (FIS) based on the hip, knee and
ankle angle trajectories' were developed to identify gait phases, their
transitions and durations. Realizing the importance of gait
4
kinematic variables and attempt was made to predict them using
Electromyogram. Though it used Artificial Intelligence '(AI)
techniques like Neural Network (NN) but was not found to be
suitable for real time execution in prosthesis. EMG itself has been
used for walking phase recognition in amputees. A gyroscope and
an accelerometer at shank and foot segment were used to classify
different walking conditions employing Support Vector Machines
(SVM) classifier. However, very limited research has used the knee
angle measurement of normal limb for the control of prosthetic
knee joint. Peak hip angle for a complete gait cycle and foot
switched on prosthesis side was used for speed adaptation swing
control of prosthetic knee joint.
Knee angle measurement has to be precise, and accurate for
gait identification. For off line analysis the kinematic variable can
t:
be measured by Charge Coupled Device (CCD) camera. While
designing prosthesis for real time monitoring data from knee joint,
device has to be reliable, easily mountable and locally repairable.
The available devices are goniometer, accelerometer and gyroscope.
Goniometer needs visual inspection and therefore need modification
for prosthesis use. Electronic accelerometers,available, have 5
degree error in simulation study. The hybrid rate gyroscopeaccelerometer
was developed to estimate the knee angle and
angular velocity. The mean error for the model, able-bodied and
paraplegic standing trials were 2:l ", 2.4 and 2.3 "s-1, 5.0 "s-1 and
1 1.8 s - 1 respectively for knee angle and angular velocity. The
objective of all the mentioned devices is accurate measurement.
For prosthesis application, other parameters viz. Easily
mountable, comfort and cost need to be accounted for. The
advancement in digital devices like microcontrollers and
microprocessors has eypanded scope for accurate measurement at
low cost.
There has been a long debate on the level of comfort among
amputees in the measurement of EMG and joint angle. On line knee
angle monitoring is difficult when compared to EMG while joint
angel gives better gait phase estimate. A combination benefit of
both can enhance the gait phase estimation. A simulation study
was carried out to estimate joint angle from EMG signal of rectus
femoris. In this study, a two step process, EMG from normal limb
was first used to estimate the knee angle of the same limb using
Radial . Basis Function (RBF) Neural Network and then the
estimated knee joint angle of normal limb was used to predict
prosthesis knee angle using Error Back Propagation (EBP) of
Multilayer Perceptron (MLP) network. Though the research shows
very high accuracy in estimation, it was a two step process with an
additional controller consisting of a prosthetic system equation of
inverse dynamics and hence limited to simulation study, hardware
implementation on the prosthesis could not be achieved. Further,
knee angle for walking up to 60 degree was used, while it ranges
beyond this value in normal gait cycle. The knee angle while
walking is not similar,for every person in range and fuzziness is
there inherently. This research work explores the hybrid advantages
in approach of Neural Network and Fuzzy logic in terms of Adaptive
Neuro Fuzzy Inference System (ANFIS) which is dissimilar to other
research has not been used in the past.
(iii) Contra lateral control:
Initially, contra lateral control strategy was a hybrid
combination of both the limb's signals to predict and control
prosthetic knee joint. The knee joint angle (0k) and hip joint angle
(ah) from the prosthetic limb along with foot switch signals from
the normal limb were used to decide the phase of level walking and
hence controlling the damping at the prosthetic knee joint. However
the validity of synchronization of all the signals is of little concern.
A simulation study employing fuzzy controller using .the
measurement of sound and prosthetic limb to control the prosthetic
knee joint damping is reported calculating error between the
trajectory of normal limb knee and prosthetic knee, as a fuzzy
variable. With this controller the author achieved the Root Mean
Square (RMS) error of 2 Degree between normal and prosthetic knee
angle. Though it was a simulation study, no hardware
implementation is reported elsewhere. In a similar approach, a
simulation on computer code was implemented to design the
structure based rules for controlling above knee (AK) Prosthesis. To
make it speed adaptive, heel and toe switch duration on prosthesis
foot was calculated as a threshold based indirect measurement of
walking speed. However the study here used only the heel switch,
on normal limb to calculate speed indirectly. This reduces any
possibility of cognitive load on the amputee. In the past a limited
research reported the measurement of walking speed. Hendry et.
al., (1990) used an optical beam to detect speed for a limited
distance that is not suitable for use in prosthesis for real time
adjustments with speed of walks. In another attempt, Smith et. a1
(1990) used the delay between transmitted and ultrasonic wave to
estimate the walking speed. Though a quantitative estimation, its
limitations was of ultrasonic wave propagation. The classification of
walking speed as normal, slow and fast has been successfully
implemented here with a heel switch incorporated with an
algorithm in the microcontroller. This does not add any significant
hardware to the developed prosthesis and hence provide a unique
feature to achieve the desired knee angle with appropriate damping
adjustments. The toe switch is not taken into consideration on
7
account of transition calculation because by the time the toe switch
is pressed, a significant amount of swing phase on prosthetic side is
covered, Similar approach was adopted using the delay of
prosthetic foot switches and pneumatic actuator. In a similar
research work, a complete gait cycle was used to recognize -the
speed of walking using the maximum angle of hip movement and
then trigger an output signal to control the knee damping. The
drawback of this system was that the information was transferred
to the control unit using a flexible cable while the wireless is
desirable.
Considerable efforts have been regularly initiated to improve
the various aspects relating with prosthetic knee joint devices and
its mechanism as evident from a large number of patents being filed
every years. A sample survey has been conducted during the R&D
phase of instant invention with an aim not to reinvent or repeat any
effort which has already been patented. For example WO Pub. No.
1999008621 on KA LOWER LIMB PROSTHESIS" highlights a lower
limb prosthesis for an above-knee amputee has an adaptive control
system which includes a knee flexion control device arranged to
resist flexion at the knee joint both hydraulically and pneumatically
by means of a dual piston and cylinder assembly. Sensors arranged
to sense knee bending moments and knee flexion angle provide
electrical signals which are fed to a processing circuit for
automatically adjusting the hydraulic and pneumatic resistance to
flexion according to the activity mode of the amputee and, when
walking, according to the speed of the cylinder containing hydraulic
fluid. The hydraulic resistance to flexion predominates during the
stance phase, and pneumatic resistance predominates during the
swing phase. Provision is made for programmable resistance during
level walking, walking on an incline, descending stairs and during a
stumble.
WO Pub. No. 1999044547 on "LOWER LIMB PROSTHESIS
AND CONTROL UNIT" ieports a lower limb prosthesis for an aboveknee
amputee which has a knee movement damper which is
dynamically adjustable in response to outputs from an electronic
control device coupled to sensors in the prosthesis, the control
device being configured such that the damper is automatically
adjusted to minimize the step-to-step variability of at least one
sensed kinetic or kinematic parameter of locomotion.
WO Pub. No. 2001017466 on "A LOWER LIMB
PROSTHESIS" discloses a lower limb prosthesis which has a pelvic
attachment, thigh and* shin components interconnected by a knee
joint, and, interconnecting the pelvic attachment and the thigh
component, a hip joint which includes an adaptive hip flexion drive
mechanism. This mechanism is arranged to apply a dynamically
variable flexion moment to the hip joint, and comprises an adaptive
resilient energy storing device which stores energy during hip
extension and returns the stored energy during subsequent flexion.
The energy storage device comprises an electronically controlled
piston and cylinder assembly, the piston rod of which is, itself, a
telescopic mechanism for limiting the duration of the swing phase.
US App. No. 20040186591 on "PROSTHETIC KNEE JOINT
MECHANISM" reports a prosthetic knee joint mechanism which has
a hydraulic load-activated knee-stabilizing device for resisting joint
flexion. A rotary piston connected to one part of the mechanism is
rotatable within a fluid-filled fluid displacement chamber associated
with another part of the mechanism to drive fluid through a fluid
passage which contains a main valve which restricts or allows joint
flexion according to the position of a valve member within the valve.
The valve member is movable towards an open position in response
to fluid pressure in the fluid passage upstream of the valve member
caused. by application of a flexion torque to the knee joint
mechanism, movement of the valve member in the direction of the
open position being at least resisted by a valve control arrangement
actuated by application of the wearer's weight. The weightresponsive
valve control arrangement is preferably a weightresponsive
pilot valve for hydraulically resisting movement of the
valve member of the main valve.
WO Pub. No. 2005087144 on "CONTROL SYSTEM AND
METHOD FOR A PROSTHETIC KNEE" provides for a prosthetic or
orthotic system including a magnetorheological (MR) damper. The
MR damper may be configured to operate in shear mode. In one
embodiment, the MR damper includes a rotary MR damper. A
controller is configured to operate the damper. A mobile computing
device may be adapted to intermittently communicate configuration
parameters to the controller. A method of configuring a prosthetic
or orthotic system is also disclosed.
WO Pub. No. 2005 110293 on "MAGNM'ORHEOLOGICALLY
ACTUATED PROSTHETIC KNEEn relates to a magnetorheologically
actuated prosthetic knee which, in one embodiment, comprises an
extension assist to facilitate knee extension. The knee in another
embodiment comprise& a flexible diaphragm that substantially
prevents or mitigates undesirable pressure build-up the chamber.
The knee in yet another embodiment comprises a specially
configured dynamic seal that is utilized to seal a
magnetorheological fluid comprising a liquid and a solid particle
within the chamber of the knee. Advantageously, the knee allows an
amputee to move comfortably, safely and in a substantially natural
and life-like manner in various dynamic and static states, terrains
and topography.
Canadian Pat. No. 2559890 on "CONTROL SYSTEM AND
METHOD FOR A PROSTHETIC KNEE" REPORT A prosthetic or
orthotic system (100) including a magnetorheological (MR)
damper. The MR damper may be configured to operate in shear
mode. In one embodiment, the MR damper includes a rotary MR
damper. A controller is configured to operate the damper. A mobile
computing device (320) may be adapted to intermittently
communicate configuration parameters to the controller. A method
of configuring a prosthetic or ofiotic system is also disclosed.
US App. No. 20060135883 on "SYSTEMS AND METHODS
FOR PROCESSING LIMB MOTIONn discloses control systems and
methods for processing a time series of signals associated with the
movement of a device associated with a limb. The time series of
motion signals is filtered, such as thorough an autoregressive filter,
and compared to stored data sets representing a limb-motion event
and/or phase. In certain examples, a plurality of accelerometers
generate the time series of motion signals based at least on
acceleration measurements in three orthogonal directions and/or
planes. The acceleration measurements may relate to the movement
of an artificial limb, such as a prosthetic or orthotic device. Upon
determining an event and/or phase of limb motion, the control
,
system may trigger an actuator to appropriately adjust one or more
prosthetic or orthotic joints.
US App. No. 20060224247 on "SYSTEMS AND METHODS
FOR ACTUATING A PROSTHETIC ANKLE BASED ON A RELAXED
11
POSITION" highlights the Systems and methods for sensing
actuating a prosthetic ankle. In one example, the system, such as
an actuated prosthetic ankle joint, detects that the user has moved
to a relaxed position, such as sitting, reclining, crawling, or leaning.
In response, the actuated prosth'etic ankle joint actively adjusts the
angle between the members of the ankle to a relaxed state. The
system .may further detect when the user has moved to exit the
relaxed position, and may actively adjust the angle between the
members of the ankle to an exit state.
US App. No. 20060224248 on "PROSTHETIC KNEE JOINT
MECHANISM" focuses on a prosthetic knee joint mechanism which
has an hydraulic load-activated knee-stabilizing device for resisting
joint flexion. A rotary piston (34) connected to one part of the
mechanism is rotatable within a fluid-filled fluid displacement
chamber (18) associated with another part of the mechanism to
drive fluid through a fluid passage which contains a main valve (38)
which restricts or allows joint flexion according to the position of a
valve member within the valve. The valve member is movable
towards an open position in response to fluid pressure in the fluid
passage upstream of the valve member caused by application of a
flexion torque to the knee joint mechanism, movement of the valve
member in the direction of the open position being at least resisted
by a valve control arrangement actuated by application of the
wearer's weight. The weight-responsive valve control arrangement is
preferably a weight-responsive pilot valve (32) for hydraulically
resisting movement of the valve member of the main valve.
US App. No. 20060235544 on "DEVICE AND SYSTEM FOR
PROSTHETIC KNEES AND ANKLESn provides a device and system
for a prosthetic device having an articulating joint for a leg
amputee. The device includes a joint housing forming a chamber,
and the chamber has a first opening. A rotary hub can be disposed
within the joint housing and configured to act as the articulating
joint. One or more vanes can extend outwardly from the rotary hub,
and the vane is configured to actuate fluid flow through the first
opening.
US App. No. 20060282175 on "PROSTHETIC DEVICE
*
UTILIZING ELECTRIC VACUUM PUMP" discloses an evacuation
devices for evacuating the socket of a prosthetic limb, ~ n d
prosthetic limb systems employing such vacuum devices. The
evacuation devices each preferably include at least an electrically
powered vacuum pump and a power source. Such evacuation
devices can be attached at various locations on or in a prosthetic
limb. Because the electrically powered pump does not require
manual manipulation to create vacuum, it is substantially easier to
use than a manual pump. Due to the small size and small power
source required by such an electrically powered pump, an
evacuation device may be readily incorporated into a prosthesis.
US App. No. 2007050045 on "SENSING SYSTEM AND
METHOD FOR MOTION-CONTROLLED FOOT UNIT" illustrates a
system and method for sensing .movement of a device associated
with a limb. In one example, a prosthetic or orthotic system
includes a sensor assembly configured to measure movement of a
component of the system in a single direction while substantially
isolating negative effects of forces and/or loads in other directions.
For instance, the sensor assembly may be advantageously coupled
to a pivot assembly configured to substantially mimic a natural
,
ankle joint. The sensor assembly may monitor rotation of a foot unit
about an axis of a pivot pin of the pivot assembly and disregard
other movements and/or forces. For example, the sensor assembly
may include a potentiometer that detects rotation of an associated
elongated bellow portion about the axis, wherein the bellow portion
includes a plurality of ridges configured to substantially eliminate
effects of radial and/or axial forces. '
US App. No. 2007050047 on "SYSTEM AND METHOD FOR
DETERMINING TERRAIN TRANSITIONS" discusses a prosthetic or
orthotic system including a sensor module and a processing module
usable to determine a ierrain variable, such as a terrain transition.
In certain examples, the system is capable of anticipating a terrain
transition prior to the user experiencing the terrain transition,
which may include, for instance, a transition from level ground
walking to walking on stairs or may include a change in a slope of
the ground surface. In certain, embodiments, the system
advantageously monitors a posture and/or movement of the patient
to anticipate the terrain transition. Furthermore, the system may
control an actuator to appropriately adjust the prosthetic or
orthotic device to encounter the anticipated terrain transition.
I
WO Pub. No. 2007110585 on "LOWER LIMB PROSTHESIS
AND CONTROL UNIT" highlights a self-teaching lower limb
prosthesis, for an above-knee amputee, including a dynamically
adjustable joint movement control unit arranged to control
operation of the joint automatically. A control unit electrically
stores a target relationship between a kinetic or kinematic
parameter of locomotion and walking speed. The relationship
defines a number of values of the parameter associated with
different walking speeds. The control unit generates monitoring
signals representative of walking speed values and values of the
parameter occurring at different walking speeds. An adjustment
14
I
system adjusts the control unit automatically when the monitoring
signals indicate deviation from the target relationship so as to bring
the parameters close to that defined by the target relationship.
US App. No. 20080046096 on "INSTRUMENTED
PROSTHETIC FOOT" 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.
US App. No. 20080058959 on "INSTRUMENTED
PROSTHETIC FOOT" 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 aloAg the foot, and an interface for transmitting
signals from the sensor to the controller.
US App. No. 20080114272 on "CONTROL SYSTEM FOR
PROSTHETIC KNEEn relates to an automated speed-adaptive and
patient-adaptive control scheme and system for a knee prosthesis.
The control scheme and system utilizes sensory information
measured local to the prosthesis to automatically adjust stance and
swing phase knee resistances to a particular wearer under a wide
variety of locomotory activities. Advantageously, no patient-specific
information needs to be pre-programmed into the prosthetic knee
by a prosthetist or the patient. The system is able to adapt to
various types of disturbances once the patient leaves the
prosthetist's facility because it is patient-adaptive and speedadaptive.
US App. No. 20080243266 on "PROSTHETIC DEVICE
UTILIZING ELECTRIC VACUUM PUMP" highlights the Prosthetic
devices having vacuum components operative to evacuate the
interior of a prosthetic socket thereof, and control systems for use
therewith. The evacuation devices preferably include at least an
electrically powered vacuum pump and associated power source,
and a 'vacuum accumulator connected to the vacuum pump.
Associated control systems may be of various designs and may
employ wired or wireless communication. Control of an evacuation
device may be based on vacuum level, residual limb volume,
residual limb motion, user activity level or other device parameters.
US App. No. 20080300692 on "PROSTHETIC ANKLE AND
FOOT COMBINATION* pin-points a prosthetic ankle and foot
combination which has an ankle joint mechanism constructed to
allow damped rotational movement of a foot component relative to a
shin component. The mechanism provides a co'ntinuous
I
hydraulically damped range of ankle motion during walking with
dynamically variable damping resistances, and with independent
variation of damping resistances in the plantarflexion and
dorsiflexion directions. An electronic control system coupled to the
ankle joint mechanism includes at least one sensor for generating
signals indicative of a kinetic or kinematic parameter of locomotion,
the mechanism and the control system being arranged such that
the damping resistances effective over the range of motion of the
ankle are adapted automatically in response to such signals. Single
and dual piston hydraulic damping arrangements are disclosed,
including arrangeme'nts allowing independent heel-height
adjustment.
US App. No. 20080215161 on "SYSTEM AND METHOD FOR
MOTION-CONTROLLED FOOT UNIT" discloses a system and
method associated with the movement of a limb. In one example,
the system, such as a prosthetic or orthotic system, includes an
actuator that actively controls, or adjusts, the angle between a foot
unit and a lower limb member.' A processing module may control
movement of the actuator based on data obtained from a sensor
module. For instance, sensing module data may include
I
information relating to the gait of a user and may be used to adjust
the foot unit to substantially mimic the movement of a natural,
healthy ankle. The system may further accommodate, for example,
level ground walking, traveling up/ down stairs, traveling up/ down
sloped surfaces, and various other user movements. In addition,
the processing module may receive user input or display output
signals through an external interface. For example, the processing
module may receive a heel height input from the user.
US App. No. 20090222105 on "TRANSFEMORAL
PROSTHETIC SYSTEMS AND METHODS FOR OPERATING THE
SAME" relate to increasing the functionality of a transfemoral
prosthetic device. In one embodiment, the transfemoral prosthetic
device is configured such that the prosthetic knee maintains a load
consistent with a healthy knee walking on level ground, while the
prosthetic ankle adjusts for the incline or decline. In certain
embodiments, adjustments, such ' as a toe lift function, are
automatically performed after about three strides of the
transfemoral prosthetic device user and/or when each of the strides
has a stride speed of at least about 0.55 meters/second. ~
8
US App. No. 20090030530 on "ELECTRONICALLY
CONTROLLED PROSTHETIC SYSTEM* discloses a prosthetic joint
system for users comprising a housing having an interior cavity, a
center axis in said interior cavity, and an attachment means for
fmedly connecting said housing to said user; an inner cylinder
disposed in said housing interior cavity wherein said inner cylinder
rotates around said center axis of said housing; an appendage
attached to said inner cylinder;' a sensor system attached to said
appendage; and a dampening system, having a power source, in
communication with said sensor system, said inner cylinder, and
said housing for contrilling dampening of the rotation of said inner
cylinder around said center axis of said housing.
US App. No. 20090259320 on "GENERATOR FOR
PROSTHESIS AND ORTHOSIS* illustrates a means for using body
energy to generate electrical current to power the electronics,
sensors, actuators and other electronic components in
microprocessor-controlled prosthetic or orthotic joints.
Furthermore, a means for using the generator to provide swingphase
damping is disclosed whereby the damping level can be
controlled and adjusted electronically.
US App. No. 201 10106274 on "SYSTEM AND METHOD FOR
MOTION-CONTROLLED FOOT UNIT" relates to a system and
method associated with the movement of a limb. In one example,
the system, such as a prosthetic or orthotic system, includes an
actuator that actively controls, or adjusts, the angle between a foot
unit and a lower limb member. A processing module may control
movement of the actuator based on data obtained from a sensor
module. For instance, sensing module data may include
information relating to the gait of a user and may be used to adjust
the foot unit to substantially mimic the movement of a. natural,
healthy- ankle. The system may further accommodate, for example,
level ground walking, traveling upidown stairs, traveling upidown
sloped surfaces, and various other user movements. In addition,
the processing module may receive user input or display output
signals through an external interface. For example, the processing
module may receive a heel height input from the user.
US App. No. 20090054996 on "LOWER LIMB PROSTHESIS
AND CONTROL UNIT" discloses a self-teaching lower limb
prosthesis, for an above-knee amputee, including a dynamically
adjustable joint movement control unit arranged ta control
operation of the joint' automatically. A control unit electrically
stores a target relationship between a kinetic or kinematic
parameter of locomotion and walking speed. The relationship
defines a number of values of the parameter. associated with
different walking speeds. The control unit generates monitoring
signals representative of walking speed values and values of the
parameter occurring at different walking speeds. An adjustment
system adjusts the control unit automatically when the monitoring
signals indicate deviation from the target relationship so as to bring
the parameters close to that defined by the target relationship.
I
US App. No. 20090143870 on "INSTRUMENTED
PROSTHETIC FOOT" 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.
US App. No. 20090054996 on "LOWER LIMB PROSTHESIS
AND CONTROL UNI+ relates to a self-teaching lower limb
prosthesis, for an above-knee amputee, including a dynamically
adjustable joint movement control unit arranged to control
operation of the joint automatically. A control unit electrically
stores a target relationship between a kinetic or kinematic
parameter of locomotion and walking speed. The relationship
defines a number of values of the parameter associated with
different walking speeds. The control unit generates monitoring
signals representative of walking speed values and values of the
parameter occurring at different walking speeds. An adjustment
system 'adjusts the codtrol unit automatically when the monitoring
signals indicate deviation from the target relationship so as to bring
the parameters close to that defined by the target relationship.
Canadian Pat. No. 2647117 On "LOWER LIMB PROTHESIS
AND CONTROL UNIT" discloses A self-teaching lower limb
prosthesis, for an above-knee amputee, including a dynamically
adjustable joint movement control unit arranged to control
operation of the joint automatically. A control unit electrically
stores a target relationship between a kinetic or kinematic
parameter of locomotion and walking speed. The relationship
I
defines a number of values of the parameter associated with
different walking speeds. The control unit generates monitoring
signals representative of walking speed values and values of the
parameter occurring at different walking speeds. An adjustment
system adjusts the control unit automatically when the monitoring
signals indicate deviation from the target relationship so as to bring
the parameters close to that defined by the target relationship.
US App. No. 20100324698 on "FEEDBACK CONTROL
SYSTEMS AND METHODS FOR PROSTHETIC OR ORTHOTIC
DEVICES" teaches the, methods and systems which are used for
monitoring a global position or location of a prosthetic or orthotic
device and to provide feedback control of the device. Certain
methods may employ remote transmitting devices and receivers to
recognize when a prosthetic or orthotic device user is in a moving
vehicle and, therefore, initiate automatic shut-off, driving mode, or
relaxed mode. Other methods may employ remote transmitting
devices and receivers to identify the global position of the prosthetic
or orthotic device, compare the'global position to a stored terrain
mapped database and output feedback control instructions and/or
alerts to the prosthetic or orthotic device based at least ili part on
I
the stored terrain mapping information.
US App. No. 20100324456 on "SYSTEMS AND METHODS
FOR PROCESSING LIMB MOTION" discloses the control systems
and methods for processing a time series of signals associated with
the movement of a device associated with a limb. The time series of
motion signals is filtered, such as thorough an autoregressive filter,
and compared to stored data sets representing a limb-motion event
and/or phase. In certain examples, a plurality of accelerometers
generate the time series of motion signals based at least on
acceleration measureqents in three orthogonal directions and/or
planes. The acceleration measurements may relate to the movement
of an artificial limb, such as a prosthetic or orthotic device. Upon
determining an event and/or phase of limb motion, the control
system may trigger an actuator to appropriately adjust one or more
prosthetic or orthotic joints.
US App. No. 20100160844 on "HIGH TORQUE ACTIVE
MECHANISM FOR ORTHOTIC AND/OR PROSTHETIC DEVICEB
highlights a high torque active mechanism for an orthotic and/or
prosthetic joint using a primary brake which can be provide by
magnetorheological (MR) rotational damper incorporating and an
additional friction brake mechanism driven by the braking force
generated by the MR damper. This combination of MR damper and
friction brake mechanism allows an increase in torque density while
keeping the same level of motion control offered by the MR damper
alone. The increased torque density achieved by this high torque
active mechanism allows to minimize the size of the actuating
system, i.e. its diameter and/or breath, while maximizing its
braking torque capability. In this regard, the friction brake
mechanism is advantageously positioned around the MR damper,
such thk the dimensioh of the package is minimized.
US App. No. 20110015762 on "JOINTS FOR PROSTHETIC,
ORTHOTIC AND/OR ROBOTIC DEVICES" discloses an artificial foot
device which may include a talus body, a core operatively coupled
with the talus body by a first joint, and a toe operatively coupled
with the core by a second joint. The first joint may provide for
constrained relative movement between the talus body and the
core. The second joint may provide for constrained relative
movement between the core and the toe. Constrained relative
movement between the talus body and the core may substantially
correspond to a coordinated movement of a first natural joint and a
second natural joint during ambulation of a natural human foot.,
US App. No. 20110093091 on "TENSEGRITY JOINTS FOR
PROSTHETIC, ORTHOTIC, AND ROBOTIC DEVICES" relate to a
prosthetic, orthotic, or robotic foot having at least two joints. One
joint is located in a position analogous to the human MTP joint, and
the other is located in a position analogous to the human subtalar
joint. Motions of these two joints are mechanically couples.
Furthermore, these joints are created using "tensegrity" design
principals, where connections between the compression members
are made by a network of tension members. These tension members
create axes of motion, and limitations on those axes of motion.
Actuators or linear elastic "springs" are use to alter the
torque/angular deflection response curve of these joints, so that the
rollover profile of the human foot can be duplicated by this
invention.
US App. No. 20110118878 on "SYSTEM AND METHOD FOR
JOINT MOTION SIMULATION" reports a simulator for driving a
prosthetic element includes a prosthetic drive mechanism that drive
the prosthetic element during an accelerated wear test of the
prosthetic element. A simulation input represents the action of the
simulator and a sensor mechanism is used to measure the force
and torque applied to the prosthetic element. Position and
orientation control sensors are further used to measure
displacement of the prosthetic element. A closed loop feedback
control system, responsive to the sensors, is used to determine a
drive signal for the drive mechanism. The control system
advantageously adds a computational model that incorporates
mechanical representations of ligament fibers. The computational
model is a non-human approximation to situations that would be
encountered by the prosthesis within the human body and includes
dimensional geometry of insertion sites and mechanical properties
of ligament fibers. The computational model is responsive to the
position and angular displacement sensors to determine constraint
forces and torques of ligaments that mitigate action of the control
system. The action of the control system may further be mitigated
by the measured force and torque
US ~ p p . NO. 2oiioi3os47 on "INSTRUMENTED
PROSTHETIC FOOT " 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.
US App. No. 20110093089 on "ELECTRONICALLY
CONTROLLED PROSTHETIC SYSTEM" highlights a prosthetic joint
system for users comprising a housing having an interior cavity, a
center axis in said interior cavity, and an attachment means for
fixedly connecting said housing to said user; an inner cylinder
disposed in said housing interior cavity wherein said inner cylinder
rotates around said center axis of said housing; an appendage
attached to said inner cylinder; a sensor system attached to said
appendage; and a dampening system, having a power source, in
communication with said sensor system, said inner cylinder, and
said housing for controlling dampening of the rotation of said inner
cylinder around said center axis bf said housing.
There has been, thus, a constant demand and need to
provide's better and efficient device for human usage and such a
solution has now been provided by the instant invention.
OBJECTIVES OF THE INVENTION:
The main object of the invention is to explore the contra
lateral controlled methodology for prosthetic knee joint.
Another object of this invention is to provide a reliable and
secured wireless transmission for data transfer from normal to
prosthetic limb.
Yet another object of this invention is to devise a prototype
knee joint for real time implementation of algorithms.
A further object of this invention is to develop a Speed
adaption with minimal number of sensors.
The foregoing has outlined some of the pertinent objectives of
the invention. These objectives should not be construed to be
merely illustrative of some of the more prominent features and
applications of the intended invention. Many other beneficial results
can be obtained by applying the disclosed invention in a different
manner or modifying the invention within the scope of disclosure.
Accordingly, other objectives and a full understanding of the
invention and the detailed description of the preferred embodiment
in addition to the scope of invention are to be defined by the claims
undertaken.
These and other objectives and advantages of the invention
will be apparent from the ensuing description.
BRIEF DESCRIPTION OF DRAWINGS:
Further objectives and advantages of this invention will be
more apparent from the ensuing description when read in
conjunction with the accompanying drawings wherein:
Figure 1. : Flow chart of Algorithm.
Figure 2. : Block schematic.
Figure 3. : Gait event detection using EVA
Figure 4. : I Experimental results for healthy person
from different walking speeds.
Figure 5. : Heel switch implementation using locally
available shoe.
Figure 6. : The prototype assembly.
While the invention is described in conjunction with the
illustrated embodiment, it is understood that it is not intended to
limit the invention to such embodiment. On the contrary, it is
intended to cover all alternatives, modifications and equivalents as
may be included within the spirit and scope of the invention
disclosure as defined by the claims.
STATEMENT OF THE INVENTION
According to the invention, there is provided a Contra Lateral
Limb Controlled Prosthetic Knee Joint, to be attached with the
stump on amputee leg, having a stepper motor to be used as an
actuator and an electronic assembly, comprising of a micro
controller and motor driver with receiver, placed below the
prosthetic knee, to work in conjunction with a heel switch
implementation schemq using locally available shoe.
DETAILED DESCRIPTION OF THE INVENTION
At the outset of the description, which follows, it is to be
understood that the ensuing description only illustrate a particular
form of the invention. However, such a particular form is only an
exemplanary embodiment and the teachings of the invention are
not intended to be taken restrictively.
For the purpose of proinoting an understanding of the
principles of the invention, reference is now to be made to the
embodiments illustrates and the specific language would be used to
describe the same. It is nevertheless to be understood that no
limitations of the scope of the invention is hereby intended, such
alterations and further modifications in the illustrated bag and
such further applications of the principles of the invention as
illustrated therein being contemplated as would normally occur to
one skilled in the art to which the invention relates.
To overcome the aforesaid drawbacks, a research project has
been initiated at Indian Institute of Technology Delhi by the
inventors to develop an Above Knee prosthesis thus requires
significantly less training time and cognitive load for the amputee.
The work has direct application in development of cost effective
contra lateral speed adaptive Above Knee prosthesis.
The invention presents embedded system and algorithm
development for heel switch implementation to regulate the knee
join movement with variable walking speeds. This algorithm
regulates the knee damping automatically by calculating the speed
of walking form the switching duration of heel switch at normal
limb. Though the prosthesis uses an additional hardware of
wireless transmission system, which does not add to the cost
significantly, but promises a speed adaptive low cost AK prosthesis
thus requires significantly less training time and cognitive load for
the amputee. The work has direct application in development of
cost effective contra lateral speed adaptive above knee (AK)
prosthesis.
Knee angle algorithm predicted efficiently for a constant
walking speed. The first figure shows flow chart of algorithm. To
make this speed adaptive, a heel switch is implemented which
indirectly measures the speed from the heel strike duration and
accordingly controls the joint stiffness in the mechanical
arrangement on prosthesis side. The heel switch implementation
and algorithm is given hereunder
A heel switch, in the shoe of the normal limb, has been
employed to calculate indirect measurement of walking speed. This
reduces any possibility of cognitive load on the amputee as the
normal limb movement is still enduring. Similar approach was
adopted using the delay of prosthesis foot switches and pneumatic
actuator. The present work does not implement toe switch as a
significant amount of swing ~ h a s eo n prosthetic side is covered
during the toe strike of contra lateral limb. In a similar research
work, a complete gait cycle was used to recognize the speed of
walking using the maximum angle of hip movement and then
trigger an output signal to control the knee damping. The drawback
of this system was that the information was transferred to control
unit using flexible cable while the wireless is desirable for
acceptable prosthesis. In this work Radio Frequency (RF) is
implemented for wireless communication for data transfer from
prosthetic limb to contra lateral limb. The purpose of this part of
research work is to automatically adjust the knee damping during
I the swing phase and achieve the'intended knee angle after checking
I the walking speed from heel switch transition duration. When the
I heel switch is pressed, the knee is locked on prosthesis side to
ensure stability. For each step, heel switch transition was
performed to confirm the modulation in walking speed. In case of
change in walking speed, desired knee angel was controlled in real
time. Sufficient study is carried out in the laboratory with live
demonstration of healthy person walking to confirm that heel
switch transition duration is inversely proportional to changes with
walking speed.
The, gait event, heel strikk and heel off were detected using
EVA as shown in Fig. 3, simultaneously the swing duration was
observed with different walking speed viz. slow, normal and fast.
Fig.2 shows the block schematic. It shows the three steps of
functioning and how the different modes of speed are classified. The
data distribution of different walking speeds also shows a
significant difference between the speeds does exist in all the
subjects. An infinitesimal difference between the normal and fast
speed was noticed which was compensated in hardware by using 8-
bit resolution microcontroller.
Fig.4 shows the experimental results for healthy person with
different walking speeds. The plot shows heel strike duration vs.
swing duration of opposite limbs. The instant observation shows
that all the three speeds can be classified using heel strike duration
and the swing duration is significantly different for the all 'the
walking speeds. The data was used to decide the threshold for
walking speed classification during real time implementation.
In the prototype assembly, a stepper motor is used as an
actuator and has been placed on knee joint. The pulse from
microcontroller to drive is controlled by identified the walking speed
so that it covers the swing phase in desired time. The electronic
assembly (microcontrol'ler and motor driver with receiver) is placed
below the prosthetic knee.
Fig. 5 shows heel switch implementation using locally
available shoe. It has a wireless transmitter placed at the lateral
side covered with a cloth packed for safety. The mechanical switch,
with debouncing switch to avoid false signal, is placed at the heel to
monitor heel strike and heel off event which is further transmitted
wirelessly to prosthetic knee joint using RF transmitter to calculate
the delay.
The microprocessor has a counter which increases the
counter value depending upon the heel switch on-off positions,
hence calculates the delay between heel strike and heel off event,
compares the counter value with threshold, subjective of the
individual amputee and class@ the speed as slow, normal and fast.
Having classified the walking speed, the microcontroller directs the
stepper motor a control signal to modulate the number of steps per
second for driving the prosthetic knee during the complete walk.
Complete methodology can be divided in three major steps as
shown in Fig. 2. The push button with debouncing circuit is placed
at the extreme back bf heel on normal limb. This ensures the
maximal margin of difference between the slow, normal and fast
speed. This advocates a high marginal threshold for the
classification speed. The decision of quantitative value of thresholds
to classify normal, fast and slow walking speeds has been decided
by observing several trial of walking with wide range of healthy
subjects.
As the heel switch at normal limb strikes, the prosthetic knee
gets locked. The microcontroller at the prosthetic knee monitors.
wirelessly, for heel off event. As the heel off occurs, the delay
between both events is calculated by the microcontroller followed bv
.I
the classification of walking speed as normal, fast and slow. As a - -
result, the prosthetic knee is unlocked with the required damping
for the classified speed.
The microcontroller again monitors for the heel strike at
normal limb and the loop goes on the complete walking.
It may be noted that the present invention is susceptible to
modifications, adaptations and changes by those skilled in art.
Such variant embodiments employing the concepts and features of
this invention are intended to be within the scope of the present
invention, which will be further set forth subsequently

WE CLAIM:
1. A Contra Lateral Limb Controlled Prosthetic Knee Joint, to be
attached with the stump on amputee leg, having a stepper
motor to be used as an actuator and an electronic assembly,
comprising of a micro controller and motor driver with
receiver, placed below the prosthetic knee, to work in
conjunction with a heel switch implementation scheme using
locally available shoe.
2. A Contra Lateral Limb Controlled Prosthetic Knee Joint as
claimed in claim 1 wherein heel switch implementation
scheme comprises of a wireless RF transmitter, placed at the
contra lateral side covered in a cloth packet attached to the
available shoe, and a mechanical push button switch with
debouncing circuit, placed at extreme back of the heel of
locally available shoe, to monitor heel strike and heel. off
event which is further transmitted wirelessly to micro
controller attached to prosthetic knee joint via RF transmitter
to calculate the delay.
3. A Contra Lateral Limb Controlled Prosthetic Knee Joint as
claimed in Claim 1 and claim 2 wherein the microcontroller
has a increment counter which increases the counter value
depending upon two heel switch on-off positions, calculates
the delay between heel strike and heel off event, compares the
counter value with thresholds, subjective to the individual
amputee, and classify the speed as slow, normal or fast.
4. A Contra Lateral Limb Controlled Prosthetic Knee Joint as
claimed in preceding dlaims wherein the said micro
controller, having classified the walking speed as slow, fast
and normal , directs the stepper motor a control signal to
modulate the number of steps for driving the prosthetic knee
during complete walk.
.5. A Contra Lateral Limb Controlled Prosthetic Knee Joint as
claimed in claim 1 wherein the microcontroller generates the
control signal so as to cover the swing phase in desired time
and achieve the intended knee angle after checking the
walking speed.
6. A Contra Lateral Limb Controlled Prosthetic Knee Joint as
claimed in claim 1 wherein the microcontroller at .the
prosthetic knee monitors the heel strike and heel off event for
locking and unlocking of prosthetic knee during complete
walk.
7. A Contra Lateral Limb Controlled Prosthetic Knee Joint as
claimed in preceding claims wherein the prosthetic knee joint
gets unlocked with the required damping for the given
classified speed depending upon three different pre-set mode
of speed.
8. A Contra Lateral Limb Controlled Prosthetic Knee Joint as
claimed in preceding claims as substantially described herein
with reference to the accompanying drawings.