WO2018236208A1

WO2018236208A1 - A prosthetic limb integrated with a sensory system

Info

Publication number: WO2018236208A1
Application number: PCT/MY2018/050043
Authority: WO
Inventors: Nur Azah HAMZAID; Farahiyah JASNI; Hanie Nadia SHASMIN; Zafirah ZAKARIA
Original assignee: Universiti Malaya
Priority date: 2017-06-22
Filing date: 2018-06-22
Publication date: 2018-12-27

Abstract

The present invention relates to a prosthetic limb integrated with a sensory system comprising of: a prosthetic socket (100) for receiving an amputee stump; a lever arm connecting the prosthetic socket (100) to an actuator for actuating a movement of the prosthetic limb; said sensory system comprising a plurality of a sensing elements (101) mounted to the prosthetic socket (100) for motion detection; and characterized in that: said prosthetic socket (100) comprises a plurality of cavities at an interior of said prosthetic socket (100) for placing the plurality of sensing elements (101) configured for detecting the motion based on ground reaction force and muscle contraction; a controller connected to the plurality of sensing elements (101) and the actuator for processing an output signal received from the plurality of sensing elements (101), and determining a user's intention movement.

Description

A PROSTHETIC LIMB INTEGRATED WITH A SENSORY SYSTEM

Background of the Invention

Field of the Invention

This invention relates to a prosthetic limb, and more particularly to a prosthetic limb integrated with a sensory system having multi-array of sensing elements for estimating an intended gait phase of an amputee.

Description of Related Arts

Transfemoral amputees are a sizeable subgroup of the amputee population as their expected mobility is less than patients with more distal amputations. They tend to walk slowly and prefer a short stride length compared to below knee amputation (Graham, Datta et al. 2007). Transfemoral amputees need to restore their self-esteem from their appearance to regain back their maximum functional mobility. The first primary interphase between the socket and the amputated limb is the prosthetic socket. When the patients try to perform the gait, the body load will be transferred to the stump and it needs an appropriate socket fitting to make sure the high satisfaction level with their prosthesis (Zhang, Zhu et al. 2013). The quality of the socket design decides on user's comfort and ability to control the appliance as the prosthetic socket act as a primary interface between the ground and residual limb. Furthermore, the forces from the prosthesis are applied to all over the body, through the stump, according to their location of application and all the forces contribute in mobility, function and acceptance of the device. Although most of the stump areas are considered as pressure tolerant but some of them are very sensitive and cannot support any pressure (Francois Friedel 2015).

Several types of prosthetic limbs have been disclosed in the prior art. For example, U.S. Patent Application No. 3,820,168 presents a servomotor for moving a prosthetic limb is actuated by a controller which responds to local variations in muscular rigidity as determined by one or more pressure sensors bearing upon the flesh of the wearer within an annular frame contacting an area of his body. The frame may be resiliently supported in a cutout of a rigid sleeve by one or more springs urging it into contact with an underlying stump. The contacts of the sensor form part of an electromagnetic vibrator whose oscillations, felt by the user, are modulated by a feedback signal controlled by the position or the speed of the prosthetic limb.

U.S. Patent Application No. 20100191 153 A1 disclosed parameters related to use of a prosthesis by a patient with a limb amputation are monitored using a tool that includes one or more piezoelectric force sensors. The resulting data are processed for use both in short and long term management of amputee patients. The sensor is a small modular unit that fits within or between traditional prosthetic components, e.g., below a prosthesis socket. The data produced by the tool are collected, processed, and stored. Optionally, the data are periodically communicated to a remote site via a network, e.g., over the Internet. The device and associated software used to process the data can be used to characterize activities conducted by a prosthesis user, to determine pistoning or threatening interface stress distributions between the limb and socket, mal-alignment of the socket, use of improper components, and other possibly undesired conditions that the amputee patient using the prosthesis may be experiencing.

U.S. Patent Application No. 2006012271 1 A1 disclosed an actuated leg prosthesis comprises a knee member, a socket connector provided over the knee member, an elongated trans-tibial member having a bottom end under which is connected an artificial foot, and a linear actuator. A first pivot assembly allows to operatively connect the trans-tibial member to the knee member. A second pivot assembly allows to operatively connect an upper end of the actuator to the knee member. A third pivot assembly allows to operatively connect a bottom end of the actuator to the bottom end of the trans-tibial member. The prosthesis can be provided as either a front actuator configuration or a rear actuator configuration. None of the prior arts presents the features as teaching in the present invention. Accordingly, it can be seen in the prior arts that there exists a need to provide a prosthetic limb incorporated with a plurality of sensing elements to detect the mechanical forces applied by the amputees' residual limb onto the sensing elements in order to determine the amputee's intention movement.

Summary of Invention

It is an objective of the present invention to provide a prosthetic limb incorporated with a sensory system comprising a plurality of sensing elements, preferably a multi-array sensing elements, for detecting user's intention movement and gait cycle including walking, sit to stand and stand to sit activities based on ground reaction force, and detection of muscles pressure based on voluntary contraction.

It is also an objective of the present invention to provide a prosthetic limb incorporated with a sensory system, which comprises a quadrilateral socket to provide total contact area of a stump with the socket and to enable user to move like a normal human movement.

It is yet an objective of the present invention to provide a controller which can classify the prosthetic limb motion based on the information from a sensor placed inside a prosthetic socket, which is derived from the muscle mechanical contraction and ground reaction forces.

It is yet a further objective of the present invention to provide a prosthetic limb incorporated with a sensory system having a plurality of sensing elements that is located strategically within the prosthetic socket to assist in determining the pressure of the stump in improving mechanical fit of the socket and soft tissue viability. It is also a further objective of the present invention to provide a prosthetic limb incorporated with a sensory system, which can ensure comfort and energy efficiency of the users. Accordingly, these objectives may be achieved by following the teachings of the present invention. The present invention relates to a prosthetic limb integrated with a sensory system, comprising of: a prosthetic socket for receiving an amputee stump; a lever arm connecting the prosthetic socket to an actuator for actuating a movement of the prosthetic limb; said sensory system comprising a plurality of a sensing elements mounted to the prosthetic socket for motion detection; and characterized in that: said prosthetic socket comprises a plurality of cavities at an inner surface of said prosthetic socket for placing the plurality of sensing elements configured for detecting the motion based on ground reaction force and muscle contraction; a controller connected to the plurality of sensing elements and the actuator for processing an output signal received from the plurality of sensing elements, and determining a user's intention movement. Brief Description of the Drawings

The features of the invention will be more readily understood and appreciated from the following detailed description when read in conjunction with the accompanying drawings of the preferred embodiment of the present invention, in which: Fig. 1 is a drawing showing an anterior wall and a posterior wall of an inner surface of a prosthetic socket.

Fig. 2 is a diagram showing a complete gait cycle from the first heel strike of one foot to another heel strike of the similar foot.

Fig. 3 is a diagram showing an output signal of one of a plurality of sensing elements (50 per. Mov. Avg.) with standard deviation for hamstring muscles of a prosthetic limb. Fig. 4 is a diagram showing an output signal of one of a plurality of sensing elements (50 per. Mov. Avg.) with standard deviation for quadriceps muscles of the prosthetic limb. Fig. 5 is a diagram showing a sensory system estimates a gait cycle of the prosthetic limb for hamstring muscles;

Fig. 6 is a diagram showing a sensory system estimates a gait cycle of the prosthetic limb for quadriceps muscles;

Fig. 7 is a graph showing ground reaction force for the prosthetic limb attached with a solid ankle cushion heel (SACH) foot, a single axis foot and a multi-axis prosthetic foot.

Fig. 8a is a graph showing pressure value of a residual limb in an assembly of the prosthetic limb that attached with the SACH prosthetic foot.

Fig. 8b is a graph showing pressure value of the residual limb in an assembly of the prosthetic limb that attached with the single axis prosthetic foot.

Fig. 8c is a graph showing pressure value of the residual limb in an assembly of the prosthetic limb that attached with the multi-axis prosthetic foot. Detailed Description of the Invention

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting but merely as a basis for claims. It should be understood that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the invention is to cover all modifications, equivalents and alternatives falling within the scope of the present invention as defined by the appended claims. As used throughout this application, the word "may" is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words "include," "including," and "includes" mean including, but not limited to. Further, the words "a" or "an" mean "at least one" and the word "plurality" means one or more, unless otherwise mentioned. Where the abbreviations or technical terms are used, these indicate the commonly accepted meanings as known in the technical field. For ease of reference, common reference numerals will be used throughout the figures when referring to the same or similar features common to the figures. The present invention will now be described with reference to Figs. 1 -8c.

The present invention presents a prosthetic limb integrated with a sensory system, comprising of: a prosthetic socket for receiving an amputee stump; a lever arm connecting the prosthetic socket (100) to an actuator for actuating a movement of the prosthetic limb; said sensory system comprising a plurality of a sensing elements (101 ) mounted to the prosthetic socket (100) for motion detection; and characterized in that: said prosthetic socket (100) comprises a plurality of cavities at an inner surface of said prosthetic socket (100) for placing the plurality of sensing elements (101 ) configured for detecting the motion based on ground reaction force and muscle contraction; a controller connected to the plurality of sensing elements (101 ) and the actuator for processing an output signal received from the plurality of sensing elements (101 ), and determining a user's intention movement.

In a preferred embodiment of the present invention, the plurality of the cavities is positioned at posterior and anterior wall of the inner surface of the prosthetic socket (100). The plurality of sensing elements (101 ) is mounted to the plurality of cavities for motion detection.

In a preferred embodiment of the present invention, the plurality of sensing elements (101 ) is a piezoelectric sensor.

In a preferred embodiment of the present invention, the plurality of cavities has a zig-zag arrangement at the inner surface of the prosthetic socket (100). In a preferred embodiment of the present invention, an electrode of the sensing element is connected to the controller through the opening at the end of each of the plurality of cavities. In a preferred embodiment of the present invention, the controller is a circuit board.

In a preferred embodiment of the present invention, the gait phase comprises heel strike, foot flat, toe-off, stair ascends, and sit to stand movements.

In a preferred embodiment of the present invention, the plurality of sensing elements (101 ) is mounted at the inner surface of the anterior wall of the prosthetic socket (100) for in contact with quadriceps muscles of a residual limb. The quadriceps muscles include posterior biceps femoris region.

In a preferred embodiment of the present invention, the plurality of sensing elements (101 ) is mounted at posterior wall of the inner surface of the prosthetic socket (100) for in contact with hamstrings muscles of a residual limb. The hamstrings muscles include anterior rectus femoris region.

The present invention also provides a method of producing the prosthetic limb movement by using the prosthetic limb integrated with the sensory system of the present invention, characterized by the steps of: transmitting information from the plurality of sensing elements (101 ) to the controller; estimating the gait phase using the controller, thereby creating the input signal based on the information received from the plurality of sensing elements (101 ); and sending the input signal from the controller to the actuator to produce the prosthetic limb movement.

In a preferred embodiment of the method of producing the prosthetic limb movement by using the prosthetic limb integrated with the sensory system, wherein the information detected by the sensing element is analysed by the controller based on maximum voluntary contraction, ground reaction force, stump pressure, and any combination thereof. Below is an example of the prosthetic limb integrated with a sensory system of the present invention from which the advantages of the present invention may be more readily understood. It is to be understood that the following example is for illustrative purpose only and should not be construed to limit the present invention in any way.

Examples

A prosthetic socket (100) of the present invention is configured for receiving the residual limb or residual stump. In a preferred embodiment, the prosthetic socket (100) can be made of various materials and in different sizes, but preferably custom-made for each amputee according to the shape and condition of the residual amputee stump and the amputee's mobility grade.

A lever arm connects the prosthetic socket (100) to an actuator for actuating a movement of the prosthetic limb. In a preferred embodiment, the prosthetic limb comprises the plurality of cavities, preferably a plurality of elongated cavities, for receiving the plurality of sensing elements (101 ). Each of the plurality of cavities has an opening at both ends for allowing the sensing element to pass through and connected to the controller. The prosthetic limb further comprises a prosthetic foot including a single-axis foot and a multi-axis foot, attached to the lever arm.

The prosthetic limb integrated with the sensory system is mainly used for detecting amputee's intention movement in order to achieve a more responsive gait including walking gait and heel strike. Said sensory system is a communication mechanism connecting the plurality of sensing elements (101 ) to the controller and the actuator. Referring to Fig. 1 , the plurality of sensing elements (101 ) is preferably mounted on inner surface of the anterior wall and posterior wall of the prosthetic socket (100) for in contact with quadriceps muscles and hamstrings muscles of the residual limb respectively. The plurality of sensing elements (101 ) is arranged in a zig-zag arrangement at each anterior wall and posterior wall of the prosthetic socket (100). Configuration of the plurality of cavities and the plurality of sensing elements (101 ) of the present invention able to provide sufficient and full contact area with the residual limb and aids in detecting the amputee's intention for movement by providing more accurate reading for estimation of the gait phase. In a preferred embodiment of the present invention, the prosthetic limb comprises eight sensing elements (101 ) mounted at the inner surface of the anterior and posterior prosthetic socket (100), respectively.

In a preferred embodiment of the present invention, the plurality of sensing elements (101 ) has an electrode and said electrode is connected to the circuit board through the opening at the end of the cavities of the prosthetic socket (100), to acquire an output amplitude voltage from the sensing elements (101 ). The openings of each of the cavity are then sealed preferably by silicone gel to prevent the air from entering to the socket. The circuit board is attached to lateral part of the prosthetic socket (100) and connected to an amplifier circuit and further connected to a DAQ card for recording the output signal of the sensing elements (101 ) via Lab View Software.

The plurality of sensing elements (101 ) sends information via the amplifier circuit to the controller. Said controller is preferably a microcontroller. In a preferred embodiment, the information is the measured interaction forces generated between the inner surface of the prosthetic socket (100) and the amputee residual limb, more particularly the amputee stump. The information is detected by the plurality of sensing elements (101 ) and then analysed by the controller based on a factor including Maximum Voluntary Contraction (MVC) and ground reaction force. The controller receives the information from the plurality of sensing elements (101 ) and estimates the gait cycle based on the information received. Having estimated the gait cycle, the controller determines the correct command for the actuator to produce the desired prosthetic limb movements. The command is sent as an input signal from the controller to the actuator. In a preferred embodiment, the gait cycle refers to the cycle from a first heel strike of one foot to another heel strike of the similar foot. Experimental trials on amputee

Maximum Voluntary Contraction for quadriceps muscles

The amputee is instructed to sit on a chair with 90 degree position. Another person places one hand on the end of the amputee's stump and pushes it downwards. The amputee needs to fight against the downward force as much as he could for about 3 seconds. The maximum voluntary contraction of the amputee's stump is observed based on bulged muscles of quadriceps. The sensing elements (101 ) in the socket detect the contraction of muscles and transmit the data to the controller and plotted against time using the Lab View software. All steps were repeated for about 3 seconds with 5 trials.

Maximum Voluntary Contraction for hamstrings muscles

The amputee is instructed to lie down on a bed with chest facing downward. Another person will place one hand on middle of the amputee's stump and push it downwards. The amputee is required to fight against the downwards force as much as he could for about 3 seconds. The maximum voluntary contraction of the amputee's stump is observed based on bulged muscles of hamstrings muscles. The sensing elements (101 ) in the prosthetic socket (100) detect the contraction of muscles and transmit the data to the controller and plotted against time using the Lab View software. All steps were repeated for about 3 seconds with 5 trials.

Gait cycle

The amputee is instructed to walk for a complete gait cycle including heel strike, foot flat and toe off. The data from the gait cycle is detected starting from the beginning of the heel strike to another heel strike. The plurality of sensing elements (101 ) detects muscle contract during heel strike, foot flat and toe off, wherein said data is transmitted to controller and analysed using the Lab View software. All steps are repeated for 10 trials. After about 10 trials, the amputee changes his prosthetic foot from SACH foot to the single axis and followed by the multi axis. The steps are repeated foe each type of foot. Experimental result

The information produced from the sensing element is transmitted to the controller and analysed by an identification process performed by a classifier of the controller. The information sent by the plurality of sensing elements (101 ) comprises sensor measurements made by the sensing elements (101 ) in the anterior and posterior regions of the prosthetic socket (100). Said information is analysed based on the plurality of factors comprising maximum voluntary contraction, ground reaction force and stump pressure. More parameter measurements are used in the present invention for both anterior and posterior regions provided useful information for estimating the intended movement of the amputee stump. A set of reference data is stored in the controller, to identify the direction and nature of the movement during different phase of the gait cycle. The output data from the sensing element is in voltage. The stump pressure value is determined by using the Formula 1 .

n F

r — — Formula 1

A

Wherein, the P refers to pressure; F refers to force; and A refers to area of the sensing elements (101 ).

A control algorithm in the controller could be further programmed to compare the information collected from the sensing element with the reference data stored in the controller to determine the intended movement of the prosthetic limb and then send the input signal to the actuator by adjusting the specific motion required by the controller, whether to flex or extend based on the information delivered from the sensing element.

Fig. 3 shows an output signal of one of the plurality of sensing elements (101 ) (50 per. Mov. Avg.) with standard deviation for the hamstring muscles. Fig. 4 shows an output signal of one of the plurality of sensing elements (101 ) (50 per. Mov. Avg.) with standard deviation for the quadriceps muscles. The output signal from the sensing element increased as the downwards forces were being applied onto the muscles as shown in the Figs. 3 and 4. Based on Figs. 3 and 4, the prosthetic limb integrated with the sensory system of the present invention able to provide a sensitive detection on the muscle contraction.

Referring to Fig. 2, one complete gait cycle is from the first heel strike of one foot to another heel strike of the similar foot. A gait cycle generally consists of 60% stance phase and 40% swing phase, but the percentages might differ according to amputees. Figs. 5 and 6 shows the sensory system estimates a gait cycle of the prosthetic limb for hamstring muscles and quadriceps muscle respectively. Referring to Fig. 5, the amputee's intention to perform heel strike is detected at 0% to 4% as it starts to produce a peak for a heel strike phase. At the midstance phase from 55% to 85%, the muscles start to produce a constant contraction as the full body weight will shift to both of the legs. Besides, as the amputee intended to toe off, the output signal started to decrease. Referring to Fig. 6, the first heel strike initiate the contracting of quadriceps muscles as the ankle foot was in flexion condition. At the mid stance phase which is 20% - 40%, the amputee has the intention to bear the full body weight and there is no change in the output data as the foot is fully in contact with the ground. In the middle of the gait cycle is the heel off phase at 40% - 50% as the amputees had an intention to raise the heel and the quadriceps initiate the contraction of it muscles when it change to swing phase. During the swing phase, output data of the quadriceps is low as the muscles did not contact with the ground and the amputee's intention to form another heel strike is detected which give the peak of the output signals data.

Fig. 7 shows a graph of ground reaction force versus percentage of stance phase between three different types of foots including a SACH foot, the single axis foot and the multi-axis foot. One gait cycle comprises of the stance phase and the swing phase where the stance phase refers to a phase from the heel strike to toe off. Graph of ground reaction force,which resembled a butterfly diagram, has two peaks of the force value which indicate heel strike. The minimum peak of the graph shows a midstance phase where total body weight of the amputee was applied to the force plate for force absorption and ready for body propulsion. Based on the Fig. 7, the heel strike phase (at about 20%) has a different force of ground reaction force between the three types of foots. The prosthetic socket (100) integrated with the the plurality of sensing elements (101 ) of the present invention able to determine performance consistency of the prosthetic limb with the three different types of foots.

Interaction between the residual limb and the prosthesis socket can lead to high stump pressure. Figs. 8a, 8b and 8c are graphs showing pressure value of the residual limb in an assembly of the prosthetic limb that attached with the SACH prosthetic foot, the single axis prosthetic foot and the multi-axis prosthetic foot respectively. The plurality of sensing elements (101 ) produces the output signal as soon as the amputee started to walk. During the first phase of gait cycle, when the amputee started to perform heel strike, the quadriceps muscles would contract and the pressure value of the quadriceps muscles will be higher than the hamstring muscles. The prosthetic limb integrated with the sensory system of the present invention able to determine appropriate pressure suitable to be applied on the amputee's residual limb based on the stump pressure analysis. Different stump pressure values are observed for the prosthetic having different type of prosthetic foots attached to the prosthetic socket (100) as shown in Table 1 .

Table 1 : Maximum and minimum stump pressure value applied onto quadriceps and hamstring muscles for prosthetic limb having different type of foots.

Types of foot Maximum Pressure (Pa) Minimum Pressure (Pa)

Quadriceps Hamstring Quadriceps Hamstring

SACH -3.019 1.796 -2.669 -4.719

Single Axis -1.171 -1.977 -4.224 -2.804

Multi axis -2.411 0.689 -4.515 -5.130 With reference to Table 1 , single axis foot has the least muscles pressure with -1 .171 Pa of quadriceps muscles and -1 .977 Pa of hamstring muscles. The amputee used to wear the single axis as he can bear all the pressure on his stump. Multi-axis foot was one of the advance designs of prosthetic foot as he had an energy storing power of the carbon fibre foot. Pressure value of the multi axis foot on the quadriceps and hamstring muscles were -2.41 1 Pa and 0.689 Pa respectively. Last, SACH food has the most pressure on the hamstring muscles with 1 .796 Pa. These types of foot did not have any axis on the ankle part of the foot as it is rigid. Thus, single axis was the best foot with the least pressure acted on the stump.

Although the present invention has been described with reference to specific embodiments, also shown in the appended figures, it will be apparent for those skilled in the art that many variations and modifications can be done within the scope of the invention as described in the specification and defined in the following claims.

Description of the reference numerals used in the accompanying drawings according to the present invention:

Reference

Description

Numerals

100 Prosthetic socket

101 A plurality of sensing elements

Claims

I/We claim:

A prosthetic limb integrated with a sensory system, comprising of:

a prosthetic socket (100) for receiving an amputee stump;

a lever arm connecting the prosthetic socket (100) to an actuator for actuating a movement of the prosthetic limb;

said sensory system comprising a plurality of a sensing elements (101 ) mounted to the prosthetic socket (100) for motion detection;

and characterized in that:

said prosthetic socket (100) comprises a plurality of cavities at an interior of said prosthetic socket (100) for placing the plurality of sensing elements (101 ) configured for detecting the motion based on ground reaction force and muscle contraction;

a controller connected to the plurality of sensing elements (101 ) and the actuator for processing an output signal received from the plurality of sensing elements (101 ), and determining a user's intention movement.

The prosthetic limb integrated with the sensory system according to claim 1 , wherein the plurality of cavities is positioned at posterior and anterior wall of the interior of the prosthetic socket (100).

The prosthetic limb integrated with the sensory system according to claim 1 , wherein the plurality of sensing elements (101 ) is a piezoelectric sensor.

The prosthetic limb integrated with the sensory system according to claim 1 , wherein the plurality of cavities is arranged in a zig-zag arrangement.