1. Field
The present invention relates generally to a method for a combined active and passive leg prosthesis system and a combined active and passive leg prosthesis system for replacing a missing lower extremity of an individual to perform a gait cycle (take a step) by the leg prosthesis system. The leg prosthesis system has at least one movable joint and a drive unit to drive the movable joint.
More specifically, the present invention concerns a leg prosthesis system intended for a person who has a leg amputated above or below the knee joint. Thus the system may comprise an articulated ankle joint or both an articulated knee joint and an articulated ankle joint.
2. Description of the Related Art
A leg prosthesis system of the type stated above can be adjusted and used by wearers of a prosthesis at different amputation levels.
A person uses his entire body to perform a movement. A gait cycle, that is two steps, is divided into a support phase and a swing phase. The support phase is when the foot of the leg is in contact with the ground, and during the swing phase the foot swings freely in the air. In walking, one leg swings forward with a flexion in hip, knee and ankle joint while at the same time the arm on the opposite side swings forward. The arm on the same side swings backward and helps to increase the forward force and promotes balance. When the foot of the leg touches the ground, heel touching ground, the weight of the body is supported and the forward fall is braked. The leg supports the body and drives it forward until the next leg takes over in placing the heel on the ground.
If one or more joints and muscles are missing, in this case in lower extremities, there will be imbalance and more energy will be consumed. The more joints that are missing and the higher the amputation level, the more energy is required to perform a gait cycle.
A gait cycle, in this case for a leg prosthesis system, can be identified as the movement performed by leg prosthesis system from placing the heel on the ground to the next placing of the heel on the ground with the same leg.
A leg prosthesis system according to the invention can be used to facilitate different types of gait cycles for the prosthesis wearer, for instance to walk at varying speeds, to climb or descend stairs or walk on inclined surfaces.
With the leg prostheses that are available on the market, it is difficult or even impossible for a leg prosthesis wearer to perform certain types of gait cycles.
The leg prosthesis systems that are being sold today are completely passive, that is no external energy is supplied to the prosthesis in addition to the prosthesis wearer's kinetic energy. A passive prosthesis can only lock, dampen and decelerate a movement. With a good passive leg prosthesis system according to prior art technique, a prosthesis wearer can handle most everyday situations, such as sit down, stand, walk on flat ground and descend stairs and slopes.
However, the energy that can be supplied to a passive leg prosthesis system by the prosthesis wearer is in most cases not sufficient to perform more energy-consuming gait cycles, such as stand up from a sitting position, quick increase of speed or climb a staircase or a steep slope. Another problem is to ensure ground clearance to reduce the risk of stumbling.
The manufacture and development of active leg prosthesis systems has only started recently, that is prostheses comprising motors and power sources. By supply of power, the leg prosthesis system helps the prosthesis wearer to perform certain gait cycles such as climb a staircase.
The technique chosen to supply power in active leg prosthesis systems, according to prior art technique, has resulted in problems, such as high movement of inertia in moving the movable joints of the leg prosthesis system. All parts have to be driven when performing a gait cycle and the energy consumption in the leg prosthesis system will be high.
There is thus a need to improve prior art and many of the leg prostheses that are currently available on the market.
An object of the present invention is to provide a leg prosthesis system which eliminates one of the problems described above in a simple and effective manner.
Another object of the invention is to provide a method of performing gait cycles with improved performance by means of a leg prosthesis.
The above objects and other objects that will be evident from the following description are achieved by a device and a method according to the claims.
A leg prosthesis system according to the invention comprises at least one movable joint which can be switched between being actively driven or being passively braked. Furthermore the leg prosthesis system comprises a control system for controlling the active and the passive unit in the movable joint. A number of transducers and sensors arranged on the leg prosthesis system supply input data to the control system, and a power source supplies power to control system, motors and transducers.
A leg prosthesis system according to the invention comprising control system, power source and transducers can be provided with an ankle joint comprising an active and a passive unit and/or a knee joint comprising an active and a passive unit.
The leg prosthesis system according to the invention can also be adjusted to a prosthesis wearer who lacks both lower extremities, that is who is double-leg-amputated. Each leg prosthesis system may, but need not, comprise one common or two separate or communicating control systems.
According to one aspect of the present invention, a combined active and passive leg prosthesis system is provided to replace a missing lower extremity of an individual to perform a gait cycle by means of the leg prosthesis system. The leg prosthesis system comprises at least one movable joint and an active drive unit to supply power and drive the movable joint. Moreover the active drive unit is disconnectable from driving relation with the movable joint. By the active drive unit being disconnectable, low moment of inertia can be achieved in the movable joint. The forward force in the natural swinging motion created by the wearer's body is then sufficient to move the joint. When the joint is disconnected from driving, it is possible to brake the movement of the joint when required. Braking of the movable joint performed by a passive brake unit may be varied in braking force and be varied from a completely unbraked (freely swinging) to a fully braked (locked) joint. The interaction between active driving and passive braking of a joint gives a prosthesis wearer a good possibility of performing gait cycles with improved performance. An active drive unit which can be run in two directions makes it possible to perform a movement in both directions of the joint if, in addition, it is possible to disconnect the active drive so as to perform a free movement of the joint which can be controlled by the passive brake unit. Active and passive movements are a natural part of the gait pattern, which means that a system having such possibilities can more easily imitate the energy-saving way of the human body to perform movements.
Preferably, the active drive unit of the leg prosthesis system is disconnected from driving relation with the movable joint during part of the gait cycle. For instance, the active drive unit can be disconnected during both the swing and the support phase.
Preferably, a passive brake unit acts on the movement of the joint when the active drive unit is disconnected from the joint. By using the passive brake unit when the active drive unit is disconnected, the energy-saving way of the human body to perform movements can be imitated.
Preferably, the leg prosthesis system according to the invention also comprises a control system adapted to control the active drive unit of the movable joint. The control system makes it possible to control direction, force and speed of the active drive unit. The control system also makes it possible to activate driving only at points of time when the leg prosthesis system needs supply of extra power.
Preferably, the control system according to the invention is also adapted to control the passive brake unit of the movable joint. A control system can be used to adjust the brake force from a completely unbraked (freely swinging) to a fully braked (locked) joint. If the control system controls both the active drive unit and the passive brake unit, a number of advantages can be achieved since the leg prosthesis system according to the invention can use the properties of both the active drive unit and the passive brake unit and also the possibility of switching between driving and braking the movable joint.
Preferably the leg prosthesis system comprises both a movable knee joint and a movable ankle joint. A prosthesis wearer who lacks a knee joint, that is who is amputated above the knee joint, needs a leg prosthesis which has both knee joint and ankle joint. A prosthesis wearer who lacks both lower extremities, that is who is double-leg-amputated, needs a leg prosthesis system with at least two movable joints.
Preferably, the knee joint and the ankle joint are each arranged with a disconnectable active drive unit and a passive brake unit as well as a common control system to control the movements of knee joint and ankle joint in a synchronized manner. In double amputation, two separate or communicating control systems may, but need not, be used. A leg prosthesis system which is made up in this manner can use active and passive techniques for both knee joint and ankle joint. When besides a control system coordinates the movement of the knee joint and the ankle joint, considerable improvements can be achieved compared with a completely passive prosthesis, but also compared with an active prosthesis which comprises a knee joint or a knee joint and an ankle joint which are active but not coordinated with a common control system.
Preferably the leg prosthesis system according to the invention comprises transducers for input data to the control system. Input data can be sent to the system from, for instance, a key set, transducers, sensors (speed, position, angle, pressure), nerve sensors etc.
Preferably, the knee joint and the ankle joint move by switching between the associated active drive unit and passive brake unit during a gait cycle.
A leg prosthesis system according to the invention with a movable knee joint and ankle joint which controls the direction, force and speed of the current control system for the active drive unit and the brake force for the passive brake unit in each joint independently of the other joint thus ensures an optimized and coordinated movement of the leg prosthesis system.
The control system may use information from the entire leg prosthesis system, for instance information from the knee joint when the ankle joint is to be controlled and vice versa.
According to one aspect of the present invention, a method is provided for performing a gait cycle with a combined active and passive leg prosthesis system, which replaces a lacking lower extremity of an individual. The leg prosthesis system comprises at least one movable joint and an active drive unit which supplies power and drives the movable joint. Moreover, the active drive unit is disconnected from driving relation with the movable joint during part of the gait cycle. By disconnecting the drive unit, it is, for instance, possible to use the natural swinging movement during the swing phase in walking. Thus the drive unit need not be adjusted to accomplish movements equivalent to free swinging. The active drive unit can instead be optimized for driving, and energy saving can be ensured since the drive unit is not activated during the entire time of use of the prosthesis.
Preferably the method comprises braking the movement of the joint, with a passive brake unit of the leg prosthesis system according to the invention, when the active drive unit is disconnected from the joint. When the active drive unit is disconnected and the passive brake unit is connected, the prosthesis can move freely by the forward force in the joint in question created by the wearer's body, or the movement of the joint can be braked.
Preferably the method comprises controlling of the drive unit and/or the brake unit of the movable joint by a control system of the leg prosthesis system according to the invention. By using a control system, it is possible to disconnect driving and/or activate the passive brake unit at the correct point of time or taking the outer circumstances into consideration. The braking in the leg prosthesis system is a property which advantageously is coordinated with the driving of the system to achieve a good result.
Preferably the method comprises supplying input data to the control system from transducers of the leg prosthesis system. Input data is sent, for instance, from a key set, transducers, sensors (which record speed, position, angle, pressure), nerve sensors etc.
The method preferably comprises controlling in a synchronized manner the movements of a knee joint and an ankle joint of the leg prosthesis system. The knee joint and the ankle joint each have a disconnectable active drive unit and a passive brake unit as well as a common control system. In a leg prosthesis with both knee joint and ankle joint, improved possibilities are achieved for the prosthesis wearer since a control system which is common to both joints can coordinate the movements of knee joint and ankle joint.
The knee joint and the ankle joint preferably move by switching between the associated drive unit and brake unit during a gait cycle.
Preferably the method comprises controlling, separately or in a communicating manner, the movements of at least two movable joints of leg prosthesis systems adjusted to a double-leg-amputated prosthesis wearer.
The control system may use information from the entire leg prosthesis system, for instance information from the knee joint when the ankle joint is to be controlled and vice versa.
The method preferably comprises driving and braking of knee joint and ankle joint, respectively, during a gait cycle.
The invention will now be described in more detail with reference to the accompanying drawings, in which
Most of the people with an amputated leg have lost their leg below the knee joint. The present leg prosthesis system and/or method can be used by prosthesis wearers who need a prosthesis with both knee joint and ankle joint, but the invention can also be used for a prosthesis with only an ankle joint or only a knee joint. The leg prosthesis system and/or the method can also be used by prosthesis wearers who lack both lower extremities, that is who are double-leg-amputated and need a leg prosthesis system with at least two movable joints. One common or two separate and/or communicating control means may be used.
To climb a staircase or slope, as illustrated in
When descending a staircase or slope, as illustrated in
With a leg prosthesis system 1 and/or a method according to the invention, the disconnectable active drive unit 4, 4′ of a knee joint or ankle joint makes it possible for the system and the method to use a combination of active and passive operation. The control system 15 can select the optimal method of performing a movement. The knee joint 2 can be active while the ankle joint 3 is passive and vice versa. For example, the knee joint 2 can perform the swinging movement in the swing phase using only the passive brake unit 2 while the ankle joint 3 uses its active drive unit for dorsal flexion of the foot in order to create extra ground clearance.
For activation of the drive unit 4, according to
According to
The foot 14 with the ankle joint 3 according to
A movement of the ankle joint 3 in the passive state actuates the piston 9′ via the link arm 10′, the hydraulic oil in the cylinder 16′ is pressed through the valve 8′ of the brake unit 5′ and the brake force can be adjusted by varying the opening degree of the valve 8′. The braking can be varied in brake force and can be varied from a completely unbraked (freely swinging) to a fully braked (locked) ankle joint 3.
If the leg prosthesis system 1 merely comprises a foot prosthesis 3 according to the invention, for instance at an amputation level below the knee joint, the foot prosthesis still needs a battery 11′ and a control unit 15′ which may then be arranged, for instance, around the interconnecting element or on a leg-enclosing socket.
It goes without saying that the invention should not be considered limited to the embodiments described above and illustrated in the drawings, with the described variants and alternatives, and can be modified additionally in various ways within the scope of the appended claims.
Number | Date | Country | Kind |
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0500882-6 | Apr 2005 | SE | national |
This application is a continuation application of U.S. patent application Ser. No. 13/846,695, entitled COMBINED ACTIVE AND PASSIVE LEG PROSTHESIS SYSTEM AND A METHOD FOR PERFORMING A MOVEMENT WITH SUCH A SYSTEM, and filed Mar. 18, 2013, which is a continuation application of U.S. patent application Ser. No. 11/887,374, entitled COMBINED ACTIVE AND PASSIVE LEG PROSTHESIS SYSTEM AND A METHOD FOR PERFORMING A MOVEMENT WITH SUCH A SYSTEM, and filed Jul. 30, 2009, which is a national stage entry of International Patent Application No. PCT/SE2006/000445, entitled COMBINED ACTIVE AND PASSIVE LEG PROSTHESIS SYSTEM AND A METHOD FOR PERFORMING A MOVEMENT WITH SUCH A SYSTEM, and filed Apr. 18, 2006, the entireties of which are incorporated by reference herein and should be considered a part of this specification.
Number | Date | Country | |
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Parent | 13846695 | Mar 2013 | US |
Child | 14743021 | US | |
Parent | 11887374 | Jul 2009 | US |
Child | 13846695 | US |