U.S. patent application number 16/377139 was filed with the patent office on 2019-08-01 for method for controlling an orthopedic joint device, and orthopedic joint device.
This patent application is currently assigned to OTTOBOCK SE & CO. KGAA. The applicant listed for this patent is OTTOBOCK SE & CO. KGAA. Invention is credited to Martin PUSCH, Christian WILL.
Application Number | 20190231562 16/377139 |
Document ID | / |
Family ID | 48793159 |
Filed Date | 2019-08-01 |
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United States Patent
Application |
20190231562 |
Kind Code |
A1 |
PUSCH; Martin ; et
al. |
August 1, 2019 |
METHOD FOR CONTROLLING AN ORTHOPEDIC JOINT DEVICE, AND ORTHOPEDIC
JOINT DEVICE
Abstract
The invention relates to a method for controlling an orthopaedic
joint device of a lower extremity. The joint device has an upper
part (2) and a lower part (3) mounted in a hinged manner on the
latter. Arranged between the upper part (2) and the lower part (3)
is an energy converter (5) by which, during walking, kinetic energy
from the relative movement between the lower part (3) and the upper
part (2) is converted or stored and supplied again to the joint in
order to support the relative movement, wherein kinetic energy
within one movement cycle is converted and/or stored and, within
the same movement cycle, is supplied again as kinetic energy to the
joint device (1) in a controlled manner and staggered in time.
Inventors: |
PUSCH; Martin; (Duderstadt,
DE) ; WILL; Christian; (Gottingen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OTTOBOCK SE & CO. KGAA |
Duderstadt |
|
DE |
|
|
Assignee: |
OTTOBOCK SE & CO. KGAA
Duderstadt
DE
|
Family ID: |
48793159 |
Appl. No.: |
16/377139 |
Filed: |
April 5, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14412418 |
Dec 31, 2014 |
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PCT/EP2013/001957 |
Jul 3, 2013 |
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16377139 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2/70 20130101; A61F
2002/704 20130101; A61F 2002/5032 20130101; A61F 2/60 20130101;
A61F 2002/503 20130101; A61F 2002/6845 20130101; A61F 2002/5035
20130101; A61F 2002/748 20130101; A61F 2002/6818 20130101; A61F
2002/701 20130101; A61F 2/66 20130101; A61F 2/605 20130101; A61F
2002/741 20130101; A61F 2002/5072 20130101; A61F 2002/745 20130101;
A61F 2/68 20130101; A61F 2002/5043 20130101; A61F 2002/708
20130101; A61F 2002/5006 20130101; A61F 2/64 20130101; A61F
2002/5033 20130101 |
International
Class: |
A61F 2/68 20060101
A61F002/68; A61F 2/60 20060101 A61F002/60; A61F 2/64 20060101
A61F002/64; A61F 2/66 20060101 A61F002/66 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 3, 2012 |
DE |
102012013140.2 |
Claims
1-32. (canceled)
33. A method for controlling an orthopedic joint device of a lower
extremity, the orthopedic joint device having an upper part and a
lower part mounted in an articulated manner thereon, the method
comprising: providing an energy conversion device arranged between
the upper part and the lower part, the energy conversion device
comprising a hydraulic cylinder with a piston arranged on a piston
rod, and a spring arranged within one of the first and second
chambers, the piston separating the hydraulic cylinder into a first
chamber and a second chamber, a volume of the first chamber being
reduced during a flexion movement of the lower part relative to the
upper part and increased during an extension movement of the lower
part relative to the upper part, the spring being loaded during the
flexion movement and relaxed during the extension movement;
converting and storing kinetic energy from relative movement
between the lower part and the upper part with the energy
conversion device; and feeding back the kinetic energy to the
orthopedic joint device with the energy conversion device during a
stance phase to assist with the extension movement; wherein within
a movement cycle, kinetic energy is converted and stored and,
within the same movement cycle, is fed back to the orthopedic joint
device in a controlled manner after a time delay such that the
energy feedback does not occur immediately after converting and
storing of the kinetic energy.
34. The method as claimed in claim 33, further comprising feeding
back the kinetic energy during at least one of initiation of a
swinging phase to assist the flexion movement of the orthopedic
joint device, after reaching a maximum flexion angle to assist the
extension movement, and after the flexion movement following an
initial heel contact to assist the extension movement.
35. The method as claimed in claim 33, wherein the kinetic energy
is at least one of converted and stored during a flexion movement,
the method further comprising feeding back the kinetic energy to
initiate the swinging phase to at least one of assist the flexion
movement and to maintain a bending velocity after a toe lift
off.
36. The method as claimed in claim 33, wherein the kinetic energy
is at least one of converted and stored after initiation of a
swinging phase, the method further comprising feeding back the
kinetic energy to assist a flexion movement of the orthopedic joint
device after reaching a maximum flexion velocity.
37. The method as claimed in claim 33, wherein the kinetic energy
is at least one of converted and stored before reaching an
extension stop limit, the method further comprising feeding back
the kinetic energy to at least one of initiate and assist a flexion
movement of the orthopedic joint device.
38. The method as claimed in claim 1, further comprising feeding
back the kinetic energy during a swinging phase of the joint device
to increase or maintain the extension movement.
39. The method as claimed in claim 33, wherein the kinetic energy
is stored during at least one of a standing phase at a beginning of
a standing phase flexion with heel loading, before reaching an
extension stop limit, and after initiating the standing phase
flexion with forefoot loading.
40. The method as claimed in claim 33, wherein the kinetic energy
is converted and stored with an initial heel impact, the method
further comprising feeding back the kinetic energy as part of at
least one of initiating and assisting a flexion movement of the
orthopedic joint device.
41. The method as claimed in claim 33, wherein less of the kinetic
energy is supplied to the orthopedic joint device with increasing
walking speed.
42. The method as claimed in claim 33, wherein the converted
kinetic energy is completely fed back to the orthopedic joint
device in the movement cycle.
43. The method as claimed in claim 1, wherein at least one of the
converting and storing of the kinetic energy is carried out only in
predetermined phases during the movement cycle.
44. The method as claimed in claim 33, wherein a supply of stored
kinetic energy is converted and fed back to assist the relative
movement in the controlled manner.
45. The method as claimed in claim 33, wherein a supply of stored
kinetic energy is changed by energy from the spring.
46. The method as claimed in claim 33, wherein the energy is stored
in an energy store, the energy store being assigned an actuator,
the actuator to fill the energy store to a minimum level if the
relative movement is not sufficient.
47. The method as claimed in claim 46, wherein the energy store is
assigned a releasing device, the releasing device to release the
kinetic energy from the energy store.
48. The method as claimed in claim 1, wherein the kinetic energy
fed back is dependent upon at least one of the following criteria:
an angular position of the upper part in relation to the lower
part; a position of at least one of the upper part and the lower
part in space; an angular velocity of at least one of the upper
part and the lower part; a relative velocity between the upper part
and the lower part; a loading situation; and an acceleration of at
least one of the upper part and the lower part.
49. The method as claimed in claim 48, wherein the kinetic energy
is stored with the spring and is fed back from the spring dependent
upon at least one of the criterion recited in claim 48.
50. The method as claimed in claim 33, further comprising adjusting
a point in time of an intervention of the energy conversion device
to change at least one of an amount of kinetic energy to be
converted and an amount of kinetic energy supplied.
51. The method as claimed in claim 46, further comprising charging
the energy store by an actuator if the energy conversion device is
not active on account of the relative movement between the upper
part and the lower part.
52. The method as claimed claim 1, wherein the relative movement is
influenced by a damper device.
53. The method as claimed in claim 33, wherein feeding back the
kinetic energy to the orthopedic joint device with the energy
conversion device occurs only during the stance phase.
54. The method as claimed in claim 33, wherein feeding back the
kinetic energy also occurs after extension during the stance phase
to assist with flexion movement of the lower part relative to the
upper part.
55. A method of controlling an orthopedic joint device of a lower
extremity, the orthopedic joint device having an upper part and a
lower part mounted in an articulated manner thereon, the method
comprising: providing an energy store and an energy conversion
device arranged between the upper part and the lower part;
converting kinetic energy from relative movement between the lower
part and the upper part with the energy conversion device; storing
the converted kinetic energy from the energy conversion device in
the energy store as stored energy; and feeding back the stored
energy to the orthopedic joint device with the energy conversion
device during a stance phase to assist with an extension movement
of the lower part relative to the upper part by supplying the
stored energy from the energy store to the energy conversion
device; wherein within a movement cycle, kinetic energy is
converted and stored and, within the same movement cycle, is fed
back as the stored energy to the orthopedic joint device in a
controlled manner after a time delay such that the energy feedback
does not occur immediately after converting and storing of the
kinetic energy, and the stored energy available for feeding back to
the conversion device is supplemented by the energy store.
56. A method for controlling an orthopedic joint device of a lower
extremity, the orthopedic joint device having an upper part and a
lower part mounted in an articulated manner thereon, the method
comprising: providing an energy conversion device arranged between
the upper part and the lower part, the energy conversion device
comprising a hydraulic cylinder with a piston arranged on a piston
rod, the piston separating the hydraulic cylinder into a first
chamber and a second chamber, a volume of the first chamber being
reduced during a flexion movement of the lower part relative to the
upper part and increased during an extension movement of the lower
part relative to the upper part; converting and storing kinetic
energy from relative movement between the lower part and the upper
part with the energy conversion device; and feeding back the
kinetic energy to the orthopedic joint device with the energy
conversion device during a stance phase of walking in order to
assist with the extension movement; wherein within a gait cycle,
kinetic energy is converted and stored and, within the same gait
cycle, is fed back to the orthopedic joint device in a controlled
manner after a time delay such that the energy feedback does not
occur immediately after converting and storing of the kinetic
energy, and the energy feedback occurs only during specific phases
of the gait cycle.
Description
[0001] The invention relates to a method for controlling an
orthopedic joint device of a lower extremity and also to an
orthopedic joint device as such; the joint device has an upper part
and a lower part mounted in an articulated manner thereon; arranged
between the upper part and the lower part is a damping device, by
way of which the extension damping and/or the flexion damping of
the pivoting movement is brought about, kinetic energy from the
relative movement between the lower part and the upper part being
converted and stored and fed back to the joint during the walking
in order to assist the relative movement.
[0002] Orthopedic joint devices of a lower extremity are for
example orthoses or prostheses. In particular in the case of
prostheses, which replace a natural knee joint, it is advantageous
and intended that active influencing of the flexion and extension
resistance takes place in the course of the movement cycle, in
order to adapt the behavior of the joint device to the movement
behavior or to other influences.
[0003] In addition, there are motor-driven prostheses or orthoses,
the drive motors of which serve the purpose of executing a flexion
or extension of the respective joint device.
[0004] WO 2007/025116 A2 describes a prosthetic device with an
electronically controlled prosthetic knee with a regenerative
braking device. In certain situations, the kinetic energy that
exists during walking is converted into electrical energy and
stored. In other situations it is provided that the gait is
assisted or completely controlled. An electronic control system is
provided in order to control the operation of the prosthetic device
and distribute electrical energy that is generated. Excess
electrical energy can be stored in a storage battery or capacitor
and called upon for movement assistance at a suitable point in
time. The energy storage devices in the case of prostheses or
orthoses are large and heavy, in order to have adequate capacity to
allow effective movement assistance to take place. In addition,
there is the possibility that the active displacement of the upper
part in relation to the lower part by correspondingly powerful
drives brings the user into situations over which he or she no
longer has control.
[0005] EP 439 028 B1 describes a swivel connection between two
parts of an orthopedic aid in the form of a polycentric prosthetic
knee joint, in the case of which a link member is designed to be
variable in length under the effect of an external force. The
changing of the length of the link member may be of a
spring-elastic form, so that the link member resumes its original
length immediately after the external force is reduced or
ceases.
[0006] The object of the present invention is therefore to provide
a method and a device with which it is possible to achieve an
improvement of the gait pattern without the user being put at risk
and having to bear a heavy joint device.
[0007] This object is achieved according to the invention by a
method with the features of the main claim and an orthopedic joint
device with the features of the alternative independent claim.
Advantageous configurations and developments of the invention are
presented in the respectively dependent subclaims, the description
and the figures.
[0008] The method according to the invention for controlling an
orthopedic device of a lower extremity, in the case of which the
joint device has an upper part and a lower part mounted in an
articulated manner thereon and between the upper part and the lower
part there is arranged an energy conversion device, by way of which
kinetic energy from the relative movement between the lower part
and the upper part is converted and/or stored and fed back to the
joint during the walking in order to assist the relative movement,
provides that, within a movement cycle, kinetic energy is converted
and/or stored and, within the same movement cycle, is fed back to
the joint device after a time delay as kinetic energy. In a typical
movement cycle of an orthopedic joint device of a lower extremity,
that is to say in a typical stepping cycle, there are phases in
which excess energy has to be converted, but also phases in which
assistance with kinetic energy is appropriate. It is therefore
provided that excess energy that is stored or converted and stored
for decelerating a component of the joint device is fed back at a
suitable point in the same stepping cycle, there being a time delay
between the storing or converting and storing and the renewed
supplying as kinetic energy, that is to say the return does not
follow on immediately after the storage. On account of the
supplying of the converted or stored energy in the same movement
cycle, a large storage battery or capacitor is unnecessary, since
there are only relatively small amounts of energy. As a result,
weight is saved and the joint device can be kept lightweight. The
device for converting and/or storing kinetic energy may be formed
as part of a damper device and bring about part of the extension
damping and/or the flexion damping of the pivoting movement when
energy is converted or stored. The device may be designed as a
hydraulic damper and/or a pneumatic damper; likewise, a
configuration as a generator may be provided.
[0009] Combinations of the devices described above with one another
are also possible. The device for converting and/or storing kinetic
energy may be provided along with conventional damper devices. The
other damping components, generally pneumatic or hydraulic dampers,
continue to be retained, but either an energy store or a generator
that can be switched over to operate as a motor is additionally
provided in order to take kinetic energy from the system or supply
it to the system at the suitable points within the movement. On
account of the fact that the hydraulic or pneumatic damping system
dissipates a large proportion of the energy, the system for
assisting the movement can be kept small and lightweight. The point
in time of the energy conversion and return is established by way
of a control device.
[0010] A development of the invention provides that kinetic energy
is converted and/or stored during an extension movement. The
renewed supplying of kinetic energy may take place in the
initiation of the swinging phase to assist the swinging phase
flexion. Likewise, kinetic energy may be fed back after the lifting
off of the toe ("toe off") during the step to maintain the flexion
velocity. It is also provided that, after reaching the maximum
flexion angle, which may be ascertained for example through a
reversal of movement or by a velocity sensor, energy is supplied to
assist the extension movement. Renewed supplying of the kinetic
energy may also take place after the flexion movement following the
initial heel contact, that is to say the standing phase flexion, to
assist the extension movement. It is possible in principle that the
supplying only takes place in a single phase of the stepping
movement; as an alternative to that, supplying of kinetic energy
may take place at a number of phases or all the phases described or
points in time of the stepping movement.
[0011] Furthermore, it may be provided that kinetic energy is
converted and/or stored during the flexion movement and is fed back
for initiating the swinging phase to assist the flexion movement
and/or to maintain the bending velocity after the lifting off of
the toe. It may therefore be provided that the kinetic energy is
converted and/or stored after initiation of the swinging phase and
is only fed back to assist the bending movement after reaching the
maximum flexion velocity. The reaching of the maximum flexion
velocity may be ascertained by a velocity sensor or an acceleration
sensor.
[0012] The extension movement is generally decelerated before
reaching the maximum extension, in order to reduce the impulse that
there is when striking against the extension limit stop occurs
without deceleration. This kinetic energy may be converted and/or
stored and fed back for initiating and/or assisting the flexion of
the joint device. During the swinging phase of the joint device,
kinetic energy can be supplied to increase or maintain the
extension velocity, in order to facilitate and assist the forward
extension of the lower part.
[0013] It is also provided that kinetic energy is converted and/or
stored during the standing phase at the beginning of the standing
phase flexion with heel loading, before reaching the extension stop
limit and/or after initiating the standing phase flexion with
forefoot loading. In particular, the kinetic energy may be
converted and/or stored with the initial heel impact and fed back
for initiating and/or assisting the flexion movement after reaching
an extension stop limit.
[0014] With increasing walking speed, it may be provided that less
kinetic energy is supplied to the joint, in order not to boost the
system itself and thereby make the user of the orthopedic joint
device walk faster and faster.
[0015] The kinetic energy may be converted into electrical energy
and buffer-stored or converted into potential energy and
buffer-stored, for example by charging an energy store, for example
a spring or a hydraulic or pneumatic pressure accumulator.
[0016] It is also provided that the converted energy is completely
fed back to the joint device in one movement cycle, so that there
is no storage of the converted energy beyond the movement cycle. As
a result, it is ensured that only the energy that exists and is
converted during the one movement cycle can be fed back to the
system as kinetic energy. This may take place by providing that,
after the detected return of a characteristic variable of the
movement cycle, the energy stored until then is dissipated or the
amount of energy over the last movement cycle is continually
checked.
[0017] Furthermore, it may be provided that the storage and/or
conversion of the kinetic energy is only carried out in
predetermined phases during a movement cycle, that is to say that
the energy conversion device does not work constantly to convert
part of the kinetic energy from the movement, store it or feed it
back to the joint device as kinetic energy. For this purpose,
either certain movement phases in which conversion, storage or
return always take place, for example by way of a mechanical or
electrical control device, are established or the points in time
and time periods in which conversion, storage or return take place
are established on the basis of an analysis of the movement from
characteristic variables for each movement cycle or for a
predetermined or calculated number of movement cycles. This may
take place for example by way of an electronic control device.
[0018] A development of the method according to the invention in
which, during pivoting of the upper part in relation to the lower
part, mechanical work from the relative movement is converted and
stored in at least one energy store and fed back to the joint
device after a time delay, in order to assist the relative
movement, provides that the stored energy is converted back and the
supply of mechanical work for and during the assistance of the
relative movement takes place in a controlled manner. When energy
is released from an energy store, for example a spring, according
to the prior art the stored energy is supplied to the joint device,
that is to say the system comprising the upper part and the lower
part and the articulated mounting, as a sudden surge, so that a
great amount of energy is introduced over a very short time period.
It is provided that the stored energy is fed back to the system,
and converted into mechanical work and assistance for the
displacement of the upper part in relation to the lower part, in a
controlled manner, in order to assist the movement over a longer
time period, so that a movement of the prosthetic or orthotic
device that is approximated to the natural sequence of movements
can take place. According to the prior art, an adaptation to
changed gait patterns, the speeds or different patients can only be
carried out with extremely great effort, in that specifically
adapted springs are used, which is impractical for daily use.
[0019] According to the invention, on the other hand, the energy
released into the system is checked, so that the required amount of
energy can be fed in over a comparatively long time period, in
order to influence the gait pattern as desired.
[0020] The supply of the mechanical work can be changed by energy
being externally supplied to or drawn from the energy store. If the
energy store is a spring, the supply of energy may take place by
the spring being retensioned; the drawing or reducing of the amount
of energy may take place by the spring being relaxed, for example
by displacement of a spring abutment. If the energy store is
designed as an electrical energy store, for example a capacitor,
battery or storage battery, the changing of the amount of energy
may take place by activation of a generator or introduction from a
second energy store; the reduction of the amount of energy may take
place by connecting a load or diversion into a second store for
electrical energy.
[0021] A development of the invention provides that the energy
store is assigned an actuator, by way of which the energy store is
filled or brought to a minimum level if the relative movement is
not sufficient for this. Should the energy that is available as a
result of the movement not be sufficient to supply the energy store
with sufficient energy for the next step or the sequence of
movements, the minimum amount depending in dependence on the
walking speed, the walking situation and the individual
circumstances of a patient, it is provided according to the
invention that, during the walking and before the return of energy
for assisting the relative movement, the energy store is filled up
to a fixed level, for example by tensioning a spring or by driving
a generator that charges the electrical energy store.
[0022] In order to be able to determine precisely the point in time
of the movement assistance, it is provided according to the
invention that the energy store is assigned a releasing device, by
way of which the energy is partially or completely released from
the energy store. The releasing device determines the point in time
of the release of energy; in the case of complete release, the
duration and the progression of the release of energy is not
controlled by way of the releasing device, but by way of changes in
the energy store, that is to say drawing or supplying energy. In
the case of a partial release, a reduction of the amount of energy
released took place, so that the initial level of the movement
assistance can be set. A partial release allows an adaptation for
example to walking speeds, patients or walking situations to be
performed; the fine influencing of the assistance takes place by
way of the changing in the energy store.
[0023] The energy may be supplied as mechanical work in dependence
on at least one following criterion or a combination of a number of
the following criteria, to be specific the angular position of the
upper part in relation to the lower part, the position of the upper
part and/or the lower part in space, an angular velocity of the
upper part and/or the lower part, the relative velocity between the
upper part and the lower part, the loading situation and/or the
acceleration of the upper part and/or the lower part. As a result,
it is possible that assistance of the movement that is as exact as
possible in terms of time and amount takes place. The positions of
the upper parts and lower parts in relation to one another and in
space can be determined by angle sensors or inertial sensors, the
velocities in relation to one another or within space by
acceleration sensors or a combination of angle sensor and
acceleration sensor. The sensors can be used not only for
determining the point in time of the release of energy, but also
for determining the respective walking situation, the walking speed
and the current position of the respective components in relation
to one another or in space, thereby making it possible to determine
and control the amount and the progression of the supply of energy
for assisting the movement.
[0024] A development of the invention provides that the energy is
fed to or drawn from the energy store in dependence on at least one
or more of the criteria presented above, in order to carry out the
checked control of the movement.
[0025] The point in time of the intervention of the conversion
device for changing the amount of energy to be converted and/or the
amount of energy supplied can be adjusted, so that for example it
can be set in dependence on the walking speed, the walking
situation or the individual parameters of the patient, how large
the amount of energy to be stored is or how large the amount of
energy to be released must be. In the case of a desired large
amount of energy, it is provided that the earliest possible
intervention in the conversion takes place, so that for example a
generator is driven very early and for a very long time, or a
spring is pretensioned very far, in order to convert the mechanical
work when walking, for example when the heel touches down in
standing phase flexion, to the maximum extent into the potential
energy of a spring or electrical energy of a storage battery or a
capacitor. If the point in time of the intervention in the
conversion back is adjusted, for example by displacement of a limit
stop or an angle-dependent release, the energy is introduced at a
later point in time of the step, whereby changing of the gait
pattern can be achieved. The energy store may be charged by an
actuator if the conversion device is not active on account of the
relative movement between the upper part and the lower part, so
that the actuator does not have to work against the relative
movement. In addition, arranging the timing of the charging of the
energy store by the actuator in a phase in which no mechanical work
from the joint device is converted has the advantage that energy
can be stored over a long time period, which has the result that
the actuator can be made to correspondingly small dimensions, to
allow the desired amount to be provided over a great time period.
If, for example, a spring is tensioned by way of a motor as an
actuator, the motor may be of a small design and be coupled by a
transmission to the spring, so that the spring can be tensioned
over a comparatively great time period. The same applies to the
conversion and storage of electrical energy.
[0026] A development of the invention provides that, in addition to
influencing the energy store, the relative movement is influenced
by way of a damping device, so that the control does not have to
take place exclusively by way of the energy store, which has the
result that there is a great possibility for variation in the
influencing of the gait pattern. In addition, loading peaks can be
absorbed more easily by way of an additional damper device.
[0027] The orthopedic joint device of the lower extremity with an
upper part and a lower part mounted in an articulated manner
thereon and a device for converting and/or storing kinetic energy
provides that the storage device has a rate of conversion and/or
storage that is inversely proportional to the pivoting velocity of
the lower part in relation to the upper part. As a result, it is
ensured that, in spite of the actually increasing kinetic energy to
be converted, no self-boosting takes place, so that the system of
the joint device remains stable.
[0028] A generator for generating electrical energy and a motor for
driving the lower part may be provided, the generator being
preceded by a speed-dependent coupling, which connects the
generator to a drive device. The greater the speed of movement, the
lower the power that has to be transmitted by way of the coupling,
so that the inverse proportionality of the energy generation in
relation to the pivoting velocity is realized by way of the
coupling.
[0029] A hydraulic damper unit for damping the pivoting movement
may be arranged between the lower part and the upper part in the
joint device, the hydraulic fluid of the hydraulic damper unit
serving as an actuator for separating the coupling. The coupling
may be designed as a speed-dependent slip clutch.
[0030] A flywheel or a pressure accumulator may be provided as the
storage device for the kinetic energy. The joint device is
preferably designed as a hip joint, knee joint or foot joint of a
prosthesis or an orthosis. The energy store may also be designed as
a spring or storage battery, a storage battery also being
understood as meaning a capacitor or a rechargeable battery.
[0031] A development of the orthopedic joint device provides that
the energy store is assigned an actuator, which supplies or draws
energy to or from the energy store in a controlled manner during
the assistance of the relative movement. The controlled supplying
or controlled drawing of energy to or from the energy store by way
of an actuator makes it possible to influence the gait pattern
particularly easily and reliably in the case of semiactive joint
devices, in particular in the case of semiactive prosthetic knee
joints. The conversion device may be designed as a spring or
generator, in order to store the mechanical work that occurs during
a relative movement between the upper part and the lower part
either in potential energy in a spring or electrical energy in an
electrical storage device, for example in the form of a storage
battery, in a rechargeable battery or in a capacitor.
[0032] A separate damper device may be arranged between the upper
part and the lower part, in order to be able to keep a better check
on the relative movement with assistance by the energy store. By
superposing the influencing of the energy store with the separate
damper device, more precise and more reliable influencing of the
gait pattern can take place. The damper device may be of an
adjustable design, in order to provide adapted damping in
dependence on sensor data, for example with respect to the joint
angle, the walking speed, an angular velocity or an absolute angle
of an upper part and/or an upper part. The damper device may be
adjusted by way of an actuator in order to achieve a reduction or
increase of the damping.
[0033] The conversion device may be adjustably coupled to the upper
part and/or to the lower part in order to displace a position of
intervention or a path of adjustment. As a result, it is possible
to influence both the amount of energy and the point in time of the
supply of energy as desired.
[0034] With the method described and the device described it is
possible that the required energy is supplied only at a suitable
point during the sequence of movements and in a minimal amount. The
user of the orthopedic device continues to introduce the greatest
part of the kinetic energy, for example by way of the remaining
stump. However, a supply of energy is necessary, or at least
advantageous, at two points at which the user of the joint device
cannot introduce the required energy by physical exertion, for
example because the physical strength is not sufficient if very
high accelerations are required because of the mass moments of
inertia. Thus, for example, assistance in the swinging phase when
swinging over the ground is advisable, in order to prevent the
lower part from dragging on the ground during walking. Selective
supplying of energy allows the knee angle to be increased, so that
greater ground clearance is realized. In the case of alternating
climbing up stairs, an additional extension moment can enable the
user to use his or her own strength to overcome the rest of the
step.
[0035] On the basis of the fact that it is only ever the
minimum-necessary amounts of energy that are fed as kinetic energy
into the system, the user retains control over the orthopedic
device at all times. The energy respectively stored would not be
sufficient to bring the user into a critical situation. In
addition, the occurrence of muscular deficits is avoided, since the
user continues to have to apply the kinetic energy himself or
herself; only the fine control is undertaken by the method or the
device.
[0036] Exemplary embodiments of the invention are explained in more
detail on the basis of the accompanying figures, in which:
[0037] FIG. 1 shows a knee angle progression during a gait
cycle;
[0038] FIG. 2 shows the progression of the knee angle velocity over
a gait cycle;
[0039] FIG. 3 shows phases of possible take-ups and releases of
energy of the knee joint during the gait cycle;
[0040] FIG. 4 shows a schematic representation of a joint device
with an energy storage device for flexion assistance;
[0041] FIG. 5 shows a joint device with a device for extension
assistance;
[0042] FIG. 6 shows a joint device with a spring mounted in a
cam;
[0043] FIG. 7 shows a joint device with a flywheel mass as an
energy store;
[0044] FIG. 8 shows a variant of the joint device with extension
control;
[0045] FIG. 9 shows a joint device with two springs;
[0046] FIG. 10 shows a joint device with an elastic cord as an
energy store;
[0047] FIG. 11 shows a variant of FIG. 1 with a displaceable spring
attachment;
[0048] FIG. 12 shows a variant with a spring arranged in the lower
part;
[0049] FIG. 13 shows a variant of FIG. 3 with an interposed
actuator;
[0050] FIG. 14 shows a variant with a twisted filament as an energy
store;
[0051] FIG. 15 shows a representation of drive moment progressions
for different walking speeds:
[0052] FIG. 16 shows a representation of different paths of
displacement against a joint angle for various walking speeds;
[0053] FIG. 17 shows a representation of a lever arm progression
against a joint angle; and
[0054] FIG. 18 shows a representation of a flexion damping setting
of a damper against a knee angle.
[0055] In FIG. 1, a schematic representation of the progression of
the knee angle .alpha. over time is shown. The representation
comprises a gait cycle, that is to say beginning from the setting
down of the heel up until the renewed setting down of the heel of
the same leg.
[0056] After the initial touching down of the heel with a stretched
knee joint, that is to say at a knee angle .alpha. of 180.degree.,
the knee joint initially bends a little in the standing phase,
which is referred to as standing phase flexion. As soon as the foot
is set down completely on the ground, the knee joint is stretched,
so that a knee angle .alpha. of 180.degree. is established. In the
course of the bending movement toward the end of the standing
phase, the knee angle .alpha. decreases. The perpendicular, dashed
line denotes the end of the standing phase, and consequently the
point in time at which the tip of the foot leaves the ground. This
point in time is known as "toe off". In the then-following swinging
phase, the lower part swings further toward the rear and pivots in
relation to the upper part up to the minimum knee angle .alpha. of
120.degree.. There follows a reversal of movement; the lower leg
with the prosthetic foot is brought forward and pivots up to the
stretching stop limit, which lies at a knee angle .alpha. of
180.degree.. In this stretched position, the touching down of the
heel will generally take place.
[0057] In FIG. 2, a schematic representation of the knee angle
.alpha. is superposed with the knee angle velocity v. The knee
angle profile corresponds in this case to that described in FIG. 1.
During the initial standing phase flexion, the knee angle velocity
v increases briefly. During the stretched phase, that is to say at
a knee angle .alpha. of 180.degree., the knee angle does not
change; likewise, the knee angle velocity v remains constant at
0.degree. per second. The bending of the knee joint toward the end
of the standing phase leads to a rise in the knee angle velocity v
up to a maximum at the "toe off". The further swinging-back
movement of the lower part takes place with a slowing speed, until
at a minimum knee angle .alpha. a reversal of movement commences
and the lower part executes an extension movement. Accordingly, the
knee angle velocity extends below the zero line up to the point in
time at which extension damping commences, in order not to allow
the lower part to swing into the stretching stop limit without
deceleration. Accordingly, the knee angle velocity v is reduced
until the lower part has reached the stretching stop limit and the
knee angle .alpha. is again 180.degree.. The knee angle velocity v
is then 0.
[0058] In order to enter the region of great knee bending more
quickly, it is possible and necessary in certain portions of the
gait cycle to increase the knee angle velocity, for example in
order to facilitate swinging through of the leg. The maximum knee
bending may in this case remain the same or else be increased, if
there is extension assistance, in order that the lower leg is
brought forward quickly enough. In FIG. 3, the knee angle .alpha.
over time during a gait cycle is represented once again. In it,
regions in which kinetic energy from the relative movement between
the lower part and the upper part can be converted or stored are
marked; these regions are provided with the reference sign o.
Furthermore, regions in which it may be advantageous to supply
stored energy once again to the system, in order to assist
extension or flexion, are marked by the reference sign i. During
the initial standing phase bending, kinetic energy can be taken up,
in order to feed it back, for example in the extension phase then
immediately following. It is likewise possible to buffer-store the
energy taken up in the bending phase or else toward the end of the
stretching phase to supply it once again during a further energy
take-up phase, so that the lower part is for example flexed or
extended more quickly, in order to achieve the effect that is
respectively desired. The supplying of the converted or stored
energy after a controlled time delay takes place within the same
movement cycle during predetermined phases i, it being preferred to
use deceleration phases to convert and/or store energy and
acceleration phases to feed this energy back after a controlled
time delay. The control preferably takes place electronically; in
principle, however, mechanical control is also possible.
[0059] Provided as supplying phases i are, in particular, the
extension movement after the initial heel contact, the assistance
of the bending to initiate the swinging phase, the maintenance of
the flexion velocity after the "toe off" and also the assistance of
the flexion movement after reaching the maximum flexion angle.
[0060] In FIG. 4, an example of an orthopedic joint device 1 is
shown in a schematic representation. The orthopedic joint device 1
has an upper part 2 and a lower part 3. The lower part 3 is mounted
on the upper part 2 pivotably about a pivot axis 4. The flexion
takes place in the direction of the arrow; an energy conversion
device 5 is arranged on the extension side. The energy conversion
device 5 has a hydraulic cylinder 51, in which a piston 52 is
arranged on a piston rod 53. The piston 52 is used for separating
two chambers 55, 56 hydraulically from one another. In the lower
chamber 55 there is arranged a compression spring. The two chambers
55, 56 are coupled to one another by way of a hydraulic line 57. In
the hydraulic line 57 there is arranged a controllable valve 58, by
way of which the flow rate from the upper chamber 56 into the lower
chamber 55 can be controlled. At the upper end of the piston rod 53
there is arranged a sawtooth-like beveled form-fitting element 531,
which is in engagement with a pivotably mounted toothed rack 59,
which likewise has toothing in the form of sawteeth formed so as to
correspond to that of the form-fitting element 531. During an
extension movement of the lower part 3 in relation to the upper
part, the piston 52 is pushed in. In order to initiate flexion
assistance, the valve 58 is opened to such an extent that the valve
58 allows a faster piston movement than the joint device. For
tensioning the spring 54, the piston rod 53 is pushed downward.
This takes place during an extension movement of the lower part 53
in relation to the upper part. If the lower part 3 flexes in
relation to the upper part 2, the teeth of the toothed rack 53
slide along on the bevel of the form-fitting element 531 on account
of their orientation; during the extension of the lower part 3, the
spring 54 is compressed, since sliding of the toothed rack 59 is
not possible due to the substantially horizontal areas of contact.
For flexion assistance, for example in the initiation of the
swinging phase, that is to say with a relatively greatly bent lower
part 3, the form-fitting element 531 is in engagement relatively
far down on the toothed rack 59 and assists the movement of the
lower part 3 in the direction of the arrow. For flexion assistance,
the valve 58 is mechanically or electrically controlled in
dependence on an ascertained joint angle position or mechanically
or electrically controlled in dependence on a joint angle velocity.
If the valve 58 is opened, the spring 54 can relax, since the
hydraulic fluid can flow out of the upper piston chamber 56 through
the hydraulic line 57 into the lower chamber 55.
[0061] In FIG. 5 there is shown a joint device in which the
direction of action is reversed in comparison with the embodiment
according to FIG. 4. The spring 54 is arranged around the piston
rod 53; the form-fitting element 531 and similarly the arrangement
of the teeth in the toothed rack 59 are oriented in the opposite
direction, so that there is extension assistance. The piston 52 is
drawn out when there is flexion, and has an assisting effect for
the extension when the valve 58 allows a piston movement, which the
spring 54 assists. This may take place in particular when there is
a reversal of the flexion movement into an extension movement. For
controlling the assistance of the extension movement, the toothed
rack 59 or ratchet may be mechanically decoupled or the valve 58
may intervene in a damping manner.
[0062] In FIG. 6, a further variant of the invention is
represented, one in which a spring 6 is compressed by way of a cam
7 when there is flexion of the joint, in order to release the
energy again when there is further bending. Consequently, kinetic
energy can be stored during a flexion movement, for example during
the heel strike, and be fed back to the joint device 1 for the
initiation of the swinging phase for the assistance of the flexion
movement and/or for the maintenance of the bending velocity after
the "toe off". During the extension movement, the spring 6 remains
ineffective on account of the guidance in the cam 7.
[0063] A further variant of the joint device 1 is shown in FIG. 7.
In this case, a flywheel mass 8, which is accelerated when there is
flexion of the lower part 3 in relation to the upper part 2, is
provided as the device for converting and storing kinetic energy.
As the flexion velocity slows down, the flywheel mass 8 releases
the rotational energy again, so that, after reaching the maximum
flexion velocity, that is to say after the "toe off", or the
swinging through in the extension phase, energy is supplied to the
joint device 1 to assist the respective movement.
[0064] In FIG. 8, the device 5 for converting and storing kinetic
energy is constructed in a way similar to that described in FIG. 4,
but without the form-fitting element 531 at the upper end of the
piston rod 53 and without the toothed rack 59. With such a device
it is possible to operate extension control, in particular to set
the extension stop limit. If the joint device is stretched
completely, the piston 52 is moved to the maximum extent into the
lower chamber 55. The compression spring 54 is tensioned to the
maximum extent. The energy stored in this way can be released on
opening of the valve 58 for flexion assistance, so that assistance
is provided at the end of the standing phase for the initiation of
flexion. The further the piston rod 53 is in this case moved out,
the greater the knee angle .alpha. at which the extension control
acts, since the upper end of the piston rod 53 or a component
assigned to it comes into early contact with the stop surface in
the upper part 2.
[0065] In FIG. 9, a further variant of the invention is shown. In
addition to the configuration according to FIG. 4, the energy
conversion device 5 provides a second toothed rack 593 and a second
form-fitting element 533. The second toothed rack 593 is arranged
pivotably on the lower part 3; the second form-fitting element 533
acts on the spring 54 in the lower piston chamber 55. The piston 52
with the piston rod 53 is pushed in by way of the toothed rack 59
when there is extension. The spring 54 stores the kinetic energy as
potential energy. Depending on the intended assistance, either the
spring 541 on the piston rod or the spring 54 away from the piston
rod is compressed.
[0066] The energy conversion device 5 may be assigned a
speed-dependent coupling, which at increased knee angle velocities
v provides reduced friction between force transmission elements, so
that the rate of conversion or storage is inversely proportional to
the pivoting velocity of the lower part 3 in relation to the upper
part 2.
[0067] FIG. 10 shows an orthopedic joint device in the form of a
prosthetic knee joint with an upper part 2, in which an upper leg
shaft 20 for receiving an upper leg stump is arranged. A lower part
3 is fastened in an articulated manner distally in relation to the
upper part 2, so that the upper part 2 can be pivoted in relation
to the lower part 3. Formed on the rear of the upper part 2 is a
bracket 21, arranged on which there is on the one hand a damper
device 50 in the form of a hydraulic or pneumatic damper and on the
other hand an energy store 54 in the form of an elastic cord. The
elastic cord is connected by way of a transmission gear mechanism
11 to an actuator 10 in the form of an electric motor. The electric
motor is arranged in a lower leg tube, which is fastened to the
lower part 3. The energy store 5 in the form of the elastic cord is
fastened to the transmission gear mechanism 11 and a bracket 12; if
the motor 10 is activated, it acts by way of the transmission gear
mechanism 11 on the bracket 12 and can either tension or relax the
elastic cord 54, in that the bracket 12 is displaced in the distal
or proximal direction or is turned in one direction or the other,
in order to roll up or unroll the elastic cord. The bracket 12
consequently forms a displaceable mounting point of the energy
store 5, whereby it is possible in the case of an extension
movement of the lower part 3 to set the beginning of a tensioning
operation of the elastic cord 54. The bracket 12 can be used to
realize a displaceable, elastic stretching stop limit, which is
adjusted by way of the actuator 10. The energy store 54, formed as
a spring, is tensioned by way of an extension movement of the lower
part 10 and takes up part of the kinetic energy of the lower part
3. This may take place for example at the end of the swinging phase
or after the heel strike and the standing phase flexion. The spring
54 is tensioned in the course of the standing phase extension and
continues to be kept tensioned during the standing phase.
[0068] In the terminal standing phase, the stored energy can be
released again to assist the initiation of the swinging phase; the
elastic cord 54 is drawn in and converts the potential energy into
mechanical work, in order to assist the flexion of the lower part
3. If more energy is to be stored in the energy store 54, the
actuator 10 pretensions the elastic cord 54, in that the bracket 12
is displaced distally or in the rolling-up direction; if less
energy is to be stored, the bracket 12 is displaced proximally or
the cord is unrolled. In the exemplary embodiment represented, the
energy storage device 54 is at the same time the conversion device
5, in which the mechanical work from the relative movement is
converted into potential energy.
[0069] In addition to the conversion device 5 or the energy store
54, a separate damper 50 is provided in the form of a hydraulic or
pneumatic damper, which is of an adjustable design, so that the
damper device 50 can be used to influence the damping during
walking, both in the direction of flexion and in the direction of
extension.
[0070] For controlled assistance in the initiation of the swinging
phase, it is provided that changing of the pretensioning of the
elastic cord 54 takes place by way of the actuator 10, the
transmission mechanism 11 and the displacement or turning of the
bracket 12, in order to keep a better check on the release of
energy. It has been found that a spring alone as the energy store
has the effect of introducing too great a force too quickly, which
can be perceived by the patients as unpleasant. In order to keep a
check not only on the time period over which energy is introduced
but also the amount of energy and the power output, a manipulation
can be performed on the energy store 54 in dependence on the
angular position of the upper part 2 in relation to the lower part
3, the angular position of the upper part 2 and/or the lower part 3
in relation to one another or in space, the angular velocities or
the walking speed, in order to limit the power output and
additionally control the time sequence of the release of energy. By
relaxing the spring 54 it is possible to introduce less energy into
the joint device 1; by pretensioning the spring 54, it is possible
to maintain assistance of the flexion over a longer time period and
over a greater flexion angle, in order to achieve the desired
harmonious gait pattern.
[0071] A variant of the invention is shown in FIG. 11, one in which
a displacement at the distal mounting point takes place instead of
the relaxing or tensioning of the spring 54 substantially in its
longitudinal extent. The upper fastening point is guided in a
displaceable spring attachment 25, which by way of the actuator 10
is displaceable back and forth in the direction of the
double-headed arrow. Depending on the point of articulation and the
direction of movement, the elastic cord 54 is tensioned or relaxed.
Both in FIG. 10 and in FIG. 11, the energy from the extension
movement is stored in the elastic cord 54. After ending of the
extension movement, it is possible that the motor 10 can
subsequently retension the cord 54 if the expected energy to be
applied is not sufficient to bring about desired assistance in the
initiation of flexion. The pretensioning advantageously takes place
whenever the joint device 1 is in a completely extended state, in
order to have to work as little as possible against a pretensioning
movement. It is possible by the adjustment either of the
pretensioning of the elastic cord 54 or of the proximal mounting
position to set the stretching angle from which the conversion
device 5 becomes active, whereby how much energy is to be stored in
the energy store 5 can also be set.
[0072] In FIG. 12, a variant of the joint device 1 is shown, one in
which the conversion device 5 in the form of the spring 54 is
arranged in the lower leg tube. The actuator 10 is connected to the
spring 5 and can either compress it or wind it up, depending on the
configuration of the spring as a compression spring or a spiral
spring. The spring 5 is coupled by way of a thrust rod 11 to a
limit stop 16, which is fastened to the upper part 2. By activation
of the motor 10, the bottom point of the spring 5 can be changed,
whereby the thrust rod 11 can be used to set when the spring 5
comes into contact with the limit stop 16. The earlier the thrust
rod 11 comes into contact with the limit stop 16, the greater the
path of adjustment and the compression of the spring 5, so that
correspondingly more energy is stored in the spring 5. Accordingly,
when it is converted back, more energy is transmitted from the
spring by way of the thrust rod 11 to the limit stop 16, so that
increased flexion assistance can be achieved. In order to influence
the release of energy, the spring 5 is either tensioned or relaxed
in the event of movement assistance.
[0073] In FIG. 13 there is shown a variant that corresponds
substantially to FIG. 12; however, the actuator 10, possibly with a
spindle drive and freewheeling in one direction, is arranged
between the spring 5 and the thrust rod 10, so that the bottom
point of the spring 5 remains fixed, but the spring 5 can be
pretensioned with the motor 10. If flexion assistance is initiated,
the motor 10 must join in the rotation, in order to release the
energy and transmit it by way of the thrust rod 11 and the stop
limit 16 to the joint device, whereby particularly good control
over the release of energy can be achieved. It is similarly
possible to stop the release of energy, which may be advisable if a
situation has been misjudged.
[0074] In FIG. 14, a twisted filament is shown as the energy store
54 and conversion device 5, in the case of which shortening is
achieved by a twisting of filaments. By increasing or decreasing
the twisting, the contact point from which the twisted filament
builds up tensile forces can be set. Between the motor 10 and the
twisted filament 54, an axial decoupling 13 is provided.
[0075] Apart from the embodiment shown of the energy store as a
spring, by using a transmission gear mechanism and a generator it
may possibly also be designed as an electrical energy store in the
form of a battery, a storage battery or a capacitor. For converting
the stored electrical energy back, the generator is switched as a
motor, so that driving and assistance of the relative displacement
of the lower part 3 in relation to the upper part 2 can take place.
To increase the amount of energy, a generator may be assigned to
the electrical energy store; it is similarly possible to provide a
further energy store, which serves as a buffer into which excess
electrical energy is fed or from which energy that is additionally
required is provided.
[0076] The springs as energy stores 54 may be designed as tension
springs, compression springs, torsion springs or elastomer
elements, which from a certain stretching angle, which is set by
the actuator 10, come into contact and from this point in time both
convert mechanical work into energy and feed it back for movement
assistance. The spring in this case takes up the energy from the
movement in the direction of extension, and serves at the same time
as a decelerating device and extension stop limit. With the
initiation of the swinging phase, the energy is released again and
helps the user to initiate the swinging phase. The actuator 10 can
be used to adjust the point in time of the contact of the spring in
the case of the release of energy, so that different, controlled
forms of assistance are possible for different walking speeds. It
is similarly possible that the respective spring is retensioned by
way of the motor 10, if the energy stored by the preceding movement
is not sufficient to provide sufficient assistance; for example, in
the case of particularly slow walking or going down steps, the
mechanical work may not be sufficient to tension the spring
sufficiently. As shown in FIG. 12, the spring 5 may be assigned a
releasing device 14, by way of which the initiating time for the
release of the stored energy can be additionally ensured.
[0077] In order to ensure the initiation of the release, the joint
device 1 may include a safety device, which is formed by the
hydraulics in the damper 50 or by a control of the motor 10, which
ensure that the spring energy applied is reduced again in time.
[0078] On account of the fact that the kinetic energy in the
extension is at least partially stored, the assistance provided by
the motor can operate very sparingly. The battery for the actuator
10 can be made small and lightweight, as can the actuator 10
itself, since the actuator 10 has sufficient time when retensioning
in the standing phase to tension the spring, and the feeding in of
the energy does not have to take place as quickly as the release
for the initiation of the swinging phase. The motor 10 controls the
release of energy from the spring, possibly in conjunction with the
separate damper 20. The flexion assistance provided by the energy
store helps in achieving the necessary bending angle in the case of
alternating climbing up stairs and when overcoming obstacles, and
saves hip work.
[0079] In FIG. 15, the drive moment for different walking speeds
are shown against the joint angle .alpha.. The representation is
for three different walking speeds, the respective walking speeds
being represented by different symbols in the diagram; the lowest
walking speed is identified by a triangle, the medium walking speed
by a circle and the highest walking speed by an X. The drive moment
is the effective drive moment in Nm, that is to say the energy
stored by the storage device 5 and fed back, less the losses such
as damping or friction. It is evident that initially a very high
drive moment is used in order to be able to provide the flexion
assistance at the beginning. With an increasing joint angle
.alpha., here the knee angle, which is measured from a maximum
extension position, the drive moment to be applied initially falls
steeply, remains constant over a small angular range, briefly rises
again and then, up to maximum flexion, falls to zero. It is evident
that the flexion assistance at low walking speeds, represented by
the triangle, is greater than at high walking speeds. The drive
moment progression, as it is shown in FIG. 15, cannot be produced
by retensioning or relaxing a spring without the influence of a
motor, since, according to the invention, after a strong drop in
the drive moment, the moment is maintained over a further time
period up until reaching the maximum angle.
[0080] FIG. 16 shows a diagram in which the tension path of the
motor 10 is plotted against the joint angle .alpha.. Various
walking speeds are presented, once again identified by a triangle,
a circle and an X; the lowest walking speed is represented by a
triangle. The representation relates to the translational movement
of the motor 10 in the case of the embodiments of FIGS. 10, 12 and
14. The path of displacement according to FIG. 16 is adjusted such
that the drive moment curve according to FIG. 15 can be achieved.
The respective progression is different for each spring chosen and,
depending on the property of the spring, can lead to a greater or
smaller path of displacement. The aim is to achieve a displacement,
and consequently tensioning, of the spring that is as small as
possible. At the start of the initiation of bending, it is evident
that the motor allows the spring to slide back, in order to achieve
the fastest possible force reduction, in order that the feeling of
controlled flexion continues to be maintained. At greater angles,
the spring is tensioned again, in order to maintain the force or
increase it again. Here, too, it is significant that, at slower
walking speeds, increased assistance is necessary. The release of
the spring, and consequently of the energy, for flexion assistance
and the driving of the motor take place at the same time, so that
it is possible to keep a check over the entire progression of the
flexion assistance.
[0081] FIG. 17 shows the changing of the lever arm according to an
embodiment of FIG. 11 against the joint angle .alpha. for different
walking speeds. Here, too, at the same time as the release of the
spring the motor 10 is activated, in order to adjust the lever arm.
Initially, the lever arm is quickly reduced, in order to bring
about a reduction in the force; subsequently, the lever arm is
increased again, in order to apply force and assist the flexion
movement over a greater angular range a.
[0082] In FIG. 18, the flexion damping setting of the damper device
50 is shown against the joint angle .alpha. for various speeds. As
a departure from the previous figures, the lowest walking speed is
identified by a square, the medium speed by a triangle and the
highest walking speed by a rhomboid. A medium flexion damping
setting of the damper device 50 is initially provided, decreasing
as the joint angle .alpha. increases. At high walking speeds,
raising of the flexion damping may take place toward the end of the
swinging phase, in order to avoid excessive bending of the lower
part 3. By changing the flexion damping setting in the damper unit
50, it is possible in conjunction with the motor control to carry
out effective and safe, as well as simple, control of the
introduction of energy for movement assistance.
[0083] Apart from the embodiment shown as flexion assistance, the
device may in principle also be used for extension assistance; the
statements made in relation to flexion assistance also apply
correspondingly to extension assistance, it also being possible and
intended that flexion assistance and extension assistance are
arranged together in a joint device.
* * * * *