U.S. patent application number 12/083164 was filed with the patent office on 2009-08-27 for device and method for an automatic treadmill therapy.
This patent application is currently assigned to EIDGENOSSISCHE TECHNISCHE HOCHSCHULE ZURICH. Invention is credited to Michael Bernhardt, Robert Riener, Joachim Von Zitzewitz.
Application Number | 20090215588 12/083164 |
Document ID | / |
Family ID | 35822624 |
Filed Date | 2009-08-27 |
United States Patent
Application |
20090215588 |
Kind Code |
A1 |
Riener; Robert ; et
al. |
August 27, 2009 |
Device and Method for an Automatic Treadmill Therapy
Abstract
A method to control the velocity of a treadmill according to the
walking velocity of the person that is using the treadmill. A
reaction force is measured, which occurs when a longitudinal
repulsion force is created between the treadmill (2) and the person
(1). A signal representation for said reaction force is transmitted
to a control unit. The control unit is used to control the velocity
of the treadmill.
Inventors: |
Riener; Robert; (Wangen,
CH) ; Bernhardt; Michael; (Munchen, DE) ; Von
Zitzewitz; Joachim; (Linz, AT) |
Correspondence
Address: |
LERNER, DAVID, LITTENBERG,;KRUMHOLZ & MENTLIK
600 SOUTH AVENUE WEST
WESTFIELD
NJ
07090
US
|
Assignee: |
EIDGENOSSISCHE TECHNISCHE
HOCHSCHULE ZURICH
Zurich
CH
|
Family ID: |
35822624 |
Appl. No.: |
12/083164 |
Filed: |
September 29, 2006 |
PCT Filed: |
September 29, 2006 |
PCT NO: |
PCT/CH2006/000526 |
371 Date: |
March 9, 2009 |
Current U.S.
Class: |
482/7 |
Current CPC
Class: |
A61H 2201/1652 20130101;
A61H 1/0237 20130101; A63B 22/025 20151001; A63B 22/02 20130101;
A61H 2001/0211 20130101; A63B 22/0235 20130101; A61H 2201/1621
20130101; A61H 2201/163 20130101; A63B 22/0023 20130101; A61H 3/008
20130101; A61H 2201/1616 20130101; A63B 2220/51 20130101; A61H
2201/5061 20130101; A61H 3/00 20130101 |
Class at
Publication: |
482/7 |
International
Class: |
A63B 24/00 20060101
A63B024/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 5, 2005 |
EP |
05405570.2 |
Claims
1-13. (canceled)
14. A device for controlling a treadmill based upon a walking
velocity of a person using the treadmill and wherein the treadmill
has a running belt and an adjustable motor for driving the running
belt, the device comprising: a mechanical system capable of fixing
the person against movements in longitudinal direction above and/or
on the running belt; a force sensor arranged between the mechanical
system and the treadmill, the force sensor capable of measuring a
reaction force between the treadmill and the person; and a control
circuit for analyzing the signals provided by the force sensor and
controlling a velocity of the treadmill and/or the movement of an
orthotic device.
15. The device according to claim 14, wherein the mechanical system
comprises a harness and a rod system.
16. The device according to claim 14, wherein the measured reaction
force is a horizontal and a longitudinal force represented by an
electrical signal used as a basic parameter to control the
rotational speed of the motor of the treadmill and/or an actuator
of the orthotic device.
17. The device according to claim 14, wherein the control circuit
comprises an impedance or an admittance control circuit.
18. The device according to claim 14, wherein the device further
comprises additional supporting elements for supporting the
person.
19. The device according to claim 18, wherein the additional
supporting elements include a relief mechanism to relieve the
person from its own weight or a driven orthotic device to provide
guidance of the motion sequence.
20. A method for controlling a treadmill according to the walking
velocity of a person that is using the treadmill comprising
measuring a reaction force when a longitudinal repulsion force is
created between the treadmill and the person, and transmitting a
signal representation for said reaction force to a control unit so
as to control the velocity of the treadmill.
21. The method for controlling the treadmill according to claim 20,
further comprising harnessing the person in an orthotic device,
measuring an orthotic reaction force of the person harnessed in the
orthotic device, and transmitting a signal representation for the
orthotic reaction force to the control unit, wherein the control
unit controls the orthotic device.
22. The method as claimed in claim 20, wherein the signal
representative for the reaction force only comprises a component of
the force parallel to the surface of the treadmill and in a running
direction of the running belt.
23. The method as claimed in claim 20, further comprising
harnessing a body device, a hip device, or a leg orthotic device to
the person; obtaining the signal representative for said reaction
force from a force sensor or from force sensors positioned on a
single rod, a double rod, rods arranged in a parallelogram, or on a
diagonal rod of a linkage; orienting the single rod, double rod,
rods arranged in a parallelogram, the diagonal rod of linkage in
the direction of the running belt attached to a harness of the
person; and positioning the person in view of the running belt, or
on a door-like rod arrangement, or within a hip or leg
orthesis.
24. The method as claimed claim 20, further comprising adjusting
the velocity of the treadmill to a natural motion when a foot
executes a rolling motion on the running belt.
25. The method as claimed in claim 20, wherein an offset force is
added to the measured patient force to simulate a virtual
slope.
26. A method to control a treadmill according to the walking
velocity of the person that is using the treadmill comprising
measuring a reaction force when a person harnessed in an orthotic
device walks with a different velocity than the running belt of the
treadmill and transmitting a signal representation for the reaction
force to a control unit for controlling the treadmill or an
orthotic device.
27. The method as claimed in claim 26, wherein the signal
representative for said reaction force comprises the component of
the force, the component of the force being parallel to the surface
of the treadmill and in a running direction of the running
belt.
28. The method as claimed in claim 26, further comprising:
harnessing a body device, a hip device, or a leg orthotic device to
the person; taking the signal representative for the reaction force
from a force sensor or from force sensors positioned on a single
rod, on two rods, rods which are arranged in a parallelogram, or on
a diagonal rod of a linkage; orienting the single rod, two rods,
rods which are arranged in a parallelogram, or diagonal rod of
linkage in the direction of the running belt attached to the
harness of the person; and positioning the person in view of the
running belt, on a door-like rod arrangement, or within a hip or
leg orthesis.
29. The method as claimed in claim 26, wherein the velocity of the
treadmill is adjusted to a natural motion, when a foot executes a
rolling motion on the running belt.
30. The method as claimed in claim 26, wherein an offset force is
added to the measured patient force to simulate a virtual slope.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a device for adjusting the speed of
a treadmill, which is used for the therapy of paraplegic or
hemiplegic patients and other neurological as well as orthopaedical
patient groups as well as for the (fitness) training of healthy or
elderly subjects.
PRIOR ART
[0002] Treadmills are known by prior art for example from EP 0 002
188. The speed of the treadmill varies according to the heart
frequency of the patient. If the heart frequency reaches an upper
limit, the speed of the treadmill decreases. The heart frequency is
a parameter that is not applicable in the therapy of paraplegic
patients, since the purpose of the therapy is the ability of a
proper motion sequence and the heart frequency does not change in a
manner that is usable for this purpose.
[0003] U.S. Pat. No. 5,707,319 discloses a treadmill with two lever
to pull in order to adjust the belt speed. For patients this is not
usable because the patient has to concentrate on the motion
sequence.
[0004] U.S. Pat. No. 6,179,754 discloses a treadmill equipped with
detectors in order to detect the position of the feet of the
runner. According to the measured position, the running belt will
be accelerated or decelerated. This device cannot be used, when the
runner does not move relatively to the treadmill, e.g. when a
patient is fixed to the surrounding for therapeutical reasons so
that his horizontal position relatively to the treadmill does not
change.
[0005] Another attempt in order to control the velocity of the
treadmill is to detect the load of the motor, as disclosed in U.S.
Pat. No. 6,416,444. The disturbance variables such as frictional
influences are rather big. Due to this inaccuracy it is difficult
to use this device for therapeutical purposes with variable
treadmill speed.
SUMMARY OF THE INVENTION
[0006] An object of the present invention is to provide a method
and a device, which gives a person the possibility for automatic
treadmill training with variable treadmill speed.
[0007] According to the invention there is provided a method to
control the velocity of a treadmill according to the walking
velocity of the person that is using the treadmill. The person's
trunk is connected to the environment via a rigid mechanical frame
(or an elastic band). A reaction force is measured within this
frame (or band), which occurs when the person intends and tries to
increase or decrease his walking velocity. A signal represents said
reaction force. The signal is transmitted to a control unit, which
is used to control the velocity of the treadmill.
[0008] This will provide realistic conditions for a person who
relearns walking with such a method.
[0009] In order to control the velocity of the treadmill the
component of the reaction force, which is parallel to the surface
of the treadmill and in running direction of the running belt of
the treadmill has to be determined.
[0010] The person is harnessed with a hip and possibly-with a leg
orthotic device. The reaction force is measured from force sensors
that can be positioned in various positions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The drawings will be explained in greater detail by means of
a description of an exemplary embodiment, with reference to the
following figures:
[0012] FIG. 1 shows a schematic arrangement of a first device
according to the present invention
[0013] FIG. 2 shows a further schematic arrangement of a second
device according to the present invention
[0014] FIG. 3 shows another schematic arrangement of a third device
according to the present invention
[0015] FIG. 4 shows another schematic arrangement of a fourth
device according to the present invention in combination with an
orthotic device.
[0016] FIG. 5 shows a mechanical arrangement to determine a
horizontal and longitudinal force.
[0017] FIG. 6 shows a further mechanical arrangement to determine a
horizontal and longitudinal force.
[0018] FIG. 7 shows the control circuit that may be used to control
the velocity of a treadmill according to the present invention.
[0019] FIG. 8 shows schematically a block diagram of a general
impedance controller in order to allow a patient-cooperative motion
strategy.
[0020] FIG. 9 shows a block diagram of an adaptive control
strategy.
[0021] FIG. 10 shows the idea of Patient-Driven Motion
Reinforcement.
[0022] FIG. 11 shows the velocity characteristics of the center of
gravity of a human body when starting walking, walking and stopping
with certain velocities.
[0023] FIG. 12 shows the control circuit that may be used to
control the velocity of a treadmill according to the present
invention, when a training person is walking on inclines.
[0024] FIG. 13 shows schematically the force relations for a person
leaning forward as for walking up a hill.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] FIG. 1 shows a schematic view of a first device for
measuring the reaction force, which occurs when a longitudinal
repulsion force is created between a treadmill 2 and a person 1,
wherein the person trains on the treadmill 2 according to one
embodiment of the present invention.
[0026] The device comprises at least a treadmill 2, measure means
3,. a controller 5 and fixation means 10. The treadmill may be a
treadmill as known from prior art i.e. WO 0028927 and comprises at
least a running belt 80 a an adjustable motor. The surface of the
treadmill comprises an essential horizontal base plane 6, on which
the patient is walking. For definition reasons: the running
direction of the running belt 80 is designated as longitudinal
direction and the direction that lies orthogonal to the horizontal
base plane 6 is designated as vertical direction. The direction
orthogonal to these two directions will be called transversal or
lateral direction.
[0027] A person 1 may be a patient who needs a therapy in order to
relearn walking, walks on a treadmill and is rigidly connected to
his surroundings especially by a pelvis or trunk harness. The
treadmill is powered by an adjustable motor and initially runs with
a treadmill velocity v. The velocity v can be adjusted continuously
starting at 0 m/s.
[0028] The patient 1 is connected by fixation means 10 to
mechanical rods 15, 16. Fixation means may be a harness that the
patient 1 is wearing on his upper part of the body. The two
mechanical rods 15, 16 are connected to a first end of a further
rod 20. The second end of the rod 20 is connected to a bearing
point 30 being in fixed relationship to the bearing of the
treadmill. Since the bearing point 30 allows pivoting movements
only, the movement of the patient 1 is restricted to vertical
movements. Lateral (transversal) and longitudinal movements are not
possible. Thus, the patient's position remains on the running belt
80 of the treadmill and especially at the same place. This makes it
possible to provide a lesser length of the treadmill, e.g. only
having a length being in the range of the step length of a person
with a great body height.
[0029] Rod 20 can be a rigid bar or an elastic rubber band or
rubber bar. In case of an elastic connection the patient's position
can vary also in ateral (=transversal) and longitudinal directions.
However, elastic forces are acting in such way that the patient
remains on the treadmill.
[0030] When the patient 1 wants to accelerate or decelerate his
body in order to change the walking-velocity v, he will produce a
longitudinal force in backward or forward direction, respectively.
Due to the rigid mechanical connection of the patient to the
surrounding, this force results in a mechanical reaction force
acting onto the mechanical rods 15, 16, 20. Force measure means 3
are arranged on the mechanical rods, in order to measure the
reaction force. A force measure mean 3 may be a force sensor, for
example based on a strain gauge measurement principle. The measured
reaction force is processed in a controller 5 in order to adjust
the velocity of the treadmill v to the intended walking-velocity of
the patient 1. If the velocity adjustment is optimal, the patient
will have the feeling that he is changing the treadmill speed with
his own voluntary efforts. This method is also designated as
force-based adjustment of the treadmill velocity. This principle
also works if an orthosis such as in WO 0028927 is attached to the
legs of the patient.
[0031] For the force-based adjustment of the treadmill velocity,
only a force component 100 has to be considered in the controller
5. The force component 100 is longitudinal, whereas longitudinal is
horizontal. Several different concepts are possible to measure that
force component 100 and are described by means of the following
figures.
[0032] The force measure means 3 generate a signal according to the
value of the reaction force. The signal is submitted to a
controller 5 to provide input data for the control circuit. The
control circuit will be explained by means of FIG. 7.
[0033] FIG. 2 shows a second embodiment according to the present
invention. The patient is fixed to a plate 43 by the fixation means
10 as already described. On one end, the two rods 40 are connected
to the plate 43 with bearings 42. The plate 43 may provide the
possibility to fix the orthosis. On the other end the two rods 40
are connected to the bearings 30. The distance from one bearing 30
to another bearing 30 is the same as the distance from one bearing
42 to the other bearing 42. Since the two rods 40 have the same
length, a parallelogram. is formed. The parallelogram lies with an
angle .beta. to the horizontal base plane 6. The angle .beta.
depends on the height of the patient 1 and it varies with the up
and down movement of the patient 1. The bearings 30 are hinge
bearings that allow only pivoting movements in the sagittal
plane.
[0034] The axial forces in rods 40 are measured by measure means 3,
4. This arrangement of rods, bearings, and force sensors allows an
easy determination of the longitudinal forces 100, whereas it
remains independent from the vertical force 102. The horizontal
force 100 in walking direction can be computed by the two forces
F.sub.1 and F.sub.2 from the sensors 3 and 4, respectively:
F.sub.longitudinal=(F.sub.1-F.sub.2)cos.beta.
[0035] The vertical load 102 results from gravitation but also from
inertial effects. As this force act in both rods 40 with the same
strength but different directions, above-mentioned equation
automatically compensates for the vertical force in such way that
only the horizontal component 100 remains after correcting the term
F.sub.1-F.sub.2 with factor cos.beta..
[0036] Due to forces that act also in the transversal (lateral)
direction, the measure means 3, 4 have to be chosen accordingly in
order to avoid erroneous force sensor output. In particular, this
requires a sensor that is able to detect a force in one direction
only, which is in that case the direction of the rod. Another
possibility is the use of a sensor that measures in two directions,
which are in that case in the rod direction and in the transversal
(lateral) direction. Note that there is no force acting in the
third direction orthogonal to the rods, when assuming that bearings
30 and 42 are frictionless hinge joints.
[0037] The angle .beta. can be measured by an angle measurement
device as it is known or it can be determined by height
measurements of the plate 43 over the base plane 6.
[0038] FIG. 3 shows a further third embodiment according to the
present invention. The patient 1 is connected to the mechanical rod
system as described in FIG. 1. The rod 20 as introduced in FIG. 1
is now replaced by rod 51 which is one of the horizontal rods of a
linkage 50. The linkage 50 comprises two horizontal rods 51 and two
vertical rods 52 that are arranged in a rectangle. The horizontal
rod 51 is longer than the other horizontal rod 51' and both are
arranged in a way that one end protrudes the vertical rod 52. A
diagonal rod 58 connects a first corner 53 of the parallelogram to
a second corner 54 of the parallelogram. The diagonal rod 52 is
equipped with a force sensor 55. The horizontal rod 51' and the
linker rod 56 are rigidly connected to each other, for example
welded. Via the horizontal rod 51' and a linker rod 56 the linkage
50 is connected to main rods 57. The two main rods 57 are supported
by the bearings 30.
[0039] Due to the arrangement of the linkage, the vertical force
components 102 are carried by the vertical rods 52. Therefore the
force sensor 55 measures only the horizontal component 100 of the
reaction force (in longitudinal direction).
[0040] In a further arrangement it may be possible that the rod 51
and the rod 51' have an equal length. Therefore the welding point
which connects the horizontal rod 51, and the linker rod 56 is
located on one the edge of the linkage 50
[0041] FIG. 4 shows a fourth embodiment similar to the embodiment
of FIG. 1. Additionally to FIG. 1 a driven orthotic device 60
provides aid to the patient in order to learn a proper motion
sequence. The orthotic device 60 may be according to the device as
described in WO 0028927, which may also be designated as gait-robot
or lokomat. The orthotic device 60 is connected via a plate 61 to
the rod system as already described.
[0042] During the training a repulsion force between the treadmill
2 and the person 1 occurs. Force measure means 3 measure a reaction
force that occurs due to the longitudinal repulsion force.
[0043] Additionally to the orthotic device 60 the patient may be
supported by a relieve mechanism 80. A suspended weight 81 is
arranged on one end of a cable 83. The cable 83 is diverted over
two pulleys 82. On the other end the cable 83 is attached to the
harness 10 of the patient 1. Due to the weight 81 on one end the
patient 1 will be relieved from a part of his own weight. The mass
of the weight 81 has to be chosen in accordance of the weight of
the patient 1 and in view of his physical condition. An adjustment
of the length of the cable 83 is also necessary, but not shown in
the drawings.
[0044] FIG. 5 shows schematically a top view of a preferred
embodiment to determine the longitudinal component 100 of the
resulting force 101 produced by the patient explicitly, when the
patient is fixed in an orthosis. Thereby sensors 70, 71 are
arranged in an asymmetric arrangement. Arrow 110 indicates the
walking direction of the patient.
[0045] The mechanical system as shown in FIG. 5 may be a door-like
frame, that is pivoting around a vertical axis. The door-like frame
is arranged at the back of the patient 1. One side of the door-like
frame is connected to a bearing point 75, the other side is blocked
by a sensor 70 and a rod 78 to a bearing point 77. In this
arrangement transversal (lateral) movements of the pelvis are
blocked. The restriction of this degree of freedom results in a
lateral force 103, orthogonal to the measure direction and in a
bending moment in the frame. Due to the asymmetric arrangement with
only one sensor 71 on only one side of the door-like frame, the
bending moment resulting from lateral forces appears also in the
force signal of sensor 71. Therefore, an additional sensor 70 is
arranged to measure lateral forces, in order to compensate the
influences of the bending moment.
[0046] The force 101 is applied to the rod system. The patient 1.
is connected via the harness 10 to a cropped rod 73. The cropped
rod 73 is connected -to a longitudinal rod 74. A sensor 70 is
mounted on the cropped rod 73, this sensor measures the lateral
(transversal) component 103 of the force 101, also designated as
F.sub.2. A longitudinal rod 74 is connected to a transversal rod
72. On one end the transversal rod 72 is connected to a bearing 75,
whereas on the other end a sensor rod 78, which lies in
longitudinal direction, leads to a further bearing 77. The sensor
rod 78 is equipped with a force sensor 71 to measure the horizontal
force, also designated as F.sub.1. The longitudinal force 100 is
determined with the aid of F.sub.1 and F.sub.2:
F longitudinal = - F 1 ( a + b ) + F 2 l b ##EQU00001##
[0047] The algebraic sign is chosen in such way that pressure
forces on the fixation system (patient decelerates) result in
negative and tractive forces (patient accelerates) result in
positive signals. If the lateral forces measured by sensor 70 are
unaccounted for the horizontal and longitudinal force 100, the
lateral (transversal) component of the reaction force would be
wrongly considered as the longitudinal force 100.
[0048] FIG. 6 shows a further top view of an asymmetric
arrangement, provided to determine the longitudinal force 100. A
linker rod 79 connects one end of the transversal rod 72 to the
bearing point 75. At the other end, the transversal rod 72 is
connected, to a further linker rod 91 by a joint 90. The linker rod
91 is connected to a bearing point 92. This newly built degree of
freedom is compensated by the sensor rod 78. The sensor rod 78 is
orthogonally connected to the linker rod 91. However the sensors
may be placed at any of the rods 72, 79 and 91. With such a rod
arrangement, the sensor measures only the horizontal and
longitudinal force 100.
[0049] FIG. 7 shows a control circuit according to the present
invention. The controller 5 (see FIGS. 1, 2, and 4) comprises a
control circuit, that integrates the physical determination of the
velocity from the longitudinal component of the reaction force. The
control circuit is preferably an admittance control circuit, but
also an impedance control circuit may be used.
[0050] The reaction force that occurs due to the mechanical
fixation of the patient 1 is measured by a sensor 201. An
electrical signal that may be linear or non-linear to the reaction
force is provided by the sensor 201.
[0051] The measured force will then be divided by a mass. This is
conducted by a divider 202. After the divider a signal {umlaut over
(x)}.sub.1 results. The value of the mass may be chosen according
to the patient's physical condition. When the patient's physical
condition is good, the parameter is equal to the body mass in order
to provide a realistic situation and walking feeling for the
patient. If the patient's motor system is weakened, for example
after a surgery, injury or neuromuscular disease, a mass with a
value lower than the body mass may be chosen. This will make it
easier for the patient, because the force that is required to
accelerate and walk will be smaller.
[0052] However, if the present invention is used for endurance
training or rehabilitation of professional athletes it is possible
to adjust the mass in an other range. Preferably a value will be
used that is between 1 and 1.5 and especially between 1.2 and 1.5
of the body mass. This relieves the joints of the patient, namely
the joints in the persons under part of the body, compared to the
training method of fixing additional weights on the person's
body.
[0053] {umlaut over (x)}.sub.1 is integrated by an integrator 203
and a velocity input signal {dot over (x)}.sub.1 results. The
actual velocity of the treadmill 2 is {dot over (x)}. {dot over
(x)}.sub.1-{dot over (x)} is fed. into a PD velocity controller 204
that controls the treadmill 2 to provide equal velocities. A PID
controller or any other control law may also be used.
[0054] The force-based velocity adjustment of the treadmill can be
used together with an orthotic device such as the gait-robot
according to WO 0028927.
[0055] In the most, cases the device according to WO 0028927 is
being used in a position-control mode, where the legs of the
patient are moved along a predefined, desired trajectory. FIG. 11
shows such a characteristic. During this fully guided movement the
velocity of the feet may not fully correspond to the velocity of
the treadmill due to inaccurate fixation between patient and
orthosis or due to different leg anthropometries among the
patients. During the swing phase 301, this speed deviation is not a
problem. However, during the stance phase, when one foot or both
feet are touching the treadmill, the speed differences result in
mechanical stress acting between treadmill and lokomat onto the
legs and feet of the patient. As this stress acts as a horizontal
force in longitudinal direction, the force is measured by the
sensor arrangements presented and the speed of the treadmill is
adjusted in such a way that the force and, thus, the stress acting
on the patient's legs and feet is minimized.
[0056] The velocity characteristics as shown in FIG. 11 will now be
explained in greater detail. A curve 308 shows velocity
characteristics of the center of gravity of a human body when
walking with a certain velocity. In a first section of the
movement, the patient accelerates, this is designated as the
development phase 300. The first bend 303 in the development phase
300 shows the first step of the patient. The second bend 304 shows
the second step of the patient. After another step, the patient
reaches his average speed, which is indicated by a horizontal line
305, since the patient walks with a constant velocity. But even
when patient walks with a constant velocity, the velocity of the
center of gravity of the body oscillates around that line 305. With
each step the center of gravity is accelerated and decelerated
respectively, this is shown by the rhythmic phase 301. If the
patient accelerates or decelerates the line 305 changes the slope.
Acceleration is indicated by line 306, deceleration is indicated by
line 307. However the oscillation of the center of gravity will be
similar as if the patient walks at a constant velocity. During
treadmill training the acceleration and deceleration is
recognizable in an orthogonal plane of the walking direction as an
alternating relative movement. While a device e.g. according to WO
0028927 is used, this relative movement is not possible, thus, it
results in a reaction force at the fixation. The reaction force is
measured as described and. the velocity of the treadmill is
controlled accordingly, i.e. the velocity of the running belt
"oscillates" around the mean velocity. This gives the advantage to
this device that a patient has the impression that his feet are
touching the running belt in a natural way and there is no sliding
of the feet on the belt. Additionally the control unit 5 can
anticipate the "oscillating" reaction force and discern this
intra-step movement form voluntary accelerations or decelerations.
The decay phase 302 represents the end of the treadmill training
session. The patient decelerates slowly, until the velocity reaches
0 m/s. Bends 310 and 311 show the last two steps. All the
controllers as described in that application are able to control
such a velocity characteristic.
[0057] It is noted that the force acting on the patient positioned
within his harness is not coming from the harness as such, staying
at the same place, but through the movement of the treadmill
belt.
[0058] The force-based treadmill speed adjustment can also be
applied, when the gait-robot according to WO 0028927 is being used
in so-called patient-cooperative modes. Here, voluntary intentions
and muscular efforts of the patient are detected within the
gait-robot system in order to adjust the gait-robot assistance to
the patient. Thus, walking pattern and speed are controlled by the
patient. Therefore, patient-cooperative strategies require the
possibility to automatically adjust the treadmill speed to the
patient effort or intention. Treadmill speed adjustment must occur
in real-time with minimal delay times.
[0059] In FIGS. 8, 9, and 10 patient-cooperative strategies are
presented that record the patient's movement efforts in order to
make the robot behavior flexible and adaptive. Three different
technical concepts are presented, which were applied to the
gait-robot according to WO 0028927. It is clear that they can be
used in connection with a number of different gait-robots.
[0060] The three strategies comprise, first, impedance control
methods that make the gait-robot soft and compliant, second,
adaptive control methods that adjust the reference trajectory
and/or controller to the individual subject, and, third, a motion
reinforcement strategy that supports patient-induced movements.
[0061] FIG. 8 shows schematically a block diagram of a general
impedance controller in order to allow a patient-cooperative motion
strategy. Impedance controllers are well established in the field
of robotics and human-system interaction. The basic idea of the
impedance control strategy applied to robot-aided treadmill
training is to allow a variable deviation from a given leg
trajectory rather than imposing a rigid gait pattern. The deviation
depends on the patient's effort and behaviour. An adjustable moment
is applied at each joint in order to keep the leg within a defined
range along the trajectory. The moment can be described as a zero
order (stiffness), or higher order (usually first or second order)
function of angular position and its derivatives. This moment is
more generally called mechanical impedance. The deviations from the
desired trajectory results in variations of the gait speed, which
requires the treadmill to be
[0062] FIG. 9 shows the idea of a Patient-Driven Motion
Reinforcement (PDMR) strategy for the control of patient-induced
walking movements. Here, the actual movement initiated by the
patient is recorded and fed into an inverse dynamic model of the
patient in order to determine the robot moment contribution that
maintains the movement induced by the patient. This means that the
patient has to apply some own voluntary efforts in order to obtain
a movement at all. This movement is then supported by the robot. A
scaling factor K can be introduced in-order to vary the supporting
moment.
[0063] FIG. 10 shows a block diagram of an adaptive control
strategy. The main disadvantage of the impedance control strategy
presented above is that it is based on a fixed reference
trajectory. In comparison, the adaptive controller changes its
reference trajectory as function of the patient efforts. In this
way the desired trajectory adapts to the individual patient.
Therefore, not only gait pattern but also gait speed are changing,
thus, requiring an online treadmill speed adjustment function.
[0064] The PDMR controller enables the subjects to walk with their
own walking-speeds and patterns. The device according to WO 0028927
as well as the treadmill speed adapts to the human muscle efforts
and supports the movement of the subject's leg, e.g. by
compensating for the gravity and velocity dependent effects.
Prerequisite for this controller is that the subject has sufficient
voluntary force to induce the robot-supported movement.
[0065] It has to be anticipated, that running belts are usually
reacting with a time delay. Therefore the control unit anticipates
these delays within the frame of the control of the drives of the
running belt 80.
[0066] Due to controlling the treadmill in the way as described
above, it is possible to provide a very realistic sensation of
walking as the forces that occur during acceleration and
deceleration as well as during the decay phase are similar to the
forces that occur when the person walks on a fixed ground. The
person has to overcome the inertia when changing speed on fixed
ground. This inertia does not occur, if the person is not fixed and
the treadmill is not controlled as shown in FIG. 7, because it is
the running belt and not the person's center of mass that changes
speed.
[0067] FIG. 12 shows the control circuit that may be used to
control the velocity of a treadmill according to the present
invention, when walking on an incline is simulated. The main parts
of the control circuit according to FIG. 12 are similar to the
circuit according to FIG. 7. The reaction force that occurs due to
the mechanical fixation of the patient 1 is measured by a sensor
201. This reaction force F.sub.patient is submitted to an adder
210. An additional offset force F.sub.offset corresponding to the
virtual inclination of the virtual slope is added within this adder
210, being dependent on the weight of the person 1 and the
inclination to be simulated.
[0068] The sum force will then be divided by a mass by a divider
202. The value of the mass may--as within the embodiment shown in
FIG. 7--be chosen according to the patient's physical condition.
The resulting value {dot over (x)}.sub.1 is integrated by an
integrator 203 and a velocity input signal {dot over (x)}.sub.1
results. For safety reasons the velocity input signal {dot over
(x)}.sub.1 can be passed through a saturation block 211, which
limits {dot over (x)}.sub.1 to positive values. This prevents the
treadmill form running in negative running direction when the
situation of walking uphill is simulated but the person does not
generate any longitudinal force.
[0069] The actual velocity of the treadmill 2 being {dot over (x)},
the difference value of {dot over (x)}.sub.1s-{dot over (x)} is fed
into a PD velocity controller 204. A PID controller or any other
control law may also be used.
[0070] FIG. 13 A&B show-schematically the force relations for a
person leaning forward as for walking up a hill. FIG. 13A shows a
person 1 going uphill, the hill having an inclination of .alpha..
The person's mass force G, the normal force N and the friction
force F.sub.R are depicted, wherein F.sub.R=Gsin.alpha..
[0071] FIG. 13B shows the person 1 according to FIG. 13A going
virtually uphill and positioned in an harness with a longitudinal
rod 20, a force sensor 3 and a bearing 30. The relative angle
.beta. between the surface of the treadmill and the person is
defined as arctan(l/h). h is the vertical distance between the
running belt and the person's center of mass and 1 is the
longitudinal distance between the line of action of G and N for the
static loading case of F.sub.R=F.sub.offset. The friction force for
a person positioned on a running belt is therefore
F.sub.R=Gl/h=Gtan.beta.. An inclination of 20% corresponds to
.alpha.=11,31.degree.. An angle of 11.degree. results in an angle
.beta.=10,8.degree.. This is due to the fact that .beta.=arctan(sin
.alpha.). Therefore a person starting to walk on such a running
belt, will first lean forward to create the angle of the slope.
This is enabled through the fixed position of the center of gravity
of the person within its harness.
REFERENCE NUMERALS
[0072] 1 Patient [0073] 2 Treadmill [0074] 3 Force sensor [0075] 4
Force sensor [0076] 5 Controller [0077] 6 Base plane [0078] 10
Fixation means [0079] 15 Rod [0080] 16 Rod [0081] 20 Rod [0082] 30
Bearing [0083] 40 Rod [0084] 41 Angle of parallelogram [0085] 42
Bearing [0086] 43 Plate [0087] 50 Linkage [0088] 51 Horizontal rod
[0089] 52 Vertical rod [0090] 53 First corner [0091] 54 Second
corner [0092] 55 Force sensor [0093] 57 Main rod [0094] 58 Diagonal
rod [0095] 60 Orthotic device [0096] 70 Force sensor [0097] 71
Force sensor [0098] 72 Transverse rod [0099] 73 Cropped rod [0100]
74 Longitudinal rod [0101] 75 Bearing point [0102] 77 Bearing point
[0103] 78 Sensor rod [0104] 79 Linker rod [0105] 80 Relieve
mechanism [0106] 81 Weight [0107] 82 Pulley [0108] 83 Cable [0109]
90 Joint [0110] 91 Linker rod [0111] 92 Bearing point [0112] 100
Longitudinal force [0113] 101 Force generated by patient [0114] 102
Vertical force [0115] 103 Lateral (transversal) force [0116] 110
Walking direction [0117] 201 Force sensor [0118] 202 Divider [0119]
203 Integrator [0120] 204 PD-Controller [0121] 210 Adder [0122] 211
Saturation block [0123] 300 Development phase [0124] 301 Rhythmic
phase [0125] 302 Decay phase [0126] 303 First step [0127] 304
Second step [0128] 305 Average velocity [0129] 306 Acceleration
[0130] 307 Deceleration [0131] 308 Velocity characteristic [0132]
310 Penultimate step [0133] 311 Ultimate step
* * * * *