Note: Descriptions are shown in the official language in which they were submitted.
1115778
The present invention relates to medical equipment and,
more particularly, to a bioelectrically controlled electric
stimulator o~ human muscles.
The invention-is applicable in clinical conditions for
the analysis, diagnOstics and treatment of dyskinesia of the
central and peripheral origins. The invention is especially
useful for treating neuritides of the facial, ulnar, radial,
median, peroneal and tibial nerves, a~ well as residual disor-
ders of cerebral circulation in the form of hemiplegia and
hemiparesis, and residual disorders of poliomy~litis and
infantile cerebral paralysis. ~he in~ention i~ also applicable
to the control and correction of move~ents, as well as to
mastering certain motor skills in the course of professional
and sports training, etc. The inve~tion c~ be used to the
best advantage under special training conditions, when a per-
son is in a state of hypokyne~ia or hypodynamia.
At present, the basic problem pertaining to electric
stimulator~ of huma~ muscles is how to use such stimulators
not only for restoring the strength of damaged muscles, but
also for restoring lost motor skills, i.e. how to enable a
person to perform compound motions of the extremities, torso
and head similar to those of a healthy person's extremities,
torso and head.
~ he most promising type o~ electric stimulator is the
bioelectrically controlled stimulator with a plurality o~ sti-
mula~io~ channels. In such stimulators, the control action on
,'
;~ - 3 - ~
, . . - - , ..... . . . . .
- ~ . , - " , ,
,"
. . - ,. .: - . . . -
,. . . . . ...
.
.. . ..
. ..
157~8
the output electric signal of the carrier frequency oscillator,
which acts on human muscles, is provided by the bioelectric
muscular activity of organs or tissues. Due to the ~act that
such stimula~ors havela plurality of channels and employ the
bioelectric w~uscular activity of a person, who sets a program
of movemer.~_, as the control action, such stimulators can elec-
trically stimulate a plurallty of muscles. The sequence of
stimula~ion correspon~s to the sequence o~ contract~ons o~
muscles in natural conditions, while performing certain move-
ments. '~his provides for compound motions of the extremities,
torso and head.
Of late, much attention has been paid to bioelectrically
controlled electric stimulators incorporating a feedback sys-
tem to provide information on the correspondence between a
preset program of movements and the movements actually perfor-
med by a person.
~ he major difficulty in providing feedback systems for
bioelectrica~ly controlled electric stimulators is to develop
sensors to supply information on the spatial position of the
motor organ~. There are different ways of solving this probiem.
One of the solution is the use of what is known as the
bioelectrolocation method which lS carried out as follows~ ;
Electric stimulation brings about contraction of muscles, which
is accompanied by bioelectric activity caused by the stimulat-
ing signal. The bioelectric activity can be registered with the
aid o~ the same electrodes that arè employed for muscle stimu-
lation through the use of the time or ~requency separation tech-
.
. ; , ., :, .. . .
. . ., , . . . ,~ . ... .. . .. . .
. . . ,.. .. .. . . , . .. ,, - .. ; .
. . :, . ,; , ., : ~ ,
niques. The response signal thus prod~ced, i.e. the signal
with which a muscle responds to stimulation, can be used as a
feedback signal which provides information on the degree of
correspondence between the actually performed and programmed
movements and characterizes the functional state o~ the muscles
being stimulated.
The~oregoin~ principle of providing a feedback system for
adjusting a signal which stimulates the muscular activity
underlies a bioelectrically controlled electric stimulator of
human muscles, which comprises six stimulation channels. Each
of said channels includes a bioelectric muscu~ar activity sen- ;
sor, which sets a program of movements, and a first integrator.
The sensor and integrator are cornected in series. ~he function
of the bioelectric activity sensor can be performed by electro-
des connected to human muscles and serving to register the bio-
electric activity of these muscles, and a bioelectric activity
amplifier. ~he bioelectric a¢tivity sensor can be ¢onstructed
as a magnetic recorder which records the bioelectric activity
data.
The output of the integrator is connected to the first
input of a comparator for comparing the bioelectric muscular
activity of a person who sets a program of movements and a
person whose movements are under control. ~he integrator's
output is also connected to the control input of a modulator.
'I`he other input of the modulator is connected to the output
of an oscillator of the carrier frequency of the electric sig- -
nal which stimu}ates the activity of muscles. This signal may
.. . :,
, : . , .. .:
: :, ~ - .
. . ~ , . .. ~ - . . ~ . .
- ~, .. ;: ~.
':'; ~ . ;.: ,.,: . ~ ' :.
~ ;, : .
- . : . ~ ~ ~ . :
- ~.1S778
be a sinusoidal or pulse electric signal. ~he output of the
separator is connected to the input o~ said oscillatorD The
output o~ the modula~or is coupled via a power amplifier to
the first input of a unit for separating the electric signal,
which stimulates muscular activity of the person whose move-
~ents are being controlled, and the bioelectric activity caused
by said signal. The second input of said separation unit and its-
first output are connected to electrodes connected, in turn, ;~
to muscles of the person whose movements are under control.
The second output of the separation unit is connected to a
second integrator via an amplifier of bioe~ectric muscular
activity o~ the person whose movements are under control.
~he output of the second integrator is connected to the second
input of said comparator.
However, the bioelectrically controlled electric stimula-
tor of human muscles under review cannot ensure complete cor-
respondence between an actually performed mo~ement and a pro- ;
grammed movement, which is due to the following factors.
In the known stimulator, the coxrespondence between the
programmed and actually performed movements is achieved by ad-
justing one or several parameters of the signal which stimula-
tes muscular activity (the stimulating signal). The adjustment
equalizes the force and speed o~ contraction o~ muscles of
the person who sets the program of movements and the person
whose movements are under control. As a r~le, several muscles
take part in per~orming a movement. ~hus, in order to ensure
:,
~ -- 6 --
correspondence between the programmed and actually per~ormed
movements, the stimulating signal must be adjusted in each
stimulation channel. As a result, it is necessary to have a
stimulating signal carrier ~requency oscillator in each chan
nel, which accoun's for a complicated design of the stimulator
and causes pain in the course of stimulation. ~he pain is
due to a low-frequency interference signal at the output of
the oscillator; the interference, in turn, is caused by the
combination frequencies of the oscillators of all the channels.
Interference signals at the output of the oscillator can be
avoided by synchronizing the stimulating signal frequencies
of all the oscillators, in which case, however, the stimula-
tor design becomes still more complicated.
In the final analysis, the actually performed movement
is a far cry from the programmed one.
~ he lack of correspondence between the actually per~ormed `
and programmed movements is also due to the fact that in the
known stimulator, the program signal is applied through the
electrodes to the muscles of the person, whose movements are
- being controlled~ from zero level. It must be reminded in this
connection th~t muscles sh~w a strongly pronounced threshold
effect, which means that they are excited and co~tract only at
a certain level of the stimulating signal, referred to as the
excitation threshold. As a stimulating signal iB applied to the
electrodes connected to muscles of a person whose movements
are to be controlled, these muscles are e~cited and contract
.
? - 7 -
- . .. .. ~ , .
- ,, ~.. : :, ; . .: . . .
. .
l~lSi7~
a~ter soJlle time lag relative to the contraction of the resQec-
tive muscles of the person setting the program of movements.
The time lag is determined by the time required ~or ~he ampli-
tude of the stimulating signal to reach the excitation thre-
shold o~ the muscles of the person whose movements are under
control, and depends on the speed of movement of the muscles
at the initial moment of time. '~he greater the speed of the
muscles' movement at the initial moment of time, the less the
time lag and vice versa. As a result, the lack o~ correspon-
dence between the actually per~ormed and programmed movernents
is ~articularly pronounced i~ the person, who sets the program, -
performs 810w movements.
In the known stimulator, another reason why the actually
performed movements correspond but little to the programmed
movements lies in the fact that the program signal is not
adausted to different functional states of di~`ferent persons'
muscles, as well as to changing functional states o~ muscles
of one person, which states may vary in the course of electric
stimulation.
It is ~nown that there exist substantial differences in
the f~nctional state of muscles of different persons. ~his is
especially true of pathological motor disturbances. The func-
tional state of muscles being stimulated may also vary consi-
derably ln the course of electric stimulation. As a result,the
dynamic ran~e of the stimulatinO~ signal, within which the force
or speed of contraction of musc~es change linearly followinO~
a change in the signal's amplitude, is different in different
. .
- 8 -
,
. . ~ ., ,: -, , ~ . , , : . .
'' ' , ~ ,
persons, as well as in different muscles of one person in the
course o~ stlmulation. ~he dynamic range is to be understood
as the range of the stimulating signal, which is limited from
below by the amplitude o~ the stimulating signal, correspond-
ing to the excitation threshold of the muscles of the person
v~hose movements are under control and from above, by the maxi-
mum amp~itude o~ said stimulating si~nal. The maximum amplitude
o~ the stimulating signal is an amplitude, whose ~urther in-
crease cannot linearly increase the force or speed of muscles'
contraction.
It can be inferred ~rom the above that it is necessary
to adjust the dynamic range of the program signal with due re-
gard for different functional states of muscles of diLferent
persons and changes in the functional state o~ muscles of one ;
person during the stimulation process. It is also necessary
to adjust the dynamic range of the program signal so that the
maximum amplitude o~ the stimulating signal should not be in
exoess of a-value at which stimulation brings pain.
In the known stimulator, the stimulating signal is adjusted
without regard for the fatiguability of the muscles being
stimulated, which invariably occurs in the course of electric
stimulation. ~n order to avoid excessive strain of the neuro- -
muscular system o~ a person being stimulated, it is necessar~
to discontinue the e~ectric stimulation or s~itch over to spa-
ring stimulation.
It is an object of the present invention to provide a
bioelectrically controlled electric stimulator of human muscles,~
:
_ 9 _
, . .. . : .. ;. ~ . . ~
which would improve the correspondence between actually per-
formed and prograinmed movements.
It is another object of the invention to mitigate pain
in the course of stimula-tion.
It is still another object of the invention to make it
possible to check the fatiguability of muscles in the course
of electric stimulation and change the stimulation conditions
at the onset of fatiguability.
It is ye.b another object of the invention to simpli~y - -
the design and raise the reliability of the electric sti.mu-
lator. . .
~ he objects o~ the present invention are attained by pro- ~:
viding a bioelectrically controlled electric stimulator of
human muscles, wherein each of at Ieast two stimulation chan- .
nels comprises in series a bioelectric muscular activity sensor,
which sets a program of movements, and a ~irst integrator elac- -
trically coupled with its output to the input of a comparator
for comparing bioelectric muscular activity of a person who ~.:
sets a program of mo~ements with that of a person whose move-
ments are under control, and to the control i~put of a modula-
.
tor, to whose other input there is applied an electric signal
stimulating the second person's muscles, the output of the mo-
dulator being electrically coupled to a power ampli~ier conIlec- :
ted to the input of a unit for separating the electric signal,
which stimulates muscles o~ the person whose movements are
,,
under control, and the bioelectric activity o~ these muscles,
- 10 -
,
. . . ~ .,, ~ ,. -. .,; ...................... . .
. - . : ~ : . . - . . - .:- .. . . . .
1~.1577B
caused by said electric signal, the second input o~ said sepa-
ration un~ t and its output being both eonnected to electrodes
co~nected to muscles of the person whose movements are under
control, the second output of the separation unit being coup-
led by means of an amplifier of bioelectric activity of muscles :
of the person, whose movements are under control, to a second
integrator whose output is electrically coupled to the second
input o~ the comparator for comparin~ the bioelectric activity
of muscles of the person setting the programi of movements with
that of the person whose movements are under control, in which
stimulator the output of the comparator for comparing the bio-
electric activity of muscles o~ the person, who sets the pro-
gram of movements, with that of the person, whose movements
are under control, is electrically coupled, in accordance
with the invention, to the control input of the modulator
whose other input is eonnected to an oseillator of the earrier
~requeney of the stimulating eleetrie signal, which oscillator
is common ~or all the stimulation ehannels.
~ he proposed bioeleetrieally eontrolled electric stimula- :
tor of human muscles improves the degree of correspondenee
~between actually performed and programmied movements, mitigates
pain in the course of stimulation and ~eatures a simplified
design.
It is expedient that the inputs of the eomparator ~or
eomparin~ the bioeleetric aetivity of muscles of the person,
who sets the pro~ram o~ movements, with that o~ the person,
whose movements are under control,should be directly connected
..... .
, : . - : ., :, - , , , :;, - -
..,. . ... ,: .
. , . : . ;.
.'
to the respective outputs of the first and second inte~rators,
~vhereas the output o~ the comparator should be connected to
the control input of the modulator by means of an adder which
must also be connected to the output of the first integrator.
~'his makes it possible to reduce the time lag of a movement
being performed with respect to a programmed movement and thus
improve the correspondence between these movements.
It is also expedient that the inputs of the comparator
for comparing the bioelectric activity o~ muscles o~ the per-
son, who sets the program of movements, with that of the
person, whose movements are under control, ~hould be electri- -
cally coupled to the respective outputs o~ the ~irst and se-
cond integrators by means of a first threshold element a~d a
second threshold element, respectively, whereas the output o~
the comparator for comparing the bioelectric activity o~ mus-
cles of the person, who sets the~program o~ movements, with
that o~ the person, whose movements are under control,should
be electrically coupled to the control input of the modulator
by means o~ a unit for forming the excitation -threshold o~
muscles o~ the person, whose movements are under control, the
input of said unit being connected to the output of the co~pa-
rator and an adder whose input is electrically coupled to the
output of said forming unit, its second input being electri-
cally coupled to the output of the ~ t integrator, w~ereas
.
the second i~put o~ the unit for forming the excitation thre-
shold of muscles of the person, whose movements are under con-
;,
jl - 12 -
.. , ~ , ~ - - . ;. . .. - .
- :. . -, . ~-; . :
trol, is connected to the output of the first threshold ele-
ment. This rules out a distortion of the program signal at the
start o~ a movement and makes it possible to adjust the program
signal with due regard for both the disparity in the actually
performed and programmed movements, and the excitation thre- -
shold of the muscles being stimulated, which is dependent on
the functional state of these muscles.
It is preferable that each stimulation channel should i~-
clude a ~oltage divider whose input is connected to the output
of the first integrator, the latter's control input being elec-
trically coupled to the output of the unit for forming the eæ-
citation threshold of muscles of the person whose movements are
- under control, its output being connected to the second input
of the adder. This makes it possible to adjust the dynamic
range of program signals with due regard for the functional
state of muscles of different persons, or to changes in the
functional state of musc~es of one person in the course of
eleotric stimulatlon.
It is advisable that each stimulation cha~nel should in-
clude a frequency meter and a first dif~erentiator amplifier
placed in series with the output of the amplifier of ~ioelec-
tric activity of the person whose movements are under control,
as well as a second differentiator amplifier whose input is
connected to the output of the second integrator, a ~ult~plier
whose first input is connected to the output of the first diffe-
re~tiator amplifier, whereas its second input iB connected to
: : '
- 13 -
i~;J,;
::
.: : ',: :
.` : :, . :, - ~ .
the output of the second differentiator amplifier, an electronic
switch whose control input is connected to the output of the
mul-tiplier, whereas it~ other input i8 co~nected to the output ~ :
o~ the freguency meter, and a second voltage divider whose cont-;
rol input is connected to the output of the electronic switch,
its other input being connected to the output of the unit for
~orming the excitation threshold of muscles of the person whose
movements are under control, whereas the output of said second
voltage divider is connected to the control input of the first
voltage divider. This makes it possible to form a stimulating
signal with due regard ~or the fatiguabi~ity o~ muscles and
either alter the stimulation conditions or discontinue the
electric stimulation at a proper time and thus rule out exces-
sive strain of the neuromuscular system of the person being
stimulated.
It is also advisable that each stimulation channel should
include a reference signal setting unit whose input is connec-
ted to the output of the first threshold element, a third
threshold element, one of its inputs being connected to the
output of the reference signal setting unit, its other input
being connected to the output of the comparator for comparing
the bioelectric activity of muscles of the person, w~o sets
the program of movements, and the person, whose moveme~ts
are under control, and a second electronic awitch who~e control
input is connected to the output of the third threshold ele-
ments, its other input being connected to the output o~ the mo-
- 14 -
. ::
:.
5~7
dulator, whereas its output is connected to the po~er amiplifier.
r~.his accounts for an improved reliability of the stimulator
and thus protects the person, whose mov~ments are under cont-
rol, from the effects of painful or dangerous electric si~nals.
Other objects and advantages of the present invention
will be more readi y understood ~rom the following detailed
description of preferred embodiments thereo~ to be read in
conjunction with the accompanying drawings, wherein:
~ IG. 1 is a block diagram of a bioelectrically controlled
electric stimulator or human muscles, in accordance with the
invention;
~ IG. ~ is a structural diagram of the unit for separating
the electric signal, which stimulates muscles of the person
whose movements are under control, and the bioelectrical acti-
vity o~ these muscles of the electric stimulator in accordance
with the invention;
FIG. 3 is a block diagram of a stimulation channel with
an adder of the electric stimulator in accordance with the
invention;
FIG. 4 is a block diagram of the stimulation ch~nnel of
FIG. 3 with two threshold elements and a unit for forming the
excitation threshold, in accordance with the invention;
FIG. 5 is a block diagram of the stimulation channel o~
FIG. 4 with a voltage divider, in accordance with the inven-
tion;
~'IG. 6 is a block diagram of the sti~--~a-~ion channel of
FIG. 5 with a frequency meter, di~ferentiator amplifiers, a
mu~tiplier, an electronic switch, and a second voltage divider,
in accordance with the invention;
~.~
`~ - 15 -
~ ~ .
~577~
FIG. 7 ls a structural dia~r~[l of -the frequency meter of
the electric stimulator in accordance wit~ the invention;
~ IG. 8 is a structural diagram of the multiplier of the
electric stimulator in accordance with the invention;
~ IG. 9 is a block diagram o~ the stimulation channel
of FIG. 6 with a re~erence signal setting unit, a third thre-
shold element and a second electronic switch, in accordance
with the invention;
~ IGS 10 a, b, c, d, e, f, g, h are time plots of electric
signals at the outputs o~ the bioe~ectric activity sensor, the
- first integrator, the adder, the stimulat~g signa~ carrier
frequency oscillatorj the modulator, the bioelectric activity ~.
amplifier, the second integrator, and the comparator of bio-
electric activity, respectively;
~IGS 11 a, b, c, d, e, f`, g, h, i, j, k are time plots
of electric signal~ at the outputs o~ the bioelectric activity
sensor, the first integrator, the bioelectric activity amp~i-
fier, the second intcgrator, the first throshold element, the
second threshold element, the comparator of bioelectric acti-
vit~, the e~citation threshold forming unit, the adder, the
stimulating signal carrier fre~uency oscillator, and the modu-
lator, respectively;
FIGS 12 a, b, c, d, c, P, g, h~ i, a, k, l are time plot~
oY electric signal~ at the outputs of the bioelectric activity
se~sor, the first i~tegrator, the bioelectric activity ampli-
; fier, the second inte~rator, the first threshold element, the
. ~ 16 -
.;.; .
.. . . .. . ...
.
. ~
second threshold element, the comparator of bioelectric acti-
vity, the excitation threshold forming unit, the first voltc~ge
d.ivider, the adder, the ~timulating signal carri~r frequenc~
oscillator, and the modula~or, respectively;
FIGS 13 a, b, c, d, e, f, g, h, i, j, k, l, m, n are
time plots of electric signals at the outputs of the bioelec-
tric activity amplifier, the second integrator, the frequency
meter, the first differentiator amplifier, the second differen-
tiator amplifier, the multiplier, the first electronic switch,
the second voltage divider, the bioelectric activity sensor,
the first integrator, the- first voltage divider, the adder,
the stimulating signal carrier ~requency oscillator, and the
modulator, respectively;
FIGS 14 a, b, c are time plots of electric signals at the
outputs of the reference signal setting unit, the comparator
of bioelectric activity, and the third threshold element.
Referring to the attached drawings, the proposed bioelec- -
trically contro~led electric stimulator of human muscles com-
prlSeS 8iX stimulation channels 1 (FIG~ 1). Each channel 1 in-
cludes a sensor 2 of bioelectric activity of muscles, which
sets a program o~ movements. As shown with reference.to the
sixth stimulation channel 1 o~ the proposed stimulator, the
sensor 2 may comprise electrodes 3 con~ected ~o muscles ~not
shown) of a person who sets a program of movements, and also
con~ected to a bioelectric activity amplifier 4 intended to
ampllfy the bioelectric activity of ~uccles of said person.
, ~ . , .: -- :,.. .. . ..,: ;.: ~ .
,. - . .. t . : .,
1~1S778
The electrodes ~ may be plates attached to the skin. Point or
implantation electrodes can also be used. T~e bioelectric acti-
~ity ampli~ier 4 is of the k~own type.
The bioelectric activit~ sensor 2 can be constructed as
a memory, for instance, of the well i~nown magnetic recorder
type.
'rhe output o~ the bioelectric activity sensor 2 is connec-
ted to the input of an integrator 5. ~he integrator 5 comprises
the well-known amplitude detector and integrating operational
amplifier. ~he output of the integrator 5 is electricall~ coup-
led to an input 6 of a comparator 7 of the bioelectric activit~
o~ muscles of the person, who sets the program of movements, and~
that o~ a person whose moNements are under contro~. ~he compa-
rator 7 is conventionally built around an operational amplifiar.
~ he output of the comparator 7 is electrically coupled
to a control input 8 o~ a modulator 9 constructed as the well-
-known controlled ~oltage divider~ An input 10 of the modula-
tor 9 is connected to the input of an oscillator 11 of the
carrler frequency of an electric sig~al which stimulates mus-
cular activity. The oscillator 11 is common for all the channels
he oscillator 11 can be embodled as follows, dependin~ on
a desired type and shape of said electric signal.
I~ a sinusoidal electric signal is to be produced at the
output of the oscillator 11, the latter may be constructed as
the well-known master oscillator with ~C circuits, or -the
wcIl~ nown master o~3c;l.llator built around l~C ele~ rlts.
If it is necessary tb produce an electric si~gnal in the
'
- 18 -
.. . ..
,. ,. :, , : .
... :- ,~ :,. .
~.15778
form of unipolar pulses at the output of the oscillator 11,
the latter comprises the well-known self-excited multivibrator
and one-shot multivibrator placed in series.
The output of the modulator 9 is connected by means o~ a
power amplifier 12 to an input 13 o~ a unit 14 for separating
the electric signal, which stimulates the muscular activity
of the person whose movements are under control, and the bio-
electric activity of that person's muscles, caused by said
stimulating signal. I
If a sn usoidal stimulating signal is used, the ~plifier
12 is constructed as the known low-frequency arnplifier with a
transformer output.
In this ~ase the separation unit 14 comprises seriesly
connected filters 15 ~FIG. 2) and 16. The filter 15 is the
well-known symmetrical high-~requency filter, whereas the fil-
ter 16 is the well-known syrnMetrical low-frequency filter.
An input 17 (~IG. 1) and an output 18 of the separation
unit 14 are connected to electrodes 19 con~ected to muscles of
the perfion whose movements are under control. ~he electrodes
19 are similar to the electrodes 3. An output 20 of the sepa-
ration unit is connected to the input of an a~plifier 21
(FIG. 1) of bioelectric activity of muscles of the person
whose mo~ements are under co~trol.
In case of using a pulse stimulating signal, the power
ampli~ier 12 is the known pulse ampli~ier with a trans~or~er
output.
In this case the separation unit 14 comprises, as is
- 19 -
,
. . . , . ~ ... . .
.shown with reference to the sixth channel 1 of the proposed
stimulator, two seriesly placed electronic switches 22 and 23
o~ the k~own symmetrical type. An input 24 of the electronic
~witch 22 and an input 25 of the electronic switch 23 serve as
the inputs 13 and 17, respectively, of the separation unit 14.
'The outputs of the electronic switches 22 and 23 are the ~ -
outputs 18 and 20, respectively, of the separation unit 14.
Control inputs 26 and 27 of the elsctronic switches 22 and 23,
respectively, are connected to the input 24 o~ the electronic
- switch 22.
~ The bioelectric activity amplifier 21 is ~imilar to the
amplifier 4.
'~he output of the amplifier 21 is connected to the input
of an integrator 28 which is similar to the integrator 5. '~he
output of the integrator 28 is electrically coupled to an in-
put 29 of the comparator 7 of` bioelectric activity.
FIG. 3 shows one stimulation channel of an electric sti-
mulator which is similar to the one described above. 'The diffe-
rence between the two embodiments is that in the latter case,
the inputs 6 and 29 of the comparator 7 of bioelectric activity
are directly connected to the outputs of the integrators 5 and
28, respectivel~. 'l`he output of the comparator 7 is connected
to an input 30 of an adder 31. An input 32 of the adder 31
is connected to the output of the integrator 5. '~he output of
said adder 31 is conneoted to the control input 8 of the modu-
lator 9.'l'he adder 31 is the known summing opera-tional ampli-
fier.
; " 2 0
,. , ~ .
` -
778
FIG. 4 shows one ch~nnel oY an electric stimulator simi-
lar to the one described abo~e. However, unlike the embodi-
men-t of ~IG. 3, the inputs 6 and 29 of the comparator 7 are con
nected to the outputs of the integrator 5 and 28 by means of re-
spective threshold elements ~3 and 34.
In this case the comparator 7 is the known flip-flop
with separated inputs. ~he circuitry of the threshold elements
33 and 34 is that of the known operational amplifier.
~ he output of the comparator 7 is connected to an input
35 of a unit 36 for ~orming the excitation threshold of muscles
of the person whose movements are under control. An input 37
of the unit 36 is connected to the output of the threshold
element 33; the output of the unit 36 is connected to the
input 30 of the adder 31. The excitation threshold forming
unit 36 is the known capacitor storage.
Unlike the embodiment of FIG. 4, the electric stimulator,
one of whose channels is shown in ~IG. 5, comprises a conven-
tiona~ voltage divider 38. An input 39 of the voltage divider
38 is connected to the output of the integrator 5. A control
input 40 of the volta~e divider 38 is connected to the output
of the excitation threshold forming unit 36.
Unlike the embodiment of FIG. 5, the electric stimulator,
one of whose chan~els is shown in FIG. 6, comprises a frequency
meter 41 whose input is connected to the output of the bioelec-
tric activity amplifier 21. ~he output of the frequency meter
41 is connected to a differentiator amplifier 42.
~ he frequency meter 41 contains in series a limiter 4
.. '' ~.
_ 21 -
., , i , ., . . ~ , . , . ,
, . . . ` - ., :
:1~.15~78
(FIG. 7) o~` bioelectric muscular activity o~ the person
whose movements are under control, a threshold element 44,
a generator 45 o~ standard duration pulses, and an integrator
46.
The circuitry of the bioelectric activity limiter 43 is
of the known type. The threshold element 44 is a Schr~itt
trigger. 'rhe generator 45 o~ standard duration pulses is a
one-shot multivibrator. '~he integrator 46 and the differeiltiator
amplifier 42 (FIG. 6) are of the known type.
Connected to the output of the integrator 28 is a dif~e-
rentiator amplifier 47 which is similar to ~he dif~erentiator
amplifier 42. '~he outputs o~ the differentiator amplifiers 42
and 47 are connected to inputs 48 and 49, respectively, of a
multiplier 50. i~he multiplier 50 comprises threshold elements
5~ (FIG. 8) and 52 whose i~puts are the inputs 48 (~IG. 6) and
4~ of the multiplier 50, whereas their outputs are connected
to respective inputs 53 (FIG. 8) and 54 o~ a logicaL A~ cir-
cuit 55. The output of the logical A~D circuit 55, which ser~es
as the output o~ the multip~ier 50 (~IG. 6), is connected to
a control input 56 o~ an e~ectronic switch 57. An input 58 of
the electronic switch 57 is connected to the output of the
frequency meter 41.
'~he threshold elements 51 (FIG. 8) are Schmibt trig~ers.
l'he logical AND circuit 55 and the electronic switch 57 (~`IG.6)
are of the known type.
Connected to the output of tke electronic switch 57 is a
control input 59 of a voltage divider 60 whose input 61 is
connecte~ to the output of the e~citation threshold for~ing
';
~ 22 -
unit 36. r~he output o~ t~e voltage divider 60 is connected to
the input 30 of ~he adder 31~ ~he voltage divider 60 is simi-
lar to the voltage divider 38.
FIG. 9 shows one channel of an electric stimulator which
i~ similar to the embodiment of ~IG. 6. The difference between
the two embodiments lies in the fact that in the ~atter case
the stimulator includes a reference signal ~etting unit 62
whose input is connected to the output of the threshold element
33. '~he reference si~nal setting unit 62 is a sta~dard dura-
tion pulse ~enerator similar to the generator 45 (~IG. 7).Con-
nected to the output of the reference signal setting unit 62
(FIG. 9) is an input 63 of a threshold element 64 which i9
the well-known logical ~ND circuit. An input 65 of the thre~
shold element 64 is connected to the output of the comparato~
7 of bioelectric activity. ~o the output of the thresho~d
element 64 there is connected a control input 66 of an elec-
tronic switch 67. An input 68 of the electronic switch 67
is connected to the output of the modulator 9, whereas t~e
output of the electronic switch 67 is connected to the powe~
amplifier 12. ~he electronic switch 67 is similar to the elec-
txonic switch 57.
he known circuitries of the above-mentioned bioelectr~ic
activity amp~i~ier 4 (~IG. 1), integrators 5, 28 and 46
(FIG. 7~ compara~or ~IG. 1) of bioelectric activity,-os-
cillator 11, separation unit 14, adder 31 (~IG. 3), dif~eren-
.
tiator ampli~iers 42 (FIG. 6) and 47, modulato~ 9, voltage
divider 38, power amplifier 12, threshold elements 33 and 34,
, .: .. . .. . . . . . .
: :-. . . . . - , ~ ~ .
~.lS~q8
excitation threshold forming unit 36, limiter 43 (FIG. 7),
generator 45, and reference signal setting unit 62 (~IG. 9)
are described in the ~ollowin~ sources: the article by Vodovnik
and Mc~aud in the journal "Electronica", Moscow, 1965, pp~ 32-
-39; N.G.Bruyevich, B.G.Dostupov, "Osnovy teorii schyotno-
-reshayushchikh ustroistv" /"~undamentals of Computer Theory"/,
l~oscow, 1964, p. 249; "Spravochnik po radioelectronike"
/"Handbook of Radio Electronics"/, ed. by A.A.Kulikovsky,
Moscow, 1970, vol. 3, pp. 285, 526, 97-200, 286; Aprikov,
"Upravlyayemye deliteli nizkoi chastoty" /"Cont~olled ~ow
~requency Dividers"/, Moscow, 1969, p. 27; A.N.Starostin~
"Impulsnaya technika" /"Pulse ~ngineering"/, Moscow, 1973,
pp. 278,288,300,175; R.S.~sykin '~silitelnye ustroistva"
/"Amplifiers"/, Moscow, 1971, p. 141; B.A.Varshaver "Ras~chyot
i proyektirovaniye impulsnykh usiliteley" /"~he Calculation
and Designing of Pulse Amplifiers"/, ~oscow, 1975; "Spravoch-
nik po telemetrii" /"Eandbook of Telemetry"/t ed. by E.~.
Grunberg, Moscow, 1971, p. 58; ~.M.Goldberg, "Impulsnye i
tsi~rovye ustroistva" /"Pulse and Digital Devices"/, ~oscow,
1973, pp. 240-265; I.M.Bolotin, V.A.Pavlenko, "Porogovye
ustroistva dlya priborov avtomatichesko~o controlya i reguliro-
vaniya" /"~hreshold Devices ~or Automatic Control and 4djust-
ment ~`quipment"/, Moscow, 1970, p. 6; ~.I.Gryaznov, ~.A.Gur-
vich, ~.V.Mograchyov, "Izl~ereniye impulsnykh naprya~heniy"
/"Pulse Voltage l~qeasurement"/, Moscow, pp. 134-149; I.S.Itskhoki,
N.I.Ovchinnikov, "Impulsnye i tsifrovye ustroistva" /"Pulse
- 24 -
. ,., . , ~.
, . . . . .
.
1~.1577~3
and Digital Devices"/, ~lloscow, 1972, p. 509).
For better understanding of the operation of the proposed
electric stimulator, ~IG~ 10 a, b, c, d, e, f, g, h show time
plots o~ electric signals at the outputs of the bioelectric
activity sensor 2 (FIG. 1), the integrator 5, the adder 31
(FIG.3), the stimulating signal carrier frequency oscillaJor
11, the modulator 9, the bioelectric activity a~plifier 21, the
integrator 28, and the comparator 7 of bioelectric activity,
respectively.
FIGS 11 a, b, c, d, e, f, g, h, i, j, k are time plots
of electric signals at the outputs o~ the bioelectric activity
sensor 2 (~IG. 4), the integrator 5, the bioelectric activity
amplifier 21, the integrator 28, the threshold element 33, tke
threshold element ~4, the comparator 7, the excitation thre-
shold ~orming unit 36, the adder 31, the stimulating signal
carrier frequencg oscillator 11, and the modulator 9, respec-
tively.
FIGS 12 a, b, c, d, e, f, g, h, i, j, k, l are time
plots of electric signals at the outputs of the bioelectric
activity sensor 2 (FI2. 5), the integrator 5, the bioelectric
activity amplifier 21, the integrator 28, the threshold element
33, the threshold element 34, the comparator 7, the excitation
threshold forming unit ~6, the voltage divider 38, the adder
31, the stimulating sig~al carrier frequency oscillator 11,
and the modulator 9, respectively.
FIGS 1~ a, b, c, d, e, ~, g, h, i, j, k, l, m, n are
time plots o~ electric signals at the outputs of the bioelec-
- 25 -
;:
- , . ......
.. , , , - ~ , ., ;:.
. ~ ~ .. . . .. .
.... ..
1~1577~
tric activity amplifier 21 (~`IG. 6), the integrator 2~, the
f`requency meter 41, the differentiator amplifier 42, the diIfe-
rentiator amplifier 47, the multiplier 50, the electronic
switch 57, the voltage divider 60, the bioelectric activity
sensor 2, the integrator 5, the voltage divider ~8, the adder
31j the stimula~ing signal carrier frequency oscillator 11, and
the modu~ator 9, respectively.
~ IGS 14 a, b, c are time plots o~ electric signals at
the outputs of the reference signal setti~g unit 62 (FIG. 9),
the comparator 7, and the threshold element 64.
In the above-mentioned time plots, time t is plotted as
abscissas, and the amplitude U of electric signals is plotted
as ordinates. The ~mplitude U0 is equal to a stimulating sig-
nal arnplitude corresponding to the excitation threshold of
uluscles bein~ stimulated. 'l'he amplitude Uma~ corresponds to a
maxi~num ~rlplitude ~f the stinlulatin~ signal. '
'i'he foregoing embodiments of the proposed bioelectricall~
controlled electric stimulator of human muscles operate as fo~-
.
lows.
When the sensor 2 (FIG. 1) comprises the seriesly connec-
ted electrodes ~ connected to muscles o~ the person, who sets
a pro~ram of movements, and the ampli~ier 4~ the bioelectria
activity is directl~ picked with the aid of the electrodes 3
~of each stimulation channel 1 (FIG. 1) of~ these muscles,
as the person performs a movement. ~he bioe~ectric activity is
amplified by the an~ ier 4 so that at the output of the sen-
- 26 -
. ~ ,. . .
- . : .
, . ~ .. .. .
:. . . .
1~.15778
sor 2 there is produced ~n amplified version of the bioelec-
tric activity of the person who sets the program o~ movements.
In case of using the electrodes 3 of the surface type, the
bioe~ectric activity is represented as the electric signal o~
FIG. 10 a.
~ ,~en the sensor 2 is a magnetic recorder, ~rom this sen-
sor there is taken the prerecorded and preamplified bioelectric
activity of muscles of the person who sets the program of mo-
vements, which is represented as the electric signal o~ FIG.
10 a.
From the ou~put o~ the bioelectric activity sensor 2, the
electric signal is applied to the input o~ the integrator 5 in-
tended the separate the useful information on the progra~med
movement from said signal. The integrator 5 detects and inte-
grates the electric signal. At the output of the integrator 5
tnere is produced the program electric signal shown in FIG.10b.
rhis signal represents the time-averaged bioelectric activity
of muscles of the person who sets the program of movements.
From the output of the integrator 5, this electric signal i~
applied to the input 6 of the comparator 7 o~ bioelectric acti-
:
vity. At an initial period of time ~)1 (FIG. 10 b), there isno electric signal carrying information on the per~ormed move-
ment at the input 29 o~ the comparator 7, because the stimula-
ting signal has not yet reached the excitation threshold U0
of the muscles being stimulated. Therefore, during this period
of time at the output of the comparator 7 there appears an elec-
tric signal whose shape and amplitude coincide with those o~
.
.
- 27 -
.. . .-
- ~ .. . . ..
- : , , , . . :
1~577E~
the signal applied to the ir.put 6 of said cornparator 7. ~hi~ slg-
nal is shown in FIG. 10 b.
I~'rom the output o~ ~he comparator 7, the electric signal
is applied to the control input 8 of the modulator 9. From tne
output of the stimulating signal carrier ~requency oscillator
11 to the input 10 of the modulator 9 there is applied a sti-
mulatin~ electric signal. ~he signal is applied in the form of
unipo~ar square pulses shown in ~IG. 10 d. In order to reduce
pain and increase thé ~orce of contraction o~' the muscles be-
ing stimulated, it is advisable that the duration of pulses
should be 0.1 to 0.5 msec, whereas the pul~e repetition f'requen-
cy should be 80 to 200 Hz. The ~unction of the stimulating
signal can ~lso be performed b~ bipolar square pulses or a si-
nusoidal signal whose ~re~uehcy is selected to be equal to
2 to 5 khz for the above reasons.
'~he use o~ sinusoidal electric signals at ~requencies OI 2
to 5 Hz for electric stimulation is due to the ~act that the~
are less pain~ul than other electric signals.
'~he modulator 9 converts the stimulating electric signal
shown in ~IG. 10 d so that at its output there is produced an
electric signal whose t~pe and shape coincide w~th those of
the stimulating signal, i.e. a sequence o~ square pulses whose
amplitude chan~es with time as the amplitude o~ the program
signal. ~'rom the output o~ the modu~ator 9, the converted sti-
mulating signal is applied to the input of the power amp~i ier
12 ~d is amplitude-amplified to a level required for stimula-
tion. The~, the signal is applied via the separation unit 14
- 28 -
... ..
~ lS77B
to the electrodes 19 connected to the muscles beinO stimulated.
I~ at the output of the oscillator 11 there i6 for~ed
the stimulating pulse signal shown in FIG. 10 a, the conver-
ted stimulating signal is applied ~rom the output of the po~er
amplifier 12 via the electronic switch 22 (~IG. 1) to the elec-
trodes 19 connected to the muscles of the person whose movernents
are under control. As a result, these muscles are excited and
contract. During time intervals between the pulses, the resul-
tant bioelectric activity of the muscles being stimulated is
applied via the electronic switch 23 to the input of the bio-
electric activity a~pli~ier 21.
During the action o~ the stimulating signal pulses, the
electronic switch 22 is conducting, and the stimulating signal
is applied to the electrodes 19. Meanwhile, the electronic
switch 23 is not conducting, and the stimulating sigrnal is not
applied to the input of the bioelectric activity amplifier 21.
During the intervals between the stimulating signal pulses the
electronic switch 22 is not conducting, and the intrinsic noise
of the power amplifier 12 cannot reach the input of the bio-
electric activity ~mplifier 21. ~eanwhile, the electronic
switch 23 lS conducting, and the bioelectric activity of the
musoles being stimulated is applied from the output of the
electrodes 19 to the input of the amplifier 21.
If a s mùsoidal stimulating signal is formed at the out-
put o~ the oscillator 11, the frequency separation o~ this
signal from the bloelectric acti~ity of the muscles being sti-
mulated, carried out by the separation unit 14 constructed as
-- 29 --
,. ., .. ` . . ` . , ` . , . ~ ..
~ 57~7~
shown in FIG. 2, is made possible due to the faet that the
ran~e of bioelectric activity of muscles, which includes fre-
quencies of 0 to ~00 Hz, is much lo~er than the stirnulating
5 ignal frequency. In this case the stimulating signal is appli-
ed from the output o~ the power amplifier 12 via the high-fre-
quency filter 15 (~IG. 2) to the electrodes 19 connected to
the muscles being stimulated~- As a result, the muscles being
stimulated are excited and contract. ~he electrodes 19 pick up
the resultant bioelectric activity which is applied via the
low-fxequency filter 16 (~IG. 2) to the input of the bioelec-
tric activity arnplifier 21 (FIG. 1).
The low-frequency filter 16 (~IG. 2) performs the basic
function o~ separating the sinusoidal stimulating signal having
a frequency of 5 Hz, for example, from the bioelectric activi-
ty of the musc~es being stimulated. It is desirable that the
transmission band of the filter 16 should be 0 to 800 Hz,
because the ma~imum bioelectric activity of the muscles
being stimulated is found within this ~requency band.
~ he high-frequency filter 15 is intended to avoid the
nclusion of the intrinsic noise of the power amplifier 12
(FIG. 1), whose freque~cy is within the bioelectric activity
frequency band, in the bioelectric activity of the musc~es
bein~ stimulated~ ~he filter 15 (~IG. 2) also serves to cor~e-
late the output resistance of the power amplifier 12 with the
inter-electrode resistance of the tissues being stimulated ~n~
remove the bioelectric activity from these tissues.
It is advisable that the cutoff frequency of the high-
-- ~0 --
., , ., :: .
: :, : ~ : :` ! :`:
.15778
-fre~uency filter 15 should be somewhat lower than the frequen-
cy of the stimulatlng signal. For example, at a frequency of
the stimulating signal of 5 khz, the cuto~`f f`requency of the
filter 15 should be 4 khz.
From the output of the amplifier 21 (~IG. 1), the bio-
electric activity of the muscles being stimulated is applied
to the input o~ the integrator 28. As the integrator 5, the
integrator 28 separates the useful information on the movement
performed by the person whose muscles are being stimulated.
At the output of the integrator 28, there i~ produced an
electric signal which is the time-averaged bioelectric activity
of the muscles being stimulated and carries information on the
movement being performed. ~his information signal is applied
to the input 29 of the comparator 7, to whose input 6 there is
applied a program signal from the output of the i~tegrator 5.
q'he comparator 7 compares the instantaneous amplitude
values of the program signal with those of the information
signal. At the output of the comparator 7 there is produced a
signal which adjusts the program signal, depending on the type
of electric coupling between the output of the comparator 7
and the control input 8 of the modulator 9, which types are
described be`low, with reference to other preferred embodiments
of the proposed electric stimulabor. ~he correction of the ~-ro-
; gram signal ensures correspondsnce between the actually perfor~
and programmed movements.
'I'he corrected program signal is applied to the control in-
; - 31 -
l~.lS77~3
put 8 o~` thei:modulator 9, to whose input 10 there is applied
the stimulating signal ~rom the oscill~tor 11. At the output
o~ the modulator 9 there is ~ormed a stimulating signal conver-
-ted in accordance with the corrected program signal. '~his sig-
nal is amplified b~ the ampli~ier 12 and applied via the sepa-
ration ~lit 14 to the electrodes 19 and to the ~uscles being
stimulated. ~he signal ensures correspondence between contrac-
ti~i.3 o~ these muscles and contractions o~ the same muscles o
the person setting the program of movements.
'~he operation o~ the stimulator of FIG. ~ is similar to
that o~ the stimulator of FIG. 1. The difference is that in
each stimulation channel 1 (~IG. 1), the program signal shown
in h`IG. 10 b is applied ~rom the output on the integrator 5 to
the input 6 of the comparator 7 and to the input 32 (~'IG. 3) o~
the adder 31. During the initial period of time ~ IG. 10 b),
the amplitude o~ the program si~nal and, consequently, the ampli-
tude of the stimulating signal do not reach U0 corresponding
to the excitation threshold o~ the muscles being stimulated;
there is no signal at the input 29 o~ the comparator 7. As a
.
resu~t, at the output of the comparator 7 there is produced
a program sig:al shown in ~IG. 10 b. rrhis program signal is
applied to the input ~0 o~ the adder 31. Wibhin the period of
time from 0 to t1~ at the output o~ the adder 31 there is pro-
duced the electric signal shown in ~'IG. 10 c. 'l'he amplitude o~
thls signal is double the amplitude o~ the program signal shown
in P`IG. 10 c by the dash line.
~ .
:::
~ 2 -
.157 7~
~ rom the output of the adder ~1, this signal is applied
to the input 8 of` the modulator 9. ~he modulator 8 converts the
stimulating signal shown in ~IG. 10 d so that at its output
t~ere is produced the signal shown in ~IG. 10 e. This si~nal
is a sequence of unipolar square pulses shown in FIG. 10 d,
whose amplitude changes vlith time in accordance with the change
in the program signal shown in ~IG. 10 c.
It is clear ~rom the above and from the time plots of
FIGS 10 c and 10 e that due to the presence of the multiplier
31~ the amplitude of the converted stimulating signal reaches
the value of UO~ which corr~sponds to the excitation threshold
of the muscles being stimulated not as the amplitude of the
program signal does, i.e. during the period of time ~1~ but
two times faster, i.e. during the period of time ~ 2 (~IG. 10 e)
As a result, the time lag between the appearance of the program -
signal and the onset of bioelectric activity of the muscles
being stimulated, shown in FIG. 10 Y, is reduced about one
hal~ and is equal to ~ 2.
As the information signal shown in FIG. 10 g appears at
the output of the integrator 28 and as this signal is applied
to the input 29 o~ the comparator 7, at the output o~ said com- -
parator 7 there appears during the period of time (t1 - t2)
(FIG. 10 h) a correction signal whose amplitude at any moment
o~time is equal to the dif~erenoe between the instantaneous
amplitude values o~ the program signal and the information
signal. ~he adder 31 (FIG. 3) adds this correction signal to
the program signal applied to its input 3~2, which decreases the
.
~ 33 -
., , . - .
.
~11577B
value of the signal at its output, as shown in FI&. 10 c.
~his results in a distortion o~ the amplitude-time relation-
ship between the oùtput signal of the adder 31 and the program
~ignal at its input 32. ~he distortion manifests itself in that
an increase in the amplitude of the program signal during the
period of time (t1 - t2) (~IG. 10 c) is accompanied by a
decrease in the amplitude of the signal at the output of the
adder 31 (~IG. 3). ~his occurs until the instantaneous value
of the program signal amplitude is equal to that of the inf ar- :
mation signal. In this case at the moment of time t2 (FIG.10h),
the amplitude of the signal at the output of the comparator 7
is zero, whereas at the output of the adder 31 (~IG. 5) it is
equal to the instantaneous value of the a~plitude of the pro-
gram signal at its input 32. ~his means that at the moment
of time t2 (FIG. 10 c) the adder 31 ~IG. 5) does not correct
the program signal.
During the period of time that follows, overcompensation
occurs due to the time lag of the system, and there may come a
moment when the instantaneous amplitude value of the informa-
tion signal is in excess of that of the program signal.
In this case a negative correction signal appears at the
output of the comparator 7 during the period o~ time (t2 - t3)
(FIG. 10 h). ~he adder 31 (FIG. 3~ adds this signal to the
program signal, whereby the amplitude o~ thè sig~al a~ the
output of the adder 31, shown in ~IG. 10 c, is reduced by a
value which is equal to the difference between the instanta-
neous amplitude values of the program and information signals.
- 34 -
. . , :.- - . ,- ~, ~ .
~ 577t~3
~ he processes which take place during the priod of ti~e
(t3 - t4) (~IG. 10 h) are reversed, as compared to the processes
that take place during the period of time (t2 - t3). During this
period of time, the output signal of the adder 31 (~IG. 3),shown
in ~IG. 10 c, increases in amplitude, as compared to the pro-
gram signal shown in ~IG. 10 c b~ the dash line. ~hus, the
progra~ signal is corrected again to ensure correspondence bet-
ween the instantaneous amplitude values of the program and in-
formation signals.
The fact that the time lag ~ 2 f the information signal
relative to the program signal is reduced by half, as compared
to the known stimulator described above, accounts for an impro-
ved correspondence between the actually performed and programmed
movements. However, this is only true of the stead~-state opera-
B ting conditions, i.e. during the periods of time (t2 - t
(~IG. 10 h).
The operation of the electric stimulator of FIG. 4 is
similar to that of the stimulator of ~IG. 3. ~he difference is
that in each stimulation chPnnel 1 (FIG. 1), the pro OEam sig-
nal is applied from the output of the integrator 5 to the input
of the threshold element 33 (FIG. 4), at whose output there is
formed a square pulse of a constant amplitude, shown in ~IG.
11 e. ~he duration of this pulse is determined b~ that of the
program signal at the output of the integrator 5. The square
pulse is applied to the input 37 of the excitation threshold
forming unit 36 and the input 6 of the comparator 7.
~ he information signal shown in FIG. 11 d is-applied from
' ' '
; -- ~5 --
. ~ , . .
' . ' ' ' ', ~" ',. " '. . ` . ~ '
- ~.1577~3
the output of the integrator 28 to the input of the threshold
element 34 after a time lag ~ 3 (FIG. 11 d) rel~tive to the pro-
gram si~nal. At this moment, at the output of the threshold
element 34 there is produced 8 square pulse shown in FIG.11 f,
which is applied to the input 29 of the comparator 7. At the
latter's output there is produced a square pulse of a constant
amplitude, shown in FIG. 11 g, whose duration is equal to the
time lag ~3 of the information signal relative to the program
signal. ~he time lag is proportional to the excitation threshold
of the muscles being stimulated, so the duration of this pulse
corresponds to the excitation threshold. From the output of the
comparator 7 the s~uare pulse is applied to the input 35 of the
excitation threshold forming unit 36, to whose input 37 there
is applied, as is mentioned above, the square pulse shown in
FIG. 11 e. At the output of the unit 36 there is produced a
pulæe ~hown in FIG. 11 h, which exponentially rises during the
pexiod of time ~ 3. The aplitude of this pulse is proportional
to the duration of the pulse shown in ~IG. 11 g, i.e. to the
excitation threshold of the muscle~ being stimulated. ~he dura-
tion of this pulse i~ determined by the duration of the pulse
shown in FIG. 11 e, which means that it is determined by the
duration of the program signal shown in FIG. 11 b. ~he rate
of rise of the pulse at the output of the excitation thre-
shold forming unit 36 is selected and adjusted with reference
to a minimum of pain caused by the electric stimulation. At
the same time it is advisable that the rate of rise should be
one order higher than the maximum rate of change in the pro-
gram signal.
- 36 -
- ~ .
f~ 5~78
~ he pulse for~ed at the output of the unit 36 serves as
the correction signal and is applied to the input 30 of the ad-
der 31. At the latter's output there is produced an electric
signal shown in ~IG. 11 i. The amplitude o~ this signal is
equal to the su~ total of the amplitudes of the program signal
and the correction signal correspondin~ to the excitation thre-
shold of the muscles being stimulated. ~he corrected program
signal is applied to the in~ut 8 of the modulator 9, to whose
input 10 there is applied the stimulating signal in the form
of square pulses shown in ~IG. 11 j. At the output of the modula~
tor 9 there is produced a converted stimulating signal ~o~m in
FIG. 11 k. At each moment of time, the amplitude of thi~ signàl
is equal to the sum total of the amplitudes of the pro~ram sig-
nal and the correction signal.
As a result, the electric signal is applied to the muscles
not from the zero level, but from a level eQual to the excita- ;
tio~ threshold Or the muscles being stimulated, which conside-
rably reduces the time lag of the in~ormation signal relative
to the program signal. The time lag is only determined by the
time of rise of the pulse at the input of the excitation thre-
shold forming unit 36.
The stimulator of FIG. 5 operates in a manner similar to
the operation of the stimulator of FIG. 4. ~he difference is
that in the latter case in each stimulation channel 1 (FIG. 1),
the program signal shown in FIG. 12 b, which is produced at the
onset o~ a prescribed bioelectric activity shown in FIG. 12 a,
is applied from the output of the integrator 5 not only to the
- 37 -
~ .
''' 1~.~ ~ 8
input of the threshold ~lement 33 (FIG. 5), but also to the in-
put 39 of the voltage divider 38. ~o the input 40 o~ said vol-
tage divider 38 from the output of the excitation threshold
formin~ unit-36 there is applied a correction signal in the
form of an exponentially rising pulse shown in FIG. 12 h.This
pulse adjusts the transfer ratio of the voltage divider 38 so
that at the,latter's output the amplitude of the converted
program signal is not in excess of ~K - 1) UO, where UO is the , '.
amplitude of the correction signal, corresponding to the exci-
tation threshold of the muscles being excited. ~he foregoing
amplitude ratio is selected for the following reasons.
~ he maximum amplitude Umax of the converted stimulating
signal is related to the excitation threshold of the muscles
being stimulated through the proportionality factor E. ~here-
fore, in order to ensure that the amplitude of the converted
stimulating signal is not in excess of a maximum value, it is
necessary that the maximum amplitude of the program signal,
added to the amplitude of the correction signal, which corres-
ponds to the excitation threshold of the muscles being stimula-
ted, should not be in excess of the maximum amplitude of the
converted stimulating signal. This means that the maximum
amplitude Or the converted program signal must not be in ex-
: cess of (K - 1)-Uo. ~his is taken care o~ b~ the voltage di-
vider 38.
At the output of the voltage divider 38 there is formed
a converted program signal shown in FIG. 12 i, whose maximum
amplitude is not greater than UO.
-, - 38 -
ll~S778
In the time plots of ~IG. 14, K ~ 2, which means that
the maxi~um amplitude o~ the converted program signal is not
in excess of a value corresponding to the excitation threshold
Or the muscles being stimulated.
~ rom the output of the ~oltage divider 38,the co~verted
program signal is applied to the input 32 of the adder 31, to
whose input 30 there is applied a correction signal whose
amplitude is proportional to the excitation threshold of the
muscles being stimulated. At the output of the adder 31 there
is produced a corrected program signal shown in ~IG. 12 ~, whose
amplitude at any moment of time is equal to the sum total of
the amplitudes Or the above-mentioned signals applied to the
inputs 30 and 32 of said adder 31. The maximum amplitude of
this signal is not in excess of double the frequency corres-
ponding to the excitation threshold Or the muscles being
stimulated. ~his sig~al is applied to the control input 8 of
the modulator 9, to whose input 10 there is applied the stimu-
lating signal in the form of pulses shown in FIG. 12 k.
At the output of the modulator 9, there ic produced a
converted stimulating signal shown in FIG. 12 l. ~he minimum
~ ! ~
~ value of the amplitude of this signal is equal to U correspon-
o
; ding to the excitation threshold Or the muscles being stimu-
~ lated, whereas its maximum value is equal to 2U . ~hus the
~ . o
e}ectric si~nal is applied to the muscles being stimulated
from a level corresponding to the excitation threshold of
these muscles, and the~maximum amplitude of this signal is
not greater than the maximum amplitude of the stimulating sig-
~ .
9 _
. ... . ;. . . ,. - , .. .
, . ~. . . ~ ` . , . ` .
.. .,, . . . ~ . ~ .. ,
~ . . ~, . . .
..,. . .. . ;.. , . . . ,.. . .. . , .
.; . - .,.. , . .. : .. :,: - . ' ` .
- . . .. . ~ . .
^
5~7 ~
nal for these muscles. As a result, the person whose muscles
are being stimulated feels less pain and the muscles which are
being stimulated are excited and contract in accordance with
the exc tation and contraction of the muscles of the person
who sets the program of movements; the actually performed
movement corresponds more fully to the programmed movement.
In the course of electric stimulation, the excitation
threshold of the muscles being stimulated varies (as a rule,
it rises); conseque~tly, the amplitude of the converted stimu-
lating signal applied to the muscles is also changed. It fol-
lows that during the stimulation process the dynamic ra~ge of
the program signal shown in ~IG. 12 b is adjusted to ~he chan-
ging functional state of the muscles of one person, or diffe-
rent functional states of muscles being stimulated of differen~
persons.
~ he operation of the stimulator shown in ~IG. 6 is similar
to that of the stimulator of FIG. 5. ~he difference is that in
each stimulation channel 1 (~IG. 1), the electric signal shown
in ~IG. 13 a is applied from the output of the bioelectric
activit~ amplifier 21 to the input of the integrator 28 and
the input of the frequency meter 41 (~IG. 6). At the output of
the frequency meter 41 there is produced an electric signal
sho-~n in FIG. 13 c, whose amplitude is proportional to the
mean bioelectric activity frequency of the muscles being sti-
mulated at a given moment of time. ~rom the output of the fre-
quency meter 41, this signal is applied to the input of the
differentiator amplifier 42, at whose output there is produced
_ 40 _
.. ,. ,., ., . ~, ~... .
. .
.: ,: "` ~ - i
~ ~ . . . . ... . ..... . .
- "
l~.i~B
an electric signal shown in FIG. 1~ d. At an~ ~oment of time
the amplitude of this signal is proportional to the rate of
change of the mean bioelectric activity frequency of the mus- -
cles being stimulated.
If at a given moment the mean bioelectric activit~ fre-
quency is increasing, this signal is positive; if the mean
frequency decreases, the signal is negative. ~he signal of po-
sitive or negative polarity is applied to the input 48 of the
multiplier 50.
~ rom the output of the integrator 28, the time-averaged
bioelectric activity of the muscles being stimulated, shown in
~IG. 13 b, is applied to the input of the differentiator ampli-
fier 47 at whose output there is formed a signal shown in ~IG.
13 e. ~he amplitude of this signal is proportional to the rate
of change of the amplitude of the time-averaged bioelectric
activity of the muscles being stimulated. ~his signal may be
of positive or negative polarity, dependin~ on whether the
amplitude of the signal applied to the input of said differen-
tiator amplifier *7 increases or decreases at a given moment
.
of time. The signal is applied to the input 49 of the multi-
plier 50. At the output of said multiplier 50 there is produced
a square pulse shown in ~IG. 13 f; this occurs only within the
period of time (t1 - t2), when signals of dif~erent polarity
are applied to the inputs 48 and 49 of said multiplier 50.The
reason is as follows.
It is Xnown that an increase in the force developed by a
wor~ing muscle is accompanied by an increase in the amplitude
of the time-averaged bioelectric activity of this muscle, as
`~ - 41 -
: ~ , . . .. , ~ ;
. . . . ... . . . .
.. . . .. . .
- . ~
. . ~ : . . . : : . : , . , j
~ 5778
well as by an increase in the mean bioelectric activity fre~u-
ency of this muscle,and vice ~ersa. Eowever,if the working
muscle is tired, for exa~ple, at the period of time (t1 - t2)
under the conditions of a standard load both for static and
dynamic work, the amplitude of the time-averaged activit~
shown in ~IG. 13 b increases, whereas its fre~uency decreases,
as shown in ~IG. 13 c. The greater the contraction force, the
greater the decrease in the frequency. ~herefore, if the muscles
of the person, whose movements are under control, are tired
during the period of time (t1 - t2), at the output of the multi-
plier 50 there is produced a signal shown in ~IG. 13 f, which
is applied to the control input 56 of the switch 57. ~ro~ the
output of the frequency meter 41 to the input 58 of said switch
57 there is applied a signal shown in ~IG. 15 c, which reaches
the control input 59 of the voltage divider 60 during the period
of time (t1 - t2) (~IG. 13 g). To the input 61 (~IG. 6) of the
voltage divider 60 there is applied a signal corresponding to
tha excitation threshold of the muscles being stimulated.
At the output of the voltage divider 60 there is produced
an electric signal shown in ~IG. 13 h. ~t the period of time
(t1 ~ t2), the amplitude of this signal decreases in accordance
with the deorease in the amplitude of the signal applied to
the input 59 o~ the voltage divider 60, i.e. in accordance with
the change in the bioelectric activity frequenc~ of the muscles
being stimulated.
This signal, corresponding to the excitation threshold
of the tired muscles, arrives at the input 30 of the adder 31
- 42 -
. ,. .: ,~ ......... . . . .... .
; . ., ,, .. ;, . . ....
1~S778
and the control input 40 of the voltage divider 38. The process
then continues as in the case of the electric 6timulator of
FIG. 5. At the outputs of the voltage divider 38, the adder
31 and the modulator 9 there are formed signals sho~m in ~IGS
13 k, l, n, respectively. As a result, during the period of
time (t1 - t2), when the muscles being stimulated are tired,
the amplitude of the converted stimulating signal, which acts
on these muscles and is produced at the output of the modula-
tor 9, decreases. ~he ~reater the fatigue of the muscles, the
greater the decrease in the amplitude. When the fatigue is over-
come, the amplitude of this signal returns to the original
value. - ~;
If the muscles being stimulated are not tired,there is
no electric signal at the control input 56 of the switch 57.
The signal from the output of the frequency meter 41 does not
p~8S via the switch 57 to the input 59 of th voltage divider
60~ Meanwhile, to the input 61 of the volta~e divider 60 there
is applied an electric signal corresponding to the excitation
threshold of the musclés being stimulated. Without a change
in its amplitude, this sig~al proceeds to the input 30 of the
adder ~1 and the input 40 of the voltage divider 38. Prior to
the moment of time t1 or ;~eginning with the moment of time t~,
at the outputs of the voltage divider 38, the adder 31 and the
modulator 9 there are formed signals shown in FIG~ 13 k, l, n,
respectively.
The operation of the stimulator of ~I&. 9 i8 similar to
that of the stimulator of FIG. 6. The diffe-ence between the
two embodiments is as follows.
., .
- 43 -
. ~ . . - . .
. . .. i . : ; . :
,. .. ..
: ~ . .. .
1~157~8
In each sti~ulation channel 1 (~IG. 1), the electric
signal from the output of the threshold element 33 (FIG.9) is
applied to the~input 6 of the comparator 7, the input~7 of the
unit 36 snd the input of the reference signal setting unit 62
which is a generator of pulses of a standard duration. At the
output of said reference signal forming unit 62 there is produ-
ced 8 square pulse of a constant amplitude, which is shown in
FIG. 14 a. ~he leading edge of this pulse coincides in time
with the appearance at the output of the integrator 5 of a pro-
gram signal in the form of the time-avera~ed bioelectric activi-
ty of the person who sets the program of movements. The dura-
tion ~ 4 of this pulse ~FIG. 14 a) is selected to be equal
to the maxi~um possible duration of the pulse formed at the
output of the comparator 7 (FIG. 9) and corresponding to the
maximum possible excitation threshold of the muscles being sti-
mulated.
The pulse is applied to the input 63 of the threshold
element 64, to those input 65 there is applied a pulse from
the output of the comparator 7. If the duration of the pulse
applied to the input 65 of the threshold element 64 is less
than the standard duration of the pulse applied to the input
63, there is no signal at the output of the threshol element
64 and, conse~uently, at the control input 66 of the switch
67. ~his indicates that the operating conaitions o~ the stimu-
lation channel 1 (~IG. 1) are normal. ~he switch 67 (FIG. 9)
is closed, and the converted stimulating signal is applied
from the output of the modulator 9 to the electrodes 19 connec-
_ 44 -
,. : . - .
1~ 15'^~78
ted to the muscles being stimulated.
If the duration ~ ~ of the pulse arriving from the output
of the comparator 7 is gre~ter than the stand~rd duration, as
is shown in FIG. 14 b, i.e. if ~3 > L4, this indicates that
the stimulation channel 1 (FIG. 1) is malfunctioning. At the
output of the threshold element 64 (~IG. 9) there is formed a
pulse of a constant amplitude, shown in ~IG. 14 c. ~he leading
edge of this pulse coincides with the trailin~ edge of the
pulse of a standard duration, shown in ~IG, 14 a. ~rom the
output of the threshold element 64, this pulse is applied to
the control lnput 66 of the switch 67. The switch 67 opens so
that the con~erted stimulating signal i8 not applied from the
output of the modulator 9 to the electrodes 19 connected to
the muscles bein~ stimulated, whereb~ these muscles are pro-
tected from p~inful electric sign~l6.
.
:: ~
,
_ 45 _ :
,
