CA1115778A - Bioelectrically controlled electric stimulator of human muscles - Google Patents

Abstract

ABSTRACT
A bioelectrically controlled electric stimulator of human muscles comprising an oscillator and a group of stimulator channels, each of the stimulator channels including a sensor for sensing the bioelectric activity of muscles of a programmer, a first integrator, a comparator, a modulator, a power amplifier, a unit for separating an electric signal, electrodes adapted to be connected to muscles of a person whose movement are under control, an amplifier of bioelectric activity of the person whose movements are under control and a second integrator con-nected to the output of the amplifier of bioelectric activity.
The electric stimulator improves the correspondence between a movement performed by a person and a programmed movement. During the course of electric stimulation, pain is reduced and the stimulation signal is automatically correctable with respect to the functional state of the muscles being stimulated.

Description

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 - ~

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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-.

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. . :, . ,; , ., : ~ , 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 .. . :, , : . , .. .:
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- ~.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 .

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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 . .

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'' ' , ~ , 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,~
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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, , . . . ~ .,, ~ ,. -. .,; ...................... . .
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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 ..... .

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.' 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 -.. , ~ , ~ - - . ;. . .. - .

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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 : : ' i~;J,;

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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-. ::

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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;
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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 -.;.; .

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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.

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,. - . .. 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 ' .. . ..

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~.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 , . . . , . ~ ... . .

.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.

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` -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 .. '' ~.
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: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 . ,., . , ~.

, . . . . .

.

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-;:

- , . ......
.. , , , - ~ , ., ;:.
. ~ ~ .. . . .. .
.... ..

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-. ~ ,. . .
- . : .

, . ~ .. .. .
:. . . .

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~
.

.

.. . .-- ~ .. . . ..
- : , , , . . :

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 ... ..

~ 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 ,. ., .. ` . . ` . , ` . , . ~ ..

~ 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.

. . , :.- - . ,- ~, ~ .

~ 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.

- ~ .

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 ~ .

''' 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 . ,. .: ,~ ......... . . . .... .
; . ., ,, .. ;, . . ....

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.

., .

. ~ . . - . .
. . .. 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.
.

:: ~

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,

Claims (8)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A bioelectrically controlled electric stimulator of human muscles, comprising: an oscillator of the carrier frequency of an electric signal which stimulates muscular activity of a person; a group of stimulation channels; each of said stimulation channels including; a sensor of bioelectric activity of muscles of a person who sets a program of movements; a first integrator connected with its input to the output of said sensor;
a comparator for comparing bioelectric activity of muscles of the person who sets the program of movements with that of a person whose movements are under control, having first and second inputs;
the first of said inputs of said comparator being electrically coupled to the output of said first integrator; a modulator hav-ing first and second inputs; said first input of said modulator being connected to the output of said oscillator; said second input of said modulator comprising a control input and being electrically coupled to the output of said first integrator through said comparator; a power amplifier electrically coupled with its input to the output of said modulator; a unit for separating the electric signal, which stimulates the activity of muscles of the person whose movements are under control, from the bioelectric activity of said muscles, caused by said signal, having first and second inputs and first and second outputs;
the first of said inputs of said separation unit being connected to the output of said power amplifier; electrodes adapted to be connected to muscles of the person, whose movements are under control, and also connected to the first of said outputs and the second of said inputs of said separation unit; an amplifier of bioelectric activity of muscles of the person whose movements are under control, connected with its input to said second output of said separation unit; a second integrator connected with its input to the output of said amplifier of bioelectric activity, the output of said second integrator being electrically coupled to said second input of said comparator.

2. An electric stimulator as claimed in claim 1, wherein each of said stimulation channels further comprises:
an adder having two inputs, the first being connected to the outputs of said comparator, while the second is connected to the output of said first integrator, the output of said adder being connected to said control input of said modulator.

3. An electric stimulator as claimed in claim 1, wherein each of said stimulation channels comprises: a first threshold element whose input is connected to the output of said first integrator, whereas the output of said first threshold element is connected to the first input of said comparator; a second threshold element whose input is connected to the output of said second integrator, whereas its output is connected to said second input of said comparator; a unit for forming the excitation threshold of muscles of the person whose movements are under control; a first input of said excitation threshold forming unit, connected to the output of said comparator; a second input of said excitation threshold forming unit, connected to the output of said first threshold element; an adder having two inputs, the first being electrically connected to the output of said excitation threshold forming unit, whereas the second input is electrically connected to the output of said first inte-grator, the output of said adder being connected to said control input of said modulator.

4. An electric stimulator as claimed in claim 3, wherein each of said stimulation channels comprises: a reference signal setting unit connected with its input to the output of said first threshold element; a third threshold element;

a first input of said third threshold element, connected to the output of said reference signal setting unit; a second input of said third threshold element, connected to the output of said comparator; an electronic switch having a control input connected to the output of said third threshold element, an input connected to the output of said modulator, and an output connected to the input of said power amplifier.

5. An electric stimulator as claimed in claim 3, wherein each of said stimulation channels comprises: a first voltage divider having two inputs, the first being connected to the output of said first integrator, whereas the second is electrically coupled to the output of said excitation threshold forming unit, the output of said first voltage divider being connected to said second input of said adder.

6. An electric stimulator as claimed in claim 5, wherein each of said stimulation channels comprises: a reference signal setting unit connected with its input to the output of said first threshold element; a third threshold element; a first input of said third threshold element, connected to the output of said reference signal setting unit; a second input of said third threshold element, connected to the output of said comparator; an electronic switch having a control input connected to the output of said third threshold element, an input connected to the output of said modulator, and an output connected to the input of said power amplifier.

7. An electric stimulator as claimed in claim 5, wherein each of said stimulation channels comprises: a frequency meter connected with its input to the output of said bioelectric activity amplifier; a first amplifier connected with its input to the output of said frequency meter; a second differentiator amplifier connected with its input to the output of said second integrator; a multiplier; a first input of said multiplier, connected to the output of said first differentiator amplifier;a second input of said multiplier, connected to the output of said second differentiator amplifier;
a first electronic switch; an input of said first electronic switch, connected to the output of said frequency meter; a control input of said electronic switch, connected to the output of said multiplier; a second voltage divider having two inputs, the first being connected to the output of said first electronic switch, whereas the second is connected to the output of said excitation threshold forming unit, the output of said second voltage divider being connected to said first input of said adder.

8. An electric stimulator as claimed in claim 7, wherein each of said stimulation channels comprises: a reference signal setting unit connected with its input to the output of said first threshold element; a third threshold element; a first input of said third threshold element, connected to the output of said reference signal setting unit; a second input of said third threshold element, connected to the output of said comparator; a second electronic switch having a control input connected to the output of said third threshold element, an input connected to the output of said modulator, and an output connected to the input of said power amplifier.