EP1715823A1

EP1715823A1 - A method and apparatus for generating a control signal as a function of a respiratory act

Info

Publication number: EP1715823A1
Application number: EP05702472A
Authority: EP
Inventors: Giuseppe Andreoni; Marco Cattaneo
Original assignee: Politecnico di Milano
Current assignee: Politecnico di Milano
Priority date: 2004-02-17
Filing date: 2005-02-11
Publication date: 2006-11-02
Also published as: ITMI20040261A1; WO2005082294A1

Abstract

The present invention relates to an apparatus for generating a control signal for an electrical/electronic peripheral as a function of a respiratory flow of a subject (3) the operating principle of which is based on the acquisition of a signal produced by the subject (3) by means of the respiratory flow which can easily be modulated using the facial and nasal muscles. Modulation of the flow in terms of duration of the individual outward flows even within the same respiratory act may encode a series of commands such as letters or functions by using transducer means (2) which detect the temperature difference (ΔT) between the respiratory flow (Tint;Text) and a reference temperature (Tref).

Description

Holder: Politecnico di Milano DESCRIPTION "A method and apparatus for generating a control signal as a function of a respiratory act" The present invention relates to a method and an apparatus for generating a control signal as a function of a respiratory act and the invention relates particularly to, though without being limited to, an apparatus capable of being operated by means of light pulses of air, such as those which might be produced by the breath of a person, to generate a signal capable of controlling one or more peripherals of an electrical/electronic type, according to the preamble of claims 1 and 20. There are known apparatuses using electromechanical devices which, suitably connected to the mouth of a subject, allow the use of a peripheral, for example a computer keyboard, capable of simulating the striking/pressing of the keys constituting the keyboard. In fact, there are numerous situations in which it is impossible for a patient to use one or more limbs, perhaps as a result of trauma or from birth and a need has therefore been felt to produce apparatuses capable of providing assistance to these persons . One of these apparatuses is described in US patent 5422640, which discloses a device capable of aiding a handicapped person with limited or no use of the hands in using a personal computer. The device consists of mechanical parts which, when suitably connected to the mouth of the person with the handicap, make it possible to simulate typing on a keyboard by detecting the flow produced when the subject breathes out. This is achieved by means of a pressure transducer which detects the pulses of the flow generated by the subject when breathing out, interpreting them as consent to strike a key on the keyboard, once the mechanical parts have been positioned at the key which it is wished to press. The apparatus just described, therefore, requires combined operation between electrical devices and mechanical means, greatly limiting the usefulness of the equipment as a whole. Another example is illustrated in patent

JP10011220A2, which discloses a device consisting of a breath-operated switch based on measurement of the value of the pressure in a nozzle positioned in the mouth of a subject and of a monitor on which a cursor runs in a cycle between the alphanumeric characters present. The subject who wishes to select a character on the keyboard blows into the nozzle (which is provided with a switch) at the moment when the cursor is positioned on the character previously selected so as to pick out the character to be "typed". The switch therefore utilizes the increase in pressure which is created in the nozzle when the subject blows into it. The apparatus just described also suffers from numerous disadvantages among which, most evidently, is that of the slowness of the operation of generating a single keystroke/letter and consequently typing a word. It is clear that the state of the art offers only breath-operated switches based on pressure transducers equipped with simple binary switches . These transducers are therefore capable of interpreting only one logic state, that is the presence or absence of pressure or in other words, prior art includes only the encoding of binary code of the On/Off type. To overcome these drawbacks, software has been produced to enable a user to input words and phrases more easily by using the breath. The basic principle is that when the user begins to type in a text, the software automatically calls up the most probable complete word. This is possible because a database or virtual "vocabulary" is used from which the words can be retrieved. In addition to the transducer, it is therefore necessary to provide a database of words from which to extract the correct word automatically from among the hundreds of possible combinations supplied. Clearly, the system is not always infallible, since more than one word making complete sense may correspond to a specific combination. By means of these software aids, compiling an alphabetical text is certainly quicker, alleviating the major defect of the apparatuses described, that is their slowness in dictation, but in no case is it possible to manage a communication with a variety of inputs or alphanumeric texts to a personal computer (PC) or to any similar device. In view of the prior art described, the object of the present invention is to produce an apparatus and a method free from the defects listed above. According to the present invention, this object is achieved by means of an apparatus and a method for generating a control signal as a function of a breath exhaled by a subject, as claimed respectively in independent claims 1 and 20. By means of the present invention it is possible to produce an apparatus capable of producing proper independent encoding, capable of sending a variety of inputs, such as commands of the On/Off type and/or alphanumeric text . More particularly, the present invention is capable of encoding numbers, letters and special functions compared with a conventional switch having simple On/Off functions. Moreover, the present invention makes it possible to simulate a proper keyboard using respiratory modulation, the speed or rate of commands per minute of which is considerable and almost comparable with conventional devices . A further appreciable advantage to be considered is that the present invention is economical to produce . This is because it is easy to manufacture, miniaturize and wear, so that it can be used in any situation, such as for example at work, at home, in an office, on an aircraft, in a car, on a motorcycle etc.. A further point to be considered is that the present invention can be used in situations with high background noise. This is because it is possible to issue instructions or commands to one or more electrical/ electronic peripherals, even though they are operating in very noisy conditions, using only the outward flow of breath, thus avoiding the use of voice commands . Moreover, it can also be used in military and aeronautical applications. Finally, there is also the advantage of being able to operate a connection to remote devices such as for example personal computers, palmtops and mobile telephones, and this can be done equally well by cable (using serial, parallel or USB standards, or a generic communications standard) , on a USB port or by wireless means (RF, Bluetooth, GSM, GPRS, UMTS or Wi-Fi) . The characteristics and advantages of the present invention will become clear from the following detailed description of a practical form of embodiment, illustrated by way of non-limiting example with reference to the appended drawings, in which: -figure 1 shows a simplified block diagram of the apparatus according to the present invention; -figure 2 shows a pictorial representation of a form of embodiment according to the present invention; -figures 3 and 4 show time charts of signals, respectively of a modulated respiratory flow and a corresponding signal encoded according to the present invention. In the present context, the expression respiratory flow identifies the act by which a subject exhales air from the mouth and/or from the nasal septum and then inhales air, or vice versa. With reference to figure 1, it will be noted that the command signal acquisition and generation chain 1 of the apparatus according to the present invention comprises, for example: -a transducer 2 capable of converting the respiratory flow exhaled by a user 3 into an electrical signal 4; -an amplification module 5 capable of amplifying the electrical signal 4, said module 5 transmitting an amplified electrical signal 6; -an analogue/digital conversion module 7 for the amplified electrical signal 6, said module 7 being capable of transmitting a pulse train 8 for the entire duration of the breath 2; -processing means 9 capable of processing said pulse train 8, said means 9 transmitting a processed digital signal 10; -and control means 11 capable of controlling a peripheral (not shown in the drawings) as a function of the processed digital signal 10, said control means 11 transmitting a control signal 12. It should be pointed out that the elements cited above must be powered by a source of electrical energy, such as for example a battery (not shown in the drawings) . It is clear that, for the apparatus 1 disclosed by the invention to be wearable by the subject 3, the source of electrical energy must be chosen so as to meet a variety of requirements, such as for example autonomy, size, weight, safety etc.. In one form of embodiment, the apparatus 1 disclosed by the invention provides for elements 2-5- 7-9-11 to be discrete, that is assembled on a PCB. In another form of embodiment, the apparatus 1 disclosed by the invention provides for the means identified as the transducer 2 and amplifier 5 to be integrated in a single transducer device 13 and for all of this to be assembled using the SMD surface mounting technique. In another form of embodiment, the apparatus 1 disclosed by the invention provides for the means identified as a transducer 2, amplifier 5, analogue/digital converter 7 and processing means 9 to be integrated in a single control signal generator device 14 and for all of this to be assembled using the SMD surface mounting technique. In any of the forms of embodiment of the apparatus which is the subject of the present invention, it is the case, in particular, that the control means 11 are capable of controlling by means of the control signal 12 one or more peripherals, such as a personal computer (PC) , a mobile telephone, a wheelchair, a mouse or in any case an electrical/electronic device. The control means 11 may transmit by cable, or by a radiofrequency (RF) connection or an infrared (IR) connection or a connection using a standard such as Bluetooth, Wi-Fi, etc.. Whatever the type of connection used, provision is made for signal reception interface hardware and software, that is the driver for the peripheral, and both must be dedicated and developed to suit the apparatus 1 disclosed by the invention. The interface is capable of receiving as input the signal 12 generated by the control means 11 and of interfacing with the software already resident in the PC or similar device (PDA, telephone, mobile telephone, etc.). It should also be noted that the amplification means 5 may in turn comprise further stages, for example filtering stages capable of removing from the electrical signal 4 noise and/or signals not relevant for the purposes of identifying the control signal and/or sudden changes in temperature . These filtering elements may be configured according to the specific operating conditions and may also be configured by the subject by means of the hardware or software interface. The processing means are for example of the digital signal processing (DSP) type. With reference to figure 2, it can be seen how the transducer 2 can be linked to the subject 3, so as to intercept the respiratory flow of the subject, the same being the case for the transducer device 13 or the control signal generator device 14. This link may be achieved by direct connection to the subject 3 or by interposing support means, for example the side arms of spectacles (not shown in the drawings) . In particular, for it to be possible to intercept the respiratory flow exhaled by the subject 3, the link must in any case provide for the transducer 2 or the transducer device 13 or the control signal generator device 14 to be close to the mouth or the nasal septum. Alternatively, the transducer 2 or the transducer device 13 or the control signal generator device 14 may be fitted as a "piercing" in one of the nasal cavities so as to intercept the respiratory flow. It is clear that the more the transducer 2 or the transducer device 13 or the control signal generator device 14 is immersed in the respiratory flow, the greater the possibility of intercepting the respiratory flow. In fact, it is known that during the breathing out phase a flow of air is exhaled from the nose or mouth by the subject 3, while during the breathing in phase a certain flow is inhaled by the above- mentioned cavities. Generally, the air breathed out has a temperature T_int equal to that of the inside of the body, that is equal to approximately 36 °C, which is different, at most equal to the ambient temperature

T Because of the presence of the transducer 2, advantageously, it is possible to calculate the duration of the act of breathing out on the basis of the variations in temperature of the air between T_int or T_ext relative to a reference temperature T_ref. In other words it is possible to calculate a temperature difference ΔT between the internal temperature of the subject 3 and the reference temperature of the transducer 2. Advantageously, T_ref may coincide with T_ext. On this assumption, the apparatus 1 disclosed by the invention is of very simple construction, thus ensuring reduced production costs and lower energy consumption. As already mentioned previously, this is implemented by means of the transducer 2 which may for example be a temperature sensor based on a thermistor or thermal resistor, or a thermocouple, or a pyroelectric detector. The thermistor utilizes the property of semiconductors of varying their electrical conductivity with temperature and may for example have a positive temperature coefficient (PTC) or a negative temperature coefficient (NTC) . The variation in the resistance of an NTC resistor as a function of temperature, for example, may be expressed by the following equation: Rr = Ro * e^w/r-^1/ro) where R- is the resistance at temperature T, RQ is the resistance at the reference temperature T₀ and β is a constant which depends on the material used. The operating temperature range of such a thermistor is for example between -5°C and 70 °C. The choice of one of the two thermistors has to be made on the basis of the specific design requirements . In particular, if rapid response to temperature variations is required, that is the least thermal inertia possible, it is appropriate to choose a thermistor belonging to the class of NTC thermistors . Moreover, the thermistor which is the subject of the present invention, in addition to being miniaturized, is also encased in a resin material, so as to make it easier to link to the subject. The thermistor 2 is then immersed in the flow of air breathed in and out in such a way as to detect the temperature variations ΔT between the air breathed in and breathed out in the areas cited above and the reference temperature T_rβf or between the temperature of the air breathed out and the reference temperature when the latter coincides with the ambient temperature, producing an electrical signal proportional to the temperature in which it is immersed. Modulation of the outward flows in terms of duration, even in the same respiratory act, makes it possible to encode, through the temperature variations, a series of commands or functions. This is because, to each modulation of the respiratory flow there corresponds a temperature difference ΔT having a duration in time equal to the duration of the modulation performed by the subject 3. It should be noted that the term modulation in the present text denotes the ability of the subject 3 to exhale by contracting the respiratory and/or facial and/or nasal muscles a single short and/or long respiratory flow, or also a combination of short and/or long respiratory flows, which enable an alphabet to be simulated. By means of the present invention, therefore, it is possible to establish a correspondence between the respiratory act and an alphabet or a communication code. In particular, the respiratory act is modulated, for example, according to the rules of Morse code or another code already encoded or on the basis of a new communication code, that is a new alphabet to be encoded. In other words, the transducer 2 provides for the generation of the electrical signal 4 as a function of the temperature variation ΔT registered, a variation which arises between the air breathed in and out by the subject 3 and the reference temperature T_ref. By way of example, if it is wished to key in by video means a word encoded in Morse code by means of the apparatus 1 disclosed by the invention, it is first of all necessary, by one of the methods illustrated previously, to link the transducer 2 (or the transducer device 13 or the control signal generator device 14) to the subject 3 so as to intercept the flow breathed out. The word to be keyed in using Morse code is encoded according to the sequence " .. - .. - .. - .. " , as illustrated in figure 4. Assuming that short respiratory flows are associated with the dots and longer respiratory flows with the dashes, the subject 3 can encode the word in the example by modulation of the breath by contracting the facial muscles as appropriate and in an entirely natural manner so as to generate a signal such as that shown in figure 3. In other words, the subject 3 must modulate his own respiratory act according to the individual letters constituting the word as required by the code selected beforehand, Morse code in the present case. The times to be associated with the short or long breaths can be defined according to the abilities of the subject and by way of example a short breath is assumed to be less than 0.5 seconds while a long breath is more than 0.8 seconds . Thus figure 3 represents a possible modulation of the word and in particular, the axis of abscissas represents the time expressed in seconds, while the axis of ordinates represents the temperature expressed in °C. As can be seen, the respiratory flows vary between a temperature T_ext and a temperature Tj._nt. The thermistor 2 senses the temperature variations caused by the passage of the flow of air generating the electrical signal 4 proportional to said temperature variation ΔT. Once the transducer 2 has generated the electrical signal 4 and the amplifier 5 has amplified and filtered it as appropriate, the analogue/digital conversion module 7 generates the pulse train 8 having a square wave form, for example. This pulse train 8 is then processed by the processing means 9, that is the DSP, so as to generate a further digital signal 10 in which it is possible actually to identify which of the pulses of the pulse train 8 is actually an encoded letter. At this stage, depending on the type of connection chosen, there is a specific driver and specific hardware, easily implemented by a person skilled in the art, such that the dedicated software interface developed to suit the apparatus 1 disclosed by the invention is capable of receiving as input the signal 12 from the circuit 11. The signal 12 will contain in digital form depending on the implementation selected either the first letter of the word in question or the complete sequence of the letters constituting the word in question. In the first case, the letters following the first one are processed using the same method. The interface will merely have to convert the Morse signal into the digital signal and then into an analogue signal or into a digital signal only so as to control the video to display the desired word. In this way there is established a new method and a new apparatus for generating a signal capable of controlling any electrical/electronic peripheral merely by modulation of a respiratory act. It should be noted that, advantageously, the method disclosed by the invention of generating the control signal 12 is completely reversible. This is because, instead of modulating the flow breathed out by means of the respiratory and/or facial and/or nasal muscles it is also possible to modulate the flow breathed in, again by means of the respiratory and/or facial and/or nasal muscles. In this situation, the transducer 2 detects the thermal differences ΔT between the outside temperature T_ext and the reference temperature T_ref. Other possible applications of the present invention may for example be the possibility of controlling a wheelchair, or operating a mouse cursor on a video screen, or controlling other electrical/ electronic devices when the upper and/or lower limbs are already engaged in performing other tasks. For example, if it is wished to control a wheelchair, it is possible to modulate the respiratory flow according to a code identified by this alphabet given by way of example: move forwards -> short pulse t<0,5 sec; - move backwards -> long pulse t>l sec; move forwards+left -> short pulse followed by a long pulse; move forwards+right -> long pulse followed by short pulse; - move backwards+left -> short pulse followed by short pulse; move backwards+right -> long pulse followed by long pulse; rotate right -> three long pulses in succession; rotate left -> three short pulses in succession. Basically, for each movement desired by the subject, the respiratory act is modulated by means of the code just illustrated, in such a way that the transducer detects the temperature differences ΔT between the temperature Tι_nt and the temperature

■>-ref⁼J-ext • The control signal associated with said ΔT is then generated and in turn is sent to the wheelchair in accordance with any of the transmission techniques cited previously. Clearly, a person skilled in the art, for the purpose of meeting incidental and specific requirements, will be able to make numerous changes and produce numerous variants to the configurations described above, without thereby departing from the scope of the invention as defined in the following claims .

Claims

CLAIMS 1. An apparatus for generating a control signal as a function of a respiratory flow of a subject (3) , comprising: transducer means (2) coupled to said subject (3) so as to intercept said respiratory flow and capable of generating a first electrical signal (4) ; analogue/digital conversion means (7) capable of making said first electrical signal (4) digital so as to generate a second electrical signal (8) , and processing means (9) capable of processing said second electrical signal (8) to identify said control signal (12) , characterized in that said transducer means (2) detect the temperature difference (ΔT) between said respiratory flow (Ti_nt;T_eχt) and a reference temperature (T_ref) .

2. An apparatus according to claim 1, characterized in that said transducer means (2) detect the temperature difference (ΔT) between the temperature of said respiratory flow (Tι_nt) exhaled by said subject and said reference temperature (T_ref) .

3. An apparatus according to claim 1, characterized in that said transducer means (2) detect the temperature difference (ΔT) between the temperature of said respiratory flow (T_ext) entering said subject (3) and said reference temperature (T_ref) •

4. An apparatus according to claims 1 to 3, characterized in that said reference temperature

(T_re_f) coincides with said temperature of said respiratory flow (T_ext) entering said subject (3) .

5. An apparatus according to claims 1 to 4, characterized in that said control signal (12) is generated as a function of said temperature difference (ΔT) by means of modulation of said respiratory flow performed by said subject (3) .

6. An apparatus according to claims 1 to 5 , characterized in that said transducer means (2) are directly linked to said subject (3) .

7. An apparatus according to claims 1 to 5 , characterized in that said transducer means (2) are coupled to said subject by support means.

8. An apparatus according to claims 1 to 7, characterized in that said reference temperature

(T_ref) is the calibration temperature of said transducer means (2) .

9. An apparatus according to claims 1 to 8, characterized in that, during said respiratory flow, to generate said control signal (12) , modulation takes place using encoding as in Morse code.

10. An apparatus according to claims 1 to 9, characterized in that it also comprises amplification means (5) capable of receiving as an input said first electrical signal (4) and capable of generating a third amplified electrical signal (6) .

11. An apparatus according to claim 10, characterized in that said amplification means (5) comprise filtering devices capable of filtering said first electrical signal (4) so as to remove noise therefrom.

12. An apparatus according to claims 1 to 11, characterized in that said analogue/digital conversion means (7) receive as an input said third signal (6) and are capable of generating said second electrical signal (8) , the latter having the form of a pulse train.

13. An apparatus according to claims 1 to 12 , characterized in that it also comprises control means (11) capable of receiving said second electrical signal and capable of generating said control signal (12) so as to control said peripheral.

14. An apparatus, according to any one of the preceding claims, characterized in that said transducer means (2) are temperature sensors.

15. An apparatus according to any one of the preceding claims, characterized in that said transducer means (2) are any one of thermistors, thermal resistors, thermocouples or pyroelectric detectors .

16. An apparatus according to claim 15, characterized in that said thermistor is a positive temperature coefficient (PTC) thermistor.

17. An apparatus according to claim 15, characterized in that said thermistor is a negative temperature coefficient (NTC) thermistor.

18. An apparatus according to any one of the preceding claims, characterized in that the signal connection between said control means (11) and a peripheral is by means of any one of cable, radiofrequency, infrared, Bluetooth standard, Wi-Fi standard, GSM standard or UMTS standard.

19. An apparatus according to claim 18, characterized in that said peripheral is any one of a video, a PDA, a mobile telephone, a personal computer, a wheelchair or a mouse.

20. A method for generating a control signal for a peripheral as a function of the respiratory flow of a subject (3) , characterized in that it comprises a first step of converting said respiratory flow into a first electrical signal (4) by transducer means (2) as a function of the thermal variations (ΔT) present between the temperature of said respiratory flow (Tint;Text) and a reference temperature (T_ref) , a second step of analogue/digital conversion of said electrical signal (4) so as to generate a second electrical signal (8) and a third step of processing said second electrical signal (8) to generate a control signal (12) capable of operating said peripheral.

21. A method according to claim 20, characterized in that it also comprises the step of amplifying the first electrical signal (4) generated by said transducer means (2) so as to generate an amplified electrical signal (6) .

22. A method according to claim 20, characterized in that said amplification step also comprises a step of filtering said first electrical signal (4) .