RU2085162C1 - Method of acoustic delivery of spatial information for sight invalids - Google Patents

Abstract

FIELD: information for sight invalids. SUBSTANCE: invention relates to devices for spatial orientation of blinds. Method consists in emitting ultrasonic pulse, binaural reception of echo-signal by two ultrasonic microphones, amplification, transformation in each reception canal, and subsequent perception of signals with human acoustic analyzer. According to invention, echo- signal is transformed by way of its time extension. EFFECT: achieved conformance of frequency band and duration of acoustic signal with acoustic analyzer. 2 dwg, 1 tbl

Description

 The invention relates to the field of creating devices for orienting the blind in the environment.

 Known technical systems and devices designed for the visually impaired and allowing them to navigate in the environment.

Known [Auth. St. N 1445725 (USSR), Device for orienting people with impaired vision; application N 0235460 (Germany), Designed for the blind converter of the visual signal into an audio one; application N 013616186 (Germany), a system for indicating the path of the blind; application N 2598316 (France), Guide for the blind with the translation of visual data into tactile and auditory sensations; application N 63-11987 (Japan), A device for assessing the capabilities of the apparatus for assisting the blind in walking]
In the device for assisting the blind while walking (application N 56-5653 (Japan)), an ultrasonic signal is studied. Reception is carried out on five ultrasonic receivers and on the phase detector. If the phase difference is within a given region, it is determined that the obstacle is within the boundaries of a solid angle corresponding to the specified known phase shift.

 Measurement of the distance to the object, as a rule, comes down to estimating the time delay of the echo signal. An example of such technical solutions is the apparatus and method of assisting in orienting the blind and people with low vision (application N 08 3544047 (Germany)).

 The device is designed as a device for measuring distances by determining the transit time of an ultrasonic echo pulse. Distance data is converted to acoustically perceived sound of a certain frequency.

 Some of the devices are stationary systems, for example, a device for leading the blind in the city (application N 2593060 (France)). It allows blind and visually impaired people to move along a certain route without the help of a conductor and consists of a cable or fiber laid in the ground and transmitting a modulated sound signal received by the detector in canes and transmitted to the receiver to signal any danger.

 Currently, there are three areas of development of technical systems for visualizing the surrounding space to help the blind.

 The first direction includes indicators of the free path. They are the simplest and carry information only about the presence of an obstacle in the path of the blind. The devices use a narrow beam of acoustic energy and can take the form of a flashlight. Presentation of information is made in a sound or tactile form.

 An example of such devices are as follows. Mower sensor. Worshald. New Zealand invention of the New Zealander Geoff Mowat. Ultrasonic radiation is used.

 The vibration of the device is perceived, which increases with approach to the subject. The device is a box carried in the hand measuring 15 x 5 x 3 cm and weighing 185 g. It is used only as an obstacle detector. You can set one of two values of the maximum distance at which the object will be seen as a possible obstacle, and the vibrator will start to work 1 and 4 m. Depending on the situation, the user can simply turn the device by turning the width or height of the radiation; in the first case, a lot of information about side objects comes in, in the second, the head of a blind person is well protected from the danger of collision with impending obstacles such as a truck body, a strongly tilted traffic light pole, etc.

 Scoutmaster is manufactured in Austria by the West German company AKG.

 Ultrasonic radiation, vibration perception. Fastens like a tie on the chest with the arrival of vibration on the shoulder, so that both hands are free. Informs about the presence of obstacles within the user-specified distance limits. Unlike the Sicopilot, the limit distance is not limited to two values, but can be adjusted very widely. In addition, the device has a large vertical angle of radiation, which allows you to timely indicate the presence of an object, which may hit your head. Food provides 15 hours of continuous use, Sicopilot.

 Habelt Electronic BRD is manufactured by Siemens (Germany).

 Perception of vibration. The oscillation frequency changes. The device has the shape of a flashlight measuring 14 x 6 x 4 cm and weighing 200 g. It is placed in the hand or attached to the chest. It reports that an obstacle has appeared within the range set by the user (you can choose one of two values of the maximum range of 1.5 and 2.5 m). By the height of the sound, determine what distance to the object, if it is less than the limit.

 Carrying a "flashlight" in his hand, the blind person gets the opportunity to clarify the direction of the obstacle, and sometimes the shape and size of the object. The width of the field at a distance of two meters is about 50 cm.

 Sonie Pathfinder was developed by Tony Heyes from the Mobility Center in Nottingham (UK) in 1987. Ultrasonic radiation. Acoustic perception. The microprocessor built into the device analyzes the information and decides which and at what point will be useful to the user, selects its elements that are significant in determining the degree of danger. Most of the time, the device is "silent", making it possible to actively use hearing for orientation and not loading the brain with unnecessary information. Sounds two seconds before a potential collision with an obstacle. In this case, the microprocessor also takes into account the speed of the blind. Mounted on the head so that the hands are free.

 Vibraduks is manufactured in Germany by Fritz Huttinger Electronic. The device is based on an ultrasonic radar with pulses of a frequency of 40 kHz. The vibration perception of boxes measuring 19x5x9 cm and weighing 190 g. Information on the distance to the obstacle in the range of 0.9-9 m. Power lasts for 15 hours.

 The second direction involves the use of hearing to the maximum extent possible for perception of the environment. The device allows you to localize the object, to obtain information about the left, right or top directions to the object, as well as the distance to it. In a device of this type, it is possible to locate several objects at the same time, and an audio signal carries some information about the nature of the object. To ensure a wide field of view, binaural perception is used.

 An example of a device of this type is Siemens spectacles (Habelt. BRD). Developer company SIEMENS (engineer Kolani).

 Ultrasonic radiation is produced by two transducers. Binaural reception. The emitter and receiver are located in a spectacle frame. The weight of the entire electronics is 200 g. The remoteness of the object (2.1 3.4 m) is determined by the height of the current (the closer, the higher) in the direction of the stereo effect. At a distance of 2 m, the field width is 80 cm.

 The third direction is characterized by an attempt to model vision with perception of frontal environmental images using a set of tactile stimulators on the body or even a set of electrodes implanted into the brain, as suggested by Brindley Dobelle. Information is transmitted through a miniature block on integrated circuits. An example is a Laser Cane device (Nurion.USA).

 Infrared radiation (3 emitters). Acoustic perception through headphones and simultaneously through vibrators under the index finger. Unlike most electronic orientation devices, it is envisaged to use three pairs of emitter-receivers at once. They are located in different parts of the reed in height and “observe” the corresponding groups of objects: the upper ones protect the head, the middle ones inform about standard obstacles, and the lower pair of emitter-receiver has a feature. The sound tone determined by them arises not when an object appears in the reflection field, but, on the contrary, when it is absent. These elements of the apparatus are set up to respond to lowering in front of the legs and report steps down, pits, the edge of the platform and other dangers of this kind. Laser tiflotype has been developed in the USA since the mid-60s. Now such canes are widely used. Restrictions are imposed by prices reaching several thousand dollars.

 Closest to the technical nature of the present invention is a method of representing spatial information, implemented in the Sonic guide (Worshald.New Zeland), developed by Leslie Kay, Dean of the Department of Electrical Engineering at Kanferbary University (New Zealand).

 When the device is used, an ultrasonic emitter is used. Stereophonic perception on two earphones. Multi-element sound display. The emitter and two receivers are designed in spectacle frames. Electronics and battery power are in a box that you can put in your pocket. There is enough food for five hours.

 The device provides information about the distance to the object (the farther it is, the higher the sound), as well as, within certain limits, about its shape, size and texture. Thus, the device is no longer a simple obstacle indicator, but to a certain extent an environmental analyzer with many important characteristics. However, the richer the information is issued, the greater the load on the user. It is necessary to process a rather complex sound picture involving variables such as volume, pitch, timbre characteristics.

 Successful interpretation of the messages generated by the device requires a long learning process. Courses on the development of the apparatus in Germany last about a month. Price over 3,000 dollars.

 The main technical characteristics of the device are given in the table.

 The block diagram of the device is shown in FIG. one.

 The essence of the method of presenting acoustic information, the basis of the considered device is as follows. An ultrasonic signal with a linear FM is emitted on Wednesday, with a frequency range of about an octave. The parameters of the device are given in the table.

 Binaural echo signals are received at two ultrasonic receivers. The received signals are multiplied with a reference signal to obtain a beat signal. Carry out low-pass filtering of the process. Produce frequency filtering of signals using the attenuation equalizer. After amplification, the signals are sent to the head phones for perception by the human auditory system. The distance to the object is represented by the frequency of the audible signal, and the direction to the object is the interaural difference in the amplitudes of the signals falling on both ears. The disadvantage of the considered method is as follows. The radiation frequency of the probe signal is in the range of 40-120 kHz. The lower limit of the range is determined by the required resolution. Studies of animals, such as bats, also show that their radiation range is 30-70 kHz, and the area of greatest intensity is 40-50 kHz. Sound does not come from animals continuously, but in the form of discrete pulses, the duration of each of which is 1-5 mS.

At the same time, the area of the best audibility of the human ear lies in the range of 250-4000 Hz. Therefore, to supply echo signals to the human auditory analyzer HAS, their frequency should be significantly reduced. To reduce the frequency, an actual demodulation (detection) operation is performed, which consists in multiplying the original signal S (t) and the harmonic high-frequency oscillation cosω _o t where ω _{o is the} carrier frequency.

 However, the power spectral density obtained as a result of this operation is, in the general case, a distorted copy of the signal spectrum.

In the considered method, the echo signal S (t) and the reference LFM signal S ₀ (t) are multiplied.

где τ задержка эхо-сигнала.Wherein

where τ is the echo delay.

Первое слагаемое представляет собой колебание биения частот 1/2•cos(ω_oτ+mtτ+μτ²/2), выделяемое в результате низкочастотной фильтрации. Поскольку мгновенная частота сигнала определяется f(t) = 1/2πdΦ/dt = μτ где v фаза сигнала, низкочастотный сигнал биения несет информацию о задержке t, определяемую дистанцией до объекта D, поскольку t 20/с. Таким образом, сигнал получаемый в результате реализации рассмотренного способа несет информацию главным образом о дистанции до объекта. Прием эхо-сигналов, отраженных от нескольких объектов или блестящих точек одного объекта, позволяет пользователю получить некоторую информацию о характере окружающей обстановки. Но и в этом случае картина воспринимается, как совокупность оцененных дальностей и направлений.As a result of multiplication, we obtain

The first term is a heartbeat fluctuation frequency 1/2 _{• cos (ω o τ + mtτ} + μτ ^2/2) generated as a result of low pass filtering. Since the instantaneous frequency of the signal is determined by f (t) = 1 / 2πdΦ / dt = μτ where v is the phase of the signal, the low-frequency beat signal carries information about the delay t, determined by the distance to the object D, since t 20 / s. Thus, the signal obtained as a result of the implementation of the considered method carries information mainly on the distance to the object. Reception of echoes reflected from several objects or brilliant points of one object allows the user to get some information about the nature of the environment. But even in this case, the picture is perceived as a set of estimated ranges and directions.

 At the same time, it is known that the spectral composition of the echo signal depends on the shape and size of the object and can be used as a sign in solving the recognition problem. The human ear is a very advanced frequency analyzer that allows you to evaluate the spectral composition of the echo signal.

 However, the signal obtained in the prototype method, as noted, is distorted and does not allow you to use all the capabilities of SAS. Another difficulty in perceiving an echo is related to its duration. The perception threshold rises with decreasing pulse duration, that is, short pulses are perceived with greater difficulty than long ones.

 The aim of the proposed invention is to coordinate the frequency range and duration of the signal with the auditory analyzer and to obtain more complete information contained in the echo signal.

This goal is achieved by the fact that in the method of acoustic representation of spatial information, which consists in the emission of a high-frequency signal, binaural reception of echo signals to two ultrasonic microphones, amplification, processing in each channel of reception and subsequent perception of signals by a human auditory analyzer, the operation of temporary stretching an echo signals in the right and left channels a times a = f ₁ / f ₂ f _{1 the} carrier frequency of the probe signal, f _{2 the} average frequency of the range perceived by the auditory analyzer.

 The essence of the proposed method is as follows.

(1)
С другой стороны входной сигнал представляет собой свертку зондирующего импульса S(t) с ИХ объекта локации h(t)
X(t) S(t)•h(t)(2)
Подставляя (2) в (1) и, переходя в область спектра, получим

где

передаточная функция восстанавливающего фильтра;

спектр оценки эхо-сигнала;

спектр излученного сигнала;

- передаточная функция объекта,
откуда

Выражение (5) показывает, что слуховая система человека, анализируя спектр оценки эхо-сигнала, производит и оценку передаточной функции объекта локации, определяющей его ИХ. Если излучается очень короткий (ультракороткий) ВЧ импульс, близкий к δ-функции, входной сигнал по сути представляет собой ИХ рассеивающего объекта. С учетом пространственной координаты.A short high-frequency pulse is emitted. An estimate of the received signal can be represented as a convolution of the input signal and the impulse response (ИХ) of the receiver, which performs the restoration of the signal h _in (t)

(one)
On the other hand, the input signal is a convolution of the probe pulse S (t) from the object of their location h (t)
X (t) S (t) • h (t) (2)
Substituting (2) into (1) and passing into the spectral region, we obtain

Where

transfer function of the recovery filter;

echo evaluation spectrum;

spectrum of the emitted signal;

- transfer function of the object,
where from

Expression (5) shows that the human auditory system, analyzing the spectrum of the evaluation of the echo signal, also evaluates the transfer function of the location object, which determines their IC. If a very short (ultrashort) HF pulse is emitted, which is close to the δ-function, the input signal is essentially an IC of a scattering object. Given the spatial coordinate.

где

пространственная координата.

Where

spatial coordinate.

где

волновой вектор.Wherein

Where

wave vector.

 Thus, the evaluation of the received signal is the IC of the scattering object, accurate to the IC of the recovery filter, the effect of which is individual for each auditory analyzer and can be taken into account during training.

где α = f₁/f_2/ ;
f₁- несущая частота сигнала;
f₂ средняя частота диапазона, воспринимаемого САЧ.In order for a short RF signal (6) to be perceived by a human auditory analyzer, (SAC) temporarily stretches the signal α times according to the law

where α = f ₁ / f _{2 /} ;
f ₁ - carrier frequency of the signal;
f _{2 is the} average frequency of the range perceived by HSA.

Среднюю частоту диапазона наилучшей слышимости необходимо подбирать для среднего пользователя и она несколько превышает 1 кГц.Taking into account (6), the scale of their object will accordingly change

The average frequency of the range of the best audibility must be selected for the average user and it slightly exceeds 1 kHz.

 Suppose a probing signal with a carrier frequency of 60 kHz is used, and the average frequency of the audible range is 1.2 kHz. In this case, α will be 50.

To fulfill relation (6), the condition
t _and ≈ 1 / f ₁
where τ _{and the} duration of the probe pulse.

Suppose τ _and = 20 μs. If the signal is reflected from an object having a length in space L, the reflected signal X (t) will experience a stretching in time to the value
τ _e = τ _and + 2L / C
where c is the oscillation propagation velocity.

Suppose L = 0.4 m. In this case, the duration of the echo signal will be τ _e ≈ 2.44 ms. After its temporary extension by a factor of α, the duration is at _э ≈122 ms. Such temporary stretching is also important for signal perception by the auditory analyzer.

 After amplification, the signals of the left and right channels are fed to the head phones for the perception of HAS.

 An example of a device that implements processing in accordance with the proposed method is shown in figure 2.

The device contains:
Probe Pulse Generator 1
Radiation path amplifier 2
Transmitter 3
Ultrasonic Transducers 4.5
Analog to Digital Converters (ADCs) 6.7
8.9 memory blocks
Digital to Analog Converters (DACs) 10.11
Amplifiers 12.13
Clock Generator (GSI) 14
CPU 15
The type of ADC 6, 7 is selected based on the required speed determined by the frequency of the probing signals. Since the maximum frequency used in such systems is 120 kHz, the necessary speed provides the ADC K 1108 PV1 with a conversion time of less than 0.9 μs and a clock frequency of 0.4 to 1.5 MHz.

The capacity of the memory blocks 8, 9 is determined by the frequency and duration of the processed implementation T _p . The storage device (memory) should provide short-term storage of N samples, where
N f ₁ T _p T _{p p} 2D / c
D maximum range.

At D 15 m, f ₁ 40 kHz N≈ 4000 devices.

 Memory devices are widely distributed in digital technology.

 DAC 10, 11 does not have special performance requirements, since the frequency of reading information from memory blocks is lower than the recording frequency.

 DAC K 572 1.10V can be used with a conversion time of 5 μs, a consumption current of 2 mA, and a supply voltage of 10 V.

 GSI 14 generates pulses with a repetition rate of sounding signals that synchronize the operation of the entire device.

 As the processor 15 can be used single-chip computer K 1816.

 After the radiation, the input implementation arrives at the ADC 6, 7 and is entered into the VP 8, 9. Process 15 provides for reading information α times slower than recording and zeroing the BP after each cycle radiation reception.

 After converting the signals into digital form using the DAC 10, 11 and subsequent amplification, they enter the SAC.

The use of new operations compared to the prototype:
ultrashort pulse radiation;
temporary stretching of the echo signals in the right and left channels allowed to obtain a positive effect to coordinate the duration and frequency range of the input signal with the auditory analyzer.

Claims (1)

 The method of acoustic presentation of spatial information for the visually impaired, which consists in emitting an ultrasonic pulse, binaural receiving an echo signal to two ultrasonic microphones, amplifying, processing in each receiving channel and subsequent perception of signals by a human auditory analyzer, characterized in that the signal is processed by temporary stretching.

Images