RU2053746C1 - Method for acoustically representing spatial information to be useable by vision invalid people - Google Patents

Abstract

FIELD: medicine. SUBSTANCE: method involves using complex probing signal. Adjusted filtration response is close in this case to pulse- response characteristic of the scattering object. To bring the frequency and time signal ranges in correspondence with audio-analyzer, transformation is carried out in each channel to extend in time the adjusted filtration response. The set of signals being percepted by a vision invalid person, the state of the surrounding situation becomes observable acoustically. EFFECT: enhanced effectiveness in helping blind and invalid persons. 2 dwg, 1 tbl

Description

 The invention relates to the creation of orientation devices for the blind in the environment.

 Known technical systems and devices designed for the visually impaired, allowing them to navigate in the environment: a device for orienting people with impaired vision; intended for the blind converter of the visual signal into sound; system for showing the way to the blind; a guide for the blind with the translation of visual data into tactile and auditory sensations; a device for assessing the capabilities of the apparatus for assisting the blind in walking.

 An ultrasound signal is emitted from the device for assisting the blind while walking. Reception is carried out on five ultrasonic receivers and a phase detector. If the phase difference lies 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.

 Measuring the distance to the object, as a rule, comes down to estimating the delay time of the ex-signal. An example of such decisions is a method and apparatus for assisting in orienting the blind and people with low vision. The device is designed as a device for measuring distances by determining the transit time of an ultrasonic ex-pulse. Distance data is converted to acoustically perceived sound of a certain frequency.

 Part of the device is a stationary system, for example, a device for guiding the blind in the city. It allows the blind and visually impaired to move along a specific route without the help of a guide. It 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. 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. In the description [9], an indicator of the path running on infrared radiation is presented. In order to increase the safety of movement, blocks were introduced into the device that allow the device to respond not only to changes in the surface level, but also its composition. Since the reflection from different surfaces of infrared radiation is not the same, a person can detect obstacles, such as borders.

The following devices can serve as an example of industrial designs of this type:
Sonic Pathfinder was developed by TONY HEYES from the Mobility Center in Nottenham (UK) in 1987. Ultrasonic radiation. Acoustic perception. The microprocessor built into the device analyzes the information and “decides” which and at what moment will be cleared for the user, selects its elements that are essential 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. The signal is given 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.

 Vybraduks. Produced in Germany by the company Frits Huttingel Elektronic. The device is based on an ultrasonic radar with pulses of a frequency of 40 kHz. The dimensions of the device are 19-5-9 cm, weight 190 g. The range of measured distances to obstacles is 0.9-9 m. Power is enough for 15 hours.

 The second direction involves the use of hearing to the maximum extent possible for perception of the environment. Devices allow to localize the object, to obtain information about the direction and distance. In devices of this type, it is possible to locate several objects at the same time, and the sound signal carries some information about the nature of the object. To ensure a wide field of view, binaural perception is used. Such devices include a means of orientation for the blind. The device comprises an emitter sending a measuring beam, reflected by an obstacle, supplied to the receiver and converted into acoustic signals. The emitter and receiver are placed in a device worn on the body of a blind person. The measuring beam is infrared radiation, which is sent in the form of a thin beam to a localized object. After the object is localized, the object contours are scanned with an IR beam. The reflected beam is converted by the receiver into acoustic signals.

 An example of an operating device is Siemens spectacles (Hanelt. BRO). Developer company SYMNENS (engineer Kolani). Ultrasonic radiation is produced by two transducers. Vinaural reception. The emitter and receiver are located in a spectacle frame. The weight of all the electronics is 200 g. The remoteness of an object (2.1-8.4 m) is determined by the pitch (the closer, the higher), and the direction according to 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 the perception of frontal images of the environment using tactile stimulators on the body or even electrodes implanted in the brain. An example is Laser Cane (Nurion. USA). Infrared radiation (3 emitters). Acoustic perception through headphones and simultaneously through vibrators under the index finger. In contrast to the majority of electronic orienteering devices, the use of three pairs of emitter-receivers is envisaged 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 it does not occur when an object appears in the reflection field, but rather, if it does not exist. These elements of the apparatus serve to respond to lowering the surface in front of the legs and report steps down, holes, the edge of the platform and other dangers of this kind. Laser typhoid scans have been developed in the USA since the mid-60s and are now 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 device (Worshald. New Zeland), developed by Leslie KAY, dean of the Faculty of Electrical Engineering at the University of Kanterbury (New Zealand).

 The principle of operation of the device is as follows. 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. Food is enough for 5 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 indicator of an obstacle, 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 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.

 Figure 1 shows the structural diagram of the device.

 The essence of the method of presenting acoustic information, the basis of the considered device is as follows. And the medium emits an ultrasonic signal with a linear FM, with a frequency range of about an octave.

 Binaural ex-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. 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 emit from animals continuously, but in the form of discrete pulses, each of which lasts 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 ex-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 and the harmonic high-frequency oscillation.

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

μτ где Φ фаза сигнала, сигнал биения несет информацию главным образом о дистанции D до объекта, поскольку τ 2D/c.In the considered method, the ex-signal S (t) and the reference LFM signal So (t) are multiplied. Generated as a result of low-pass filtering heartbeat fluctuation frequency is _{(1/3) · cos (ω o} τ + μtτ + μ + τ ^2/2), where τ ex-delay signal. Since the instantaneous frequency of the signal is determined
f (t)

μτ where Φ is the phase of the signal, the beat signal carries information mainly about the distance D to the object, since τ 2D / c.

 Thus, the signal obtained by the considered method carries information mainly about the distance to the object. Reception of ex-signals reflected from several objects or brilliant points of one object allows the user to get some information about the nature of the environment. However, a direct analysis of the impulse response of the scattering object, information about which is contained in the ex-signal, is not performed in the specified method.

 The aim of the invention is the coordination of the frequency range and duration of the acoustic signal with the auditory analyzer and obtaining more complete information contained in the ex-signal.

This is achieved by the fact that in the method of acoustic representation of spatial information, which consists in the emission of ultrasound. The LFM signal, binaural reception of echo signals to two ultrasonic microphones, amplification, conversion of electrical signals into acoustic ones and subsequent perception of signals by a human auditory analyzer, introduce operations of coordinated filtering of ex-signals in each channel and temporal stretching of the filter responses in the right and left channels in α times, where α f ₁ / f ₂ , f _{1 is the} carrier frequency of the probe signal, f _{2 is the} average frequency of the range perceived by the human auditory analyzer.

 The essence of the proposed method is as follows. An ultrasonic chirped pulse is emitted. Note that any complex or noise-like signal can be used as a probing signal, for which the condition TW> 1 is satisfied, where T is the signal duration, W is its band. However, studies of animals, such as bats, show that animals use FM signals with a large (up to 100 kHz) frequency deviation, within its duration, which is units of ms. In addition, compression filters for chirp signals are well developed, so the proposed method is considered in relation to chirp signals.

 The input signal X (x, t), taking into account the spatial coordinate x, is a convolution of the probe pulse S (x, t) with the impulse response of the scattering object h (x, t).

X (x, t) S (x, t) h (x, t) (1)
With consistent filtering of the input process, the response will look like
X (x, t) S (x, -t) S (x, t) h (x, t) S (x, -t) (2)
It is known that the correlation function of the chirp signal form A _{· cos (ω o t + μ} t ^2/2) can be written
R (τ) = (1/2) A $\genfrac{}{}{0ex}{}{\text{2}}{\text{o}}$ T · [sin (πmx
x (1-τ / T) τ / T] · cos (ω _o τ) / πmτ / T (3) where m 2 Δ fT
Δ f frequency deviation
(1/2) A $\genfrac{}{}{0ex}{}{\text{2}}{\text{o}}$ T is the total energy of the considered radio pulse.

 For n >> 1, which is true, for example, for a signal with a frequency deviation of 40 kHz and a duration of 1 ms, the correlation function forms a very sharp peak and, therefore, the convolution S (x, t) x S (x, -t) is close to δ -functions, i.e.

S (x, t). S (x, -t) ≈δ (x, t) (4)
Taking into account (4), the response of the matched filter is
x (x, t) ≈ h (x, t) x δ (x, t) ≈ h (x, t) (5)
In other words, the response of the matched filter is close to the impulse response of the scattering object.

In order for the HF signal to be perceived by the HSA, it is necessary to temporarily stretch it according to the law
X (x, t) _ → X (x / α, t / α) (6) taking into account (5) h (x, t) _ → h (x / α, t / α) where α f ₁ / f ₂
f ₁ carrier frequency of the probe signal,
f _{2 the} average frequency of the range perceived by human auditory analyzers.

 Suppose that probing pulses with a carrier frequency of 80 kHz are used, and the average frequency of the audible range is 1.2 kHz. In this case, α≈ 66. If a signal of duration T is reflected from an object with a length in space L, the duration of the SF response Tsf can be estimated as 2L / c. For example, at L 0.5 m, Tsf ≈ 2L / c ≈ 3 ms. After temporary stretching, the duration of the signal arriving at the HSA will be Tsf ≈ 200 ms. Such an increase in duration is important in perception, since signals with a duration of less than 0.2 s are hardly recognized.

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

 The device contains: 1 probe pulse generator; 2 cascade of FM; 3 radiation path amplifier; 4 transmitter; 5, 6 ultrasonic transducers; 7.8 analog-to-digital converters (ADC); 9.10 matched filters (OF); 11, 12 memory blocks; 13.14 digital-to-analog converters (DAC); 15, 16 amplifiers; 17, 18 head phones; 19 generator of synchronizing pulses (GSI); 20 microprocessor.

 The type of ADC 7, 8 is selected based on the required speed, determined by the frequency of the probe pulses. Since the maximum frequency used in such systems is 120 kHz, the necessary speed provides the K1108PV1 ADC with a conversion time of less than 0.9 μs and a clock frequency in the range of 0.4-1.5 MHz.

 SF 9, 10 (compression filters) for chirp signals are well known in radio engineering.

The capacity of the memory blocks (BP) 11, 12 should provide recording reports of the input implementation. The number of samples is determined
N f _d T _p , T _p 2D / c, where T _{p the} duration of the implementation
D range of the device
f _d sampling rate
The memory is used in digital technology. K DAC 13, 14 does not have special performance requirements, since the frequency of reading information from memory blocks is much lower than the recording frequency. DAC K572PTA1 can be used. 10V with a conversion time of 5 μs, a consumption current of 2 mA, a supply voltage of 10 V.

 As the processor 20 can be applied single-chip computer K1816.

 After the radiation, the input implementation goes to the ADC 7, 8 and then to the digital SF 9, 10. The SF responses corresponding to their scattering object are recorded in the memory blocks 11, 12. The processor 20 provides for reading information α times slower than the recording and zeroing the VP after each processing cycle. The received signals are converted into analog form using the DAC 13. 14 and after amplification are fed to the headphones 17, 18.

Application of new operations compared to the prototype for each processing channel:
consistent filtering
temporary stretching of the responses of matched filtering made it possible to obtain a positive effect in matching the frequency range and duration of the acoustic signal with an auditory analyzer.

Claims (1)

 METHOD OF ACOUSTIC REPRESENTATION OF SPATIAL INFORMATION FOR VISUAL DISABLED PEOPLE, which consists in emitting an ultrasonic frequency-modulated pulse, binaural reception of an echo signal to two ultrasonic microphones, amplification, conversion of electrical signals into acoustic ones, followed by the perception of signals by a human auditory analyzer, characterized in that echo filtering and temporal stretching of the received responses in each receive channel.

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