JP2002296024A - Step detector and activity aiding device for visually handicapped person - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a step detector capable of detecting whether a step exists or not and its depth by making it possible to recognize a nearby object by increasing the SN ratio of a reflected wave from the object to reverberations within a sensor, and to provide an activity aiding device for visually handicapped person capable of determining whether a step exists or not and its depth by incorporating the same step detector into a walking stick. SOLUTION: This step detector is made by providing a waveguide tube 3 in front of an ultrasonic sensor 2, forming an outlet 4 of the tube 3 into a slanted shape, and adjusting the length of the tube 3 so that a reflected wave from the tube outlet and reverberations within the sensor counteract each other. This activity aiding device for visually handicapped person is made by providing the same step detector near a tip end of the walking stick 1 for sensing whether a barrier exists or not.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step detector using an ultrasonic sensor, and a step detecting device for identifying a step by incorporating the step detector into an activity assisting device called a cane for assisting the activity of a visually impaired person. The present invention relates to an activity assisting device for the visually impaired that can be used.

[0002]

2. Description of the Related Art An ordinary wand as a device for assisting a visually impaired person is a stick having a certain length, which is operated by hand by a visually impaired person, and the tip of the wand hits an obstacle. Thus, the presence or absence of an obstacle is sensed. Therefore, according to such an activity assisting device, it is substantially difficult to detect the presence or absence of a step whose front is lowered and the degree of its depth.

[0003] Therefore, there has been proposed an instrument which can notify a step and its depth by applying a measurement technique using a sensor such as an infrared ray or an ultrasonic wave. However, the signals measured by these sensors tend to change depending on the distance to the reflector, the surface condition, and even the orientation. There was a problem that a stable measurement could not be obtained, because a signal of high strength could not be obtained.

There are two types of ultrasonic sensors: an open type in which the ultrasonic vibrator contacts the outside air through an opening, and a drip-proof type without an opening. The drip-proof type is easy to handle and has durability. On the other hand, since the sensitivity is low, it is difficult to stabilize the operation. For this reason, a small and stable measuring instrument that can be incorporated into a cane, an activity assisting device for the visually impaired, for the purpose of notifying the presence or absence of a step and the depth of the step is still practical. The fact is that it has not yet been converted.

[0005] By improving the ultrasonic sensor, a small measuring instrument using an ultrasonic sensor of either the open type or the drip-proof type can reliably detect the presence or absence of a step and its depth. There is a long-awaited need for a step detector that can be detected. On the other hand, since ultrasonic waves are diffused and attenuated as they propagate in the air, it is necessary to detect echoes from a road surface or the like at a short distance as much as possible in order to reliably detect the echoes without being affected by surroundings. . Therefore, when detecting the presence or absence of a step, it is desirable to attach an ultrasonic sensor near the tip of the cane.

However, when a normal ultrasonic sensor is used, reverberation after transmission lasts for several ms, and a small reflected wave from an object at a very short distance overlaps with the reverberation and cannot be easily identified. Transmitter and receiver sensors can be provided separately to prevent reverberation inside the sensor, but in this case also, strong ultrasonic waves immediately after transmission directly propagate in the air before obtaining reflected waves. There is a problem that reverberation is generated due to reception of the object and it is difficult to identify an object at a very short distance.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to address the above problems, and a first object of the present invention is to use a waveguide whose outlet shape and length are adjusted. To increase the signal-to-noise ratio between the reflected wave from the object and the reverberation inside the sensor, and to provide a level difference detector that is capable of identifying an object at a short distance and that can detect the presence or absence of a level difference and its depth. is there.

It is another object of the present invention to provide a level difference detector capable of maximally attenuating reverberation inside a sensor and detecting a signal with as high a sensitivity as possible.
A further object of the present invention is to provide an activity assisting device for the visually impaired, which can identify the presence or absence of a step and its depth by incorporating a small and practical step detector into a cane. .

[0009]

In order to solve the above-mentioned problems, a step detector according to the present invention is provided with a waveguide on the front surface of an ultrasonic sensor, and the exit of the waveguide is formed obliquely. The length is adjusted so that the reflected wave from the waveguide outlet and the reverberation inside the sensor cancel each other.

[0010] As described above, the waveguide is provided on the front surface of the ultrasonic sensor, and by adjusting the shape and length of the exit, the amplitude of the reflected wave due to the diffraction phenomenon of the ultrasonic wave occurring at this portion is reduced to a certain level. Since the reverberation inside the sensor can be canceled by the reflected wave from the waveguide outlet (open end), the S / N ratio of the reflected wave from the object and the reverberation can be increased to obtain a stable measurement value. It is possible,
Steps can be identified.

Further, in the step detector according to the present invention, in the above-described step detector, the length of the waveguide is set such that the phase of the reflected wave and the phase of reverberation inside the sensor are each other.
It is characterized by being adjusted to a length shifted by 0 °.

By setting the length of the waveguide so that the phase of the reflected wave from the exit of the waveguide and the phase of the reverberation are shifted by 180 °, the reverberation inside the sensor is maximized due to interference with the reflected wave. The signal can be detected with high sensitivity, and the operation can be stabilized.

Further, in the activity assisting device for the visually impaired person according to the present invention, a waveguide is provided on the front surface of the ultrasonic sensor, the exit of the waveguide is formed obliquely, and the length is guided. A step detector, which is adjusted so that the reflected wave from the wave tube outlet and the reverberation inside the sensor cancel each other, is provided outside or inside near the tip of the cane for detecting the presence or absence of an obstacle. Things.

By providing a waveguide outside or inside the ultrasonic sensor as described above and adjusting the exit shape and length thereof, the SN ratio is increased to improve sensitivity and stabilize operation. Therefore, by providing a small step detector using this ultrasonic sensor outside or inside near the tip of the cane, practical use of an activity assisting device for the visually impaired who can identify the step and its depth Can be tied.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram of a step detector and an activity assisting device for the visually impaired according to the first embodiment of the present invention, and FIG. 2 is a step detector and activity for the visually impaired according to the second embodiment of the present invention. FIG. 3 is a block diagram showing a measuring circuit of the auxiliary device, and FIG. 4 is a waveform diagram of an ultrasonic wave detected by the measuring circuit.

An embodiment of the present invention to be described below uses only the presence or absence of a reflected wave from an object in a certain time domain after transmitting an ultrasonic wave, so that the road surface can be moved to a distance corresponding to the time domain. And whether there is a step or not. In ultrasonic measurement, it is highly possible that a reflected wave of a component that is perpendicularly incident on the horizontal plane of a road or stairs is detected as a signal, so the time until the first reflected wave is detected is the distance to the road surface or the step Will represent the depth of

On the other hand, in the case of a cane, which is an activity assisting device for the visually impaired, the reflected wave becomes considerably small depending on the direction of the cane, so that the SN ratio, which is the ratio between the signal value and the noise value, must be increased. A stable measurement result cannot be obtained. Therefore, the first
In the embodiment, as shown in FIG. 1, a waveguide 3 for transmitting ultrasonic waves is provided on the front surface of an ultrasonic sensor 2 provided outside the vicinity of the tip of the cane 1 by being attached to the outside of the cane. By combining with the measurement circuit shown, stable measurement results can be obtained. 1A is a grip portion of the cane 1. In the second embodiment, as shown in FIG. 2, the ultrasonic sensor 2 is provided near the tip of the wand 1, and the waveguide 3 is built in the wand 1.

Since the amplitude and the waveform of the reflected wave from the exit (open end) 4 of the waveguide 3 vary significantly depending on the exit shape of the waveguide 3, the amplitude of the reflected wave from this portion is appropriately adjusted. The outlet 4 of the waveguide 3 is obliquely cut so as to be small. Since the wavelength of the reflected wave changes depending on the temperature (the phase is shifted), it is preferable that the wavelength can be corrected by a circuit. The length of the waveguide 3 is adjusted so that the phase of the reflected wave and the phase of the reverberation inside the ultrasonic sensor 2 cancel each other out, preferably, the phase is shifted by 180 °.

Further, as shown in FIG. 3, in the measuring circuit, the transmission / reception unit 5 for the ultrasonic sensor 2 changes the input impedance for each time domain after transmission, the reverberation attenuates quickly, and the signal is transmitted with as high sensitivity as possible. By making detection possible, the SN ratio is made higher, and at the same time, the waveform of the reverberation is made closer to the attenuation waveform of a single frequency so that the effect of the waveguide 3 can be easily obtained.

That is, the time signal 6 is set to several stages having different delay times, and the signal from the ultrasonic sensor 2 is transmitted and received by the transmitting / receiving unit 5 based on the pulse signal from the pulse generating unit 7.
The signal is transmitted and received by the amplifying unit 8 and amplified by the amplifying unit 8, and the detecting unit 9 detects whether a signal due to the reflected wave from the object appears in a time region set in several stages. Then, the signal is judged by the judging section 10 to identify a road surface having no step, a step having a depth of several steps, such as a step of about a stair, etc., and output the signal from the output section 11. It is desirable that the oscillation frequency from the ultrasonic sensor 2 can be changed to a frequency having an appropriate wavelength depending on the temperature.

According to the above-described embodiment, by utilizing the reflected wave from the waveguide 3 and the exit (open end) 4 thereof, the ultrasonic sensor 2 is used to determine the presence or absence of a step and the depth thereof. The degree can be detected. That is, since the ultrasonic waves from the ultrasonic sensor 2 do not diffuse when propagating inside the waveguide 3, the attenuation can be reduced, and the time elapses during that time, so that the reverberation inside the ultrasonic sensor 2 Can be attenuated.

As a result, by attaching the waveguide 3 to the front surface of the ultrasonic sensor 2, it is possible to considerably increase the S / N ratio between the signal due to the reflected wave from the object to be detected and the reverberation. On the other hand, when the waveguide 3 is used, a reflected wave is generated due to the diffraction phenomenon of the ultrasonic wave at the exit (open end) 4 of the waveguide 3, and SN is generated in the same manner as the reverberation inside the ultrasonic sensor 2.
Although the ratio is deteriorated, the amplitude and waveform of the reflected wave from the exit (open end) 4 of the waveguide 3 can be significantly changed by changing the exit shape of the waveguide 3.

Taking advantage of this, by changing the shape and length of the exit of the waveguide 3 to adjust the amplitude and phase of the reflected wave from the exit 4 of the waveguide 3, interference with the reflected wave causes The reverberation inside the ultrasonic sensor 2 can be canceled to a considerable extent. As a result, it is possible to further increase the S / N ratio by using the reflected wave from the waveguide exit 4 which was initially regarded as an obstacle.

FIG. 4 shows a waveform of an ultrasonic wave detected by the above-described measuring circuit. FIG. 4A shows a waveform when the outlet 4 of the waveguide 3 is cut perpendicular to the axis. ,
(B) shows the waveform when the exit 4 of the waveguide 3 is cut obliquely as described above and the length is adjusted so that the amplitude becomes maximum, and (C) shows the waveform when the exit 4 of the waveguide 3 is obliquely cut. And waveforms in the case where the length is adjusted so that the amplitude is minimized. These waveforms are obtained when the frequency of the signal is about 40 KHz, and the length of the time axis (horizontal axis) is 0.5 ms. is there.

By the synergistic effect of the above two effects, it is possible to prevent erroneous detection due to a low SN ratio when detecting an object at a short distance and to increase the sensitivity when detecting an object at an extremely short distance. Thus, the practicality of the step detector using the ultrasonic sensor 2 can be improved, and a small and practical step detector that can be incorporated in a cane as an activity assisting device for the visually impaired can be obtained.

Also, by improving the sensitivity of the step detector and stabilizing its operation, the unstable operation due to the fluctuation of the amplitude of the ultrasonic wave due to the manual operation of the wand by which the ultrasonic sensor is mounted by a person. Therefore, it is possible to provide an improved activity assist device for the visually impaired, which has a function of identifying the presence or absence of a step and the depth thereof, and can obtain a stable measurement value.

[0027]

As described above in detail, according to the step detector according to the present invention and the activity assisting device for the visually impaired using the same, the ultrasonic sensor can be provided by providing the waveguide on the front surface. Since the SN ratio can be increased and the operation can be stabilized, an object at a very short distance can be identified, and the presence or absence of a step and the depth thereof can be detected. As a result, a small and highly sensitive step detector can be obtained, and by incorporating it into a cane, the presence / absence of a step and the depth thereof can be identified. Can be planned.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a step detector and an activity assisting device for a visually impaired person according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a step detector and an activity assisting device for a visually impaired person according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a measurement circuit of the device.

FIG. 4 is a waveform diagram of an ultrasonic wave detected by the measurement circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Staff, 2 ... Ultrasonic sensor, 3 ... Waveguide, 4 ... Exit of waveguide

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mitsuhiro Saito 1-4-5-318 Nakao, Asahi-ku, Yokohama-shi, Kanagawa Prefecture (72) Norio Maekaku, 43 Funako, Atsugi-shi, Kanagawa Koper Electronics Co., Ltd. In-house F-term (Reference) 2F068 AA22 BB01 CC11 DD04 DD10 FF03 FF12 FF21 FF28

Claims (3)

[Claims] 1. A waveguide is provided in front of an ultrasonic sensor,
A step detector, wherein the exit of the waveguide is formed obliquely and the length thereof is adjusted so that the reflected wave from the exit of the waveguide and the reverberation inside the sensor cancel each other. 2. The step according to claim 1, wherein the length of the waveguide is adjusted so that the phase of the reflected wave and the phase of reverberation inside the sensor are shifted from each other by 180 °. Detector. 3. A waveguide is provided on the front surface of the ultrasonic sensor,
The exit of the waveguide is formed obliquely, and the length is adjusted so that the reflected wave from the exit of the waveguide and the reverberation inside the sensor cancel each other. An activity assisting device for the visually impaired, which is provided outside or inside near the tip of a cane for sensing.