CA2267435C - Ultrasonic distance detection for visually impaired pedestrians - Google Patents

Abstract

Ultrasound is used to determine, by echo ranging, the distance of objects in front of a user for allowing a visually impaired pedestrian to walk safely. A double circuit allows two simultaneous measurements. Distances measured are converted into human paces or steps. Then each ear of the human receives measurement information. The user can calibrate the apparatus for his or her own stride.

Description

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Ultrasonic Distance Detection for Visually Impaired Pedestrians FIELD OF THE INVENTION

The present invention relates to obstacle detection devices to be used by visually impaired pedestrians. More particularly, the present invention relates to an ultrasonic-based obstacle detection device.

BACKGROUND OF THE INVENTION

The task facing visually impaired pedestrians is the task of independently starting from a point and ending at a destination. This seems simple. However, it appears to be extremely challenging once the factors affecting mobility are taken into account. If one were to close his eyes and tried to move just a few steps, it would not take long for him to realize that the visually impaired have no access to basic information such as spatial orientation, the nature of the obstacles, the presence of moving objects, or even the boundaries of the path or travel surface.

Travelling aids have long been developed in efforts to allow visually impaired pedestrians to travel and move about safely and comfortably. One of the first versions and the most widely up to the present is the long cane.
Since the 1960's, several types of electronic travel aids (ETA) have been developed to improve the mobility of visually impaired pedestrians. Some of these devices are now currently available. The Russell Pathfinder provides on such example it first came into use in 1965 and employs an ultrasonic beam to detect objects. It provides a vibrating warning which is inversely proportional to the distance.
The Nottingham Obstacle Detector, designed in 1973, is a hand-held device which provides an auditory readout of the distance between the visually impaired individual and the object with eight musical notes. Recent technical development permit the use of a human voice to communicate the distance between the visually impaired individual and the object by a voice message.

1 .

U.S. Patent 4,870,687 to Deleon discloses an oral readout rangefinder. It orally announces the measured distance by using of a speech synthesiser. U.S.
Patent 5,508,699 to Silverman discloses a dual sensing identifier / locator device for the visually impaired. It composes of two parts. Transmitters attached to a variety of objects send out coded signals to indicate the names of the objects. A
receiver attached to the user decodes the signal and produces audible output which includes the name of the object and the distance. U.S. Patent 5,347,273 to Katiraie discloses an ultrasonic detection system. It is basically a collision sensing system adapted use by both automobiles and the visually impaired. For the visually impaired application, transducers are mounted on a cane. It gives the exact distance of an obstacle from the visually impaired using the device by a voice message. U.S. Patent 5,724,313 to Burgess et al discloses a guide device using pitches and tones to inform the user of the nature of the obstacle.

All of these devices, some of which have been innovative in their own way, have serious deficiencies. They have often lacked functionality and compactness necessary for one who will use the device while walking. The distance information provided has often at best been impractical and at worst incomprehensible to a visually impaired individual. They generally have lacked the ability to adapt to the needs and characteristics of the visually impaired individual who will use the device. Thus, what is need is a compact functional device which readily adapts to the needs and characteristics of a visually impaired individual. A device which provides in a readily comprehensible and intuitive form information on the distance between a visually impaired individual and an object that person is approaching.

SUMMARY OF THE INVENTION

2 It is an object of the present invention to provide an ETA method and apparatus for a visually impaired individual which is economical and easy to use so that a visually impaired individual can safely move about on his or her own.

It is an object of the present invention to provide an ETA obstacle detection device and method for guiding visually impaired pedestrians in a safe, comfortable and easy manner.

It is yet another object of the present invention to provide an ETA method and apparatus which provides information on distance to an object in an intuitive manner which makes it easy for the visually impaired individual to easily and quickly understand the distance units and what they actually represent in their own experience.

It is yet another object the present invention to provide an ETA with a method and apparatus which provides distance information in units of step or stride of an individual.

It is yet another object of the present invention to provide a means for the user to calibrate the apparatus to their own personnel preferences or characteristics.

It is yet another object of the present invention to provide an ETA
apparatus which is provided in an easy to use, compact and unobtrusive package.

The present invention provides an ETA apparatus and system which uses ultrasonic sound as a ranging medium with a dual channel transducer driver system to determine by echo ranging the distance of objects in front of a user of the ETA apparatus. The apparatus converts the information obtained from the time difference between an ultrasonic transmission and its subsequent echo to determine distance and it communicates the measure of distance to the user in measurements of normal human strides. The information on distance is presented to the user by pre-recorded statements of the number of strides or steps to the object or obstacle detected.

3 In a further aspect of the present invention a twin channel transducer allows it to discriminate the between objects which are on the left or right side of the path of travel of the user and to determine which is closer.

In yet another aspect of the invention information on distances and location of objects is provided to the user by a dual channel sound system which discriminate between objects or obstacles on the left or right of the user.
The system, in it s preferred embodiment has ear phones for each ear which transmit the information by the left or right or both audio channels depending on the position of an obstacle or obstacles by sending a audio signal that is louder to the side that the an object is closer on as well as an audio distance message.

In yet another aspect of the present invention it incorporates the ETA of the present invention within the frame of glasses for the visually impaired pedestrian. The electronics being in a miniaturised configuration.

In yet further aspect of the present invention it provides a method and apparatus for the user to calibrate the distance of the stride used to measure and inform the user of distance to an object to the users preferred stride or step characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by an examination of the following description, together with the accompanying drawings, in which:

Fig. 1 is the block diagram of the major functional components of the present invention;

Fig. 2 is a perspective view of glasses which incorporate the present invention in one possible embodiment of the present invention;

Fig. 3 provides a flow chart which depicts the functional steps of the present invention;

4 Fig. 4 is the timing diagram of the major signal generated during operation of the present invention; and Fig. 5 of one arrangement and use of the memory address which make up a memory of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The overall apparatus.
The invention works on the well known principle of range and direction finding with reflected ultrasonic sound waves in a fashion similar to the operation of radar and sonar. The ultrasonic travel aid of the present invention allows the measurement of distance between two points by emitting a short burst of high frequency sound waves and listening for an echo. When the echo is received, the time elapsed between the outgoing and reflected sound pulse is measured.
Knowing the speed of the sound wave and the time taken to travel, the distance from the emission point of the ultrasound to the object can be calculated by the formula: D = (S x T) / 2, where D stands for the total distance traveled, S
for the speed of sound wave and T for the time elapsed.

Ultrasound essentially means "high frequency sound." The frequency range of ultrasound is from twenty to five hundred thousand vibrations per second, too high for human beings to perceive. It was chosen as the transmission medium over other mediums, such as light or radio waves or lower frequency sound waves because of its unique characteristics. Sounds at higher frequencies are more directional and focused than lower frequency waves.
Ultrasonic waves can also be focused much like a beam of light. Therefore, an obstacle will more strongly reflect a beam of ultrasound waves than lower frequency sound waves. Because of its relatively slow speed of propagation, it is easy to detect. Furthermore, the ultrasonic sensor, a device which transmits ultrasonic pulses and receives the reflected echoes, can withstand extremely harsh environments, making it more suitable for outdoor applications.

Since the visually impaired are unable to read visual display, audio is the most efficient way to communicate information to the user. Musical notes have long been used to represent distance. Many ETAs also use vibrations where the intensity of the vibrations warn the user of the range between him and the obstacle. However, these methods leave the visually impaired user to translate notes or vibrations into an understanding of the distance. This is ineffective and often leads to confusion or worse for the visually impaired user.
One of the objectives of the present invention, the ultrasonic travel aid, is to improve the presentation of information, a common shortcoming of ETAs up to now. The new method uses state of the art technology to present distance in human voice. If the distance is given in either meters, feet, inches etc. most person especially the visually impaired still have difficulty in conceptually understanding units of measure expressed in this form. Therefore, an artificial intelligence is added by presenting the units of distance in steps or strides corresponding to the length of the user's stride. The length of ones own a step or stride is a unit which everyone can comprehend without difficulty. This is particularly true of the visually impaired, many of which have had such impairment from birth and thus have a greater conceptual difficulty in translating distance measurements into something understandable.

As depicted in Fig. 1, a block diagram of the major functional parts the present invention, the ultrasonic travel aid consists of four major functional parts:
a Timing Control Logic module 23, an Ultrasonic Generation module 25, a Time-to-Distance Conversion module or Distance and Direction discrimination module 24, and an Information Presentation interface 22. The invention has a fifth component a Calibration module 33 which, as will be explained below in detail, is used to adjust the unit to the personnel stride or step characteristics of the individual user.

The Ultrasonic Generation module 25 has two sub-components composed of two parts each. A left ultrasonic driver 27 which drives a left ultrasonic transducer 31 and a right ultrasonic driver 26 which drives a right ultrasonic transducer 30. When commanded the right 26 and left 27 ultrasonic drivers produce in their respective ultrasonic transducers 30 and 31 burst of ultrasonic sound. Likewise when the transducers 30 and/or 31 receive a return echo they communicate receipt of this echo to their respective ultrasonic driver. Having a separate circuit and transducer for the right and left side allows, the system can determine which side the object being approached is on or if it is across the entire path of the user.
The ultrasonic drivers 26 and 27 are controlled by and communicate with the logic control and timing module 23. The logic control and timing module sends the signal which instructs each ultrasonic driver 27 and 27 to emit periodic bursts of ultrasonic sound through their respective transducers. In turn when the ultrasonic transducers 30 and 31 receive an echo they communicate this event to the logic control and timing module 23. If, as will be discussed in detail below, the echo is received within the requisite period of time it will initiate the necessary process to determine the distance to the object created the echo, by reflecting the ultrasonic sound, by the distance and direction discrimination unit 24.
The distance and direction discrimination unit 24 upon receiving the necessary signals and information from the logic control and timing unit determines the distance and activates the information interface 22 which will in turn advise the user of the presence of an object or objects in its path with in the normalized distance. The normalized distance being the maximum distance which the unit is set to detect objects. Standard transducers which would function with the present invention have a range of about 20 to 30 meters. However, the normalized distance in the preferred embodiment is about 10 meters a distance equivalent to roughly 30 to 33 steps or strides by the average individual.
The information presentation interface 22 is made up of an information presentation module 28 which drives a right audio channel driver 26 and audio output 34 and a left audio channel driver 27 and audio output 35. The two separate audio channels one for each ear plus the corresponding left and right ultrasonic transducers give the apparatus and system of the present invention the ability to distinguish which side an object sits on or if it sits across the entire path the individual user.
Fig. 2 depicts how the glasses 39 of the preferred embodiment of the present invention might appear. The most notable features would be the left 27 and right 26 transducers. Left 35 and right 34 audio output devices, in the preferred embodiment would be typical small ear phones which the user would insert into each ear. The remainder of the electronics which makes up the invention would be typical miniaturized built in to temple supports 40 and 41.
Actual electronic parts have not been identified for the functional parts enumerated with respect to Figs. 1 and 2 since those skilled in the art, once they understand the concepts enumerated herein will be able to obtain the necessary parts to fabricate the present invention without any difficulty.

Operation of the invention:

Fig. 3 provides a flow diagram which depicts the over all operation of the system of the present invention. In the preferred embodiment every two seconds, the Timing Control Logic module generates an INIT signal which will allow the Ultrasonic module to emit a burst of ultrasonic waves 42. The transducers 30 and 31 then listen for returning echoes 43. In the meantime, this INIT signal is also sent to the Time-to-Distance Conversion module to start counting pulses 42.
Upon detecting an echo, the Ultrasonic module sends out an ECHO
received signal 44 which is then passed on to the Time-to-Distance Conversion module 24 which then stops counting pulses 46. The Time-to-Distance Conversion module 24 then determines if the distance is within the normalized distance 47. If it determines 48 yes it is it then counts the number of pulses generated by the timing mechanism between the INIT signal and the signal to stop timing 49. The Information Presentation module 28 then reads out the number of pulses counted between the INIT and ECHO signals and determines the distance in strides 50. This information is then transmitted to the user in the form a human voice 51.

Fig. 4 provides a timing diagram with the major signals generated during normal operation of the present invention. The system first generates a start or INIT signal 53 which initiated generation of ultrasonic pulses by the transducers and the commencing of the timing or distance count 55. Commencing of the distance count involves commencing of the timing pulses 55A. A periodic reset signal 56, generally one every two seconds, commences the start or INIT signal 53. Upon receipt of an echo an ECHO signal is received which halts the timing sequence 55 and generates a sound enable signal.

Presentation of Distance as Strides:

The ultrasonic travel aid does not directly measure the distance to an object. Instead, it measures the time taken for the ultrasonic waves to make a round trip from its transducer 30 and 31 to an object and back again.
Therefore, knowing the speed of ultrasound and the time taken to travel for a round trip, the distance between the user and the object can be calculated using the formula:
D
= (S x t)/2. However, it is difficult to apply this formula directly.
Nevertheless, we know that the speed of ultrasound is approximately 343 m/s, which implies that it takes ultrasound waves 2.925 milliseconds to travel one meter. If we can generate pulses at 2.925 millisecond per cycle, then, by counting the number of pulses between INIT and ECHO signals, we would know the distance in meters immediately.
As mentioned above, it is difficult for the visually impaired to comprehend distance in meters. Hence a little "artificial intelligence" is added. The distance is given out in the form of steps. For example, ultrasonic waves travel 0.343 meters per millisecond, that is approximately the length one step of an adult.
Consequently, if logic timing module 23 generates pulses at one millisecond per cycle as time base, we would know the distance in steps instead of meters.
This time base can be easily changed to suit the user with different length of step.
One of the unique features of the present invention is the presentation of distance by the human voice. State of the art static recorder chip is used to convert the number of steps into human voice. The information presentation module 28 can be a standard static recorder chip which allows the recording of messages onto the chip for played back at any time. Around thirty messages was to be recorded, and a systematic procedure was derived to allow messages to be played back with as little delay as possible.
Two methods are possible. The first being message cueing to a recorded message. This proved to be difficult for the delay was too long in order to skip messages. The second method involved accessing a recorded message by a specific address. The standard static recorder which can be used contains six hundred addresses with a total duration of sixty seconds. This means that one second of recording time is equivalent to ten address counts. If each message lasted 1.6 seconds, it could be stored in the space of sixteen addresses.
Since sixteen is an "even" binary multiple, we can ignore all the counts less than sixteen by strapping the corresponding bits to ground and programming the remaining bits. This simplifies the design tremendously, now, the address of messages stored in the chip are directly related to number of steps, as shown in the table at Fig. 5. In this way, the voice recording of "n steps" can be directly accessed by the number of steps measured by Time-to-Distance Conversion module 24.

Calibration:
The present invention includes a means to calibrate the apparatus to the individual stride or step characteristics of the user. To calibrate the present invention the user simply activates the calibration module 33 of Fig. 1 with control 79. Once the apparatus is placed in the calibration mode the user takes three average strides. At the start of the strides or steps he or she turns on the timer and at the end of the three strides or steps turns the timer off. The unit then determines the number of pulses equivalent to the average stride of the user calibrating the device. This information is stored to memory on the system and used to determine the distance in strides of the user.

An Additional View of The Invention:

As noted above the present invention as depicted in Fig. 1 is an obstacle ranging system for visually impaired pedestrians comprising a dual sensing module 25, a distance and direction discrimination module 24, a logical control module 23, an information presentation interface 22, a time base generator module (which in the preferred embodiment forms part of the logical control module or the distance and direction discrimination module), and a calibration module 33.

The dual sensing module 25 comprises two ultrasonic drivers 27 and 26.
The ultrasonic drivers transmits a burst of ultrasonic signals when it receives the START or INIT command and listens for the reflection. When the reflections from the obstacle are received by the ultrasonic driver, it sends out an ECHO
signal.
The two channels of the dual sensing module 25 operate independently of each other and the system of the present invention is able to process the information from each channel separately and determine if two different objects are on the left and right side of the path of the user are at different distances from the user and which is closer to the user of the invention.

The time-base generator module in the preferred embodiment is incorporated in the logical control module or the distance and direction discrimination module. However, it could be separately configured item without to much difficulty. The purpose of the time-base generator module is to generate step-time base pulse 55A of Fig. 4. It comprises a crystal clock generator and a counter. When it receives a START signal from the control logic module, it begins to generate step-time base pulse. It uses the step length (number of crystal clock cycle) stored in the calibration module as a reference. The reference having been set during the calibration mode. The reference being a measure of the average stride of the user. When the crystal clock cycle reaches this number, it generates a time-base pulse. When it receives a STOP signal from the control logic module when the control logic module receives and echo signal from one of the ultrasonic drivers 26 or 27, it resets the time-base generation counter. It should be noted that this process occurs separately for each ultrasonic driver allowing the system to discriminate between information received from each channel of the dual sensing module 25.

The distance/direction discrimination module 24 is the heart of the invention. This module includes the dual clock counter, a dual time/distance conversion part, a distance to step conversion part and direction discrimination part. When the control logic module sends out the INIT signal to the ultrasonic module, it also starts a counter to count the number of clock cycles. When the module receives the ECHO signal, it stops counting. The counted number of clock cycles is proportional to the distance between the obstacle and the sensor.

The direction discrimination determines which obstacles detected by the dual ultrasonic driver is closer to the user. To do this, it compares the dual clock counter outputs, taking the smaller one which represents that the object is close to the user. In the preferred embodiment of the present invention outputs from the dual clock counter will be normalized by a preset value which represents the largest distance the sensor can measure. As noted the preferred embodiment of the present invention has a maximum range of 20 to 30 meters; however, as a practical matter the actual range in the preferred embodiment is normalized to a maximum of 10 meters, anything beyond this distance being indicated by the system as beyond range. The output of the normalized counter number is used by the information presentation module in presenting the information on distance to the user of the system.

The control logic means control of the operation of the talking glasses.
The flow chart of Fig. 3 and the timing diagram of Fig. 4 indicate the procedure it uses for control and operation of the system. It first sends out a INIT signal which will start the dual ultrasonic driver module, start the dual distance measurement counter, reset the static recorder and an internal step down counter. When it receives an ECHO signal from the ultrasonic driver module, it will stop the corresponding distance counter. When it receives both ECHO signals from the dual ultrasonic driver, it sends out a signal to the distance/direction discrimination module to start the process of determining the distance to the object or objects which side are they on etc.. When the module stops processing, it sends out a signal to the information presentation module to present the information to the user based on the information provided to the information presentation module by the Distance and Discrimination module.

The information presentation module can be best understood by Fig. 1 and Fig. 2. It has two parts, an audio generation part and what amounts a 3-D
surrounding sound generation part or more correctly left and right sound channels. The audio generation part contains pre-recorded information, such as "one step", "two steps", "three steps"..... This information is stored using static record technique and it can accessed by index by standard procedures well known in the industry. Thus, the number of steps can be used directly as audio information index. It should be noticed that when the distance is too far, for example, excess the possible distance that ultrasonic driver can measure or is beyond the normalized range, the audio output is "too far". However, when the distance is too close, for example, less than one step, the audio output will be "too close". The second part is to use of the left channel right channel audio out put to present the direction information. When an obstacle on the left hand side is closer than an obstacle on the right hand side, the left hand side audio output will be more pronounced or louder than the right hand side audio output. The depth of field or range is controlled by the normalized distances for both left hand side and right hand side as described above.

The calibration module 33 as depicted in Fig. 1 has a control 79 in the preferred embodiment a push button. The calibration module 33 also has a time-base input and means to store the step length pertaining the user. The time base input is generated by the clock generator of the system. When the device is powered, a predefined number of time bases corresponding to the length of one step is loaded into the step length memory. When the user pushes the calibration button the system of the invention is in the calibration mode. It measures a predefined number of steps, for example, three steps. The number of time bases corresponding to the length of one step will be calculated and stored in the step length memory which will be used as the reference to convert the distance measurement into number of steps.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and detail may be made to it without departing from the spirit and scope of the invention.

Claims (17)

The invention claimed is:

1. A method for assisting a visually impaired person in determining a distance to an object in a path of said visually impaired person, said method comprising:
creating a stride length unit that corresponds to a stride length for the visually impaired person;
storing the stride length unit in memory;
projecting from a location adjacent to the visually impaired person at least one ultrasonic transmission;
listening for an echo of the at least one ultrasonic transmission generated by said object;
determining said distance in said stride length unit using the echo of the at least one ultrasonic transmission; and communicating the distance in said stride length unit to the visually impaired person.

2. The method of claim 1 wherein said creating a stride length unit comprises determining a number of pulses in said at least one ultrasonic transmission equivalent to an average stride of the visually impaired person.

3. The method of claim 1 wherein said communicating comprises communicating an audio signal.

4. The method of claim 3 wherein said communicating an audio signal comprises providing a human voice which states a total number of strides to the object which created the echo.

5. The method of claim 4 wherein said providing a human voice comprises providing a data bank of prerecorded human voice transmissions with a range of strides for communication to the visually impaired person.

6. The method of claim 1 wherein said projecting comprises projecting at least two parallel independent ultrasonic transmissions, and said listening comprises listening for an echo of the at least two parallel independent ultrasonic transmissions independently.

7. The method of claim 6 wherein said projecting and said listening comprises mounting a first ultrasonic transducer on a right side of a pair of glasses worn by the visually impaired person for projecting a first ultrasonic transmission and listening for an echo thereof and mounting a second ultrasonic transducer on the left side of the pair of glasses for projecting a second ultrasonic transmission and listening for an echo thereof.

8. The method of claim 6 further comprising determining if two or more different objects are on either side of the forward direction and determining if one is closer to the visually impaired person, and communicating this information.

9. An apparatus for determining a distance to an object, the apparatus comprising:
an ultrasound generation module adapted to generate at least one ultrasonic pulse and receive an echo off of said object;
a calibration module for recording a stride length of a user and creating a stride length unit that corresponds thereto;
a memory for storing said stride length unit;
a distance and direction module connected to said ultrasound generation module and adapted to measure a duration between a generated pulse and a received echo and determine said distance in said stride length unit using said duration; and an information presentation module connected to said distance and direction module and adapted to communicate said distance in said stride length unit to said user via an audio signal.

10. The apparatus of claim 9 wherein said ultrasound generation module comprises a left ultrasonic driver operatively connected to a left transducer and a right ultrasonic driver operatively connected to a right transducer.

11. The apparatus of claim 10 wherein said left ultrasonic driver is adapted to send a left ultrasonic pulse and to receive a left echo generated by said object, and wherein said right ultrasonic driver is adapted to send a right ultrasonic pulse and to receive a right echo generated by said object.

12. The apparatus of claim 11 wherein said information presentation module further comprises left and right channel audio drivers for signaling to said user a location of said object.

13. The apparatus of claim 12 wherein said apparatus is miniaturized to be positioned on said user in an unobtrusive manner, said left transducer being positioned to provide coverage of an area to a left and front side of said user and said right transducer being positioned to provide coverage for a right and front side of said user.

14. The apparatus of claim 13 wherein said left audio channel driver connects to a first audio output device positioned at an end of a left ear of the user and said right channel audio driver connects to a second audio device positioned at an end of a right ear of the user.

15. The apparatus of claim 14 wherein said apparatus is integrated in a set of glasses.

16. The apparatus of claim 9, wherein said calibration module is adapted to record a duration of a given number of strides of said user and determine a duration of an average stride.

17. The apparatus of claim 10, wherein said distance and direction module comprises:
a distance base generator operatively connected to a left distance counter and a right distance counter, and wherein said distance based generator communicates to said left and right distance counters to commence a left timing cycle and a right timing cycle, respectively, and communicates to said left distance counter and said right distance counter to halt said left timing cycle and said right timing cycle, respectively;
a distance extractor operatively connected to said left and right distance counters which upon receipt of information on a halted timing cycle from said left and right distance counters determines a distance to said object which created said echo; and a directional information generator operatively connected to said left and right distance counters which based on a timing differential between said left timing cycle and said right timing cycle determines which of a left object which creates a left echo and a right object which creates a right echo is closer to said user.