WO2008032982A1

WO2008032982A1 - Ultrasonic sensor with different-directional directivities

Info

Publication number: WO2008032982A1
Application number: PCT/KR2007/004397
Authority: WO
Inventors: Byung Geuk Kim
Original assignee: Hagisonic Co., Ltd.
Priority date: 2006-09-13
Filing date: 2007-09-12
Publication date: 2008-03-20

Abstract

Disclosed is an ultrasonic sensor for detecting and dodging invaders or obstacles, by being mounted to a security alarm, an ultrasonic range finder, an industrial mobile robot, a robot cleaner and the likes. According to the present invention, the ultrasonic sensor is capable of detecting and dodging obstacles more accurately without a dead zone with only a few numbers, by forming an ultrasonic emission opening on a front of a housing in the form of an oval or rectangular slit to have different directivities according to its verticality and horizontality, applying a principle in that, when ultrasonic waves emitted from a piezoelectric diaphragm of the open ultrasonic sensor pass through the opening, the diffraction degree of waves varies depending on the wavelength of the waves and the width of the opening.

Description

ULTRASONIC SENSOR WITH DIFFERENT-DIRECTIONAL DIRECTIVITIES

Technical Field

[1] The present invention relates to an open ultrasonic sensor for detecting and dodging invaders or obstacles, being mounted to a security alarm, an ultrasonic range finder, an industrial mobile robot, a robot cleaner and the likes. More particularly, the present invention relates to an ultrasonic sensor capable of detecting and dodging obstacles more accurately without a dead zone with only a few numbers, by forming an ultrasonic emission opening on a front of a housing in the form of an oval or rectangular slit to have different directivities according to its verticality and hori- zontality, applying a principle in that, when ultrasonic waves emitted from a piezoelectric diaphragm of the open ultrasonic sensor pass through the opening, the diffraction degree of waves varies depending on the wavelength of the waves and the width of the opening.

[2]

Background Art

[3] As shown in Fig. 1, generally, an open ultrasonic range sensor comprises a unimorph diaphragm 200 including a metal disc 10 and a piezoelectric ceramic plate 20. The piezoelectric ceramic plate 20 has electrodes (not shown), one of which is bonded to the metal disc 10. A conical resonator 30 is attached to an upper surface of the metal disc 10. The diaphragm 200 is fixedly bonded by silicon to a base 50. A cylindrical plastic housing 90 having an ultrasonic emission opening 80 on a front thereof covers the unimorph diaphragm 200.

[4] In the drawing, a reference numeral "40" denotes a damping hole, "50" the base,

"60" a conductive wire, and "70" a terminal.

[5]

[6] As methods for widening a directional angle in the conventional open piezoelectric ultrasonic range sensor as shown in Fig. 1, shape alteration of the internal conical resonator 30 and adoption of a circular ultrasonic emission opening have been proposed. However, the shape alteration of the internal conical resonator 30 has a limit in widening the directional angle because emission pressure of ultrasonic waves may be decreased. Furthermore, the circular ultrasonic emission opening 80 as shown in Fig. 2 causes wide directivities omnidirectionally, thereby deteriorating accuracy of detection since unnecessary signals in a specific zone may be detected.

[7] Also, a horn-shape housing 90 as shown in Fig. 3 has been highly suggested in order to reduce the directional angle. However, such a horn-shape housing 90 increases the whole size of the sensor. [8]

Disclosure of Invention

Technical Problem

[9] Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide an ultrasonic sensor with different- directional directivities, capable of having a wide ultrasonic directional angle of about 180 horizontally and a limited directional angle vertically not to receive unnecessary signals such as doubly reflected sound waves, in almost the same size as a conventional sensor.

[10]

Technical Solution

[11] In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of an open ultrasonic sensor comprising a cylindrical housing and a unimorph diaphragm mounted in the housing, the unimorph diaphragm including a metal disc and a circular or square piezoelectric ceramic plate including electrodes of which one is bonded to the metal disc, a conical resonator attached to the metal disc, and an ultrasonic emission opening formed on a front of the housing to emit ultrasonic waves generated from the unimorph diaphragm, wherein the ultrasonic emission opening has a slit form relatively long in one of horizontal and vertical directions and relatively short in the other direction such that the ultrasonic waves emitted from the diaphragm and passing through the ultrasonic emission opening are diffracted by different degrees horizontally and vertically so that a directional angle of the sensor has different-directional directivities.

[12]

Brief Description of the Drawings

[13] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[14]

[15] Fig. 1 is a sectional view of a conventional open ultrasonic sensor;

[16] Fig. 2 is a perspective view of a conventional sensor with a large directivity;

[17] Fig. 3 is a sectional view of a conventional ultrasonic sensor with a horn-type housing;

[18] Fig. 4 is a perspective view of an ultrasonic sensor according to an embodiment of the present invention; [19] Fig. 5 is a front view of the ultrasonic sensor shown in Fig. 4;

[20] Fig. 6 is a sectional view of the ultrasonic sensor shown in Fig. 4;

[21] Fig. 7 shows a diffraction degree of ultrasonic waves according to the width of an ultrasonic emission opening;

[22] Fig. 8 is a perspective view of a ultrasonic emission opening for different-directional directivities in a robot platform to which the ultrasonic sensor according to the present invention is attached;

[23] Fig. 9 is a front view of various types of the ultrasonic emission opening;

[24] Fig. 10 is a graph illustrating directivity of the ultrasonic sensor with respect to a horizontal direction;

[25] Fig. 11 is a graph illustrating directivity of the ultrasonic sensor with respect to a vertical direction;

[26] Fig. 12 is a plan view illustrating a sensing range of a mobile robot mounted with a plurality of ultrasonic sensors according to the present invention;

[27] Fig. 13 illustrates a sensing range of a mobile robot mounted with a single ultrasonic sensor according to the present invention, through a plan view and a side view;

[28] Fig. 14 is a graph illustrating directivity of a conventional ultrasonic sensor with respect to a horizontal direction; and

[29] Fig. 15 is a plan view illustrating a front sensing range of the mobile robot mounted with a plurality of conventional ultrasonic sensors, and a dead zone.

[30]

Best Mode for Carrying Out the Invention

[31] Referring to Figs. 4 through 6, an ultrasonic sensor according to an embodiment of the present invention comprises a unimorph diaphragm 200 including a metal disc 10 and a circular or square piezoelectric ceramic plate 20. The piezoelectric ceramic plate 20 has electrodes (not shown) on upper and lower surfaces thereof, and at least one of the electrodes is bonded to the metal disc 10. The ultrasonic sensor further comprises a conical resonator 30 attached to an upper surface of the metal disc 10 to improve ultrasonic efficiency, a base 50 supporting the diaphragm 20 and having a damping hole 40, leads 70 connected to the metal disc 10 and the piezoelectric ceramic plate 20 through conductive wires 60, an adhesive bonding the diaphragm 200 to the base 50 and sealing a gap between the diaphragm 200 and the base 50, and a housing 90 having an ultrasonic emission opening 80. The housing 90 is fixedly bonded to the base 50, non-contactingly covering the diaphragm 200 and the conical resonator 30.

[32] The ultrasonic emission opening 80 is vertically positioned in a rectangular form so that ultrasonic waves generated from the diaphragm 200 have different directional di- rectivities horizontally and vertically, respectively. The ultrasonic emission opening 80 is provided with an ultrasonic emission screen 81 to prevent entry of dust and other foreign substances into the housing 90.

[33]

[34] When a predetermined electric signal is applied between the electrodes formed at the metal disc 10 and the piezoelectric ceramic plate 20, the diaphragm 200 vibrates in a longitudinal bending mode. As shown in Fig. 7, the directional angle (-6dB) can be controlled as the diffraction degree of the ultrasonic waves is varied according to the width of the ultrasonic emission opening 80. If the width of the ultrasonic emission opening 80 is too narrow, the emission efficiency is remarkably deteriorated.

[35]

[36] Instead of the ultrasonic emission opening 80 for different-directional directivities formed through the housing 90 as shown in Figs. 4 through 6, an ultrasonic emission opening 140 having the same configuration as in the previous embodiment may be formed at an ultrasonic emission unit 130 outside the ultrasonic sensor as shown in Fig. 8 to achieve the same effect. In Fig. 8, the ultrasonic sensor is designated by reference numeral " 110." The ultrasonic emission opening 140 can be applied to various fields including a robot platform 120 and a rear side of a car.

[37]

[38] Fig. 9 shows various types of ultrasonic emission openings applicable to the ultrasonic sensor according to the present invention. However, the ultrasonic emission opening according to the present invention is not limited to those types of Fig. 9 but can be in other types including oval and rectangular, as long as it guarantees the different-directional directivities and appropriate sensitivity.

[39]

[40] Fig. 10 and Fig. 11 are graphs illustrating directional angles measured by the ultrasonic sensor having the ultrasonic emission opening shown in Figs. 4 through 6. The sensor herein used has a 4OD nominal frequency and 16D diameter. The ultrasonic emission opening has a rectangular form of 2Dx4D. According to the present invention, due to diffraction of the waves, the ultrasonic emission opening generally has about 180° wide directional angle in a horizontal direction and about 60-70° directional angle in a vertical direction. In this embodiment, more specifically, the ultrasonic emission opening has a wide horizontal directional angle of 172° for wide-range sensing and a vertical directional angle of 66 for preventing reception of unnecessary signals.

[41]

[42] Thus, as shown in Figs. 12 and 13, when applied to the robot platform 120 to detect forward obstacles and measure distances to the obstacles, the ultrasonic sensor is capable of covering a whole front side with only a few numbers. Furthermore, the limited vertical directional angle reduces undesired reception of signals.

[43]

[44] On the other hand, when the conventional ultrasonic sensor having a 60 horizontal directional angle is applied to perform forward sensing of the robot platform 120 as shown in Fig. 14, a dead zone is generated in a short-distance area as shown in Fig. 15. Therefore, more sensors are required to reduce the dead zone, thereby increasing the expenses.

[45]

[46] According to the present invention, as described above, the ultrasonic emission opening of the ultrasonic sensor is configured in a slit form being relatively longer in one of horizontal and vertical directions while relatively shorter in the other direction, so that the ultrasonic waves are emitted by a wide directional angle, i.e. about 180° horizontally. As a consequence, when the ultrasonic sensor is applied to a mobile robot, a range finder and the likes, the sensing range can be improved. In addition, the limited directional angle in the vertical direction helps prevent detection of unnecessarily reflected signals.

[47]

[48] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

[49]

Industrial Applicability

[50] An ultrasonic sensor according to the present invention is appropriate for detecting and dodging obstacles by being mounted to a security alarm, an ultrasonic range finder, an industrial mobile robot, a robot cleaner and the like.

Claims

[1] An open ultrasonic sensor comprising a cylindrical housing and a unimorph diaphragm mounted in the housing, the unimorph diaphragm including a metal disc and a circular or square piezoelectric ceramic plate including electrodes of which one is bonded to the metal disc, a conical resonator attached to the metal disc, and an ultrasonic emission opening formed on a front of the housing to emit ultrasonic waves generated from the unimorph diaphragm, wherein the ultrasonic emission opening has a slit form relatively long in one of horizontal and vertical directions and relatively short in the other direction such that the ultrasonic waves emitted from the diaphragm and passing through the ultrasonic emission opening are diffracted by different degrees horizontally and vertically so that a directional angle of the sensor has different-directional directivities.

[2] An open ultrasonic sensor comprising a cylindrical housing and a unimorph diaphragm mounted in the housing, the unimorph diaphragm including a metal disc and a circular or square piezoelectric ceramic plate including electrodes of which one is bonded to the metal disc, a conical resonator attached to the metal disc, and an ultrasonic emission opening formed on a front of the housing to emit ultrasonic waves generated from the unimorph diaphragm, the ultrasonic sensor further comprising: an ultrasonic emission unit disposed outside the sensor and including an ultrasonic emission opening having a slit form relatively long in one of horizontal and vertical directions and relatively short in the other direction so that the ultrasonic waves emitted from the diaphragm and passed through the ultrasonic emission opening are diffracted by different degrees horizontally and vertically and therefore a directional angle of the sensor has different-directional directivities.

[3] The ultrasonic sensor according to any of claim 1 and claim 2, wherein the ultrasonic emission opening has an oval or rectangular form.

[4] The ultrasonic sensor according to claim 3, wherein the ultrasonic emission opening includes an ultrasonic emission screen for preventing entry of foreign substances including dust as long as not deteriorating different-directional directivities and sensitivity of the ultrasonic sensor.