Physical object detection system

• US 20100220551A1
• Filed: 02/12/2010
• Published: 09/02/2010
• Est. Priority Date: 02/27/2009
• Status: Active Grant

• Current Assignee: DENSO Corporation, Nippon Soken, Inc. (DENSO Corporation)
• Original Assignee: DENSO Corporation, Nippon Soken, Inc. (DENSO Corporation)
• Inventors: Yoshida, Takahiko, Matsuura, Mitsuyasu, Akiyama, Keiko, Okuda, Yasuyuki, Isogai, Toshiki
• Granted Patent: US 8,248,887 B2
• Time in Patent Office: Days
• US Class Current: 367/99
• CPC Class Codes: G01S 15/101 Particularities of the measurement of distance G01S15/12, G01S15/14, and G01S15/18 take precedence
• CPC Class Codes: G01S 15/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S15/46
• CPC Class Codes: G01S 15/87 Combinations of sonar systems
• CPC Class Codes: G01S 15/931 of land vehicles
• CPC Class Codes: G01S 2015/938 in the bumper area
• CPC Class Codes: G01S 2015/939 vertical stacking of sensors, e.g. to enable obstacle height determination
• CPC Class Codes: G01S 7/52003 Techniques for enhancing spatial resolution of targets G01S7/52046 takes precedence
• CPC Class Codes: G01S 7/52006 with provision for compensating the effects of temperature
• CPC Class Codes: G01S 7/521 Constructional features
• CPC Class Codes: G01S 7/524 Transmitters
• CPC Class Codes: G01S 7/527 Extracting wanted echo signals Doppler systems G01S15/50
• CPC Class Codes: G01S 7/539 using analysis of echo signal for target characterisation; Target signature; Target cross-section

Abstract

In an obstacle detection system, a wave transmitted by a transmitting element and received by receiving elements as a receiving wave includes extraneous waves, which are reflection waves from other than an obstacle, and obstacle reflection waves from an obstacle. It is determined that, an obstacle is present, if the reflection waves are detected as having an amplitude (voltage) greater than a threshold level and a reception time difference between time points at which the amplitude exceeds threshold level at the receiving elements is less than a predetermined time.

Claims

1. A physical object detection system comprising:

at least one transmitting element for transmitting a transmission wave;

at least two receiving elements for receiving a reflection wave, which corresponds to the transmission wave reflected by a physical object; and

an electronic unit for detecting presence of the physical object based on a phase difference between the reflection waves received by the receiving elements,

wherein the electronic unit includes;

a detection section configured to detect a set of waves, each of which is a part of the reflection wave received by each of the receiving elements and has an amplitude greater than a predetermined level, a time difference between time points at which the amplitudes of the set of waves exceed the predetermined level is less than a predetermined time interval; and

a determination section configured to determine presence of the physical object when the set of waves are detected between the receiving elements.

2. The physical object detection system according to claim 1, wherein:

the determination section is configured to determine that the physical object is an irregular reflection body, which reflects the transmission wave irregularly, when the detection section detects a set of waves, each of which is a part of the reflection wave received by each of the receiving elements and has an amplitude greater than the predetermined level, a time difference between time points at which the amplitudes of the set of waves exceed the predetermined level is greater than the predetermined time interval.

3. The physical object detection system according to claim 2, wherein:

the determination section is configured to determine that the irregular reflection body is one of a road surface, a net structure and a tree.

4. The physical object detection system according to claim 1, wherein:

the detection section is configured to detect the set of waves by adding synchronously the amplitudes of the reflection waves received by the receiving elements and detecting a set of waves, which provide a sum of added amplitudes is greater than a predetermined threshold value.

5. The physical object detection system according to claim 1, wherein:

the detection section is configured to detect the set of waves by calculating a coefficient of correlation between waves of the reflection waves, which are received by the receiving elements and corresponds to each other, at every predetermined interval and detecting a set of waves, which provide the coefficient of correlation greater than a predetermined value.

6. The physical object detection system according to claim 1, wherein:

the detection section is configured to detect the set of waves, if the amplitudes of the set of waves are greater than a first predetermined level but the time difference between time points at which the amplitudes exceed the first predetermined level is greater than the predetermined time interval, by checking whether the amplitudes of the set of waves are greater than a second predetermined level greater than the first predetermined level, and the time difference between time points at which the amplitudes exceed the second predetermined level is less than the predetermined interval; and

the determination section is configured to determine the presence of the physical object when the set of waves having the amplitudes greater than the second predetermined level and the time difference is less than the predetermined time interval.

7. The physical object detection system according to claim 4, wherein:

the detection section is configured to detect the set of waves, the time difference of which is less than the predetermined time interval and the sum of the added amplitudes is greater than the predetermined threshold value.

8. The physical object detection system according to claim 5, wherein:

the detection section is configured to detect the set of waves, the time difference of which is less than the predetermined time interval and the coefficient of correlation of which is greater than the predetermined value.

9. The physical object detection system according to claim 7, wherein:

the detection section is configured to apply first and second weights to a detection result of the set of waves having the time difference less than the predetermined time interval and a detection result of the set of waves having the sum of added amplitudes greater than the predetermined threshold value, respectively, the first weight being greater than the second weight.

10. The physical object detection system according to claim 8, wherein:

the detection section is configured to apply first and second weights to a detection result of the set of waves having the time difference less than the predetermined time interval and a detection result of the set of waves having the coefficient of correlation greater than the predetermined value, respectively, the first weight being greater than the second weight.

11. The physical object detection system according to claim 1, wherein:

the time difference corresponds to a difference in distances caused between the receiving elements in respect of distances relative to the physical object.

12. The physical object detection system according to claim 1, wherein:

the detection section is configured to detect the set of waves by comparing a distance difference calculated based on the time difference and a propagation velocity of the transmission wave with a predetermined distance.

13. The physical object detection system according to claim 12, wherein:

the predetermined distance corresponds to a positional interval between the receiving elements.

14. The physical object detection system according to claim 1, further comprising:

a temperature sensor for measuring an ambient temperature,

wherein the transmission wave is an ultrasonic wave, and

wherein the detection section is configured to correct the time difference in accordance with the ambient temperature measured by the temperature sensor.

15. The physical object detection system according to claim 12, further comprising:

a temperature sensor for measuring an ambient temperature,

wherein the transmission wave is an ultrasonic wave, and

wherein the detection section is configured to correct the propagation velocity of the transmission wave in accordance with the ambient temperature measured by the temperature sensor.

16. The physical object detection system according to claim 1, wherein:

the transmitting element, the receiving elements and the electronic unit are mounted on a vehicle.

17. A physical object detection system comprising:

a plurality of ultrasonic sensors arranged at a plurality of locations spaced apart each other horizontally on a longitudinal end part of a vehicle for detecting a physical object by transmitting ultrasonic waves and receiving reflection waves of transmitted ultrasonic waves; and

an indicator device connected to the ultrasonic sensors for indicating presence of the physical object detected by the ultrasonic sensors,

wherein each of the ultrasonic sensors includes;

a transmitting element for transmitting an ultrasonic wave;

a first receiving element for producing a first reception signal upon receiving a reflection wave;

a second receiving element for producing a second reception signal upon receiving the reflection wave; and

a control unit for driving the indicator device, when a time difference between time points, at which the first reception signal and the second reception signal attains a predetermined level, is less than a predetermined time interval.