Occupant position system and method using ultrasonic technology

• US 6,271,762 B1
• Filed: 02/27/1999
• Issued: 08/07/2001
• Est. Priority Date: 02/27/1999
• Status: Expired due to Fees

• Current Assignee: Key Safety Systems, Inc. (Ningbo Junsheng Investment Group Co., Ltd.)
• Original Assignee: Breed Automotive Technology, Inc. (Ningbo Junsheng Investment Group Co., Ltd.)
• Inventors: Burley, Edward, Murad, Mohannad F., Lotito, James C., Mazur, Joseph F., Blackburn, Brian K., Gentry, Scott B.
• Primary Examiner(s): TWEEL JR, JOHN ALEXANDER
• Application Number:
  US09/259,753
• Time in Patent Office: 892 Days
• Field of Search: 340/686.1, 340/667, 340/825.36, 340/825.49, 340/425.5, 340/438, 367/93, 367/94, 367/99, 367/100, 367/904, 280/734, 342/357, 342/450
• US Class Current: 340/686.1
• CPC Class Codes: B60R 21/01526 using piezoelectric elements
• CPC Class Codes: B60R 21/01536 using ultrasonic waves
• CPC Class Codes: B60R 21/01542 detecting passenger motion
• CPC Class Codes: G01S 7/539 using analysis of echo signal for target characterisation; Target signature; Target cross-section

Abstract

An apparatus and method of determining and tracking the position of a main target (an occupant) and secondary targets, comprising the steps of: transmitting a signal T₁, of determinable period toward the location of the occupant, generating and storing a first index of data indicative of the time any received signal exceeds a determinable threshold; separating the data within the first index into definable data groups indicative of individual received signals representing potential targets; determining, in relation to each transmitted signal T₁, a common group time of receipt T_c for each data group; correlating the group time of receipt to the position of the main target and secondary targets occupant.

Claims

1. A method of detecting one or more objects including an occupant of a vehicle and identifiable parts of the occupant, comprising the steps of:

a) transmitting a first pulse having a determinable signature in the direction of an occupant;

b) establishing a received signal threshold;

c) sensing a received signal reflected from an object including a received signal reflected from the targeted occupant;

d) determining when the amplitude of the received signal exceeds the threshold and storing numbered time increments during which the received signal exceeds the threshold;

e) evaluating the stored increments and grouping contemporaneous increments together, each group of increments being indicative of one target which reflected the first pulse;

f) determining a first group of increments, from those grouped in step e, corresponding to the highest numbered increments and correlating same with the position of the torso of the occupant.

2. The method as defined in claim 1 including a step g) of isolating a target other than the torso of the occupant.

3. The method as defined in claim 2 wherein step g) includes identifying a second group of increments having a value less than that of the first group and correlating this second group with a second target that is spaced forward of the torso of the occupant.

4. The method as defined in claim 1 including a step h) of obtaining a first average value of the first group of increments and identifying this first average value with the position of the torso of the occupant.

5. The method as defined in claim 4 including a step i) of obtaining a second average value of the second group of increments and identifying this second average value with the position of the second target.

6. The method as defined in claim 5 including rapidly repeating step a through step i) to obtain subsequent first and second average values corresponding to each newly transmitted signal.

7. The method as defined in claim 6 including a step j) of recomputing the value of the first average value by repeatedly transmitting signals and recomputing the first average value of the received signal until a predetermined number of subsequent compilations of the first average value are substantially equal and then using this compiled first average value as the first average value, that is, as an indication of the position of the torso of the occupant.

8. The method as defined in claim 6 including a step of tracking the position of the occupant'"'"'s torso, wherein this step of tracking includes:

step k) of recomputing the first average value and comparing same to the compiled first average value and

step l) comparing the difference between the first average value in step k) with the compiled average value, then if the difference is less than a predetermined difference, using the average value from step k) as an indication of the new position of the torso of the occupant.

9. The method as defined in claim 3 including a step of determining if any target is within a risk zone, that is, too close to a location of an inflatable air bag, by comparing the first and second average values to a low limit value which corresponds to a minimum safe position between the air bag and the respective target.

10. The method as defined in claim 9 including the step of modifying the performance of the air bag if any target is within the risk zone.

11. The method as defined in claim 1 wherein the received signal threshold is a variable threshold.

12. A method of detecting the position of a main body part of an occupant as being a main target and tracking this main target while other secondary objects are placed partially in front of it, the method comprising the steps of:

A) transmitting an ultrasound pulse of a determinable period toward the occupant, and starting a time counter;

B) capturing the time count generated by the time counter whenever any received signal exceeds a determinable threshold;

C) separating and analyzing the previously captured time counts to determine how many objects are located at different distances and then calculating these different distances;

D) depending upon how many objects were detected, moving a sensing threshold level up or down, to compensate for different reflection factors resulting from different reflection materials, until a reasonable number of objects has been detected;

E) building a history of objects detected at different distances for several transmission periods;

F) analyzing this history to determine the position of the main body as being the most furthest object seen as a result of the history;

G) updating this history after every transmit period and continuing to analyze it to lock onto the position of the main body while ignoring other secondary objects placed in front of it;

H) flagging the system whenever a secondary object is being seen repeatedly within an Automatic Suppression Zone;

I) repeating the process of building and analyzing a history of objects detected any time the system determines that it has lost its main target.