Vehicle occupant discrimination system and method

• US 6,252,240 B1
• Filed: 04/24/1998
• Issued: 06/26/2001
• Est. Priority Date: 04/25/1997
• Status: Expired due to Fees

• Current Assignee: Automotive Systems Laboratory, Incorporated (Ningbo Junsheng Investment Group Co., Ltd.)
• Original Assignee: Automotive Systems Laboratory, Incorporated (Ningbo Junsheng Investment Group Co., Ltd.)
• Inventors: Farmer, Michael E., Mahbub, Naveed, Stanley, J. Gregory, Campbell, James A., Gillis, Edward J.
• Primary Examiner(s): Le, Que T.
• Assistant Examiner(s): Luu, Thanh X.
• Application Number:
  US09/066,547
• Time in Patent Office: 1,159 Days
• Field of Search: 250/559.38, 250/221, 250/559.4, 280/735, 307/10.1, 701/45, 180/271, 180/272, 180/273, 180/282
• US Class Current: 250/559.38
• CPC Class Codes: B60R 21/01516 using force or pressure sensing means
• CPC Class Codes: B60R 21/01534 using electromagneticwaves, e.g. infrared
• CPC Class Codes: G01G 19/4142 for controlling activation of safety devices, e.g. airbag systems electrical circuits for triggering safety arrangements in case of vehicle accidents B60R21/015

Abstract

An occupant discrimination system incorporates a position sensor for measuring the distance from a fixed structure within the vehicle to a first surface of an occupant or object on a vehicle seat, and a seat weight sensor for measuring the weight of the occupant or object. The position sensor generates a plurality of signal components that are combined with the weight and vehicle speed related measurements so as to form a signal space, from which a plurality of measures are calculated. A plurality of seat occupancy scenarios are defined and the likelihood of each seat occupancy scenario is functionally related to the plurality of measures. For a given measure state, the likelihood of each of the seat occupancy scenarios is calculated, and the most likely scenario is used to govern the control of a safety restraint system.

Claims

1. A system for discriminating the condition of seat occupancy by an object on a vehicle seat and for controlling the activation of a safety restraint system responsive thereto, comprising:

a) a plurality of sensors, each one of said plurality of sensors generating at least one distinct measurement, said plurality of sensors generating a plurality of measurements, wherein said plurality of sensors comprises at least one object position sensor, and said object position sensor is an optical sensor comprising;

i) a collimated optical beam;

ii) a position sensitive detector comprising a distributed photosensitive device; and

iii) a lens for imaging light onto said position sensitive detector from said optical beam reflected from the object, whereby said position sensitive detector generates a plurality of measurements responsive to current signals from the distal ends of said position sensitive detector responsive to light focused on said position sensitive detector at a spot between said distal ends, the location of said focused light is responsive to the position of the object of the vehicle seat;

b) a signal processor operatively coupled to the safety restraint system;

c) a memory within said signal processor;

d) a first plurality of distinct measures, each one of said first plurality of distinct measures dependent upon at least one of said plurality of measurements, wherein said first plurality of distinct measures comprises at least one measure selected from the group consisting of a mean distance to the object, a variance of the distance to the object, a maximum distance to the object, and a mean weight of the object, said first plurality of distinct measures further comprises a slant measure, said slant measure is responsive to a slant transform of an N-point moving average of the sum of said current signals from the distal ends of said position sensitive detector, the value of said transform is compared with a first threshold, and said slant measure comprises the fraction of time for which said value of said transform exceeds said first threshold;

e) a plurality of seat occupancy scenarios, each of one of said plurality of seat occupancy scenarios having an associated a priori probability, said plurality of seat occupancy scenarios having an associated plurality of a priori probabilities; and

f) a plurality of probability distributions, each one of said probability distributions providing the probability of a distinct combination of values of said first plurality of distinct measures for one of said seat occupancy scenarios, whereby said signal processor calculates a first probability of each of said plurality of seat occupancy scenarios, said first probability of each seat occupancy scenario of said plurality of seat occupancy scenarios being dependent upon i) said distinct combination of values of said first plurality of distinct measures, ii) said plurality of a priori probabilities, and iii) said plurality of probability distributions, said signal processor calculates the most likely seat occupancy scenario from said first probability of each of said plurality of seat occupancy scenarios, and the control of said safety restraint system is responsive to said most likely seat occupancy scenario.

2. The system for discriminating the condition of seat occupancy by an object on a vehicle seat and for controlling the activation of a safety restraint system responsive thereto, as recited in claim 1, wherein said plurality of sensors further comprises a sensor selected from the group consisting of a vehicle speed sensor, and a vehicle acceleration sensor, and the calculation of said slant measure does not include measurements made at times when the absolute magnitude of vehicle acceleration exceeds a threshold.

3. The system for discriminating the condition of seat occupancy by an object on a vehicle seat and for controlling the activation of a safety restraint system responsive thereto, as recited in claim 2, wherein said processor detects when said most likely seat occupancy scenario has settled down responsive to the time period since when the amount of change of at least one of said distinct measures last exceeded a threshold, and the calculation of said slant measure does not include measurements made at times when said most likely seat occupancy scenario has not settled down.

4. The system for discriminating the condition of seat occupancy by an object on a vehicle seat and for controlling the activation of a safety restraint system responsive thereto, as recited in claim 1, wherein said processor detects when said most likely seat occupancy scenario has settled down responsive to the time period since the last change in said most likely seat occupancy scenario, and the calculation of said slant measure does not include measurements made at times when said most likely seat occupancy scenario has not settled down.

5. The system for discriminating the condition of seat occupancy by an object on a vehicle seat and for controlling the activation of a safety restraint system responsive thereto, as recited in claim 1, wherein the calculation of said slant measure does not include measurements made at times when said strength of said light from said optical beam reflected from the object onto said position sensitive detector is below a threshold.

6. The system for discriminating the condition of seat occupancy by an object on a vehicle seat and for controlling the activation of a safety restraint system responsive thereto, as recited in claim 1, wherein the calculation of said slant measure does not include measurements made at times when the distance between an object and said occupant sensor is less than a threshold.

7. The system for discriminating the condition of seat occupancy by an object on a vehicle seat and for controlling the activation of a safety restraint system responsive thereto, as recited in claim 1, wherein said plurality of sensors further comprises a vehicle speed sensor, and said first threshold is responsive to a measurement of vehicle speed from said vehicle speed sensor.