Seat belt tension prediction

Abstract

A vehicle seat belt tension prediction restraint actuator control system and method comprises an accelerometer having an output that generates a signal responsive to vertical acceleration of the vehicle, a seat weight force responsive sensor having an output that generates a signal responsive to the force exerted by a mass resting on the seat, and a processor means operatively coupled to the accelerometer and the force responsive sensor for calculating seat belt tension controlling the actuation of a restraint actuator responsive thereto. The processor is provided with a plurality of inputs operatively coupled to the accelerometer output and seat weight sensor output. Suitable programming is provided to instruct In one embodiment, the processor to calculates the average mass resting on the vehicle seat and predictthe s a force that should be exerted on the seat for corresponding to a measured level of vertical acceleration assuming zero belt tension. The processor then compares the controls the actuation of the restraint actuator responsive to a comparison of an actual force measured by the seat weight force responsive sensor with the predicted force to determine seat belt tension thereby obviating the necessity of complex hardware in physical contact with the seat belt system . In another embodiment, the processor controls the actuation of the restraint actuator responsive to a ratio of a measure of seat weight divided by a measure of vertical acceleration and by the average mass.

1. A system for measuring seat belt tension in a vehicle having an airbag control system and a seat, comprising:
 a.)a. an accelerometer rigidly secured to said vehicle in proximity to the seat thereof, said accelerometer having an output signal responsive to the vertical acceleration of said vehicle;  
 b.)b. a seat weight sensor having an output signal responsive to the force exerted by a mass on said seat; and  
 c.)c. a computer processor having first and second inputs, the first input being operatively coupled to the output signal of said accelerometer and the second input being operatively coupled to the output signal of said seat weight sensor, wherein said processor calculates tension in said seat belt by comparing the output signal of said seat weight sensor at discrete time intervals with predicted fluctuations in the force exerted on the seat caused by vertical acceleration acting upon the mass, assuming no seatbelt tension.  
 
     
     
       2. The system of  claim 1  wherein said seat weight sensor comprises a hydrostatic seat weight sensor disposed within the seat. 
     
     
       3. The system of  claim 1  wherein said seat weight sensor comprises a plurality of load cells adapted to be responsive to the force exerted on the seat by said seat belt. 
     
     
       4. The system of  claim 1  wherein said seat weight senor comprises a plurality of force sensitive resistive elements disposed within the seat. 
     
     
       5. The system of  claim 1  wherein said computer processor further comprises an output operatively coupled to said air bag control system for inhibiting said control system upon the calculation of high seat belt tension. 
     
     
       6. The system of  claim 2  wherein said computer processor further comprises an output operatively coupled to said air bag control system for inhibiting an operation thereof upon the calculation of high seat belt tension. 
     
     
       7. The system of  claim 3  wherein said computer processor further comprises an output operatively coupled to said air bag control system for inhibiting an operation thereof upon the calculation of high seat belt tension. 
     
     
       8. The system of  claim 4  wherein said computer processor further comprises an output operatively coupled to said air bag control system for inhibiting an operation thereof upon the calculation of high seat belt tension. 
     
     
       9. A method for predicting seatbelt tension in a vehicle having a seat, an accelerometer rigidly secured to said vehicle in proximity to the seat, said accelerometer having an output signal responsive to a vertical acceleration of said vehicle, a seat weight sensor having an output signal responsive to a force exerted by a mass acting on the seat, and a processor having a first input operatively coupled to the output signal of said accelerometer and a second input operatively coupled to the output signal of said weight sensor comprising:
 a.)a. measuring an actual variation in force due to vertical acceleration exerted on the seat over a predetermined time period;  
 b.)b. calculating an average mass on the seat;  
 c.)c. calculating a predicted variation in force due to vertical acceleration exerted on the seat by multiplying the average mass on the seat by the variation in vertical acceleration over a predetermined time period; and  
 d.)d. dividing the actual variation in force by the predicted variation in force whereby a quotient represents normalized seatbelt tension.  
 
     
     
       10. A method for predicting seatbelt tension in a vehicle having a seat, an accelerometer rigidly secured to said vehicle in proximity to the seat, said accelerometer having an output signal responsive to a vertical acceleration of said vehicle, a seat weight sensor having an output signal responsive to a force exerted by a mass on the seat, and a processor having a first input operatively coupled to the output signal of said accelerometer and a second input operatively coupled to the output signal of said weight sensor comprising:
 a.)a. measuring the force duct to vertical acceleration exerted on the seat at discrete time intervals;  
 b.)b. calculating an average mass on the seat;  
 c.)c. calculating at discrete time intervals a predicted force acting on the seat due to vertical acceleration, assuming the tension in said seat belt is zero; and  
 d.)d. calculating at discrete time intervals a difference between the measured force exerted on the seat and the predicted force whereby the difference is indicative of seats belt tension.  
 
     
     
       11. A method for predicting seatbelt tension in a vehicle having a seat, an accelerometer rigidly secured to said vehicle in proximity to the seat, said accelerometer having an output signal responsive to a vertical acceleration of said vehicle, a seat weight sensor having an output signal responsive to a force exerted by a mass on the seat, and a processor having a first input operatively coupled to the output signal of said accelerometer and a second input operatively coupled to the output signal of said weight sensor comprising:
 a.)a. measuring the force due to vertical acceleration exerted on the seat at discrete time intervals;  
 b.)b. calculating an average mass on the seat;  
 c.)c. measuring the vertical acceleration acting on said vehicle at discrete time intervals;  
 d.)d. calculating at discrete time intervals a predicted force exerted on the seat by multiplying the vertical acceleration at each time interval by the average mass, assuming the tension in said seat belt is zero; and  
 e.)e. calculating at discrete time intervals a ratio between the measured force exerted on the seat and the predicted force exerted on the seat whereby the ratio is indicative of seat belt tension.  
 
     
     
       12. A system for measuring seat belt tension in a vehicle having an airbag control system and a seat, comprising:
   a. an accelerometer rigidly secured to said vehicle in proximity to the seat thereof, said accelerometer having an output signal responsive to the vertical acceleration of said vehicle;        b. a seat weight sensor having an output signal responsive to the force exerted by a mass on said seat; and        c. a processor having first and second inputs, the first input being operatively coupled to the output signal of said accelerometer and the second input being operatively coupled to the output signal of said seat weight sensor, wherein said processor calculates tension in said seat belt responsive to said output signal of said accelerometer and responsive to said output signal of said seat weight sensor.     
     
     
       13. A system for measuring seat belt tension in a vehicle having an airbag control system and a seat as recited in  claim 12 , wherein said seat weight sensor comprises a hydrostatic seat weight sensor disposed within the seat. 
     
     
       14. A system for measuring seat belt tension in a vehicle having an airbag control system and a seat as recited in  claim 12 , wherein said seat weight sensor comprises a plurality of load cells adapted to be responsive to the force exerted on the seat by said seat bell. 
     
     
       15. A system for measuring seat belt tension in a vehicle having an airbag control system and a seat as recited in  claim 12 , wherein said seat weight sensor comprises a plurality of force sensitive resistive elements disposed within the seat. 
     
     
       16. A system for measuring seat belt tension in a vehicle having an airbag control system and a seat as recited in  claim 12 , wherein said processor further comprises an output operatively coupled to said air bag control system for inhibiting the operation thereof upon the calculation of high seat belt tension. 
     
     
       17. A system for controlling the actuation of an air bag in a vehicle, comprising:
   a. an accelerometer operatively coupled to the vehicle, wherein said accelerometer generates a first signal responsive to a vertical acceleration of the vehicle proximate to a seat thereof, wherein said seat is associated with the air bag;        b. a seat weight sensor, wherein said seat weight sensor generates a second signal responsive to a weight on said seat; and        c. a processor operatively coupled to said accelerometer and to said seat weight sensor, wherein said processor is adapted to generate a third signal for controlling the actuation of the air bag, and said third signal is responsive to both said first signal and said second signal.     
     
     
       18. A system for controlling the actuation of an air bag in a vehicle as recited in  claim 17 , wherein said accelerometer is rigidly secured to the vehicle in proximity to said seat. 
     
     
       19. A system for controlling the actuation of an air bag in a vehicle as recited in  claim 17 , wherein said seat weight sensor comprises a hydrostatic seat weight sensor disposed within said seat. 
     
     
       20. A system for controlling the actuation of an air bag in a vehicle as recited in  claim 17 , wherein said seat weight sensor comprises a plurality of load cells adapted to be responsive to the force exerted on said seat by a seat belt associated therewith. 
     
     
       21. A system for controlling the actuation of an air bag in a vehicle as recited in  claim 17 , wherein said seat weight sensor comprises a plurality of force sensitive resistive elements disposed within said seat. 
     
     
       22. A method of controlling the actuation of an air bag in a vehicle, comprising:
   a. measuring a vertical acceleration of the vehicle proximate to a location of a seat, wherein said seat is associated with the air bag;        b. measuring a weight upon said seat of the vehicle; and        c. controlling the actuation of the air bag responsive to said operations of measuring said vertical acceleration and measuring said weight.     
     
     
       23. A method of controlling the actuation of an air bag in a vehicle as recited in  claim 22 , wherein the operation of controlling the actuation of the air bag responsive to said operations of measuring said vertical acceleration and measuring said weight comprises:
   a. determining an average mass on said seat from at least one weight measure, wherein said at least one weight measure is generated by the operation of measuring said weight upon said seat;        b. determining a first variation of a plurality of said weight measures within a time period;        c. determining a second variation of a plurality of vertical acceleration measures within said time period, wherein said plurality of vertical acceleration measures are generated by the operation of measuring said vertical acceleration of the vehicle proximate to a location of said seat; and        d. determining a quotient responsive to a division of said first variation by said second variation and by said average mass, wherein the operation of controlling the actuation of the air bag is responsive to said quotient.     
     
     
       24. A method of controlling the actuation of an air bag in a vehicle as recited in  claim 23 , wherein the actuation of the air bag is inhibited if said quotient is less than a threshold. 
     
     
       25. A method of controlling the actuation of an air bag in a vehicle as recited in  claim 22 , wherein the operation of controlling the actuation of the air bag responsive to said operations of measuring said vertical acceleration and measuring said weight comprises:
   a. determining an average mass on said seat from at least one weight measure, wherein said at least one weight measure is generated by the operation of measuring said weight upon said seat;        b. determining said weight measure at discrete time intervals,        c. determining a vertical acceleration measure at said discrete time intervals, wherein said vertical acceleration measure is generated by the operation of measuring said vertical acceleration of the vehicle proximate to a location of said seat; and        d. determining a difference between said weight measure and a product of said average mass and said vertical acceleration measure, wherein the operation of controlling the actuation of the air bag is responsive to said difference.     
     
     
       26. A method of controlling the actuation of an air bag in a vehicle as recited in  claim 25 , wherein the actuation of the air bag is inhibited if the magnitude of said difference is greater than a threshold. 
     
     
       27. A method of controlling the actuation of an air bag in a vehicle as recited in  claim 22 , wherein the operation of controlling the actuation of the air bag responsive to said operations of measuring said vertical acceleration and measuring said weight comprises:
   a. determining an average mass on said seat from at least one weight measure, wherein said at least one weight measure is generated by the operation of measuring said weight upon said seat;        b. determining said weight measure at discrete time intervals;        c. determining a vertical acceleration measure at said discrete time intervals, wherein said vertical acceleration measure is generated by the operation of measuring said vertical acceleration of the vehicle proximate to a location of said seat; and        d. determining a quotient responsive to a division of said weight measure by said vertical acceleration measure and by said average mass, wherein the operation of controlling the actuation of the air bag is responsive to said quotient.     
     
     
       28. A method of controlling the actuation of an air bag in the vehicle as recited in  claim 27 , wherein the actuation of the air bag is inhibited if said quotient is less than a threshold.