# Patent

## Title
Vehicle occupant weight classification system

## Abstract

A vehicle occupant classification system categorizes vehicle occupants into various classes such as adult, child, infant, etc. to provide variable control for a vehicle restraint system such as an airbag. The classification system utilizes sensors that are installed in various locations in the vehicle. The sensors are used to generate a three-dimensional profile for the vehicle occupant. Various factors can affect the accuracy of this three-dimensional profile. Fuzzy logic is used to reduce some of the inaccuracies by providing multiple decision levels for various stages of the classification. Inaccuracies are also caused by sensors shifting within the system from their original position. This condition creates offset and the system evaluates this offset and generates a correction factor to provide a more accurate three-dimensional profile. Electrically erasable programmable read-only memory is used to reduce complications and inaccuracies associated with seat occupant weight sensors that have mounting configurations that vary depending upon the vehicle.

## Background
RELATED APPLICATIONS
This application is a divisional of Ser. No. 9/900,282 filed on Jul. 6, 2001 U.S. Pat. No. 6,578,870, which claims priority to provisional applications 60/217,579 filed on Jul. 12, 2000, 60/217,580 filed on Jul. 12, 2000, and 60/217,582 filed on Jul. 12, 2000.


BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for classifying vehicle occupants utilizing multiple vehicle sensors to generate a three-dimensional profile.
2. Related Art
Most vehicles include airbags and seatbelt restraint systems that work together to protect the driver and passengers from experiencing serious injuries due to high-speed collisions. It is important to control the deployment force of the airbags based on the size of the driver or the passenger. When an adult is seated on the vehicle seat, the airbag should be deployed in a normal manner. If a small child is sitting on the seat, then the airbag should not be deployed or should be deployed at a significantly lower deployment force. One way to control the airbag deployment is to monitor the weight and position of the seat occupant. The weight information and position information can be used to classify seat occupants into various groups, e.g., adult, child, infant, and occupant close to dashboard, etc., to ultimately control the deployment force of the airbag.
There are many different systems for measuring weight and determining the position of a seat occupant. These systems use sensors placed in various locations within the vehicle to continuously monitor the position and weight of the occupants. For example, a typical vehicle may include load cells mounted within the seat to measure occupant weight and optical sensors mounted to the dashboard to determine the position of the occupant. Information from the sensors is compiled by a central processing unit and the occupant is classified. Airbag deployment is then controlled based on this classification.
Current classification systems typically use a decision tree method for assigning a class to an occupant. The decision tree method offers only a limited number of comparison tests, which can lead to classification inaccuracies. Further, the decision tree method is unable to adapt to accommodate changes within the system as the system operates over time.
Another problem with current classification systems is that classification accuracy is affected by the number and orientation of seat sensors. Each vehicle can have a different mounting requirement for seat sensors. Smaller vehicles with small seats and limited packaging space, often cannot accommodate a preferred number of sensors or a preferred sensor mounting orientation, which can result in inaccuracies. Further, each different sensor mounting configuration requires its own software, which increases system cost.
System inaccuracies are also caused by sensor shifting. Over time, sensors within the vehicle can be shifted from their original locations creating offset. Thus, when there is offset, the classification system is classifying occupants assuming that the sensors are still in their original locations while in practice the sensors are providing measurements from other locations.
Thus, it is desirable to have a method and apparatus for classifying seat occupants that can reduce inaccuracies caused by sensor shifting, variable sensor mounting configurations, and limited decision processes. The method and apparatus should also be able to adapt with system changes over time in addition to overcoming the above referenced deficiencies with prior art systems.
SUMMARY OF THE INVENTION
The subject invention includes a method and apparatus for classifying vehicle occupants utilizing multiple vehicle sensors to generate a three-dimensional profile.
The classification system utilizes sensors that are installed in various locations throughout the vehicle. The sensors transmit data to a central processing unit that generates a three-dimensional profile representative of the vehicle occupant. Fuzzy logic is used to reduce inaccuracies by providing multiple decision levels for various stages of the classification. The central processing unit also reduces inaccuracies caused by offset by utilizing a measuring function to determine the amount of offset and to generate an appropriate correction factor to provide a more accurate three-dimensional profile. Electrically erasable programmable read-only memory (EEPROM) is used to reduce inaccuracies associated with seat occupant weight sensors that have mounting configurations that vary depending upon the vehicle.
The subject invention provides an improved method and apparatus that more accurately classifies vehicle occupants. The classification information is used for vehicle restraint system control. These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representation of a vehicle seat and airbag system incorporating the subject invention.
FIG. 2 is a schematic representation of the subject system.
FIG. 3 is a schematic representation of a seat sensor configuration incorporating the subject invention.



DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT
A vehicle includes a vehicle seat assembly, shown generally at 12 in FIG. 1, and a restraint system including an airbag system 14. The seat assembly 12 is preferably a passenger seat and includes a seat back 16 and a seat bottom 18. A vehicle occupant 20 exerts a force F against the seat bottom 18. The vehicle occupant 20 can be an adult, child, or infant in a car seat.
The airbag system 14 deploys an airbag 24 under certain collision conditions. The deployment force for the airbag 24, shown as deployed in dashed lines in FIG. 1, varies depending upon the type of occupant that is seated on the seat 12. For an adult, the airbag 24 is deployed in a normal manner. If there is child or an infant in a car seat secured to the vehicle seat 12 then the airbag 24 should not be deployed or should be deployed at a significantly lower deployment force. Thus, it is important to be able to classify seat occupants in order to control the various restraint systems.
One way to classify occupants is to monitor and measure the weight force F exerted on the seat bottom 18 and to monitor and determine the position of the occupant within the vehicle. Multiple sensors 26 are mounted throughout the vehicle to determine seat occupant weight and position. Some sensors 26 are preferably mounted within the seat bottom 18 for generating occupant weight signals 28, each representing portions of the occupant weight exerted against each respective seat sensor 26. The signals 28 are transmitted to a central processing unit (CPU) 30 and the combined output from the sensors 26 is used to determine seat occupant weight. This process will be discussed in greater detail below.
Typically, seats used in different vehicles require different sensor mounting configurations. If differing designs of the seat sensor unit are used, the sensor arrangement can be divided into zones. A reference cell can lie in each zone that can be used for compensation of the sensor cells. Maximum flexibility and minimum electrically erasable programmable read-only memory (EEPROM) requirements will be realized in the assignment of the reference cells and the zones of the sensor arrangement to a virtual arrangement of sensor cells. By the use of EEPROM programmable zone coding, each individual zone can be unambiguously assigned to the virtual sensor arrangement. For example, only four (4) bytes of EEPROM will be necessary for four (4) zones with this coding to achieve an unambiguous, yet flexible, assignment. By using this design, it is possible to achieve high system flexibility with only minimum memory requirements. This will be discussed in further detail below.
Other sensors 26 are mounted within the vehicle to determine occupant position. These sensors generate position signals 32 that are transmitted to the CPU 30. The signals 28, 32 are combined to generate a three-dimensional profile that is used to classify the occupant.
The sensors 26 mounted within the vehicle can be any known sensors in the art including contact and/or non-contact sensors. For example, the sensors mounted within the seat are preferably load cells that utilize strain gages. The position sensors can be optical sensors or other similar sensors. The CPU 30 is a standard microprocessing unit the operation of which is well known and will not be discussed in detail. A single CPU 30 can be used to generate the three-dimensional profiles or multiple CPUs 30 working together can be used.
Once seat occupant weight and position is determined, the occupant is classified into one of any of the various predetermined occupant classes, e.g., adult, child, infant, close to airbag deployment area, far from airbag deployment area, etc. Vehicle restraint systems are then controlled based on the classification assigned to the occupant. For example, if the classification indicates that an adult is in the seat 12 then the airbag 24 is deployed in a normal manner. If the classification indicates that a child or infant is the seat occupant then the airbag 24 will not be deployed or will be deployed at a significantly lower deployment force.
Fuzzy logic is used to reduce inaccuracies that result from classification of persons and objects by using one or several measurements from a three-dimensional input profile. Various features will be determined from the input profile, which will have to be combined in a suitable comparison logic unit in order to achieve correct classification of the person. Previously, decision trees were used to compare features. The disadvantage with this method is that it provides only a limited number of comparison tests and cannot be used adaptively.
Instead, the subject invention uses fuzzy logic to provide multiple links that can lead to more precise classifications. Fuzzy logic is a type of logic that recognizes more than simple true and false values. With fuzzy logic, propositions can be represented with degrees of truthfulness and falsehood. Using fuzzy logic results in higher success rates for classifications and results are achieved with significantly less effort and computing time because of the use of a flexible, adaptive fuzzy set.
Classification inaccuracies can also be caused by system offset. Certain calculated features can be reproduced inadequately because of the actual position of the three-dimensional input values with regard to the sensor arrangement, i.e. the actual position of the input values is different than the original sensor arrangement thereby creating offset. However, since this position offset in the system is known, with the help of additional measurements, these features can be affected adaptively in order to improve classification accuracy. A measuring function is used to evaluate the position offset of the input values from the sensor arrangement and at the same time prepares a correction factor in order to adjust the features that have not been calculated adequately. Because an adaptive solution is used, an effect can be made selectively on the respective conditions of the three-dimensional input value, whether there is position offset or not. It is possible to have a gradual effect on the features in contrast to fixed threshold value switching of prior systems. The inverse of this modification can also be controlled using this mechanism. This will be discussed in further detail below.
As discussed above, and as schematically shown in FIG. 2, the system for classifying vehicle occupants includes multiple sensors 26 mounted within a vehicle to generate a plurality of occupant measurement signals 28, 32, which are transmitted to a CPU 30 which generates a three-dimensional profile for occupant classification by using fuzzy logic. The CPU 30 includes a memory unit 34 for storing an information factor for comparison to the three-dimensional profile. The memory unit 34 can be part of the CPU 30 or can be a separate unit associated with the CPU 30 depending upon the application. The CPU 30 generates a correction factor if the three-dimensional profile varies from the information factor by a pre-determined amount. If correction is required, the CPU 30 generates a corrected three-dimensional profile that is used to classify the occupant. If correction is not required, then the CPU 30 uses the original information. The airbag system 14 controls airbag deployment based on this classification.
The information factor that is used for comparison to the three-dimensional profile is based on various data inputs. One part of the information factor includes a predefined or original sensor arrangement with known sensor positions and calibrations. The three-dimensional profile generated by the sensor measurements represents actual sensor position input values. The CPU 30 compares the actual sensor position input values to the predefined sensor arrangement to determine an offset. The measuring function is used to determine the amount of offset and to generate the correction factor to adjust the actual sensor position input values for the corrected three-dimensional profile.
Another part of the information factor is seat sensor mounting configurations. As discussed above, different seats have a different number of seat sensors 26 mounted in any of various mounting configurations. For example, as shown in FIG. 3, a certain number of seat sensors 26 are mounted within a scat bottom 18. The information factor includes a virtual sensor matrix, shown generally at 36 that defines a predetermined maximum or ideal number of virtual weight sensor positions 38. Typically this maximum or ideal number of virtual weight sensor positions 38 is greater than the actual number of sensors 26 mounted within the seat bottom 18.
To permit the use of common system hardware and software for various different seat sensor mounting configurations, the CPU 30 and EEPROM 34 divide the seat sensors 26 into a plurality of zones 40. Any number of zones 40 can be used and four (4) zones are shown in the preferred embodiment of FIG. 3. Each zone 40 covers a subset of the virtual weight sensor positions 38. A reference cell 42 is assigned to each zone 40 for compiling the weight signals 28 from that zone 40 to generate weight zone signals 44 representing data for the respective subset of the virtual weight sensor positions 38. The CPU 30 and EEPROM 34 map each weight zone signal 44 into the virtual sensor matrix 36 such that all of the virtual weight sensor positions 38 are filled. The CPU 30 then determines seat occupant weight based on the virtual sensor matrix 36 to generate the corrected three-dimensional profile.
The method for classifying vehicle occupants is discussed in detail below. First a plurality of sensors 26 are mounted within the vehicle which generate a plurality of occupant measurement signals 28, 32 in response to an occupant or object being present within the vehicle. The three-dimensional profile is determined based on these occupant measurement signals and is compared to an information factor. A correction factor is applied if the three-dimensional profile varies from the information factor by a predetermined amount to generate a corrected three-dimensional profile. The information factor is a compilation of various features and the determination of whether or not to apply a correction factor is dependent upon the specific feature in question. The occupant is then classified based on either the original or corrected three-dimensional profile.
In the preferred embodiment, fuzzy logic is used to classify the occupant. Specifically, fuzzy logic is used to generate the three-dimensional profile, the corrected three-dimensional profile, and occupant classification.
Also in the preferred embodiment, a plurality of weight sensors 26 are installed in the vehicle seat to determine occupant weight. The sensors 26 generate weight signals 28 in response to a weight force F being applied against the seat bottom 18. The information factor includes the virtual sensor matrix 36, which defines a predetermined number of virtual weight sensor positions 38. The weight signals 28 are mapped into the virtual weight sensor positions 38 to determine seat occupant weight as part of the three-dimensional profile. The correction factor is applied if the number of weight sensors 26 is less than the predetermined number of virtual weight sensor positions 38. Applying the correction factor includes dividing the weight sensors 26 into a plurality of zones 40 with each zone 40 defined as covering a subset of the virtual weight sensor positions 38. Each zone 40 is assigned a reference cell 42 for compiling the weight signals 28 from that zone 40 to form a weight zone signal 44 representing data for the subset of the virtual weight sensor positions 38. Each weight zone signal 44 is mapped into the virtual sensor matrix 36 such that all virtual weight sensor positions 38 are filled and seat occupant weight is determined from the virtual sensor matrix 36 for use in generating the corrected three-dimensional profile. The subset of virtual weight sensor positions 38 for each zone 40 includes a greater number of sensor positions than the number of sensors 26 assigned to each zone 40. The CPU 30 and EEPROM 34 work in conjunction to generate the virtual matrix 36, assign zones 40, and map signals into the matrix 36.
Also in the preferred embodiment the three-dimensional profile is based on an actual position of three-dimensional input values while the information factor includes a defined sensor arrangement. The actual position is compared to the defined sensor arrangement to determine if there is offset. A measuring function is used to evaluate the offset and to generate the correction factor to adjust the input values to generate the corrected three-dimensional profile. This allows the same system software to be used for all offset values.
The subject invention provides a method and apparatus for classifying seat occupants that reduces inaccuracies caused by sensor shifting, variable sensor mounting configurations, and limited decision processes. The subject method and apparatus is also able to adapt with system changes over time.
Although a preferred embodiment of this invention has been disclosed, it should be understood that a worker of ordinary skill in the art would recognize many modifications come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.

## Claims

1. A method for determining vehicle occupant characteristics comprising the steps of:
(a) supporting a plurality of sensors in a seat structure; 
(b) generating a signal from each of the sensors in response to an occupant interacting with the seat structure; 
(c) dividing the seat structure into a plurality of zones with each zone including at least one of the sensors; 
(d) assigning at least one reference cell to each zone; 
(e) determining an information factor for the sensors by establishing a virtual sensor matrix; 
(f) comparing the signals from each of the sensors to the information factor; and 
(g) applying a correction factor by compiling the signals from the sensors in each zone into the respective reference cell, generating a zone signal from each reference cell, and mapping the zone signals into the virtual sensor matrix.

2. A method according to claim 1 including determining an original sensor arrangement having known sensor positions for each of the sensors and wherein step (g) further includes using the known sensor positions in each respective zone to determine offset.

3. A method for determining vehicle occupant characteristics comprising the steps of:
(a) supporting a plurality of occupant sensors in a seat structure; 
(b) generating an initial set of occupant signals from the occupant sensors having a predefined sensor arrangement with known sensor calibrated values; 
(c) dividing the seat structure into a plurality of zones with each zone including at least one of the occupant sensors; 
(d) assigning at least one reference cell to each zone, compiling signals from the occupant sensors in each zone into the respective reference cell, and generating a reference cell output from each reference cell; 
(e) determining an information factor for the occupant sensors based on the known sensor calibrated values; 
(f) generating a plurality of operational occupant signals from each occupant sensor over time that correspond to a plurality of different occupant configurations and generating a plurality of three dimensional profiles based on the different occupant configurations; 
(g) comparing the three dimensional profiles to the information factor; and 
(h) applying a correction factor based on reference cell output from each reference cell in step (d) to generate a corrected three dimensional profile if the three-dimensional profile varies from the information factor by a predetermined amount.

4. A method according to claim 3 including the step of defining system offset as the difference between the known sensor calibrated values and the operational occupant signals generated in step (f).

5. A method according to claim 4 wherein the initial set of occupant signals corresponds to at least one predetermined occupant configuration and wherein at least one of the operational occupant signals corresponds to the same predetermined occupant configuration.

6. A method according to claim 5 wherein each of the signals in the initial set of occupant signals for the predetermined occupant configuration has a first signal value based on the known sensor calibrated values, each of the operational occupant signals for the predetermined occupant configuration has a second signal value different than the first signal value, and further defining the system offset as the difference between the first and second signal values.

7. A method according to claim 6 including the steps of determining an offset correction factor for the occupant sensors in each zone based on the system offset and modifying the three dimensional profile by the respective offset correction factor to generate the corrected three dimensional profile.

8. A method according to claim 3 wherein step (d) further includes generating a zone output signal for each zone.

9. A system for determining vehicle occupant characteristics comprising:
a seat bottom divided into a plurality of zones; 
a plurality of sensors mounted within said seat bottom with each zone including at least one sensor wherein each sensor generates a sensor output signal; 
a plurality of reference cells with one reference cell being associated with one zone wherein each of said reference cells compiles the sensor output signals for all of said sensors mounted within said respective zone; 
a control unit for generating a three dimensional profile representing an occupant position wherein said control unit corrects the three dimensional profile based on output from the reference cells.

10. A method according to claim 1 wherein each signal from step (b) forms a first set of occupant signals generated by the occupant applying a load to the seat structure in a first occupant configuration; step (b) further includes determining an initial three dimensional profile from the first set of occupant signals to establish an initial occupant position, and generating a plurality of operational occupant signals from each sensor over time for establishing subsequent three dimensional profiles that correspond to a plurality of different occupant configurations: step (c) further includes combining operational occupant signals from each zone to generate a zone output signal; step (f) further includes comparing each three dimensional profile to the information factor; and step (g) further includes correcting signal output values if the three dimensional profiles vary from the information factor by a predetermined amount.

11. A method according to claim 3 wherein step (b) includes generating the initial set of occupant signals in response to an occupant applying a load to the seat structure; step (c) further includes assigning each of the occupant sensors to a zone with each zone including more than one occupant sensor, and step (g) further includes combining the operational occupant signals in each zone to generate a zone output signal from each zone, mapping each zone output signal into a virtual sensor matrix, and determining occupant weight based on output from the virtual sensor matrix.

12. A system according to claim 9 wherein each zone includes more than one sensor with said sensors generating a first set of occupant signals in response to an occupant load to said seat bottom in a first occupant configuration and wherein said sensors generate a plurality of operational occupant signals over time that correspond to a plurality of different occupant configurations, said control unit determining said three dimensional profile based on said first set of occupant signals, combining said operational occupant signals from each zone to generate a zone output signal, mapping said zone output signal from each zone into a virtual sensor matrix, and correcting the three dimensional profile based on output from the virtual sensor matrix.

13. A method according to claim 1 wherein step (f) further includes combining the signals from each of the sensors to generate a three dimensional profile.

14. A method according to claim 13 including the step of determining seat occupant weight based on output from the virtual sensor matrix.

15. A method according to claim 14 wherein step (g) further includes generating a corrected three dimensional profile based on output from the virtual sensor matrix.

16. A method according to claim 8 wherein step (e) also includes determining the information factor by establishing a virtual sensor matrix defining a predetermined maximum number of occupant sensor positions; and wherein step (h) further includes mapping the zone output signals into the virtual sensor matrix and determining the corrected three dimensional profile based on output from the virtual sensor matrix.

17. A system according to claim 9 including an information factor with a predetermined virtual sensor matrix wherein said control unit maps output from said reference cells into said virtual sensor matrix to correct said three dimensional profile.

18. A system according to claim 17 wherein said virtual sensor matrix defines a maximum number of sensor positions and wherein the number of sensors within said seat bottom is less than said maximum number of sensor positions.

19. A system according to claim 18 wherein said sensors include a predefined sensor arrangement generating predefined calibrated sensor output values and wherein said control unit compares actual sensor values used to generate said three dimensional profiles to said predefined calibrated sensor output values to determine system offset.

20. A system according to claim 19 wherein said control unit generates a correction factor if said offset is greater than a predetermined amount and applies said correction factor to generate a corrected three dimensional profile.