Abstract:
Systems and methods for numerically creating corresponding 2-D mesh models for a plurality of airbag fabric panels from a 3-D computerized model of a fully-inflated airbag are disclosed. 3-D computerized model comprises a plurality of nodes and a plurality of shell finite elements. Each shell element is categorized as to which one of a plurality of fabric panels that form the airbag it belongs. Each fabric panel occupies a continuous surface area of the airbag. Shell finite elements of a particular fabric panel are unfolded to a 2-D mesh one fabric panel at a time. The total surface area of a particular fabric panel is compared with the total area of the corresponding 2-D model. Adjust the 2-D mesh model until the areas are within a predetermined tolerance. The final “total-area-matched” 2-D mesh model is further orientated to a fabric material coordinate system of warp and weft for determining manufacturability.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to designing of an airbag, which is a vehicle safety device for increasing occupant safety during an automobile collision, more particularly to methods and systems for creating a plurality of two-dimensional mesh models (e.g., finite element analysis model) of fabric panels that form an airbag from a three-dimensional computerized model of the airbag in a fully-inflated configuration. 
       BACKGROUND OF THE INVENTION 
       [0002]    Airbag is made of a plurality of fabric panels stitched together and installed in an automobile to provide an occupant restraint in an automobile collision. Airbag contains a flexible envelope designed to inflate rapidly in a car crash, to prevent vehicle occupants from striking interior objects such as the steering wheel or a window. Modern vehicles may contain multiple airbags in various side and frontal locations of the passenger seating positions and sensors may deploy one or more airbags in an impact zone at variable rates based on the type and severity of impact. 
         [0003]    With advent of computing technologies, airbag is designed using computer aided engineering analysis (e.g., a finite element analysis (FEA) collaborated between two groups of engineers/designers. The first group is responsible for protecting a vehicle occupant when airbag is fully-inflated in an automobile crash, while the second group for manufacturability of airbag. To satisfy these design goals, a three-dimensional fully-inflated geometry of an airbag is used by the first group while the two-dimensional flat geometry of the panels by the second group. 
         [0004]    Since the design flow is from the first group to the second group, it would therefore be desirable to have methods and systems for numerically creating corresponding two-dimensional models of fabric panels from a three-dimensional computerized model of the airbag in a fully-inflated configuration. 
       SUMMARY OF THE INVENTION 
       [0005]    This section is for the purpose of summarizing some aspects of the present invention and to briefly introduce some preferred embodiments. Simplifications or omissions in this section as well as in the abstract and the title herein may be made to avoid obscuring the purpose of the section. Such simplifications or omissions are not intended to limit the scope of the present invention. 
         [0006]    Systems, methods and software product for numerically creating corresponding two-dimensional (2-D) mesh models of a plurality of fabric panels that form an airbag from a three-dimensional (3-D) computerized model of a fully-inflated airbag are disclosed. 
         [0007]    According to one exemplary embodiment of the present invention, a 3-D computerized model (e.g., finite element analysis model, grid model, etc.) of a fully-inflated airbag is defined. The 3-D computerized model comprises a plurality of nodes and a plurality of shell finite elements. Each shell element is designated to one of a plurality of fabric panels that form the airbag it belongs. Each fabric panel occupies a continuous surface area of the airbag. Shell finite elements of a particular fabric panel in respective three-dimensional topologies or geometries are unfolded to a two-dimensional mesh model one fabric panel at a time. The total surface area of a particular fabric panel is compared with the total area of the corresponding 2-D mesh model. Adjust the 2-D mesh model until the areas are within a predetermined tolerance. The final “total-area-matched” 2-D mesh model is further orientated to a fabric material coordinate system of warp and weft for determining manufacturability. 
         [0008]    According to another aspect, the identifier for each shell element (e.g., element number, element label, etc.) is kept the same in the 3-D and 2-D models, while the identifiers for nodes (e.g., node number, node label, etc.) are different in two models. 
         [0009]    According to yet another aspect, the area for airbag vents is included in the unfolding operation originally and then removed from the final 2-D mesh model, whose area matches the surface area of the 3-D model. 
         [0010]    Objects, features, and advantages of the present invention will become apparent upon examining the following detailed description of an embodiment thereof, taken in conjunction with the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    These and other features, aspects, and advantages of the present invention will be better understood with regard to the following description, appended claims, and accompanying drawings as follows: 
           [0012]      FIG. 1  is a flowchart illustrating an exemplary process of creating 2-D mesh models of airbag fabric panels from a fully-inflated 3-D computerized model, according to an embodiment of the present invention 
           [0013]      FIG. 2  is a perspective view showing a 3-D computerized model of the airbag in a fully-inflated configuration according to an embodiment of the present invention; 
           [0014]      FIG. 3  is a diagram showing a scheme of unfolding a 3-D computerized model to a 2-D mesh model, according to an embodiment of the present invention; 
           [0015]      FIGS. 4-5  shows a 2-D mesh models that are unfolded from the 3-D computerized model of  FIG. 2   
           [0016]      FIG. 6  is a diagram showing an exemplary warp and weft definitions to be used in a fabric material coordinate system, according to an embodiment of the present invention; and 
           [0017]      FIG. 7  is a function diagram showing salient components of an exemplary computer, in which one embodiment of the present invention may be implemented. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will become obvious to those skilled in the art that the present invention may be practiced without these specific details. The descriptions and representations herein are the common means used by those experienced or skilled in the art to most effectively convey the substance of their work to others skilled in the art. In other instances, well-known methods, procedures, and components have not been described in detail to avoid unnecessarily obscuring aspects of the present invention. 
         [0019]    Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Further, the order of blocks in process flowcharts or diagrams representing one or more embodiments of the invention do not inherently indicate any particular order nor imply any limitations in the invention. 
         [0020]    Embodiments of the present invention are discussed herein with reference to  FIGS. 1-7 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes as the invention extends beyond these limited embodiments. 
         [0021]      FIG. 1  is a flowchart illustrating an exemplary process  100  of designing an airbag used as a vehicle safety device for increasing occupant safety in an automobile collision, in particular, creating 2-D mesh models of fabric panels of an airbag from a 3-D computerized model of the airbag in fully-inflated configuration, according to an embodiment of the present invention. Process  100  is preferably understood in conjunction with the previous figures and is implemented in software. 
         [0022]    Process  100  starts by receiving a 3-D computerized model (e.g., finite element analysis model) of an airbag in a fully-inflated configuration at step  102 . The 3-D computerized model comprises a plurality of nodes and a plurality of shell finite elements (e.g., quadrilateral element, triangular element, etc.). Since the airbag is made of a plurality of fabric panels, each shell finite element is further designated to one of the fabric panels. In other words, each fabric panel contains a portion of the shell elements of the 3-D computerized model. A perspective view of an exemplary 3-D computerized model  200  of an airbag in its fully-inflated configuration is shown in  FIG. 2 . Airbag  200  is made of three fabric panels  201 ,  202 ,  203  (the third panel  203  is hidden). 
         [0023]    Next, at step  104 , a 2-D mesh model is created for each fabric panel by unfolding those shell finite elements representing the particular fabric panel from a first orientation in the fully-inflated configuration to a second orientation of a flat geometry. The first orientation is defined by a set of node numbers in the 3-D computerized model, while the second orientation is defined by another set of node numbers of the 2-D mesh model. Element identifier (e.g., element number, element label) of each unfolded finite element is retained or remains to be the same. As an example of unfolding operation of a 3-D object to 2-D,  FIG. 3  shows an exemplary 3-D computerized model  302  unfolded to a 2-D mesh model  304 . The 3-D computerized model  302  represents a portion of curved dome structure defined by a set of nodes  312  having a first set of node numbers. The 2-D mesh model  304  represents the flattened 3-D computerized model  302  and defined by another set of nodes  314  having a second set of node numbers. 2-D mesh models  401  and  502  of the fabric panels  201  and  202  are shown in  FIG. 4  and  FIG. 5 , respectively. 
         [0024]    Process  100  moves then to decision  106 , it is determined whether the total area of the 2-D mesh model is within a tolerance when comparing with the total surface area of those shell elements representing the particular fabric panel of the 3-D computerized model. The tolerance is established with known techniques, for example, a percentage of difference defined by user. If “no”, process  100  moves to step  108 , in which the 2-D mesh model is adjusted to match the total surface area. Next, at decision  110 , if there are more panels in the airbag to be unfolded, process  100  moves back to step  104  to repeat the process for another fabric panel. Otherwise, process  100  moves to step  112 , the 2-D mesh models are orientated to respective fabric material coordinate system of warp and weft for determining manufacturability. Finally, at step  114 , the area  408  ( FIG. 4 ) occupied by the airbag vents is removed from corresponding 2-D mesh model before process  100  ends. An exemplary warp  602  and weft  604  definition is shown in  FIG. 6   
         [0025]    According to one aspect, the present invention is directed towards one or more computer systems capable of carrying out the functionality described herein. An example of a computer system  700  is shown in  FIG. 7 . The computer system  700  includes one or more processors, such as processor  704 . The processor  704  is connected to a computer system internal communication bus  702 . Various software embodiments are described in terms of this exemplary computer system. After reading this description, it will become apparent to a person skilled in the relevant art(s) how to implement the invention using other computer systems and/or computer architectures. 
         [0026]    Computer system  700  also includes a main memory  708 , preferably random access memory (RAM), and may also include a secondary memory  710 . The secondary memory  710  may include, for example, one or more hard disk drives  712  and/or one or more removable storage drives  714 , representing a floppy disk drive, a magnetic tape drive, an optical disk drive, etc. The removable storage drive  714  reads from and/or writes to a removable storage unit  718  in a well-known manner. Removable storage unit  718 , represents a floppy disk, magnetic tape, optical disk, etc. which is read by and written to by removable storage drive  714 . As will be appreciated, the removable storage unit  718  includes a computer usable storage medium having stored therein computer software and/or data. 
         [0027]    In alternative embodiments, secondary memory  710  may include other similar means for allowing computer programs or other instructions to be loaded into computer system  700 . Such means may include, for example, a removable storage unit  722  and an interface  720 . Examples of such may include a program cartridge and cartridge interface (such as that found in video game devices), a removable memory chip (such as an Erasable Programmable Read-Only Memory (EPROM), Universal Serial Bus (USB) flash memory, or PROM) and associated socket, and other removable storage units  722  and interfaces  720  which allow software and data to be transferred from the removable storage unit  722  to computer system  700 . In general, Computer system  700  is controlled and coordinated by operating system (OS) software, which performs tasks such as process scheduling, memory management, networking and I/O services. 
         [0028]    There may also be a communications interface  724  connecting to the bus  702 . Communications interface  724  allows software and data to be transferred between computer system  700  and external devices. Examples of communications interface  724  may include a modem, a network interface (such as an Ethernet card), a communications port, a Personal Computer Memory Card International Association (PCMCIA) slot and card, etc. The computer  700  communicates with other computing devices over a data network based on a special set of rules (i.e., a protocol). One of the common protocols is TCP/IP (Transmission Control Protocol/Internet Protocol) commonly used in the Internet. In general, the communication interface  724  manages the assembling of a data file into smaller packets that are transmitted over the data network or reassembles received packets into the original data file. In addition, the communication interface  724  handles the address part of each packet so that it gets to the right destination or intercepts packets destined for the computer  700 . In this document, the terms “computer program medium” and “computer usable medium” are used to generally refer to media such as removable storage drive  714 , and/or a hard disk installed in hard disk drive  712 . These computer program products are means for providing software to computer system  700 . The invention is directed to such computer program products. 
         [0029]    The computer system  700  may also include an input/output (I/O) interface  730 , which provides the computer system  700  to access monitor, keyboard, mouse, printer, scanner, plotter, and alike. 
         [0030]    Computer programs (also called computer control logic) are stored as application modules  706  in main memory  708  and/or secondary memory  710 . Computer programs may also be received via communications interface  724 . Such computer programs, when executed, enable the computer system  700  to perform the features of the present invention as discussed herein. In particular, the computer programs, when executed, enable the processor  704  to perform features of the present invention. Accordingly, such computer programs represent controllers of the computer system  700 . 
         [0031]    In an embodiment where the invention is implemented using software, the software may be stored in a computer program product and loaded into computer system  700  using removable storage drive  714 , hard drive  712 , or communications interface  724 . The application module  706 , when executed by the processor  704 , causes the processor  704  to perform the functions of the invention as described herein. 
         [0032]    The main memory  708  may be loaded with one or more application modules  706  that can be executed by one or more processors  704  with or without a user input through the I/O interface  730  to achieve desired tasks. In operation, when at least one processor  704  executes one of the application modules  706 , the results are computed and stored in the secondary memory  710  (i.e., hard disk drive  712 ). The status of the finite element analysis is reported to the user via the I/O interface  730  either in a text or in a graphical representation. 
         [0033]    In one embodiment, an application module  706  is configured to facilitate the creation of the 2-D mesh models from a 3-D computerized model of a fully-inflated airbag. The application module  706  further allows the 2-D mesh models to be oriented with a fabric material coordinate system. In another embodiment, the application module  706  is configured to facilitate the removal of airbag vent area from the 2-D mesh models. 
         [0034]    Although the present invention has been described with reference to specific embodiments thereof, these embodiments are merely illustrative, and not restrictive of, the present invention. Various modifications or changes to the specifically disclosed exemplary embodiments will be suggested to persons skilled in the art. For example, whereas a particular type of airbag has been shown and described for carrying out one embodiment of the present invention, other types of airbag may be used for accomplishing the same. Further, whereas three fabric panels have been shown and described to form an airbag, other number of panels can be used for accomplishing the same. Finally, 3-D computerized model and 2-D mesh model have been shown and described as examples, models with other mesh densities or shapes can be used for achieving objectives of the present invention. In summary, the scope of the invention should not be restricted to the specific exemplary embodiments disclosed herein, and all modifications that are readily suggested to those of ordinary skill in the art should be included within the spirit and purview of this application and scope of the appended claims.