Patent Application
20170255724
The present invention generally relates to computer aided engineering design, more particularly to improved methods and systems for performing structural topology design optimization of a product.
Today, computer aided engineering (CAE) has been used for supporting engineers in tasks such as analysis, simulation, design, manufacture, etc. In a conventional engineering design procedure, CAE analysis (e.g., finite element analysis (FEA), finite difference analysis, meshless analysis, computational fluid dynamics (CFD) analysis, modal analysis for reducing noise-vibration-harshness (NVH), etc.) has been employed to evaluate responses (e.g., stresses, displacements, etc.). Using automobile design as an example, a particular version or design of a car is analyzed using FEA to obtain the responses due to certain loading conditions. Engineers will then try to improve the car design by modifying certain parameters or design variables (e.g., thickness of the steel shell, locations of the frames, etc.) based on specific objectives and constraints. Another FEA is conducted to reflect these changes until a “best” design has been achieved. However, this approach generally depends on knowledge of the engineers or based on a trial-and-error method. To solve this problem, a systematic approach (referred to as design optimization) to identify the “best” design is used.
Traditionally, design optimization is performed with a computer system and generally divided into three categories, sizing, shape and topology. Structural topology design optimization is best suited for creating optimal conceptual design in which the user (i.e., engineer, designer, etc.) does not have put too many constraints as to the shape and/or size of the engineering product. However, there are problems associated with structural topology design optimization especially for the topology design optimization of a component of a complex structure (e.g., automobile, airplane, etc.). Non-linear structure responses (e.g., design constraints) of the complex product make the progress of the structural topology design optimization difficult to predict. In particular, at each stage of the topology design optimization, the new candidate design is computed using some arbitrary or ad hoc formula for the relationship between the constraints and design variables. As a result, the structural topology optimization procedure can fail or can be overly expensive.
Furthermore, when topology design optimization used in a highly nonlinear impact event (e.g., vehicle crash), prior approaches cannot take certain vehicle occupant safety criteria into consideration. For example, design of the stiffest structure of vehicle would result in peak force dangerous to the vehicle occupants.
A prior art approach designates part(s) in a vehicle in a vehicle as global design variable(s). Such an approach can result in too stiff a part, which is lethal to the vehicle occupants. The results may be improved by subdividing a design part into a number of smaller design parts. However, it is not practical due to expensive computational power, excessive labor costs, and delay.
Therefore, it would be desirable to have improved methods and systems for performing structural topology design optimization using enhanced global design variables for a product in an impact event.
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.
Methods and systems for performing structural topology design optimization of a product in an impact event using enhanced global design variables are disclosed. According to one aspect of the present invention, a definition of a FEA model of the product's design domain as an initial candidate design along with a design objective, at least one design constraint and initial values of a set of global design variables are received in a computer system having one or more application module installed thereon. Initial values of field design variables are then assigned based on the initial values of the global design variables. Simulated structural responses of the product are obtained by performing a time-marching simulation of the impact event using the FEA model. The simulated structural responses include computed internal energy density (IED) distribution, computed design objectives and constraints. The current candidate design is determined whether it is deemed to be optimal based on predefine criteria. If not, new values of global design variables are computed based on computed design constraints and objectives, A target IED distribution for next candidate design is established. The target IED distribution is defined by the sum of a set of mathematical functions with each function scaled by a corresponding global design variable. The field design variables are then updated using the differences of the target IED distribution and the computed IED distribution. Simulated structural responses are obtained for the current candidate design until the current candidate design is deemed to be optimal.
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.
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:
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.
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. Additionally, the term “optimal design” in this document is intended to indicate a design that meets the design requirements (e.g., goal, objective and constraints) in an iterative optimization design process. Furthermore, the terms “optimal configuration”, “optimal design”, “substantially improved design”, “significantly improved design” and “final design” are used interchangeably throughout this document. Finally, 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.
Embodiments of the present invention are discussed herein with reference to
The mathematical basis of structural topology optimization using global design variables is described below.
Write a function F (either design objective or constraint) as:
F=F(x)=F(x(η))=F(η)
Now the standard optimization problem can be solved as:
Minimize F(η) subject Gi(η))<0.
where:
i represents the i-th design constraint, that is, i=1, . . . , n for n constraints.
Specifically the design objective can be the mass of the structure while G represents the occupant safety.
Referring first to
Process 100 starts, at action 102, by receiving a definition of a finite element analysis (FEA) model of a product's design domain as an initial candidate design along with a design objective, at least one design constraint and initial values of a set of global design variables in a computer system (e.g., computer 600 of
At action 104, a set of field design variables are initialized based on the initial values of the global design variables. In one embodiment, material distribution of the product can be represented the field design variables, for example, the mass density of each finite element of the FEA model is a field design variable.
Next, at action 110, the simulated structural responses of the product are obtained by conducting a time-marching simulation of the impact event using the FEA model of the candidate design in a computer system. The simulated structural responses include computed internal energy density (IED) distribution, computed design objectives and computed design constraints. Another example response that is important for occupant safety in an automobile crash is the impact pulse at the location of the occupant.
Next, at decision 112, the current candidate design is checked to determine whether an optimal design has achieved based on predefined criteria. For example, the change of the current candidate design from the immediately prior candidate design is smaller than a predetermined percentage or value, then the optimization can be declared converged (i.e., decision 112 is true).
If decision 112 is false, process 100 follows the ‘no’ branch to action 114. New values of the global design variables are computed using the computed design objectives and constraints obtained at action 110.
Next, at action 116, a target IED distribution for the next candidate design of the product is established. The target IED distribution is defined by a sum of a number of mathematical functions with each function scaled by a corresponding one of the global design variables.
The IED distribution (either computed using FEA or prescribed using global design variables) is a measure of the structural performance in an impact event. Generally, a stiffer part is obtained by decreasing the target IED Enhanced global design variables therefore effective control the stiffness variation in a structure by controlling the target IED distribution variation
In one embodiment, the set of mathematical functions are polynomial functions. Shown in
IED(X)=A0+A1X+A2X2
where:
IED(X) is the target internal energy density distribution.
X is an arbitrary direction in space.
A0, A1, A2 are a set of global design variables.
In another embodiment, the set of mathematical functions are radial basis functions.
Next, at action 118, the field variables and corresponding FEA model of the next candidate design are updated in accordance with the differences between the target IED distribution and the computed IED distribution. This can be done with known topology optimization techniques.
In a first embodiment, a material distribution of a first example candidate design is shown in
In the second embodiment, a material distribution of a second example candidate design is shown in
Referring back to
Finally, impact pulse 440 shown in
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 600 is shown in
Computer system 600 also includes a main memory 608, preferably random access memory (RAM), and may also include a secondary memory 610. The secondary memory 610 may include, for example, one or more hard disk drives 612 and/or one or more removable storage drives 614, representing a floppy disk drive, a magnetic tape drive, an optical disk drive, etc. The removable storage drive 614 reads from and/or writes to a removable storage unit 618 in a well-known manner. Removable storage unit 618, represents a floppy disk, magnetic tape, optical disk, etc. which is read by and written to by removable storage drive 614. As will be appreciated, the removable storage unit 618 includes a computer usable storage medium having stored therein computer software and/or data.
In alternative embodiments, secondary memory 610 may include other similar means for allowing computer programs or other instructions to be loaded into computer system 600. Such means may include, for example, a removable storage unit 622 and an interface 620. 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 622 and interfaces 620 which allow software and data to be transferred from the removable storage unit 622 to computer system 600. In general, Computer system 600 is controlled and coordinated by operating system (OS) software, which performs tasks such as process scheduling, memory management, networking and I/O services.
There may also be a communications interface 624 connecting to the bus 602. Communications interface 624 allows software and data to be transferred between computer system 600 and external devices. Examples of communications interface 624 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 600 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 624 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 624 handles the address part of each packet so that it gets to the right destination or intercepts packets destined for the computer 600. In this document, the terms “computer program medium” and “computer usable medium” are used to generally refer to media such as removable storage drive 614, and/or a hard disk installed in hard disk drive 612. These computer program products are means for providing software to computer system 600. The invention is directed to such computer program products.
The computer system 600 may also include an input/output (I/0) interface 630, which provides the computer system 600 to access monitor, keyboard, mouse, printer, scanner, plotter, and alike.
Computer programs (also called computer control logic) are stored as application modules 606 in main memory 608 and/or secondary memory 610. Computer programs may also be received via communications interface 624. Such computer programs, when executed, enable the computer system 600 to perform the features of the present invention as discussed herein. In particular, the computer programs, when executed, enable the processor 604 to perform features of the present invention. Accordingly, such computer programs represent controllers of the computer system 600.
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 600 using removable storage drive 614, hard drive 612, or communications interface 624. The application module 606, when executed by the processor 604, causes the processor 604 to perform the functions of the invention as described herein.
The main memory 608 may be loaded with one or more application modules 606 that can be executed by one or more processors 604 with or without a user input through the I/0 interface 630 to achieve desired tasks. In operation, when at least one processor 604 executes one of the application modules 606, the results are computed and stored in the secondary memory 610 (i.e., hard disk drive 612). The status of the CAE analysis or structural design topology optimization (e.g., candidate design at each iteration) is reported to the user via the I/O interface 630 either in a text or in a graphical representation.
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 the examples have been shown and described in two-dimensional (i.e., dimensions “x” and “y”), the present invention does not set such limit, dimensions “x” and “y” can be extended to three-dimensional to achieve the same. 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.
