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CHAPTER 162
H. Bruce Bongiorni
SIMULATION-BASED DESIGN
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12.1Nomenclature
-- to be developed --
12.2What is Simulation-based Design?
Simulation-based Design (SBD) is the program name given to a DARPA project to develop an integrated design environment (see Reference 1). A primary goal of this project is to make it practical to create "virtual prototypes" and test them in "synthetic environments". By doing so, the designer could make decisions tradeoffs while getting instantaneous feedback on the consequences of those changes.
12.2.1Virtual Prototypes: the Smart Product Model
The first notion of a virtual prototype was the development of digital mockups in lieu of physical mockups. These were and are visualizations of the product geometry based on features, dimensions, and spatial relations taken from the CAD representation. These representations are typically sparse in that they represent a subset of much of the information that is contained or generated by a CAD system. This is a result of limitations in the speed of rendering the images and constraints in handling the large amounts of data required.
Another type of virtual prototype is one in which the "behaviors" of the product are represented. An example of a behavior is the structural response of a physical object to a given load. As there are many behaviors that are considered by a designer, there are as many different models that are used. For a ship example, for the structural response of a ship’s structure there is the finite element model. But there can also be a computational fluid dynamics model, a radar signature model, a seakeeping model, a model of the cargo handling systems, a fluid system model, an electrical load model, and so on.(see Reference 2)
The virtual prototype is then defined as:
The logical representation of the digital models and data which describe the behaviors of the product in response to environmental inputs.
There is a lot of discussion surrounding the product model, the 3D product model, the product information model, and the "smart" product model. The 3D product model is essentially the 3 dimensional geometry of the product andwhere the product information model usually refers to the set of non-geometric data related to the product. People use "product model" to refer to either the 3D product model, the product information model, or both. For the purpose of our discussion, the product model refers to the superset of data composed by the union of the 3D product model and the product information model.
During the DARPA SBD project the notion of the "smart" product model emerged. This was the product model expanded to include product behaviors. So for the purpose of this discussion, the "smart" product model is a virtual prototype.
12.2.2Synthetic Environments: Simulations
Models are the sets of instructions, constraints, relationships, and data that describe the way that a product will respond to the inputs from the environment. But a model is a static entity, in that there is no time element in the model.
A simulation, on the other hand, is the instantiating of the model in a time domain. That is, when one set of inputs are given to the model, the model responds to those inputs. That set of inputs is a single instance in time. Multiple inputs are discrete steps in the time domain.
Each version of the product model has a corresponding set of inputs. A synthetic environment is then the superset of all of the input sets for the virtual prototype (or smart product model). The synthetic environment can be defined as:
The logical representation of the input sets and data which elicit the behaviors of the product over time.
Summary [Like to have this at end of section or chapter. Or use a different word]
These are key concepts used in the following discussions and seem deceptively simple. As I have said previously, the virtual prototype is the set of all models that describe the behaviors of the product, and thesynthetic environment is the set of all inputs for simulation.
So for simulation-based design all we have to do is build models for all of the behaviors we want to use as a basis for the design, and test those models simultaneously by running all of the simulations at the same time. Right?
12.3Why the Interest in Simulation-based Design (SBD)?
12.3.1Introduction
The race is to the swift
The new economic realities are shifting the focus from low cost, low quality commodity products to best value custom products. This makes the ability to conceive, design, and produce a new, quality product quickly an important business survival strategy.
Introduction
It is essential toWe are starting this class by looking at the business drivers for SBD-related technologies. The interest in integrated design technologies is basically driven by the need to create new products. There are two fundamental business strategy scenarios: being late to a market with a new product, or being first to the market with a new product.
Scenario 1: We need one of those too!
This is the situation where a business's competitor is investing in the development of a new product and may be the first to have it in the market. The first one there gains market share, economies of scale, etc. So typically management will have some competitor intelligence and start up its own product development program.
Being late to develop a product is not always a bad thing. In some cases, the business that blazes the trail spends a large part of its time and resources going down dead ends. There are also many examples of cases where the innovator ultimately did not capitalize on its ability to create new products such as Zerox or Apple and the PC.(Apple?).
So imagine an example where Company A is investing $5,000,000 of current year money over 5 years to create a new product. Assume that the market for that product is expected to be about $20,000,000 per year. Other assumptions are that cost of capital is 10% and that you can expect to have a 50% share of the market when your product launches.
Now imagine Company B has a 1 year lag behind Company A and now will spend the same effort to develop competing product, but must do so in the same time deadline as their competitor. That is, Company B must develop its version of the product in 4 years.
But, it is not good enough to just have your product in the market. Company B wants to have a better product order to gain market share from its competitor. Being late to start development actually helps this situation and can be a powerful strategy. By being late or delaying the decision to develop a product, Company B can avoid some of the costs from dead ends, and/or take advantage of new technologies or changes in the market forecast. So in this example, we'll assume that Company B actually gets 51% of the market because its product better meets the needs the market.
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The cash flows are shown below:
And the cost comparison is shown in the table below:
Company A
Market share / 49%
Cost of Capital / 10%
Expense / $ (5,000,000)
Revenue / $ 39,522,634
Profit / $ 34,522,634
Company B
Market Share / 51%
Cost of Capital / 10%
Expense / $ (5,000,000)
Revenue / $ 41,135,803
Profit / $ 36,135,803
Difference btw B and A / $ 1,613,169
Scenario 2: We need to be first!
The second generalized case is where a company wants to be the first in a market place with a new product. In this situation, the sooner that the business can develop the product the sooner the benefits of the revenue will accrue. Looking at the same conditions as in the first scenario, the second scenario cash flow looks like that below:
We assume a couple of things in scenario 2. First we assume that the product development process for Company B spends the same amount of resources over a shorter period of time than its competitor. Another assumption is that there is no difference in the quality of the products and that the market is equally shared. Consequently, the benefit to company B is advancing the cash flow.
The results are shown in the table below:
Scenario 2: early finish, no change in market share for Company BCompany A
Market share / 50%
Cost of Capital / 10%
Expense / $ (5,000,000)
Revenue / $ 40,329,219
Profit / $ 35,329,219
Company B
Market Share / 50%
Cost of Capital / 10%
Expense / $ (5,000,000)
Revenue / $ 44,362,141
Profit / $ 39,362,141
Difference btw B and A / $ 4,032,922
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Conclusions from the examples
If you compare the examples above, what should be clear is that in neither of the cases does a Company B reduce engineering cost as compared to Company A. The benefit accrues to Company B by the ability to gain market share and revenues, not by reducing the product development expenditure. That's not to say that a business should not be concerned with product development costs. What it does say is that, all things being equal, a business gains the most benefit from its ability to develop products that allow it to gain market share and, consequently, revenue as quickly as possible.
Businesses that think this way are excited about technologies like SBD. SBD technologies can be expensive, SBD processes can be more expensive than traditional design processes. But because so many more alternatives can be considered and tested in a given period of time, SBD changes the product development process so that higher quality products can be developed in a shorter time.
The case studies below are examples of the application of SBD processes and technologies.
Case Study: Chrysler
In the auto industry, the key to survival, let alone dominance, is in the effectiveness of an auto maker's design process. In the 1970's and 80's production processes and quality were improved. In the 90's, auto makers have rethinking their design processes. One of the best examples of this is Chrysler.
In 1988, Chrysler recognized that it needed to replace its K-car line with a new model. Chrysler management looked at their competition, in particular Honda and Toyota. At that time one study conducted by the Harvard Business School estimated that the average Japanese auto company spent 1.7 million engineering hours in 4 years to launch a new model. In contrast, American and European auto makers spent 3 million engineering hours and 5 years to accomplish the same project.
Chrysler has had more than one near death experience, and in 1988, was facing another possible threat to its viability. In response, Chrysler management committed $1.6 billion dollars to developing a new product line. They also committed to revamping the way they did design. By doing so, Chrysler launched its new line in 3.5 years. This line of cars is now selling very well, Chrysler not only is surviving, but thriving.
What did Chrysler do? Among the things that they changed were:
Platform Teams - Chrysler organized the design process around the product. It formed cross-functional groups of engineers who functioned as an autonomous business unit. The teams not only included the designers, but also people from materials and manufacturing.
Digital mockups -Chrysler has used the digital geometry from their CAD systems to review and evaluate styling decisions and manufacturing processes.
Centralized CAD database - This shared information allowed everyone working on the design, including the major suppliers, to have the same reference information.
Variation simulation - Chrysler engineers simulated the stack-up of tolerances in order to determine the fit of body panels. This simulation also allowed establishment of tolerances to account for spring-back during manufacturing.
Structure modeling and simulation - Cab-forward design made structural analysis critical to the development of Chrysler's new car designs. In addition, simulation of performance reduced the need to develop prototype vehicles and physical testing.
Case Study: Boeing
The Boeing 777 is considered a watershed in the use of simulation to reduce construction costs, and concept-to-delivery time. This ability allowed Boeing to delay committing to the design of its new aircraft until its competitors had already done so. By shortening the design time, Boeing was able to better meet needs of their customers with a product that better met the customer's needs in the market place at about the same time as Airbus Industrie.
In 1986, Airbus and McDonnell Douglas were beginning to develop new planes to meet the market for medium range, wide-body airliners. Boeing was caught with nothing in their product line to match the planes their competitors were developing. The McDonnell Douglas MD-11 and its variation, the MD-12, were scheduled for delivery in 1990. The Airbus A330 and its A340 variation were expected to be delivered in 1993.
Boeing's product development cycle was at least 6 years, McDonnell Douglas was about 4 years for the MD-11, and Airbus was on a 7 years. At the time that Boeing finally committed to developing the 777, they were 5 years behind their competition.
Boeing did a number of things to insure that the 777 would gain market share over its competitors. Among them were:
Early involvement of the customers - Before Boeing committed to design features, the first thing they did was talk to their customers. They spent over a year meeting with the 8 major airlines and discussing the things that they needed. What Boeing learned became the features to be incorporated into the 777 and the constraints for the design.
Digital mockups - Boeing typically built 3 sets of full-scale mockups of a new design. The first checked the basic geometry and arrangements, the second incorporated the changes from the first mockup, electrical wiring, and piping systems, the third incorporated the discoveries of the second mockup. Instead of the physical mockups, Boeing decided to use 3 dimensional digital models to coordinate the design of the aircraft systems.
Collaborative design - Boeing integrated the designers and the builders into a design-build team that forced communication and negotiation between disciplines and organizations that, prior to the 777, had never had direct contact.
Case Study: DD-21, 21st Century Destroyer
The marine industry has started to adopt some of the technologies and practices that are becoming common place in commercial industries (Session Readings 6). Much of the interest by the Department of Defense has been due to cutbacks in appropriations, the increasing cost of new acquisitions, and the complexity of new systems.
The DD-21 program is an effort to design and build the Navy's next generation surface combatant vessel. The contract for initial design has recently been let to two consortiums: the first is Bath Iron Works and Lockheed Martin, the second is Ingalls Shipbuilding and Raytheon. Integral to the design process, the Navy has required the extensive use of modeling and simulation in the course of design and evaluation of alternatives.
The requirements include (Session Reading 9):
Product Model - NAVSEA currently uses the Integrated Ship Design Program (ISDP) software for product model definition provided by the NAVSEA CAD2 contract. The long term goal for SC 21 simulation-based acquisition (SBA) will be the inclusion of physics-based behavioral objects being developed by DARPA. The incorporation of behaviors into the product model results in a "smart" product model.
Physics-based Analysis Programs - Some of the SC 21 Office's analysis needs (15-20%) can be met by the adaptation of commercial-off-the-shelf (COTS) analysis programs developed for general engineering use (e.g., structural finite element, pipe network, and power distribution systems analysis). The majority of needs are unique to ship design or warship design (e.g., seakeeping, survivability). For these areas the SC 21 Office will depend upon software developed by NAVSEA, the Navy or other defense activities.
Behavioral Models - Behavior models capture extensive analytical calculations as parametric equations, as in ship maneuvering coefficients and missile flight characteristics.
Visualization - This capability allows "virtual mockups" to be toured and spatial relationships to be visualized to support the functions of design review and evaluation by managers, production staff, and fleet operators.
Simulations - Simulations are the combination of visualization with realistic behaviors. The SC 21 Office will rely heavily on other Navy and defense activities, industry, and academia for identification and integration of required simulation models.
Product Models
We talk about the the 3d product model as if it were something new and improved over two dimensional drawings. The truth be known, 2d drawings of a 3d object were considered to be a major technological advance. In fact, the British Admiralty required that the ship builder submit a scale model of the ship proposed, which showed the arrangements and structural details of the ship. This resulted in some beautifully crafted models that are now on display in the Royal Maritime Museum in London.
Ultimately, this practice was displaced by the use of orthographic drawings. So it is a bit ironic that we are now in an age where we can deliver 3d representations of a ship design that can replace drawings.