What Is Systems Engineering in CAD ?
Real designers usually admit that AutoCAD ( coupons and promos are here ) used more for documenting the design than developing it. We need to rethink the design process now that we have all these exotic computer based mechanical design tools. This paper only begins to examine the concept of systems engineering, what it is, what it is not, and explores how such a concept might be used for future designs based on requirements.
As a young designer, fresh out of Rutgers University, with my newly minted BS degree, I worked on a project at Bell Telephone Laboratories designing the hardware and software for the latest electronic switching system. This project involved more than 1200 engineers furiously working toward the delivery of an operational system, within a very tight deadline. We were organized into development teams, each with about 10-12 engineers, and each working on a piece of the overall project. My team was developing a portion of the real time operating system. My little piece was developing the software to scan sensors that detected when each subscriber required dial tone. Obviously, this was just one of many steps required to complete a complex call across the network, all of which would be controlled by duplexed central computers. Periodically we were visited by representatives of the systems
engineering department, a mysterious group that appeared to be the design overlords. I didn’t, at the time, understand why they were so interested in the behavior of my little piece of software. Of course, it turns out that by analyzing all the “little pieces of software” they were able to simulate whether the system would even work at all! It turns out that software design is often developed using systems engineering, often a requirement for DoD work. Of course, software appears to be a two dimensional system, as opposed to mechanical design, which is a multi-dimensional system.
What is it – definition?
Systems Engineering is concerned with the effective design of reliable systems within cost and time constraints. Systems Engineering applies an appropriate combination of theories and tools, carried out through the use of a suitable methodology and a set of system management procedures, to address real world problems that are often of large .
Systems Engineering in CAD
Systems engineering activities vary from requirements definition or specification to the conceptual and functional development of systems. In dealing with the various phases of the system life cycle, the systems engineer’s perspective is different from that of a product engineer or technology developer. Whereas the product engineer deals with details, the systems engineer takes a “top down” perspective dealing with details only as needed to guarantee successful implementation. Whereas the product engineer deals with system internals, the systems engineer also addresses the external view of the system through the system’s interface to other systems, users, and managers. A systems engineer needs a unique perspective on the system and its life cycle.
My design concept
I envision a subsystem where the behavior is specified. A sub-system that can be designed and tested to satisfy that behavior. One where, even if the behavior changes, it can re-configure itself to match the expected behavior. Such behavior can extend beyond design into manufacturing, deployment, and end-of-lifecycle treatment. Today’s systems are quite facile at making geometric changes driven by parameters. But sub-systems are connected using only geometric mating constraints. If these mating constraints change how is the corresponding sub-system to react? For instance, suppose two co- linear shafts connect via a coupling. Suppose one shaft increases in
diameter. How is the coupling or shaft supposed to change? I can envision embedding each connection with knowledge rules that can determine this, BUT such rules only work for predetermined changes! And a rule would have to be written for every connection. Clearly this is impossible. On the other hand, knowing the characteristics of the coupling might enable the system to compute such a change. Yet mechanical systems have no way to describe what happens at each interface.
- Several problems exist in making such a concept operable.
No language exists to clearly define what sub systems do. Consider even the simplistic case of a bolt. We know it has thickness, thread pitch and depth, and material type. But what does it do? How does its performance change as its parameters and characteristics change?
Beside geometry, changes include operational characteristics, geometric sizing and tolerances, external stresses and reactions, motion behavior, etc. These changes are quite complex to describe, in fact, often impossible to describe with a regular language. Think about many systems that can only be described using non-linear charts, such as RPM vs. power output. Is this new? Not really. It is just done manually, if at all.
Who is working on it?
ANSYS – CADOE (behavior and prediction analysis); EDS What would be the benefits? What tools might be needed? Sub-system performance definition language? Considering sub-system interface actions and their interaction
with “connected sub-systems” Analysis Kinematics Predictions tools
About the author
Raymond Kurland is president of TechniCom, Inc, a market research and consulting firm specializing in the mechanical CAD/CAM market. TechniCom’s CAD/CAM Vendor program offers many CAD vendors insight on where the market is and where it is going. Ray authors many papers and reports on the industry and is the editor of the TechniCom eMonthly. If hes not here he can be reached at email@example.com.