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When I was a child playing baseball, "scaling up or down" was as easy as choking up on my bat if I was carrying too much stick for my skinny arms, or going back to the dugout to grab Big Nate's Louisville Slugger if I was swinging for the fence. But today, scalability is no longer a trivial adjustment at the plate.
As companies are driven by customer demand to add more features to their industrial machines, the arising complexities can throw curve balls at the engineers trying to solve new design challenges. Scalability is a key consideration as machine requirements evolve, and it should be planned for to accommodate the inevitable feature creep. Consider the benefits of designing for scalability and how to accomplish it, in the context of a labeling and packaging machine for cans of soup.
In simple terms, scalability is defined to be a measure of how well a solution to a problem will still work as the problem changes or becomes more complex. Scalability is a widely used metric when describing machines that process computational intensive tasks, ranging from network routers that have to direct traffic over the web to industrial packaging machines that require complex motion control algorithms.
Scalable design practices help engineers avoid the problem of "boxing yourself into a design". Two benefits of scalability will be discussed in this paper, one benefit that addresses an initial product design, and a second benefit that helps plan for the future.
Benefit 1: Scalability helps accommodate changing design requirements. Precise design requirements aren't known at the outset of most designs. In fact, research has shown that a leading factor for missed deadlines can be attributed to the rework involved in adding changes to a design, or adapting to unforeseen challenges in the original design. In the worst case scenario, this phenomena results in a late-to-market product, as illustrated by T1 in Figure 1 below.
Benefit 2: Scalability promotes the re-use of components and intellectual property (IP). This correlates to the age-old adage of "Don't re-invent the wheel." New product designs that are built in an evolutionary manner (i.e. an iterative design process), can leverage the existing framework of previous designs, whether that's mechanical or electrical subsystems, or both. In Figure 1, notice the scalable product design, denoted in blue, can have shortened design cycle for next generation products, while a design that doesn't scale may take as long as the original product.
Figure 1: Relative Time to Market Comparison of a Scalable Design vs. a Design That Doesn't Scale.
So how can you design for scalability? In addition to focusing on scalability as a design requirement from the outset of the design, it also requires a design approach with the right development tools and components that won't "box you in."
There are two primary considerations when selecting tools and components that can achieve this:
1) Design algorithms with flexible software platforms.
If the embedded developer at your company who developed a system in FORTRAN leaves, who can pick up his code and understand what's going on? High-level graphical tools, such as LabVIEW, are ideal for rapid code development as they are self-documenting and widely understood by any engineer that can understand a block diagram. LabVIEW also allows integration with other design tools, such as SolidWorks, to integrate the mechanical components of a design with the software control algorithms.
2) Deploy smaller subsystems of the machine with off-the-shelf hardware and standard technologies. The advantage of using off-the shelf components, is that it allows your company to invest in "technology roadmaps" as opposed to vendor products that may be proprietary without 3rd party support. An example of an off-the-shelf platform for embedded design is CompactRIO, which combines a real-time processor, FPGA, and I/O modules to perform any of the following: analog and digital measurements, motion control, and communication over standard busses such as Ethernet, Serial, CAN, etc. Machine builders can choose from a wide array of specialized CompactRIO modules due to multi-vendor support, or create custom modules based on an open specification.
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