OS LIMITATIONS
Nonetheless, the PC still has drawbacks for real-time engineering applications. According to Ludy, the Windows operating system (OS) poses some limitations in measurement and control applications due to its response time. To address real-time applications, therefore, users often must seek solutions other than a standard PC running Windows. Data Translation addresses this problem with its Fulcrum series of data-acquisition boards that have their own on-board processors.
National Instruments' Jenifer Loy agrees that the Windows OS can pose challenges for engineering applications. She explains that while the processing power of a desktop PC can easily acquire and analyze large amounts of data, the framework of a general-purpose OS makes it difficult to execute operations in precise intervals. General-purpose OSs are designed to quickly respond to user inputs like mouse and keyboard entries but aren't designed to execute applications requiring deterministic performance.
Deterministic performance is a critical component of control systems, such as those used to regulate shaker tables. The mathematics of control algorithms are based on a precise time interval (delta t) between input and output operations. If the controller is distracted by, say, a user keystroke and can't complete necessary calculations within the specified delta t, the system will struggle for stability.
Instead, engineers are choosing to implement control systems using real-time OSs. Real-time OSs run on the same type of hardware that's found in desktop PCs. However, the software architecture is developed so that you can achieve deterministic performance. The operating system adheres to a preemptive scheduling mechanism that allows you to specify execution priorities to parts of the system, thereby ensuring that critical sections of code always receive the necessary processor time.
While many test applications can benefit from real-time OSs, the expertise needed to develop applications for this platform has been a barrier to entry for many engineers. With tools such as LabView, engineers are able to develop applications for targets ranging from desktop systems to real-time platforms.
CONNECTIVITY IS KEY
Network connectivity is a critical capability for today's engineering team. Imagine a design team working on a next-generation automobile. Each member of this team is working on a different part of the vehicle, but all parts need to be tested in real-world situations as one complete unit. Therefore, when prototypes undergo crash testing, multiple engineers need immediate access to test data. Engineering analysis tools must be able to easily retrieve networked data and share new results with other members of the team.
Allen Razdow, vice president of products and services for Mathsoft Engineering and Education Inc. sees connectivity—the PC's part in a larger infrastructure—as an important advance in the PC's ever-changing role. Mathsoft's flagship product is the Mathcad calculation and documentation software. Mathcad allows users to calculate, graph, and communicate technical ideas in a unified visual format.
The Mathcad software interface is meant to combine a white board and a word processor and can be thought of as the electronic equivalent of the back of an envelope. The tool produces worksheet-like documents that have live calculations that can be reused with different numbers and engineering units. The tool checks units as engineers go to ensure their consistency. It's worth recalling that the Hubble space telescope was initially out of focus because somewhere along the way, an engineer confused units in a calculation.
When Mathsoft was born in 1985, PCs were relatively new. No longer tethered to the mainframes of yore, engineers had, in their new desktop machines, some measure of personal control. But the circle is closing and PCs, inherently isolated, are being networked to form a larger computing infrastructure. That infrastructure extends far beyond an office, a building, or even a campus to encompass multiple organizations in physical locations around the world.
Calculations are a crucial part of the design process, especially in the early portions of the design cycle when the majority of the project's costs are committed. There are tens of thousands of calculations required in a big project, and too often they're not documented or archived. The PC, in its new wider role in the overall computing infrastructure, can be the central collection point for these many calculations, carefully documenting and archiving them throughout the entire process (see "PCs: A Tool For Technical Communication," p. 56) .
The point of connectivity is driven home by Mathsoft's Mathcad Application Server, which allows engineers to interactively use the Mathcad software over the Web. The tool changes worksheets on the fly into HTML, and the parameters are changed to user-entry fields. With the Application Server, Mathcad is made accessible, enterprise-wide and beyond, to any and all personnel who must use it, even if they don't have Mathcad software on their own PC.
The MathWorks also provides calculation and analysis software for the PC. Its Matlab product, based on a high-level, text-based language, is the foundation for its entire product line. Matlab helps engineers analyze data with visualization and has connectivity to a variety of data sources.
Simulink, another MathWorks product, is a graphical design environment that lets users create models of their systems and then refine them until they're satisfied with the results. The simulation is done in C, and it can generate C code to run on an embedded system for a DSP processor. It can also generate code for an FPGA. |
