Wind tunnel controls provide consistent, reliable results

How do you get the wind to repeatedly perform in exactly the same way? Precise controls, of course. Used to evaluate aerodynamics, acoustics, and other performance characteristics of product designs and refinements, wind tunnels must exactly duplicate testing conditions to ensure test results are caused by design changes rather than testing errors.

02/01/1999


How do you get the wind to repeatedly perform in exactly the same way? Precise controls, of course. Used to evaluate aerodynamics, acoustics, and other performance characteristics of product designs and refinements, wind tunnels must exactly duplicate testing conditions to ensure test results are caused by design changes rather than testing errors.

To achieve consistent conditions in the new low-speed wind tunnel (LSWT) at the Korea Aerospace Research Institute (KARI, Taejon, Korea), designer Sverdrup Technology Inc. (Tullahoma, Tenn.) recently enlisted GE Fanuc (Charlottesville, Va.) to manage the tunnel's numerous subsystems. Sverdrup's team used GE Fanuc Series 90-70 programmable logic controllers (PLCs) and Cimplicity human-machine interface (HMI) software in a seamless combination that cut implementation costs, saved months of development time, and will be easy to maintain.

Capable of producing up to 250-mph wind speeds, KARI's wind tunnel can test building and automobile aerodynamics, wind noise, high-speed train aerodynamics, aircraft control surface optimization, low-speed flight characteristics, and engine-aircraft integration. Subsystems control conditions in the LSWT, such as air speed, temperature, air exchange, test-device positioning, support, turntables, external balances, struts, and data collection.

HMI, PLC implementation

Using a time-saving data transfer and object-oriented software, Sverdrup's team implemented the LSWT's integrated Cimplicity HMI in just three weeks. The team edited prebuilt and preconfigured screens, selected appropriate tools, and added text or buttons as needed. An Object Linking and Embedding (OLE) button eased importation of OLE 2.0 objects that Sverdrup could move and size with software-based "handles." Screens and subroutines were then modified to match configurations and test requirements.

"Cimplicity HMI gave us the flexibility we needed, and allowed us to import AutoCad files and annotate them," says John Cook, Sverdrup's manager for systems engineering.

Cimplicity HMI allows one person to operate the LSWT using four screens at a central control station. Algorithms in the Series 90-70 PLC bring the tunnel up to desired air speed and conditions, as well as respond to static and dynamic data from 400 control I/O points, which are 70% digital and 30% analog. More than 1,000 pressure points and 120 high-speed points in the tunnel are sampled for test article information, and logged on a separate data acquisition system.

Though many wind tunnels use distributed control systems (DCSs) or PCs for automation, Mr. Cook says Sverdrup decided a VME-based PLC would be more reliable and economical, and increase uptime and data accuracy. "The components are also available off-the-shelf from local suppliers and the interface uses standard protocols," adds Mr. Cook. "GE and GE Fanuc's representatives in South Korea were also critical because our customer needed local parts and training."

For more information, visit www.controleng.com/info .





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