ViGYAN, Inc. provides services in aeronautics R&D, scientific and engineering software development, and computer technology support. ViGYAN operations include the ViGYAN Low Speed Wind Tunnel. This Wind Tunnel has recently undergone a major renovation of its model support, electronics and data acquisition (DAQ) systems.
Although the DAQ briefly described herein has been applied to the wind tunnel, this is not a necessary requirement. The ViGYAN DAQ system could be implemented in other appropriate environments.
The wind tunnel features a closed-loop control system integrated with the data acquisition system for repeatable, efficient conduct of testing operations. A robust instrumentation and control system wiring and instrumentation design and a LabVIEW-based data acquisition system provides measurement and reduction of tunnel conditions, balance loads and other analog channels. Using virtual instrumentation provided by the LabVIEW environment decreased system development time.
The objective of the Wind Tunnel motion control and DAQ program was to create a graphical user interface to setup the wind tunnel tests, control pitch and yaw drive motors, acquire and reduce test data, display and save test results.
The system reads the balance signals, the instrument voltages, and various pressure and temperature sensors. Twelve analog channels are currently available for use. Each channel utilizes external signal conditioning near its respective signal source to minimize noise and degradation. The program also controls the two stepper motors that are used for pitch and yaw motion control through two motor controllers whose commands are transmitted over serial (RS-422) cables. Two absolute encoders are used to read their positions. The readings of pitch and yaw are input to the program through two digital I/O (DIO) boards. A combination of a NI-DAQ (National Instruments) board, PCI-MIO-16XE-10 and NI-backplane with 5b-series signal conditioning modules is used. This NI-DAQ board offers a data acquisition capability which meets a wide range of applications which could read up to 16 analog input channels, 16-bit resolution per channel, and up to 100k samples/second data rate. Two analog output channels and 8 TTL lines are among other useful features of the DAQ system. The 5b-series signal conditioning modules can be manufactured to accept custom voltage levels, and have mix and match module capability that gives the system flexible signal conditioning potential.
The backplane signal conditioner allows remote signal conditioning. The backplane with the 5b-series modules, the pressure and voltage sensors is installed inside a shielded NEMA box in the test chamber and attached to a 10-ft ground rod for added noise suppression. The outputs of the signal conditioners are connected to the DAQ board using a 10m round shielded cable. This setup allows the signal conditioning to occur relatively near to the signal source and thus minimizes added line noise.
The installed hardware communicates with the system software through the DAQ board, the RS-232 port and the DIO boards. The program also creates a graphical user interface to facilitate the set up tests, reduction of the acquired raw data and its display and storage.
LabVIEW was chosen as the programming tool because it provided a graphical programming environment that allowed rapid development and provides the tools to more easily integrate DAQ boards and RS-232 signals as well as advanced signal processing and analysis tools into the production DAQ system.
Among the requirements of the DAQ and motion control program are to guide the user through the test sequence and make it relatively easy to enter and/or edit test-specific information. The GUI guides the user through the test sequence:
As a precaution the program causes the user to initiate an electrical zero before each tare if it has been more than 4 hours since the most previous zero has been taken. The system allows the user to enter different alpha schedules for tares and wind-on data. The DAQ system allows access to previous test/run set-up information. This provides the capability to re-compute a previous run using this modified information.
Once a run starts the data point is available as soon as is taken and saved.
The model support mechanism allows the model attitude to be varied in the range of from -10 to +90 degrees of pitch and from -20 to +20 degrees of yaw, each accurate to 0.1 degree. It features a closed-loop control system integrated with the data acquisition system for repeatable, efficient conduct of testing operations. This system is part of a control room network with workstations for customers to view, plot, and process data immediately after each run as well as allow access to previous runs, tests, or customer-supplied comparison data. An improved version of the widely-used Data Analysis System (DAS) software, now know as DESL, has also been integrated into the system for use as a plotting and analysis tool. This tool is installed on one of the workstations and has access to each data point as soon as it is taken, thus being able to include that point in any real-time plotting and/or analyses.
Recently, the facility DAQ system has been modified to allow the automatic attitude control in pitch and yaw to be operate in a mode wherein combinations of these two angles are specified in random order while at the same time reducing potential sources of flow hysteresis. These latest modifications were made to accommodate the Modern Design of Experiments (MDOE) type wind tunnel testing. At the present time there is no other wind tunnel facility which has these automatic capabilities. ViGYAN intends to also modify its analysis software to also be more conducive to MDOE testing.
Further information regarding data acquisition services may be obtained from:
Kareny Dominguez
ViGYAN, Inc., 30 Research Drive, Hampton, Virginia 23666-1325, USA, Phone: (757) 865-1400, FAX: (757) 865-8177,
webmaster@vigyan.com
Last update:
Thursday, February 24, 2005 at 01:22:59 PM
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