Real Time Control Systems

Propulsion Control System for NASA White Sands Test Facility

"The first system was used early this year and the PXI worked flawlessly.
We were very excited." Asher Lieberman, NASA

Propulsion Test Data Acquisition and Control Systems (DACS)
Propulsion Test Stands
Propulsion Facts

Fig 1 – NASA PXI Control System

The propulsion control system is built on three computer platforms: an embedded NI PXI –8196 real-time controller, an AlphaServer DS25, and an Intel PC (the PC is off-line during real-time control and is used for system configuration and troubleshooting only). The platforms are running under Phar Lab ETS, VMS, and Windows XP respectively.

The PXI RT controller provides storage, execution and management of test and pre-defined profiles. It also performs read/write operations on I/O modules and reflective memory card within 1ms ±0.25ms of the deterministic control cycles. The response time on control commands from reflective memory is less than 2 ms. All I/O operations are synchronized using a back-plane PXI trigger bus and time stamped by an IRIG B code reader PXI card with a resolution of 1µs. Figure 1 shows the control system under test at TEAM Technologies Inc.

The AlphaServer (VMS) executes various user programs that provide real-time test monitoring and control through the reflective memory network to the PXI controller and I/O modules. The AlphaServer provides control system event logging and generates a test report.

The user interface software runs on a Windows XP PC and provides system and PXI instrumentation configuration as well as loading, remote manual control, and monitoring of test profiles execution. It includes various testing and debugging tools for off-line and real-time PXI instrumentation control and monitoring.

Fig 2 - PXI Instrumentation with cables to I/O cards.