Power switching module, priority unit, emergency stop system and part of the manual switching panel

The CompactRIOTM Platform

The National Instruments CompactRIO system combines real-time FPGA technology and offers superior performance in a compact housing for testing and automation tasks. The architecture consists of a reconfigurable I / O FPGA core, which combines the reliability of a dedicated hardware circuit and the performance of a parallel program execution on the chip itself.

In addition, a real-time embedded processor for deterministic and distributed stand-alone operation to an integrated man-machine interface available. Programming with LabVIEW™.

Green Propellant Test Stand

The Green Propellant test stand at the DLR ( German aerospace centre) in Lampoldshausen allows tests on rocket engines with special fuels and fuel combinations, e.g. for Ariane 5. Green Propellants are specific liquid, environmentally friendly and non-toxic fuels. The test stand is enabled to conduct tests with realistic operation conditions: Pressures up to 6MPa and gas temperatures up to 3000°C. Especially the use of liquid oxygen (LOX) as oxidant and methane (LCH4), the favourite fuel for new rocket engines, are explored here.

Task

The test stand is operated by a control room where all control and monitoring signals are collected. Up to 60 digital channels are controlled by one FPGA, e.g. for fuel supply or monitoring sensor and actuators. The signals of the test stand are processed, visualised and stored during operation. PXI FPGA controllers in the control centre (MCC) monitor the performance of the test stand and ensure that all safety functions are available under all circumstances.

In the event of an error of the current control system, two additional independent sub-systems for safety assurance are available: The emergency stop system transforms the test stand into a safe state, the priority unit monitors the test stand signals of the control system. For those systems a real-time system is required which guarantees the programmatic shut-down of the test stand in dependence on the current state. The employed sequences can be be programmed by the customer if needed.

Solution

The control and measurement electronics are situated in five 19“racks with independent and redundant power supplies. The control and monitoring functions are integrated into two of the five racks and consist of four components, three control elements and one intelligent switching module:

  • The Measurement and Control Centre (MCC) was realised by our partner Werum Software and Systems AG and is based on measurement and controlling hardware on a PXI basis.

  • The Manual Switching Panel (MSP) allows direct and manual control of the test stand.

  • The NI CompactRIO™ based Emergency Stop System (ESS) guarantees direct test stand control under all circumstances even in the event of the loss of the control or the watchdog signals.

  • The CompactRIO based Priority Unit (PU) directs the control over the test stand to the individual systems and is in charge of routing the control signals between the control systems – manual, PC or Emergency Stop - .

The use of CompactRIO RealTime technology enables the control of the test stand in every situation without CPU influence. The control of safety-relevant functions via FPGA creates a stable and safe system which meets the criteria of rocket test beds. LabVIEW FPGA offers simple and fast programming for changing requirements by the user.

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