Author(s):
Moon Sohk Chae -
Samsung Techwin
A gas turbine engine is a complicated engine featuring combinations of various technologies, making its overall performance very difficult to evaluate. Often, measurement problems preclude performing an exact analysis on an actual engine. As a result, the design and verification of gas turbine engine controller hardware and the controlling algorithm present a challenge.
Developing a proper engine simulator was vital to our ability to verify the safe and reliable functioning of the gas turbine engine controller we were developing. In order to implement a safe and highly perfected engine controller, we had to come up with a method of verifying the controller hardware and its algorithm before they could be integrated with an actual engine.
Our goal was to build a virtual engine (or engine simulator) to enhance the performance of our engine controllers. Instead of a large and cumbersome data acquisition system, we used NI LabVIEW running on a PC along with the small and rugged NI CompactRIO hardware platform for the entire simulation and test environment. The resulting simulated virtual engine system, which inputs and outputs the same physical signals as an actual engine, supplied the optimum solution to verify software and hardware integrity.
By mathematically modeling the gas turbine engine, we were able to calculate the engine performance parameters. We then converted those results into actual physical signals that we input and output to the gas turbine engine controller. Through trial and error, we tested the engine controller hardware and algorithm, improving reliability, reducing debugging (calibration) time, and helping us prevent unanticipated controller malfunctions.
Development History
To develop the controller algorithm, we used NI LabVIEW, the LabVIEW Simulation Interface Toolkit , The MathWorks, Inc. MATLAB® and Simulink® software, and Visual C++ as development tools. The entire design process took just over nine and a half months of one developer’s time – two and a half months for hardware design and implementation; just over three months for LabVIEW programming; three and a half months for debugging and verification; and about 10 days for packaging. We were able to resolve nearly half of the 150 engine controller verification items using the simulated report features. (For comparison, performing verification using only actual engine tests took more than one year.)
System Configuration
The gas turbine engine simulator system configuration includes the virtual engine simulator itself, the gas turbine engine controller, the control algorithm (the application software), and the simulator server. The virtual engine simulator contains the mathematical model required for the engine’s dynamic characteristic calculation, real-time operation execution, state calculation, and output parameter generation. The simulator converts the output parameters into the physical pressure/temperature/RPM signal through an independently designed and implemented signal converter model before outputting them. We achieved real-time operation, I/O, and communication to the simulator server using FPGA programming on an 8-slot NI CompactRIO chassis, which allowed for a signal converter to be fabricated.
The engine controller is the actual hardware that executes engine control. We equipped a high-performance CPU and connected it to the simulator using the engine harness/cable. The control algorithm is the engine’s operational logic and control compensator. (The algorithm is most important aspect of engine control; we needed to program it to meet the application’s exact specifications.) Finally, the simulator server is the computer in charge of the virtual engine simulator’s operation and data storage, as well as the user interface.
Our engine simulator incorporates both FPGA programming and real-time programming on the CompactRIO hardware. We programmed the high-speed filtering and I/O in LabVIEW FPGA and downloaded them to the CompactRIO chassis as FPGAs. We then downloaded the algorithm to the CompactRIO controller for real-time processing.
We started out using the NI cRIO-9102 8-slot, 1M gate chassis, but we replaced it with the cRIO 9104 3M gate chassis after realizing that one million gates was not enough. We also added analog buffer circuitry into the signal converter module, because the externally driven current was only a few mA for the original analog output module, the NI cRIO-9263.
Using the simulator server program, the user can perform such user interface tasks as temporary engine status modification, simulation setting modification, simulation start, pause, and exit, and ultimate engine status setting. The engine status monitoring program informs the user on the application software’s integrity, including engine change display and data storage. The engine status monitoring program required the most development and debugging time during overall system development.
Size and weight limitations of the previous PXI-based system presented some portability difficulties. Also, because the operating system was Windows-based, it was not suitable for applications requiring deterministic operation. CompactRIO is a very attractive platform for developers who need to overcome such limitations and to implement new control or monitoring concepts. The real-time operating system equipped in our new system ensures deterministic operation, and LabVIEW lets us perform FPGA programming, largely reducing the development burden of separating operation and monitoring.
MATLAB and Simulink are trademarks of The MathWorks, Inc.
Author Information:
Moon Sohk Chae
Samsung Techwin
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