hardware-in-the-loop (hil)

Hardware-In-the-Loop (HIL) is a kind of simulation in which an actual component of a closed-loop control system is tested within computer-based real-time simulation of the rest of the system. In a conventional HIL simulation, the hardware is an Electronic Control Unit (ECU) in which electronic control signals are communicated between the hardware and the software. But, HIL simulation of a mechanical component, within a closed-loop control system, requires additional sensors and actuators named transfer systems. The transfer systems are used to connect the software and hardware parts. The HIL simulation can achieve unstable behavior or inaccurate results due to unwanted time-delay dynamic of the transfer systems. In this paper, a test bench is implemented for the hardware-in-the-loop simulation of the fuel control unit (FCU) of a gas turbine engine. The FCU is an electro-hydraulic actuator of the fuel control system. In a real engine, the FCU contains a miniature gear-type liquid-fuel pump which is driven at a fraction of the engine rotor speed mechanically by gears. In the HIL simulation, the engine is simulated numerically and an electric motor is employed to drive the pump of the FCU. The real-time simulation of the gas turbine engine thermodynamic model is implemented on an industrial personal computer with an input/output board in connection with the electro-hydraulic system. There is time-delay in the forward path of the fuel control system due to the use of flowmeter for measuring the outlet flow rate of the FCU in HIL simulation. According to extensive experimental works, the AC motor’s lag dynamics has no considerable effect on the HIL testing, and the flowmeter is the only additional transfer system of which the dynamic effect needs to be mitigated. The results show instability of the hardware-in-the-loop simulation due to unwanted time-delay of the flowmeter. Therefore, a model-based predictor is designed for time-delay compensation of the flowmeter. The consistency of the experimental real-time simulation and off-line simulation shows the applicability of the presented method for mitigating the effect of unwanted dynamic of the transfer system in the HIL simulation.

In this paper, first the turbofan engine is modeled and then the fuel flow controller is designed based on the Min-Max algorithm. The engine control system is designed as a dual channel, which means two controllers independent of each other but connected to each other. In the Model-in-the-Loop (MIL) test, the controller and the engine model are run on the computer, but for the Hardware-in-the-Loop (HIL) test, the controller is implemented on an Arduino board that connects to the computer model via USB cable. The main purpose of the controller is to comply with engine restrictions, to provide fuel flow based on the pilot's desired trust in the minimum time and no rapid changes in fuel flow. The results of MIL and HIL tests were evaluated for different inputs, which shows that the controller correctly observed the above notes. The only difference between the HIL and MIL test results is the lower speed of the controller in the HIL test.