Real-time multi-rate HIL simulation platform for evaluation of a jet engine fuel controller

https://doi.org/10.1016/j.simpat.2010.12.011Get rights and content

Abstract

A new Hardware-In-the-Loop (HIL) platform is developed for testing of a turbojet engine fuel control system using a multi-rate simulation platform. The HIL equipment consists of an industrial PC and a commercial I/O board for jet engine simulation as the controlled process and an Electronic Control Unit (ECU) as the fuel controller. The controlled process consisting of actuator, physical process and sensors is fully simulated in HIL simulation. However, the high resolution signals of some components in the HIL simulation cause the real-time simulation to become difficult due to the need of small time-steps. As a result, the disparity between the jet engine model sampling rate and these high resolution signals requires a multi-rate simulation. In this study, a multi step size simulation is developed using multiple processors. These processors are designed to synchronize the status of the engine model with the control system as well as to convert the raw data of the I/O boards to actual input and output signals in real-time. These features make the HIL equipment more effective and flexible. The HIL environment is proved to be an efficient tool to develop various control functions and to validate the software and hardware of the engine fuel control system.

Introduction

Generally, the construction of aircraft is costly and time consuming. Safety is also a primary issue that one is facing in conducting actual flight tests. Consequently, Hardware-In-the-Loop (HIL) simulation can effectively evaluate the reliability of the overall aircraft system. HIL simulation is characterized by the operation of real components in connection with real-time simulated components. The simulated components are often the processes being controlled and/or sensors and actuators. In particular, the framework can be used to examine the performance of aircraft subsystems and equipments such as flight control system [1], camera hardware [2], fuel cell power [3], electro hydraulic actuators [4] and engine fuel control system [5].

Several studies have been reported for HIL simulation of jet engine control system. Iserman et al. [6] provided an overview of the various kinds of simulation considering of real-time simulators, architectures and the historical development of hardware-in-the-loop simulation. Cheng [7] discussed HIL testing system for the mini-type turbojet engine to study the transient and steady state performance of a conventional digital control regulator for ground start, air start, stopping, automatic acceleration and deceleration, and steady state regulation. The adjusting characteristics of air start and flying along the ballistic trajectory are also evaluated. In [8], HIL simulation system using MATLAB/xPC-target was developed for an electronic throttle idle speed control strategy based on ANFIS. Wang et al. [9] introduced and applied a method of non-fully recovering LQG/LTR to design the aero-engine control system. In order to validate the performance of the designed control system, the HIL simulation system was then designed. Watanabe et al. [10] designed a fuzzy logic controller and tested on a turbojet engine in a simulated environment. The controller was tested in HIL simulation before being used with the real engine.

According to Fathy [11], a common problem in HIL simulation is virtual model stiffness, defined as a large disparity between the characteristic speeds of different components of a virtual model. When the disparity between the fast and slow dynamics in a virtual model cannot be eliminated, it is common to simulate these dynamics separately at different sampling rates. Such multi-rate simulation may take place on one processor via multithreading, but is more often achieved using multiple processors. The HIL literature describes the challenge to the simulation platform due to the high time resolution required for emulating high sampling rates signals of actuators and sensors [12], [13]. The disparity between the jet engine control system components have not been considered for HIL simulation development.

In this paper, a new HIL simulation platform is developed for the evaluation of jet engine ECU performance. In this application, electrical signals including rotor speed encoder and servo valve drive signals are at high sampling rates rather than the engine model sampling rate of simulation. So this system is characterized by a combination of subsystems working at different time scales and with different needs of time resolution. In order to address this issue, the separation of the high resolution signals for the real-time operation from the software requirements has been proposed. This separation can be achieved by introducing a suitable hardware interface to catch and to generate these high resolution switching signals with a high accuracy without the need of reducing the integration time steps of jet engine simulation.

The outline of this paper is organized as follows. In Section 2, a thermodynamic model and the integration method which is proposed for the real-time simulation of single spool turbojet engine is presented. The structure of the min–max algorithm employed in the ECU is illustrated in Section 3. In Section 4, the software and hardware framework for HIL simulation is presented. The interface between the simulation model and hardware consists of some convertors described in Section 5. Finally the results of the simulation with the simulated ECU and actual ECU are compared in Section 6. Some concluding remarks are presented in Section 7.

Section snippets

Turbojet engine real-time model

The process considered is a single spool turbojet engine with a convergent nozzle, without bypass and bleed flow. The assumptions in the model presented here are that, there does not exist any heat transfer between the control volume and in each control volume, the gas is perfectly mixed. These assumptions imply that only two gas states per control volume are necessary to determine the condition there. Jet engine model has been composed of two parts. The first one refers to a system of static

Electronic control unit hardware

What the pilot usually wants to achieve is to get the engine to deliver a certain percentage of the thrust that is available at the current flight conditions. Since thrust itself is not measurable in flight, the relative thrust command given by the PLA (power lever angle) setting must be translated into a command change of a measured variable. The relative thrust corresponds very well to the engine pressure ratio and this parameter can be used for thrust modulation in controller design [17].

In

HIL architecture

The Matlab/Simulink has been selected as the base software used for the Electronic Control Unit (ECU) development. The toolbox of Real-Time Workshop (RTW) can be used to generate the C-code directly from Simulink model. The xPC-target is then selected as a HIL simulation platform which can be employed to make a real-time system with the host PC and target PC. It provides a high-performance host-target prototyping environment to connect with the physical systems, and then execute them in

Transmitter

The aircraft is controlled using three Pulse Width Modulation (PWM) servo motors. The transmitter section uses a specific protocol to send commands to the vehicle over an RS-232 connection. When manual control is enabled, the transmitter sends a constant stream of ASCII packet to the vehicle flight control computer. These packets consist of five pieces of information. These pieces of information include manual control status, engine fuel throttle, aileron angle, elevator angle and a check byte.

Experimental results

The performance of the ECU for the fuel control of the turbojet engine is tested through the HIL system in order to evaluate and improve the controller performance by tuning the gain parameters. The engine is simulated at zero mach number and only the fuel flow rate is varied during the simulation. In order to compare the response of the simulated and the actual ECU responses, the parameters of the controller are the same as those used in the simulation and the same type of step inputs test is

Conclusion

The purpose of this research is to develop a new HIL platform to simulate the dynamics of a turbojet engine for the purpose of ECU rapid control prototyping. The simulator includes an engine model and interfaces for connecting to ECU hardware. The host-target architecture is integrated in the system to provide the capability of rapid controller prototyping for ECU system. To validate the HIL simulator, the real ECU testing dynamics are compared with the simulator dynamics and the differences

References (18)

There are more references available in the full text version of this article.

Cited by (40)

  • Reliability assessment of engine electronic controllers based on Bayesian deep learning and cloud computing

    2021, Chinese Journal of Aeronautics
    Citation Excerpt :

    So, the reliability assessment of EEC plays an important role in the reliability design of aircraft. Moreover, the prediction of the most frequently used reliability index in engineering, Mean Time Between Failures (MTBF), has high potential to reduce the development and material cost and testing time, thus saving the cost of aircraft eventually.3,4 However, there are two challenges that influence the development of reliability assessment work at the design phase.

  • Design and implementation of MPC for turbofan engine control system

    2019, Aerospace Science and Technology
    Citation Excerpt :

    Lu et al. [15] developed an ECU-in-the-loop platform for an aero-engine digital electronic control (DEC) which was composed of MATLAB/RTW for rapid prototyping from the aero-engine modeling to the embedded implementation, VxWorks real-time operating system, xPC Target for simulated aero-engine, and PC/104 embedded computer for the ECU with a processing speed of 800 MHz. Recently, Montazeri et al. [16] constructed a new HIL simulation for testing a single-spool turbojet engine fuel control system using multiple processors for multi-rate simulation. They set up an HIL framework consisting of an industrial PC for the engine model as the plant, commercial I/O board and an ECU with min-max control architecture.

  • Design and implementation of a real-time hardware-in-the-loop testing platform for a dual-rotor tail-sitter unmanned aerial vehicle

    2018, Mechatronics
    Citation Excerpt :

    The HIL testbed in aerospace industry requires further development for application in tail-sitter vehicles, particularly in terms of real-time aerodynamic prediction. In the HIL framework developed for power systems in [18], the Simulink toolbox of Real-Time Workshop was used to accelerate the computation and realise the real-time simulation, and it can also be applied to UAVs. At the same time, the development of high-powered embedded computers and open-source flight controller such as Pixhawk and PX4 [19] is progressing rapidly.

View all citing articles on Scopus
View full text