In-flight Simulation Research Articles

한국형 공중 시뮬레이터 항공기 연구

This paper presented here contains development of variable stability system(VSS) control laws for the KIFS (Korean In-Flight Simulator) aircraft to simulate the dynamics of F-16 aircraft. Development of VSS Control law for pitch rate, roll rate, yaw rate simulation for three specified flight conditions using Model Following Technique with rate feedback autopilot for stability provision. The direct lift force controller was also added to the developed VSS control law to simulate the pitch rate and normal g-load simultaneously. The simulation results show high accuracy of F-16 aircraft's pitch, roll, yaw rate and g-load simulation.

Model-based control of the flying helicopter simulator: evaluating and optimizing the feedback controller

The numerical evaluation and optimization of the feedback controller parameters of the model-based control implemented in the flying helicopter simulator is subject of this paper. The German Aerospace Center operates this helicopter as a flying testbed for numerous applications, e.g., pilot assistance and in-flight simulation. Initially, the elements of the model-based control are presented. A genetic algorithm and the Nelder–Mead simplex method used for optimization are described. Two simple objective functions to rate parameter sets in the time domain are presented, and a Simulink® model of the helicopter dynamics and the controller structure are used to find optimized sets. The first function, called “Delta Rating”, consists of a normalized integral of the absolute error between commanded and measured states. The second function incorporates the Delta Rating, but is enhanced by a penalty on overshoots. The controllers found are further evaluated using a frequency domain approach consisting of a weighted sum of the differences in amplitude and phase, also considering the coherence at the corresponding frequency. Apart from the Simulink® model, a ground-based simulator is used to evaluate the standard and the optimized controllers.

Flight Control Experiment of Multipurpose-Aviation-Laboratory-alpha In-Flight Simulator

This paper reports the results of experimental verification of flight controllers for the multipurpose-aviation-laboratory-α (MuPAL-α) in-flight simulator. The flight controller design requirements are twofold: to suppress the effects of gusts on MuPAL-α motions and to realize a wide range of maneuverability, i.e., handling characteristics, without controller redesign. Using a previously proposed two-step design method for two-degrees-of-freedom model-matching controllers, flight controllers were designed for the linearized longitudinal and lateral-directional motions of MuPAL-α, and their performance was examined by hardware-in-the-loop simulations and flight tests with several maneuverability models. These experiments confirmed that MuPAL-α with our controllers achieves gust suppression and is capable of simulating various types of handling characteristics simply by replacing the model that defines the characteristics to be examined.

전환제어법칙 설계 및 검증에 관한 연구

The flight control law designed for prototype aircraft often leads to degraded stability and performance, although developed control law verify by non-real time simulation and pilot based evaluations. Therefore, the proper evaluation methods should be applied such that flight control law designed can be verified in real flight environment. The one proposed in this paper is IFS (In-Flight Simulator). Currently, this system has been implemented into the F-18 HARV (High Angle of Attack Research Vehicle), SU-27 and F-16 VISTA (Variable stability In flight Simulation Test Aircraft) programs. The IFS necessary switching control law such as fader logic and integrator stand-by mode to reduce abrupt transient and minimize the integrator effect for each flight control laws switching. This paper addresses the concept of switching mechanism with fader logic of TFS (Transient Free Switch) and stand-by mode of feedback type based on SSWM (Software Switching Mechanism). And the result of real-time pilot evaluation reveals that the aircraft is stable for inter-conversion of flight control laws and transient response is minimized.

フィードフォワードモデルマッチング制御による操縦特性模擬を実現した MuPAL-α による ILS 進入実験

This paper reports flight controller design for In-Flight Simulator (IFS) MuPAL-α and some experiment results. As IFS MuPAL-α was required to realize handling characteristics of given models using only feedforward controllers, inverse systems were designed as the flight controller for model-matching control. Flight experiments confirmed that MuPAL-α with our controller has a research ability for handling quality investigation.

Piloted Simulation Study Comparing Classical, H-infinity, and Linear Parameter-Varying Control Methods

Piloted simulation is often regarded as an intermediate step between traditional desktop analysis and flight test. It is a valuable tool in the assessment of how changes in flight control system parameters affect closed-loop vehicle performance. This paper focuses on the piloted simulation evaluation of classical proportional-integral-derivative, robust H ∞ , and linear parameter-varying control design methods. Three different controllers are designed for the longitudinal flight dynamics of the F-16 variable stability in-flight simulator test aircraft within a defined flight envelope. After assessing the performance of each controller using the desktop analysis and simulation, a piloted simulation study is provided to gather qualitative pilot ratings and comments to validate or refute the results and conclusions which were based on the preliminary desktop analysis. The pilot-in-the-loop flight simulator, simulation test plan, and controller evaluation procedure are described. The data obtained from a two-pilot simulation test are then used to conduct a full-handling-qualities study comparing the performance and robustness of each controller. The paper concludes with the selection of the controller that is best suited for application to a modern, fighter-type aircraft.

The Effects of Time Delay and Physical Motion on Manual Flight Control: An In-Flight and Ground-Based Simulation Experiment

An experiment addressed the effects of time delay and physical motion on manual flight control and flying qualities ratings. Flight tasks were presented on a head-up display in a variable-stability NT-33A aircraft. Specified maneuvers were performed under simulated instrument meteorological conditions with variable signal delays added to the flight control system. To assess the effects of physical motion, the same experiment was replicated with the airplane parked on the ground using a digital aerodynamic simulation. Increasing time delay degraded tracking performance more in the no-motion ground-based simulation than in the full-motion in-flight simulation. Similar results occurred for flying qualities ratings.

Approach and Landing Flight Evaluation of Smart-Cue and Smart-Gain Concepts

The smart-cue and smart-gain concepts were developed as a means to alleviate pilot―vehicle-system loss of control in the presence of control surface actuator rate limiting. Both concepts exploit the measure of dynamic distortion, that is, the difference between the actual and an ideal aircraft control system response. The concept of dynamic distortion has significantly evolved in work conducted by Systems Technology, Inc., during a two-phase program sponsored by NASA Dryden Flight Research Center. In this work, the distortion of interest results from control surface rate limiting and is quantified by the surface position error, whereas the distortion metric is the position lag. A force feedback cue (the constraining function) and/or a command path gain reduction are created when the position error exceeds the position lag (the alerting function). This paper examines the approach and landing flight-test evaluations conducted using the Calspan Corporation Learjet II In-Flight Simulator. Three test pilots evaluated several smart-cue and smart-gain implementations while performing the precision offset landing task. One of the pilots flew on a calm air day, whereas the other two flew on days with moderate turbulence and significant crosswinds. The clear performance enhancer for all three pilots was the smart-gain, however, the best results for the two pilots who flew under adverse conditions were obtained for the configuration that featured both the smart-cue and smart-gain active. This configuration eliminated the undesirable motions that were encountered in the final centerline correction when only the smart-gain was active.

Robust model-following controller design for LTI systems affected by parametric uncertainties: a design example for aircraft motion

This article addresses the design problem of a robust model-following controller (MFC) which minimises the error between plant controlled output and model output for a linear time-invariant (LTI) plant system affected by parametric uncertainties and an LTI target model. To design such an MFC, a previously proposed MFC scheme, whose applicability has already been demonstrated with flight controller design, is adopted in this article. Our design procedure is as follows: first, a basic MFC is designed using the nominal LTI plant model and the LTI target model while a structured free matrix in the MFC is not assigned; second, model-following performance of the MFC for appropriately defined disturbance input and model input for the parametric uncertain plant model and the LTI target model is minimised using the structured free matrix; and finally, a robust MFC is obtained using the basic MFC and the optimal structured matrix. In the second step, an iterative design method for robust H 2 controllers for LTI parameter-dependent (LTIPD) systems using parameter-dependent Lyapunov functions (PDLFs), which is also proposed in this article, is applied. Two MFCs for the lateral-directional (L/D) motions of a research aircraft, which has been developed for an in-flight simulator, for two different real aircraft models, i.e. a Boeing 747 model and a Lockheed Jetstar model, are designed and their performance is confirmed via numerical simulations and flight tests.

Stabilator Failure Adaptation from Flight Tests of NF-15B Intelligent Flight Control System

Adaptive flight control systems have the potential to be more resilient to extreme changes in airplane behavior. Extreme changes could be a result of a system failure or of damage to the airplane. A direct adaptive neural-network-based flight control system was developed for the National Aeronautics and Space Administration NF-15B Intelligent Flight Control System airplane and subjected to an inflight simulation of a failed (frozen) (unmovable) stabilator. Formation flight handling qualities evaluations were performed with and without neural network adaptation. The results of these flight tests are presented. Comparison with simulation predictions and analysis of the performance of the adaptation system are discussed. The performance of the adaptation system is assessed in terms of its ability to decouple the roll and pitch response and reestablish good onboard model tracking. Flight evaluation with the simulated stabilator failure and adaptation engaged showed that there was generally improvement in the pitch response; however, a tendency for roll pilot-induced oscillation was experienced. A detailed discussion of the cause of the mixed results is presented.

Centrifuge Testing of Fiber-Reinforced Soil Liners for Waste Containment Systems

The objective of this paper is to study the deformation behavior of moist-compacted soil liners with and without inclusion of discrete and randomly distributed fibers for waste containment systems at the onset of nonuniform settlements in a geotechnical centrifuge. First, scaling considerations pertaining to simulation of discretely mixed fibers in a centrifuge are presented. A series of centrifuge tests were carried out by varying aspect ratio and dosage of fibers in a soil liner of 1.2 m thick and compacted at its standard Proctor compaction. Controlled in-flight simulation of nonuniform settlements in a centrifuge was carried out using a trap-door arrangement at 40 g . It was observed that the aspect ratio and fiber content has a significant affect in restraining cracks for a randomly reinforced soil liner at the onset of nonuniform settlements. In addition to centrifuge test results, flexural behavior of soil beams with and without discrete and randomly distributed fibers was evaluated in the laborato...

Simultaneous Realization of Handling and Gust Responses: In-Flight Simulator Controller Design

This paper addresses the design problem of a flight controller for an in-flight simulator, in which the controller is required to realize the gust response and the handling response of the target aircraft simultaneously. A two-degree-of-freedom model-matching controller is proposed to meet this requirement, with feedback and feedforward controllers designed to vary the gust response and handling response characteristics, respectively. The controller is designed in two steps: the feedback controller is first designed via the H ∞ model-matching approach, then the feedforward controller is designed as a filtered right inverse system of the closed-loop system comprising the plant dynamics and the feedback controller. Controllers are designed to enable a research aircraft to simulate the lateral-directional motions of two target aircraft models: a Boeing 747 and a Convair 880M. Hardware-in-the-loop simulations and flight tests with the designed controllers confirm that they achieve the simultaneous realization of gust response and handling response of the target aircraft. Additionally, an in-flight simulator controller for investigating handling qualities for lateral-directional motions is designed, and hardware-in-the-loop simulations and flight tests confirm its applicability to handling-quality investigation.

A Flight Test Evaluation of the Arc Segment Attitude Reference for Use as a Primary Flight Reference in Helmet-Mounted Displays

The objective of this evaluation was to determine if the use of the Arc Segment Attitude Reference (ASAR) symbology in a head-up display (HUD) in place of the legacy climb-dive ladder attitude reference aids in unusual attitude recovery (UAR) piloting tasks as specified in AFM 11–217 for use as a primary flight reference (PFR). Flight tests were conducted at the US Air Force Test Pilot School (TPS), Edwards AFB, California on the NF-16D Variable-stability In-flight Simulator Test Aircraft (VISTA). Five VISTA flight UAR test sorties were flown. The time for the pilot to initiate a recovery was measured in addition to the correctness of the recovery. The flight tests were conducted with the use of the HUD combiner on VISTA to examine three symbology configurations. Each of the symbology configurations, the Mil-Std-1787C HUD, dual-articulated (DA) HUD, and ASAR HUD were evaluated by five pilots for the UAR task. The flight test results revealed the ASAR resulted in faster stick input for correction of UARs then the Mil-Std-1787C HUD. This study along with other supporting research indicates that the configural design properties of the ASAR support the ability of pilots to quickly ascertain aircraft attitude.

HBS-SWMC 환경에서의 전환장치 설계 및 검증에 관한 연구

Although non-real time simulation and pilot based evaluations are available for the development of flight control computer prior to real flight tests, there are still many risky factors. The control law designed for prototype aircraft often leads to degraded performance from the initial design objectives, therefore, the proper evaluation methods should be applied such that flight control law designed can be verified in real flight environment. The one proposed in this paper is IFS(In-Flight Simulator). Currently, this system has been implemented into the F-18 HARV(High Angle of Attack Research Vehicle), SU-27 and F-16 VISTA(Variable stability. In flight Simulation Test Aircraft) programs. This paper addresses the concept of switching mechanism for FLCC(Flight Control Computer)-SWMC(Switching Mechanism Computer) using 1553B communication based on flight control law of advanced supersonic trainer. And, the fader logic of TFS(Transient Free Switch) and stand-by mode of reset '0' type are designed to reduce abrupt transient and minimize the integrator effect in pitch axis control law. It hans been turned out from the pilot evaluation in real time that the aircraft is controllable during the inter-conversion process through the flight control computer, and level 1 handling qualities are guaranteed. In addition, flight safety is maintained with an acceptable transient response during aggressive maneuver performed in severe flight conditions.

Design of a Variable Stability Flight Control System

A design objective for variable stability flight control system is to develop a controller of in-flight simulation capability that forces the aircraft being flown to follow the dynamics of other aircraft. This paper presents a model-following variable stability control system (VSS) for in-flight simulation which consists of feedforward and feedback control laws, the aircraft dynamic model to be simulated, and switching and fader logics to reduce the transient effect between two aircraft dynamics. The separate design techniques for feedforward and feedback control law proposals are based on model matching and augmented linear quadratic (LQ) techniques. The system allows pilots to select and engage VSS mode, and when deselected, the aircraft reverts to the baseline flight control system. Both the baseline flight control laws and VSS control laws are computed continuously during flight. Initialization of the state values are necessary to prevent instability, since VSS control laws have integrators and filters in longitudinal, and lateral/directional axes. This paper demonstrates and validates the effectiveness and quality of VSS with F-16 models embedded in T-50 in-flight simulation aircraft.

Rate-Controlled Lateral-load Pile Tests Using a Robotic Manipulator in Centrifuge

Abstract Robotic manipulators, as a new facility for centrifuge modeling, can provide a platform to carry out complex in-flight simulation of geotechnical problems. In this study, a four-axis robotic manipulator was employed to conduct a series of laterally-loaded pile tests in sand. Four model piles were installed into a sand bed and laterally loaded at different loading rates consecutively without stopping the centrifuge, which accordingly maximized consistency of the soil sample among the tests. Tests in both loose sand and dense sand were conducted. Detailed information of the test devices and procedures of soil sample preparation and load testing is described in this paper. The test results, including horizontal force-displacement curves, bending moment distributions, relationships between lateral resistance and loading rates, and p-y curves derived from the measured bending moment distributions, are presented. In addition, the effects of loading rate and ground surface are discussed based on the test results. It is found that, under the investigated conditions, loading rate has little effect on the horizontal resistance at specified displacements, but has significant effects on the bending moment and soil reaction distributions. The ground surface also has an effect on the behavior of the laterally-loaded piles. A simple modification method is used to consider the effect of ground surface on p-y curves at shallow depths.

FLIGHT TEST OF IN-FLIGHT SIMULATOR CONTROLLER FOR SIMULTANEOUS SIMULATION OF GUST RESPONSE AND HANDLING RESPONSE

This paper presents flight test result of In-Flight Simulator (IFS) controller which simulates gust response as well as handling response. To simulate these two responses simultaneously, we first design a robust feedback controller to simulate gust response via scaled H∞ control, we then design a feedforward controller to simulate handling response via H∞ control. We design two controllers for the lateral-directional motions of a research aircraft for two different target aircraft. Hardware-In-the-Loop (HIL) simulations and flight tests with the designed controllers confirm that the controllers achieve our objective; that is, the controllers simultaneously simulate gust response as well as handling response.

Flight Test of Model-Matching Controllers for Lateral/Directional Motions of In-Flight Simulator MuPAL-.ALPHA.

In this paper, flight controller design for the lateral/direction motions of in-flight simulator MuPAL-α is discussed. For the simultaneous simulation of gust responses and pilot input responses of model aircraft, feedback and feedforward controllers are designed in two steps; feedback controllers for robust model-matching problem are first designed using scaled H∞ control to simulate the gust responses of target aircraft, and then feedforward controllers for H∞ model-matching are designed as right inverse systems to simulate the aircraft responses driven by pilot inputs. In the feedback controller design, we use airspeed in stead of inertial speed which was used in our previous report. After confirming that designed controllers have good model-matching performance with numerical simulations, we conducted hardware-in-the-loop simulations and flight tests. In the flight tests, we confirmed that controllers with air speed feedback have better model-matching performance than controllers with inertial speed feedback, i.e. we have improved the model-matching performance of in-flight simulator MuPAL-α for its lateral/directional motions.

Centrifuge Modeling of Geosynthetic Reinforced Clay Liners of Landfills

Imperviousness of clay liners is essential in landfills in order to safeguard the environment from contamination. To accomplish this task, the behavior of clay liner of landfills with and without reinforcement inclusion has been explored by carrying out controlled in-flight simulation of nonuniform settlements of landfill in a geotechnical centrifuge using a trap-door arrangement. The reinforcement ability of geosynthetic materials such as geogrid is used to control the crack propagation and permeability of clay liner even at large settlement differences. Centrifuge model test results demonstrate a potential of reinforced clay liners to retain its integrity without significant cracking and crack propagation. Test results have shown that a geogrid layer that is placed within the top portion of the clay liner restrains cracking and enhances the sealing efficiency due to soil–geogrid frictional resistance. The adoption of geosynthetic reinforced clay liner (GRCL) provides an ideal solution for enhancing the ...

History of In-Flight Simulationat General Dynamics

General Dynamics‐Advanced Information Systems (GDAIS) (formerly Veridian) has been the primary innovator, developer, and operator of in-flight simulators in the United States, as well as the rest of the world, since 1947. Though other agencies and countries have developed their own in-flight simulators, the focus is on GDAIS accomplishments in this field. In-flight simulation puts the pilot in the real flight environment and has been used in the development of new aircraft, research of flying qualities and flight-control systems, and training of pilots and engineers in these areas. More recent uses have been in the field of display systems and as avionics test beds. Early technologies that led to the development of variable stability aircraft and their earlier applications, are described first, followed by GDAIS’s history in the development and utilization of in-flight simulation, starting in 1949 with the first flight of the F4U-5 and its auxiliary rudder surface, up to the present with the five-degree-of-freedom F-16 Variable Stability In-Flight Simulator and Test Aircraft. Specific case studies are presented that describe the development and distinctive features of each of the GDAIS in-flight simulators and some of the more significant applications of these unique tools are highlighted.