Chang-Joo Kim

Konkuk University | KU · Department of Aerospace Information Engineering

Extensive research has been conducted on mission autonomy for multiple aircraft and air mobility operations because of the increasing demand for developing manned-unmanned teaming. Besides a few studies, research focusing on real terrain environments and non-linear dynamics for multiple large unmanned aircraft operations for high-speed maneuvers re...

As the demand of designing the complex configuration like compound rotorcraft or tilt-rotor rotorcraft increased, prediction of performances for those complex configurations is important. Therefore, performance analysis for propeller or rotor-driven aircraft/rotorcraft has been performed to estimate the performance of several rotorcraft configurati...

This paper treats the approach to safe emergency landing for an autonomous rotorcraft in 3-dimensional terrain environments. The autorotation flight that the rotorcraft flies without the power supply is dangerous and needs the high-skilled control ability of the pilot. Ordinary, this flight is divided into three phases: Entry, Steady-Descent, and F...

An autonomous flight system is essential for effective mission performance of UAVs, which are increasingly being applied in civil and military missions. Thus, in this study, an effective approach for implementing guidance and flight control systems is proposed. Based on the rapidly-exploring random tree (RRT) algorithm, the bidirectional potential...

In most extant flight trajectory tracking control schemes, such as sliding mode control, gain parameter selection is time-consuming owing to the lack of explicit methods or rationales for the selection. Therefore, we herein propose a simple and efficient parameter selection method for sliding mode control. To demonstrate the effectiveness of the pr...

This paper investigates an adaptive backstepping control based on the immersion-and-invariance (I&I) method for a rotorcraft’s trajectory-tracking control problem. To effectively cope with both parametric uncertainties and external disturbances affecting all forces and moments of a rotorcraft, the I&I-based disturbance observer is designed and comb...

This study proposes a novel algorithm to accurately predict the angular acceleration required for incremental nonlinear control design. To this end, the angular acceleration of the body as well as the Euler angles provided by the navigation system are used to interpolate the attitude trajectories using a Hermite-spline polynomial. By differentiatin...

Herein, the integrated design process of guidance and control systems required for the design of autonomous flight systems for aircraft is discussed. The system can generate a trajectory using real-time path planning, re-plan the path, and accurately track the created trajectory. The real-time path planning is implemented using a rapidly-exploring...

Recently, interest in mission autonomy related to Unmanned Combat Aerial Vehicles(UCAVs) for performing highly dangerous Air-to-Surface Missions(ASMs) has been increasing. Regarding autonomous mission planners, studies currently being conducted in this field have been mainly focused on creating a path from a macroscopic 2D environment to a dense ta...

This paper treats a robust adaptive trajectory-tracking control design for a rotorcraft using a high-fidelity math model subject to model uncertainties. In order to control the nonlinear rotorcraft model which shows strong inter-axis coupling and high nonlinearity, incremental backstepping approach with state-dependent control effectiveness matrix...

Integrating multiple features for autonomous flight of aircraft requires extensive research over wide categories, high-level of know-how, and experiences. To contribute to these issues, this paper treats the realizable integration techniques of the path planning, trajectory generation, and trajectory-tracking control for the mission autonomy of the...

This paper investigates the adaptive incremental backstepping sliding mode control for the rotorcraft trajectory-tracking control problem to enhance the robustness to the matched uncertainty in the model. First, the incremental dynamics is used for the control design to exclude the adverse effect of the mismatched model uncertainties on the traject...

This paper proposes a new approach to the carrot-chasing guidance law to provide an accurate trajectory-tracking function. The ahead-distance approach used in the conventional method highly depends on trajectory shapes and the complex geometric manipulation causes degraded performance. To overcome this disadvantage, the ahead-distance is replaced w...

This study presents the unified high-fidelity flight dynamic modeling technique for compound aircraft. The existing flight dynamic modeling technique is absolutely depended on the experimental data measured by wind tunnel. It means that the existing flight dynamic model cannot be used for analyzing a new configuration aircraft. The flight dynamic m...

This paper proposes a new direct method for an efficient trajectory optimization using the point that the dynamics of a deterministic system are uniquely determined by initial states and controls imposed over the time horizon of interest. To effectively implement this concept, the Hermite spline is adopted to interpolate the continuous controls and...

Complex and unsteady flow patterns occur around rotating rotor blades owing to the generation of shock waves at the blade tip and interference between the blade and tip wake when the blade rotates at high speeds, thereby resulting in specific noise characteristics. Furthermore, these noise characteristics cause noise pollution in private areas and...

This paper treats numerical methods for an efficient prediction of the rotorcraft emergency procedures after engine failures. The analytical means of compliance for the Category-A requirements can be used for the type certification of the transport-category rotorcraft when their fidelities are approved by the civil airworthiness authority. However,...

This paper intends to compare the effect of the attitude parameterization method on the performance of the attitude controller designed with the direct feedback of corresponding attitude states. To achieve this, the proportional-derivative controllers using the finite rotation angles and the modified Rodrigues parameters are designed with the same...

An inverse-simulation problem is reformulated to exactly satisfy the kinematic constraints imposed by the prescribed trajectory. Thereby, the problem can be transformed into an index 1 differential–algebraic equation that is much more easily solvable than the higher index system of the conventional formulation. Various numerical methods which have...

This paper intends to propose the integrated design framework of a model-following controller (MFC) combined with both an adaptive neural network (ANN) and a linear observer to enhance the handling qualities (HQ) of a fixed-wing aircraft. To achieve this objective, the HQ requirements (HQRs) applicable to a light sports aircraft and the controller...

This study develops the real-time maneuver library generation technique for performing aggressive maneuvers of fixed-wing aircraft. Firstly, the general maneuver libraries are defined, and then 7th-order polynomials are used to create the maneuver libraries. The attitude command attitude hold (ACAH) system, the rate command rate hold (RCRH) system,...

This paper describes the evaluation of the inner-loop controller of the flight control system for the unmanned compound rotorcraft. In order to design the flight control system, the model-following control technique is applied by using the linear model of GEN-ATLAS. This technique is robust to model uncertainty and external disturbance, so it is ap...

This study creates and combines the general maneuver libraries for fixed-wing aircraft to implement tactical maneuvers. First, the generalized maneuver libraries are established by analyzing the characteristics of tactical maneuvers required in battlefields. The 7th order polynomial is applied to both the creation of the maneuver libraries and the...

This paper intends to propose new inverse simulation techniques to cope with the numerical stability and accuracy problems frequently encountered with the integration inverse simulation methods widely used today. To achieve this, the pseudo-spectral method is adopted as a time integrator of the aircraft motion equations. In addition, the quasi-Newt...

In this paper, we have studied on the flight path generation using polynomial and the flight path tracking control using guidance law, speed hold system, ACAH (Attitude Command Attitude Hold) system. The modeling section of the flight path is divided into five regions, and each region is modeled by a 7th order polynomial. The flight paths were defi...

In this paper, the flight characteristics of the Korea Light Aircraft-100 (KLA-100) are evaluated based on the Korean Airworthiness Standards through optimal-flight-path-generation techniques. A flight-dynamics model is developed by using component-based modeling techniques, where a wake model is adopted to examine the propeller effects on the aero...

The best active twist schedules exploiting various waveform types are sought taking advantage of the global search algorithm for the reduction of hub vibration and/or power required of a rotor in high-speed conditions. The active twist schedules include two non-harmonic inputs formed based on segmented step functions as well as the simple harmonic...

This paper intends to develop the rotor track and balance (RTB) algorithm using the nonlinear RTB models and a real-coded hybrid genetic algorithm. The RTB response data computed using the trim solutions with variation of the adjustment parameters have been used to build nonlinear RTB models based on the quadratic interpolation functions. Nonlinear...

This paper deals with the implementation techniques of an implicit integrator to achieve fast and accurate analyses of spacecraft dynamics. For this purpose, the pseudospectral method is adopted to directly integrate the second-order system of equations for both the spacecraft dynamics and corresponding state transition matrix. Various implementati...

The rapid prototyping process and development tool which enable the control law evaluation efficiently are needed to minimize the development cycle, cost and risk of aircraft flight control system. This paper describes a development process that integrates the designed control law into HETLAS to evaluate simulation effectively using nonlinear mathe...

This article investigates various transcription techniques for the Legendre pseudospectral (PS) method to compare the pros and cons of each approach. Eight combinations from four different types of collocation points and two discretization methods for dynamic constraints, which differentiate Legendre PS transcription techniques, are implemented to...

Detached eddy simulations were successfully applied to assess fully-turbulent external flows. DES exploits the advantages of RANS modeling inside of the boundary layer and large eddy simulation outside of the turbulent boundary layer. The DES results have generally shown excellent solutions for unsteady wake flows, but not for transitional flows be...

A unified numerical method for computing the quadrature weights, integration matrix, and differentiation matrix is newly developed in this study. For this purpose, a spline-like interpolation using piecewise continuous polynomials is converted into a global spline interpolation formula, with which the quadrature formulas can be derived from integra...

We present a study of vertical dynamics control of an electrostatically levitated gyro-accelerometer considering the wobbling effect and propose a tilt stabilization method with newly introduced control electrodes. Typically, a rotor in a vacuum rotates at high velocity, which may create a drift rate and lead to displacement instability due to the...

A novel hybrid evolutionary algorithm is developed based on the particle swarm optimization (PSO) and genetic algorithms (GAs). The PSO phase involves the enhancement of worst solutions by using the global-local best inertia weight and acceleration coefficients to increase the efficiency. In the genetic algorithm phase, a new rank-based multi-paren...

This paper presents a vision/LiDAR integrated navigation system that provides accurate relative navigation performance on a general ground surface, in GNSS-denied environments. The considered ground surface during flight is approximated as a piecewise continuous model, with flat and slope surface profiles. In its implementation, the presented syste...

This paper is focused on the development of an efficient hybrid optimizer using particle swarm optimization and an improved genetic algorithm with an effective constraint handling scheme for constrained nonlinear optimization. The basic operators of genetic algorithm, i.e., crossover and mutation are revisited and a new rank-based multi-parent cros...

The objective of this research is to develop a real-time embedded onboard flight control system (FCS) that provides dual communication linkage functionality and real-time signal processing for a pilot command, guidance, navigation, and control of a rotary unmanned aerial vehicle (UAV) system. In particular, dual communication linkage is realized th...

In this paper, a closed-loop system constructed with a linear plant and nonlinearity in the feedback connection is considered to argue against its planar orbital stability. Through a state space approach, a main result that presents a sufficient stability criterion of the limit cycle predicted by solving the harmonic balance equation is given. Prel...

The objectives of this research are development of guidance, navigation and control system for RUAV on virtual instrumentation and real flight test. For this research, the system is divided to DAQ (data acquisition) section, actuator section and controller section. And the hardware and software on each sections are realized on LabVIEW base. Waypoin...

The purpose of this paper deals with direct multiple-shooting method (DMS) to resolve helicopter maneuver problems of helicopters. The maneuver problem is transformed into nonlinear problems and solved DMS technique. The DMS method is easy in handling constraints and it has large convergence radius compared to other strategies. When parameterized w...

This paper deals with the State-Dependent Riccati Equation (SDRE) Technique for the design of rotorcraft waypoint guidance. To generate the flight trajectory through multiple waypoints, we use the trigonometric spline. The controller design and its validation is based upon a level 2 simulation rotorcraft model and the designed SDRE controller is ap...

This paper deals with the State-Dependent Riccati Equation (SDRE) Technique for the design of helicopter nonlinear waypoint guidance controller. To generate the flight guidance through multiple waypoints, we use the trigonometric spline. The controller design and its validation is based upon a level 2 simulation helicopter model and the designed SD...

This paper investigates a new loop design approach of force balance control for the vibratory rate sensor application. The proposed force balance control design takes advantages of the modified automatic gain control configuration in controlling the system’s oscillating dynamics at the sense mode. The adapted automatic gain control scheme and force...

In this paper, it is presented a novel approach for the self-sustained resonant accelerometer design, which takes advantages of an automatic gain control in achieving stabilized oscillation dynamics. Through the proposed system modeling and loop transformation, the feedback controller is designed to maintain uniform oscillation amplitude under dyna...

This paper deals with the State-Dependent Riccati Equation (SDRE) technique for the design of helicopter nonlinear flight controllers. Since the SDRE controller requires a linear system-like structure for nonlinear motion equations, a state-dependent coefficient (SDC) factorization technique is developed in order to derive the conforming structure...

This paper deals with the nonlinear optimal control approach to helicopter maneuver problems using the indirect method. We apply a penalty function to the integral deviation from a prescribed trajectory to convert the system optimality to an unconstrained optimal control problem. The resultant two-point boundary value problem has been solved by usi...

This paper deals with the nonlinear optimal control approach to helicopter maneuver problems using the indirect method. We apply a penalty function to the deviation from a prescribed trajectory to convert the system optimality to an unconstrained optimal control problem. The resultant two-point boundary value problem has been solved by using the mu...

A supersonic base flow is computed to investigate the effect of the eddy viscosity coefficient to the linear turbulence models. Slight modifications to the eddy viscosity coefficient, which are based on the realizability condition, are given to the Launder-Sharma turbulence model so that present models satisfy the realizability condition. Numerical...

The implicit formulation of rotor dynamics and its application to helicopter flight mechanics have been presented. The generalized vector kinematics regarding the relative motion between coordinates were expressed as a unified matrix operation and applied to get an inertial velocity and acceleration at arbitrary blade span position. Based upon thes...