In-Je Cho

Development of Low Altitude Terrain Following System based on TERain PROfile Matching

A flight capability to take a terrain following flight near the ground is required to reduce the probability that a fighter aircraft can be detected by foes radar fence in the battlefield. The success rate for mission flight has increased by adopting TFS (Terrain Following System) to enable the modern advanced fighter to fly safely near the ground at the low altitude. This system has applied to the state-of-the-art fighter and bomber, such as B-1, F-111, F-16 E/F and F-15, since the research begins from 1960s. In this paper, the terrain following system and GCAS (Ground Collision Avoidance System) was developed, based on a digital database with UTASs TERPRROM (TERrain PROfile Matching) equipment. This system calculates the relative location of the aircraft in the terrain database by using the aircraft status information provided by the radar altimeter and the INS (Inertial Navigation System), based on the digital terrain database loaded previously in the DTC (Data Transfer Cartridge), and figures out terrain features around. And, the system is a manual terrain following system which makes a steering command cue refer to flight path marker, on the HUD (Head Up Display), for vertical acceleration essential for terrain following flight and enables a pilot to follow it. The cue is based on the recognized terrain features and TCH (Target Clearance Height) set by a pilot in advance. The developed terrain following system was verified in the real-time pilot evaluation in FA-50 HQS (Handling Quality Simulator) environment.

Development and Validation of Automatic Thrust Control System

Modern version of advanced supersonic fighter have ATCS (Automatic Thrust Control System) to maximum flight safety, fuel efficiency and mission capability the integrated advanced autopilot system such as TFS (Terrain Following System), GCAS (Ground Collision Avoidance System) and AARS (Automatic Attitude Recovery System) and etc. This paper addresses the design and verification of ATCS based on advanced supersonic trainer in HILS (Hardware In the Loop Simulator) with minimum hardware modification to reduce of development cost and maintain of system reliability. The function of ATCS is consisted of target speed hold mode in UA (Up and Away) and angle of attack hold mode in PA (Power Approach). The real-time pilot evaluation reveals that pilot workload is minimized in cruise and approach flight stage by ATCS.

A Study on the Design and Validation of Switching Mechanism in Hot Bench System-Switch Mechanism Computer Environment

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.

Research flight control computer development for the flight control switching mechanism

The flight control switching mechanism system (FCSWMS) can give a pilot-selectable research control law capability due to the research flight control computer (RFCC) and the basis triplex primary flight control computer (PFCC), therefore this system provides a flexible platform for control law algorithm research. The research flight control system (RFCS) supports a design capability for relatively fast control law modifications and development, while retaining safety of flight through the PFCC. The RFCS processor was designed by more improved performance than primary FCC processor for the implementation of switching algorithm on the FCSWMS. The application software based on VxWorks operating system was developed on the tornado development environment. The verification and validation of research flight control computer system and software was performed in the hardware-in-the loop simulation environment including the primary flight control computer, cockpit and etc.. The RFCS verified through the software and system test will be useful for a variety of advanced control law research and future flight control system development.

A Study on the Design of Hardware Switching Mechanism using TCP/IP Communication

The SSWM(Software Switching Mechanism) of I-processor concept using non-real time in-house software simulation program is an effective method in order to develop the flight control law in desktop or HQS environment. And, this system has some advantages compare to HSWM(Hardware Switching Mechanism) such as remove the time delay effectiveness and reduce the costs of development. But, if this system loading to the OFP(Operational Flight Program), the OFP guarantee the enough throughput in order to calculate the two control law at once. Therefore, the HSWM(Hardware Switching Mechanism) of 2-processor concept is necessary. This paper addresses the concept of HSWM of the HQS-PC interface using TCP/IP(Transmission Control Protocol/Internet Protocol) 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 in order to reduce the abrupt transient response and minimize the integrator effect in pitch axis. The result of the analysis based on HQS pilot simulation using HSWM reveals that the flight control systems are switching between two computers without any problem.

A Study on the Design of Software Switching Mechanism for Develops the Flight Control Law

Relaxed Static Stability(RSS) concept has been applied to improve aerodynamic performance of modern version supersonic jet fighter aircraft. Therefore, the flight control systems are necessary to stabilizes the unstable aircraft and provides adequate handling qualities. The initial production flight control system are verified by flight test and it`s always an elements of danger because of flight-critical nature of control law function and design error due to model base design method. These critical issues impact to flight safety, and it could be lead to a loss of aircraft and pilot`s life. Therefore, development of an easily modifiable RFCS(Research Flight Control System) capable of reverting to a PFCS(Primary Flight Control System) of reliable control law must be developed to guarantee the flight safety. This paper addresses the concept of SSWM(Software Switching Mechanism) using the fader logic such as TFS(Transient Free Switch) based on T-50 flight control law. The result of the analysis based on non-real time simulation in-house software using SSWM reveals that the flight control system are switching between two computers without any problem.

Flight control computer operational flight program development for the control laws switching mechanism

All new flight control law and flight control computer developments have historically been an extremely expensive and time-consuming proposition specially in a flight-critical system. To reduce and avoid these kind of problems, the switching mechanism method has been addressed. Here the switching mechanism needs two computers. One is a basic(or primary) computer already customized to the production airframe and the other one is a new developed computer with a research control law algorithm. So the basic computer provides a pilot-selectable research flight control law capability during flight. This paper describes the modified basic digital fly-by-wire Flight Control Computer(FCC) software development for the switching mechanism which has been already verified for the safety of flight in its operational field. This paper also presents and describes system design, software mechanization design, autocode design for the switching algorithm, and system verification and validation(V&V). The function of switching and data communication can minimize the interferences between two computers, two control laws, or both. This successful flight control system for switching mechanism will provide a useful equipment for the future development of risk challengeable control laws algorithm, software, and hardware development.