Hyung-Don Choi

Large angle attitude control of spacecraft with actuator saturation

This paper presents spacecraft large angle attitude control problem with actuator saturation limit. Traditional approach for control design for the spacecraft large angle maneuver is a fixed gain proportional plus integral plus derivative (PID) controller using quaternion attitude variables with stability guarantee. Unwanted external disturbance inputs may induce excessively large error by the PID control. Anti-windup control and intelligent integrator are effective in reducing the rapid build up of the control signal due to, in particular, integral control action. Application of the anti-windup and intelligent integrator which already have been studied extensively in other areas is made to the large angle feedback controller minimizing reaction wheel type actuator saturation. Conventional PID controller is modified by augmenting additional control actions for the purpose of performance improvement.

An adaptive control approach to the attitude control of a flexible rocket

Abstract An adaptive notch filter design that considers the body-bending vibration associated with the attitude control of a two-stage sounding rocket is discussed in this paper. The algorithm adapts the parameters while keeping the poles of the notch filter inside the unit circle on the z -plane, and it satisfies the stability conditions of the filter at all times. Only a single parameter of the filter is adapted to simplify the algorithm to speed up the convergence rate. Applying this adaptive notch filter to the two-stage sounding rocket results in stable response characteristics of the attitude control system, which is unstable without adaptation.

Development of a GPS Receiver System for Satellite Launch Vehicles

This paper deals with electromagnetic tests of the GPS receiver system that should be developed to satisfy emission and susceptibility requirements for a satellite launch vehicle. Performance of the GPS receiver system against electromagnetic environment that is improved through several tests satisfies all requirements about electromagnetic tests. The outline of the electromagnetic tests and emission test results of CE102, CE106 and RE102 on MIL-STD-461E are described in Part Ⅰ.

Day-to-Day Repeatability of the Navigation Solution and SNR from the GPS Receiver installed on KSLV-I

This paper deals with quantitative analysis about the characteristics of GNSS(Global Navigation Satellite System) signals contaminated with multipath signals and day-to-day repeatability of the navigation solution and SNR(Signal to Noise Ratio) caused by multipath signals using the collected data from GPS receiver installed on KSLV-I which was on standby on the launch pad at Naro Space Center. Since the GPS antennas, surrounding environments and GPS satellite orbits were very slightly changed with respect to the day, the repeating pattern of the solution and SNR caused by the multipath signals was verified from the collected data. Analytic result of the multipath effects and day-to-day repeatability of the navigation solution and SNR observed at the launch pad would be used for obtaining more stable performance of the GPS receiver when the satellite launch vehicles are on standby.

Operation of the GPS Receiver System for KSLV-I on the Launch Site at Naro Space Center

This paper describes the operation results of the GPS receiver system for KSLV (Korea Space Launch Vehicle)-I on the launch site at Naro Space Center that is the first spaceport of South Korea located at Goheung. All equipments of KSLV-I including the GPS receiver system should be monitored and controlled through hard-wired interface during KSLV-I is on standby at the launch pad. The GPS receiver for KSLV-I is connected to triple almost omni-directional patch antennas mounted on the cylindrical surface of KSLV-I that should be erected vertically on the launch pad until lift-off. Signal interference and multipath effects observed in the GPS receiver on the launch site are analyzed in this paper based on the GPS signals received from each GPS antenna.

Attitude Control Design and Analysis for Thrust Vector Control System of 3-Staged Launch Vehicle

This paper concerns attitude controller design for a 3-staged launch vehicle which has movable nozzle TVC systems for all stages as its control systems. The PD-type control gains are determined by shaping the corresponding closed-loop natural frequencies for the purpose of guaranteeing the required stability margin. Bending filters are also designed to stabilize the bending modes by using parametric optimization method. The designed controllers are verified using six degree of freedom flight simulations in MATLAB.

Comparative Performance Analyses of GPS Receivers under High-Dynamic Conditions

The KSLV-I GPSR that is the first GPS receiver utilized on a satellite launch vehicle developed by KARI should operate normally under harsh environments such as extremely high vibration and shock, wide operating temperature range as well as high-dynamic conditions. Several extensive terrestrial tests have been already done in order to verify performance of the KSLV-I GPSR before flight. This paper deals with comparative performance analyses between the KSLV-I GPSR and other two GPS receivers without velocity and altitude restrictions under high-dynamic conditions. The tracking capability and accuracy of the GPS receivers are compared using a GPS signal simulator with various scenarios like a centrifuge, a satellite launch vehicle, and a spacecraft.

Electromagnetic Test of the GPS Receiver System for a Satellite Launch Vehicle - Part II. Susceptibility Test

This paper deals with electromagnetic tests of the GPS receiver system that should be developed to satisfy emission and susceptibility requirements for a satellite launch vehicle. The performance of the GPS receiver system against electromagnetic environment that is improved through several tests satisfies all requirements about electromagnetic tests. The susceptibility test results of CS101, CS114, CS115, CS116 and RS103 on MIL-STD-461E are described in Part II.

Electromagnetic Test of the GPS Receiver System for a Satellite Launch Vehicle - Part I. Outline & Emission Test

This paper deals with electromagnetic tests of the GPS receiver system that should be developed to satisfy emission and susceptibility requirements for a satellite launch vehicle. Performance of the GPS receiver system against electromagnetic environment that is improved through several tests satisfies all requirements about electromagnetic tests. The outline of the electromagnetic tests and emission test results of CE102, CE106 and RE102 on MIL-STD-461E are described in Part I.

Performance Analyses of the GPS Receiver for Satellite Launch Vehicles according to Temperature Variation

The GPS(Global Positioning System) receiver for satellite launch vehicles which will be mounted on a launch vehicle can be applied to the flight safety system with its accurately calculated position and velocity data during vehicle`s flight. This paper analyzes the performance of the GPS receiver such as SNR(Signal to Noise Ratio), fix mode, position and velocity error, number of visible and tracking satellites, and PDOP(Position Dilution of Precision) under temperature variation which is changed from -34 to +71.