Attitude Controller Design and Test of Korea Space Launch Vehicle-I Upper Stage

Abstract

On August 25, 2009, the first Korea Space Launch Vehicle, KSLV-I, was launched, as shown in Fig. 1. The KSLV-I is a two-stage launch vehicle. The payload is STSAT-2, a scientific satellite of 100 kg. The target orbit is a low Earth orbit with perigee altitude of 300 km, apogee altitude 1,500 km, and an inclination of 80 degree. To guide the KSLV-I through a nominal trajectory up to the target orbit, several attitude control systems are used. Typical control systems are thrust vector control (TVC) systems and reaction control system (RCS), which are commonly used for many launch vehicles worldwide.The first stage of KSLV-I has one liquid engine which can be swiveled by TVC actuators. The TVC actuators control the pitch and yaw attitude of the KSLV-I during the first stage flight. For roll attitude control, additional control systems are applied. First stage attitude control systems operate from lift-off until stage separation. The second stage has two TVC actuators, which swivel the nozzle of the second stage kick motor, and an RCS using cold nitrogen gas. The second stage attitude control systems stabilize attitude errors from stage separation until payload separation in order to target the flight direction exactly to the satellite mission orbit.Generally, an onboard autopilot consists of several attitude controllers. Attitude controllers need to be properly designed in order to handle onboard attitude control systems. The controllers must guarantee sufficient stability margins regardless of system variations and environment changes.In this paper, an attitude controller design and a test of the KSLV-I upper stage are introduced. First, the overall configuration of the upper stage control system is presented. Controller design problems and the corresponding results will be explained. The stability and performance of the designed controllers is verified via hardware in the loop (HIL) tests. Lastly, the flight test results relating to the upper stage attitude control is discussed. Attitude Controller Design and Test of Korea Space Launch Vehicle-I Upper StageByung-Chan Sun*, Yong-Kyu Park*, Woong-Rae Roh** and Gwang-Rae Cho*** KSLV Research and Development Head Office, Korea Aerospace Research Institute, Korea Abstract This paper introduces the upper stage attitude control system of KSLV-I, which is the first space launch vehicle in Korea. The KSLV-I upper stage attitude control system consists of two electro-hydraulic actuators and a reaction control system using cold nitrogen gas. A proportional, derivative, and integral controller is designed for the electro-hydraulic thrust vectoring system, and Schmidt trigger ON/OFF controllers are designed for the reaction control system. Each attitude controller is designed to have enough stability margins. The stability and performance of KSLV-I upper stage attitude control system is verified via hardware in the loop tests.

Quaternion-based attitude control design and hardware-in-the-loop simulation of suborbital modules with cold gas thrusters

“…The Schmitt trigger mechanism introduces a deadband and a hysteresis that eliminate additional fluctuations in the actuators. The modulator parameters are designed based on system performance requirements and by using equations (11) to (14). Here, the modular gain k m is selected equal to one, and the maximum torque output of the Schmitt Trigger mechanism is U m ¼ T i .L i, , where T i is maximum thrust level of thruster and L i is the thruster arm from the module's center of gravity.…”