Tatsushi Izumi

Robust flight control law design for an automatic landing flight experiment

Abstract The Automatic Landing FLight EXperiment, ALFLEX, was conducted by the National Aerospace Laboratory and National Space Development Agency of Japan, in order to develop their automatic landing technology for future unmanned reentry space vehicle. All the flight experiments were successfully completed. Because the ALFLEX vehicle is an unmanned and autonomous vehicle which has tip-fin wings, the flight control law has to achieve high-response-performance and robustness simultaneously. In this paper, the design method used to achieve these objectives is presented, as well as the results of flight experiments related to performance and robustness.

Flight control system for the Automatic Landing Flight Experiment

This paper discusses the flight control system developed for the Automatic Landing FLight Experiment, ALFLEX. ALFLEX is an experimental program conducted by the National Aerospace Laboratory and the National Space Development Agency of Japan in order to investigate the automatic landing technology for a future unmanned reentry space vehicle. The ALFLEX vehicle is a dynamically similar sub-scale model of the planned Japanese HII Orbiting Plane, HOPE. Since the HOPE program is in a preliminary conceptual design phase, the ALFLEX vehicle is a scaled model of one of the proposed configurations from 1992 research. The vehicle bare airframe is statically unstable in the pitch axis. In the lateral-directional axes, it has negative weather cock stability and strong dihedral effect, which introduce severe instability. The airframes instability and the landing performance requirement drive the flight control system design to be one of the key technologies in the HOPE program. Since the vehicles maximum L/D is approximately 4, it needs the same landing guidance technique as lifting body research vehicles and the Space Shuttle. This paper discusses the flight control design and the design methods applied to ALFLEX, and discusses lessons learned so far. The results from a preliminary flight test are briefly introduced. The series of automatic landing flights are scheduled for the middle of 1996, at Woomera, Australia, and will verify the guidance, navigation and control design. *Head, Control Qualification Lab., member AIAA Senior research engineer, Flight Research Division *^Research engineer, Control Research Division § Associate senior engineer, Winged Space Vehicle Office ^Engineer, Winged Space Vehicle Office *Asistant manager, Nagoya Aerospace Systems **Asistant manager, Nagoya Aerospace Systems Copyright

AUTOMATIC LANDING FLIGHT EXPERIMENT FLIGHT SIMULATION ANALYSIS AND FLIGHT TESTING

Preflight simulation analysis of flight experiment and flight test results are described. The automatic landing flight experiment was conducted in Woomera, Australia, in 1996, to develop the automatic landing technology required for the future Japanese uncrewed spacecraft. To ensure successful landings, computer simulation played an important role in the preflight analysis. Monte Carlo simulation was applied for the analysis. The root sum square method, which is commonly used in Japanese launcher rocket development projects, was also applied. Monte Carlo results were compared with the rss results and the flight test results. All 13 flight tests were successfully completed. Longitudinal guidance in the flare phase was found to be sensitive to some modeling errors. The cause is discussed.

Robust Flight Control Law Design for Automatic Landing Flight Experiment

Abstract Automatic Landing FLight EXperiment, ALFLEX, is conducted by National Aerospace Laboratory (NAL) and National Space Development Agency of Japan (NASDA) in order to develop the automatic landing technology for future unmanned reentry space vehicle, HOPE(H- II Orbiting PlanE). Total of 13 flight experiments were conducted at Woomera Australia in 1996, and all flight experiments were perfectly completed. Because ALFLEX vehicle, which is dynamically similar sub-scaled model(37%) of HOPE, is the unmanned and autonomous vehicle which has tip-fin wings, the flight control law has to achieve high-response-performance and robustness simultaneously. In this paper, the design method, which connects the MDM/MDP(Multiple Delay Model/Multiple Design Point) and the H∞ control design method combined with Exact Model Matching to achieve the objectives, is presented. And the results of flight experiment about the performance and the robustness are also presented.

LONGITUDINAL FLIGHT CONTROL FOR SPACE VEHICLE'S AUTOMATIC LANDING

This paper discusses a longitudinal flight path control designed and flight tested for Automatic Landing Flight Experiment, ALFLEX. ALFLEX, the flight test of which was conducted in 1996, demonstrated Japanese potentials for developing a reentry space vehicles automatic landing technology. In the program, however, longitudinal flight path control after the preflare maneuver is one of the critical items needed to satisfy the design requirement for landing on a limited length runway. Robustness against uncertainties and sensor errors is a key issue in longitudinal flight path control. The design was carefully conducted and flight tested. Although the flight test proved that the design result satisfied all the landing requirements, it identified critical parameters affecting the landing performance, such as longitudinal aerodynamics, navigation error and air data sensor error. This paper describes data obtained through the development and flight test, as well as further investigation conducted after the flight test in order to improve landing performance for the future space vehicle development. In the design review, a new approach called stochastic gain tuning is adopted, where the guidance feedback gain is tuned to maximize the probability of mission achievement. The results indicate some possibility of robustness improvement.

NAVIGATION AND GUIDANCE OF THE H-11 ORBITING PLANE

The National Space Development Agency of Japan (NASDA) has been studying an unmanned winged space vehicle. This is called HOPE, the H-II Orbiting Plane. The development of its guidance, navigation and control system requires much more versatile technology than those of the rocket and the satellite. Because of the long operation time and high accuracy requirement, the aided navigation is required for HOPE. The tentative navigation reference configuration for each flight phase is obtained based on the navigation analysis. Aerodynamic heating in the entry phase has the great influence on the HOPE design. The preliminary entry guidance analysis is carried out and the design constraints for HOPE are clarified. This paper presents the outline of the above discussions.

Navigation and Guidance of the H-11 Orbiting Plane

Abstract The National Space Development Agency of Japan (NASDA) has been studying an unmanned winged space vehicle. This is called HOPE, the Η-II Orbiting Plane. The development of its guidance, navigation and control system requires much more versatile technology than those of the rocket and the satellite. Because of the long operation time and high accuracy requirement, the aided navigation is required for HOPE. The tentative navigation reference configuration for each flight phase is obtained based on the navigation analysis. Aerodynamic heating in the entry phase has the great influence on the HOPE design. The preliminary entry guidance analysis is carried out and the design constraints for HOPE are clarified. This paper presents the outline of the above discussions.