Fuyuto Terui

Flight Control Design of an Unmanned Space Vehicle Using Gain Scheduling

A flight control design of an unmanned space vehicle using an interpolative gain-scheduling technique is presented. The ν-gap metric is used to evaluate the interpolative errors between linear models at operating points. The linear-parameter-varying models for the space vehicle are then constructed by minimizing a criterion using the ν-gap metric. Furthermore, multi-objective constraints are locally imposed on the specified operating points to improve the control performance. In the numerical simulations, the gain-scheduling control laws whose number of operating points was greater than two stabilized the space vehicle over the entire region. Furthermore, the input-saturation constraint was effective in suppressing the magnitude of the input and extending the stability region of the design parameter.

Generalized Attitude Model for Momentum-Biased Solar Sail Spacecraft

This paper describes a method of modeling general attitude dynamics of a nonspinning momentum-biased spacecraft under strong influence of solar radiation pressure. This model, called the “generalized sail dynamics model,” can be applied to realistic solar sail spacecraft with nonflat surfaces and nonuniform optical reflectance. A coarse sun-pointing momentum-biased spacecraft is especially of interest, for which an approximate solution of the equations of motion is analytically derived. Stability and fundamental characteristics of momentum-biased spacecraft dynamics as well as theoretical relations with past dynamics models are discussed in detail. Furthermore, unique attitude motion predicted by the novel model is verified with flight data of the Japanese interplanetary probe, Hayabusa 2.

Flight Control Designs Using v-Gap Metric and Local Multi-Objective Gain-Scheduling

This paper presents flight control designs of an unmanned space vehicle, HOPE-X vehicle using interpolative gain scheduling techniques. The ν -gap metric is used to evaluate the errors between linear models at operating points. The linear parameter varying models for the HOPE-X vehicle are then constructed by minimizing two types of indices defined with the ν -gap metric. On the other hand, the magnitude of the input is locally constrained to avoid the saturation of the control surfaces. In the numerical simulations of the HOPEX in the terminal area energy management (TAEM) phase, the gain scheduling control laws whose number of operating points was greater than two stabilized the HOPE-X vehicle over the entire region of the TAEM phase. Furthermore, the input-saturation constraint was effective in suppressing the magnitude of the input and to extend the stability region of the design parameter.

Spherical µ with Application to Flight Control Analysis

Robust stability analysis problems for linear systems subject to real parametric uncertainties are treated. We assume that uncertainties are restricted to a hypersphere in a parameter space. This constraint is representedby an inequality with respect to the Euclidean norm of a parameter vector. From a statistical point of view, the use of a spherical constraint can be justified if uncertain parameters are Gaussian-distributed random variables. We define an extended version of the real structured singular value, which is referred to as spherical (real) μ, for a spherical uncertainty set. Geometrically, the reciprocal of spherical μ means the radius of a guaranteed stable spherical region. We newly develop an upper bound of spherical μ, which is similar to a well-known upper bound of standard μ for a cubical uncertainty set, that is, parametric uncertainties subject to interval constraints. As its counterpart, the spherical μ upper bound can be computed by solving a linear matrix inequality problem. We apply the standard and spherical μ tools to a flight control problem. Through the numerical study, it is shown that spherical μ is less conservative than standard μ. The main contributions are the following: 1) An upper bound is developed for spherical p. 2) It is shown that the use of spherical μ is rationalized from a statistical perspective. 3) The newly derived upper bound is applied to the robust stability analysis of a flight control system.

RELATIVE MOTION ESTIMATION AND CONTROL TO A FAILED SATELLITE BY MACHINE VISION

Abstract An algorithm is developed for estimating the motion (relative attitude and relative position) of large pieces of space debris, such as failed satellites. The algorithm is designed to be used by a debris removal space robot which would perform six degree-of-freedom control (control its position and attitude simultaneously). The information required as feedback signals for such a controller is relative –- position, velocity, attitude and angular velocity–-and these are expected to be measured or estimated from image data. The algorithm uses a combination of stereo vision and 3D model matching, applying the ICP (Iterative Closest Point) algorithm, and uses time series of images to increase the reliability of estimates. To evaluate the algorithm, a simulator is prepared to simulate the on-orbit optical environment in terrestrial experiments, and the motion of a miniature satellite model is estimated using images obtained from the simulator.

Fast estimation of asteroid shape and motion for spacecraft navigation

In this paper, we consider fast simultaneous estimation problem of the geometric shape of the asteroid and the relative motion of the spacecraft. In asteroid exploration missions, the information of asteroid shape and motion is needed to find suitable landing sites and navigate the spacecraft safely. In the previous HAYABUSA mission, large part of the estimation was performed manually by ground operators. We propose an efficient automatic estimation method using the image feature matching and matrix decomposition based fast 3D reconstruction techniques. Preliminary experiment results are also shown.

TARGET ATTITUDE MOTION ESTIMATION AND TRACKING EXPERIMENT ON MICRO-SATELLITE "MICRO-LABSAT"

On a NASDA’s microsatellite named “μ-LABSAT,” which was launched by H-IIA on December 14, 2002 (Fig.1), Communications Research Laboratory (CRL), National Aerospace Laboratory (NAL) and University of Tokyo (UT) have been jointly performing several orbital experiments as technology demonstration towards the future orbital servicing missions. In University of Tokyo’s experiment which was held on May 14, 2003, the micro-satellite released a small object named “target,” and its rotational motion was estimated by the images captured continually using a camera developed by CRL. Then satellite attitude control was performed by visual feedbacks of the target image position on the camera frame so that the target image may come to a certain point on the camera frame. This is a pre-experiment of so-called LOS (Line Of Sight) control, which will be indispensable during rendezvous and docking to the satellite to be serviced. In this paper, the objectives and procedure of these experiments, and the results will be described. 54th International Astronautical Congress of the International Astronautical Federation, the International Academy of Astronautics, and the International Institute of Space Law 29 September 3 October 2003, Bremen, Germany IAC-03-A.P.06 Copyright

LPV controller design for the lateral-directional motion of re-entry vehicle

The development of Japanese unmanned reentry vehicle which is a part of the reusable space transportation system using H-II A launch vehicle is in progress. Since its dynamical characteristics such as stability derivatives change during the flight, it’s not feasible to use a single attitude controller which covers all flight conditions. This paper considers the application of Linear parametervarying (LPV) controller synthesis technique to the lateral-directional attitude control in the approach and landing phase. The robustness and the performance of the resulting LPV controller are investigated through linear analysis and nonlinear simulation.

Solar Radiation Pressure-Assisted Fuel-Free Sun Tracking and Its Application to Hayabusa2

This paper describes the modeling, dynamical characteristics, and implementation of an attitude control method that actively uses solar radiation pressure. The theory behind this control method is ...

Simultaneous estimation of shape and motion of an asteroid for automatic navigation

In an asteroid exploration and sample return mission, accurate estimation of the shape and motion of the target asteroid is essential for selecting a touchdown site and navigating a spacecraft during touchdown operation. In this work, we present an automatic estimation method for the shape and motion of an asteroid, which is planned to be tested in future exploration missions including Japanese Hayabusa-2 [1]. Our task is to estimate the shape and rotation axis of the asteroid, as well as positions of the spacecraft from optical images. The proposed method is based on the expectation conditional-maximization (ECM) framework that consists of an auxiliary particle filter and nonlinear optimization techniques. One of our technical contributions is the estimation of the direction of rotation axis of the asteroid from monocular camera images, which are taken by the moving spacecraft. We conducted two experiments with synthetic data and an asteroid mock-up to show the validity of the proposed method and to present the numerical accuracy.