A Case Study in the Mars Landing Site Selection for Science Objects

Seo, Haingja,Kim, Eojin,Kim, Joo Hyeon,Lee, Joo Hee,Choi, Gi-Hyuk,Sim, Eun-Sup 한국우주과학회 2012 Journal of Astronomy and Space Sciences Vol.29 No.4

It is a crucial matter to select a landing site for landers or rovers in planning the Mars exploration. The landing site must have not only a scientific value as a landing site, but also geographical features to lead a safe landing for Mars probes. In this regard, this study analyzed landing site of Mars probes and rovers in previous studies and discussed the adequacy of the landing site to scientific missions. Moreover, this study also examined domestic studies on the Mars. The frameworks of these studies will guide the selection of exploration sites and a landing site when sending Mars probe to the Mars through our own efforts. Additionally, this paper will be used as the preliminary data for selection of exploration site and a landing site.

A Case Study in the Mars Landing Site Selection for Science Objects

서행자,김어진,김주현,이주희,최기혁,심은섭 한국우주과학회 2012 Journal of Astronomy and Space Sciences Vol.29 No.4

It is a crucial matter to select a landing site for landers or rovers in planning the Mars exploration. The landing site must have not only a scientific value as a landing site, but also geographical features to lead a safe landing for Mars probes. In this regard, this study analyzed landing site of Mars probes and rovers in previous studies and discussed the adequacy of the landing site to scientific missions. Moreover, this study also examined domestic studies on the Mars. The frameworks of these studies will guide the selection of exploration sites and a landing site when sending Mars probe to the Mars through our own efforts. Additionally, this paper will be used as the preliminary data for selection of exploration site and a landing site.

모델예측제어에 기반한 화성정밀착륙 유도법칙 연구

정유연,방효충 한국항공우주학회 2014 한국항공우주학회 학술발표회 논문집 Vol.2014 No.11

화성은 태양계의 행성 중 지구와 가장 유사한 환경을 갖고 있어 인류가 거주할 수 있는 가능성이 가장 큰 행성이다. 따라서 화성탐사를 위한 착륙선의 연구 및 개발이 활발히 진행되고 있지만 아직까지 착륙 정확도의 향상이 절대적으로 필요한 상황이다. 정밀착륙유도를 위해서는 화성의 대기권을 통과하면서 발생하는 바람이나 대기 밀도의 변화와 같은 불확실성 요소에 대한 추정 및 예측이 필요하며 이 정보를 이용한 근 최적유도제어가 연구되어야 한다. 따라서 본 논문에서는 화성착륙 동역학 모델을 선형화하고 제약조건을 완화하여 모델예측제어를 적용 가능하게 하였다. 하지만 비용함수에서 발생하는 수치적 불안정성이 파라미터의 변화에 따라 발생하는 경우가 나타나 이를 해결할 방안 및 앞으로의 연구의 방향을 제시하였다. Mars is the planet most likely to be able to mankind live because Mars has most similar environment to the Earth’s environment in the solar system. Therefore, research and development of landing for the Mars exploration has been carried out actively, but in situations where absolutely necessary to improve the accuracy still landing. For the precision landing guidance, the estimation and prediction of uncertainties from the winds or atmospheric density variation is required, and the near-optimal guidance must be studied using these information. Thus, the dynamic model and the constraints of Mars landing were linearized and relaxed to apply model predictive control. The uncertainty variation affecting state variables was applied to the dynamic model and the near-optimal solution was obtained. Moreover this guidance logic was compared with other Mars landing guidance logics.

화성 지형상대항법을 위한 하강 데이터셋 생성과 랜드마크 추출 방법

김재인,Kim, Jae-In 대한원격탐사학회 2022 大韓遠隔探査學會誌 Vol.38 No.6

The Entry-Descent-Landing process of a lander involves many environmental and technical challenges. To solve these problems, recently, terrestrial relative navigation (TRN) technology has been essential for landers. TRN is a technology for estimating the position and attitude of a lander by comparing Inertial Measurement Unit (IMU) data and image data collected from a descending lander with pre-built reference data. In this paper, we present a method for generating descent dataset and extracting landmarks, which are key elements for developing TRN technologies to be used on Mars. The proposed method generates IMU data of a descending lander using a simulated Mars landing trajectory and generates descent images from high-resolution ortho-map and digital elevation map through a ray tracing technique. Landmark extraction is performed by an area-based extraction method due to the low-textured surfaces on Mars. In addition, search area reduction is carried out to improve matching accuracy and speed. The performance evaluation result for the descent dataset generation method showed that the proposed method can generate images that satisfy the imaging geometry. The performance evaluation result for the landmark extraction method showed that the proposed method ensures several meters of positioning accuracy while ensuring processing speed as fast as the feature-based methods.

Convex 최적화를 이용한 화성착륙 유도제어 알고리즘 연구

강상욱,변수영,김호영,방효충 한국항공우주학회 2013 한국항공우주학회 학술발표회 논문집 Vol.2013 No.11

화성탐사의 성공적인 임무수행을 위해서는 화성 착륙선을 정해진 목표지점에 정확히 착륙시키는 것이 매우 중요하다. 본 연구에서는 Convex optimization을 이용하여 목표지점까지 착륙선을 유도제어할 수 있는 추력하강단계의 착륙알고리즘에 관해 연구를 수행하였다. 미리 정해진 목표지점과 최소의 착륙 오차를 갖는 궤적을 생성한 후 연료소모를 최소화하는 궤적을 설계하였다. 착륙오차를 최소화하는 궤적은 추력벡터의 크기가 0이 아닌 하한값을 갖기 때문에 nonconvex 문제이다. 따라서 이 문제를 convex 최적화 문제로 변형하여 전역영역에서의 최적화 궤적을 찾는 알고리즘을 소개하였다. 이 연구는 실제 화성탐사시 실시간으로 적용할 수 있는 추력단계에서의 착륙알고리즘 개발에 많은 도움이 될 것이다. To perform the Mars mission successfully, it is important to land the lander precisely on the target of Mars surface which is determined in advance. In this study, powered descent guidance algorithm to guide lander on target was investigated using convex optimization. Minimum landing error trajectory is generated before designing trajectory of minimum fuel consumption for this study. the problem of minimum landing error trajectory is noconvex optimal control problem because of nonzero lower bound on the magnitude of thrust vector. So it is introduced to solve the optimal trajectory in global domain after converting this problem to convex optimal control problem. This study will be helped on development of powered descent guidance algorithm to apply on real time implementation for Mars mission.

Mars precision landing guidance based on model predictive control approach

Jung, Youeyun,Bang, Hyochoong SAGE Publications 2016 Proceedings of the Institution of Mechanical Engin Vol.230 No.11

<P>A precision landing guidance design for the Mars powered descent phase is proposed based on model predictive control (MPC) approach. Dynamics model used for the formulation are convexificated and linearized to adopt the convex optimization technique, which has been suggested by researchers of Jet Propulsion Laboratory. To employ the receding horizon frame and reduce the number of control inputs, the convex optimization problem is augmented with Laguerre functions. To represent the minimum fuel consumption or minimum landing error precisely unlike the optimal control theory, new cost function is designed by combining them with weighting factors. Moreover, the stability of the proposed guidance design for the independent control inputs calculated from each time step is verified by using Lyapunov stability analysis. Finally, numerical simulations are conducted to examine the suggested guidance formulation and to compare the performance with an optimal solution.</P>

Integrated Inertial and Radio Based State and Parameter Estimation for Mars Entry Phase Spacecraft Navigation

Natnael S. Zewge,Hyochoong Bang 제어로봇시스템학회 2021 제어로봇시스템학회 국제학술대회 논문집 Vol.2021 No.10

We address the entry phase navigation of Entry, Descent, and Landing (EDL) operation for future Mars spacecraft missions. The entry phase is characterized by a highly non-linear motion model and is influenced by various aerodynamic forces. Current entry phase navigation systems exclusively use Inertial Measurement Units (IMUs) from atmospheric entry to parachute deployment phase. This results in large error accumulation. Such systems cannot meet the precision landing requirements of future missions. In addition, entry phase filters designed using inertial measurement systems alone cannot observe some states which leads to diverging state estimates. We present an integrated navigation scheme whereby a ground based radio ranging device telemeters spacecraft range and range rate information to a computer on board the spacecraft. This information is fused with inertial measurements to yield a more accurate navigation system than a standalone inertial system. The paper implements the navigation scheme using the continuous-discrete Extended Kalman Filter (EKF) and the Unscented Kalman Filter (UKF). Performance comparisons are made between the two filters in terms of RMS error, runtime, and ease of implementation. Our results show comparable results between the two filters. The UKF provides better estimates of lift to drag ratio and downrange distance while the EKF outperforms the UKF with the rest of the state and parameter estimates. The fact that no Jacobian calculation is required in the case of the UKF renders it a more attractive option than the EKF in terms of ease of implementation for highly non linear systems.

모델예측제어이론에 기반한 화성정밀착륙 유도법칙 연구

정유연,방효충 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.4

화성의 대기권 통과 시 발생하는 항법오차가 존재하는 조건에서도 목표지점에 정밀하게 착륙할 수 있는 기술이 필요하다. 본 논문에서는 매 시간스텝마다 새로운 측정치를 이용한 최적화를 수행하는 모델예측제어이론에 기반하여 화성정밀착륙 유도법칙을 제안하였다. 전역 최적 해를 보장할 수 없는 모델예측제어이론의 단점을 화성착륙 운동방정식의 볼록 최적화를 통하여 해결하였으며 Laguerre 함수를 이용하여 수식전개를 단순화하였다. 또한 각 스텝에서 계산된 제어입력은 서로 독립적이기 때문에 Lyapunov 함수를 이용한 안정성을 증명하였다. 최종적으로 제안된 이론을 이용한 시뮬레이션을 수행하였다. The precise landing technology is required under the presence of the navigation error that was occurred during passing through the Martian atmosphere. In this paper, the precise landing guidance for Mars is suggested based on the model predictive control theory that performs optimization process at each time step. The drawback of the theory that cannot guarantee the global optimum is resolved by using convex optimization. Additionally, the formulation is simplified using Laguerre function. For independent control inputs obtained by independent optimization process, the stability is proved by Lyapunov stability. Finally, the simulation results are represented for the proposed guidance.

계층적 강화학습을 이용한 화성 탐사선의 자동 착륙 기법

최지민(Jimin Choi),안재명(Jaemyung Ahn) 한국항공우주학회 2022 한국항공우주학회 학술발표회 논문집 Vol.2022 No.11

외란과 불확실성에 강건한 비선형 제어기 설계

강상욱(Sang-Wook Kang),방효충(Hyochoong Bang),이상률(Sang-Ryool Lee) 한국항공우주학회 2017 한국항공우주학회 학술발표회 논문집 Vol.2017 No.11