Using Video Images for Determining Relative Disposition of Two Spacecrafts

В работе рассматривается математическая проблема определения взаимного положения и ориентации двух орбитальных аппаратов по данным видеосъемки. Обсуждаются недостатки простейших процедур оценивания, основанных на прямом (попиксельном) сравнении изображений, и предлагается более строгий метод, обеспечивающий быстрое и точное оценивание относительных параметров. Метод составлен из трех основных частей (инициализация, обновление и наблюдение), каждая из которых допускает независимую программную реализацию. Предложенный алгоритм тестировался на упрощенной задаче и обнаружил высокую точность получаемого результата.В роботі розглянуто математичну проблему визначення взаємного положення та орієнтації двох орбітальних апаратів за даними відео зйомки. Обговорюються недоліки найпростіших процедур оцінювання, що ґрунтуються на прямому (попіксельному) порівнянні зображень, і пропонується більш строгий метод, що забезпечує швидке та точне оцінювання відносних параметрів. Метод складається з трьох основних частин (ініціалізація, оновлення та спостереження), кожна з яких може бути реалізована незалежно від інших. Запропонований алгоритм випробувався на спрощеній задачі та показав високу точність одержуваного результату.The purpose of the article is to construct a model-based method that provides fast and accurate estimation of relative position and attitude of the target spacecraft. We discuss possible drawbacks of direct procedures based on straightforward (pixel-wise) image fitting and propose a subtle algorithm which satisfies formulated conditions. Results. The algorithm composed of three independent parts (initialization, pose refinement and pose tracking) has been developed and tested on simple initial datum. Initialization stage, responding for rough estimation in the absence of preliminary information, has given relatively poor but quite enough accuracy for the aims of initial approximation. Pose refinement stage which is implemented as iterative procedure based on closeness of neighboring frames demonstrated almost total matching with actual values. Pose tracking (state estimation based on equations of motion) was redundant for our simple example as it could not improve the result provided by pose refinement

Development of miniature robotic arm manipulators to enable smallsat clusters

The performances of monolithic spacecraft are limited by their size, mass and cost. For example, the sizes of a communication satellite antenna or of a space telescope primary mirror directly impact their performances. In-space assembly and formation flying missions are the logical responses to this issue. Instead of limited dedicated launches, several small satellites can be piggybacked as secondary payload and work together to accomplish the same mission. Therefore, this concept reduces the cost but also removes the limit of size and mass since more spacecraft can always be added to the formation while increasing robustness (the independent spacecraft are replaceable) and modularity (the reconfiguration of the formation can lead to different outcomes). This research is the result of a collaboration between the Jet Propulsion Laboratory (JPL) and University of Illinois at Urbana Champaign (UIUC). It presents the development of an integrated, robust and optimized method to enable scalable small satellites clusters via Clusters Forming On-Board Robotic Manipulators (C-FORM). The physical connection removes the constraint of highly sophisticated control for collision avoidance, the main obstacle of formation flying missions. After the deployment phase, pairs of satellites will sequentially rendezvous, deploy their miniature robotic arms and dock with the help of their end effectors. The dockings will be repeated until the formation is formed. JPL developed and designed both the robotic arms and the end effectors. Under the requirements of the mission, the components were selected for the satellite bus. A simulation was developed in order to model the dynamics of the spacecraft under realistic sensors and actuators to validate the feasibility of this concept. Finally, a quantitative estimation of the amount of fuel the robotic arms can save for formation flying purposes was carried out

Autonomous Visual Servo Robotic Capture of Non-cooperative Target

This doctoral research develops and validates experimentally a vision-based control scheme for the autonomous capture of a non-cooperative target by robotic manipulators for active space debris removal and on-orbit servicing. It is focused on the final capture stage by robotic manipulators after the orbital rendezvous and proximity maneuver being completed. Two challenges have been identified and investigated in this stage: the dynamic estimation of the non-cooperative target and the autonomous visual servo robotic control. First, an integrated algorithm of photogrammetry and extended Kalman filter is proposed for the dynamic estimation of the non-cooperative target because it is unknown in advance. To improve the stability and precision of the algorithm, the extended Kalman filter is enhanced by dynamically correcting the distribution of the process noise of the filter. Second, the concept of incremental kinematic control is proposed to avoid the multiple solutions in solving the inverse kinematics of robotic manipulators. The proposed target motion estimation and visual servo control algorithms are validated experimentally by a custom built visual servo manipulator-target system. Electronic hardware for the robotic manipulator and computer software for the visual servo are custom designed and developed. The experimental results demonstrate the effectiveness and advantages of the proposed vision-based robotic control for the autonomous capture of a non-cooperative target. Furthermore, a preliminary study is conducted for future extension of the robotic control with consideration of flexible joints

Proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress

Published proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress, hosted by York University, 27-30 May 2018