As a new sampling technique, a “Harpoon & Penetrator” method by a tethered sampler is planned instead of “Touch and Go” method for the next sample return project of small celestial bodies explorations. This paper reports about the results of micro gravity experiments by using parabolic flights of the airplane in order to analyze 3-dimensional dynamic behavior of the tethered rigid body. Objectives of the experiments are demonstration of feasibility of the present sampling method and observation of dynamic characteristics in micro gravitational environments. The extraction / catching experiments and the launch / deployment experiments are explained in this paper. These results contribute to the feasibility study of the tethered sampler and will help to understand the characteristics and to make trade off of the tethered sampling methods.
A spaceflight validation of bare electro dynamic tape tether technology was conducted. A S520-25 sounding rocket was launched successfully at 05:00am on 31 August 2010 and
successfully deployed 132.6m of tape tether over 120 seconds in a ballistic flight. The electrodynamic performance of the bare tape tether employed as an atmospheric probe was measured. Flight results are introduced through the present progressive report of the
demonstration and the results of flight experiment are examined as the premier report of the international cooperation between Japan, Europe, USA and Australia. Future plans for maturing space tether technology, which will play an important role for future space activities, are also discussed.
This study is devoted to investigate slew maneuver of a flexible space structure. The flexible space structure treated in the present study is a rigid body equipped with a flexible aluminum bean, and the control scheme is defined as a method to minimize the bending-moment at the root of the flexible appendage during slew maneuver. The hierarchical gradient algorithm is employed to obtain the optimal control profile. Original of the algorithm can only treat inequality constraints on the state variables, and not on the maximum value of control input. It is necessary in the present problem formulation to take into consideration constraints on the control input since maximum value of control input is naturally limited. This paper proposes a method to improve the hierarchical algorithm so that constraints on the control input can be treated. The method is analyzed numerically to verify the present modified algorithm, and to show that constraints both on the control input and bending-moment are satisfied. The resulting control profile is implemented in an experiment to verify its feasibility. Results of experiments show that bending-moment is effectively reduced in the case that constraint on the maximum value of bending moment is considered.
It has been expected to clarify the mechanism of free flying sports such as aerial ski, diving contest and so on. The attitude motion in those sports is constrained by the conservation of angular momentum, and the aerial players are, thus, a kind of nonholonomic, under-actuated mechanical systems with initial angular momentum, in which the number of the generalized coordinates is more than the number of control inputs. Because their dynamics is complicated, it is difficult to control them and grasp their motion intuitively. In addition, because zero gravity environments are hardly realized on the ground, it is difficult to carry out experiments with the actual machine for a long time. This paper addresses numerical simulations and experimental set up for attitude control by a feedback control strategy for 3-D free-flying robots with non-zero angular momentum, in which the attitude of the main body of the robot and configuration of the robot can approach the desired states. Contrary to past studies that considered only the final attitude, in this study, we consider situations to make the configuration of the robot transit some intermediate states to emulate performance in aerial sports.
As a result of the increased number of missions in space, the number of satellites that have completed their missions or have broken down has increased, leaving a great deal of space debris in orbit. Most space debris is found in GEO or low-altitude polar orbits and more than 9,600 pieces of debris having a diameter of over 10 cm are currently in orbit. The number of pieces of debris may increase further due to break up, which increases the chance of debris colliding with other spacecraft. To solve this problem, the development of space robots to capture and eliminate space debris from orbit has been explored extensively, and areas such as attitude estimation, formation flying or rendezvous(Kojima , 2005), manipulator control(Inaba & Oda , 2000), de-orbiting of space debris using electro-dynamic tether systems(Forward et al. , 2000; Ishige et al. , 2004) have been investigated. If the target satellite is incorporative, that is, for an example, if radar communication between the target satellite and the debris eliminator satellite is not possible, then image processing will be required in order to monitor the attitude of the satellite and to capture it by means of a robot manipulator. Image processing algorithms with lower computational costs are desired, because the computer resources installed on satellites are usually fewer than those on the ground. A great number of image processing algorithms have been developed for various purposes, such as edge extraction(Harris & Stephens , 1988; Kitchen & Rosenfeld , 1982) and silhouette extraction(Tomasi & Kaneda , 1991). In the EST-VII mission(Inaba & Oda , 2000), the target markers were installed on the daughter satellite so that the mother satellite can easily monitor the attitude of the daughter satellite. However, normally it is not easy to recognize the attitude of satellites in orbit, because commercial satellites that are not equipped with target markers are usually covered by multi-layer insulator (MLI) with numerous wrinkles that randomly reflect the Sun’s light, and such random reflection makes silhouette extraction more difficult. Furthermore, satellites often overlap the Earth, and the direction of the Sun’s light relative to the satellite varies with time. To estimate the attitude of a satellite, the iterative closest point (ICP) algorithm(Besl & McKay , 1992) has been studied by JAXA(Terui et al. , 2002), but this algorithm needs a computational cost. In order to avoid the computational cost of ICP, the grid closest point (GCP) algorithm (Yamany et al. , 1998) was developed using a hash-table technique. The GCP algorithm has 22
