Adaptive Time-delay Estimated Sliding Mode Control for a Bias Momentum Satellite with Two Reaction Wheels

An adaptive sliding mode control to stabilize the attitude of a bias momentum satellite with a time delay via two wheels is proposed. Stabilizing the attitude of a rigid body via two control torques is an under-actuated control problem, and belongs to the class of systems that are controllable but cannot be asymptotically stabilized via continuous state feed-back because Brockett\u27s necessary condition is not satisfied. The adaptive method combined with the sliding mode control estimates the time delay contained in the system by sensing the difference between the attitude predicted and the measured one at each sampling time and compensates for the time delay by predicting the current state using the past measured attitude and angular velocity. Provided that external disturbances and modeling uncertainties in the satellite moments of inertia are absent, the validity of the proposed adaptive time delay estimated sliding mode control for attitude control of a bias momentum satellite is verified through numerical simulations

Conjugated 3D Virtual Reality Worlds in Spacecraft Attitude Control

The chapter aims to contribute to the application of virtual reality (VR) in spacecraft attitude control for systems, possessing “Inertial Morphing (IM)” capabilities.The concept of IM, proposed/applied by authors in 2017, is attractive in design of the fully autonomous future space missions, as swift control, requiring minimized energy and computations, can be achieved with exiguous/paltry morphings. To assist rapid planning of the optimized maneuver scenarios, we propose collocated merging of the various VR simulation worlds for the same spacecraft or merging of the VR worlds for the same system (but in different configurations). This enabled concurrent utilization of different methods of modeling, including Poinsot’s and Bine’s construction and Euler’s equations. Therefore, superimposed VR worlds are called “conjugated.” We present the classical methods of modeling of the torque-free systems and then show their implementation in the developed VR-integrated interactive package. Effectiveness of the VR-conjugated environment is illustrated with its use for planning of spacecraft de-tumbling, spacecraft 180-degrees inversion, and 90-degrees inversion. The developed VR environment enables utilization of both the body-axes spacecraft coordinate system and inertial coordinate system with instant transition from one into another, switching on/off various virtual reality worlds for multiple supports in the process of mission design

Space demostration of bare electrodynamic tape-tether technology on the sounding rocket S520-25

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

T-REX: Bare electro-dynamic tape-tether technology experimetn on sounding rocket S520

The project to verify the performance of space tether technology was successfully demonstrated by the launch of the sounding rocket S520 the 25tu. The project is the space demonstration of science and engineering technologies of a bare tape electrodynamic tether (EDT) in the international campaign between Japan, USA, Europe and Australia. Method of "Inverse ORIGAMI (Tape tether folding)" was employed in order to deploy the bare tape EDT in a short period time of the suborbital flight. The deployment of tape tether was tested in a various experimental schemes on ground to show high reliability of tape tether deployment. The rocket was launched on the summer of 2010 and deployed a bare electro-dynamic tape tether with length 132.6 m, which is the world record of the length deployment of tape tether. The verification of tether technology has found a variety kind of science and technology results as the first in the humankind and will lead a large number of applications of space tether technologie

Mu-Beta event-related (de)synchronization and EEG classification of left-right foot dorsiflexion kinaesthetic motor imagery for BCI.

The left and right foot representation area is located within the interhemispheric fissure of the sensorimotor cortex and share spatial proximity. This makes it difficult to visualize the cortical lateralization of event-related (de)synchronization (ERD/ERS) during left and right foot motor imageries. The aim of this study is to investigate the possibility of using ERD/ERS in the mu, low beta, and high beta bandwidth, during left and right foot dorsiflexion kinaesthetic motor imageries (KMI), as unilateral control commands for a brain-computer interface (BCI). EEG was recorded from nine healthy participants during cue-based left-right foot dorsiflexion KMI tasks. The features were analysed for common average and bipolar references. With each reference, mu and beta band-power features were analysed using time-frequency (TF) maps, scalp topographies, and average time course for ERD/ERS. The cortical lateralization of ERD/ERS, during left and right foot KMI, was confirmed. Statistically significant features were classified using LDA, SVM, and KNN model, and evaluated using the area under ROC curves. An increase in high beta power following the end of KMI for both tasks was recorded, from right and left hemispheres, respectively, at the vertex. The single trial analysis and classification models resulted in high discrimination accuracies, i.e. maximum 83.4% for beta ERS, 79.1% for beta ERD, and 74.0% for mu ERD. With each model the features performed above the statistical chance level of 2-class discrimination for a BCI. Our findings indicate these features can evoke left-right differences in single EEG trials. This suggests that any BCI employing unilateral foot KMI can attain classification accuracy suitable for practical implementation. Given results stipulate the novel utilization of mu and beta as independent control features for discrimination of bilateral foot KMI in a BCI

Utilisation of the Controllable Inertial Morphing for Providing Spacecraft with Acrobatic Attitude Capabilities.

The paper is exploring a new method of controlling of the attitude dynamics of the spacecraft with non-zero angular momentum, using deliberately applied changes to the spacecraft inertial properties, called inertial morphing (IM). This method does not employ classical gyroscopic devices, nevertheless it enables the spacecraft to perform various acrobatics manoeuvres, allowing interchanges between stable and unstable states. In one case scenario, it enables transformation of the stable spin into unstable flipping motion and establishment of the desired periods of the flips at various stages of the procedure. Special consideration is given to the selection of the controllable morphed parameters to impose the desired periods and patterns of the acrobatics. This paper exploits use of the unstable flipping motions of the systems and due to established mini-max relationships for the flipping periods, enables selection of the system parameters, maximizing or minimizing the values of the periods for faster (more agile) maneuvers. In the other scenario, IM is used to transfer the regular spin about one body axis into the regular spin about another nominated body axis. Numerous illustration cases are presented and application of the new enhanced capabilities are discussed in detail. For example, paper presents a scenario of the reconfiguration of the articulated spacecraft with its segments being inverted during the acrobatic procedure in the desired way, which may open new possibilities during the spacecraft operation, including re-boost and landing