Recurrent-iterative algorithm for control synthesis of spacecraft terminal reorientation based on the method for analytical design of optimal controllers

The paper considers the application of the method for analytical design of optimal controllers as formulated by of A.A. Krasovsky (optimization according to the criterion of generalized work) for the control synthesis of spacecraft reorientation from an arbitrary angular position to a given attitude during a fixed time period. A predictive algorithm model was selected as a numerical implementation for the analytical design according to the generalized performance criterion. In order to investigate the angular motion optimization methods experimentally, a model of the spacecraft reorientation control process was developed and implemented in C#. Numerical experiments demonstrated that the generic algorithm does not ensure the specified accuracy of the final orientation, and an increase in the weight coefficients in the terminal member in order to reduce the orientation errors leads to a loss of stability of the dynamic process. The paper proposes a modification of the prediction algorithm — a recurrent-iterative algorithm for exact reorientation of a spacecraft in a fixed time period. The approach used in this case involves organizing an iterative procedure for synthesizing the optimal control of the spacecraft reorientation based on a prediction algorithm. The optimal control calculated at each iteration is used at the next step of the iterative procedure as the next additive component of programmable control. Numerical experiments demonstrated that the recursive-iterative method for reorienting a spacecraft ensures the angular motion stability of the spacecraft and the specified accuracy of the final orientation in a wide range of boundary conditions. The scope of the proposed algorithm is limited to control objects with continuum end-effectors. An example of such a control object is a remote sensing satellite with power gyroscopes (gyrodines) in the orientation system.

Sunflower inflorescences absorb maximum light energy if they face east and afternoons are cloudier than mornings

The mature inflorescence of sunflowers (Helianthus annuus) orients eastward after its anthesis (the flowering period, especially the maturing of the stamens), from which point it no longer tracks the Sun. Although several hypothetical explanations have been proposed for the ecological functions of this east facing, none have been tested. Here we propose an atmospheric-optical explanation. Using (i) astronomical data of the celestial motion of the Sun, (ii) meteorological data of diurnal cloudiness for Boone County located in the region from which domesticated sunflowers originate, (iii) time-dependent elevation angle of mature sunflower heads, and (iv) absorption spectra of the inflorescence and the back of heads, we computed the light energy absorbed separately by the inflorescence and the back between anthesis and senescence. We found that the inflorescences facing east absorb the maximum radiation, being advantageous for seed production and maturation, furthermore west facing would be more advantageous than south facing. The reason for these is that afternoons are cloudier than mornings in the cultivation areas of sunflowers. Since the photosynthesizing green back of mature heads absorbs maximal energy when the inflorescence faces west, maximizing the energy absorbed by the back cannot explain the east facing of inflorescences. The same results were obtained for central Italy and Hungary, where mornings are also less cloudy than afternoons. In contrast, in south Sweden, where mornings are cloudier than afternoons, west-facing mature inflorescences would absorb the maximum light energy. We suggest that the domesticated Helianthus annuus developed an easterly final orientation of its mature inflorescence, because it evolved in a region with cloudier afternoons.

Performing the enemy? No-risk logic and the assessment of prisoners in “radicalization assessment units” in French prisons

This article is based on a sociological research, combining qualitative interviews and ethnographic observations, undertaken in “radicalization assessment units” (RAU) in French prisons. The RAUs are units that hold, for a fixed period of time, a dozen prisoners described as “Islamic terrorists” or “suspected radicalization” so that a multidisciplinary team can evaluate their degree of radicalization. In the first section we will show how the climate of terrorist attacks during the period prior to opening of the RAUs not only engendered a warlike rhetoric that would overdetermine the decline of trust in detention. It also engendered institutional improvisation whereby these special units were set up one after another without much preparation. Secondly, we will detail the RAU’s security organization and the warlike relationship that grew between the guards and prisoners, between radical defiance and criminology of the Other. In the third section we will return to the evaluation work itself. During this evaluation work in the RAU, although each professional makes efforts to refine the prisoners’ profiles, the job is deeply biased by an obsession to fight against the “ taqîya” and against “dissimulators”. Lastly, at the end of the evaluation, the evaluation summary and recommendations for final orientation are overdetermined by the imperative to avoid professional risks.

Learning the Macroscopic Flow Model of Short Fiber Suspensions from Fine-Scale Simulated Data

Fiber–fiber interaction plays an important role in the evolution of fiber orientation in semi-concentrated suspensions. Flow induced orientation in short-fiber reinforced composites determines the anisotropic properties of manufactured parts and consequently their performances. In the case of dilute suspensions, the orientation evolution can be accurately described by using the Jeffery model; however, as soon as the fiber concentration increases, fiber–fiber interactions cannot be ignored anymore and the final orientation state strongly depends on the modeling of those interactions. First modeling frameworks described these interactions from a diffusion mechanism; however, it was necessary to consider richer descriptions (anisotropic diffusion, etc.) to address experimental observations. Even if different proposals were considered, none of them seem general and accurate enough. In this paper we do not address a new proposal of a fiber interaction model, but a data-driven methodology able to enrich existing models from data, that in our case comes from a direct numerical simulation of well resolved microscopic physics.

Point-to-Point Motion Planning of a Free-Floating Space Manipulator Using the Rapidly-Exploring Random Trees (RRT) Method

SUMMARYIt is usually proposed to use a robotic manipulator for performing on-orbit capture of a target satellite in the planned active debris removal and on-orbit servicing missions. Control of the satellite-manipulator system is challenging because motion of the manipulator influences position and orientation of the chaser satellite. Moreover, the trajectory selected for the capture manoeuvre must be collision-free. In this article, we consider the case of a nonredundant manipulator mounted on a free-floating satellite.We propose to use the bi-directional rapidly-exploring random trees (RRT) algorithm to achieve two purposes: to plan a collision-free manipulator trajectory that, at the same time, will result in a desired change of the chaser satellite orientation. Several improvements are introduced in comparison to the previous applications of the RRT method for manipulator mounted on a free-floating satellite. Feasibility of the proposed approach is demonstrated in numerical simulations performed for the planar case in which the chaser satellite is equipped with a 2-DoF (Degree of Freedom) manipulator. The obtained results are analysed and compared with the results obtained from collision-free trajectory planning methods that do not allow to set the desired final orientation of the chaser satellite.

The Discussion about the European Experience in Deliberation Judicial Reform in the Russian Magazines (1857–1864)

Purpose. Analyzed articles about past and present European of justice, published in the periodical socio-political (“Russian Gerald”, “Domestic notes”, “Contemporary”) and departmental (magazines published by ministries) publications in 1857–1864 in the context of discussions on judicial reform. Results. A total of 43 texts on the past and present of European justice were identified, which belong to 25 authors. The authors identify as professors of low and civil servants. At the heart of their professional worldview was the state-historical school of law, so they revealed through the press its values. Refined of the most discussed topics: the organization of local justice, advocacy and jury. There is a discussion between the supporters of the English and French justice systems, their argumentation is considered. Supporters of the English judicial system argued that England is not as similar to Europe as Russia, so its experience may be interesting. But they stressed that the judicial institutions of England are very closely connected with its specific history and culture. Adherents of the French model of justice found positive its organization, uniformity and high educational level for judicial officials and lawyers. They also pointed out that in the countries of continental Europe, where justice has been reformed in the French model, it is functioning successfully. Proved the dependence between the final orientation of the printing on the French model and the assumption of office of Minister of justice D. N. Zamyatnin. Conclusion. It is emphasized that, in addition to respect for the judicial systems of European countries, there were skeptical judgments about the use of these samples in the Russian Empire.

Динамика импульсного перемагничивания магнитоодноосных наночастиц

The magnetic moment response of a magneto-uniaxial nanoparticle and a flat lattice of similar nanoparticles are being studied under the action of a short Gaussian pulse of a magnetic field in the presence and in the absence of its modulation. The periodic dependence of the final orientation and duration of a response of the magnetic moments on the pulse duration and its peak value have been revealed and analyzed. The effect on processes magnetization reversal of a weak magnetizing field and the deviation of the pulse of field from the transverse orientation has been studied. Have been shown that the influence of the dipole-dipole interaction leads to modulation of the response to the pulse action.

DEVELOPMENT OF UAV PHOTOGRAMMETRY METHOD BY USING SMALL NUMBER OF VERTICAL IMAGES

This new and efficient photogrammetric method for unmanned aerial vehicles (UAVs) requires only a few images taken in the vertical direction at different altitudes. The method includes an original relative orientation procedure which can be applied to images captured along the vertical direction. The final orientation determines the absolute orientation for every parameter and is used for calculating the 3D coordinates of every measurement point. The measurement accuracy was checked at the UAV test site of the Japan Society for Photogrammetry and Remote Sensing. Five vertical images were taken at 70 to 90 m altitude. The 3D coordinates of the measurement points were calculated. The plane and height accuracies were ±0.093 m and ±0.166 m, respectively. These values are of higher accuracy than the results of the traditional photogrammetric method. The proposed method can measure 3D positions efficiently and would be a useful tool for construction and disaster sites and for other field surveying purposes.