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Attitude Control System for an Earth observation satellite

Narkiewicz Janusz, Grünvald Szabolcs, Sochacki Mateusz

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2024

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Vol. 72, nr 2

art. no. e148612

EN

The objective of the research was to develop the Attitude Control System algorithm to be implemented in the Earth Observation Satellite System composed of leader-follower formation. The main task of the developed Attitude Control System is to execute attitude change manoeuvres required to point the axis of the image acquisition sensor to the fixed target on the Earth’s surface, while the satellite is within the segment of an orbit, where image acquisition is possible. Otherwise, the satellite maintains a nadir orientation. The control strategy is realized by defining the high-level operational modes and control laws to manage the attitude control actuators: magnetorquers used for desaturation of the reaction wheels and reaction wheels used for agile attitude variation. A six-degree-of-freedom satellite model was used to verify whether the developed Attitude Control System based on PID controllers for actuators performs attitude control in line with the requirements of an Earth Observation System. The simulations done for a variety of combinations of orbital parameters and surface target positions proved that the designed Attitude Control System fulfils the mission requirements with sufficient accuracy This high-level architecture supplemented by a more detailed control system model allowed proving efficient functionalities performance.

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Characterization of the anteroposterior center of pressure in upright position in type 2 diabetics with peripheral diabetic neuropathy and paired healthy controls

Toloza-Cano Daissy Carola, Zequera Martha, González Gustavo Hernando Castro

Biocybernetics and Biomedical Engineering

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2021

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Vol. 41, no. 1

306--315

EN

Peripheral diabetic neuropathy (PDN) is a complication of type 2 diabetes (T2DM) that impairs posture control and increases the risk of falling. The aim of this study was to characterize the anteroposterior center of pressure (COP-AP) in the time and the frequency domains in the T2DM/PDN group in relation to the control group. To that end we: (1) evaluated the efficacy of using both linear and non-linear discrete wavelet transform (DWT) analyses to evaluate oscillation patterns in the anteroposterior center of pressure (COP-AP) in the bipedal position in terms of time and frequency and (2) established input parameters for a model for predicting the risk of falling. This study included an experimental sample of 30 people with T2DM/PDN matched by gender, age, weight and height with a control sample of 30 healthy individuals. Unreported techniques for analyzing the COP-AP literature were assessed for their capacity to model patient bodily stability in the proprioceptive, visual and vestibular systems. To measure COP-AP, five tests were performed under different conditions as outlined in the Romberg Test using the ‘‘PEDAR System’’ for measuring plantar pressure. DWTs were used to calculate excursion parameters, average speeds, range, RMS values, the average maximum and minimum amplitude, power spectral densities and energy percentages in 11 frequency bands (D1 to D10 and A10). There were significant differences between the two study groups in terms of the calculated linear parameters ( p < 0.05). Using linear and non-linear DWT analyses, a preliminary characterization of COP-AP patterns was achieved. DWT could be used alongside linear analysis to determine the effect changes in these systems have on postural oscillation in people with T2DM.

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Nonlinear measures in posturography compared to linear measures based on yoga poses performance

Błażkiewicz MIchalina

Acta of Bioengineering and Biomechanics

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2020

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Vol. 22, no. 4

15--21

EN

Yoga is known as a type of exercise that combines physical, mental and spiritual aspects. There has not been much research on the postural control in various yoga poses. The aim of this study was to examine CoP regularity in both yoga instructors and novices during the performance of four yoga poses, and to verify the sensitivity of linear and nonlinear methods for assessing postural stability. Methods: The dynamic characteristics of CoP fluctuations were examined using linear and nonlinear methods on a group of 22 yoga instructors (Y) and 18 age-matched non-practitioners of yoga (NY). The study involved maintaining a balance for 20 seconds while performing four yoga poses. Results: Conventional analysis of CoP trajectories showed that NY and Y exhibited similar control of postural sway, as indicated by similar CoP path-length and area values observed in both groups. These results suggest that the special balance yoga training received by Y may not have an impact on less challenging balance conditions, such as the poses used in this experiment. Interestingly, nonlinear dynamical analysis of CoP showed that Y exhibited less CoP regularity and more complex signal than NY, as evidenced by higher values of sample entropy and fractal dimension. Conclusions: The results shed light on the surplus values of CoP trajectories in the nonlinear dynamical analysis to gain further insight into the mechanisms involved in posture control.

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Stabilometric profile of handstand technique in male gymnasts

Sobera Małgorzata, Serafin Ryszard, Rutkowska-Kucharska Alicja

Acta of Bioengineering and Biomechanics

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2019

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Vol. 21, no. 1

63--71

EN

This study aimed to determine the characteristic features of handstand posture control associated with a high level of ability among male gymnasts. Methods: 8 acrobatic gymnasts (4 more and 4 less experienced) participated in the study. They performed a 10-second handstand five times with each hand positioned on one AccuSway (AMTI) force platform and the other hand on the second. Body sway changes were recorded in time series: centre of pressure (COP) and components of the ground reaction force (GRF) (vertical, medial-lateral and anterior-posterior). The COP amplitude and average of GRF components, the index of frequency (by Fast Fourier Transform) for the right and left hand were calculated. Results: More experienced gymnasts performing a handstand concentrate mainly on minimizing anterior-posterior body sway with minimum medial-lateral body sway. Less experienced gymnasts’ pressure exerted on a surface by the hands is irregular in a medial-lateral direction. More experienced gymnasts control body position in the handstand and show less variation of body sway compared to less experienced gymnasts. More experienced gymnasts revealed lower frequency of body sway in the handstand compared to less experienced gymnasts. Conclusion: The stabilometric profile of more experienced gymnasts means the better posture control in handstand. The minimizing of body sway is compensated by exerting more force on a floor surface and the less experienced athletes cannot do that even after several years of training. The gymnasts of both groups, during standing on their hands, put more load on the right hand.

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Gender differences in postural stability in elderly people under institutional care

Wiśniowska-Szurlej Agnieszka, Ćwirlej-Sozańska Agnieszka, Wilmowska-Pietruszyńska Anna, Wołoszyn Natalia, Sozański Bernard

Acta of Bioengineering and Biomechanics

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2019

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Vol. 21, no. 2

45--53

EN

The aim of the research was to assess the postural stability indicators of older women and men receiving institutional care. Methods: The study involved 123 people aged 65–85, living in residential care homes in Rzeszów district. The main research tool was the CQ-Stab 2P 2-platform posturograph. Results: There were statistically significant differences between women and men in the total statokinesiogram path length, the statokinesiogram path length in the anteroposterior direction, the mean COP displacement in the anteroposterior direction as well as the mean velocity of the COP point in the anteroposterior direction under eye control ( p = 0.04). In the case of absence of visual control, men were characterized by significantly worse parameters in the area of mean COP displacement in the anteroposterior and lateral directions as well as the maximal COP displacement in the anteroposterior and lateral directions. It indicated that without visual control body balance parameters in men significantly worsened along with increasing age. A statistically significant difference was found between both genders in terms of the statokinesiogram path length, the mean COP displacement and the mean COP velocity ( p < 0.05). Conclusions: Gender differences in postural stability of older people under institutional care were noticed. Men were characterized by a lower level of postural stability compared to women. Elimination of visual control significantly worsened the balance of the body. The results obtained indicate the necessity of introducing therapeutic programs in nursing homes, taking proprioceptive exercises and exercises without visual input into account.

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Parametry odpowiedzi impulsowej w ocenie stabilności postularnej

Flis K., Pepłowski P., Kalejta M., Kowalczyk A., Błaszczyk J.

Pomiary Automatyka Kontrola

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2001

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R. 47, nr 7/8

10-13

PL

Przedstawiono różne aspekty modelowania układu kontroli postawy, ze szczególnym uwzględnieniem metod wykorzystujących teorię układow liniowych. Przyjęto, iż utrzymywanie równowagi możnaopisać modelem autoregresyjnym niskiego rzędu. Identyfikację przeprowadzono w oparciu o sygnał wychyleń środka nacisku stóp na platformę posturograficzną. Pokazano, że czas tłumienia i okres oscylacji wynikające z rozwiązań równania charakterystycznego są nowymi testami służącymi różnicowaniu pacjentów zdrowych i z patologią układu równowagi.