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Path following Control of an Underactuated Catamaran for Recovery Maneuvers.

ABSTRACT: This paper focuses on the autonomous recovery maneuvers of an unknown underactuated practical catamaran, which returns to its initial position corresponding to the man overboard (MOB) by simply adjusting the rate of turn. This paper investigates the completion of model-based path following control for not only the traditional Williamson turn, but also complex recovery routes under time-varying disturbances. The main difficulty of model-based path following control for predicting the hydrodynamic derivatives of a practical catamaran was solved by the approximated calculation of a diagonal matrix. The second key problem of differential calculation for an underactuated model in the case of complex reference trajectories under severe disturbances was investigated. Even though this paper employs a diagonal matrix with unknown nonlinear terms, the experimental test using a small craft with payloads by remote control demonstrated the sway force per yaw moment in turning cases. Adaptive backstepping mechanisms with unknown parameters were proven by the Lyapunov theory as well as the passive-boundedness of the sway dynamics, guaranteeing the stability of sway motion in the case of unavailable sway control. The effectiveness of the algorithms of the guiding concept and error dynamics is demonstrated by the numerical simulations.

SUBMITTER: Lee SD

PROVIDER: S-EPMC8948864 | biostudies-literature | 2022 Mar

REPOSITORIES: biostudies-literature

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Path following Control of an Underactuated Catamaran for Recovery Maneuvers.

Lee Sang-Do SD Song Yong-Seung YS Kim Dae-Hae DH Kang Ma-Ru MR

Sensors (Basel, Switzerland) 20220314 6

This paper focuses on the autonomous recovery maneuvers of an unknown underactuated practical catamaran, which returns to its initial position corresponding to the man overboard (MOB) by simply adjusting the rate of turn. This paper investigates the completion of model-based path following control for not only the traditional Williamson turn, but also complex recovery routes under time-varying disturbances. The main difficulty of model-based path following control for predicting the hydrodynamic ...[more]

PMID: 35336404

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Project description:Uncertainty in risks posed by emerging stressors such as synthetic hormones impedes conservation efforts for threatened vertebrate populations. Synthetic hormones often induce sex-biased perturbations in exposed animals by disrupting gonad development and early life-history stage transitions, potentially diminishing per capita reproductive output of depleted populations and, in turn, being manifest as Allee effects. We use a spatially explicit biophysical model to evaluate how sex-biased perturbation in life-history traits of individuals (maternal investment in egg production and male-skewed sex allocation in offspring) modulates density feedback control of year-class strength and recovery trajectories of a long-lived, migratory fish-shovelnose sturgeon (Scaphirhynchus platorynchus)-under spatially and temporally dynamic synthetic androgen exposure and habitat conditions. Simulations show that reduced efficiency of maternal investment in gonad development prolonged maturation time, increased the probability of skipped spawning, and, in turn, shrunk spawner abundance, weakening year-class strength. However, positive density feedback disappeared (no Allee effect) once the exposure ceased. By contrast, responses to the demographic perturbation manifested as strong positive density feedback; an abrupt shift in year-class strength and spawner abundance followed after more than two decades owing to persistent negative population growth (a strong Allee effect), reaching an alternative state without any sign of recovery. When combined with the energetic perturbation, positive density feedback of the demographic perturbation was dampened as extended maturation time reduced the frequency of producing male-biased offspring, allowing the population to maintain positive growth rate (a weak Allee effect) and gradually recover. The emergent patterns in long-term population projections illustrate that sex-biased perturbation in life-history traits can interactively regulate the strength of density feedback in depleted populations such as Scaphirhynchus sturgeon to further diminish reproductive capacity and abundance, posing increasingly greater conservation challenges in chemically altered riverscapes.

Project description:OBJECT Pediatric sports-related concussions are a growing public health concern. The factors that determine injury severity and time to recovery following these concussions are poorly understood. Previous studies suggest that initial symptom severity and diagnosis of attention deficit hyperactivity disorder (ADHD) are predictors of prolonged recovery (> 28 days) after pediatric sports-related concussions. Further analysis of baseline patient characteristics may allow for a more accurate prediction of which patients are at risk for delayed recovery after a sports-related concussion. METHODS The authors performed a single-center retrospective case-control study involving patients cared for at the multidisciplinary Concussion Clinic at Children's of Alabama between August 2011 and January 2013. Patient demographic data, medical history, sport concussion assessment tool 2 (SCAT2) and symptom severity scores, injury characteristics, and patient balance assessments were analyzed for each outcome group. The control group consisted of patients whose symptoms resolved within 28 days. The case group included patients whose symptoms persisted for more than 28 days. The presence or absence of the SCAT2 assessment had a modifying effect on the risk for delayed recovery; therefore, stratum-specific analyses were conducted for patients with recorded SCAT2 scores and for patients without SCAT2 scores. Unadjusted ORs and adjusted ORs (aORs) for an association of delayed recovery outcome with specific risk factors were calculated with logistic regression analysis. RESULTS A total of 294 patients met the inclusion criteria of the study. The case and control groups did not statistically significantly differ in age (p = 0.7). For the patients who had received SCAT2 assessments, a previous history of concussion (aOR 3.67, 95% CI 1.51-8.95), presenting SCAT2 score < 80 (aOR 5.58, 95% CI 2.61-11.93), and female sex (aOR 3.48, 95% CI 1.43-8.49) were all associated with a higher risk for postconcussive symptoms lasting more than 28 days. For patients without SCAT2 scores, female sex and reporting a history of ADHD significantly increased the odds of prolonged recovery (aOR 4.41, 95% CI 1.93-10.07 and aOR 3.87, 95% CI 1.13-13.24, respectively). Concussions resulting from playing a nonhelmet sport were also associated with a higher risk for prolonged symptoms in patients with and without SCAT2 scores (OR 2.59, 95% CI 1.28-5.26 and OR 2.17, 95% CI 0.99-7.73, respectively). Amnesia, balance abnormalities, and a history of migraines were not associated with symptoms lasting longer than 28 days. CONCLUSIONS This case-control study suggests candidate risk factors for predicting prolonged recovery following sports-related concussion. Large prospective cohort studies of youth athletes examined and treated with standardized protocols will be needed to definitively establish these associations and confirm which children are at highest risk for delayed recovery.

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Path following Control of an Underactuated Catamaran for Recovery Maneuvers.

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Path following Control of an Underactuated Catamaran for Recovery Maneuvers.

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