A Comparison of Inverse Simulation-Based Fault Detection in a Simple Robotic Rover with a Traditional Model-Based Method

Robotic rovers which are designed to work in extra-terrestrial environments present a unique challenge in terms of the reliability and availability of systems throughout the mission. Should some fault occur, with the nearest human potentially millions of kilometres away, detection and identification of the fault must be performed solely by the robot and its subsystems. Faults in the system sensors are relatively straightforward to detect, through the residuals produced by comparison of the system output with that of a simple model. However, faults in the input, that is, the actuators of the system, are harder to detect. A step change in the input signal, caused potentially by the loss of an actuator, can propagate through the system, resulting in complex residuals in multiple outputs. These residuals can be difficult to isolate or distinguish from residuals caused by environmental disturbances. While a more complex fault detection method or additional sensors could be used to solve these issues, an alternative is presented here. Using inverse simulation (InvSim), the inputs and outputs of the mathematical model of the rover system are reversed. Thus, for a desired trajectory, the corresponding actuator inputs are obtained. A step fault near the input then manifests itself as a step change in the residual between the system inputs and the input trajectory obtained through inverse simulation. This approach avoids the need for additional hardware on a mass- and power-critical system such as the rover. The InvSim fault detection method is applied to a simple four-wheeled rover in simulation. Additive system faults and an external disturbance force and are applied to the vehicle in turn, such that the dynamic response and sensor output of the rover are impacted. Basic model-based fault detection is then employed to provide output residuals which may be analysed to provide information on the fault/disturbance. InvSim-based fault detection is then employed, similarly providing \textit{input} residuals which provide further information on the fault/disturbance. The input residuals are shown to provide clearer information on the location and magnitude of an input fault than the output residuals. Additionally, they can allow faults to be more clearly discriminated from environmental disturbances

Inverse Simulation as a Tool for Fault Detection and Isolation in Planetary Rovers

With manned expeditions to planetary bodies beyond our own and the Moon currently intractable, the onus falls upon robotic systems to explore and analyse extraterrestrial environments such as Mars. These systems typically take the form of wheeled rovers, designed to navigate the difficult terrain of other worlds. Rovers have been used in this role since Lunokhod 1 landed on the Moon in 1970. While early rovers were remote controlled, communication latency with bodies beyond the Moon and the desire to improve mission effectiveness have resulted in increasing autonomy in planetary rovers. With an increase in autonomy, however, comes an increase in complexity. This can have a negative impact on the reliability of the rover system. With a fault-free system an unlikely prospect and human assistance millions of miles away, the rover must have a robust fault detection, isolation and recovery (FDIR) system. The need for comprehensive FDIR is demonstrated by the recent Chinese lunar rover, Yutu (or “Jade Rabbit”). Yutu was rendered immobile 42 days after landing and remained so for the duration of its operational life: 31 months. While its lifespan far exceeded its expected value, Yutu's inability to move severely impaired its ability to perform its mission. This clearly highlights the need for robust FDIR. A common approach to FDIR is through the generation and analysis of residuals. Output residuals may be obtained by comparing the outputs of the system with predictions of those outputs, obtained from a mathematical model of the system which is supplied with the system inputs. Output residuals allow simple detection and isolation of faults at the output of the system. Faults in earlier stages of the system, however, propagate through the system dynamics and can disperse amongst several of the outputs. This problem is exemplified by faults at the input, which can potentially excite every system state and thus manifest in every output residual. Methods exist for decoupling and analysing output residuals such that input faults may be isolated, however, these methods are complex and require comprehensive development and testing. A conceptually simpler approach is presented in this paper. Inverse simulation (InvSim) is a numerical method by which the inputs of a system are obtained for a desired output. It does so by using a Newton-Raphson algorithm to solve a non-linear model of the system for the input. When supplied with the outputs of a fault-afflicted system, InvSim produces the input required to drive a fault-free system to this output. The fault therefore manifests itself in this generated input signal. The InvSim-generated input may then be compared to the true system input to generate input residuals. Just as a fault at an output manifests itself in the residual for that output alone, a fault at an input similarly manifests itself only in the residual for that input. InvSim may also be used to generate residuals at other locations in the system, by considering distinct subsystems with their own inputs and outputs. This ability is tested comprehensively in this paper. Faults are applied to a simulated rover at a variety of locations within the system structure and residuals generated using both InvSim and conventional forward simulation. Residuals generated using InvSim are shown to facilitate detection and isolation of faults in several locations using simple analyses. By contrast, forward simulation requires the use of complex analytical methods such as structured residuals or adaptive thresholds

Dance & Down Syndrome: Parental Perceptions on Dance and Movement-Based Interventions

This qualitative phenomenological study was designed to identify parent or guardian perceptions on the benefits of dance and movement-based interventions for their child who has Down syndrome. Individuals with Down syndrome face limitations in social-emotional skills, physical skills, and life skills, and research on the benefits of dance and movement-based interventions demonstrated some evidence of improvements in these skills. Researchers utilized a parent focus group in order to gain insight into how dance impacts their children with Down syndrome. A number of themes emerged from the data analysis process including improved movement, psychological well-being, and routine and retention. The theme of improved movement included concepts such as motor planning, balance, coordination, exercise, and increased strength and tone. The theme of psychological well-being included increased happiness, connecting with typically developing peers, and a sense of belonging. The theme of routine and retention included ideas about structure, routine, and learning and applying skills. The implications for dance and movement-based intervention in the field of occupational therapy are discussed, as well as suggestions for further research studies on this topic

Prevalence, Awareness, Treatment, and Control of Hypertension in United States Counties, 2001–2009

Hypertension is an important and modifiable risk factor for cardiovascular disease and mortality. Over the last decade, national-levels of controlled hypertension have increased, but little information on hypertension prevalence and trends in hypertension treatment and control exists at the county-level. We estimate trends in prevalence, awareness, treatment, and control of hypertension in US counties using data from the National Health and Nutrition Examination Survey (NHANES) in five two-year waves from 1999–2008 including 26,349 adults aged 30 years and older and from the Behavioral Risk Factor Surveillance System (BRFSS) from 1997–2009 including 1,283,722 adults aged 30 years and older. Hypertension was defined as systolic blood pressure (BP) of at least 140 mm Hg, self-reported use of antihypertensive treatment, or both. Hypertension control was defined as systolic BP less than 140 mm Hg. The median prevalence of total hypertension in 2009 was estimated at 37.6% (range: 26.5 to 54.4%) in men and 40.1% (range: 28.5 to 57.9%) in women. Within-state differences in the county prevalence of uncontrolled hypertension were as high as 7.8 percentage points in 2009. Awareness, treatment, and control was highest in the southeastern US, and increased between 2001 and 2009 on average. The median county-level control in men was 57.7% (range: 43.4 to 65.9%) and in women was 57.1% (range: 43.0 to 65.46%) in 2009, with highest rates in white men and black women. While control of hypertension is on the rise, prevalence of total hypertension continues to increase in the US. Concurrent increases in treatment and control of hypertension are promising, but efforts to decrease the prevalence of hypertension are needed

Deep North Atlantic last glacial maximum salinity reconstruction

Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography and Paleoclimatology 36(7), (2021): e2020PA004088, https://doi.org/10.1029/2020PA004088.We reconstruct deep water-mass salinities and spatial distributions in the western North Atlantic during the Last Glacial Maximum (LGM, 19–26 ka), a period when atmospheric CO2 was significantly lower than it is today. A reversal in the LGM Atlantic meridional bottom water salinity gradient has been hypothesized for several LGM water-mass reconstructions. Such a reversal has the potential to influence climate, ocean circulation, and atmospheric CO2 by increasing the thermal energy and carbon storage capacity of the deep ocean. To test this hypothesis, we reconstructed LGM bottom water salinity based on sedimentary porewater chloride profiles in a north-south transect of piston cores collected from the deep western North Atlantic. LGM bottom water salinity in the deep western North Atlantic determined by the density-based method is 3.41–3.99 ± 0.15% higher than modern values at these sites. This increase is consistent with: (a) the 3.6% global average salinity change expected from eustatic sea level rise, (b) a northward expansion of southern sourced deep water, (c) shoaling of northern sourced deep water, and (d) a reversal of the Atlantic's north-south deep water salinity gradient during the LGM.This work was supported by the US National Science Foundation (grant numbers 1433150 and 1537485).2021-10-2

Relationship between the Romberg Test and the Wii Basic Balance Test and Cognition in Athletes with Concussion

Background: Approximately 30% of individuals with a sport-related concussion present with postural instability. Multiple clinical balance tests exist to diagnose postural instability; yet little is known about the potential relationship between these type of postural assessments and cognition post-concussion. Aim: The purpose of the current study was to assess the relationship between the Romberg test, the Wii Fit basic balance test (WBBT), and the composite scores on the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) test in a sample of athletes with concussions. Methods: 55 post-concussed athletes (40 male) completed the Romberg Test (RT) (−/+), the WBBT, and ImPACT test. Wii Fit basic balance test performance was operationalized as the number of successfully completed trials (of 5 trials of increasing difficulty) within 30 seconds. Pearson’s and point-biserial correlations examined univariate associations among the variables. Results: The RT and WBBT were not significantly related (r = −0.029, p = 0.832). The RT weakly correlated with ImPACT impairment scores (r= 0.26, p= 0.041), whereas WBBT the number of trials did not (r = − 0.20, p = 0.155). Romberg Test scores were significantly correlated with ImPACT Visual Processing Speed Score (r = 0.27, p = 0.036) and Reaction Time score (r = 0.34, p = 0.006). In contrast, WBBT trials were significantly correlated with the ImPACT Visual Memory Score (r = − 0.41, p = 0.003). Conclusions: These results suggest that the WBBT and RT assess unique aspects of postural control. The RT may relate directly to single sensory cognitive and motor processing, while the WBBT may relate to multi-sensory visually driven cognitive and motor processing. Relevance for patients: Clinical balance tests could point to different cognitive impairments post-concussion

Candida albicans colonization and dissemination from the murine gastrointestinal tract : the influence of morphology and Th17 immunity

This article is protected by copyright. All rights reserved. This work was supported by the Wellcome Trust (086558, 080088, 102705), a Wellcome Trust Strategic Award (097377) and a studentship from the University of Aberdeen. D.K. was supported by grant 5R01AI083344 from the National Institute of Allergy and Infectious Diseases and by a Voelcker Young Investigator Award from the Max and Minnie Tomerlin Voelcker Fund.Peer reviewedPublisher PD

Exploring the synthesis and coordination chemistry of pentafluorophenylcopper : organocopper polyanions and coordination networks

[CuC6F5]4 is a thermally stable and soluble compound with suitable reactivity for synthetic applications in organic and inorganic chemistry. Here the synthesis of [CuC6F5]4 is explored in different solvents and followed by in situ 19F NMR spectroscopy. The importance of solvent choice during the synthesis from Grignard reagent C6F5MgBr is highlighted, with a range of magnesium cuprate species identified and isolated when THF is used as solvent (rather than Et2O), including [Cu(C6F5)2]− and the remarkable organocopper polyanion ([Cu5(C6F5)7]2–)∞. The coordination chemistry of [CuC6F5]4 with 1,4-dioxane is investigated in solution and in the solid state, with an extended coordination network, [CuC6F5]4(dioxane), structurally resolved for the first time. This structure reveals interwoven linear and zig-zag chains featuring dioxane donors unusually coordinating to adjacent Cu sites of some of the [CuC6F5]4 tetramers

Postfledging Survival, Movements, and Dispersal of Ring Ouzels (Turdus torquatus)

We thank Invercauld Estate for cooperation with access to Glen Clunie. S. Redpath, J. Wilson, and S. Roos provided valuable comments on the manuscript. This study was funded by the Royal Society for the Protection of Birds, Scottish Natural Heritage, and the Cairngorms National Park Authority. J.L.L. was supported by the Natural Environment Research Council.Peer reviewedPublisher PD