Position Locking for Permanent Magnet Synchronous Machine Propeller Drives in Drones by Hall-Effect Sensor-Assisted Nonlinear Observer

The paper presents a hall-effect sensor-assisted non-linear observer-based solution for position locking of a surface-mounted permanent magnet synchronous motor (SMPMSM) propeller drive in drone applications. The purpose of the position locking is to ensure a fixed motor position at the landing instant to avoid mechanical damage to the propeller. To evaluate the proposed solution, the position locking sequence of the motor drive is studied for two cases, implemented with two different state machines. The first case is relying on an encoder to provide the position feedback signal and serves as a reference for assessing the performance of the proposed solution based on the position estimate from the hall-effect sensor-assisted nonlinear observer. Experimental results show how the proposed solution can provide sufficient performance of position locking without the encoder.Position Locking for Permanent Magnet Synchronous Machine Propeller Drives in Drones by Hall-Effect Sensor-Assisted Nonlinear ObserveracceptedVersio

Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures

Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo

Position Control and Locking of Permanent Magnet Synchronous Motor for Propeller Drives in Drones

De siste årene har etterspørselen etter posisjoneringsløsninger for propelldrift i droner økt i industrien, med to velkjente motorapplikasjoner, fremdriftsmotorer og vertikal take-off og landings motorer. Hensikten med posisjoneringen i fremdriftsmotorer for fastvingede ubemannede luftfartøyer er å sikre en trygg motorposisjon ved landingsøyeblikket. Siden luftfartøyene er designet med et lavt landingsutstyr for å redusere luftmotstanden og øke varigheten, krever det at propellen plasseres i en horisontal posisjon for å unngå mekanisk skade på propellbladene hvis den treffer bakken. For vertikale take-off og landingsmotorer er posisjonering nødvendig for å redusere luftmotstanden produsert av propellene når de ikke er parallell med kursvinkelen. Hvis mer av overflatearealet til propellbladene er eksponert i lengderetningen av luftfartøyet, bidrar det til mer luftmotstand som igjen bidrar til redusert varighet for dronen under flygningen. Denne oppgaven presenterer fire tilstandsmaskiner for posisjonskontroll og posisjonslåsing av en overflatemontert permanentmagnet synkron motor for propelldrift. Hvor posisjoneringsmetodene er enten med en proporsjonal-integral-derivert kontroller og en enkoder som tilbakekobling for posisjonskontroll, eller med en hall-effekt sensor som tilbakekobling og med en konstant strøm i motorfasene for posisjonslåsing. I tillegg anvender en av posisjonslåsemetodene et posisjonsestimat som tilbakekobling med en implementert hall-effekt sensorassistert ulineær observatør for å muliggjøre posisjonslåsing i mer enn én fast mekanisk posisjon. De eksperimentelle resultatene viser hvordan de foreslåtte løsningene kan gi tilstrekkelig ytelse både med og uten enkoder, og er utført med en vindforstyrrelse for å kunne vurdere ytelsen nært et reelt scenario, og sammenlignet opp mot de to nevnte motorapplikasjonene

Volatility forecasting with Twitter message volume - Improving forecasting ability of the Heterogenous Autoregressive model of Realized Volatility

We test the predictive power of Twitter message volume on realized volatility in a panel of 22 companies from S&P 100. The relationship is tested using OLS regression, with Newey-West standard errors. The forecasting ability of the two best performing Twitter variables is tested in models inspired by the Heterogenous Autoregressive model of Realized Volatility. We employ the Two-Scales Estimator (TSE) to achieve more precise estimates of realized volatility. TSE takes advantage of high-frequency return data, while simultaneously correcting for microstructure noise. Findings indicate a relationship between Twitter message volume and realized volatility, made most explicit by employing variables that only contain messages accumulated outside of trading hours. Twitter messages containing cashtags were found to hold greater predictive power compared to messages containing company name mentions. However, a model containing both Twitter variables were superior in terms of forecasting ability. Company name messages were found to explain systematic risk, while cashtag messages were found to explain idiosyncratic risk

The impact of TiO2 nanoparticles on uptake and toxicity of benzo(a)pyrene in the blue mussel (Mytilus edulis)

Nanoparticles are emerging contaminants of concern. Knowledge on their environmental impacts is scarce, especially on their interactive effects with other contaminants. In this study we investigated effects of titanium dioxide nanoparticles (TiO2NP) on the blue mussel (Mytilus edulis) and determined their influence on the bioavailability and toxicity of benzo(a)pyrene (B(a)P), a carcinogenic polyaromatic hydrocarbon (PAH). Blue mussels were exposed to either TiO2NP (0.2 and 2.0 mg L− 1) or B(a)P (20 μg L− 1) and to the respective combinations of these two compounds. Aqueous contaminant concentrations, the uptake of Ti and B(a)P into mussel soft tissue, effects on oxidative stress and chromosomal damage were analyzed. The uncoated TiO2NP agglomerated rapidly in the seawater. The presence of TiO2NP significantly reduced the bioavailability of B(a)P, shown by lowered B(a)P concentrations in exposure tanks and in mussel tissue. The activities of antioxidant enzyme superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) were impacted by the various exposure regimes, indicating oxidative stress in the contaminant exposure groups. While SOD activity was increased only in the 0.2TiO2NP exposure group, CAT activity was enhanced in both combined exposure groups. The GPx activity was increased only in the groups exposed to the two single compounds. In hemocytes, increased chromosomal damage was detected in mussels exposed to the single compounds, which was further increased after exposure to the combination of compounds. In this study we show that the presence of TiO2NP in the exposure system reduced B(a)P uptake in blue mussels. However, since most biomarker responses did not decrease despite of the lower B(a)P uptake in combined exposures, the results suggest that TiO2NP can act as additional stressor, or potentially alters B(a)P toxicity by activation