A New Approach to Better Low-Cost MEMS IMU Performance Using Sensor Arrays

Over the past decade and a half, the combination of low-cost, lightweight micro-electro-mechanical sensors (MEMS) technology and multisensor integration has enabled inertial sensors to be deployed over a much wider range of navigation applications [1]. Examples include pedestrian dead-reckoning using step detection technology [2, 3], aiding of GNSS signal tracking during jamming [4, 5], and simultaneous localisation and mapping (SLAM) using radio signals [6]. However, for best performance, a MEMS inertial measurement unit (IMU) must be calibrated in the laboratory prior to use, which increases the cost by more than $1000 per unit. In this paper, we examine and present a range of techniques which use an array of inexpensive MEMS sensors to improve the performance of a MEMS IMU without requiring a full calibration prior to use. As the cost of calibration of a high-performance MEMS IMU far outweighs the cost of the hardware, there is considerable scope to improve the performance by adding additional sensors, before the cost of the IMU reaches that of a laboratory calibrated equivalent. Combining MEMS IMUs in an array has been studied before. However, the most common approach was simply to take an average of the input of several identical sensors [7]. If the sensor errors were independent, this could be expected to improve performance by a factor of root-n where, n is the number of IMUs combined. In this paper more sophisticated techniques are investigated that use knowledge of the sensor characteristics to obtain better performance. Three different properties of MEMS sensors may potentially be exploited: 1) The common-mode errors of different sensors of the same design; 2) The different characteristics of in-plane and out-of-plane sensors; and 3) The complementary properties of MEMS sensors with different dynamic ranges. In [8], it is shown that different individual sensors of the same design exhibit similar bias variation with temperature and that improved accuracy may be obtained by differencing the outputs of two gyroscopes mounted with their sensitive axes in opposing directions. Here, this approach will be independently verified and the performance benefits assessed with a range of different MEMS accelerometers and gyros, including Bosch BMA180 accelerometers, Analogue Devices ADXL345 accelerometers, ST Microtronics L3G4200D gyroscopes. Preliminary indications are that there is considerable common bias variation with temperature for the in-plane sensors of L3G4200D gyroscopes, and some common mode behaviour for the low-cost accelerometers. The second idea presented is exploiting the differences between the in-plane and out-of-plane axis outputs of single-chip inertial sensor triads, to improve the performance of an array-based IMU. Early experiment s point to considerable differences between the two which could markedly affect navigation performance. Both accelerometer and gyro triads can exhibit smaller errors from the in-plane sensors than from the out-of-plane sensors. Therefore, experiments were conducted using mutually-perpendicular arrays of accelerometer and gyro triads to determine whether better performance could be obtained using only the in-plane sensors. The third idea is to combine the outputs of MEMS sensors with different dynamic ranges to exploit the lower noise exhibited by some lower-dynamic-range sensors compared to their higher-dynamic-range counterparts. The sensor outputs are thus weighted according to the platform dynamics. That is, predominantly using the high-precision sensor when dynamics are low and using the full-range sensor when the dynamics are high. Several versions of this weighted signal combination will be presented and compared. Early indications are that there can be a significant benefit in this approach for some sensor designs, but not others. Finally, this paper will also examine the efficacy of a once-only static calibration on purchase, performed by the user instead of the supplier, for improving navigation performance. It is essential for a user-performed calibration that the physical movements required of the sensor are very simple and easily understood and completed, even if the underlying method is complex. To this end data, recorded on different days from an array of MEMS sensors within a precisely manufactured rapid prototyped ‘calibration cube’, will be analysed. These measurements are taken at precisely orthogonal angles of the cubes six faces, and allow the scale factor errors, biases and axes alignments of the accelerometers to be determined. The computed calibration corrections over several days will be compared to enable the efficacy of the one-time calibration technique to be assessed. The development of a full calibration routine will be the subject of future research. In summary, this paper will present several new methods for utilising the output of an array of low-cost sensors to improve the performance of a MEMS IMU, and also expands on methods proposed in existing research. As uncalibrated MEMS IMUs are of low performance there is a great potential for new applications if the performance can be improved closer to the level of those which are factory calibrated. / References [1] Groves, P. D., Principles of GNSS, inertial, and multi-sensor integrated navigation systems, Second Edition, Artech House, 2013. [2] Gustafson, D., J. Dowdle, and K. Flueckiger, “A Deeply Integrated Adaptive GPS-Based Navigator with Extended Range Code Tracking,” Proc. IEEE PLANS 2000. [3] Groves, P. D., C. J. Mather and A. A. Macaulay, “Demonstration of Non-Coherent Deep INS/GPS Integration for Optimized Signal to Noise Performance,” Proc. ION GNSS 2007. [4] Ma, Y., W. Soehren, W. Hawkinson, and J. Syrstad, "An Enhanced Prototype Personal Inertial Navigation System," Proc. ION GNSS 2012. [5] Groves, P. D., et al., “Inertial Navigation Versus Pedestrian Dead Reckoning: Optimizing the Integration,” Proc. ION GNSS 2007. [6] Faragher, R. M., C. Sarno, and M. Newman, “Opportunistic Radio SLAM for Indoor Navigation using Smartphone Sensors,” Proc. IEEE/ION PLANS 2012. [7] Bancroft, J. B., and G. Lachapelle, “Data fusion algorithms for multiple inertial measurement units,” Sensors, Vol. 11, No. 7, 2011, pp. 6771-6798. [8] Yuksel, Y., N. El-Sheimy, N., and A. Noureldin, “Error modelling and characterization of environmental effects for low cost inertial MEMS units,” Proc. IEEE/ION PLANS 2010

La habilidad en el cálculo en los adultos con síndrome de Down es una cuestión de calidad de vida

Se acepta ampliamente que la capacidad para calcular resulta crítica en el mundo de los adultos de la comunidad general, y que ese es el caso igualmente para los que tienen síndrome de Down. Este trabajo informa sobre algunos de los resultados de un estudio que plantea esta pregunta objeto de investigación: ¿Cuál es la justificación para el desarrollo de la capacidad de calcular en los adultos con síndrome de Down? La investigación sobre esta pregunta nos condujo hacia la búsqueda de un marco que sirviera de base al desarrollo permanente de la capacidad de calcular. La investigación se realizó por el método de estudio de casos. Se observó e investigó a cinco adultos con síndrome de Down, en dos situaciones distintas para cada uno. Se analizaron los datos para identificar las conexiones que tenían en relación con el modelo de calidad de vida. El estudio ilustra cómo se puede utilizar este enfoque de la calidad de vida para justificar y guiar el desarrollo de la capacidad para el cálculo a lo largo de la vida. Los datos obtenidos en el estudio de los casos enlazaron la capacidad para el cálculo con la calidad de vida en los principios de los contextos personales, la variabilidad, las perspectivas a lo largo de la vida, los valores, las elecciones y el control personal, las percepciones y la autoimagen. Se concluye que los principios de la calidad de vida pueden proporcionar un marco para el desarrollo de la capacidad de cálculo en el contexto de la edad adulta de las personas con síndrome de Down. Prepararlas para que cubran las necesidades de utilización del cálculo en una adultez larga y satisfactoria significa que ha de iniciarse pronto en la niñez, proseguir en la etapa escolar mediante la enseñanza de los correspondientes conceptos y habilidades aritméticas, y ser modificado y refinado a lo largo de la vida adulta mediante la utilización de un plan que desarrolle esa capacidad para utilizar los números. En esta empresa los cuidadores y los profesionales han de adoptar su papel de profesores en interacción con el contexto

Soroban: Attributing latency in virtualized environments

Applications running in the cloud have highly-variable response times due to the lack of perfect performance isolation from other services served by common infrastructure. In particular, response latency when executing on a loaded hypervisor or in a container is substantially higher than uncontested bare-metal performance. Whilst efforts to increase performance isolation continue, we present Soroban, a framework for attributing latency to either the cloud provider or their customer. Soroban allows cloud providers to instrument commonly used programs, such as a web server to determine, for each request, how much of the latency is due to the cloud provider, or the consumer. We apply Soroban to a HTTP server and show that it identifies when the cause of latency is due to a provider-induced activity, such as underprovisioning a host, or due to the software run by the customer.This is the author accepted manuscript. The final version is available from USENIX. via https://www.usenix.org/conference/hotcloud15/workshop-program/presentation/sne

'Tumour volume' as a predictor of survival after resection of non-small-cell lung cancer (NSCLC)

Many factors have been individually related to outcome in populations of non-small-cell lung cancer (NSCLC) patients. Factors responsible for the outcome of an individual after surgical resection are poorly understood. We have examined the importance of 'tumour volume' in determining prognosis of patients following resection of NSCLC in a multivariate model. Cox's proportional hazard analysis was used to determine the relative prognostic significance of stage, patient age, gender, tumour cell-type, nodal score and estimated 'tumour volume' in 669 cases with NSCLC treated with surgical resection, of which 280 had died. All factors (except tumour cell-type, P = 0.33) were individually related to survival (P < 0.05). When examined together, survival time was significantly and independently related to 'tumour volume' and stage (P < 0.001), and other factors ceased to be significant. In cases with stage I or II tumours, risk of death was found to increase significantly with increasing estimated 'tumour volume' (23.8% relative increase in hazard to death per doubling of 'tumour volume', 95% confidence interval 13.2-35.2%, P < 0.001 stage I; P < 0.006 stage II). In cases with stage IIIa tumours this factor alone was the significant prognostic variable. In conclusion, an estimate of 'tumour volume' significantly improves prediction of prognosis for individual NSCLC patients with UICC stage I or II tumours

Achieving Practical and Accurate Indoor Navigation for People with Visual Impairments

Methods that provide accurate navigation assistance to people with visual impairments often rely on instrumenting the environment with specialized hardware infrastructure. In particular, approaches that use sensor networks of Bluetooth Low Energy (BLE) beacons have been shown to achieve precise localization and accurate guidance while the structural modifications to the environment are kept at minimum. To install navigation infrastructure, however, a number of complex and time-critical activities must be performed. The BLE beacons need to be positioned correctly and samples of Bluetooth signal need to be collected across the whole environment. These tasks are performed by trained personnel and entail costs proportional to the size of the environment that needs to be instrumented. To reduce the instrumentation costs while maintaining a high accuracy, we improve over a traditional regression-based localization approach by introducing a novel, graph-based localization method using Pedestrian Dead Reckoning (PDR) and particle filter. We then study how the number and density of beacons and Bluetooth samples impact the balance between localization accuracy and set-up cost of the navigation environment. Studies with users show the impact that the increased accuracy has on the usability of our navigation application for the visually impaired

Experimentally manipulated self-affirmation promotes reduced alcohol consumption in response to narrative information

Background: Health-risk information is increasingly being conveyed through accounts of personal experiences or narrative information. However, whether self-affirmation can enhance the ability of such messages to promote behavior change has yet to be established. Purpose: This study aims to test whether self-affirmation (a) promotes behavior change following exposure to narrative information about the risks of excessive alcohol consumption and (b) boosts message acceptance by increasing narrative engagement. Methods: In an experimental design, female drinkers (N = 142) reported their baseline alcohol consumption and were randomly allocated to condition (Self-Affirmation, Control). All participants next watched an extract of a genuine narrative piece in which the central character discussed her liver disease and its link with her previous alcohol consumption. Then, participants completed measures assessing engagement with the narrative and message acceptance. The primary outcome was alcohol consumption, assessed at 7-day follow-up. Results: Self-affirmed participants reported consuming significantly less alcohol at follow-up compared to baseline (mean 7-day decrease = 5.43 units); there was no change in alcohol consumption for the control group. Immediately post-manipulation, self-affirmed participants (vs. control) showed more message acceptance and reported greater engagement with the information. The impact of self-affirmation on message acceptance was mediated by narrative engagement. Conclusions: Self-affirmation can promote behavior change following exposure to health information, even when presented in narrative form

Work Hours and Self rated Health of Hospital Doctors in Norway and Germany. A comparative study on national samples

<p>Abstract</p> <p>Background</p> <p>The relationship between extended work hours and health is well documented among hospital doctors, but the effect of national differences in work hours on health is unexplored. The study examines the relationship between work hours and self rated health in two national samples of hospital doctors.</p> <p>Methods</p> <p>The study population consisted of representative samples of 1,260 German and 562 Norwegian hospital doctors aged 25-65 years (N = 1,822) who received postal questionnaires in 2006 (Germany) and 2008 (Norway). The questionnaires contained items on demography, work hours (number of hours per workday and on-call per month) and self rated subjective health on a five point scale - dichotomized into "good" (above average) and "average or below".</p> <p>Results</p> <p>Compared to Norway, a significantly higher proportion of German doctors exceeded a 9 hour work day (58.8% vs. 26.7%) and 60 hours on-call per month (63.4% vs. 18.3%). Every third (32.2%) hospital doctor in Germany worked more than this, while this pattern was rare in Norway (2.9%). In a logistic regression model, working in Norway (OR 4.17; 95% CI 3.02-5.73), age 25-44 years (OR 1.66; 95% CI 1.29-2.14) and not exceeding 9 hour work day and 60 hours on-call per month (OR 1.35; 95% CI 1.03-1.77) were all independent significant predictors of good self reported health.</p> <p>Conclusion</p> <p>A lower percentage of German hospital doctors reported self rated health as "good", which is partly explained by the differences in work time pattern. Initiatives to increase doctors' control over their work time are recommended.</p

The bornavirus-derived human protein EBLN1 promotes efficient cell cycle transit, microtubule organisation and genome stability.

It was recently discovered that vertebrate genomes contain multiple endogenised nucleotide sequences derived from the non-retroviral RNA bornavirus. Strikingly, some of these elements have been evolutionary maintained as open reading frames in host genomes for over 40 million years, suggesting that some endogenised bornavirus-derived elements (EBL) might encode functional proteins. EBLN1 is one such element established through endogenisation of the bornavirus N gene (BDV N). Here, we functionally characterise human EBLN1 as a novel regulator of genome stability. Cells depleted of human EBLN1 accumulate DNA damage both under non-stressed conditions and following exogenously induced DNA damage. EBLN1-depleted cells also exhibit cell cycle abnormalities and defects in microtubule organisation as well as premature centrosome splitting, which we attribute in part, to improper localisation of the nuclear envelope protein TPR. Our data therefore reveal that human EBLN1 possesses important cellular functions within human cells, and suggest that other EBLs present within vertebrate genomes may also possess important cellular functions