Speed and Torque Estimation of BLDC using DTC and Sliding Mode Observer

This paper presents speed and torque estimation for Brushless DC (BLDC) motors with non-sinusoidal back electromotive force using six switch inverter and DTC technique. The 180 conduction mode is the more popular method used for three-phase drives but here we use two-phase conduction mode. A simple approach is discussed n how to reduce ripples in the estimated torque at low frequency operation. A simple look-up table at a pre-defined sampling time is used to select the inverter voltage space vectors and the quasi-wave current is obtained. Estimation of electromagnetic torque for BLDC drives is the key issue and so sensor-less control method are used. The sliding mode observer estimates the back-EMF and generates torque, as under sliding mode observer error equation is reduced and it makes stability easier. Only the measurements of the stator currents is used in the estimation of back-EMF waveform. The electromagnetic torque and the rotor speed is estimated using values from Sliding Mode Observer. Fuzzy Gain Scheduling method is used to tune the parameters because this scheme uses human expertise on PID gain scheduling can be represented in fuzzy rules. Furthermore, better control performance can be expected in the proposed method than that of the PID controllers with fixed parameters and the gains of the sliding mode observer are tuned manually. The effectiveness of the proposed scheme is verified by using simulation results. Keywords: BLDC, DTC, Sliding Mode Observer(SMO), PID Controller, Fuzzy Gain Scheduling, Estimated Rotor speed, Estimated Torque, Estimated Back-EMF

A novel application of sustainable material sourcing and building performance monitoring: case study based approach.

In this research, a novel use of building materials and their impact on the building performance and its climatic adaptability is explored, based on a complex real word case study of a unique low energy sustainable building project. In particular, an innovative use of sycamore and its suitability as a structural and constructional timber has been investigated and reported, considering that is deemed not appropriate for structural applications by current standards. A research method of in-situ longitudinal study has been adopted, concentrating on the performance monitoring and assessment of its structural performance and conditions in which it might deteriorate. On the system level, the climatic adaptability of the building as a whole has been analysed via dynamic performance simulation and compared to the in-situ measurements. This was important in order to develop a holistic building performance monitoring strategy, but in particular, to understand the impact of building microclimate on the sycamore frame and hempcrete components of the external load-bearing wall. So far research has concluded that sycamore can be used as structural and constructional material in building design, but due attention has to be paid to construction detailing and provision of a breathable, low humidity environment with an effective resistance to decay and insect attack. This includes measures that ensure a low equilibrium moisture content conditions, effective ventilation provision and appropriate service class uses.N/

Green Manufacturing: Case Study using AHP and Grey Relation

Green manufacturing is cooperative manufacturing based on various hierarchy resources. Its important to get the optimum Cooperative enterprise scheme by analyzing, arranging and evaluating the manufacturing capabilities of Industries for Green manufacturing. The paper analyzes correlation between five industries in the context of green manufacturing, with the help of relation matrix which is based on grey relation theory and AHP method. The paper analyses the environmental actions according to Green product design, Green design of raw material, Green process, Green Technology, Green packaging Material and Green Packaging design

Visual Field Mapping by Tangent Screen and Humphrey Perimetry: A Comparative Study

Background and Objectives: (a) To compare manual tangent screen perimetry and automated Humphrey perimetry for visual field testing, and (b) to analyze whether manual tangent screen perimetry still has a role or it should be replaced by computerized automated Humphrey perimetry in physiology labs and clinical diagnostic settings.Methods: Study was done on 45 patients between 18 and 65 years of age that included 30 eyes of patients suffering from glaucoma/ other eye diseases giving rise to visual field defects, 5 eyes of patients suffering from neurological diseases and 10 eyes of normal subjects.All patients underwent perimetry examination by tangent screen at 1 meter distance (and 2 meter distance, if required) and automated Humphrey perimetry by Humphrey visual field analyzer (HFA) using 30-2 ‘white on white’ full threshold strategy. Tangent screen consists of black screen 2 meter square or 1 meter square. Accordingly, patient is seated at a distance of 2 meter or 1 meter respectively. A patient with organically constricted visual fields will show an increase in the size of the visual field when moved to a farther distance while a patient with functional visual field loss will often report the same absolute size of the field (tubular or gun-barrel field) to be consistent with their first field. This is clear evidence of functional visual field impairment.Results: Out of 45 patients, 29 were male and 16 were female. The age cases in the study ranged from 40-79 years with mean age of 60.70 years. Tangent screen perimetry was able to detect about 5 patients with early field defects and 15 patients with moderate/ advanced field defects. On the other hand, Humphrey automated perimetry was able to detect 10 patients with early field defects and 18 patients with moderate/ advanced field defects. While only 13.33% technicians preferred tangent screen perimetry, around three-fourths of the technicians found Humphrey automated perimetry more preferable. 91.11% technicians found HVF to be technically easier because the automated perimeter eliminates observer bias, is easier to perform and also overcomes the tedium of manual perimetry. Moreover, automated perimetry also uses quantified parameters while manual perimetry does not. On evaluating sensitivity and specificity of manual tangent screen perimeter using the Humphrey automated perimeter as the standard, the tests showed that the tangent screen perimeter had 75.75% sensitivity and 88.88% specificity. Since the mean time taken was more in automated perimetry: 474.5 sec, 474 sec and 459.9 sec versus 340.5 sec, 339.1 sec, and 339.1 sec in glaucoma, neurological and normal patients respectively; more patients-66% preferred tangent screen perimetry.Interpretation and Conclusions: Our results suggest that visual field testing with automated perimetry is superior to visual field testing with tangent screen perimetry. The automated perimeter picked up visual field defects in a larger number of eyes than the tangent screen perimeter. Visual field defects were more extensive on automated perimetry compared to tangent screen perimetry.The advantage of the HVF analyzer also lies in its ability to make use of quantified parameters like mean deviation and corrected pattern standard deviation to detect subtle worsening of visual field defect, with statistical level of confidence

Frequency shifts in noble-gas magnetometers

Polarized nuclei are a powerful tool in nuclear spin studies and in searches for beyond-the-standard model physics. Noble-gas comagnetometer systems, which compare two nuclear species, have thus far been limited by anomalous frequency variations of unknown origin. We studied the self-interactions in a $^3$He-$^{129}$Xe system by independently addressing, controlling and measuring the influence of each component of the nuclear spin polarization. Our results directly rule out prior explanations of the shifts, and demonstrate experimentally that they can be explained by species dependent self-interactions. We also report the first gas phase frequency shift induced by $^{129}$Xe on $^3$He.Comment: v.

PARIS: Personalized Activity Recommendation for Improving Sleep Quality

The quality of sleep has a deep impact on people's physical and mental health. People with insufficient sleep are more likely to report physical and mental distress, activity limitation, anxiety, and pain. Moreover, in the past few years, there has been an explosion of applications and devices for activity monitoring and health tracking. Signals collected from these wearable devices can be used to study and improve sleep quality. In this paper, we utilize the relationship between physical activity and sleep quality to find ways of assisting people improve their sleep using machine learning techniques. People usually have several behavior modes that their bio-functions can be divided into. Performing time series clustering on activity data, we find cluster centers that would correlate to the most evident behavior modes for a specific subject. Activity recipes are then generated for good sleep quality for each behavior mode within each cluster. These activity recipes are supplied to an activity recommendation engine for suggesting a mix of relaxed to intense activities to subjects during their daily routines. The recommendations are further personalized based on the subjects' lifestyle constraints, i.e. their age, gender, body mass index (BMI), resting heart rate, etc, with the objective of the recommendation being the improvement of that night's quality of sleep. This would in turn serve a longer-term health objective, like lowering heart rate, improving the overall quality of sleep, etc.Comment: 18 pages, 7 figures, Submitted to UMUAI: Special Issue on Recommender Systems for Health and Wellbeing, 202