A review of saliency-based sensorless control methods for alternating current machines

Operation of model-based sensorless control of Alternating Current machines at low and zero speeds is unreliable and can fail. To overcome the limitations of sensorless control at low speeds, several alternative techniques have been developed to estimate speed and position. These are mainly based on detecting machine saliencies by measuring the response of the current to some form of voltage injection. This paper discusses injection methods, machine saliencies, and techniques used to extract speed and position that are applicable to both induction machines and permanent magnet synchronous motors.peer-reviewe

La dimensión de género en el sistema de pensiones de capitalización individual, a la luz de la reforma previsional de la Ley 20.255 chilena

41 p.La presente memoria se fundamenta en analizar las medidas que establece la Reforma Previsional, en relación directa a la dimensión de género con el sistema de pensiones. El objetivo principal de este trabajo investigativo será descubrir, si la reforma de la Ley 20.255 soluciona la desigualdad de género en el sistema de capitalización individual con las medidas implementadas o si estas son inútiles o insuficientes. Para cumplir con este objetivo, utilizaremos una investigación jurídico dogmática, ya que buscamos verificar la utilidad de la norma al contrastarla con los hechos que la contextualizan, apoyada en la investigación interpretativo-sociológico de la normativa vigente, toda vez que sea necesario analizarla en su contexto sociocultural, para verificar sus efectos prácticos en las personas./ABSTRACT: This report is based on analyzing the measures provided for Pension Reform, in direct relation to the gender dimension in the pension system. The main objective of this research work is to discover if the reform of Law 20,255 addresses gender inequality in the individual capitalization system with the implemented measures or if these are useless or insufficient. To accomplish this goal, we will use a dogmatic method of legal research as we seek to verify the usefulness of the standard to compare them with the facts that put it in context, supported by sociological interpretative research of existing legislation, each time it is necessary to analyze it in its socio-cultural context, to verify its practical effects on people

Sensorless control of AC machines for low and zero speed operation without additional test signal injection

This work considers the sensorless control of AC machines for the low and zero speed operation range. Two novel techniques have been developed that use the inherit nature of the inverter PWM to estimate the rotor position of the machine. The inherent back EMF and the saliency of AC machines can be utilized to identify the rotor/flux position. The zero vector current derivative (ZVCD) technique for permanent magnet synchronous machines (PMSM) utilizes both of these effects. No additional test signals are injected into the machine and the difficulty in sensing the machine terminal voltage at low speed is eased. Only three standard current transducers are used in the drive system. For the position/ speed estimator only the machine current derivative during the relatively long (at low speed) zero voltage vectors is used for obtaining the rotor position. Practical results show the operation of the drive at several torque and speed conditions including stand still. A further method has been developed for the sensorless control of induction machines. The high frequency harmonics present in a PWM inverter drive system can be used to detect an equivalent impendence saliency that shows modulation due to rotor/ flux position saliency. The proposed method focuses particularly on the extraction of spatial saliency modulation due to rotor bar slotting effect, which can be used to determine the mechanical rotor position. No additional signal injection is required; the method simply employs some of the inherent PWM carrier harmonics

Who benefits from universal child care? Estimating marginal returns to early child care attendance

We examine heterogeneous treatment effects of a universal child care program in Germany by exploiting variation in attendance caused by a reform that led to a large expansion staggered across municipalities. Drawing on novel administrative data from the full population of compulsory school entry examinations, we find that children with lower (observed and unobserved) gains are more likely to select into child care than children with higher gains. Children from disadvantaged backgrounds are less likely to attend child care than children from advantaged backgrounds but have larger treatment effects because of their worse outcome when not enrolled in child care

Can Financial Incentives Reduce the Baby Gap? Evidence from a Reform in Maternity Leave Benefits

To assess whether earnings-dependent maternity leave positively impacts fertility and narrows the baby gap between high educated (high earning) and low educated (low earning) women, I exploit a major maternity leave benefit reform in Germany that considerably increases the financial incentives for higher educated and higher earning women to have a child. In particular, I use the large differential changes in maternity leave benefits across education and income groups to estimate the effects on fertility up to 5 years post reform. In addition to demonstrating an up to 22% increase in the fertility of tertiary educated versus low educated women, I find a positive, statistically significant effect of increased benefits on fertility, driven mainly by women at the middle and upper end of the education and income distributions. Overall, the results suggest that earnings-dependent maternity leave benefits, which compensate women commensurate with their opportunity cost of childbearing, could successfully reduce the fertility rate disparity related to mothers’ education and earnings

Sensorless control of AC machines for low and zero speed operation without additional test signal injection

This work considers the sensorless control of AC machines for the low and zero speed operation range. Two novel techniques have been developed that use the inherit nature of the inverter PWM to estimate the rotor position of the machine. The inherent back EMF and the saliency of AC machines can be utilized to identify the rotor/flux position. The zero vector current derivative (ZVCD) technique for permanent magnet synchronous machines (PMSM) utilizes both of these effects. No additional test signals are injected into the machine and the difficulty in sensing the machine terminal voltage at low speed is eased. Only three standard current transducers are used in the drive system. For the position/ speed estimator only the machine current derivative during the relatively long (at low speed) zero voltage vectors is used for obtaining the rotor position. Practical results show the operation of the drive at several torque and speed conditions including stand still. A further method has been developed for the sensorless control of induction machines. The high frequency harmonics present in a PWM inverter drive system can be used to detect an equivalent impendence saliency that shows modulation due to rotor/ flux position saliency. The proposed method focuses particularly on the extraction of spatial saliency modulation due to rotor bar slotting effect, which can be used to determine the mechanical rotor position. No additional signal injection is required; the method simply employs some of the inherent PWM carrier harmonics

On the range equation for a hybrid-electric aircraft

This paper proposes a new range equation for hybrid-electric aircraft. The paper revisits the theory of the range equation for a hybrid-electric aircraft with constant power split published earlier in the literature and proposes a new efficiency-based definition of the degree of hybridization (φ), one which includes the efficiencies of the electric or fuel-powered drivetrain. The paper shows that the efficiencies of the respective drivetrains play a significant role in the range estimation of the hybrid-electric aircraft. The paper makes use of a case study to show the relationship between battery energy density, powertrain efficiency and modification in the definition of the degree of hybridization φ with aircraft range. We show that for every aircraft design, there is a battery energy density threshold, for which the aircraft range becomes independent of the degree of hybridization. Below this threshold, the range decreases with an increase in the degree of hybridization. Conversely, beyond this threshold, the aircraft range increases with the degree of hybridization. Our study finds that the new definition of φ has shifted this threshold significantly upwards compared to earlier publications in the literature. This makes the design of an aircraft with a high degree of hybridization less optimistic.peer-reviewe

Space modulation profile modelling for steer-by-wire SMPMSM

This paper presents a sensorless estimation algorithm for steer-by-wire applications based on the injection of a high-frequency rotating voltage. Enhancement to the basic sensorless algorithm through SMP look-up tables is proposed. The improved observer was simulated in MATLAB for a 12 V RMS 400 W permanent magnet synchronous machine (PMSM).peer-reviewe

Prevalence and factors associated with exposure to second-hand smoke (SHS) among young people: a cross-sectional study from The Gambia

Background: Annually 600,000 deaths are attributed to exposure of non-smokers to second-hand smoke (SHS). These include 165,000 among children, about 60% of which occur in Africa and South-East Asia. In 2011 only four countries in the African region had comprehensive smoke-free legislation covering all public places. Given the increasing prevalence of smoking in many low income countries, preventing exposure to SHS is an urgent public health priority, particularly in sub-Sahara Africa. Objectives: The objective of this study is to obtain a reliable and nationally representative estimate of the prevalence of exposure to SHS, and to identify the major risk factors among young people in The Gambia. Settings and methods: We used two-stage cluster random sampling to select students in secondary schools throughout The Gambia, and a self-administered questionnaire to collect data on demographic characteristics and detailed indicators of exposure to SHS. Results: Of the 10,392 eligible students, 10,289 (99%; 55% girls and 44% boys, age 12-20 years) participated. The proportion of students reporting any exposure to SHS was 97.0%, (enclosed public places 59.2%, outdoor public places 61.4%, school 2l.3% and home 38.2%), with 96.4% reporting some exposure outside the home. Exposure to SHS in the home was more common in girls and among older students. Parental education, living with parents and being sent to purchase cigarettes were associated with exposure to SHS both within and outside the home. More than 50% of students supported public smoking ban in both enclosed and outdoor public places. About 35% of students were unaware of the harmful effects of exposure to SHS. Conclusions: Exposure to SHS is highly prevalent among students in the Gambia, and occurs mostly outside of the home. Interventions to reduce SHS exposure in students are urgently needed

Quality Prediction in Directed Energy Deposition Using Artificial Neural Networks Based on Process Signals

The Directed Energy Deposition process is used in a wide range of applications including the repair, coating or modification of existing structures and the additive manufacturing of individual parts. As the process is frequently applied in the aerospace industry, the requirements for quality assurance are extremely high. Therefore, more and more sensor systems are being implemented for process monitoring. To evaluate the generated data, suitable methods must be developed. A solution, in this context, was the application of artificial neural networks (ANNs). This article demonstrates how measurement data can be used as input data for ANNs. The measurement data were generated using a pyrometer, an emission spectrometer, a camera (Charge-Coupled Device) and a laser scanner. First, a concept for the extraction of relevant features from dynamic measurement data series was presented. The developed method was then applied to generate a data set for the quality prediction of various geometries, including weld beads, coatings and cubes. The results were compared to ANNs trained with process parameters such as laser power, scan speed and powder mass flow. It was shown that the use of measurement data provides additional value. Neural networks trained with measurement data achieve significantly higher prediction accuracy, especially for more complex geometries