Field Oriented Sliding Mode Control of Surface-Mounted Permanent Magnet AC Motors: Theory and Applications to Electrified Vehicles

Permanent magnet ac motors have been extensively utilized for adjustable-speed traction motor drives, due to their inherent advantages including higher power density, superior efficiency and reliability, more precise and rapid torque control, larger power factor, longer bearing, and insulation life-time. Without any proportional-and-integral (PI) controllers, this paper introduces novel first- and higher-order field-oriented sliding mode control schemes. Compared with the traditional PI-based vector control techniques, it is shown that the proposed field oriented sliding mode control methods improve the dynamic torque and speed response, and enhance the robustness to parameter variations, modeling uncertainties, and external load perturbations. While both first- and higher-order controllers display excellent performance, computer simulations show that the higher-order field-oriented sliding mode scheme offers better performance by reducing the chattering phenomenon, which is presented in the first-order scheme. The higher-order field-oriented sliding mode controller, based on the hierarchical use of supertwisting algorithm, is then implemented with a Texas Instruments TMS320F28335 DSP hardware platform to prototype the surface-mounted permanent magnet ac motor drive. Last, computer simulation studies demonstrate that the proposed field-oriented sliding mode control approach is able to effectively meet the speed and torque requirements of a heavy-duty electrified vehicle during the EPA urban driving schedule

Pushing the Upper Limit of Nucleophilicity Scales by Mesoionic N-Heterocyclic Olefins

A series of mesoionic, 1,2,3-triazole-derived N-heterocyclic olefins (mNHOs), which have an extraordinarily electron-rich exocyclic CC-double bond, was synthesized and spectroscopically characterized, in selected cases by X-ray crystallography. The kinetics of their reactions with arylidene malonates, ArCH=C(CO2Et)2, which gave zwitterionic adducts, were investigated photometrically in THF at 20 °C. The resulting second-order rate constants k2(20 °C) correlate linearly with the reported electrophilicity parameters E of the arylidene malonates (reference electrophiles), thus providing the nucleophile-specific N and sN parameters of the mNHOs according to the correlation lg k2(20 °C)=sN(N+E). With 21<N<32, the mNHOs are much stronger nucleophiles than conventional NHOs. Some mNHOs even excel the reactivity of mono- and diacceptor-substituted carbanions. It is exemplarily shown that the reactivity parameters thus obtained allow to calculate the rate constants for mNHO reactions with further Michael acceptors and predict the scope of reactions with other electrophilic reaction partners including carbon dioxide, which gives zwitterionic mNHO-carboxylates. The nucleophilicity parameters N correlate linearly with a linear combination of the quantum-chemically calculated methyl cation affinities and buried volumes of mNHOs, which offers a valuable tool to tailor the reactivities of strong carbon nucleophiles

Signature of short-range van der Waals forces observed in Poisson spot diffraction with indium atoms

The phase of de Broglie matter waves is a sensitive probe for small forces. In particular, the attractive van der Waals force experienced by polarizable atoms in the close vicinity of neutral surfaces is of importance in nanoscale systems. It results in a phase shift that can be observed in matter-wave diffraction experiments. Here, we observe Poisson spot diffraction of indium atoms at submillimeter distances behind spherical submicron silicon dioxide particles to probe the dispersion forces between atoms and the particle surfaces. We compare the measured relative intensity of Poisson’s spot to theoretical results derived from first principles in an earlier communication and find a clear signature of the atom-surface interaction

Nonlinear Robust Control of Permanent Magnet Synchronous Motors With Applications to Hybrid Electric Vehicles

Environmental concerns are driving the automotive industry towards more sustainable and efficient forms of transportation such as electric vehicles. The electric drivetrains present in the various types of electric vehicles are much more efficient than traditional internal combustion engine drivetrains and produce fewer greenhouse gases. The most popular type of motor used in electric vehicle drivetrains is the permanent magnet synchronous motor. This can be attributed to its inherent high power density, large torque to weight ratio, and high reliability and efficiency. Advanced control techniques for permanent magnet synchronous motor drives must be developed in order to meet the high performance and efficiency demands of modern electric vehicles. Application of the nonlinear control method known as sliding mode control is the focus of this work. Both first order and higher order sliding mode methods are considered. These control methods provide robustness to modeling inaccuracies, internal parameter variations, and external disturbances. In addition to permanent magnet synchronous motors, the sliding mode control methods are also applied to the buck-boost type DC-DC converter. DC-DC converters have found extensive applications, ranging from consumer electronics to electric vehicles and smart grid synchronization. Computer simulation studies verify the efficacy of the proposed control techniques

OPTIMAL SIZE AND LOCATION OF CAPACITORS ON POWER DISTRIBUTION LINES

ABSTRACT Shunt capacitor banks are used on power distribution feeders to reduce losses and regulate the voltage level. The decrease in transmission line current also leads to an increase in the amount of demand that can be supplied without increasing the size of the conductors. In order to maximize the benefit of adding capacitor banks to the distribution feeders, the optimal size and location of the capacitors must be determined. This paper presents a novel optimal control approach to both regulate the voltage drop and reduce the copper loss. A cost function that penalizes both energy losses and voltage drop is developed. The optimal size and location of capacitors can be found using the optimal control solution. Computer simulation results are compared with existing methods of determining the optimal size and location of capacitors. Our approach improves on current methods by providing flexibility to both regulate voltage levels and reduce losses

Development and validation of brain target controlled infusion of propofol in mice.

Mechanisms through which anesthetics disrupt neuronal activity are incompletely understood. In order to study anesthetic mechanisms in the intact brain, tight control over anesthetic pharmacology in a genetically and neurophysiologically accessible animal model is essential. Here, we developed a pharmacokinetic model that quantitatively describes propofol distribution into and elimination out of the brain. To develop the model, we used jugular venous catheters to infuse propofol in mice and measured propofol concentration in serial timed brain and blood samples using high performance liquid chromatography (HPLC). We then used adaptive fitting procedures to find parameters of a three compartment pharmacokinetic model such that all measurements collected in the blood and in the brain across different infusion schemes are fit by a single model. The purpose of the model was to develop target controlled infusion (TCI) capable of maintaining constant brain propofol concentration at the desired level. We validated the model for two different targeted concentrations in independent cohorts of experiments not used for model fitting. The predictions made by the model were unbiased, and the measured brain concentration was indistinguishable from the targeted concentration. We also verified that at the targeted concentration, state of anesthesia evidenced by slowing of the electroencephalogram and behavioral unresponsiveness was attained. Thus, we developed a useful tool for performing experiments necessitating use of anesthetics and for the investigation of mechanisms of action of propofol in mice

Routinely randomize potential sources of measurement reactivity to estimate and adjust for biases in subjective reports

With the advent of online and app-based studies, researchers in psychology are making increasing use of repeated subjective reports. The new methods open up opportunities to study behavior in the field and to map causal processes, but they also pose new challenges. Recent work has added initial elevation bias to the list of common pitfalls; here, higher negative states (i.e., thoughts and feelings) are reported on the first day of assessment than on later days. This article showcases a new approach to addressing this and other measurement reactivity biases. Specifically, we employed a planned missingness design in a daily diary study of more than 1,300 individuals who were assessed over a period of up to 70 days to estimate and adjust for measurement reactivity biases. We found that day of first item presentation, item order, and item number were associated with only negligible bias: Items were not answered differently depending on when and where they were shown. Initial elevation bias may thus be more limited than has previously been reported or it may act only at the level of the survey, not at the item level. We encourage researchers to make design choices that will allow them to routinely assess measurement reactivity biases in their studies. Specifically, we advocate the routine randomization of item display and order, as well as of the timing and frequency of measurement. Randomized planned missingness makes it possible to empirically gauge how fatigue, familiarity, and learning interact to bias responses

Schematic of model creation methods.

<p>The first image represents the initial infusion used, which was delivered at a fixed rate. The second image shows that data collected from these experiments were fit and used to produce estimates of the pharmacokinetic parameters, as described in the methods. Third, these parameter estimates were used to calculate the infusion rate necessary to maintain a target brain concentration for the brain TCI experiments. After each experimental set, accuracy of TCI model was determined and fit was updated to incorporate all experimental findings. The methodology represented in images 2 and 3 was repeated until time-invariant and unbiased target brain concentration of propofol was maintained for at least 1 hour.</p