Carrier-Signal Selection for Sensorless Control of PM Synchronous Machines at Zero and Very Low Speeds

This paper compares pulsating- and rotating-vector carrier-signal injection for self-sensing (or sensorless) control of permanent-magnet synchronous machines (PMSMs). The main focus of this paper is the evaluation of estimation errors due to the physical nonideal attributes of both the machine and the inverter. Initial-position and magnet-polarity estimations are analyzed as well. Transient response and signal processing for both techniques are discussed for completeness. The theoretical analysis is supported by experimental and simulation evidence obtained using interior PMSMs.      

Chemical Ecology of Cave-Dwelling Millipedes: Defensive Secretions of the Typhloiulini (Diplopoda,Julida, Julidae)

Cave animals live under highly constant ecological conditions and in permanent darkness, and many evolutionary adaptations of cave-dwellers have been triggered by their specific environment. A similar “cave effect” leading to pronounced chemical interactions under such conditions may be assumed, but the chemoecology of troglobionts is mostly unknown. We investigated the defensive chemistry of a largely cave-dwelling julid group, the controversial tribe “Typhloiulini”, and we included some cave-dwelling and some endogean representatives. While chemical defense in juliform diplopods is known to be highly uniform, and mainly based on methyl- and methoxy-substituted benzoquinones, the defensive secretions of typhloiulines contained ethyl-benzoquinones and related compounds. Interestingly, ethyl-benzoquinones were found in some, but not all cave-dwelling typhloiulines, and some non-cave dwellers also contained these compounds. On the other hand, ethyl-benzoquinones were not detected in troglobiont nor in endogean typhloiuline outgroups. In order to explain the taxonomic pattern of ethyl-benzoquinone occurrence, and to unravel whether a cave-effect triggered ethyl-benzoquinone evolution, we classed the “Typhloiulini” investigated here within a phylogenetic framework of julid taxa, and traced the evolutionary history of ethyl-benzoquinones in typhloiulines in relation to cave-dwelling. The results indicated a cave-independent evolution of ethyl-substituted benzoquinones, indicating the absence of a “cave effect” on the secretions of troglobiont Typhloiulini. Ethyl-benzoquinones probably evolved early in an epi- or endogean ancestor of a clade including several, but not all Typhloiulus (basically comprising a taxonomic entity known as “Typhloiulus sensu stricto”) and Serboiulus. Ethyl-benzoquinones are proposed as novel and valuable chemical characters for julid systematics.     

Runtime and energy constrained work scheduling for heterogeneous systems

The Journal of Supercomputing - Heterogeneous hardware systems consisting of CPUs and different types of accelerators are wide-spread nowadays for large supercomputers as well as smaller cluster...     

Modeling and Adaptive Decoupling of High-Frequency Resistance and Temperature Effects in Carrier-Based Sensorless Control of PM Synchronous Machines

This paper analyzes the effects of the high-frequency resistances in saliency tracking-based sensorless control methods of permanent-magnet synchronous machines (PMSMs). A high-frequency model of the PMSM, including stator high-frequency resistance, is presented. From this model, potential sources of error in the estimated position due to the high-frequency resistances are analyzed, and their compensation by means of an adaptive decoupling mechanism is proposed. This paper also addresses the influence and compensation of temperature effects in carrier-signal-injection-based sensorless techniques.      

Sequential variable neighborhood descent variants: an empirical study on the traveling salesman problem

In a single local search algorithm, several neighborhood structures are usually explored. The simplest way is to define a single neighborhood as the union of all predefined neighborhood structures; the other possibility is to make an order (or sequence) of the predefined neighborhoods, and to use them in the first improvement or the best improvement fashion, following that order. In this work, first we classify possible variants of sequential use of neighborhoods and then, empirically analyze them in solving the classical traveling salesman problem (TSP). We explore the most commonly used TSP neighborhood structures, such as 2‐opt and insertion neighborhoods. In our empirical study, we tested 76 different such heuristics on 15,200 random test instances. Several interesting observations are derived. In addition, the two best of 76 heuristics (used as local searches within a variable neighborhood search) are tested on 23 test instances taken from the TSP library (TSPLIB). It appears that the union of neighborhoods does not perform well.     

Saliency-Tracking-Based Sensorless Control of AC Machines Using Structured Neural Networks

The focus of this paper is the use of structured neural networks for sensorless control of ac machines using carrier-signal injection. Structured neural networks allow effective compensation of saturation-induced saliencies as well as other secondary saliencies. In comparison with classical compensation methods, such as lookup tables, this technique has advantages such as a physics-based structure, general scalability, reduced size and complexity, and correspondingly reduced commissioning time. When compared with traditional neural networks, structured neural networks are simpler, physically insightful, less computationally intensive, and easier to train. All make the proposed method an improved implementation for sensorless drives     

clusterCL: comprehensive support for multi-kernel data-parallel applications in heterogeneous asymmetric clusters

Heterogeneous cluster systems consisting of CPUs and different kinds of accelerators have become mainstream in HPC. Programming such systems is a difficult task and requires addressing manifold challenges that stem from the intricate composition of such systems and peculiarities of scientific applications. A broad range of obstacles preventing efficient execution have to be considered and dealt with properly. In this paper, we propose a systematic approach and a framework that is capable of providing comprehensive support for running data-parallel applications in heterogeneous asymmetric clusters. Our implementation provides work partitioning and distribution by ensuring workload balance in the cluster while handling of partitioning-induced communication and synchronization in a transparent way. In our experimental section, we choose 11 representative scientific applications from different domains to evaluate our approach. Experimental results show a strong speedup and workload balance for different cluster configurations.

     

Less is more approach: basic variable neighborhood search for the obnoxious p‐median problem

The goal of the less is more approach (LIMA) for solving optimization problems that has recently been proposed in Mladenovi? et al. (2016) is to find the minimum number of search ingredients that make a heuristic more efficient than the currently best. In this paper, LIMA is successfully applied to solve the obnoxious p‐median problem (OpMP). More precisely, we developed a basic variable neighborhood search for solving the OpMP, where the single search ingredient, the interchange neighborhood structure, is used. We also propose a new simple local search strategy for solving facility location problems, within the interchange neighborhood structure, which is in between the usual ones: first improvement and best improvement strategies. We call it facility best improvement local search. On the basis of experiments, it appeared to be more efficient and effective than both first and best improvement. According to the results obtained on the benchmark instances, our heuristic turns out to be highly competitive with the existing ones, establishing new state‐of‐the‐art results. For example, four new best‐known solutions and 133 ties are claimed in testing the set with 144 instances.     

Analysis of the Measurement System and Optimization of the Measurement Procedure for Detection of Thermal Memory Effects by Photoacoustic Experiments

Experimental verification of thermal memory effects represents a challenge that is important from both fundamental and practical points of view. Recent theoretical studies suggest that the thermal memory effect should lead to thermal resonances in the modulation frequency characteristics of photoacoustic response. Therefore, studies of thermal resonances in photoacoustic response represent an alternative for detection of the thermal memory effect and measurement of thermal memory properties. Since the resonances were not observed, this paper analyzes standard measurement setups and shows that the experimental technique should be optimized to provide a better chance of detection of thermal memory effects by photoacoustic measurements. The results show that a proper selection of modulation frequencies and the knowledge of the approximate transfer function of the electronic part of the photoacoustic measurement system are prerequisites for detection of thermal resonances in the modulation frequency characteristics of photoacoustic response.