The bio-inspired algorithms are novel, modern, and efficient tools for the design of electrical machines. However, from the mathematical point of view, these problems belong to the most general ...branch of non-linear optimization problems, where these tools cannot guarantee that a global minimum is found. The numerical cost and the accuracy of these algorithms depend on the initialization of their internal parameters, which may themselves be the subject of parameter tuning according to the application. In practice, these optimization problems are even more challenging, because engineers are looking for robust designs, which are not sensitive to the tolerances and the manufacturing uncertainties. These criteria further increase these computationally expensive problems due to the additional evaluations of the goal function. The goal of this paper is to give an overview of the widely used optimization techniques in electrical machinery and to summarize the challenges and open problems in the applications of the robust design optimization and the prospects in the case of the newly emerging technologies.
Since large power transformers are custom-made, and their design process is a labor-intensive task, their design process is split into different parts. In tendering, the price calculation is based on ...the preliminary design of the transformer. Due to the complexity of this task, it belongs to the most general branch of discrete, non-linear mathematical optimization problems. Most of the published algorithms are using a copper filling factor based winding model to calculate the main dimensions of the transformer during this first, preliminary design step. Therefore, these cost optimization methods are not considering the detailed winding layout and the conductor dimensions. However, the knowledge of the exact conductor dimensions is essential to calculate the thermal behaviour of the windings and make a more accurate stray loss calculation. The paper presents a novel, evolutionary algorithm-based transformer optimization method which can determine the optimal conductor shape for the windings during this examined preliminary design stage. The accuracy of the presented FEM method was tested on an existing transformer design. Then the results of the proposed optimization method have been compared with a validated transformer design optimization algorithm.
Two powerful and versatile code packages (Agros Suite and Ārtap) are presented for design and optimization of technical devices and systems. Agros Suite represents an environment for numerical ...solution of systems consisting of partial differential equations (PDEs) of the second order by a higher-order finite element method with a lot of further advanced features such as full adaptivity and selected optimization techniques. Ārtap is a robust design optimization toolbox that provides a simple and efficient programming environment for a wide-range of optimization methods, integrated and external PDE solvers and well-established machine learning tools. Both packages are described in a sufficient detail and their power is illustrated with solution of three problems from the domain of technical sciences.
This reprint contains fourteen chosen articles on robust design optimization of electrical machines and devices. Optimization is essential for the research and design of electromechanical devices, ...especially electrical machines. Finding optimal solutions may lead to cheaper and more efficient production of electrical machines. However, optimizing such a complex system as an electrical machine is a computationally expensive optimization problem, where many physical domains should be considered together. However, a good, practical design should be insensitive to parameter changes and the manufacturing tolerances. The collected papers show how modern artificial intelligence (AI) tools can be used for the robust design optimization of electric machines and electrical devices. The articles which are published in this Special Issue present the latest results of current research fields. Hopefully, the presented models and various application fields will provide useful information for researchers and professionals interested in these techniques themselves or who have other problems from different fields.
Optimization is an essential part of designing electrical machines and devices. Considering the uncertainties and tolerances from the beginning of the design process can lead to a more robust design ...and significantly reduce the number of waste products during the manufacturing process. However, the computational demand for these robust design optimization problems is amazingly high. This paper examines how the computational demand and the robustness of the results depend on the applied sensitivity metric. The multi-objective TEAM 35 benchmark problem has been used as the basis of the comparison. This optimization task aims to create a homogeneous magnetic field in a predefined coil region, which is insensitive to the positioning errors of the coil turns. The original definition of the problem uses a simple worst-case sensitivity metric calculated from the extreme values of the optimized turn parameters in the given tolerance range. This sensitivity metric has been replaced by Plackett–Burman, Box–Behnken, and Central Composite Design-based metrics. It was shown in this simple geometry that there is a significant difference between the resulting sensitivities. Nevertheless, Plackett–Burman and Central Composite Design provided the more accurate and consistent estimate of the sensitivity of the examined layouts, with a higher but still reasonable computation demand than the worst-case metric.
Previous research demonstrated that there are observable sex differences in developing muscle fatigue when mental task during fatiguing activity is present; however, there is no available review on ...this matter. Therefore, this review aimed to summarize the findings of previous studies investigating the effect of mental task on muscle fatigue in men and women. To conduct the review, we utilized searches using the electronic databases Web of Science, PubMed, Scopus, and EBSCO Cinahl Ultimate. The studies included had no limited publication date and examined the effects of mental task on muscle fatigue in a healthy adult population of any age. The evaluation was performed using the following criteria: time to failure, or subjective scale in various modifications (visual analog scale-VAS, rate of perceived effort-RPE, rate of perceived fatigue-RPF, rate of perceived discomfort-RPD). A total of seven studies met the set criteria, which were subsequently analyzed. Heavy mental task (more demanding math tasks) can reduce the time to failure for both men and women, with the reduction being more pronounced for women than for men. For light mental task (simple math tasks), no reduction in time to failure was observed to a great extent. The mental task in any of the included studies did not affect the subjective perception of fatigue, effort, discomfort, or pain. Although the studies investigating the effect of mental task on sex differences in muscle fatigability are limited, based on our findings we can assume that in jobs requiring heavier mental task, women may be more prone to the faster development of muscle fatigue; thus, employers might consider paying attention to the possibility of adequate rest.
Touch is one of the primary communication tools. Interestingly, the sensation of touch can also be experienced when observed in another person. Due to the system of mirror neurons, it is, in fact, ...being mapped on the somatosensory cortex of the observer. This phenomenon can be triggered not only by observing touch in another individual, but also by a mirror reflection of the contralateral limb. Our study aims to evaluate and localize changes in the intracerebral source activity via sLORETA imaging during the haptic stimulation of hands, while modifying this contact by a mirror illusion. A total of 10 healthy volunteers aged 23-42 years attended the experiment. The electrical brain activity was detected via scalp EEG. First, we registered the brain activity during resting state with open and with closed eyes, each for 5 min. Afterwards, the subjects were seated at a table with a mirror reflecting their left hand and occluding their right hand. The EEG was then recorded in 2 min sequencies during four modifications of the experiment (haptic contact on both hands, stimulation of the left hand only, right hand only and without any tactile stimuli). We randomized the order of the modifications for each participant. The obtained EEG data were converted into the sLORETA program and evaluated statistically at the significance level of
≤ 0.05. The subjective experience of all the participants was registered using a survey. A statistically significant difference in source brain activity occurred during all four modifications of our experiment in the beta-2, beta-3 and delta frequency bands, resulting in the activation of 10 different Brodmann areas varying by modification. The results suggest that the summation of stimuli secured by interpersonal haptic contact modified by mirror illusion can activate the brain areas integrating motor, sensory and cognitive functions and further areas related to communication and understanding processes, including the mirror neuron system. We believe these findings may have potential for therapy.
Vojta’s therapy is a widely used approach in both the prevention and therapy of musculoskeletal disorders. Changes in the musculoskeletal system have been described repeatedly, but the principles of ...the approach have not yet been clarified. The objective of our study was to evaluate changes of intracerebral activity using electromagnetic tomography (sLORETA) that arise during reflex locomotion stimulation of the breast trigger zone according to Vojta’s therapy. Seventeen healthy women took part in the experiment (aged 20–30 years old). EEG activity was recorded 5 min prior to the reflex locomotion stimulation, during stimulation, and 5 min after the stimulation. The obtained data were subsequently processed in the sLORETA program and statistically evaluated at the significance level p ≤ 0.05. The analysis found statistically significant differences in the frequency bands alpha-2, beta-1, and beta-2 between the condition prior to stimulation and the actual stimulation in BAs 6, 7, 23, 24, and 31 and between the resting condition prior to stimulation, and the condition after the stimulation was terminated in the frequency bands alpha-1, alpha-2, beta-1, and beta-2 in BAs 3, 4, 6, and 24. The results showed that reflex locomotion stimulation according to Vojta’s therapy modulates electrical activity in the brain areas responsible for movement planning and regulating and performing the movement.
The coronavirus pandemic has affected life and left one of the strongest negative effects on sport. The aim of our study was to evaluate how a simple exercise performed with elastic resistance during ...the COVID-19 pandemic, when athletes cannot train, affects the basic shooting characteristics of ball hockey players. Extra-league ball hockey players (
= 30, age 19-37 years) were randomly divided into an experimental group, which performed elastic resistance exercises with Proprioceptive Neuromuscular Facilitation (PNF) elements for eight weeks, and a control group, which did not perform any exercises. Before the start of the experiment and after it was completed, the speed and accuracy of shooting were measured. In experimental group, there was no decrease after 8 weeks in the shooting speed, and in the control group, there was a statistically significant decrease. There was a deterioration in the accuracy of shooting in both groups; however, in the experimental group, the deterioration was not significant. The results show that even three simple exercises with elastic resistance according to the PNF concept performed 10 times per day for eight weeks can maintain the level of basic skills of ball hockey players-the speed and accuracy of shooting-even when no other training is performed.
Due to the high prevalence of neck pain, considerable attention is paid to the function of cervical flexor muscles. Although the deep and superficial cervical flexor muscles have been evaluated, the ...impact of hyoid muscles on cervical flexion is still not well known. We, therefore, aimed to investigate the activation of hyoid muscles during physiological cervical flexion, and to determine the impact of different starting positions on cervical flexion muscle activation. The activities of bilateral sternocleidomastoid, scalene, suprahyoid, and infrahyoid muscles were evaluated by surface electromyography (EMG) in twenty young healthy volunteers. They performed a repetitive cervical flexion-extension movement, from neutral position of the head to the maximum flexion with the same speed set at eight seconds in a cycle, in three various positions (sitting, standing, and supine). In sitting and standing positions, the group of suprahyoid muscles was activated in advance of other cervical flexor muscles despite only significant differences were found in scalene muscles, and the activation of the group of infrahyoid muscles was time-synchronous with sternocleidomastoid muscles. On the other hand, in supine position, the activation of all measured cervical flexor muscles was significantly earlier and longer than in the other two positions. This study confirmed the empirical suggestion that hyoid muscles contributed to cervical flexion, and it confirmed that muscle activation was position dependent, even if the given movement is nearly identical.
PDF
