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The torque ripple of a switched reluctance motor (SRM) should be taken into account, as it can have negative effects on a connected gearbox and/or load. In this paper a concept and two realization methods for the reduction of the torque ripple are presented. An optimized alignment of the active elements of the stator leads to a reduction of this torque ripple. The first method proposed here is a four-fold segmented motor, which can reduce the torque ripple by 37.3 %. This can be achieved by segmentation in combination with a clever arrangement of active elements. However, this increases the number of necessary inverters, which increases redundancy and therefore leads to more security. A second method of achieving an equal reduction can be obtained by using a “double stator” motor. In this configuration both stators can be powered together. With this concept, the number of converters is halved compared to the first mentioned solution. This saves electronic components and thus reduces the effort. All results referred to in this article are obtained by simulation, or measured on a prototype. [ABSTRACT FROM AUTHOR]

Contribution: This paper qualitative research delineates the thinking and behavioral patterns that reflect students’ advanced level of epistemological thinking in project-based learning (PBL) activities and the associated impact factors. Background: PBL has been widely adopted in engineering education for its effectiveness in improving students’ problem-solving abilities, collaboration skills, and academic achievement. The four stages of Perry’s theory—Dualism, Multiplicity, Relativism, and Commitment (within Relativism)—depict students’ epistemological development from dualistic to contextual relativistic thinking. Prior research suggested that participation in PBL could benefit students’ development to relativistic thinking—the most revolutionary change in Perry’s model. Nevertheless, how epistemological thinking was exhibited in the context of PBL, and the relationship between students’ epistemological thinking and PBL learning activities both remain unclear. Research Questions: 1) What are demonstrations of students’ relativistic thinking in PBL activities? and 2) What are the factors in regard to students’ relativistic thinking in PBL activities? Methodology: Built upon quantitative results obtained using a modified Zhang’s cognitive development inventory (ZCDI) developed in the context of Perry’s theory, this paper explored demonstrations of students’ relativistic thinking in PBL in a qualitative manner, and analyzed the associated factors based upon one-on-one interviews with 17 engineering students. Findings: In PBL activities, students’ epistemological thinking is reflected in their solving problems within constraints, conducting feasibility analyses, exhibiting commercial awareness, having their thinking broadened, and more. Their epistemological thinking can be impacted by factors, such as guidance from professors, collaborations with peers, communications with other stakeholders, and complexity level of projects. [ABSTRACT FROM AUTHOR]

In mechanical engineering, multi-translational oscillator with rotational actuator (multi-TORA) systems have been introduced to study the self-synchronized phenomenon as well as to investigate the vibration damping problem associated with many vibrational mechatronic systems, e.g., hand-held drills. Due to the lack of available actuators, multi-TORA systems are typically underactuated. Multi-TORA systems consist of a series of single TORA subsystems connected to and coupled with each other by elastic springs. For practical multi-TORA systems, the plant parameters are usually unknown or difficult to measure. Moreover, they exhibit strong nonlinear coupling behaviors. These factors bring much difficulty for both controller design and analysis. The control problem for underactuated multi-TORA systems with parametric uncertainties is challenging and still open. To address the above issues, this paper proposes a nonlinear increased motion control scheme for multi-TORA systems with parametric uncertainties. Specifically, a novel energy function is constructed and some extra coupling terms are introduced into the proposed controller for improving the transient performance. Then, based on Lyapunov techniques, we rigorously prove the asymptotic stability for the equilibrium point of the closed-loop system. As far as we know, this paper gives the first smooth control law to yield global asymptotic control results for underactuated multi-TORA systems suffering from unknown/uncertain plant parameters. To verify the effectiveness of the proposed controller, a series of hardware experiments are carried out on a self-built double-TORA hardware testbed, which indicate that the controller achieves effective control results in various conditions. [ABSTRACT FROM AUTHOR]

We developed a unified semianalytical thermal–fluidic model for hotspot (HS) thermal management via thin-film evaporation from well-defined silicon micropillar wicks. The capillary pressure generated at a receding liquid meniscus is matched with the flow resistance of the micropillar wick to estimate the dryout heat flux. In addition to modeling the fluidic transport within the porous wick structure, the thermal transport was modeled by solving the 3-D heat diffusion equation. The model prediction for the capillary-limited dryout heat flux agrees within ±20% accuracy with our experiments for the range of heat fluxes reported in this paper. Our comprehensive thermal–fluidic model shows that ultrahigh heat fluxes in excess of 10 kW/cm2 can be dissipated from a 640 \times 620~\mu \textm^2 HS area via thin-film evaporation from microstructured surfaces by carefully selecting the thickness and thermal conductivity of the substrate. Furthermore, our results show that there is a global optimum pillar diameter-to-spacing ratio for a given micropillar wick thickness and spreading radius that maximizes the capillary-limited dryout heat flux. The physical insights gained from this paper can be used to improve and optimize the design of wicking structures for extreme heat flux thermal management. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a compliant mechanical amplifier (mechAMP) suitable for the sensitivity enhancement in MEMS sensor applications. The design, fabrication and characterization of a planar compliant amplifier mechanism is presented with special focus on the kinematic and static system modelling of the displacement and force amplification. We show that the proposed system can also be applied as mechanical stiffness transformer for the adaption of mechanical signals or as mechanical transformer for MEMS actuators. Based on a kinematic model, a compact mechanism with a system size of 930 μm × 2080 μm and a displacement amplification ratio of 200 with an output displacement in a range of 100 μm was designed. The fabrication of the system was carried out using silicon-on-insulator (SOI) technology. Experimentally, we could verify an amplification ratio of 197.9 for the designed and fabricated system which corresponds to the analytic model by a deviation of about 1%. [2019-0228] [ABSTRACT FROM AUTHOR]

Contribution: A semester-long, open-ended design project was implemented to promote intellectual development of first-year students while reinforcing event-driven/procedural programming principles. This paper describes this approach, and an evaluation strategy using Perry’s model for intellectual development. The results show that students can reach the relativism stage of Perry’s model in their first year of studies. Background: Students must move beyond a dualistic worldview to be engineers. Felder and Brent provided a list of recommendations to promote this type of intellectual development in students; active learning strategies strongly align with these recommendations. While active learning is common in programming courses (sometimes taking the form of project-based learning), they are typically tightly controlled by the instructor, and limited in scope (both in time and complexity), potentially reducing their impact on students. Intended Outcomes: This course and term-long project provided students a supportive environment in which to develop their decision-making skills, and promoted their intellectual development through Perry’s stages related to software design. Application Design: Aligned with Felder and Brent’s recommendations and Kuh’s High Impact Practices, a course was built to: 1) teach students procedural programming, with 2) a focus on software design and open-ended problem solving, while maintaining 3) a supportive environment for skill acquisition. Findings: A mixed methods study showed the majority of students align themselves with the relativism stage of intellectual development at the end of the course. This study also illuminated the decision-making processes of teams of students in a first-year software design course. [ABSTRACT FROM AUTHOR]

This paper considers multi-degree cyclic scheduling in automated electroplating lines with multiple hoists. In a line, hoists share the same overhead track and cannot cross over each other while transporting parts. To avoid conflicts among hoists, the hoist assignment principle without overlapping is applied. Identical parts with processing time windows are produced. The objective is to maximize the throughput of the line, equivalently to minimize the cycle time in given degree cycles. Previous work mainly focuses on simple cycles, i.e., 1-degree cycles. This paper considers multi-degree cycles to improve the throughput, which is the main contribution of this research. Operations of multi-degree cycles are analyzed in details. Then, a mixed-integer linear programming model is formulated to obtain the optimal schedules. Numerical examples are used to illustrate the schedules obtained in multi-degree cycles based on the model proposed. A number of randomly generated instances simulating practical data are tested. Computational results show the benefits of multi-degree cycles and the efficiency of the approach proposed in practice. [ABSTRACT FROM AUTHOR]

This paper addresses the transient performance improvement for path-following control of underactuated surface vessels (USVs) in the presence of oceanic disturbances. The traditional practice that chooses the tangent direction of the desired path as the desired heading may deteriorate the tracking performance in the curve following due to the nonzero sideslip angle therein. Also, the disturbances in wave filed greatly affect the transient path-following control. To this end, three contributions are made in this paper: 1) an amendment to the definition of the desired heading using the sideslip-angle compensation is presented to achieve a more accurate path-following maneuver; 2) a novel disturbances observer-based composite nonlinear feedback (DO-CNF) controller is proposed to restrain system overshoots and eliminate steady-state errors while dealing with multiple oceanic disturbances with unknown bounds; and 3) the variation of the yaw-rate reference for path-following objective is handled in the controller design, which can enhance the vessel's robustness to the changing of the path curvature. Comparative simulations verify the reasonability of the desired-heading amendment and the effectiveness of the DO-CNF approach in improving the transient path-following performance of USVs while satisfying actuator saturation considering the unknown disturbances and changing reference. [ABSTRACT FROM PUBLISHER]

In this paper, a novel Ni-doped SAC 1205 (Sn–1.2Ag–0.5Cu) solder alloy is investigated to determine its mechanical behavior at a high strain rate. The Ni-doped SAC 1205 solder alloy has never been discussed in terms of high-strain-rate testing. The purpose of the SAC 1205 solder material doped with Ni is to enhance the mechanism of the solder alloy and delay the formation of the brittle intermetallic compound. In the drop test standard (Joint Electron Device Engineering Council condition B), the test vehicle was subjected to impact loading with a peak acceleration of 1500G and a time duration of 0.5 ms. Because the test board supported the impact loading for a very short time, the solder joint material was considered to have a rate-dependent elastic–plastic behavior. The quasi-static mechanical behavior and dynamic behavior were estimated for the simulation modeling by conducting a quasi-static tensile test and a split Hopkinson tensile bar test. A finite-element model was used to analyze the stress and strain of the solder joint during the drop test. The experimental results revealed that Young’s modulus and yielding strength of the Ni-doped SAC 1205 solder alloy increased during the high-strain-rate testing. Therefore, a rate-dependent elastic–plastic model of the Ni-doped SAC 1205 solder alloy was designed and implemented to describe the real mechanical behavior of a solder joint at a high strain rate during a drop test. The primary failure mode occurs at the top of the solder joint (package side) during the drop test. The predicted fatigue model we provided was focused on the primary failure mode. Eventually, the fatigue life curve of the rate-dependent elastic–plastic model offered the greatest accuracy in predicting the solder joint fatigue life. [ABSTRACT FROM AUTHOR]

This paper presents a method for efficiently testing the stability of an object under contact that accommodates empirical models of admissible forces at individual contact points. It handles a diverse range of possible geometries of the admissible force volume, including anisotropy, adhesion, and even nonconvexity. The method discretizes the contact region into patches, performs a convex decomposition of a polyhedral approximation to each admissible force volume, and then formulates the problem as a mixed integer linear program. The model can also accommodate articulated robot hands with torque limits and joint frictions. Predictions of our method are evaluated experimentally in object lifting tasks using a gripper that exploits microspines to exert strongly anisotropic forces. The method is applied to calculate gripper loading capabilities and equilibrium predictions for a quadruped climbing robot on steep and overhanging terrain. [ABSTRACT FROM AUTHOR]

Harmonic emissions of power electronic (PE) devices connected to transmission networks are introducing new and rising trends of harmonic distortion. Analyses, which focus on assessing the harmonic levels in PE-rich power networks of the future, are mostly based on digital simulations, which require accurate models of the power system and connected devices. The simulations are usually performed with the use of electro-magnetic transient (EMT) models, resulting in long simulation times or the use of oversimplified load-flow models. In this paper, we propose a methodology that can be used to define accurate frequency-domain simulation models of PE devices. The models are derived by frequency-dependent multiparameter scanning. The resulting models can be employed for harmonic load-flow simulations in different network and PE-device operating conditions. They enable the assessment of the impact of frequency-dependent network-impedance characteristics and, moreover, the effect of cross coupling between different frequency components. The analysis is focused on high-power high-voltage PE devices, which cannot be easily measured or analyzed for harmonic characteristics. Therefore, the methodology requires detailed EMT models of the devices, which are analyzed within different operating conditions. The accurate equivalent models of PE devices represent a crucial element within the context of harmonic emission studies in large transmission networks. [ABSTRACT FROM AUTHOR]

This paper presents a novel feedback (FB) controller design on the basis of a circle condition for the fast and precise positioning of mechatronic systems. In general FB controller design, both disturbance suppression and system stability (i.e., gain and phase margins) are essential indexes to provide the desired control performance. A circle condition-based FB controller design by an optimization framework using a linear matrix inequality (LMI) technique has been already proposed in the literature, where the disturbance suppression performance was successfully improved with the desired stability margin. However, since the conventional approach did not consider the frequency shaping of FB control system, the fine positioning performance was deteriorated by response variations due to mechanical parameter variations, disturbances, and/or plant uncertainties. In this paper, therefore, a circle condition-based FB controller design considering the frequency shaping is proposed to achieve robust properties against the response variations. Effectiveness of the proposed approach has been verified by numerical simulations and experiments using a prototype of linear motor-driven table system. [ABSTRACT FROM PUBLISHER]

Type-II superconductors are expected to be extensively used in the designing of dc power grids due to their reduced use of space, high transport current capability, and nearly zero resistive losses. Nevertheless, these systems will have to share the right of way of the currently installed ac network, reducing the costs of development associated with the superconducting (SC) cables without the need of increasing the right of way. Under the theoretical framework of the critical state model and the numerical solution of Maxwell equations in the magneto quasi-steady approach, in this paper, we present a comprehensive study of the effects of applying an ac transverse magnetic field to a type-II SC wire of rounded cross section it utilized for direct current power transmission. Our numerical results can be used as a practical benchmark for determining the minimal losses and magnetic impact of dc SC lines subjected to external oscillating magnetic fields. The local dynamics of the flux front profile of current density, the resulting density of magnetic flux, the total magnetic moment of the wire, and the curve of ac losses for different conditions of dc current and transverse AC magnetic field are presented. Our results are compared with simplified analytical approaches, demonstrating the importance of considering the concomitant action of dc current and ac magnetic field by the use of numerical methods, mainly at low values of applied magnetic field relative to the intensity of transport current and the full penetration profile of current density. [ABSTRACT FROM AUTHOR]

Informal science learning aims to improve public understanding of STEM. Free-choice learners can be engaged in a wide range of experiences, ranging from watching entertaining educational videos to actively participating in hands-on projects. Efforts in informal science learning are often gauged by their ability to elicit interaction, to foster learning, and to influence perceptions of STEM fields. This paper presents the installation of a biomimetic robotic fish controlled by an iDevice application at an informal science learning exhibit. Visitors to the exhibit are offered a unique experience that spans engineering and science, in which they can steer the robotic fish, choosing from three modes of control. Visitor engagement is examined through the lens of the Selinda model of visitor learning, while their behavior is examined using an adapted model of Borun’s framework for behaviors indicative of learning. The evaluation of the efficacy of the exhibit is assessed through a post-experience survey questionnaire, an analysis of the application usage, and a behavior coding study. Data collected on visitor interactions with the exhibit indicate that free-choice learners value the importance of engineering research, and prefer interactive modes. Further, behavior coding results support the ability of the robotic fish platform to capture the visitors’ attention. Findings offer compelling evidence that the exhibit is both highly engaging to visitors and a suitable format for science inquiry. [ABSTRACT FROM AUTHOR]

Course objectives, like research objectives and product requirements, help provide clarity and direction for faculty and students. Unfortunately, course and laboratory objectives are not always clearly stated. Without a clear set of objectives, it can be hard to design a learning experience and determine whether students are achieving the intended outcomes of the course or laboratory. In this paper, a common set of laboratory objectives, concepts, and components of a laboratory apparatus for undergraduate control systems laboratories were identified. A panel of 40 control systems faculty members completed a multi-round Delphi survey to bring them toward consensus on the common aspects of their laboratories. These panelists identified 15 laboratory objectives, 26 concepts, and 15 components common to their laboratories. Then an 45 additional faculty members and practitioners completed a follow-up survey to gather feedback on the results. In both surveys, each participant rated the importance of each item. While average ratings differed slightly between the two groups, the order in which the items were ranked was similar. Important examples of common learning objectives include connecting theory to what is implemented in the laboratory, designing controllers, and modeling systems. The most common component in both groups was MathWorks software. Some of the common concepts include block diagrams, stability, and PID control. Defining common aspects of undergraduate control systems laboratories enables common development, detailed comparisons, and simplified adaptation of equipment and experiments between campuses and programs. [ABSTRACT FROM AUTHOR]

Future high-energy accelerators will need very high magnetic fields in the range of 20 T. The EuCARD-2 WP10 Future Magnets collaboration is aiming at testing HTS-based Roebel cables in an accelerator magnet. The demonstrator should produce around 17 T, when inserted into the 100-mm aperture of Feather-M2 13-T outsert magnet. HTS Roebel cables are assembled from meander-shaped REBCO-coated conductor tapes. In comparison with fair level of uniformity of current distribution in cables made out of round Nb–Ti or Nb${}_{3}$ Sn strands, current distribution within the coils wound from Roebel cables is highly nonhomogeneous. It results in nonuniform electromagnetic force distribution over the cable that could damage the very thin REBCO superconducting layer. This paper focuses on the numerical models to describe the effect of the nonhomogeneous current distribution on stress distribution in the demonstrator magnet designed for the EuCARD-2 project. Preliminary results indicate that the impregnation bonding between the cable glass fiber insulation and layer-to-layer insulation plays a significant role in the pressure distribution at the cable edges. The stress levels are safe for Roebel cables. Assuming fully bonded connection at the interface, the stresses around the edges are reduced by a large factor. [ABSTRACT FROM PUBLISHER]

To improve the flexibility and robustness of the engineering of automated production systems (aPS) in the case of extending, reducing, or modifying parts, several approaches propose an encapsulation and clustering of related functions, e.g., from electrical, mechanical, or software engineering, based on a modular architecture. Considering the development of these modules, there are different stages, e.g., module planning or functional engineering, that have to be completed. A reference model that addresses the different stages for the engineering of aPS is proposed by the automation markup language (AML). Due to these different stages and the integration of several engineering disciplines, e.g., mechanical, electrical/electronic, or software engineering, information not limited to one discipline are stored redundantly, increasing the effort to transfer information and the risk of inconsistency. Although data formats for the storage and exchange of plant engineering information exist, e.g., AML, fixed domain specific structures and relations of the information, e.g., for automated material flow systems (aMFSs), are missing. This paper presents the integration of a metamodel into the development of modules for aMFS to improve the transferability and consistency of information between the different engineering stages and the increasing level of detail from coarse-grained plant planning to fine-grained functional engineering. [ABSTRACT FROM PUBLISHER]

This paper proposes a semi-geometric process (SGP) model to generalize the geometric process (GP) model. The SGP differs from the GP in that the failed system after repair may not degenerate. By assuming that the system is not degenerative at the nth repair with probability pn and is geometrically degenerative with probability 1 - pn, we give explicit expressions of the distribution function and the mathematical expectation of the system working times after repair. In addition, an order-replacement model is developed for a deteriorating system based on SGP. The policy N is adopted, that is the system will be replaced after the Nth failure and the spare system is ordered at the end of the (N - 1)th repair. The long-run average availability A(N) and cost rate C(N) are derived, and the optimal policy N^\ast such that C(N) is minimized is obtained under the premise of meeting the availability requirement. Finally, we give a numerical example to illustrate the model, and carry through some discussions and sensitivity analysis of the model. [ABSTRACT FROM AUTHOR]

This paper examines the problem of tracking control of networked multi-agent systems with multiple delays and impulsive effects, whose results are applied to mechanical robotic systems. Four kinds of impulsive effects are taken into account: 1) both the strengths of impulsive effects and the number of nodes injected with impulses are time dependent; 2) the strengths of impulsive effects occur according to certain probabilities and the number of nodes under impulsive control is time varying; 3) the strengths of impulses are time varying, whereas the number of nodes with impulses takes place according to certain probabilities; 4) both the strengths of impulses and the number of nodes with impulsive control occur according to certain probabilities. By utilizing the comparison principle, criteria are established for these different cases and a relationship between the frequencies (occurrence probabilities) of impulses and systems' parameters is unveiled. Finally, an example for tracking control of robotic systems is provided to show the effectiveness of the presented results. [ABSTRACT FROM PUBLISHER]

This paper develops ordering heuristics to improve the efficiency of reliability evaluation for multistate two-terminal networks given all minimal path vectors ( d -MPs for short). In the existing methods, all d-MPs are treated equally. However, we find that the importance of each d-MP is different, and different orderings affect the efficiency of reliability evaluation. Based on the above observations, we introduce the length definitions for d-MPs in a multistate two-terminal network, and develop four ordering heuristics, called O1, O2, O3, and O4, to improve the efficiency of the Recursive Sum of Disjoint Products (RSDP) method for evaluating network reliability. The results show that the proposed ordering heuristics can significantly improve the reliability evaluation efficiency, and O1 performs the best among the four methods. In addition, an ordering heuristic is developed for the reliability evaluation of multistate two-terminal networks given all minimal cut vectors (d-MCs). [ABSTRACT FROM AUTHOR]

This paper presents a novel resonance-based multicoil array structure to wirelessly charge or power up apparatus, like smart phones, computer mouses, smart animal research systems, or implanted medical devices. The proposed array consists of a novel multicoil inductive link, whose primary resonator is made of several identical coil elements connected in parallel and arranged in an array. Such a structure presents several key features compared to previous inductive coil arrays. The proposed approach can do the following: 1) deliver power with superior efficiency over longer separation distances; 2) naturally track the receiver position and localize transmitted power through nearby coil array elements without the need for complex control and detection circuitry; and 3) accommodate either short- or long-range power transmission applications simply by slightly modifying the receiver topology. The performance of the proposed structure is verified by measurement results. In a three-coil configuration, the prototype provides a power transfer efficiency (PTE) of 83.3% and a power delivered to the load (PDL) of 3.87 W for a separation distance below 1 cm, while in a four-coil configuration, it provides a PTE of 76% and a PDL of 115 mW for a separation distance of 4 cm. [ABSTRACT FROM PUBLISHER]

This paper introduces model reduction techniques based on various methods known from mechanical engineering that are used in calculation for structural analysis. These techniques are applied to electrical machines reducing the number of degrees of freedom and, hence, computation time for transient analysis. It further introduces magnetic superelements for the stator and the rotor of these machines and combines them with suitable coupling methods from literature. [ABSTRACT FROM AUTHOR]

The Asia-Pacific International Symposium on the Basics and Applications of Plasma Technology (APSPT) has been held in Taiwan every two to four years since 1997. It is an important annual event in the Asia-Pacific area, providing an excellent platform for exchanging new ideas and sharing the most advanced knowledge in plasma-related science and technology. Thanks to the participants from 10 countries, in the 8th APSPT, we had a very strong program with 187 papers delivered at National Chiao Tung University, Hsinchu, Taiwan, in December 20–22, 2013. This special issue documents the selected presentations in all kinds of plasma science and technology. There were 51 papers submitted after the conference and 32 accepted to be published in this special issue. We also thank the authors, the reviewers, the editors, and the publisher, who have seamlessly worked together to publish this special issue in time. I hope it will help advance our knowledge in plasma science and technology and cultivate future scientific collaboration among those who participated in APSPT 2013. I look forward to seeing all participants again in the 9th APSPT at Nagasaki University, Japan, in December 2015. [ABSTRACT FROM PUBLISHER]

These instructions give guidelines for preparing papers for this publication. Presents information for authors publishing in this journal. [ABSTRACT FROM PUBLISHER]