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The aim of this paper is to construct a theoretical framework for stability analysis relevant to standing balance of humanoids on top of the linear inverted pendulum model, in which their dynamics between the center of mass (CoM) and the zero moment point (ZMP) is dealt with. Based on the well-known sufficient condition that the contact between the ground and the support leg is stable if the corresponding ZMP is always inside the supporting region, this paper aims at characterizing three types of the associated stability regions. More precisely, assuming no external force disturbances affecting the motion of the humanoids, the stability region of the initial CoM position and velocity values can be explicitly computed by solving a finite number of linear inequalities. The stability regions of time-invariant force disturbances such as impulsive force and constant force disturbances are also dealt with in this paper, where the former is exactly obtained through a finite number of linear inequalities while the latter is approximately derived by using an idea of truncation. Furthermore, time-varying force disturbances of finite energy and finite amplitude are concerned with, and their maximum admissible ${l} _{2}$ and ${l} _{\infty }$ norms are computed in this paper, where the former can be exactly obtained by solving the discrete-time Lyapunov equation while the latter is approximately derived through an idea of truncation. It is further shown for both the truncation ideas that the approximately obtained stability regions converge to the exact stability regions with an exponential order of ${N}$ , where ${N}$ is the truncation parameter. Finally, the effectiveness of the computation methods proposed in this paper is demonstrated through some simulation results. [ABSTRACT FROM AUTHOR]

Firing accuracy is a critical quantity of interest in the performance analysis of electromagnetic railgun (EMRG) exterior ballistics. Since the simulation technique is always used to simulate the complex physical system at a low cost, it is employed to evaluate the firing accuracy of railgun projectile with uncertainty in this paper. An exterior ballistics simulation model of the railgun, including 3-DOF flight mechanical model, relative kinematic model, and guidance law model, is developed to simulate the ballistics behavior in the missile target intercept mission. The firing accuracy is studied in this paper to compare the capability of EMRG with different ranges and muzzle velocities. In order to explore the firing accuracy of the guided projectile, the guidance precision analysis and ballistics uncertainty quantification are studied. In the guidance precision analysis, the shot range and efficiency are used to make a comparison. In addition, the sensitivity analysis and firing accuracy analysis are also performed in terms of uncertainty quantification. The simulation results illustrate that the simulation of the guided projectile can give some practical guide to the projectile design of EMRG. [ABSTRACT FROM AUTHOR]

In this paper, a quadcopter unmanned aerial vehicle (UAV) system based on neural-network enhanced dynamic inversion control is proposed for multiple real-world application scenarios. A sigma-pi neural network (SPNN) is used as the compensator to reduce the model error and improve the system performance in the presence of the uncertainties of UAV dynamics, payload, and environment. Besides, we present a technical framework for fast and robust implementation of multipurpose UAV systems and develop a testbed for the evaluation of UAV control system by using a high-precision optical motion capture system. Both simulation results and experiment results demonstrate that the SPNN can reduce the inversion errors related to UAV parameter uncertainties as well as tracking errors related to unknown disturbances and unmodeled dynamics. With the help of an online neural network (NN) learning mechanism, the entire system can achieve much higher accuracy in attitude and trajectory control than that achieved by conventional proportional-integral derivative based control systems under varying flight conditions. [ABSTRACT FROM AUTHOR]

Simulation involving interaction with deformable objects often causes stability problems because a slowly updated force generates additional energy to the human user. This paper proposes a stable and transparent haptic rendering for simulation involving interaction between a rigid tool and deformable objects. This method computes visual and haptic feedback in the simulation and haptic feedback loops, respectively. A local stiffness matrix consisting of points around contact points is constructed based on collision detection between a virtual tool and a deformable object in the simulation loop. The haptic feedback is then computed at a higher update rate in the haptic feedback loop using the local stiffness matrix. Equivalent springs computed by using the equivalent stiffness energy are added to the boundary of the local stiffness matrix to minimize errors in the rendered force. The proposed method is compared with the virtual coupling widely used in simulation involving interaction with deformable objects. The proposed method reduces the x-, y-, and z-axis maximum force errors by up to 52%, 80%, and 70%, respectively, compared to the virtual coupling in the simulation involving interaction with the Stanford bunny object consisting of 2087 points and 9997 tetrahedrons. [ABSTRACT FROM AUTHOR]

Operation optimization for modern subway trains usually requires the speed curve optimization and speed curve tracking simultaneously. For the speed curve optimization, a multi-objective seeking issue should be addressed by considering the requirements of energy saving, punctuality, accurate parking, and comfortableness at the same time. But most traditional searching methods lack in efficiency or tend to fall into the local optimum. For the speed curve tracking, the widely applied proportional integral differential (PID) and fuzzy controllers rely on complicated parameter tuning, whereas robust adaptive methods can hardly ensure the finite-time convergence strictly, and thus are not suitable for applications in fixed time intervals of trains. To address the above-mentioned two problems, this paper presents a novel approach for speed curve seeking and tracking control. First, we present the random reinforcement genetic algorithm (GA) algorithm to avoid the local optimum efficiently. Then, a sliding mode controller is developed for speed curve tracking with bounded disturbance. The Lyapunov theory is adopted to prove that the system can be stabilized in the finite time. Finally, using the real datasets of Yizhuang Line in Beijing Subway, the proposed approach is validated, demonstrating its effectiveness and superiorities for the operation optimization. [ABSTRACT FROM AUTHOR]

To overcome the shortcomings of the traditional staircased particle-in-cell (PIC) method, this paper presents the conformal PIC method to simulate the system-generated electromagnetic pulse (SGEMP) produced by the X-ray beam. One advantage of this method is to accurately simulate the electromagnetic response from the boundary of the object, and more importantly, it can be used to simulate the emission direction of the electrons accurately by properly handling the normal direction of the curved boundary. The numerical results show that the conformal PIC method can save much more computation time and memory than the staircased PIC technique to obtain the same accurate computational results. [ABSTRACT FROM AUTHOR]

In this paper, an algorithm for the estimation of the longitudinal and lateral forces exerted at wheel level between tires and ground is presented. Starting from a modified version of the single track vehicle model, which also includes the steady-state effect of pitch and roll on the planar movement of the vehicle, the structure is designed as a cascade of two Sub-Optimal Second-Order Sliding-Mode (S-SOSM) observers, featuring an adaptive feedback that helps improving the accuracy of the estimation of the longitudinal forces. The presented approach is purposely designed so that only standard sensors, which are usually available in commercial vehicles, are exploited. In order to alleviate the high-frequency vibrations introduced by the Sliding-Mode technique, an EKF is added as a second step, which considers the output of the S-SOSM observer as a noisy measurement, hence the virtual sensor nomenclature. The method is evaluated on experimental data, displaying good performance both in terms of accuracy and chattering alleviation. [ABSTRACT FROM AUTHOR]

The shape of a concentric tube robot depends not only on the relative rotations and translations of its constituent tubes, but also on the history of relative tube displacements. Existing mechanics-based models neglect all history-dependent phenomena with the result that when calibrated on experimental data collected over a robot's workspace, the maximum tip position error can exceed 8 mm for a 200-mm-long robot. In this paper, we develop a model that computes the bounding kinematic solutions in which Coulomb friction is acting either to maximize or minimize the relative twisting between each pair of contacting tubes. The path histories associated with these limiting cases correspond to first performing all tube translations and then performing relative tube rotations of sufficient angle so that the maximum Coulomb friction force is obtained along the interface of each contacting tube pair. The robot tip configurations produced by these path histories are shown experimentally to bound position error with respect to the estimated frictionless model compared to path histories comprised of translation or mixed translation and rotation. Intertube friction forces and torques are computed as proportional to the intertube contact forces. To compute these contact forces, the standard zero-clearance assumption that constrains the concentrically combined tubes to possess the same centerline is relaxed. The effects of clearance and friction are explored through numerical and physical experiments and it is shown that friction can explain much of the prediction error observed in existing models. This model is not intended for real-time control, but rather for path planning—to provide error bounds and to inform how the ordering of tube rotations and translations can be used to reduce the effect of friction. [ABSTRACT FROM AUTHOR]

Basic kinetic process of plasmas is studied by a first principle based N-body simulation. By confirming Coulomb collisional relaxation process, this paper is extended to investigate the dynamics of Debye shielding. Some of the key numerical techniques are discussed, including how to avoid singularities at the near encounter of two charged particles. Electron distribution function in Debye shielding is revealed, which deviates from conventional Maxwellian distribution function. [ABSTRACT FROM AUTHOR]

Magnetic levitation actuators (MLAs) are increasingly employed in the modern high-precision manufacturing industry. Since the current-wrench transformation matrix is calculated inaccurately in the controller, the existing MLA finds it hard to undertake high-precision multi-degrees-of-freedom (DOF) movement in the large stroke. A high-fidelity real-time model is required to design better controllers for MLAs. This paper proposes a universal FPGA-based real-time wrench model (RTWM); meanwhile an MLA capable of translation and rotation in the horizontal plane is employed as the modeling object. To obtain the high accuracy with excellent generality, the force and torque distribution is solved through the magnetic node, coordinate transformation, and Gaussian quadrature. The corresponding calculation components are developed on the field-programmable gate array (FPGA) by exploiting the fully pipelined arithmetic and parallel architecture processing. Utilizing the high level synthesis tool, the final register transfer level structure is optimized adequately to reduce the time and hardware overhead. In the experiment, the RTWM of the proposed MLA and an existing MLA from the literature are obtained together to highlight the generality, and the computational accuracy is compared with the finite element method (FEM) software Comsol Multiphysics and a boundary element method software package Radia, respectively. The results show that the relative deviation is less than $\text{2}\%$ choosing the FEM results as benchmark. [ABSTRACT FROM AUTHOR]

The operation range of today’s micro-electromechanical systems (MEMS) continues to enter the geometric nonlinear regime due to miniaturization and performance requirements. One example is the MEMS Coriolis Vibratory Gyroscope (CVG), where the drive mode operates beyond the structural width, causing a change in resonance frequency upon displacement amplitude. Getting good estimates for this change in frequency has been a major issue in the development of CVGs over the past 20 years. In this paper, we present simulation methods and strategies to extract the nonlinear frequencies of such actuated MEMS from the finite element model of the device. The methods are explained in detail and benchmarked with two MEMS structures. As result, we find that the new methods fulfill the accuracy and performance requirements to aid MEMS designers in developing and optimizing the mechanical structure of their devices. [2018-0136] [ABSTRACT FROM AUTHOR]

The levitation system containing high-temperature superconductor (HTS) has great advantages in various applications, but the highly nonlinear properties of HTS limit its practical applications. In this paper, a method to analyze the electromagnetic behaviors of the levitation system which includes HTS bulk and permanent magnets (PMs) is presented. The method is based on the finite-element method combining with ${H}$ -formulation, which is applicable for 2-D axial symmetric problems that include HTS materials. To deal with the nonlinear properties of HTS bulks, its electric field–current density (E–J) relationship is considered here. In order to verify the validity and accuracy of the method, a simple HTS/PM system model is established which includes a cylindrical HTS bulk and PM. The axial levitation force of the model is computed considering the nonlinear properties of HTS bulk. Moreover, the corresponding experimental results of the system are also obtained and compared with the related simulation results. The comparison shows that the experimental and corresponding simulation results match well. [ABSTRACT FROM AUTHOR]

Most of surgical simulators employ a linear elastic model to simulate soft tissue material properties due to its computational efficiency and the simplicity. However, soft tissues often have elaborate nonlinear material characteristics. Most prominently, soft tissues are soft and compliant to small strains, but after initial deformations they are very resistant to further deformations even under large forces. Such material characteristic is referred as the nonlinear material incompliant which is computationally expensive and numerically difficult to simulate. This paper presents a constraint-based finite-element algorithm to simulate the nonlinear incompliant tissue materials efficiently for interactive simulation applications such as virtual surgery. Firstly, the proposed algorithm models the material stiffness behavior of soft tissues with a set of 3-D strain limit constraints on deformation strain tensors. By enforcing a large number of geometric constraints to achieve the material stiffness, the algorithm reduces the task of solving stiff equations of motion with a general numerical solver to iteratively resolving a set of constraints with a nonlinear Gauss–Seidel iterative process. Secondly, as a Gauss–Seidel method processes constraints individually, in order to speed up the global convergence of the large constrained system, a multiresolution hierarchy structure is also used to accelerate the computation significantly, making interactive simulations possible at a high level of details. Finally, this paper also presents a simple-to-build data acquisition system to validate simulation results with ex vivo tissue measurements. An interactive virtual reality-based simulation system is also demonstrated. [ABSTRACT FROM PUBLISHER]

Control of the capillary driven underfill flow process is a very important problem in flip chip technology in electronics packaging. The challenge here is to uniformly distribute fluids in the gap, which is composed of the chip and substrate and solder bumps. In this paper, we first present a conceptual model of the flow behavior of underfill materials, which has four stages, leading to the finding that the contact line jump phenomenon occurs at both entry and exit of the solder bumps. We then propose a more accurate model for describing the flow front based on the principles of mass conservation and force equilibrium. Another contribution of the present paper is the proposal of a computational model for describing the average capillary pressure difference with respect to the area of flow. The verification of these models is presented by comparing the result calculated with our model with the experimental result reported in the literature, which shows the superiority of the models proposed in this paper. [ABSTRACT FROM AUTHOR]

This paper proposes a new method for fast radial vibration computation in switched reluctance motors. Only a piecewise first-order linear function is used to calculate the total peak acceleration, which is rather fast. The overall radial vibration is the superposition of natural oscillation of each mode. Before that, several critical parameters need to be calculated or measured in advance, including weight factor, natural frequency and damping ratio of each mode, in order to obtain the respective analytical expression of natural oscillation of each mode. First, the total peak acceleration concerning the multiple of current and its slope is derived analytically from the perspective of abrupt change of radial force. Then, a simple method for calculating weight factors is presented for the distribution of peak acceleration of each mode from the total peak acceleration. Natural frequencies are measured and compared by three methods, including finite-element analysis, hammer impulse test, and dc pulse excitation. The calculation of damping ratio is improved since the traditional damping ratio calculation method cannot be used in a multiple degree-of-freedom system. Finally, both simulation and experiments are conducted to verify the effectiveness and accuracy of the proposed method. [ABSTRACT FROM PUBLISHER]

Torque-speed characteristics of an oscillating wave energy converter (WEC) is necessary to determine its optimal power point and to extract the corresponding design parameters for the generator and power converters used to generate power from the WEC. In this paper, analytical expressions for the mechanical torque on the WEC due to the oscillating surge of seawater are derived, and the dynamic model of the WEC is developed. A method for hardware emulation of the WEC is proposed by controlling the torque of an electric motor. The reference torque of the motor is derived by solving the mechanical dynamics of the WEC system in a real-time computing device considering a typical sea wave input. The emulated WEC dynamics is validated through variable loading on a generator coupled with the emulator. Experimental results support the existence of an optimal power point of the derived WEC model. [ABSTRACT FROM AUTHOR]

This paper presents a detailed investigation of the influence of several design parameters on the performance of a ferrofluid-based electromagnetic energy harvester which converts ambient vibratory energy into an electromotive force through the sloshing motion of a ferrofluid. To this end, a computational model is developed and validated against the experimental data. Using the validated model, a series of numerical simulations are performed on two configurations of the energy harvester to study the effects of the magnetic and sloshing parameters on the electromotive force. Results of the performance analysis provide useful insights for designing high-performance ferrofluid-based energy harvesters. [ABSTRACT FROM PUBLISHER]

Piezoelectric-actuated stick–slip device (PASSD) is a highly promising equipment that is composed of one end-effector, one piezoelectric actuator (PEA) and one driving object adhered to the PEA. Since the end-effector can slip on the surface of the driving object, the PASSD is capable of realizing the macrolevel motion with the microlevel precision. Due to the following two reasons: the complicated relative motion between the end-effector and the driving object, and the inherent hysteresis nonlinearity in the PEA, the ultraprecision displacement control of the end-effector of PASSDs raises a real challenge, which is rarely reported in the literature. Toward solving this challenge, a neural-network-based controller is proposed in this paper. First, a neural-network-based model is proposed to capture the relative motion between the end-effector and the driving object. Second, a neural-network-based inversion model is developed to online calculate the desired position of the PEA under the predesigned reference of the end-effector. Third, a dynamic linearized neural-network-based model predictive control method, which can effectively handle the hysteresis nonlinearity, is employed to implement the displacement control of the PEA, which finally results in an overall high-precision controller of the end-effector. Finally, a PASSD prototype has been implemented and tested through experimental studies to demonstrate the effectiveness of the proposed approach. [ABSTRACT FROM PUBLISHER]

This paper presents a novel control algorithm to regulate the aerodynamic thrust produced by fixed-pitch rotors commonly used on small-scale electrically powered multirotor aerial vehicles. The proposed controller significantly improves the disturbance rejection and gust tolerance of rotor thrust control compared to state-of-the-art RPM (revolutions per minute) rotor control schemes. The thrust modeling approach taken is based on a model of aerodynamic power generated by a fixed-pitch rotor and computed in real time on the embedded electronic speed controllers using measurements of electrical power and rotor angular velocity. Static and dynamic flight tests were carried out in downdrafts and updrafts of varying strengths to quantify the resulting improvement in maintaining a desired thrust setpoint. The performance of the proposed approach in flight conditions is demonstrated by a path tracking experiment, where a quadrotor was flown through an artificial wind gust and the trajectory tracking error was measured. The proposed approach for thrust control demonstrably reduced the tracking error compared to classical RPM rotor control. [ABSTRACT FROM PUBLISHER]

The lubricant bridge connecting the slider and the disk will significantly deteriorate the read–write stability of the hard disk drive. This paper builds a model of disk-lubricant-slider system. The coarse-grained bead-spring model is used to represent perfluoropolyethers molecules. And the molecular dynamic method is used to study the formation time and the molecule number of the lubricant bridge under different disk rotation speeds and slider flying heights. Furthermore, the influence of lubricant bridge on the pressure acting on the slider pad is also studied. [ABSTRACT FROM AUTHOR]

The aim of this paper is to study different permanent magnet (PM) bearings geometries based on PM rings with a minimum volume of PM for a given load. Simple and general scaling laws (SCLs) are proposed for each bearing geometry to predict its behavior. These SCLs allow a fast sizing of those geometries, as a function of the number of PM rings, the load reference, the air gap, and the remanent flux density. Those SCLs are derived for optimized topologies without any constraint on the geometrical parameters, as well as for optimized geometries with a constraint on the PM dimensions. For both cases, SCLs for the thrust-bearing stiffness are also proposed. [ABSTRACT FROM AUTHOR]

An accurate wrench model is significant for the simulation, manufacture, and control of the commutated magnetically levitated planar actuator (CMLPA). With plenty of coils and permanent magnets employed in the coil set and magnet array of CMLPA, the computational burden of the corresponding wrench model can be substantial. This paper proposes an accurate, universal, and robust parallel massive-thread wrench model (PMWM) for the CMLPA. In PMWM, the magnetic node, Gaussian quadrature, and coordinate transformation are employed to express the interaction between magnet array and coil set. All of these calculation modules are implemented on the graphics processing unit in a massively parallel framework by CUDA. In order to highlight the performance of this PMWM, the wrench model of three different CMLPAs is computed. The computation accuracy and efficiency of proposed PMWM are compared with the finite-element method software Ansys Maxwell and a boundary element method software package named Radia, respectively. The same wrench model is also implemented on a multicore CPU through OpenMP and the comparative results are presented to show significant acceleration of the proposed massive-thread model. [ABSTRACT FROM AUTHOR]

This paper explores the use of pantograph–catenary contact force (PCCF) for monitoring of the current collection quality and detection of anomalies in the interaction between pantograph and catenary. The concept of catenary structure wavelength (CSW) is proposed as the dominant component of PCCF. It describes the signal components caused by the cyclical catenary structure in span and interdropper distance. To obtain the CSWs and non-CSW residual of PCCF, an automatic extraction approach based on the ensemble empirical mode decomposition (EEMD) is proposed. In the approach, the instantaneous frequency of each intrinsic mode function generated by the EEMD is employed for the extraction of CSWs. Some selected trials on the PCCF data from simulation and measurement are performed and indicate that the extraction approach is adaptive to the PCCF under various circumstances, including different operation speeds, pantograph type, and catenary structure. Analyses on the extracted CSWs and non-CSW residual show that, with certain tolerance against measurement noise, the approach can preserve intact the characterizations of current collection quality and make anomalies easier to detect. [ABSTRACT FROM PUBLISHER]

A new 3-D model for the die attach (DA) process is established and validated in this paper. With this model, the fluid flow characteristics of the DA process can be predicted accurately. Dynamic mesh and interface tracking method were adopted in the modeling to study the compression motion and the front of DA. A force driven model was conducted for the parametric studies of different bonding forces. The model for the DA process was validated by the four materials, AP1, CA1, CA4, and DM60 in the optimized condition. Bond line thickness can be predicted by the simulation with $\sim 20$ % accuracy. The simulation results show that the viscosity is one of the key properties, which has a significant effect on the required bonding force, bonding time, and DA contamination on the die top. Complete filling and DA contamination on the die top are two important standards to evaluate the good bonding force range in fluid dynamic analysis. Stress analysis illuminates that a fillet area is very critical and experiences highest stress during the reflow process. [ABSTRACT FROM PUBLISHER]

Line-edge roughness induced fin-edge roughness (FER) is the primary source of VT variation in FinFETs. Conventionally, stochastic simulations are performed to predict the device variability due to FER for a technology, which are computationally expensive. An analytical formulation to predict variability due to FER enables understanding of the effect of input parameters as well as provides quantitative results at fractional computational costs. In this paper, we develop and present an analytical model to estimate saturation VT ( $V_{{T\rm {-sat}}}) variability due to FER. The model is capable of capturing the LG and W\mathrm{ fin} ) and variability parameters (correlation length $\Lambda $ and standard deviation $\Delta )$ accurately. The entire $V_{{T\rm {-sat}}}$ distribution obtained by the model is also presented and compared against the $V_{{T\rm {-sat}}} distribution of stochastic simulations to show that the model captures the distribution effectively. We show that not only \sigma VT but even \mu VT is affected by variability parameters. Hence, such modeling is critical to defining nominal FinFET structure ( LG and W\mathrm{ fin} ), which is affected by variability ( $\Lambda $ and $\Delta $ ) especially for scaled FinFETs, where quantum-confinement effects are enhanced. [ABSTRACT FROM PUBLISHER]

The aim of this paper is to propose an efficient and unique reluctance network (RN) model for all translator displacements of a linear hybrid motor. This model has to consider several translator positions to analyze the linear motor performances. The proposed RN model takes into account the magnetic characteristic and the flux leakage. Consequently, the proposed model gives precise results of the electromagnetic characteristic. The RN model considers an interesting solution to deal quickly with an optimization task of a large number of constraints and parameters. The developed model is coupled with sequential quadrating programming method for an optimization process of the linear machine. The obtained results confirm the efficiency of this method for modeling and optimization of the linear machine. [ABSTRACT FROM AUTHOR]

For the development and optimization of power system components that are subjected to high short-circuit currents, such as generator circuit breakers (GCBs) and insulated phase bus ducts, an accurate, robust, and efficient methodology for performing a 3-D transient electromagnetic-mechanical analysis is of paramount importance. The purpose of this paper is to present numerical and modeling aspects of the analysis that are decisive for the accuracy and reliability of the results. The efficient and robust 3-D approach based on Biot–Savart integration for evaluating the electromagnetic force density over electrically conductive domains, the 3-D magnetostatic approach based on the A-field formulation including an air box, and the 3-D eddy-currents approach based on the A- $\varphi $ -field formulation are compared in order to evaluate the importance and relevance of magnetic bodies consideration (structural steel components) in terms of electromagnetic force and induced eddy-currents for daily design of GCBs. [ABSTRACT FROM AUTHOR]

This paper focuses on external volume and power consumption optimization of an electromagnetic actuator used to move pins in a two-stage variable valve lift component within an automotive engine. This system is designed to change the valve lift at each engine cycle. To achieve this optimization, three models were developed: a magnetic, an electric, and a dynamic model. They evaluate the performances of a given actuator, check if it fulfills its role, and define the springs needed for the displacement of the pins. The optimization is made using a particle swarm method and can reduce the volume up to 20% with the same electric consumption. [ABSTRACT FROM PUBLISHER]

The paper presents the computer simulation results for a single section of electrohydrodynamic (EHD) conduction pump with and without taking into account the enhancement of the dissociation rate under the action of the strong electric field (the Wien effect). The computations were carried out on the basis of the complete set of EHD equations using commercial software package COMSOL Multiphysics. The behavior of EHD flow inside the pump was investigated for different ratios between positive and negative ion mobilities and the effect of the latter on the pumping efficiency was estimated. The features of the pump operation in the case of the Wien effect presence were investigated. It was shown that the enhancement of the dissociation rate can lead to the reversion of EHD flow direction with increasing voltage. Besides, the results for the present computer model were compared to those for the simplified one (based on the hydrostatic approach), and considerable discrepancy between the calculated pressure drops was revealed. [ABSTRACT FROM AUTHOR]

This paper concerns the superposition of 2-D semianalytical models to model 3-D shielding configurations. The 2-D semianalytical models are used to describe the effect of magnetic shielding on the stray field of a single-sided coreless linear permanent-magnet motor. The modeling results are compared to 3-D finite-element analysis and to measurements. It is found that an accurate description of the tendencies and the order of magnitude is given. Furthermore, the comparison of the superposition of 2-D semianalytical models with the measurements shows that saturation and neglecting the 3-D effects cause the deviation between model and measurement. [ABSTRACT FROM PUBLISHER]

Distribution systems are typically composed of radial feeders. Radial means that there is only one path of current flow to each of the loads on the feeder. There are times when it becomes necessary to form a loop in a feeder by closing switches. This may be because of an outage or a new load that will cause the radial current to exceed the conductor current rating or violate the American National Standards Institute voltage requirement. This paper will present a method for simulating the loop flow using an injection current technique. A simple single-phase circuit is used to demonstrate the steps in the simulation. Following that, the IEEE 13 bus test feeder will be studied as it is right now, followed by the addition of a new three-phase load at one bus and a new single-phase load added at another bus. Both of these loads are going to require the addition of new lines and the capability of operating the feeder with one or two closed loops. The process for simulating the closed loops will be presented. [ABSTRACT FROM PUBLISHER]

Mechanical contact caused using excessive probe force produces an oversized scrubbing mark that may result in damage to the die pad and the silicon chip breaking for thin wafer. Therefore, investigating the relationship between the wafer thickness and the limited breaking stress of the wafer, and applying this relationship as a basis for establishing suitable design rules for a multilayer needle layout are crucial. In this paper, two experimental techniques, three-point-bending test and ball-on-ring, were setup and carried out to measure the force-displacement relation of various wafer thicknesses (100–25 $\mu $ m). The results from the testing then coupled with finite-element analysis to reverse finding the breaking stress/strain as a function of wafer thickness. In addition, experimental setup with a single tungsten needle probe contact with Al pad were employed to investigate the relations between the overdrive, beam length, and scrub mark length. A 3-D computational probing simulation model was developed and verified against the experimental data. The model is then used to examine the effects of the beam length, overdrive distance (OD), and shooting angle on the maximum stress induced within the wafer. Finally, a four-layer probe card needle shape design has been demonstrated as a practical application example; it is shown that for a wafer thickness of 25 $\mu $ m and an OD of 60 $\mu $ m, the allowable shooting angles of a four-layer needle probe card are as follows: 1500 $\mu $ m and 0°–4° (Layer 1); 2100 $\mu $ m and 0°–9° (Layer 2); 3500 $\mu $ m and 0°–15° (Layer 3); and 4000 $\mu $ m and 0°–15° (Layer 4). [ABSTRACT FROM AUTHOR]

This paper presents a novel analytical model that accurately predicts the current-force characteristic of a 2 degrees-of-freedom moving magnet linear motor (MMLM), where its translator is formed by a Halbach permanent magnet (PM) array. Unlike existing theoretical models, the uniqueness of this proposed model is based on a derived magnetic field model that accounts for the magnetic flux leakage at the edges of the Halbach PM array. Hence, it can be used to model an MMLM that employs a low-order Halbach PM array effectively. To implement the proposed model in high sampling rate control system, a model-based approximation approach is proposed to simplify the model. The simplified model minimizes the computation complexity while guarantees the accuracy of the current-force prediction. MMLM prototype with two separate translators, i.e., one with a single magnetic pole Halbach PM array and the other with six magnetic poles Halbach PM array, were developed to evaluate the accuracy of the proposed models. [ABSTRACT FROM AUTHOR]

Electromagnetic actuators are energy conversion devices that suffer from inefficiencies. The conversion losses generate internal heat, which is undesirable, as it leads to thermal loading on the device. Temperature rise should be limited to enhance the reliability, minimize thermal disturbance, and improve the output performance of the device. This paper presents the application of an optimization method to determine the geometric configuration of a flexure-based linear electromagnetic actuator that maximizes output force per unit of heat generated. A two-stage optimization method is used to search for a global solution, followed by a feasible solution locally using a branch and bound method. The finite element magnetic (fine) model is replaced by an analytical (coarse) model during optimization using an output space mapping technique. An 80% reduction in computation time is achieved by the application of such an approximation technique. The measured output from the new prototype based on the optimal design shows a 45% increase in air gap magnetic flux density, a 40% increase in output force, and a 26% reduction in heat generation when compared with the initial design before application of the optimization method. [ABSTRACT FROM PUBLISHER]

The locomotion of miniature medical robots in the interior of the human body, possibly in contact with the tissue of organs and vessels, is a challenging problem in robotics, which, if properly addressed, might favorably impact several significant applications. This paper investigates the potential of employing relatively low-frequency vibrations, generated by an on-board eccentric motor, to reduce friction for such robots, moving by some other primary mechanism over and in contact with liver tissue. This study focuses on the computational modeling and the experimental assessment of the interaction between vibratory-actuated miniature robots and compliant tissue. The computational model developed to analyze the effect of such vibrations, for a robot moving over a substrate with normal-wise viscoelasticity, is employing a modified Dahl model with viscous damping for the tangential friction. Experiments with a vibratory-actuated platform pulled over ex-vivo bovine liver tissue indicate that the friction reduces as the frequency of vibrations increases, in a manner consistent with the model’s predictions, reaching a reduction of up to $40\%$. [ABSTRACT FROM AUTHOR]