Pure Integrator Research Articles

Wave solutions in nonlocal integral beams

Wave propagation in slender beams is addressed in the framework of nonlocal continuum mechanics. The elastodynamic problem is formulated exploiting consistent methodologies of pure integral, mixture and nonlocal strain gradient elasticity. Relevant wave solutions are analytically provided, with peculiar attention to reflection and near field phenomena occurring in presence of boundaries. Notably, the solution field is got as superimposition of incident, reflected, primary near field and secondary near field waves. The latter contribution represents a further effect due to the size dependent mechanical behaviour. Limit responses for vanishing nonlocal parameter are analytically evaluated, consistently showing a zero amplitude of the secondary near field wave. Parametric analyses are carried out to show how length scale parameter, amplitude of incident wave and geometric and elastic properties of the beam affect the amplitudes of reflected, primary near field and secondary near field waves. The results obtained exploiting different nonlocal integral elasticity approaches are compared and discussed.

Extending the professional borders or maintaining the status quo? Union membership as boundary work

Disruption and changes within the profession of journalism instigate boundary disputes. In this article, we analyse boundary work ‘in the making’, with the debate about membership rules within the Norwegian Union of Journalists as a case. The research question asked is: How do positioning and rhetoric in the membership debate evoke boundary struggles in journalism, and how do they reflect the internal professional hierarchy? Theoretically anchored in the sociology of professions, this study is based on qualitative text analysis of debate articles in the specialist magazines Journalisten and Medier24, as well as qualitative interviews. The findings suggest two main positions. On the one hand, a struggle to protect pure professional identity, values, and integrity. On the other, arguments regarding union power and impact and the contention that in today’s digital media landscape journalism in practice involves a wide range of competencies. The two positions suggest a tension between white-collar professionalism and blue-collar unionism. This study contributes to our understanding of the shifting boundaries of journalism, and how changes in external conditions also impact upon internal professional identity.

Research on Sliding Mode Variable Structure Model Reference Adaptive System Speed Identification of Bearingless Induction Motor

To improve the speed observation accuracy of the bearingless induction motor (BL-IM) and achieve its high-performance speed sensorless control, an improved sliding mode variable structure model reference adaptive system speed identification method based on sigmoid function (sigmoid-VS-MRAS) is proposed. Firstly, to overcome the problem of initial values and cumulative errors in the pure integration link of the reference flux-linkage voltage model, the rotor flux-linkage reference voltage model has been improved by using an equivalent integrator instead of the pure integration link. Then, in order to improve the rapidity and robustness of speed identification, the sliding mode variable structure adaptive law is adopted instead of the PI adaptive law. In addition, in order to optimize the sliding mode variable structure adaptive law and overcome the sliding mode chattering problem, a sigmoid function with smooth continuity characteristics is used instead of the sign function. Finally, on the basis of the inverse system decoupling control of a BL-IM, simulation experiments were conducted to verify the sigmoid-VS-MRAS speed identification method. The research results indicate that when the proposed speed identification method is adopted, not only higher identification accuracy and rapidity can be achieved than traditional PI-MRAS methods, but it can also eliminate the problem of high-frequency vibration (with an amplitude of about 3.0 r/min) when using the sign-VS-MRAS method; meanwhile, the steady-state tracking speed with zero deviation can still be maintained after loading.

Cutkosky representation and direct integration

We present a new method of direct integration of Feynman integrals based on the Cutkosky representation of the integrals. In this representation we are able to explicitly compute the integrals which yield square root singularities and leave only the integrals which yield logarithmic singularities, thus making the transcendentality weight manifest. The method is elementary, algorithmic, does not introduce spurious non-physical singularities and does not require a reduction to a basis of pure integrals.

Grid Synchronization in a 3-Phase Inverter using Double Integration Method

Distributed renewable energy sources (DRESs) have additional benefits compared with conventional fossil fuel-based energy sources. These sources are connected to the utility grid using a suitable synchronization method. It requires accurate information on grid voltage magnitude and phase angle. But the presence of harmonics, DC Offset, and voltage unbalances makes the synchronization process more challenging. Conventionally synchronous reference frame (SRF)- PLL is implemented for this purpose, however, it has a problem with 100Hz ripple during distorted grid conditions. A double integration method (DIM) is administered for the synchronization of a 3-phase inverter under non-ideal grid conditions. It is important for DIM implementation to remove the DC offset or integrating constants of pure integrators without involving any phase shift. This method is also compared with conventional SRF-PLL based on mathematical modelling and simulations using a MATLAB/Simulink toolbox. The results are verified based on ideal and non–ideal grid conditions and also tested on grid-connected 3-phase Inverter.

Experimental study on an enhanced integral force feedback controller for active damping

In this paper, an enhanced integral force feedback controller is proposed for implementing active damping. Compared with the classical integral force feedback, the pure integrator is replaced with a combination of a first-order low-pass filter and a proportional term. The control performance of the proposed controller is examined on a single-degree-of-freedom host system. In order to better understand the physics behind, a full equivalent mechanical model is derived. It is found that the first-order low-pass filter is mechanically equivalent to a spring and a damper connected in parallel. The proportional term mechanically represents a spring which is connected in series with the inherent actuator spring. The optimal control parameters are numerically obtained with the ℋ∞ optimisation criterion. The analysis shows that the optimal feedback gain can be practically taken the same as that of the classical integral force feedback controller in the sense that the difference between the resultant control performance is negligible. The numerical study is also experimentally validated. The obtained results are found to correspond well with the theoretical developments.

Simple and low-cost motion-sensorless control approach for the IPMSM with elimination of DC offset and steady-state error

Voltage type flux observer has attracted much attention because of its less mathematical calculations and ease of implementation. The only issue with the flux estimation approach is the integration mechanism; using a pure integrator may cause integrator saturation and a DC bias issue, whereas using the low pass filter (LPF) and a self-adaptive band-pass filter (SABPF) would result in magnitude and phase angle errors. This work offers an improved flux linkage estimation approach with a proportional integral (PI) DC offset compensator, resolving the DC drift issue associated with the observer’s pure integrator. Compared to the standard voltage type flux observer, the DC offset is removed, the LPF and phase adjustment are eliminated, and low-speed armature position estimate accuracy is improved. The proposed method can reduce calculation. As a result, the control period is reduced. The Matlab Simulink framework findings are presented to validate the performance and effectiveness of the proposed strategy.

Dissociating effects of aging and genetic risk of sporadic Alzheimer’s disease on path integration

Path integration is a spatial navigation ability that requires the integration of information derived from self-motion cues and stable landmarks, when available, to return to a previous location. Path integration declines with age and Alzheimer’s disease (AD). Here, we sought to separate the effects of age and AD risk on path integration, with and without a landmark. Overall, 279 people participated, aged between 18 and 80 years old. Advanced age impaired the appropriate use of a landmark. Older participants furthermore remembered the location of the goal relative to their starting location and reproduced this initial view without considering that they had moved in the environment. This lack of adaptative behavior was not associated with AD risk. In contrast, participants at genetic risk of AD (apolipoprotein E ε4 carriers) exhibited a pure path integration deficit, corresponding to difficulty in performing path integration in the absence of a landmark. Our results show that advanced-age impacts landmark-supported path integration, and that this age effect is dissociable from the effects of AD risk impacting pure path integration.

Rotor Speed and Position Estimation Analysis of Interior PMSM Machines in Low and Medium-High Speed Regions Adopting an Improved Flux Observer for Electric Vehicle Applications

This paper proposes a nonlinear flux linkage observer for the PMSM speed controls without motion sensors, introducing the deviation among the real stator flux linkage and an estimated stator flux linkage to suppress feedback and integral flux drift. In the position detection of an interior PMSM without a speed sensor, the traditional back EMF integration method uses a pure integrator, or LPF, to estimate the stator flux. Its inherent defects inevitably lead to inaccurate flux estimation, which directly affects the estimation of the motor mover position, resulting in the decline in motor control operation and the distortion of phase current. This paper uses an improved integrator with adaptive compensation. The projected value of the stator flux linkage has been derived from the estimated value of the rotor permanent magnetic flux linkage position angle and the algebraic model (m-model) of the stator flux linkage, along with a synchronous coordinate system. The IPMSM stator coil flux linkage obtained from the stator coil current and integral voltage models in the static coordinate system is compared to form a feedback closed-loop to suppress the integral drift, and using the cross-product approach of the actual and estimated flux linkage yields the projected value of the IPMSM rotor speed and position through a PLL. Compared with the existing motion-sensorless observers, the methodology proposed in this article is simple and exhibits better dynamic and static estimation performance. Extensive and comprehensive MATLAB computer simulation and experimental findings validate the proposed motion-sensorless control mechanism.

Institutionalizing University-Business Innovation Systems in an Innovation Economy

The purpose, design and operation of universities and institutions of higher learning are being transformed. The transformations are requiring universities to lead the process of innovation. Collaboration with stakeholders is accelerated through innovation ecosystems that are functional in some universities. Innovation hubs are powerhouses of innovations at the apex of science and technological advancement. Traditional university designs have their strength in pure science but limit interdisciplinary integration and innovation. Government, private sector and philanthropists are key funders of innovation projects. Universities with a central role in the national and global innovation system exhibit varying impact, a few have exceedingly succeeded in this endeavor and innovation systems are avenues to have national and regional impact. A university is a place of discovery where academics, researchers, government, students, community and companies work together in an innovation ecosystem to develop solutions and products that have an impact on our society. Institutionalizing innovation laboratories is a winning strategy for powering science-led economies.

Improved Deadbeat Predictive Thrust Control for Linear Induction Machine With Online Parameter Identification Based on MRAS and Linear Extended State Observer

This paper proposes an improved deadbeat predictive thrust control (IDPTC) for linear induction machine (LIM) drives based on online parameter identification. First, to achieve fast thrust dynamic response with low thrust ripples, a DPTC method is induced based on the reference primary flux vector calculator and discrete-time LIM model. Second, a novel online magnetizing inductance identification is designed based on back electromotive force model reference adaptive system (MRAS) and linear extended state observer. Compared to the conventional MRAS identification strategy, there is no pure integration and differential operation in both reference and adaptive models for the proposed method, so that integral initial values, dc bias and high-frequency-noise amplification problems can be solved. Then, to improve the robustness of DPTC against magnetizing inductance mismatch, the proposed online parameter identification is further combined with the DPTC method, in which the flux can also be estimated as an intermediate variable without conventional parameter-based flux observer. Finally, comprehensive simulation and experiments have been conducted on one 3 kW arc induction machine, showing that the proposed method can effectively eliminate the influence of magnetizing inductance mismatch on the control performance and significantly improve the parameter robustness compared to the existing DPTC methods.

FEA Assisted Optimization of Bump Shear Test Method for Assessment of Back-End-of-Line Mechanical Integrity

An enhanced Cu pillar bump shear test (BST) method has been developed to quantify wafer level back-end-of-line (BEOL) mechanical integrity and assess the risk of white bump failure. First, three different types of failure mode in the BST and the one that corresponds to the white bump failure in which delamination occurs at an ultra-low-k (ULK) dielectric layer, were identified by studying the load-displacement data together with focused ion beam (FIB) and scanning electron microscopy (SEM) analysis. To find the reason for different failure modes in BST and the effects of BST conditions, first, the difference in the stress modes between the bump shear test and the assembly solder reflow process was compared using finite element analysis (FEA) stress simulations. Then, parametric studies on the bump shear angle and the bump shear height were performed to find the optimal conditions at which the BST stress modes best mimic those of the solder reflow. Based on these studies, special high Cu pillar bump test samples were built in order to apply the optimal shear height and angle condition. The new optimal BST method has shown to significantly increase the probability of ULK delamination failure mode and was shown to be in good agreement with reflow hammer test results. Also, the method was used to verify the effect of metal density as well as process and design changes. Finally, a machine learning based correlation for quantifying the pure BEOL integrity regardless of the bump and far-BEOL dimensions was developed for application of the method to various products.

Clinically normal elderly adults at genetic risk for sporadic Alzheimer’s disease have a path integration deficit

AbstractBackgroundAlzheimer’s disease (AD) is associated with cognitive impairment, including spatial disorientation. Disorientation may be an early indicator of AD because spatial navigation relies on entorhinal cortex, the first cortical region affected by AD pathology. To test the hypothesis that spatial navigation declines in preclinical AD, we investigated age and genotype effects on a virtual path integration task, the "Apple Game" (Bierbrauer et al. 2020).MethodParticipants navigated in a virtual field and had to drop a basket to their initial location. Difficulty varied according to two parameters: (1) the number of interim locations (distractor) participants had to visit (0, 1, or 2); and (2) the presence or absence of a landmark. We recruited 145 clinically normal participants (MMSE>24/30, median age= 64). We genotyped the apolipoproteinE (APOE) gene, the ε4 allele of which is a risk factor for AD. We classified participants as E4 (n=41) if they had at least one ε4 allele and E3 (n=104) otherwise (table 1). We used linear mixed models to predict the drop error, i.e., the Euclidean distance between the correct and the actual drop location. The two components of the drop error, the angle and distance errors, were analyzed.ResultsThe drop error increased with age. In trials with no distractor and no landmark, we observed higher drop error for E4 than E3 participants older than 70 years (fig.1), suggesting a deficit in pure path integration for oldest E4 carriers. This deficit was due to higher angle error (fig.2) rather than distance error (fig.3). In trials with distractors, performance dropped to chance level for all participants above 50 years (fig.4), suggesting the task was too difficult in general. In trials with landmark, the error was not influenced by the APOE genotype.ConclusionThis spatial navigation task detected a deficit in pure path integration in elderly E4 carriers, when the task was not too difficult. The deficit may reflect an impairment in grid cells localized in the entorhinal cortex. Indeed, this group has probably the most AD neuropathology brain deposit. By contrast, landmark‐based navigation was impaired with age but not related to AD risk.

Improved Position Sensorless Piston Stroke Control Method for Linear Oscillatory Machine via an Hybrid Terminal Sliding-Mode Observer

Since the piston stroke of linear oscillation machine (LOM) is very important for the safe and reliable operation of the system, it is necessary to effectively control the piston stroke. Besides, considering that the use of position sensor will reduce the system reliability, so the accurate position sensorless method is needed to obtain the stroke signals. In this article, a hybrid terminal sliding-mode observer is designed by combing a second-order nonsingular terminal sliding mode (SNTSM) and a high-order sliding-mode (HOSM) to estimate the back-electromotive force signals of the LOM. The SNTSM surface is selected to ensure that the system state variables can converge in a finite time and the HOSM control law is designed by introducing a variable exponential reaching law, which can strengthen the stability of the observer and greatly reduce the sliding chattering. Since the piston stroke is calculated by integrating the estimated piston velocity, the pure integral saturation will occur due to the presence of dc components in the measured current and voltage. In order to cope with this problem, one self-adaptive band-pass filter is introduced to replace the pure integrator, which can obtain smooth stroke signals with almost no amplitude and phase offset. Moreover, the current amplitude controller is designed to improve the control accuracy and response speed. Finally, comprehensive simulation and experimental results are provided to verify the effectiveness and the superiority of the proposed method.

Control algorithm for coordinated operation of wind-solar microgrid standalone generation system

ABSTRACT In this paper, a wind-driven self-excited induction generator (SEIG) combining solar photovoltaic (SPV) and battery storage has been successfully demonstrated. A second-order sequence filter-based frequency locked loop (SOSF-FLL) control is implemented for operating the voltage source converter (VSC). The SOSF-FLL method is designed by replacing two second-order low pass filter (LPF) pure integrators with two reduced order generalized integrators (ROGIs). The SOSF-FLL has a nonlinear control feedback system. The major contributions in this study include: 1. Implementation of SOSF-FLL control to generate reference source currents for VSC and evaluate the amplitude of load current component under intermittent condition of renewable energy sources (RESs) and nonlinear load, 2) The control algorithm with VSC performs numerous functions such as voltage/frequency regulation, load leveling, harmonic reduction, active/reactive power compensation and reduces the overall power quality problems, 3) Through DC-link voltage management, a bidirectional converter (BDC) with battery storage optimizes the best power flow to provide power balancing between the sources and the unbalanced load, 4) Under diverse operating situations, an incremental conductance (INC)-based maximum power point tracking approach with BDC control provides quick system convergence and support frequency. Moreover, a comparison is carried out between SOSF-FLL control and conventional control algorithms. The settling time of the proposed control is very less than one cycle (20 ms) within 2% described limit, whereas the conventional control algorithms show oscillations of more than 5% during the load dynamics. Despite the load current THD 24.41%, the proposed control is able to obtain supply current THD at 4.23%, which is less than 5% as per IEEE-519 standard. The proposed microgrid (MG) is constructed in MATLAB/Simulink and experimental prototype environment, and its dynamic response is investigated under dynamic conditions of RESs and nonlinear load conditions.

A Stroke Estimation Method for Linear Oscillatory Machine Using an Improved Sliding Mode Observer

For the linear compressor system driven by a linear oscillatory machine (LOM), the piston stroke is very important to realize the high working efficiency for the whole system. In order to obtain precise and reliable piston stroke signals without using the position sensor, this article proposes a stroke estimation method for the LOM using an improved sliding mode observer (SMO). For the improved SMO, the integral sliding surface is chosen to reduce the chattering phenomenon and the steady-state error of the system, and a novel reaching law is introduced to construct the sliding control law, which can further reduce the influence of the sliding chattering. Due to the piston stroke being obtained by integrating the back electromotive force (EMF) as estimated by the improved SMO, the pure integration saturation problem will occur due to that the measured current and voltage signals always contain some dc components. In order to cope with this problem, a self-adaptive bandpass filter is designed, which can obtain a filtered signal with almost no amplitude and phase deviation by adaptively adjusting its center frequency. Simulation and experimental results confirm that the proposed improved SMO has higher stroke estimation accuracy than the back EMF integration and the conventional SMO.

Online Identification Strategy of Secondary Time Constant and Magnetizing Inductance for Linear Induction Motors

In this article, an online dual-parameter identification strategy for linear induction motors (LIMs) is investigated. Considering the influence of unique end effects in LIMs and the critical impact on control system performance, the magnetizing inductance and secondary time constant are chosen as the targets of estimation. Compared with rotary induction motors, the influence factors in LIMs are much more complex, which can heavily affect the parameter value especially for the high-speed condition. As a result, the online identification is vital for high performance applications. Based on the model reference adaptive system with magnetizing current as state variable, this article starts from the adaptive law of secondary time constant derived by Popov's criterion for hyperstability. Then, the physical significance and stable range are analyzed in details, based on which a handy magnetizing inductance identification method is combined. To further ensure the precision of estimation, one simplification scheme is specially designed. Besides, to eliminate the pure integrator, the derivatives of magnetizing current are chosen as the state variables. Finally, the dual-parameter identification system that utilizes only one PI controller and has low coupling property is constructed. Comprehensive simulation and experiments have fully demonstrated the effectiveness and superiorities of the proposed method.

Model predictive control for gas turbine shaft speed based on model compensation using extended state observer

Gas turbine engines have offered advanced power generation with relatively small size on marine vessels. The operational flexibility has high control requirements for shaft speed regulation. Model predictive control provides a methodology for safe and efficient operation of gas turbines. However, when working at partial load, the controller degrades due to the mismatch between predictive model in model predictive control and dynamics of gas turbine. To deal with the issue of model adaptability in model predictive control, model compensation–based model predictive control is proposed for the gas turbine operation. The dynamics of the plant is modified by the extended state observer to get close to the pure integrator. The model predictive control is devised based on the modified plant. The wide-range load regulation and disturbance rejection of gas turbine have been improved by leveraging the benefits of model compensation–based model predictive control.

ACCOUNTANTS AND AUDITORS' PERCEPTIONS OF TECHNOLOGY AND ATTITUDE OF INTEGRITY IN PREVENTING FRAUD

Fraud can be interpreted as fraud which contains the meaning of irregularities and acts against the law, which are carried out intentionally for certain purposes. The role of accountants is often questioned when it comes to financial statement fraud. The audit expectation gap indicates that public expectations are not met for the role of accountants in all fraud cases. This study aims to see if there is a common perception between accountants and auditors in determining the most effective technology and integrity attitude in preventing fraud. Data collection was carried out by distributing a questionnaire link to 110 accounting alumni of the Riau Caltex Polytechnic who graduated from 2015 to 2019 and worked as accountants or auditors. Hypothesis testing is done by using independent sample t-test or different test t-test. The results showed that there were differences in perceptions between accountants and auditors in the selection of technology, namely protection against viruses and the installation of CCTV surveillance camera equipment. However, overall, the results showed no difference. Accountants and auditors have the same perception regarding the attitude of pure integrity which is chosen to be the most effective attitude of integrity to have in order to prevent fraud.

A Straightforward Quadrature Signal Generator for Single-Phase SOGI-PLL With Low Susceptibility to Grid Harmonics

Suppressing the negative effects of grid voltage harmonics on the estimated frequency of a phase-locked loop (PLL) is a challenge in literature. This article proposes an easy-to-implement quadrature signal generator (QSG) to attenuate the oscillations on the estimated frequency in single-phase grid-connected inverters, which use second-order generalized integrator (SOGI)-PLL. It is shown that SOGI exerts a stronger filtering effect in generating the quadrature signal than the in-phase signal. Against this background, in this work, a modified integrator is introduced into the path of the in-quadrature signal to generate another in-phase component with much lower harmonic content. The proposed method imposes only a small computational burden on the existing SOGI-PLL compared to the previously presented methods that address the input voltage harmonic problem. Moreover, this method can work properly within the allowable range of grid voltage frequency deviations. The proposed integrator benefits from an error-decaying mechanism to overcome dc drift in pure integrators. The integrator has been designed based on theoretical equations. The validity of the proposed QSG and theoretical equations is evaluated using simulations and experimental studies. A fixed-point representation of the proposed QSG is also provided for implementation on low-cost microcontrollers.