Search

Presents information on a study on the issues on high-speed laser zone texturing of magnetic disk substrates with improved quality. Tooling; Laser bump quality; Conclusion.

The human ankle joint interacts with the environment during ambulation to provide mobility and maintain stability. This association changes depending on the different gait patterns of day-to-day life. In this study, we investigated this interaction and extracted kinematic information to classify human walking mode into upstairs, downstairs, treadmill, overground and stationary in real-time using a single-DoF IMU axis. The proposed algorithm’s uniqueness is twofold - it encompasses components of the ankle’s biomechanics and subject-specificity through the extraction of inherent walking attributes and user calibration. The performance analysis with forty healthy participants (mean age: 26.8 ± 5.6 years yielded an accuracy of 89.57% and 87.55% in the left and right sensors, respectively. The study, also, portrays the implementation of heuristics to combine predictions from sensors at both feet to yield a single conclusive decision with better performance measures. The simplicity yet reliability of the algorithm in healthy participants and the observation of inherent multimodal walking features, similar to young adults, in elderly participants through a case study, demonstrate our proposed algorithm’s potential as a high-level automatic switching framework in robotic gait interventions for multimodal walking. [ABSTRACT FROM AUTHOR]

Electrooculography (EOG) can be used to measure eye movements while the eyelids are open or closed and to assist in the diagnosis of certain eye diseases. However, challenges in biosignal acquisition and processing lead to limited accuracy, limited resolution (both temporal and spatial), as well as difficulties in reducing noise and detecting artifacts. Methods such as finite impulse response, wavelet transforms, and averaging filters have been used to denoise and enhance EOG measurements. However, these filters are not specifically designed to detect saccades, and so key features (e.g., saccade amplitude) can be over-filtered and distorted as a consequence of the filtering process. Here we present a model-based fusion technique to enhance saccade features within noisy and raw EOG signals. Specifically, we focus on Westheimer (WH) and linear reciprocal (LR) eye models with a Kalman filter. EOG signals were measured using OpenBCI’s Cyton Board (at 250 Hz), and these measurements were compared with a state-of-the-art EyeLink 1000 (EL; 250 Hz) eye tracker. On average, the LR model-based KF produced a 47% improvement of measurement accuracy over the bandpass filters. Thus, we conclude that our LR model-based KF outperforms standard bandpass filtering techniques in reducing noise, eliminating artifacts, and restoring missing features of saccade signatures present within EOG signals. [ABSTRACT FROM AUTHOR]

High mobility thin film transistors (TFTs) based on zinc oxynitride (ZnON) semiconductor were fabricated onto polyethylene-2.6-naphthalate (PEN) substrates. The application of a dual gate structure enhanced the field-effect mobility from 65.8 to 147 cm2/ $\text{V}\cdot \text{s}$ , which is generally attributed to the bulk accumulation effect. Dual gate driving also results in improved device stability with respect to bias and illumination stress. This is most likely due to the fact that the bulk channel confines the charge carriers away from the semiconductor-dielectric interfaces, where charge trapping is anticipated. The electrical performance of dual gate devices did not change significantly after 5,000 bending cycles, while the single gate transistors exhibited clear degradation. [ABSTRACT FROM AUTHOR]

This paper proposes a sensorless speed-control method based on an innovative adaptive synchronous-frequency tracking-mode observer (AFTO) for surface permanent-magnet synchronous motor drives. The method uses the AFTO function, based on proportional resonance control, to track stator currents adaptively under variable-frequency scenarios. Then, an orthogonal phase-locked loop supports the estimation of rotor speed. The convergence of stator-current errors guarantees an estimation of the back electromotive force (back EMF) without the influence of harmonic components and the chattering problem. The resulting pure and smooth back EMF provides high-accuracy estimates of the rotor position and speed. Simulations and experimental results are given to provide further validation of the proposed rotor-position and speed estimation schemes under different speed scenarios. The improved control method also maintains high estimation accuracy for rotor speed and position at low speeds. [ABSTRACT FROM AUTHOR]

In order to improve the performance of surface permanent magnet synchronous motor drives, a novel sensorless drive scheme is proposed in this paper, which is based on the virtual third-harmonic back EMF incorporating a fractional-N phase-locked loop (FN-PLL) and a synchronous frequency-extract filter (SFF). A simple low-pass filter based circuit is used to obtain the commutation points through the virtual third-harmonic back EMF. After that, an FN-PLL is applied to obtain continuous rotor position angles. On this basis, the SFF-based compensation is proposed to compensate the detecting error adaptively. Meanwhile, the field vector control loop for surface PM motor is proposed, which is based on the proposed rotor position detection link and compensation link. An experimental high-speed magnetically suspended blower platform is built. The effectiveness and the feasibility of the proposed method are validated with experimental results. [ABSTRACT FROM AUTHOR]

Inverter-based distributed generation (DG) system is becoming an attractive solution for high penetration of renewable energy sources to the main grid. DG system should be able to supply power to the local loads whenever necessary even in case of utility power outage. Thus, the inverters in DG systems are expected to operate in both grid-connected and islanded mode, where they are acting as a current source for the ac grid and a voltage-source for the load, respectively. Transition between modes of operation is nontrivial and can cause deviations in voltage and current, because of mismatch in frequency, phase, and amplitude between the inverter output voltage and the grid voltage. Thus, it is necessary to have seamless transition between grid-connected and islanded mode. This paper presents a new control strategy with seamless transfer characteristics for a grid-connected voltage-source inverter using model predictive control (MPC) framework. The main objectives of the proposed predictive controller are: 1) decoupled power control in grid-connected mode, which enables the proposed power electronics interface to provide ancillary services such as reactive power compensation; 2) load voltage control in islanded mode; and 3) seamless transition between modes of operation through proposed synchronization and phase adjustment algorithm. The proposed controller features simplicity to implement since only one cost function should be minimized for all modes of operation, and hence no ambiguity in the control algorithm that could cause mode transition problems. An autotuning strategy for weight factors in MPC cost function is proposed to simplify the weight factor tuning strategy. The stability analysis of the proposed controller is provided. Simulation and experimental results validate the expected performance and effectiveness of the proposed control strategy. [ABSTRACT FROM PUBLISHER]

To improve the performance of the surface permanent magnet synchronous motor drives, a sensorless control scheme based on the sliding-mode observer with an orthogonal phase-locked loop (PLL) incorporating two synchronous frequency-extract filters (SFFs) is proposed. The rotor position estimation errors are analyzed. The analysis results show that the harmonic errors of the estimated signal are hard to eliminate completely. Therefore, an improved adaptive notch filter - The SFF is proposed to extract the fundamental wave of the rotor position estimation before applying to the PLL. This method of the PLL combined SFFs can compensate the estimated back electromotive force harmonic error efficiently and adaptively. An experimental driveline system used for testing the electrical performance of the developed magnetically suspended motor is built. The effectiveness and the feasibility of the proposed method are validated with the experimental results. [ABSTRACT FROM PUBLISHER]

In this paper we contrast the application of two different methods for verifying soundness of workflow. The first approach considers the structure of the workflow net and proposes an analytical process that takes into account the incidence matrix and a strict positive vector to prove soundness. The second method is based on decision process Petri nets theory showing that the problem of finding an optimum trajectory for validation of well-formed workflow is solvable. The advantage of both solutions is that to tackle the soundness verification problem use the Lyapunov stability theory which corresponds to an analytical method for Petri nets. We validate our statement theoretically and by an application example. [ABSTRACT FROM PUBLISHER]

A transformerless hybrid series active filter is proposed to enhance the power quality in single-phase systems with critical loads. This paper assists the energy management and power quality issues related to electric transportation and focuses on improving electric vehicle load connection to the grid. The control strategy is designed to prevent current harmonic distortions of nonlinear loads to flow into the utility and corrects the power factor of this later. While protecting sensitive loads from voltage disturbances, sags, and swells initiated by the power system, ridded of the series transformer, the configuration is advantageous for an industrial implementation. This polyvalent hybrid topology allowing the harmonic isolation and compensation of voltage distortions could absorb or inject the auxiliary power to the grid. Aside from practical analysis, this paper also investigates on the influence of gains and delays in the real-time controller stability. The simulations and experimental results presented in this paper were carried out on a 2-kVA laboratory prototype demonstrating the effectiveness of the proposed topology. [ABSTRACT FROM PUBLISHER]