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A kind of launching platform driven by two permanent magnet synchronous motors which is used to launch kinetic load to hit the target always faces strong parameter uncertainties and strong external disturbance such as the air current impulsion which would degrade their tracking accuracy greatly. In this paper, a practical method which combines adaptive robust control with neural network-based disturbance observer is proposed for high-accuracy motion control of the launching platform. The proposed controller not only accounts for the parametric uncertainties but also takes the external disturbances into account. Adaptive control is designed to compensate the former, while neural network-based disturbance observer is designed to compensate the latter respectively and both of them are integrated together via a feedforward cancellation technique. A new kind of parametric adaptation and weight adaptation strategy is designed by using the linear combination of the system's tracking error and the weight estimation error as a driving signal for parametric adaptation and disturbance approximation. The stability of the novel control scheme is analyzed via a Lyapunov method and this method presents a prescribed output tracking performance in the presence of both parameter uncertainties and unmodeled nonlinearities. Extensive comparative simulation and experimental results are obtained to verify the high-performance of the proposed control strategy. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

There is a lot of dynamic knowledge in real world, the traditional semantic Web ontology and context-aware system were not suitable to deal with the dynamic knowledge. To solve this problem, this paper proposed a pragmatic Web driven context-aware system by virtue of the advantage of pragmatic Web in expressing dynamic knowledge, and designed its framework. This system employed an efficient context capturing technique to improve the accuracy of captured context information, and deduced the high-level context with decision capability by reasoning. Finally, achieving user-centric personalizes recommendation service by a method of agent based context-aware service discovery. [ABSTRACT FROM AUTHOR]

In this paper, two-dimensional (2D) transient simulations of an AlGaN/GaN high-electron-mobility transistor (HEMT) are carried out and analyzed to investigate the current collapse due to trapping effects. The coupling effect of the trapping and thermal effects are taken into account in our simulation. The turn-on pulse gate-lag transient responses with different quiescent biases are obtained, and the pulsed current–voltage (I–V) curves are extracted from the transients. The experimental results of both gate-lag transient current and pulsed I–V curves are reproduced by the simulation, and the current collapse due to the trapping effect is explained from the view of physics based on the simulation results. In addition, the results show that bulk acceptor traps can influence the gate-lag transient characteristics of AlGaN/GaN HEMTs besides surface traps and that the thermal effect can accelerate the emission of captured electrons for traps. Pulse transient simulation is meaningful in analyzing the mechanism of dynamic current collapse, and the work in this paper will benefit the reliability study and model development of GaN-based devices. [ABSTRACT FROM AUTHOR]

A new analytical model for the surface electric field distribution and breakdown voltage of the silicon on insulator (SOI) trench lateral double-diffused metal-oxide-semiconductor (LDMOS) is presented. Based on the two-dimensional Laplace solution and Poisson solution, the model considers the influence of structure parameters such as the doping concentration of the drift region, and the depth and width of the trench on the surface electric field. Further, a simple analytical expression of the breakdown voltage is obtained, which offers an effective way to gain an optimal high voltage. All the analytical results are in good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

A low on-resistance (Ron, sp) integrable silicon-on-insulator (SOI) n-channel lateral double-diffused metal-oxide- semiconductor (LDMOS) is proposed and its mechanism is investigated by simulation. The LDMOS has two features: the integration of a planar gate and an extended trench gate (double gates (DGs)); and a buried P-layer in the N-drift region, which forms a triple reduced surface field (RESURF) (TR) structure. The triple RESURF not only modulates the electric field distribution, but also increases N-drift doping, resulting in a reduced specific on-resistance (Ron, sp) and an improved breakdown voltage (BV) in the off-state. The DGs form dual conduction channels and, moreover, the extended trench gate widens the vertical conduction area, both of which further reduce the Ron, sp. The BV and Ron, sp are 328 V and 8.8 m&ohmega;.cm2, respectively, for a DG TR metal-oxide-semiconductor field-effect transistor (MOSFET) by simulation. Compared with a conventional SOI LDMOS, a DG TR MOSFET with the same dimensional device parameters as those of the DG TR MOSFET reduces Ron, sp by 59% and increases BV by 6%. The extended trench gate synchronously acts as an isolation trench between the high-voltage device and low-voltage circuitry in a high-voltage integrated circuit, thereby saving the chip area and simplifying the fabrication processes. [ABSTRACT FROM AUTHOR]

A zero‐bias microwave detector using an AlGaN/GaN‐on‐Si lateral diode featuring a recessed metal/Al2O3/III‐nitride (MIS) gated hybrid anode (MG‐HAD) is experimentally demonstrated. The forward turn‐on voltage of the MG‐HAD is determined by the threshold‐voltage of the 2DEG channel beneath the recessed MIS‐gate, and thus the nonlinearity of the device at zero bias can be flexibly modulated by gate recessing. The optimal trench depth of the MIS‐gate for zero‐bias detection was designed and experimentally determined to be ∼23 nm, which enables a high‐curvature coefficient of 78 V−1 at zero bias. The first‐order voltage sensitivity, βV, is as high as 7.8 mV/μW. To the best of the authors' knowledge, these values are the highest reported for GaN‐based zero‐bias detectors to date. [ABSTRACT FROM AUTHOR]

In this study rectangular AlGaN/AlN/GaN heterostructure field-effect transistors (HFETs) with 22-nm and 12-nm AlGaN barrier layers are fabricated, respectively. Using the measured capacitance–voltage and current–voltage characteristics of the prepared devices with different Schottky areas, it is found that after processing the device, the polarization Coulomb field (PCF) scattering is induced and has an important influence on the two-dimensional electron gas electron mobility. Moreover, the influence of PCF scattering on the electron mobility is enhanced by reducing the AlGaN barrier thickness. This leads to the quite different variation of the electron mobility with gate bias when compared with the AlGaN barrier thickness. This mainly happens because the thinner AlGaN barrier layer suffers from a much stronger electrical field when applying a gate bias, which gives rise to a stronger converse piezoelectric effect. [ABSTRACT FROM AUTHOR]

We report on the temperature-dependent dc performance of AlGaN/GaN polarization doped field effect transistors (PolFETs). The rough decrements of drain current and transconductance with the operation temperature are observed. Compared with the conventional HFETs, the drain current drop of the PolFET is smaller. The transconductance drop of PolFETs at different gate biases shows different temperature dependences. From the aspect of the unique carrier behaviors of graded AlGaN/GaN heterostructure, we propose a quasi-multi-channel model to investigate the physics behind the temperature-dependent performance of AlGaN/GaN PolFETs. [ABSTRACT FROM AUTHOR]