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In this paper, an adaptive neural network (NN) control scheme is developed for a class of stochastic nonlinear systems with time-varying full state constraints. In the controller design, RBF NNs are employed to approximate the unknown terms, and the backtracking technique is introduced to overcome the restriction of matching conditions. At the same time, tangent type time-varying barrier Lyapunov functions (tan-TVBLFs) are constructed to ensure the full state constraints are never violated, where tan-TVBLFs are beneficial to integrate constraint analysis into a common method. Furthermore, the Lyapunov stability theory is used to prove that all closed-loop signals are semiglobal uniformly ultimately bounded in probability and error signals remain in the compact set do not violate the time-varying constraints. A simulation example will be used to exhibit the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

In this letter, we demonstrate high performance black phosphorus (BP) top gate transistors using molecular layer deposition (MLD) of high-quality alucone films as top gate dielectrics. Ethylene glycol was used as an oxygen precursor instead of using water or ozone as precursor, which typically results in the oxidation of BP surface. The carrier mobility of BP transistors using the alucone dielectric reaches 216 cm $^{2}/\text{V}\cdot \text{s}$ at room temperature, which is 4.5 times higher than that of with Al2O3dielectrics using O3. The ON current and ON–OFF ratio of the alucone-based transistors are also much higher than the other two types of devices. Meanwhile, we observe a metal-insulator transition in the BP top gate with alucone films, suggesting an excellent interface quality with efficient electro-static gate control. This result shows great potential of MLD for applications in high-quality BP top gate devices. [ABSTRACT FROM AUTHOR]

Achieving low contact resistance is one of the main challenges for black phosphorus (BP) transistors for both electronic and optoelectronic applications. Here we demonstrate a novel yet feasible lithium doping technique, which greatly reduces the contact resistance from 2 to 0.85 $\text{k}\Omega \cdot \mu \text{m}$ and results in more than 2.5 times improvement in output current and ON/OFF ratio. This can be mainly attributed to the high hole doping density by lithium bis(trifluoromethylsulfonyl)-imide, which results in a narrower carrier injection barrier at the source end. The ON/OFF ratios of BP field-effect transistors with contact doping at 300 and 20 K are 432 and $7.2 \times 10^{5}$ , respectively. A high drain current of $773~\mu \text{A}/\mu \text{m}$ with a $0.56~\mu \text{m}$ channel length at 20 K is also demonstrated. The doping technique provides a valid way to improve the overall performance of BP transistors. [ABSTRACT FROM AUTHOR]

As an emerging two-dimensional material, few-layer black phosphorus (BP) shows great potential in nanoelectronics and nanophotonics due to its high carrier velocity. However, non-optimized gate dielectrics often degrade the performance of BP devices severely. In this letter, we demonstrate high-performance BP devices using a novel HfLaO as back gate dielectric with improved interface quality. High current exceeding 1.15 mA/ \mu \textm has been achieved at 20 K for BP transistors with improved noise spectral density. Moreover, BP photodetectors with a record high photoresponsivity up to 1.5\times 10^8 A/W and fast response time of 10~\mu \texts at 300 K are demonstrated. Excellent photoresponse in a broadband spectrum range from 514 to 1800 nm at 70 K has also been achieved. [ABSTRACT FROM AUTHOR]

The dual-stage actuation system based on a newly developed slider-level thermal microactuator has been demonstrated to be able to achieve 6 kHz control bandwidth with 60 kHz sampling rate. This paper reports the saturation control for the thermal microactuator. The aim is to release the thermal microactuator from saturation as soon as possible once the saturation occurs, and to maintain the system to be stable when the microactuator saturates. Typically, the antiwindup compensation scheme is used, due to its benefits of easy design and implementation as well as effectiveness for the thermal microactuator. Simulation and experimental testing shows the performance of this saturation control, when the dual-stage system undertakes a seeking task, especially a long distance seeking such as 40 and 80 nm seekings. [ABSTRACT FROM PUBLISHER]

This paper considers track-following control of four-bar structured hard disk drive (HDD) systems. Compared with the traditional single-arm HDD, the four-bar structure potentially leads to higher achievable closed-loop bandwidth, but also brings challenges in control design due to nonlinearity. In track-following control design, exact linearization is impossible in practice due to mechanic resonances and measurement constraints. In this paper, instead of exact linearization, we propose a kind of prefilter to compensate for the low-frequency nonlinearities so that the compensated system has the same linear approximation at different track positions subjected to different high-frequency resonances. With this prefilter, many existing track-following control methods can be applied to the compensated plant. In this paper, H\infty loop shaping is used and simulation results show that the resulting controller preserves similar track-following performance at different track positions. [ABSTRACT FROM PUBLISHER]

This paper is devoted to the control design and implementation of the dual-stage actuation system with a newly developed microthermal actuator (MTA) as the secondary actuator. The characterization and modeling of this new MTA is presented for controller design. Its performances such as stroke, time constant, and a good linearity are exhibited. The controller design of the MTA-based dual-stage actuation system is then proposed, and aims to push the bandwidth with the MTA. The simulation and the experimental testing have demonstrated the achievable 6-kHz bandwidth with 60-kHz sampling rate, the MTA displacement of 15 nm at 4 kHz, and 0.1-ms seeking time for 40-nm seeking length. [ABSTRACT FROM AUTHOR]