Future sixth generation (6G) communications are expected to support robotic control tasks in applications such as industrial automation and emergency response, where sensors, computing units, and robots are interconnected via nervous system-like networks to form sensing-communication-computingcontrol (SC 3 ) closed loops.However, the limited battery capacities of devices within these SC 3 loops constrain operational duration and degrade control efficiency, particularly in remote or postdisaster scenarios.To address this challenge, wireless power transfer (WPT) can be leveraged to provide continuous energy supply for SC 3 closed loops.In this paper, we investigate a wireless-powered SC 3 system, where a satellite transfers energy via radio frequency (RF) signals to support the communication and computing processes of multiple SC 3 closed loops.By accounting for the intricate coupling among computing, communication, and energy transfer, we propose a holistic design framework to enhance overall control performance.Specifically, we adopt the linear quadratic regulator (LQR) cost as the performance metric and formulate a sum LQR cost minimization problem.The uplink/downlink transmit power, bandwidth allocation, computing capability, communication/computing time allocation, and WPT power allocation are jointly optimized.We recast the problem into a more tractable form and develop an iterative algorithm to solve it.For the special case of a single loop, we further analyze the properties of optimal solutions in energylimited scenarios to provide insights for practical parameter configuration.Simulation results demonstrate the performance gains of the proposed scheme.

To overcome traditional limitations in handling complex disturbances, a novel fractional-order second-order sliding mode control (FOSOSMC) is developed for a class of nonlinear systems in the presence of matched and mismatched uncertainties, ensuring the properties of stability and dynamic performance. The main novelties are highlighted as follows. Firstly, a structurally flexible continuous SOSMC manifold incorporating FO calculus is constructed by taking into account the design of a family of sliding variables, which ensures that the state trajectory can converge to the equilibrium point accurately in a finite time and address the chattering problem owing to its memory and hereditary properties, while uniformly compensating for mismatched uncertainties. Furthermore, the straightforward sliding manifold structure allows for diverse designs of control laws. For simple single-input single-output systems, their fast convergence and high precision under lumped uncertainties can be guaranteed by combining the FOSOSM manifold and a fast-terminal sliding mode-type reaching law. For complex multi-input multi-output systems, a state-dependent adaptive gain is fitted to the FOSOSM manifold to obtain stronger robustness without sacrificing control accuracy or complicating parameter tuning. The global finite-time stability of the closed-loop dynamics is demonstrated by means of Lyapunov functions. Finally, simulation and experimental results verify the excellent control performance of the proposed method for nonlinear systems with uncertainties.

Cooperation between satellite and terrestrial wireless networks promises great potential in meeting fast-growing demands for ubiquitous communications coverage. To tackle spectrum scarcity, spectrum sharing is studied for a hybrid satellite-terrestrial network where satellite links share the same group of time-slotted subcarriers with terrestrial links opportunistically. In particular, with coarse network-wide time synchronization, a time-scale-adaptable spectrum sharing framework is proposed based on a satellite-terrestrial cooperation time scale that can be flexibly adjusted according to practical requirements. For generality, it is assumed that both full and partial frequency reuse could be adopted among the base stations (BSs) and satellite selection is supported when multiple satellites are available. Relying on only statistical channel state information (CSI), joint link scheduling and power control are explored to maximize the average sum rate of the network while ensuring quality of service (QoS) for users. To solve the complicated mixed integer programming (MIP) problem, a low-complexity spectrum sharing scheme is presented based on link-feature-sketching-aided hierarchical link clustering and Monte-Carlo-and-successive-approximation-aided transmit power optimization. Simulation results demonstrate that by link feature sketching, diversity of the links brought by the spatial distribution of the users could be well utilized. The proposed scheme promises a significant performance gain even under strict inter-link interference constraints.

This paper proposes a novel approach for constructing a Chinese fault lexicon for electrical test systems based on the mutual information and information entropy, which consists of three main steps, i.e., vocabulary selection and preprocessing, word vector representation, and similarity calculation. First, by using the term frequency as the performance indicator, the selection and preprocessing for the test fault vocabulary is carried out. Second, a distributed encoding approach is applied to convert the text words into numerical word vectors. Based on the Word2Vec model, the selected test fault vocabulary is transformed into a fixed-length, continuous, dense vector set. Meanwhile, a function of cosine similarity is utilized to compute the index of the vocabulary similarity and further validate the effectiveness and accuracy of the constructed fault lexicon for electrical test systems. Finally, numerical simulations are given to show the effectiveness of this paper.

With the large-scale integration of grid-forming photovoltaic (PV)-storage systems in power systems, the transient stability during its mode transition is a great challenge. In this paper, a virtual synchronous generator (VSG)-based integrated control approach is proposed to realize the smooth switching from the off-grid mode to the grid-connected mode for the grid-forming PV-storage systems. The innovation lies in the elimination of the need for phase-locked loops (PLL) by adjusting the frequency and voltage of VSG for the realization of smooth switching operation while controlling the battery energy storage system via the voltage-current control so that the reliability of the power exchange can be guaranteed at the same time. Simulations validate the effectiveness of this paper with the advantages of reducing the inrush current in the process of grid synchronization and the better stability of the whole system.

Spectrum sharing among the satellite, unmanned aerial vehicle (UAV), and terrestrial components is crucial to alleviate spectrum scarcity in a hybrid maritime communication network (MCN). In the time domain, spectrum sharing optimization based on fine-grained time slices is widely envisioned. However, fine-grained time synchronization is rather challenging due to the large diversity in the link delay. In this paper, we focus on link-cluster-based spectrum sharing based on coordinated link scheduling in terms of subcarrier and time slice allocation. By link-cluster-based scheduling for the satellite links, time-slice-oriented spectrum sharing is realized with coarse time synchronization at time scales much larger than single time slice duration. Only large-scale channel state information (CSI) is utilized for saving cost. An NP-hard mixed integer programming (MIP) problem is formulated, and with the aid of link clustering, a suboptimal spectrum sharing scheme, with only a small performance gap to the optimal one, is proposed. Simulations show that a significant improvement in both energy efficiency and spectrum efficiency could be achieved by the proposed scheme.

The state of energy (SoE) is a critical metric for battery management systems, complementing the state of charge (SoC) in providing comprehensive battery management insights. This paper addresses SoE estimation for lithium-ion batteries by designing a sliding mode observer that utilizes sliding mode control technology to enhance the robustness of the SoE estimation algorithm. Leveraging the correlation between SoC and SoE, this study develops a method to accurately estimate SoC and determine SoE. Additionally, we introduce a sliding mode observer based on the Super-twisting algorithm, which stabilizes the observer by carefully selecting parameters. The effectiveness of the proposed SoE estimation algorithm is validated using Dynamic Stress Test (DST) data, confirming its practical utility.

In this paper, a continuous sliding mode control (CSMC) approach based on a super-twisting algorithm is proposed to improve the efficiency and safety of the lithium-ion battery charger. First, the charger model is established based on the Vienna rectifier and the three-phase interleaved buck converter. Differing from the traditional PI control, a composite control scheme by using the super-twisting algorithm is proposed for the three parts of the system. The sliding surface, the corresponding continuous control law, and the steady analysis are carried out to guarantee the effectiveness of the designed controller. Simulations validate this paper.

An improved virtual impedance droop control (VIDC) strategy based on sliding mode control (SMC) is proposed in this paper to effectively suppress the inter-phase circulating current of parallel three-phase grid-connected inverters. Unlike the traditional VIDC method, the proposed strategy is discussed and improved in four aspects: bus voltage stability, Q-U loop performance, P-f loop performance, and virtual impedance regulation. The generation mechanism of the inter-phase circulating current is emphatically analyzed, and the output voltage difference and power distribution are studied and integrated with the improved VIDC strategy to suppress the circulating current. The simulations are carried out to demonstrate that the improved VIDC strategy is effective in restraining the circulating current in the system while also significantly improving the system's response speed and output accuracy.

Spectrum sharing among the satellite, unmanned aerial vehicle (UAV), and terrestrial components is crucial to alleviate spectrum scarcity in a hybrid maritime communication network (MCN). Fine-grained spectrum sharing based on ms-level time-domain slices is widely envisioned. However, ms-level time synchronization is challenging in the hybrid MCN due to the large diversity in the link delay. To tackle this challenge, we propose a fine-over-coarse spectrum sharing framework based on coordinated link scheduling, which is realized by joint subcarrier and time slice allocation. Specially, by link-cluster-based scheduling with grouped time slice allocation for the satellite links, time-slice-oriented spectrum sharing is realized with coarse time synchronization at time scales much larger than a single time slice duration. In the framework, only large-scale channel state information (CSI) is utilized for saving cost. A worst-case model is introduced to depict interference caused by satellite link clusters, and an NP-hard mixed integer programming (MIP) problem is formulated. Based on analysis on the characteristics of the optimal solution, a novel link clustering algorithm is proposed to form a group of shaped virtual cells within the coverage area of the MCN. A suboptimal spectrum sharing scheme with only a small performance gap to the optimal one is then proposed. Simulations show that a significant improvement in both energy efficiency and spectrum efficiency can be achieved by the proposed framework.

This paper investigates an emergency rescue system, which comprises a multi-functional unmanned aerial vehicle (UAV) and multiple robots. The UAV carries sensing, communication, and computing modules. It senses system states, calculates commands, and instructs field robots to take actions. In this way, the UAV and robots form multiple sensing-communication-computing-control $(\mathbf{SC} ^{3})$ loops, which could finish many mission-critical tasks without human participation. To activate these $\mathbf{SC} ^{3}$ loops, we propose a closed-loop optimization scheme. Unlike traditional studies that primarily focus on the communication link, the proposed scheme emphasizes the $\mathbf{SC} ^{3}$ loop and adopts the linear quadratic regulator (LQR) cost as the objective. Focusing on the UAV-robot downlink, we model the data transmission in the finite block length regime and take the transmit power and block lengths as optimization variables. We solve the nonlinear integer problem by exploiting the monotonicity and convexity of the objective rate-cost function. The closed-form solution of the transmit power is derived in the assure-to-be-stable region. On this basis, we compare the proposed scheme with the max-sum rate scheme. Through comparisons, the fairness-minded nature of the proposed scheme is revealed.

In this paper, aiming at the problem of the boost isolated push-pull bidirectional DC/DC converter that the average value of the transmitted inductor current is zero in one switching cycle and cannot be directly described by the state space model, a modal average hierarchical modelling method is proposed, and a low-order uncoupled small signal mathematical model of the system is further established to realize the decoupling of the front and rear circuits. Then based on the pre-stage model of the converter, a dual closed-loop control system is established to control the clamp capacitor voltage. Next, based on the post-stage model, a post-stage single-voltage loop phase-shifting control system is shown to control the output voltage. Finally, based on simulation analysis, the parameters of the regulator are optimized to improve the dynamic and static performance of the system.

In this paper, taking the typical buck type in paralleled DC/DC converter as an example, a mathematical model of the parallel buck converter is established in the continuous domain, and a sliding mode control (SMC) system based on the master-slave control is designed for improving the output performance of the paralleled system. In order to adapt to practical engineering applications, the SMC system is further discretized by the zero-order holder (ZOH) to obtain the corresponding discrete control system, and the constraint conditions of the sampling period of the discretized SMC system for the paralleled buck converter is derived by analyzing the sufficient stable conditions of the discrete SMC system. Finally, the influence of discrete controller parameters and the superior performance of the designed controller on the SMC system is further discussed and verified by simulations.

Current fifth-generation (5G) networks do not cover maritime areas, causing difficulties in developing maritime Internet of Things (IoT). To tackle this problem, we establish a nearshore network by collaboratively using on-shore terrestrial base stations (TBSs) and tethered unmanned aerial vehicles (UAVs). These TBSs and UAVs form virtual clusters in a user-centric manner. Within each virtual cluster, non-orthogonal multiple access (NOMA) is adopted for agilely including various maritime IoT devices, which are sparsely distributed over the vast ocean. The nearshore network also shares the spectrum with marine satellites. In such a NOMA-based hybrid satellite-UAV-terrestrial network, interference among different network segments, different clusters, and different users occurs. We thereby formulate a joint power allocation problem to maximize the sum rate of the network. Different from existing studies, we use large-scale channel state information (CSI) only for optimization to reduce system overhead. The large-scale CSI is obtained by using the position information of maritime IoT devices. The problem is non-convex with intractable non-linear constraints. We tackle these difficulties by adopting max-min optimization, the auxiliary function method, and the successive convex approximation technique. An iterative power allocation algorithm is accordingly proposed, which is shown to be effective for coverage enhancement by simulations. This shows the potential of NOMA-based hybrid satellite-UAV-terrestrial networks for maritime on-demand coverage.

Benefiting from the fusion of communication and intelligent technologies, network-enabled robots have become important to support future machine-assisted and unmanned applications. To provide high-quality services for robots in wide areas, hybrid satellite-terrestrial networks are a key technology. Through hybrid networks, computation-intensive and latency-sensitive tasks can be offloaded to mobile edge computing (MEC) servers. However, due to the mobility of mobile robots and unreliable wireless network environments, excessive local computations and frequent service migrations may significantly increase the service delay. To address this issue, this paper aims to minimize the average task completion time for MEC-based offloading initiated by satellite-terrestrial-network-enabled robots. Different from conventional mobility-aware schemes, the proposed scheme makes the offloading decision by jointly considering the mobility control of robots. A joint optimization problem of task offloading and velocity control is formulated. Using Lyapunov optimization, the original optimization is decomposed into a velocity control subproblem and a task offloading subproblem. Then, based on the Markov decision process (MDP), a dual-agent reinforcement learning (RL) algorithm is proposed. The convergence and complexity of the improved RL algorithm are theoretically analyzed, and the simulation results show that the proposed scheme can effectively reduce the offloading delay.

In this paper, the stability problem of sliding mode (SM) controlled buck converters affected by the switching nonlinearity is investigated. In order to deduce the transfer function, the small signal model of buck converters is established in continuous conduction mode. Instead of the traditional time-domain approach based on Lyapunov theorem, the description function (DF) is introduced to realize the linearization of the switching nonlinearity under the direct ON/OFF control of SM controller. By Nyquist stability criterion, the system stability is proved to be determined by the implementation of hysteresis modulation. Comparative simulations with/without hysteresis modulation validate this paper.

In this paper, the frequency analysis of second-order sliding mode (SM) controlled buck converters is investigated by utilizing the description function (DF) approach. The transfer function of the buck converter is established on the basis of the small signal model. Taking the commonly-used super-twisting algorithm as an example, a second-order SM controller is designed, which consists of two nonlinear components. Then by adopting the DF approach, the linearized counterparts of the both can be further deduced, following the block diagram of the whole closed-loop control system. Based on the Nyquist stability criterion, the system stability is studied, which proves the inevitable existence of periodic oscillations caused by the nonlinearity of the controller. Meanwhile, the influence of the controller parameters with the frequency characteristics is investigated. Simulations validate this paper.

In the coming smart ocean era, reliable and efficient communications are crucial for promoting a variety of maritime activities. While on-shore base stations (BSs) constitute a key infrastructure for maritime communications, the trap of low energy efficiency caused by long transmission distances must be delicately circumvented. In this paper, we try to utilize internet of vessels (IoV) to tackle the problem. Specifically, we investigate the joint link scheduling and rate adaptation problem for a maritime communication network with both shore-to-vessel and vessel-to-vessel links, with the target of minimizing the energy consumption while assuring a quality of service (QoS) guarantee for each vessel. With only large-scale channel state information available, the problem is shown to be an NP-hard mixed integer non-linear programming problem with a group of hidden nonlinear equality constraints. A process-oriented iterative scheme is proposed based on a relaxation and gradually-approaching method following the gentlest-ascent principle, as well as the divide-and-conquer strategy. Simulation results demonstrate that the proposed scheme can achieve a prominent gain in terms of network energy consumption reduction with a rather low complexity.

In this paper, a novel robust control approach is proposed for the speed control of permanent magnet synchronous motor (PMSM) working in a network transmission environment. Based on the decoupled model of PMSM by using the vector control technology, the traditional point-to-point sliding mode (SM) control scheme with a double closed-loop structure is first given for comparison. The influence of network delay on the system is the concerned issue in this paper. For the time-varying network delay, the queuing theory is introduced to make it a fixed value. By combining multiple-step predictive control and SM control, a novel controller is designed, following its guaranteed stability condition based on Lyapunov theory. The simulations validate the proposed approach.

In this paper, an adaptive continuous sliding mode (SM) control approach is proposed for buck converters by introducing a novel zero-crossing checking mechanism into the twisting algorithm. Instead of the traditional first-order SM approaches, the twisting algorithm can solve their inherent chattering problem and realize the control continuity at the price of unnecessary constant control gain and low precision. Differing from the traditional adaptive mechanisms based on fuzzy logic or Lyapunov stability, the convergence characteristics of the controlled buck converter system are analyzed and further an adaptive twisting algorithm is proposed based on zero-crossing checking online to achieve a time-varying control gain. The number of the zero-crossing checking points can be calculated and the system stability is investigated. Comparative simulations with the traditional twisting algorithm validate the improved algorithm with advantages of high accuracy and excellent performance.

In the coming smart ocean era, reliable and efficient communications are crucial for promoting a variety of maritime activities. Current maritime communication networks (MCNs) mainly rely on marine satellites and on-shore base stations (BSs). The former generally provides limited transmission rate, while the latter lacks wide-area coverage capability. Due to these facts, the state-of-the-art MCN falls far behind terrestrial fifth-generation (5G) networks. To fill up the gap in the coming sixth-generation (6G) era, we explore the benefit of deployable BSs for maritime coverage enhancement. Both unmanned aerial vehicles (UAVs) and mobile vessels are used to configure deployable BSs. This leads to a hierarchical satellite-UAV-terrestrial network on the ocean. We address the joint link scheduling and rate adaptation problem for this hybrid network, to minimize the total energy consumption with quality of service (QoS) guarantees. Different from previous studies, we use only the large-scale channel state information (CSI), which is location-dependent and thus can be predicted through the position information of each UAV/vessel based on its specific trajectory/shipping lane. The problem is shown to be an NP-hard mixed integer nonlinear programming problem with a group of hidden non-linear equality constraints. We solve it suboptimally by using Min-Max transformation and iterative problem relaxation, leading to a process-oriented joint link scheduling and rate adaptation scheme. As observed by simulations, the scheme can provide agile on-demand coverage for all users with much reduced system overhead and a polynomial computation complexity. Moreover, it can achieve a prominent performance close to the optimal solution.

In this paper, a novel continuous non-singular terminal sliding mode (NTSM) control approach with hierarchical two-layer sliding surfaces are proposed for electronic throttle (ET) of gasoline engines. In modelling, the uncertain parameters and external disturbances of the ET system are considered. By combining the concepts of relative degree and high-order sliding mode (HOSM), a novel continuous NTSM controller is designed for the ET system, which features of free-chattering, fast response and high accuracy. Especially the hierarchical control structure is adopted for the design of sliding surface by utilizing linear sliding mode (LSM) and NTSM simultaneously. A robust derivative estimator is used to estimate the derivative of LSM variable in the controller. Comparative simulations with the traditional twisting algorithm are presented to validate this paper.

This paper investigates the influence of unmodeled dynamics of joint actuators on sliding mode controlled two-link flexible manipulators. The joint actuators are modeled as singularly perturbed systems and a linear combination of joint angular and flexible modes is chosen as a new output, which can decompose the whole system into an input-output subsystem and a zero dynamic subsystem for the indirect control of tip-position. For the input-output subsystem, the influence of joint actuator dynamics on the system stability is investigated; while for the zero dynamic subsystem, its stability is proved to be related to the redefined parameters. Finally the Lyapunov stability theory is used to determine the steady error of tip-position for each link. Simulations validate this paper.

In this paper, an novel unified sliding mode (SM) control scheme is proposed for boost converters, which can be adopted for the controller design based on the quantitative dynamic and static performance indexes simultaneously. Due to the ON/OFF operations of power switch, the boost converter is modeled into a switching affine system. The steady-state error is the concerned static performance indexes, while overshoot and setting time are considered at the same time for the dynamics control. In order to satisfy the different control objectives at different phases of system movement, a SM control scheme with two hierarchical sub-controllers is proposed. If the steady-state error is chosen to construct a quadratic performance index function, a linear SM sub-controller is only needed; while if the dynamic performance indexes are needed for consideration, another extra Backstepping SM sub-controller will be added. Simulations verify the correctness of this paper.

The decoupling control of two-link flexible manipulators with uncertain parameters and joint motor dynamics is investigated by combining terminal sliding mode (TSM) and output redefinition in this paper. The linear combination of joint angles and flexible modes is chosen as the redefined output to overcome the inherent non-minimum phase characteristics of flexible manipulators; correspondingly the system is decomposed into an input-output subsystem with motor dynamics and an internal dynamic subsystem with uncertain disturbances. A TSM controller is designed for the robust stability of input-output subsystem as well as to transfer the internal dynamics into zero dynamics. The stability of zero dynamic subsystem is proved to be related to the redefined parameters. Finally the steady-state error of the tip position for each link is deduced by Lyapunov stability theory. Simulation results validate the proposed scheme.

This paper investigates the problems of stability and periodicity for the discrete sliding mode (SM) controlled DC-DC buck converters subject to parasitic parameters. The loss resistance of power switch, conduction voltage and conduction resistance of diode, equivalent series resistance of inductor are first considered and modeled for buck converters. After the discretization of SM controlled buck converter system, the stability condition is deduced, proving that there exist a attractive region in phase plane which affected by the sampling time. The sufficient and necessary condition of periodicity is given and the influence of parasitic parameters on dynamic trajectory is analyzed and further it is proved not affect the system periodicity under some restricted conditions. Simulations validate the proposed research.

The inevitable existence of harmonics in sliding mode (SM) controlled DC-DC boost converters with sensor unmodeled dynamics is investigated in this paper. A singular perturbation model of unmodeled dynamics is proposed by choosing the rise time of sensor as a perturbed parameter. The guaranteed stability conditions of SM controller and sensor output are deduced respectively, following an equivalent model transformation of the whole closed-loop system for convenient analysis. A Lyapunov-like function is further designed to prove the harmonics exist in a vicinity concerning the rise time of sensor. Simulation results validate the proposed scheme.

For a non-singular terminal sliding mode (NTSM) controlled two-link flexible manipulator, this paper investigates the phase trajectories starting from different original states and gives the existence of a critical surface determining whether the system convergences to the equilibrium point in a short path. By using the output redefinition method, the system is first decomposed into a zero dynamic subsystem and an input-output subsystem-the stability of the former is guaranteed by pole placement technique, while a NTSM controller is designed for the latter to realize its finite time convergence and better control performance. Then twelve possible original states and their corresponding phase trajectories are discussed, proving the distribution rule of phase trajectory. Simulations validates the proposed analysis.

This paper focuses on the transient analysis for a two-link flexible manipulator under the control of non-singular terminal sliding mode (NTSM), and proposes a convergence time estimation method with difficulties of non-minimum phase and the uncontrolled reaching motion. To overcome the first problem, the system is decomposed into a zero dynamic subsystem and an input-output subsystem-the stability of the former is guaranteed by pole placement, while a NTSM controller is designed for the latter to realize its finite time convergence and better control performance. The relationship between the initial point and the sliding mode reaching time is explored, and further the convergence time is estimated to overcome the second problem. Simulations validate the proposed method.

Millimeter-wave (mmWave) communication is envisioned to provide orders of magnitude capacity improvement. However, it is challenging to realize a sufficient link margin due to high path loss and blockages. To address this difficulty, in this paper, we explore the potential gain of ultra-densification for enhancing mmWave communications from a network-level perspective. By deploying the mmWave base stations (BSs) in an extremely dense and amorphous fashion, the access distance is reduced and the choice of serving BSs is enriched for each user, which are intuitively effective for mitigating the propagation loss and blockages. Nevertheless, co-channel interference under this model will become a performance-limiting factor. To solve this problem, we propose a large-scale channel state information (CSI)-based interference coordination approach. Note that the large-scale CSI is highly location-dependent, and can be obtained with a quite low cost. Thus, the scalability of the proposed coordination framework can be guaranteed. Particularly, using only the large-scale CSI of interference links, a coordinated frequency resource block allocation problem is formulated for maximizing the minimum achievable rate of the users, which is uncovered to be an NP-hard integer programming problem. To circumvent this difficulty, a greedy scheme with polynomial-time complexity is proposed by adopting the bisection method and linear integer programming tools. Simulation results demonstrate that the proposed coordination scheme based on large-scale CSI only can still offer substantial gains over the existing methods. Moreover, although the proposed scheme is only guaranteed to converge to a local optimum, it performs well in terms of both user fairness and system efficiency.

In this paper, preamplifier circuit, filter circuit and bias circuit with protection were designed. With the help of DSP and LabVIEW, the algorithm implementation of dual-phase lock-in amplifier, data processing, data display and the serial communication between DSP and LabVIEW were achieved. A complete digital dual-phase lock-in amplifier system based on DSP and LabVIEW was designed. It can extract the weak sinusoidal signals submerged by noise. This design has the advantages of high accuracy, low cost and portability, and its update and transplantation are easy. Experiment results show that when the rate of weak sinusoidal signal's additional noise is 100%, the relative error of amplitude detection is less than 2%, and the absolute error of phase measurement is less than 3°. It fully satisfies the requirements of detecting weak signals submerged by noise in general application. It can also serve as a high cost performance platform in the intensive study of weak signal detection.

In this paper, a terminal sliding mode (TSM) controller is designed for boost converter with purpose of robustness and better response against circuit nonlinearities and disturbances. Instead of using the commonly used average model or switching model for current-mode controlled (CMC) boost converter, a novel energy storage function (ESF) model is proposed for TSM controller, which contains all of the nonlinear elements of inductor current and capacitor voltage and further converges the both to the zero, unlike the CMC control ignoring the transient control of capacitor voltage. By adopting TSM instead of the traditional linear sliding mode (LSM), the system can track the given output voltage with faster response due to its finite time convergence. Meanwhile, an exponential reaching law is designed for TSM controller to eliminate the unexpected chattering phenomenon. Simulation results with comparison of the traditional CMC LSM control can prove the better control performance of the proposed scheme.

This work focuses on stability analysis and stabilization synthesis problem for a class of Takagi-Sugeno (T-S) polynominal fuzzy-model-based time-delay systems based on the sum-of-squares (SOS) approach. Firstly, a novel stability criterion is proposed based on Lyapunov stability theorey, which is less conservative as the information of the membership functions is included in the stability conditions. Then, a new fuzzy controller with greater design flexibility to stabilize the colsed-loop system is developed. Finally, a simulation example is provided to illustrate the effectiveness of the proposed design methods.

The massively dense distributed antenna system (md-DAS) with virtual cells (VCs) has drawn increasing interests recently. In this paper, we develop an energy-efficiency-oriented coordinated power allocation (PA) scheme considering the inter-VC interference in a downlink md-DAS. The problem can be formulated as a complicated non-convex fractional programming problem. To make it tractable, we recast the problem into quasi-concave fractional programming sub-problems, by applying successive Taylor expansion. Then we transform these subproblems into the equivalent convex ones in a subtractive-form based on fractional programming method. An iterative energy-efficient coordinated PA algorithm is finally proposed. Simulation results illustrate that the proposed scheme can offer a significant performance improvement over the existing methods.

This paper presents a novel terminal sliding mode (TSM) control scheme with double closed-loop structure of capacitor voltage and inductance current for the stability control of DC-DC buck converter. In order to satisfy the different performance demands of capacitor voltage and inductance current, a TSM controller and a linear sliding mode (LSM) controller is designed separately. For the former, TSM controller can track the given output voltage with fast response speed due to its finite time convergence and then output the reference inductance current; while for the latter, it can track the reference inductance current and then control the `on/off' of the power switch. The stability condition in the case of power switch `on' and `off' can also be deduced. Simulation results with comparison of those of traditional single-loop LSM controller can validate the proposed scheme.

In the implementation of distributed antenna systems (DASs), the antenna elements in some cases may only be deployed in the form of distributed antenna-clusters (ACs), due to various practical limitations. Consequently, correlation usually exists among the antenna elements within each AC. In contrast to most of the previous work that focused on the antenna correlation in a single-cell environment, this paper investigates the impact of the antenna correlation in a more general multi-cell scenario, where the inter-cell interference becomes the key challenge. We formulate a joint multi-cell input covariance optimization problem, accounting for the transmit antenna correlation, the propagation path-loss and the shadow fading. We show that the problem is a complicated non-convex problem. Moreover, the objective function, i.e., the ergodic sum capacity, is found difficult to be expressed in a straightforward form. After mathematical simplification, we propose an iterative inter-cell coordination scheme by adopting the successive approximation method. Simulation results demonstrate that, thanks to much more effective adaptation to the antenna correlation, the proposed scheme outperforms the existing ones and can significantly improve the system performance of a DAS with highly-correlated ACs.

The standard application of nonsingular terminal sliding mode (NTSM) control is strictly limited to n-order (n≥2) systems and suffers from chattering problem. This paper proposes a continuous NTSM control for extended first order systems to obtain the global finite-time convergence and free-chattering simultaneously. Firstly, utilizing the concept of relative degree, a power-fractional NTSM manifold is designed. Then, based on Lyapunov stability theorem, a switching control law is designed to act on the derivative of NTSM variable, so that the real control is smoothed by integral action. Meanwhile, since the integral term is incompatible with input saturation in real systems, anti-windup compensation should be made accordingly. Taking permanent magnet synchronous motor as an example, simulation results are presented to validate the proposed method.

This paper investigates the robust control of two-link flexible manipulator systems subject to parameter perturbations, and a hybrid control scheme consisting of a continuous nonsingular terminal sliding mode (NTSM) controller and an observer-based LQR controller is proposed. In order to solve the non-minimum phase problem of flexible manipulator, singular perturbation method is utilized to decompose the system into a slow and fast subsystem in two-time scale, and joint angles and corrected flexible modes are modeled as the slow and fast variables, respectively. For the slow subsystem, a novel continuous NTSM control based on the concept of relative degree is proposed for robustness, finite-time convergence and free-chattering. For the fast subsystem, a reduced-order observer is designed to estimate corrected flexible modes and then a LQR controller is proposed for its optimal stability. Simulation results are presented to validate the control scheme.

The virtual multiple input multiple output (MIMO) technique can dramatically improve the performance of a multi-cell distributed antenna system (DAS), thanks to its great potentials for inter-cell interference mitigation. One of the most challenging issues for virtual MIMO is the acquisition of channel state information at the transmitter (CSIT), which usually leads to an overwhelming amount of system overhead. In this work, we focus on the case that only the slowly-varying large-scale channel state is required at the transmitter, and explore the performance gain that can be achieved by coordinated transmissions for virtual MIMO with large-scale CSIT. Aiming at maximizing the achievable ergodic sum rate, the input covariances for all the mobile terminals (MTs) are jointly optimized, which turns out to be a complicated non-convex problem with a non-closed-form objective function. Further analysis reveals that the coordinated transmission problem can be recast as a Max-Min problem with a closed-form objective function and linear constraints. Then, by appealing to the successive approximation method and the saddle-point theory of concave-convex functions, we propose an iterative algorithm for coordinated transmissions with large-scale CSIT and establish its convergence. Simulation results corroborate that the proposed scheme converges quickly, and it yields significant performance gains compared to the existing schemes. Moreover, it is observed that the proposed scheme can achieve a nearly globally-optimal point under the diagonal input covariance constraint. Since the acquisition of large-scale CSIT is far less demanding than that of full CSIT, we believe that the proposed coordinated transmissions with large-scale CSIT in DASs shed some light on virtual MIMO in the making.

In this paper, the problem of joint power allocation (PA) for the downlink of a multi-cell distributed antenna system (DAS) is addressed. Motivated by practical applications, we focus on a reasonable scenario that only the large-scale channel state information at the transmitter (CSIT) is available. Based on the observation that the capacity-achieving input covariance for each cell is diagonal and that PA optimization is enough to achieve the maximum ergodic sum capacity, we formulate a joint PA optimization problem to maximize the ergodic sum capacity of the system with a total transmit power constraint for each cell. A rather precise closed-form approximation of the ergodic sum capacity is then introduced and taken as the objective function instead so that the original joint PA optimization problem can be simplified. Finally, we propose an iterative PA scheme based on the simplified joint PA optimization problem, in which Signomial Programming (SP) is used. Monte Carlo simulations show that the proposed scheme converges quickly and can offer nearly optimal system ergodic sum capacity. Thus, we refer the proposed PA scheme as a suboptimal one. Moreover, from the simulations we can see that a significant performance gain can be achieved by multi-cell joint PA in DAS with only large-scale CSIT.

In this paper, we address the problem of coordinated user scheduling for the downlink of a multi-cell distributed antenna system (DAS). With the practical assumption that only large-scale channel state information (CSI) is known at the transmitter, a low-complexity greedy scheduling scheme is proposed. In order to provide fairness among users, the proposed scheme adopts round-robin scheduling within each cell and optimizes the scheduling order for each cell to maximize the minimum ergodic capacity of the users. For each user, the selection transmission scheme (just the distributed antenna element (DAE) with the largest channel gain to the user is selected for transmission) is implemented and each selected DAE transmits with equal power. Simulation results demonstrate that the proposed greedy scheme promises much better performance than that without inter-cell coordination and its performance is quite close to the optimal one. Moreover, by simulations we find that the proposed scheme achieves nearly the same system ergodic sum capacity with the one targeted to maximize the system ergodic sum capacity.

In this note, we point out a few problems with the proof for Theorem 1 and Theorem 2 in the above-mentioned paper and give a correct version for the incorrect parts.