Switching Delay Research Articles

Finite-time formation trajectory tracking control for unmanned underwater vehicles with time delays and Markov-switch topology

ABSTRACT The formation trajectory tracking control strategy of unmanned underwater vehicles is proposed for communication time delay and communication topology random switching. The methods ensure that formation systems are finite-time bounded under discrete time. Firstly, based on the consistency theory and the exact feedback linearised dynamics model of unmanned underwater vehicle, a control strategy is proposed for discrete formation system with communication time delay. Secondly, a cooperative control method is designed for communication problems of Markovian switching topology and time delay. Then, definition of finite-time bounded and linear matrix inequality technique are applied to sufficient conditions of system stability for the above problem. Finally, the formation motion of discrete unmanned underwater vehicle system in three-dimensional space is simulated, fully demonstrating the feasibility of the method.

Stabilization of nonhomogenous semi-Markov jump linear systems with synchronous switching delays via aperiodically intermittent control

A type of nonhomogenous semi-Markov jump linear systems with synchronous switching delays is considered in the present paper. Owing to the existence of time-varying delays and nonhomogenous semi-Markov switching process, the selection of Lyapunov functional and the transformation of some time-varying parameters become more complicated in comparison with many existing works. To overcome these difficulties, a sort of Lyapunov–Krasovskii functional related to switching delays is introduced. Simultaneously, the technique of convex combination is applied to tackle a variety of time-varying terms including transition probabilities (TPs), probability distribution function and probability density function (PDF). Then, a time-invariant stability criterion superior to many relevant works in conservativeness is obtained to ensure mean-square exponential stability (MES). Based on this result, time-invariant conditions for mean square exponential stability of the controlled system are also attained by the continuous feedback control. Subsequently, to stand on the point of cost reduction, an aperiodically intermittent control (AIC) is adopted in such a system and a stability criterion is attained as well under more relaxed restrictions on relative parameters. Finally, a numerical example is provided to verify the effectiveness and correctness of the results.

Node-to-node clustering asymptotic synchronized discrete stochastic neural networks in time and space with Bernoulli switching delay

The article proposes a new approach to synchronizing space–time discrete stochastic neural networks with random switching delays. This is achieved by employing a control in the boundary, which is based on node-to-node clustering and controlling theories. The design of the control in the boundary for synchronizing space–time discrete stochastic neural networks in the form of clusters is based on the establishment of several significant sequential inequalities and the creation of cluster information. Also, an executable computer algorithm has been developed to streamline the implementation of the findings presented in this paper. The current study represents a pioneering approach in considering spatial discrete factors, providing a solid foundation for future research and offering theoretical and practical guidance.

Event-Triggered Extended Dissipative FTB for T-S Fuzzy Switched Systems With Mismatched Phenomena and Deception Attacks: A Multidomain Framework.

This article investigates the extended dissipative finite-time boundedness (ED-FTB) problem for fuzzy switched systems under deception attacks. To improve the network resource efficiency, a multidomain probabilistic event-triggered mechanism (MDPETM) is proposed. The mode mismatched phenomenon is modeled based on the switching delay information between the controller mode and the system mode. To extract the true signal generated by the MDPETM, a virtual delay concept is developed. The constraint that the controller and the system must have the same premise variables is removed. Based on the MDPETM, mismatched fuzzy state feedback controllers are first devised which may not share the same modes with the system. Then, by establishing fuzzy basis and controller mode-dependent Lyapunov functionals, sufficient criteria free of nonlinear terms existing in the literature are derived, which ensure the ED-FTB of the closed-loop system under admissible delays and deception attacks. Finally, an application-oriented one-link robotic arm system is utilized to validate the theoretical results.

An Improved SPWM Strategy for Effectively Reducing Total Harmonic Distortion

In the inverter circuit, the speed at which the MOSFET is impacted by the presence of a parasitic inductor within the printed circuit board (PCB) leads to a delay in the switching process. Furthermore, the parasitic inductor within the circuit can easily form an LC oscillation with the parasitic capacitor of the MOSFET. These two issues result in an inconsistency between the actual output of the MOSFET and the driving signal waveform, leading to distortion in the sinusoidal pulse width modulation (SPWM) waveform and an increase in total harmonic distortion (THD). It is a common practice to mitigate gate oscillation by introducing a resistor at the gate of the MOSFET. However, elevating the resistance leads to deceleration in the charging process of the MOSFET’s parasitic capacitor, consequently causing an increase in the switching delay, and thereby increasing THD. Therefore, an effective strategy to reduce THD is proposed in this paper, while augmenting the gate resistance, computing the MOSFET switching delay, and applying corrective compensation. In this way, the inherent issues of the switch are addressed, resulting in inverter output waveforms that closely resemble sine waves and reduced THD. Through a combination of simulation and empirical experimentation, the efficacy of the proposed approach in significantly reducing THD in the inverter’s output waveform has been empirically substantiated.

Dead-Time Free Modulation Scheme for IM Drive System Fed by Voltage Source Inverter

During the modulation process of the VSI motor drive system, the nonlinear errors caused by the dead-time and conduction voltage drop will increase the phase current harmonic distortion and the torque ripple. To solve this problem, a novel dead-time free modulation scheme is proposed in this paper. In the non-zero crossing region of the phase current, the switching tube, whose body diode can provide a continuation path, is set as off-state, the driving signal is only implemented on another switching tube with the same bridge arm, and the errors caused by the conduction voltage drop and switching delay are compensated to the pulse duration. At the same time, to suppress the zero current clamp effect that exists near the zero crossing point of the phase current, another modulation scheme for the phase current crossing zero in advance is proposed, which avoids the complicated determination and calculation of the current polarity near the zero crossing point of the current. Both of the above modulation schemes eliminate the dead-time, and the switching principle is presented. In addition, to suppress the impact of the current ripple and high-frequency noise on the accuracy of the phase current detection, a second-order resonance digital filter without phase shift is introduced. Finally, compared to two deadtime compensation methods, the effectiveness and superiority of the proposed dead-time free modulation scheme are verified by the experimental results.

Secure consensus for positive multi‐agent systems with bumpless transfer control under Denial‐of‐Service attacks

AbstractThis article investigates the secure consensus control problem of positive multi‐agent systems under multiple‐mode Denial‐of‐Service (DoS) attacks. A bumpless transfer (BT) control based secure mode strategy is proposed to improve the switching transient performance due to the system being actively switched to secure mode when attack is detected. Considering possible time delays for agents dealing with the issues of DoS attacks, an asynchronous switching model is established between system models and communication topology. With the stability theory of positive systems, sufficient and necessary conditions are established to guarantee the positivity of multi‐agent systems under the secure mode strategy. Because the switching law caused by external attacks is unknown in advance, the BT control is specifically implemented through the controller gain interpolation technique. By multiple Lyapunov functions (MLFs) approach, secure consensus is achieved with a trade‐off among controller performance, attack parameters, and switching delays. Numerical examples are presented to demonstrate the effectiveness of the obtained results.

Reduce energy consumption - causes of CMOS inverter switching delay and its influencing factors

This paper offers a comprehensive examination of the Complementary Metal-Oxide-Semiconductor (CMOS) inverter, a quintessential component in contemporary digital integrated circuits, renowned for its minimal power consumption, robust noise resistance, and adaptability. The focus of this investigation is the switching delay of the CMOS inverter, a pivotal attribute that exerts substantial influence on the overall functionality of the circuitry. This discourse undertakes a detailed exploration of the factors contributing to the CMOS inverter switching delay, dissecting the influence of both intrinsic and extrinsic elements. Initially, the analysis delineates the origins of the switching delay in CMOS inverters, categorizing them into internal and external determinants. Subsequently, the study meticulously examines methodologies to modulate these factors, thereby achieving effective control over the delay. By implementing strategic optimizations, this research aims to diminish latency and enhance operational efficiency. Through a theoretical lens, this paper elucidates the complex interplay between these inherent and external factors, culminating in the optimization of the CMOS inverter switching delay. The insights garnered from this analysis are poised to offer a substantive theoretical foundation for the design of more efficient and reliable digital circuits in the current technological milieu.

H∞ control of delayed switched systems under asynchronous switching: New results without the constraint between the switching delay and the dwell time of submodes

AbstractThis article investigates the control problem of switched systems with time‐varying delays under asynchronous switching. By reconstructing the switching rule of local controllers and empolying multiple Lyapunov functionals and integral inequalities, sufficient conditions without the constraint between the switching delay and the dwell time of submodes to solve the control problem are derived. The control gain matrices can be conveniently obtained by the proposed linear search algorithm.

Improved Design of a SiC MOSFET Gate Drive with Crosstalk Suppression Capability

For high-frequency switching applications, silicon carbide (SiC) devices are more suitable than silicon-based devices, which is conducive to improving the efficiency and power density of power electronic equipment. However, as the switching frequency increases, the influence of parasitic parameters on the switching characteristics of devices becomes increasingly apparent. When SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) are applied in bridge circuits, the crosstalk problem easily occurs with the complementary conduction of upper and lower transistors, which seriously limits the promotion of SiC MOSFETs. However, the existing crosstalk suppression drive circuit tends to increase the switching loss, switching delay, and control complexity; therefore, a gate drive with crosstalk suppression capability is proposed. In this paper, the gate drive has two features: a negative voltage to shut down the SiC MOSFET; and an adjustment of the gate-source equivalent impedance. To accomplish this goal, the mechanism of crosstalk voltage generation is analyzed. Furthermore, the operation principle of the gate drive is analyzed, and the parameters of the gate drive are designed. Eventually, the proposed gate drive is verified by an LTspice simulation and experimental platform. The results prove that the gate drive can suppress the crosstalk voltage without affecting the switching speed.

Event‐triggered output quantization control for asynchronously switched interval type‐2 fuzzy systems

AbstractThis article considers exponential stabilization (ES) of switched interval type‐2 (SIT2) fuzzy systems with asynchronous switching control. The SIT2 fuzzy system switches from one mode to another according to transition probabilities (TPs). A general SIT2 fuzzy quantized event‐triggered output controller (QETOC) is designed to save the communication resources. The QETOC employs distinctive membership functions from those of the IT2 fuzzy model and switches with mode‐pendent switching delay, which is more practical than asynchronously switched control techniques with a common switching delay and control schemes without TP. By designing discretized multiple Lyapunov function (DMLF) and using convex combination technique, sufficient conditions formulated by linear matrix inequalities (LMIs) are obtained to ensure that the DMLF does not ‘jump high’ at the moment of switching, and hence the conservatism of obtained results is significantly reduced since no additional dwell time is needed for the stabilization. It is discovered that the SIT2 fuzzy system is not necessary to be unstable on mismatched intervals, and it can be unstable on matched intervals. The advantages of theoretical analysis are verified by numerical simulations, and the classical assumption that each subsystem is unstable on mismatched intervals is conservative for control design.

A fault ride-through strategy for grid-forming converters under symmetrical and asymmetrical grid faults

In order to maintain grid-forming converter (GFM) voltage source behaviour under current limiting mode, a threshold virtual impedance (TVI) current limiting control is proposed, which is controlled in the positive and negative sequence synchronous reference frames for symmetrical and asymmetrical fault conditions. The converter current is strictly limited within the maximum limit without the need for current saturation limiters. Since the TVI control is based on 3-phase sinusoidal currents, it is shown that using the measured current instead of the existing current reference for the TVI control may cause oscillatory behaviour when a large switching delay is considered. Since sequence extraction control is necessary, the paper also compares GFM dynamic stability under the three well-known sequence extraction methods (i.e. delay cancellation, dual second order generalized integrator, and decoupled double synchronous reference frame). It is shown that the differences are small when GFM is not in current limiting mode, but they are large when GFM is in current limiting mode or switching delays are considered.

Hybrid intelligent system for channel allocation and packet transmission in CR-IoT networks

The proliferation of interconnected devices is driving a surge in the demand for wireless spectrum. Meeting the need for wireless channel access for every device, while also ensuring consistent quality of service (QoS), poses significant challenges. This is particularly true for resource-limited heterogeneous devices within Internet of Things (IoT) networks. Cognitive radio (CR) technology addresses the shortcomings of traditional fixed channel allocation policies by enabling unlicensed users to opportunistically access unused spectrum belonging to licensed users. This facilitates timely and reliable transmission of mission-critical data packets. A cognitive radio-enabled IoT (CR-IoT) network is poised to better accommodate the growing demands of diverse applications and services within the smart city framework, spanning areas such as healthcare, agriculture, manufacturing, logistics, transportation, environment, public safety, and pharmaceuticals. To minimize switching delays and ensure energy and spectral efficiency, this study proposes a hybrid intelligent system for efficient channel allocation and packet transmission in CR-IoT networks. Leveraging Support Vector Machine (SVM) and Adaptive Neuro-Fuzzy Inference System (ANFIS), the system dynamically manages spectrum resources to minimize handoffs while upholding QoS. A Java-based simulation integrates system outputs with interference temperature data to accommodate service demands across 2G–4G spectrums. Evaluation reveals SVM’s 98.8% accuracy in detecting spectrum holes and ANFIS’s 90.4% accuracy in channel allocation. These results demonstrate significant potential for enhancing spectrum utilization in various IoT applications.

Inverter With Paralleled Modules to Extend Current Capacity and Combat Motor Overvoltage in SiC-Based Adjustable Speed Drives

This article proposes a quasi-three-level (Q3L) PWM-based module-parallel inverter to address two major issues of deploying SiC MOSFETs in high-power cable-fed adjustable speed drives. Firstly, the maximum output power of SiC inverters is limited due to the lack of high current rating SiC devices, which cannot satisfy the demand of high-power applications such as heavy-duty electric vehicles and more electric aeroplanes. The second issue comes from the fast-switching speed of SiC MOSFETs, where power cables act like transmission lines under steep rising/falling voltages (high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$dv/dt$</tex-math></inline-formula> ), with back and forth voltage reflections that result in serious overvoltage oscillations at motor terminals. To address these issues, a SiC module-parallel inverter is adopted with elevated current capacity, where the phase voltage is maintained at the mid-point of a coupled inductor connected to the output nodes of each paralleled half-bridge module. By actively controlling the switching delay between the paralleled half-bridge-legs, Q3L PWM waveforms are generated at the inverter output nodes which can mitigate the motor overvoltage due to the voltage reflections through power cables. An active current control technique is also proposed to facilitate the current balance between the paralleled half-bridge-legs. The proposed Q3L PWM-based module-parallel inverter is experimentally verified using a SiC-based cable-fed motor drive system. The results show that the proposed approach can extend the current capabilities of SiC devices as well as mitigate the motor overvoltage, enabling the adoption of SiC devices in high-power motor drives.

Study on a rotational symmetry structure pulse forming network with low-impedance for compact pulse drivers.

A pulse forming network (PFN) is a significant component, contributing a lot to the overall dimension of pulse generators. In order to both reduce the size of PFN and improve the output waveform quality, this paper proposes a compact low-impedance PFN with a rotational symmetry structure. The PFN consists of four groups of Blumlein pulse forming units (PFUs) connected in parallel along the angular direction, and the spline curve structure is applied in each PFU, which achieves a higher space utilization rate. The theoretical maximum energy density of PFN is 6.6 J/L as the dimensions of PFN are φ500 × 138mm. Field-circuit co-simulation is carried out based on the spatial model of PFN and the double switch modulation circuit to analyze the effects of switch delay time (time between main switch and steep discharge switch), as well as the output port position affecting the output pulse waveform. The results show that the PFN is appropriate to achieve quasi-square wave pulse modulation as the switch delay time is 290ns with the output port positioned at the periphery. The verification experiments are also carried out. The results show that the PFN can generate a quasi-square wave pulse with an output voltage of 49.6kV, a pulse width of 83ns, and a peak power of 1 GW on a matched load. The output pulse exhibits a distinct flat top, with the fluctuation of the plateau being less than 3%.

Non-Invasive Calibration Method for Optical Switching Delay Line Based on Iterative Optimization

Non-Invasive Calibration Method for Optical Switching Delay Line Based on Iterative Optimization

Voltage control of electromagnetic properties in antiferromagnetic materials

Dynamic modulation of electromagnetic responses is theoretically examined in dielectric antiferromagnets (AFMs). While both magneto-electric and magneto-elastic coupling can achieve robust electrical control of magnetic anisotropy, the latter is considered in a bilayer structure with a piezoelectric material. Numerical calculations based on the frequency-dependent permeability tensor clearly illustrate that the anisotropy profile in the typical dielectric AFMs such as NiO and Cr2O3 can be modified sufficiently to induce a shift in the resonance frequency by as much as tens of percent in the sub-mm wavelength range (thus, an electrically tunable bandwidth over 10’s of GHz). The polarization of the electromagnetic response is also affected due to the anisotropic nature of the effect, offering a possibility to encode the signal. The intrinsic delay in switching may be minimized to the ns level by using a sufficiently thin AFM. Application to specific devices such as a bandpass filter further illustrates the validity of the concept.

Input Voltage-Level Driven Split-Input Inverter Level Shifter for Nanoscale Applications

A level shifter (LS) appears to be highly efficient and effective in solving voltage contentions between deep sub-threshold and core voltage levels. An input voltage-level driven split-input inverter that can create common unconnected PMOS and NMOS transistors for the input inverter is proposed, which is powered and used at the input stage to achieve maximum conversion efficiency. Layout and simulation results across different corners have demonstrated that the proposed LS is highly useful for cutting-edge nanoscale applications. It can up-convert voltage from 0.2 V to 1.2 V and down-convert from 1.2 V to 0.2 V @ 1 MHz input pulse, with a level-up or level-down mean switching delay of 1.3 ns, and a power of 9.5 nW. Moreover, the LS occupies an area of 8 μm2, which is a reasonably compact size compared to the typical LS designs. Overall, the proposed voltage LS design is an efficient and effective solution that could have an ample range of applications in IoT and biomedical, wireless sensor networks.

A Voltage-Gated Spin-Orbit Torque (VgSOT) Magnetic Tunnel Junction based Non-Volatile Flip Flop design for Low Energy Applications

In this paper, a Voltage-gated Spin-Orbit Torque based non-volatile flip-flop design has been discussed. Theflip-flop consists of a conventional CMOS master latch used in normal operations, and a VgSOT-MTJ basedslave latch has been considered for interim data saving during power-gating. The current circuit uses the samewrite current to write data into two magnetic tunnel junctions, saving 50% of storing energy. The proposedNVFF circuit has been simulated using Cadence Virtuoso 45nm. The performance parameters like energyconsumption and delay during restore and store operations of VgSOT-MTJ based NVFF circuit have beenanalyzed in this paper and compared with SOT-MTJ based and STT-MTJ based NVFF circuits. Simulationresults show that for the switching delay, VgSOT-MTJ based NVFF performs 40% and 58% better than SOT-MTJ NVFF and STT-MTJ based NVFFs, respectively during storing mode and 83% and 88% better than SOT-MTJ and STT-MTJ based NVFFs during restoring mode. In terms of energy consumption, during storingmode, VgSOT-MTJ based NVFF consumes 84% less energy than SOT-MTJ NVFF and 90 % less energy thanSTT-MTJ based NVFFs. During restoring mode, VgSOT-MTJ based NVFF consumes 70% and 80% lessenergy than SOT-MTJ NVFF and STT-MTJ, respectively.

Stability for Markov switching stochastic delay systems binding event-triggered mechanism to activate multi-impulse jumps

This paper focuses on the pth moment exponentially stability for Markov switching and multi-impulse jumps stochastic time-varying delay system, where the switching behavior among subsystems of the target system is determined by Markov chains, and the occurrence of impulsive jumps is decided according to event-triggered impulsive mechanism when certain well-designed conditions are satisfied. By applying the Itô formula, Gronwall inequality and Razumikhin theorem, some novel sufficient criteria are provided to assure the system stability and get rid of Zeno phenomenon. It is worth pointing out that the multi-impulse jumps are our research aim and the range of delays considered is relatively wide, i.e., the daily bounded delay τ(t)∈[0,1) and the unupper bound delay τ(t)∈[1,∞). Subsequently, two diverse event trigger mechanism about impulsive jumps are proposed for such two types of delays, namely the defined event-triggered impulsive mechanism with delay. Finally, the validity and feasibility of the developed theoretical results are verified by two numerical simulations.