Switching Signals Research Articles

Fuzzy nonsingular fast terminal sliding mode controller for a robotic system

This study introduces an innovative control strategy utilizing a nonsingular fast sliding mode technique tailored for robotic systems. The core of this approach lies in the development of a type-2 fuzzy logic-based nominal model, meticulously designed to accurately approximate the dynamics of the real system while adeptly handling the variability in system parameters. This method marks a departure from conventional approaches by inferring the switch signal for type-2 adaptive fuzzy systems, a critical step in achieving superior tracking performance without the necessity for extensive knowledge of the system's upper bounds in uncertainties and external disturbances. The efficacy of the proposed control law is rigorously validated through a series of simulations, encompassing a variety of initial conditions and reference signals, thereby demonstrating its robust performance capabilities.

Safety-Critical Model Reference Adaptive Control of Switched Nonlinear Systems With Unsafe Subsystems: A State-Dependent Switching Approach.

In this article, a novel safety-critical model reference adaptive control approach is established to solve the safety control problem of switched uncertain nonlinear systems, where the safety of subsystems is unnecessary. The considered switched reference model consists of submodels possessing safe system behaviors that are governed by switching signals to achieve satisfactory performances. A state-dependent switching control technique based on the time-varying safe sets is proposed by utilizing the multiple Lyapunov functions method, which guarantees the state of the subsystem is within the corresponding safe set when the subsystem is activated. To deal with uncertainties, a switched adaptive controller with different update laws is constructed by resorting to the projection operator, which reduces the conservatism caused by the common update law adopted in all subsystems. Moreover, a sufficient condition is obtained by structuring a switched time-varying safety function, which ensures the safety of switched systems and the boundedness of error systems in the presence of uncertainties. As a special case, the safety control problem under arbitrary switching is considered and a corollary is deduced. Finally, a numerical example and a wing rock dynamics model are provided to verify the effectiveness of the developed approach.

Fuzzy control of synchronous buck converters utilizing fuzzy inference system for renewable energy applications

<p>In the present research, an innovative fuzzy control approach is developed specifically for synchronous buck converters utilized in renewable energy applications. The proposed control strategy effectively manages load changes, nonlinear loads, and input voltage variations while improving both stability and transient response. The method employs a fuzzy inference system (FIS) that integrates adaptive control, feedforward control, and multivariable control to guarantee optimal performance under a wide range of operating conditions. The design of the control scheme involves formulating a rule base connecting input variables to an output variable, which signifies the duty cycle of the switching signal. The rule base is configured to dynamically modify control rules and membership functions in accordance with load conditions, input voltage fluctuations, and other contributing factors. The performance of the control scheme is evaluated in comparison to conventional techniques, such as proportional integral derivative (PID) control. Results indicate that the advanced fuzzy control approach surpasses traditional methods in terms of voltage regulation, stability, and transient response, particularly when faced with variable load conditions and input voltage changes. As a result, this control scheme is highly compatible with renewable energy systems, encompassing solar and wind power installations where input voltage and load conditions may experience considerable fluctuations. This research highlights the potential of the proposed fuzzy control approach to significantly enhance the performance and reliability of renewable energy systems.</p>

Secure Filter Design of Fuzzy Switched CPSs With Mismatched Modes and Application: A Multidomain Event-Triggered Strategy

This article investigates the finite-time secure filter design of fuzzy switched cyber-physical systems equipped with a resource-constraint network that may undergo false data injection attacks (FDIAs). To strike a higher level balance between the resource consumption and filtering performance, a multidomain probabilistic event-triggered mechanism (MDPETM) is initially developed. And the mode mismatched phenomenon between the filter and the system is characterized through a delayed switching signal. Based on the MDPETM and a virtual delay partitioning approach, fuzzy mismatched secure filters are first devised whose modes could differ from the system. Then, filter-mode-dependent Lyapunov functionals are created to obtain new sufficient criteria such that the filtering error achieves finite-time boundedness with extended dissipativity subject to admissible FDIAs. The filter gains are obtained by solving a set of convex optimization problems. Finally, an application-oriented example is employed to test the effectiveness and advantages of the proposed results.

An antibody-based molecular switch for continuous small-molecule biosensing.

We present a generalizable approach for designing biosensors that can continuously detect small-molecule biomarkers in real time and without sample preparation. This is achieved by converting existing antibodies into target-responsive "antibody-switches" that enable continuous optical biosensing. To engineer these switches, antibodies are linked to a molecular competitor through a DNA scaffold, such that competitive target binding induces scaffold switching and fluorescent signaling of changing target concentrations. As a demonstration, we designed antibody-switches that achieve rapid, sample preparation-free sensing of digoxigenin and cortisol in undiluted plasma. We showed that, by substituting the molecular competitor, we can further modulate the sensitivity of our cortisol switch to achieve detection at concentrations spanning 3.3 nanomolar to 3.3 millimolar. Last, we integrated this switch with a fiber optic sensor to achieve continuous sensing of cortisol in a buffer and blood with <5-min time resolution. We believe that this modular sensor design can enable continuous biosensor development for many biomarkers.

Absolute exponential stability of switching Lurie systems with time-varying delay via dwell time switching

This paper addresses the absolute exponential stability analysis for switching Lurie systems with time-varying delay. With the switching time-varying Lyapunov functions technique, sufficient conditions in terms of linear-matrix inequalities are presented to ensure the absolute exponential stability of switching Lurie systems with time-varying delay under mode-dependent dwell time switching signals. Furthermore, the conservatism of the proposed method for stability analysis is studied. Simulation examples illustrate the validity of the obtained results.

Light-by-light polarization control using Stimulated Brillouin Scattering with retardance spectrum shaping

The spectral broadening of a nonlinear polarization retarder based on the polarization dependent interactions of Stimulated Brillouin Scattering is proposed and demonstrated. Through phase-to-retardance conversion, it is shown that polarization can not only be controlled in a bandwidth wider than the natural Brillouin response, but it can also be tailored to provide a certain retardance profile. Broadening is achieved through the engineering of Brillouin phase frequency response via feedback pump regulation, unlike previous schemes based on amplitude and time delay control. Retardance broadening from 51 MHz (natural SBS interaction) to 0.9 GHz along with retardance flattening is demonstrated. This technique contributes to expand optical signal processing tools and opens new possibilities in all-optical switching and routing of data signals as well as in the field of microwave photonics.

Nonfragile observer-based event-triggered fuzzy tracking control for fast-sampling singularly perturbed systems with dual-layer switching mechanism and cyber-attacks

This paper investigates the problem of nonfragile observer-based tracking control for a class of fuzzy fast-sampling singularly perturbed systems (SPSs) with sensor saturation, which subject to event-triggered scheme and random cyber-attacks. The switching topology of the fast-sampling SPSs is dominated by a dual-layer switching mechanism, in this case, the Markov process in the underlying system is nonhomogeneous and its time-varying transition probabilities (TPs) are governed by a persistent dwell-time switching signal. First, in order to avoid asynchronous phenomenon of premise variable between the fuzzy fast-sampling SPSs and the fuzzy controller under network environments, the non-parallel distributed compensation (non-PDC) technique is applied to improve the design flexibility and reduce the conservativeness of the results. Furthermore, a novel fuzzy tracking control design scheme is proposed, in which integrating the fuzzy nonfragile observer and reference model signal into the synthetic design of the tracking controller can be expected to reduce the tracking error. Second, by constructing a well-designed time-delay and mode-dependent Lyapunov function, some sufficient conditions are derived such that the closed-loop system is mean-square exponential stable and with extended dissipative tracking performance. Finally, the effectiveness and applicability of the proposed control protocol are illustrated by two simulation examples.

Probabilistic event-triggered protocol for switched power systems under multi-strategy deception attack

This paper focuses on the security control of a discrete-time switched power system utilizing a probabilistic event-triggered protocol under a multi-strategy deception attack. To better characterize the system mode’s switching behavior, a novel nonhomogeneous sojourn probability is introduced, which is modulated by a upper-level deterministic switching signal. Furthermore, a multi-strategy deception attack is established, wherein different deception attack strategies randomly target various nodes during signal transmission through the network carrier to the controller. To optimize network resource utilization, a probabilistic event-dependent triggering protocol based on a triggering threshold interval is presented, which effectively reduces unnecessary communication, leading to resource savings. Subsequently, sufficient conditions for the closed-loop system’s input-to-state stability in probability is derived. Finally, the effectiveness of the proposed control strategy is demonstrated through simulation results, which verify its capability in enhancing system security and stability, while efficiently utilizing network resources.

Consensus control of multi‐agent systems with switched linear dynamics

AbstractIn this work, the consensus problem of multi‐agent systems is addressed whose agent dynamics are described by the switched linear system, and the interaction topology is a directed graph. Two cases are considered: For completely controllable agent dynamics, a novel construct method of control law and switching signal are proposed to derive sufficient conditions to solve the finite‐time consensus problem. When the controllability of the agent system is incomplete, it is proven that the uncontrollable sub‐mode of agent dynamics is consistently asymptotically stabilizable is a key condition to achieve consistency for multi‐agent systems. Finally, numerical examples are provided to demonstrate the effectiveness of the theoretical results obtained in this paper.

Event-Triggered State Estimation for Networked Switched Systems: An Output Predictor Approach

In this article, we investigate the event-triggered state estimation for networked switched systems with (a)synchronous switching. A new multimode output predictor-based sampled-data observer and an event-triggered mechanism are proposed. Between event-triggered sampling times, an output predictor is utilized to compensate for the impact of sampling, and at the sampling instants, the predicted output is reset with the updated sampled output. Two scenarios are considered: the observer's switching signal is synchronous with the system's switching signal, and the switching signals among them are asynchronous, and frequent switching is allowed during interevent intervals. Average dwell time and linear matrix inequalities techniques are employed to guarantee the global uniform exponential convergence of the proposed observer. Moreover, Zeno phenomenon can be ruled out by proving the existence of a positive lower bound of interevent intervals. Finally, the effectiveness of the proposed approach is illustrated by a circuit system and an academic example.

A Millimeter-Wave Mixer-First Receiver With LO Waveform Shaping Using Varactors

A mixer-first receiver is proposed, which uses an overlap-suppressed local oscillator (LO) signal for the mixer switching. A sinusoidal LO wave can be shaped into a sharper waveform by adding a second-harmonic component to the fundamental one. This is readily achieved by integrating accumulation MOS varactors with LO buffers. The receiver is implemented in a 28-nm bulk CMOS and achieves an input 1-dB gain compression power in the range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 12.6 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 14.3 dBm and a noise figure (NF) in the range of 8.4–9.6 dB at frequencies of 24–29 GHz while consuming 12.6-mW power.

Low-loss Optical Switching Based on Phase-change Material Sb2Se3 in a Micro-ring Resonator

In the past research, optical interconnection has successfully developed into an emerging technology due to its compatibility with CMOS, where an efficient and reconfigurable optical switch operating at ultra-low programming energy is a key element to realize optical signal routing and switching. Here we numerically demonstrate an optical switch operating in the telecommunications band, which shows a 20 dB switch ratio and insertion loss of 0.8 dB. The device is implemented in waveguide-coupled micro-ring resonator (MRR) using the phase materials Sb2Se3, which exhibits high contrast in its optical properties upon transitions between its crystalline and amorphous structural phases.

Dynamic Output Feedback Fault Tolerant Control for Switched Fuzzy Systems With Fast Time Varying and Unbounded Faults

This paper focuses on the fault reconstruction and fault-tolerant control problems of switched fuzzy systems with actuator and sensor faults, where the faults may be fast time-varying and unbounded. The multiple coordinate transformations are introduced, then the reduced-order observer based fault reconstruction method is considered, which can reconstruct the system state, actuator and sensor faults, simultaneously. For the case that there is no disturbance, the LMI conditions are achieved to insure that for any switching signal, the error dynamics can be exponentially stable. Utilizing the estimated fault information, the fuzzy dynamic output feedback fault tolerant controllers are designed to compensate the fault effect and stabilize the systems. The root-mean-square gain is considered to reduce the disturbance influence on fault estimation and fault-tolerant control, in which the zero initial condition is not needed. Finally, simulations are conducted to demonstrate the effectiveness of the considered techniques.

Double-Stage Rate Bumpless Transfer Control for Switched Systems With Severely Unstable Dynamics

This brief investigates the double-stage rate bumpless transfer (DSRBT) control for switched linear systems possing severely unstable dynamics (SUDs). The considered SUDs mean all destabilizing subsystems and partially destabilizing switching instants. A new DSRBT performance is defined, which implies the transient control purpose can be achieved under asynchronous switching. Then, an improved dwell time method that restricts the ratio of the total number of stabilizing and destabilizing switching instants is proposed, in which the ratio is designed without incorporating additional parameters. By co-designing a switching signal and a series of dynamic output feedback controllers, a sufficient condition is given to ensure both the exponential stabilization and the DSRBT performance. Finally, a numerical example and an application of the tunnel diode circuit are given to demonstrate the effectiveness of the proposed method.

Total-Activity Conservation Analysis and Design of Boolean Networks.

The law of conservation of mass, represented in Boolean networks (BNs) as total-activity conservation, is one of the typical properties of biological networks. This article analyzes the total-activity conservation of BNs based on the algebraic state-space representation (ASSR) approach. First, the total-activity-conservative matrix is defined and a matrix-based criterion is proposed to verify the total-activity conservation of BNs. Meanwhile, when function perturbation is considered, robust total-activity conservation is investigated. Second, by means of the pseudo-Boolean function generated by total-activity conservation, a constructive design procedure of the Boolean dynamics is given to achieve the total-activity conservation. Third, the total-activity conservation of switched Boolean networks (SBNs) under arbitrary switching signal is studied, which together with network aggregation achieves the total-activity conservation of large-scale BNs.

Observer-Based Global Event-Triggered Control for a Class of Switched Nonlinear Systems

This note studies the global event-triggered control problem for a class of switched nonlinear systems in the sense of output feedback by the average dwell-time method. Since system switching has no regularity and the controller is only updated at triggering instants, the mismatch behavior may happen between the controller and its corresponding subsystem, which may lead to a destroyed system performance. To derive a flexible triggering condition and solve this problem, two dynamic gains are introduced and a mode-dependent dynamic triggering mechanism is designed. Then, by using the weighted homogeneity and inequality techniques, a mode-dependent dynamic event-triggered controller is developed by output feedback, under which the system states can globally enter an adjusted neighborhood of the origin. Meantime, by the skillful use of the right-continuous property of the switching signal, the Zeno behavior is proved to be avoided. Finally, as the effectiveness verification, two practical examples are provided.

Protocol-Based Load Frequency Control for Power Systems With Nonhomogeneous Sojourn Probabilities

This article is concentrated on the load frequency control for interconnected multiarea power systems (IMAPSs) with nonhomogeneous sojourn probabilities (NSPs) and cyber-attacks. A generalized framework of NSPs is formulated to describe the dynamic behavior of IMAPSs. To govern variations of sojourn probabilities, a deterministic switching signal is introduced using the average dwell-time technique. Essentially, different from the existing protocols, an improved event-triggered protocol that is relevant to the dynamic quantizer parameter is presented, thereby increasing triggering intervals. Furthermore, both denial-of-service and deception attacks, which obey Bernoulli distributions, are considered during information transmission. By virtue of the Lyapunov theory, the mean-square exponential stability of the considered systems is established. Finally, the effectiveness of the obtained results is verified via a numerical example.

Stochastic Synchronization of Semi-Markovian Switching Cyber-Physical Impulsive Complex Networks via Dynamic Event-Triggered SMC

In this paper, a novel dynamic event-triggered sliding mode control (SMC) scheme is developed to investigate the stochastic synchronization of semi-Markovian switching cyber-physical complex network (SSCCN) with impulsive effects. First of all, the mode-dependent average dwell time (MDADT) and the transition probability (TP) are introduced to express the semi-Markovian switching signal, which makes the proposed model more applicable than other systems where only the average dwell time (ADT) switching is provided. Moreover, to prevent system uncertainty and unnecessary data transmission, a new dynamic event-triggered mechanism is incorporated into the design of SMC. In most of the existing event-triggered SMC strategies, the continuity of sliding mode surfaces for SSCCN is lost due to intermittent impulsive effects and stochastic switching in the system. Considering this problem, a piecewise mode-independent integral sliding function is put forward that takes into account the dynamic properties of the impulses through the proposed dynamic event-triggered mechanism. It can not only obtain the continuous trajectories of the impulsive networked system, but also significantly reduce the number of event triggers. Some rigorous analytical techniques have been developed to obtain the sufficient conditions required to ensure both the mean square synchronization (MSS) and almost sure synchronization (ASS) of SSCCN. Finally, some numerical examples are presented to demonstrate the effectiveness of the theoretical analysis.

Recent developments of Boolean networks with switching and constraints

A switched Boolean network (SBN) is an important model for describing hybrid phenomena in gene regulatory networks, and it has received increasing attention since the development of the semi-tensor product of matrices. This paper aims to present a comprehensive survey on SBNs. First, the fundamental issues for SBNs with arbitrary switching signals are reviewed, including stability, stabilisation, controllability, observability, optimal control, and synchronisation. Next, a brief review of the stability analysis of SBNs with constrained switching, consisting of time-dependent switching, state-dependent switching, and logical switching, is given. In addition, some basic results on the SBNs under non-ideal conditions are also introduced comprehensively.