Developed Controller Design Research Articles

Analysis and Design of CD-Cell-Based Fifth-Order Boost Converter With Robust Stability Considerations

The reported fifth-order boost topologies exhibiting gain (1 + D 1)/(1 − D 1) find limited utility in point-of-load applications due to lack of common ground, inverted load voltage polarity, highly pulsating source current, and more switching devices. This article evolves a fifth-order boost converter that successfully overcomes the enlisted limitations. The basis for the evolution of this topology is the addition of a charge-pump capacitor with a diode to the SEPIC converter. This modification alleviates the shortcomings of the existing higher order boost topologies with identical voltage gain. A remarkable feature of this topology is reduced voltage stress on all of its intermediate capacitors. After performing extensive steady-state and state-space analysis, a detailed comparison highlighting significant features is brought out. To demonstrate the proposed converter's utility, a complex proportional–integral lead compensator (PILC) is designed by placing the closed-loop dominant poles satisfying the predefined time-domain specifications, including phase margin, to ensure sufficient stability. PILC gives the flexibility to choose the complex conjugate zeros of the lead portion making the closed-loop system exhibit better disturbance rejection features. The robustness of the designed controller is verified through performance metric computation of the contoured robust controller bode plot. The converter's salient features, the developed controller design, and its robustness against the structured uncertainties are validated experimentally on a 100–150-W prototype module.

Stabilization of uncertain switched discrete-time systems against actuator faults and input saturation

This paper studies the robust fault-tolerant stabilization problem for a class of uncertain switched discrete-time systems subject to time delays, actuator faults and input saturation by using delta operator approach. By constructing an appropriate Lyapunov–Krasovskii functionals in delta domain, a new set of sufficient conditions is provided for the stability of the delta operator time delay switched systems. More precisely, gain matrices of the fault-tolerant controller can be computed by solving the linear matrix inequalities and the proposed controller can robustly stabilize the uncertain delta operator time delay switched system for all admissible parameter perturbations. Further, in order to obtain a maximal estimate of the domain of attraction, an LMI based optimization algorithm is presented. It is noted that a better control performance can be obtained for small sampling periods by using delta operator approach than using shift operator. Finally, numerical examples with simulation results are presented to illustrate the effectiveness and potential of the developed control design technique.

Decentralized fuzzy linguistic control of multiple robotic manipulators with guaranteed global stability

Abstract A decentralized adaptive control based on human linguistic is investigated to learn human behaviors for multiple robotic manipulators. Many experts’ words or sentences can be transferred into the control actions by employing membership functions in robot systems, which can be synthesized fuzzy controller by employing reasoning mechanism. For the unknown model dynamical robot manipulators, one adjustable parameter that relates to the approximation accuracy of fuzzy logic systems is introduced at first, which be utilized to deal with the unknown dynamics of robot manipulators. Switching fuzzy adaptive controller is designed to overcome the limitation of logic structure that the number of adaptive laws only focus on fuzzy rules in conventional fuzzy logic systems. Another advantage of this design method is that the control with human linguistic extend the semi-global stability to global stability. Finally, effectiveness of the developed control design scheme has been shown in simulation example.

Barrier-function-based distributed adaptive control of nonlinear CAVs with parametric uncertainty and full-state constraint

The platoon control of connected and automated vehicles (CAVs) is an emerging problem and has become a hot topic in transportation research. Most of the existing results are based on second-order or third-order linear vehicular dynamics. They ignore either the actuator internal kinetics or vehicular inherent nonlinearity, and the linearization requires a complete priori knowledge of plant parameters and may not be easy to implement in practice. In order to overcome these shortcomings, this paper concentrates on third-order nonlinear vehicular plants with parametric uncertainty and full-state constraint. Different from the popular linear-matrix-inequality (LMI) robust control and model predictive control (MPC), this paper proposes a barrier-function-based distributed adaptive backstepping control scheme. The third-order nonlinear vehicle models are considered, uncertain parameters are identified on-line, full-state constraints are not violated, and the tracking control objectives are established. Simulation studies are carried out to verify the effectiveness of the developed control design.

Robust finite-time stabilization for positive delayed semi-Markovian switching systems

Robust finite-time stabilization is discussed for positive semi-Markovian switching systems (S-MSSs), in which semi-Markovian process, time-varying delay, external disturbance, and transient performance in finite-time level are all considered in a unified framework. In the system under consideration, finite-time problem can describe transient performance of practical control process. Firstly, some finite-time boundedness and L1 finite-time boundedness criteria for positive delayed S-MSSs are proposed by constructing the stochastic semi-Markovian Lyapunov–Krasovskii functional with mode-dependent integral term. Then, a developed L1 finite-time feedback controller design method is presented to reduce some constraints of input matrices, which guarantees the resulting closed-loop system achieves positivity, finite-time boundedness, and has a prescribed L1 noise attenuation performance index in a novel standard linear programming. Finally, a practical example is illustrated to validate the proposed results by applying a virus mutation treatment model.

Model-Matching Fractional-Order Controller Design Using AGTM/AGMP Matching Technique for SISO/MIMO Linear Systems

A new two-stage method is proposed for the model-matching fractional-order (FO) controller (FOC) design for the single-input single-output (SISO) / multiple-input multiple-output (MIMO) linear systems. A streamlined procedure for the selection of reference model M(s), based on a linear quadratic regulator (LQR) with integral action (LQRI) is presented. Since the proposed M(s) is designed using the optimal control theory, the designed output-feedback closed-loop system can be termed as a suboptimal one. Formulation of M(s) incorporates the time-domain characteristics, and the optimal interaction desired to be present in the designed closed-loop system. The developed controller design procedure also works with a user-specified M(s). In the first stage of the controller design, a higher-order controller K(s) which makes the closed-loop system exactly equal to the M(s) is obtained. In the second stage, K(s) is approximated to a FOC or an integer-order (IO) controller (IOC) C(s) with the aim of matching a certain number of approximate generalized time moments (AGTMs) and/or approximate generalized Markov parameters (AGMPs) of K(s) to those of C(s) at a set of frequency points in the s-plane. The simulation and experimental validation of the proposed approach are performed by the design and implementation of the controller for an IO MIMO plant with time-delays. The controller design algorithm is also illustrated based on the user-defined reference model for a FO MIMO plant with time-delays taken from the literature. The obtained results show that the FOC results in better performance compared with its IO counterpart.

Observer-Based Finite-Time Nonfragile Control for Nonlinear Systems With Actuator Saturation

This paper considers a design problem of dissipative and observer-based finite-time nonfragile control for a class of uncertain discrete-time system with time-varying delay, nonlinearities, external disturbances, and actuator saturation. In particular, in this work, it is assumed that the nonlinearities satisfy Lipschitz condition for obtaining the required results. By choosing a suitable Lyapunov–Krasovskii functional, a new set of sufficient conditions is obtained in terms of linear matrix inequalities, which ensures the finite-time boundedness and dissipativeness of the resulting closed-loop system. Meanwhile, the solvability condition for the observer-based finite-time nonfragile control is also established, in which the control gain can be computed by solving a set of matrix inequalities. Finally, a numerical example based on the electric-hydraulic system is provided to illustrate the applicability of the developed control design technique.

Predictor-Based Adaptive Cruise Control Design

We develop a predictor-based adaptive cruise control design with integral action (based on a nominal constant time-headway policy) for the compensation of large actuator and sensor delays in vehicular systems utilizing measurements of the relative spacing as well as of the speed and the short-term history of the desired acceleration of the ego vehicle. By employing an input–output approach, we show that the predictor-based adaptive cruise control law with integral action guarantees all of the four typical performance specifications of adaptive cruise control designs, namely, 1) stability, 2) zero steady-state spacing error, 3) string stability, and 4) non-negative impulse response, despite the large input delay. The effectiveness of the developed control design is shown in simulation considering various performance metrics.

Synchronization of fractional-order complex dynamical network with random coupling delay, actuator faults and saturation

This paper examines the synchronization problem of fractional-order complex dynamical networks (FCDNs) against input saturation and time-varying coupling by using a fault-tolerant control scheme. Precisely, the occurrence of coupling delay assumed is considered to be random, which is characterized by stochastic variables that obeys the Bernoulli distribution properties, and the actuator fault values are represented by a normally distributed stochastic random variable. The main aim of this paper is to propose the fault-tolerant fractional-order controller such that for given any initial condition, the state trajectories of considered FCDN are forced to synchronize asymptotically to the reference node. Based on the linear matrix inequality technique and Lyapunov stability theorem, a new set of sufficient conditions is established to not only guarantee mean-square asymptotic synchronization of the resulting closed-loop system but also cover the issues of actuator saturation and actuator faults. Moreover, the obtained sufficient conditions can help to enlarge the estimation about the domain of attraction for the closed-loop system. Finally, to show the advantages and effectiveness of the developed control design, numerical simulations are carried out on both Lorenz and Chen type FCDNs.

Compensation of actuator dynamics governed by quasilinear hyperbolic PDEs

We present a methodology for stabilization of general nonlinear systems with actuator dynamics governed by a certain class of, quasilinear, first-order hyperbolic PDEs. Since for such PDE–ODE cascades the speed of propagation depends on the PDE state itself (which implies that the prediction horizon cannot be a priori known analytically), the key design challenge is the determination of the predictor state. We resolve this challenge and introduce a PDE predictor-feedback control law that compensates the transport actuator dynamics. Due to the potential formation of shock waves in the solutions of quasilinear, first-order hyperbolic PDEs (which is related to the fundamental restriction for systems with time-varying delays that the delay rate is bounded by unity), we limit ourselves to a certain feasibility region around the origin and we show that the PDE predictor-feedback law achieves asymptotic stability of the closed-loop system, providing an estimate of its region of attraction. Our analysis combines Lyapunov-like arguments and ISS estimates. Since it may be intriguing as to what is the exact relation of the cascade to a system with input delay, we highlight the fact that the considered PDE–ODE cascade gives rise to a system with input delay, with a delay that depends on past input values (defined implicitly via a nonlinear equation). The developed control design methodology is applied to the control of vehicular traffic flow at distant bottlenecks.

On Homogeneous Finite-Time Control for Linear Evolution Equation in Hilbert Space

Based on the notion of generalized homogeneity, a new algorithm of feedback control design is developed for a plant modeled by a linear evolution equation in a Hilbert space with a possibly unbounded operator. The designed control law steers any solution of the closed-loop system to zero in a finite time. A method of homogeneous extension is presented in order to make the developed control design principles to be applicable for evolution systems with nonhomogeneous operators. The design scheme is demonstrated for the heat equation with the control input distributed on the segment ${[}0,1{]}$ .

Predictor-Based Adaptive Cruise Control Design with Integral Action

We develop a predictor-based adaptive cruise control design with integral action (based on a nominal constant time-headway policy) for compensation of long actuator and sensor delays in vehicular systems utilizing measurements of the relative spacing as well as of the speed and the short-term history of the desired acceleration of the ego vehicle. Employing an input-output approach we show that the predictor-based adaptive cruise control law with integral action guarantees all of the four typical performance specifications of adaptive cruise control designs, namely, (1) stability, (2) zero steady-state spacing error, (3) string stability, and (4) non-negative impulse response, despite the long input delay. The effectiveness of the developed control design is illustrated in simulation considering various performance metrics.

Equivalent‐input‐disturbance‐based repetitive tracking control for Takagi–Sugeno fuzzy systems with saturating actuator

This study investigates the output tracking problem for a class of Takagi–Sugeno fuzzy systems subject to periodic signals and actuator saturation via equivalent-input-disturbance (EID) technique. In particular, to ensure the periodic signals tracking, a state-space repetitive control structure is considered. Further, the EID technique is utilised to improve the disturbance rejection performance without any prior knowledge of the disturbance and inverse dynamics of the plant. By constructing a suitable Lyapunov–Krasovskii functional and using the Wirtinger-based integral inequality, a new set of sufficient conditions is derived in terms of linear matrix inequalities (LMIs) which ensures the stability of the addressed system. In addition to that by using a Lyapunov level set, saturation-dependent Lyapunov function captures the real-time information on the severity of actuator saturation and leads to less conservative estimate of the domain of attraction, which is based on the solution of an LMI optimisation problem. Moreover, the designed fuzzy repetitive controller is reliable in the sense that the stability and the satisfactory performance of the closed-loop system are achieved not only under normal operation, but also in the presence of any actuator faults, saturation and dead zone. Finally, the proposed method is validated through two numerical examples to illustrate the effectiveness and superiority of the developed controller design.

Dissipativity-Based Reliable Sampled-Data Control With Nonlinear Actuator Faults

In this paper, the problem of reliable sampled-data control design with strict dissipativity for a class of linear continuous-time-delay systems against nonlinear actuator faults is studied. The main objective of this paper is to design a reliable sampled-data controller to ensure a strictly dissipative performance for the closed-loop system. Based on the linear matrix inequality (LMI) optimization approach and Wirtinger-based integral inequality, a new set of sufficient conditions is established for reliable dissipativity analysis of the considered system by assuming the mixed actuator fault matrix to be known. Then, the proposed result is extended to unknown fault matrix case. Also, the reliable sampled-data controller with strict dissipativity is designed by solving a convex optimization problem which can be easily solved by using standard numerical algorithms. Finally, a numerical example based on liquid propellant rocket motor with a pressure feeding system model is presented to illustrate the effectiveness of the developed control design technique.

Variance-constrained [formula omitted] control for a class of nonlinear stochastic discrete time-varying systems: The event-triggered design

In this paper, a general event-triggered framework is set up to deal with the variance-constrained H∞ control problem for a class of discrete time-varying systems with randomly occurring saturations, stochastic nonlinearities and state-multiplicative noises. Based on the relative error with respect to the measurement signal, an event indicator variable is introduced and the corresponding event-triggered scheme is proposed in order to determine whether the measurement output is transmitted to the controller or not. The stochastic nonlinearities under consideration are characterized by statistical means which can cover several classes of well-studied nonlinearities. A set of unrelated random variables is exploited to govern the phenomena of randomly occurring saturations, stochastic nonlinearities and state-dependent noises. The purpose of the addressed multiobjective control problem is to design a set of time-varying output feedback controller such that, over a finite horizon, the closed-loop system achieves both the prescribed H∞ noise attenuation level and the state covariance constraints. A recursive matrix inequality approach is developed to derive the sufficient conditions for the existence of the desired finite-horizon controllers, and the analytical characterization of such controllers is also given. Simulation studies are conducted to demonstrate the effectiveness of the developed controller design scheme.

Command filtered backstepping tracking control of uncertain nonlinear strict-feedback systems under a directed graph

This paper studies the distributed consensus tracking control problem of multiple uncertain non-linear strict-feedback systems under a directed graph. The command filtered backstepping approach is utilised to alleviate computation burdens and construct distributed controllers, which involves compensated signals eliminating filtered error effects in the design procedure. Neural networks are employed to estimate uncertain non-linear items. Using a Lyapunov stability theorem, it is proved that all signals in the closed-looped systems are semi-globally uniformly ultimately bounded. In addition, consensus errors converge to a small neighbourhood of the origin by adjusting the appropriate design parameters. Finally, simulation results are presented to demonstrate the effectiveness of the developed control design approach.

New results on robust control for a class of uncertain systems and its applications to Chua’s oscillator

This paper addresses the problems of robust stability analysis and stabilization for continuous-time systems with state-dependent uncertainties via constructing a new parameter-dependent Lyapunov function. On the basis of such a parameter-dependent Lyapunov function, the stability conditions for open-loop uncertain systems are first presented. Then a relaxed stability analysis approach that utilizes a property of the time derivatives of uncertain parameters is obtained. To take full advantage of the parameter-dependent Lyapunov function, a model-dependent state-feedback stabilization scheme is proposed, which can provide more flexibilities in controller synthesis. The static state-feedback controller can be seen as a special case of the model-dependent state-feedback controller. A numerical example is provided to illustrate the effectiveness of the proposed approaches. Finally, the developed controller design methodology is applied to stabilization and synchronization of Chua’s oscillator, which has wide applications in secure communication systems and power electronic systems.

Observer-based stabilization of one-sided Lipschitz systems with application to flexible link manipulator

This article is concerned with the observer-based output feedback stabilization problem for a class of nonlinear systems that satisfies the one-sided Lipschitz and the quadratically inner-bounded conditions. The system model under consideration encompasses the classical Lipschitz nonlinear system as a special case. For such a system, we design the output feedback controller via constructing a full-order Luenberger-type state observer. Sufficient conditions that guarantee the existence of observer-based output feedback are established in the form of linear matrix inequalities, which are readily solved by the available numerical software. Moreover, the proposed observer-based output feedback designs are applied to a flexible link manipulator system. Finally, simulation study on the manipulator system is given to demonstrate the effectiveness of the developed control design.

Robust stabilisation of time-varying delay systems with probabilistic uncertainties

For robust stabilisation of time-varying delay systems, only sufficient conditions are available to date. A natural question is as follows: if the existing sufficient conditions are not satisfied, and hence no controllers can be found, what can one do to improve the stability performance of time-varying delay systems? This question is addressed in this paper when there is a probabilistic structure on the parameter uncertainty set. A randomised algorithm is proposed to design a state-feedback controller, which stabilises the system over the uncertainty domain in a probabilistic sense. The capability of the designed controller is quantified by the probability of stability of the resulting closed-loop system. The accuracy of the solution obtained from the randomised algorithm is also analysed. Finally, numerical examples are used to illustrate the effectiveness and advantages of the developed controller design approach.

Decentralized Adaptive Fuzzy Tracking Control for Robot Finger Dynamics

In this paper, a novel design method for adaptive tracking control is proposed for robot finger dynamics. First, the dynamics are described by considering the robot finger as a large-scale system since it has many joints and multi-degrees of freedoms (DOFs). Second, by employing the direct adaptive fuzzy approximation method to approximate the unknown and desired control input signals instead of the unknown nonlinear functions, the number of adaptive design parameters obtained in the control design process is greatly reduced. Moreover, it is shown that the designed controller can guarantee all the signals in the closed-loop system to be semiglobally uniformly ultimately bounded. Finally, simulations are conducted on the Puma 560 robot manipulator, and the results show the effectiveness of the developed control design approach.