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Cranes are widely employed for transportation in many industrial fields. However, strong couplings and high nonlinearities increase difficulty of designing effective control methods for crane systems. Additionally, complex environments may bring uncertainties and unfavorable factors for the control problem. In this paper, we design an effective tracking approach for double pendulum cranes considering variable rope lengths problem by using sliding mode technique, to further improve the robustness and achieve the control objectives of accurate tracking, while effective suppression for double pendulum swing is also ensured. We design a proper sliding mode surface containing all state variables, which effectively suppresses swing angles of the payload and the hook. Then, the time delay estimator technique is used to estimate parameter uncertainty-related terms and the estimation errors are effectively tackled by using sliding mode technique. The effectiveness is rigorously proved by Lyapunov stability theory. At last, comprehensive simulations are implemented to show the proper performance. • The effective tracking objective for the trolley and the rope is achieved. • The parameter uncertainty is successfully solved by sliding mode technique. • The swing suppression performance is theoretically proved. [ABSTRACT FROM AUTHOR]

This paper proposes a new control strategy to deal with three different types of uncertainties for a class of time-varying delay nonlinear systems. Quite different from related celebrated works, the considered systems allow the existence of parameter uncertainties in the output function and nonlinearities, dynamic uncertainties of the unmeasurable state, and continuous external disturbances, which invokes the motivation of the paper. The objective is to construct a continuous output feedback controller by utilizing a new restructured integral function and the double-domination method. The novelty control design is the capability of tackling zero-dynamic and unknown output function simultaneously, thereby guaranteeing the state convergence of the closed-loop system. Finally, the proposed scheme is applied to a practical example and a numerical one simultaneously to demonstrate the effectiveness and the superiority. • This paper is an important theoretical work to deal with the output feedback stabilization problem of time-delay nonlinear systems, since it provides a new idea to handle parameter uncertainties in the output function and nonlinearities, dynamic uncertainties of the unmeasurable state, and continuous external disturbances. • This method overcomes the influence of dynamic/parametric uncertainties and time-varying terms, and provides an insight for the combination of output feedback stabilizer and state observer for uncertain control systems. • To eliminate the effect of dynamic uncertainties, a nondecreasing positive continuous function is used to construct an appropriate integral Lyapunov function in stability analysis. [ABSTRACT FROM AUTHOR]

The manuscript focuses on the interval type-2 (IT2) fuzzy sampled-data H∞ control problem for nonlinear systems with parameter uncertainties and random communication. Nonlinear systems are constructed as Takagi–Sugeno (T–S) fuzzy form, and the parameter uncertainties are represented by employing the membership functions. A reliable controller is designed, based on which the fuzzy closed-loop system is stable and the H∞index is satisfied. In the analysis, the free-weighting matrices and the slack ones are introduced, and the mathematical expectation and the linear matrix inequalities (LMIs) are used. Furthermore, by taking the inverted pendulum system as an example, the superiority and applicability of the control strategy are demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, stable and adaptive neural network compensators are proposed to control the uncertain permanent magnet synchronous motor (PMSM). Firstly, the overall uncertainties caused by mathematical modelling, parameters variation during operation and external load torque disturbances are modelled. Secondly, a new motion control scheme, where (dq) current loops are dotted by two on-line tuning neural network compensators (NNCs), is used to compensate these uncertainties. As a result, the speed control loop is processed easily by proportional integral (PI) controller. Stability of the closed-loop system is also designed according to the Lyapunov stability. Compared to classical vector control, the simulations of PMSM system at different speeds including nominal, low and high speed, with and without uncertainties, show the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

A large portion of the frameworks in the business contain extraordinary nonlinearity and vulnerabilities, which are difficult to outline and control using general nonlinear frameworks. To vanquish these kind of inconveniences, distinctive plans have been created in the last two decades, among which a well-known procedure is Takagi–Sugeno fuzzy control. In this paper, this work presents strong adjustment and control of Takagi–Sugeno (T–S) fuzzy frameworks with parameter vulnerabilities and aggravations. At first, Takagi and Sugeno (T–S) fuzzy model is utilized to speak to a nonlinear framework. In light of this T–S fuzzy model, fuzzy controller configuration plans for state input, and yield criticism is likewise created. At that point, vital conditions are inferred for strong adjustment insight of Lyapunov asymptotic security and are communicated in the Linear Matrix Inequalities (LMIs). The proposed framework is implemented in the working stage of MATLAB and the simulation results are given to represent the efficacy of the proposed strategies. [ABSTRACT FROM AUTHOR]

Abstract This paper is concerned with the observer-based control problem for Markovian jump delay systems with parameter uncertainties using quantized measurements. The parameter uncertainties are assumed to be norm bounded. The aim is to design a suitable observer-based controller which guarantees the stochastic stability of the resulting closed-loop system with a prescribed mixed passivity and H ∞ performance index. A novel stability criterion is obtained by constructing a mode-dependent Lyapunov–Krasovskii functional based on the delay-partitioning technique. Then, with the novel stability criterion, sufficient conditions for the solvability of the presented observer-based controller design problem are derived. All the results obtained in this paper can be tackled by a feasibility problem in terms of linear matrix inequalities. Finally, three numerical examples are provided to illustrate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

High-precision navigation algorithm is essential for the future Mars pinpoint landing mission. The unknown inputs caused by large uncertainties of atmospheric density and aerodynamic coefficients as well as unknown measurement biases may cause large estimation errors of conventional Kalman filters. This paper proposes a derivative-free version of nonlinear unbiased minimum variance filter for Mars entry navigation. This filter has been designed to solve this problem by estimating the state and unknown measurement biases simultaneously with derivative-free character, leading to a high-precision algorithm for the Mars entry navigation. IMU/radio beacons integrated navigation is introduced in the simulation, and the result shows that with or without radio blackout, our proposed filter could achieve an accurate state estimation, much better than the conventional unscented Kalman filter, showing the ability of high-precision Mars entry navigation algorithm. [ABSTRACT FROM AUTHOR]

This paper concerns wire rope tension control of a double-rope winding hoisting system (DRWHS), which consists of a hoisting system employed to realize a transportation function and an electro-hydraulic servo system utilized to adjust wire rope tensions. A dynamic model of the DRWHS is developed in which parameter uncertainties and external disturbances are considered. A comparison between simulation results using the dynamic model and experimental results using a double-rope winding hoisting experimental system is given in order to demonstrate accuracy of the dynamic model. In order to improve the wire rope tension coordination control performance of the DRWHS, a robust nonlinear adaptive backstepping controller (RNABC) combined with a nonlinear disturbance observer (NDO) is proposed. Main features of the proposed combined controller are: (1) using the RNABC to adjust wire rope tensions with consideration of parameter uncertainties, whose parameters are designed online by adaptive laws derived from Lyapunov stability theory to guarantee the control performance and stability of the closed-loop system; and (2) introducing the NDO to deal with uncertain external disturbances. In order to demonstrate feasibility and effectiveness of the proposed controller, experimental studies have been conducted on the DRWHS controlled by an xPC rapid prototyping system. Experimental results verify that the proposed controller exhibits excellent performance on wire rope tension coordination control compared with a conventional proportional-integral (PI) controller and adaptive backstepping controller. [ABSTRACT FROM AUTHOR]

The robust H∞ consensus control problem of high-order discrete-time multi-agent systems with parameter uncertainties and external disturbances is studied, and a linear distributed consensus protocol is designed in this paper. Firstly, the robust H∞ consensus control problem of high-order discrete-time multi-agent systems with parameter uncertainties and external disturbances is transformed to a robust H∞ control problem of a set of independent uncertain systems. Secondly, a suffcient linear matrix inequality (LMI) condition is derived to insure that high-order discrete-time multi-agent systems with parameter uncertainties and external disturbances achieve robust consensus with a H∞ performance level γ. Thirdly, convergence results are given as final consensus values of high-order discrete-time linear multi-agent systems with parameter uncertainties and without external disturbances. Finally, a contrast numerical experiment with and without parameter uncertainties is provided to demonstrate the correctness and effectiveness of the theoretical results. [ABSTRACT FROM AUTHOR]

The antiswing control and accurate positioning are simultaneously investigated for underactuated crane systems in the presence of two parallel payloads on the trolley and rail length limitation. The equations of motion for the crane system in question are established via the Euler–Lagrange equation. An adaptive control strategy is proposed with the help of system energy function and energy shaping technique. Stability analysis shows that under the designed adaptive controller, the payload swings can be suppressed ultimately and the trolley can be regulated to the destination while not exceeding the pre-specified boundaries. Simulation results are provided to show the satisfactory control performances of the presented control method in terms of working efficiency as well as robustness with respect to external disturbances. [ABSTRACT FROM AUTHOR]

This paper presents a super-twisting algorithm control strategy for a three-phase voltage source inverter of a distributed generation system in the stand-alone operation mode to guarantee good performance of the load output voltage under a sudden load, unbalanced load, and nonlinear load. The proposed control is established for an inner-loop current controller and an outer-loop voltage controller in a dual-control scheme. The proposed controller is very simple and robust to the parameter uncertainties. The stability and robustness of the proposed controller are proven based on the Lyapunov theory. The simulation results are illustrated by MATLAB/Simulink software and are compared to the performance of the traditional sliding controller to validate the effectiveness of the proposed controller. [ABSTRACT FROM AUTHOR]

A two-loop robust nonlinear controller is proposed to deal with uncertain model parameters in HIV infection models, which are described by nonlinear differential equations of three state variables and antiretroviral drugs. The treatment goal is to suppress the concentration of infected CD4+ T cells to a target value using only the measurement of total CD4+ T cell concentration. The outer-loop controller is designed to achieve the treatment goal for the nominal HIV infection model, while a nonlinear disturbance observer (DOB) controller is employed in the inner-loop to compensate for parameter uncertainties. In the nonlinear DOB controller, a disturbance signal, equivalent to the parameter variation in terms of effect on the output, is canceled by its estimate. Numerical simulations verify that the proposed controller achieves robust performance for reducing the concentration of infected CD4+ T cells even in the presence of parameter uncertainties. [ABSTRACT FROM AUTHOR]

In this paper, the problem of time optimal trajectory planning under confined torque and uncertain dynamics and torque parameters along a predefined geometric path is considered. It is shown that the robust optimal solution to such a problem can be obtained by solving a linear program. Thus a tractable algorithm is given for robust time-optimal path-tracking control under confined torque. [ABSTRACT FROM AUTHOR]

Abstract: This paper is concerned with the problem of robust fault-tolerant compensation control problem for uncertain linear systems subject to both state and input signal quantization. By incorporating novel matrix full-rank factorization technique with sliding surface design successfully, the total failure of certain actuators can be coped with, under a special actuator redundancy assumption. In order to compensate for quantization errors, an adjustment range of quantization sensitivity for a dynamic uniform quantizer is given through the flexible choices of design parameters. Comparing with the existing results, the derived inequality condition leads to the fault tolerance ability stronger and much wider scope of applicability. With a static adjustment policy of quantization sensitivity, an adaptive sliding mode controller is then designed to maintain the sliding mode, where the gain of the nonlinear unit vector term is updated automatically to compensate for the effects of actuator faults, quantization errors, exogenous disturbances and parameter uncertainties without the need for a fault detection and isolation (FDI) mechanism. Finally, the effectiveness of the proposed design method is illustrated via a model of a rocket fairing structural-acoustic. [Copyright &y& Elsevier]

Abstract: This paper assesses how parameter uncertainties in the model for rise velocity of CO2 droplets in the ocean cause uncertainties in their rise and dissolution in marine waters. The parameter uncertainties in the rise velocity for both hydrate coated and hydrate free droplets are estimated from experiment data. Thereafter the rise velocity is coupled with a mass transfer model to simulate the fate of dissolution of a single droplet. The assessment shows that parameter uncertainties are highest for large droplets. However, it is also shown that in some circumstances varying the temperature gives significant change in rise distance of droplets. [Copyright &y& Elsevier]

Aimed at the parameter uncertainties and extra torque in passive force control system, an adaptive baekstepping controller is proposed based on the established nonlinear model of the system. The stability of the controller is testified by the Lyapunov stability theory, in which the parameter uncertainties and extra torque are considered. The nonlinear model of the system is established to construct several new virtual subsystems, then the backstepping thought is introduced to the design of the dummy controllers for each dummy subsystem. By backstepping recurrence, the nonlinear controller with parameter uncertainties and disturbance of load bearing system is obtained. The result of simulation shows that the designed controller can eliminate extra torque better compared with traditional controller, which proves the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

A dynamic output feedback guaranteed cost control approach is presented for structures with model parameter uncertainties under seismic excitations. With quadratic cost function given, sufficient conditions for the existence of such an output feedback guaranteed cost controller are derived in the framework of linear matrix inequality optimization, while the steps for controller designing are suggested. To verify the effectiveness of the proposed guaranteed cost control strategy, a six-storey building subjected to a deterministic earthquake acceleration record or to a Kanai-Tajimi filtered white noise random excitation is investigated respectively, which shows that whether the model parameter uncertainties exist or not, the guaranteed cost controller can provide satisfactory results. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with the problem of robust state feedback stabilization for uncertain switched linear systems with state delay. The system under consideration involves time delay in the state, parameter uncertainties and nonlinear uncertainties. The parameter uncertainties are norm-bounded time-varying uncertainties which enter all the state matrices. The nonlinear uncertainties meet with the linear growth condition. In addition, the impulsive behavior is introduced into the given switched system, which results a novel class of hybrid and switched systems called switched impulsive control systems. Using the switched Lyapunov function approach, some sufficient conditions are developed to ensure the globally robust asymptotic stability and robust disturbance attenuation performance in terms of certain linear matrix inequalities (LMIs). Not only the robustly stabilizing state feedback controller and impulsive controller, but also the stabilizing switching law can be constructed by using the corresponding feasible solution to the LMIs. Finally, the effectiveness of the algorithms is illustrated with an example. [Copyright &y& Elsevier]

This paper investigates the stability robustness of linear output feedback systems with actuator saturation as well as both time-varying structured (elemental ) and unstructured (norm-bounded) parameter uncertainties by directly considering the mixed quadratically coupled uncertainties in the problem formulation. Based on the Lyapunov approach and some essential properties of matrix measures, a new sufficient condition is proposed for ensuring that the linear output feedback systems with actuator saturation as well as both time-varying structured and unstructured parameter uncertainties are robustly stable. A numerical example is given to illustrate the application of the presented sufficient condition. [ABSTRACT FROM AUTHOR]

Robust model reference control for multivariable linear systems with structural parameter uncertainties is considered. It is shown that the problem can be decomposed into two subproblems: a robust state feedback stabilization problem for multivariable linear systems subject to parameter uncertainties and a robust compensation problem. The latter concerns solution of three coefficient matrices such that four matrix equations are met and, simultaneously, the effect of the uncertainties to the tracking error is minimized. Based on a complete parametric solution to a class of generalized Sylvester matrix equations, the robust compensation problem is turned into a minimization problem with quadratic cost and linear constraints. A set of linear equations is derived that determines the optimal solution to the minimization. An example illustrates the application of the proposed approach. [ABSTRACT FROM AUTHOR]