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This work investigates the energy shaping control of a class of underactuated mechanical systems subject to state‐dependent linearly parameterized matched disturbances. To this end, a new integral interconnection and damping‐assignment passivity‐based design is proposed. The controller design is developed for systems subject to either momenta‐dependent disturbances or position‐dependent disturbances or to both simultaneously. The effectiveness of the proposed approach is demonstrated with numerical simulations on three examples: an Acrobot system with nonlinear friction; a ball‐on‐beam system with constant and position‐dependent disturbances; a disk‐on‐disk system with a complete set of state‐dependent disturbances. In all examples, the proposed controller shows better performance compared to previous implementations. [ABSTRACT FROM AUTHOR]

This article addresses the problem of distributed average tracking for second‐order multi‐agent systems with disturbances. The unknown disturbances inject into the velocity dynamics, resulting in the degradation of system stability. An extended state observer is designed to estimate the velocities and disturbances. Then, an observer‐based average tracking protocol is proposed, which does not require velocity measurements, and the unknown disturbances are compensated by the estimations. The protocol is implemented in a distributed fashion, without requiring any global information, and is robust to initialization errors. Through Lyapunov analysis, it is verified that the second‐order multi‐agent system can achieve distributed average tracking under the proposed protocol. Finally, the effectiveness of the control method is demonstrated by simulations. [ABSTRACT FROM AUTHOR]

In this article, we propose a dual‐mode event‐triggered predictive control method for nonlinear systems with bounded disturbances. The proposed method contains two triggering mechanisms, namely, the hybrid threshold‐based event‐triggered model predictive control (HETMPC) mechanism and the event‐triggered linear quadratic regulator mechanism. The former triggering mechanism is designed based on the error between the real state and the optimal state and also the disturbance information acted on the investigated system. Compared with the traditional fixed triggering threshold, the designed HETMPC has a fewer triggering numbers and reduces the computational burden of online real‐time optimization. This event‐triggered mechanism will be adopted before the states go into the terminal invariant set. The latter event‐triggered mechanism is designed based on the derivation of the system state and it will be adopted after the states enter the terminal invariant set. The feasibility and the input‐to‐state practical stability analysis of the designed strategy is presented. Some simulations, including the application to a mass‐spring‐damper system, are provided to show the correctness and feasibility of the designed algorithms. [ABSTRACT FROM AUTHOR]

Summary: This paper studies the consensus problem for one‐sided Lipschitz (OSL) multiagent systems (MASs) affected by bounded disturbances via dynamic edge event‐triggered mechanism (DEETM). Due to disturbances and OSL dynamics in MASs, the event‐triggered consensus problem of which is quite more difficult than those of linear or Lipschitz nonlinear networks without disturbances in the previous works. In order to cope with this problem, a novel consensus method is developed based on DEETM and adaptive technique, which contains adaptive gains in both controller and DEETM. Firstly, smooth adaptive items in controller are designed to significantly compensate unknown disturbances, which can guarantee asymptotic consensus. Moreover, DEETM can effectively reduce the communication cost among neighboring agents, which does not cause Zeno behavior. It is worth noticing that the developed method is fully distributed, which relies on neither global information of the communication topology nor the upper and lower bounds of disturbances. Finally, a simulation example is given to demonstrate the effectiveness of theoretical results. [ABSTRACT FROM AUTHOR]

In this paper, we study the exponential attitude tracking and disturbance rejection problem of rigid body systems. We design a control law for the rigid body system that ensures the exponential convergence of the attitude tracking error and the angular velocity tracking error in the presence of unknown external disturbances. Furthermore, by tuning some design parameters, the exponential convergence rate can be made arbitrarily fast. The effectiveness of our approach is validated by a numerical example. [ABSTRACT FROM AUTHOR]

In this work, based on the robust iterative learning control (ILC) scheme, the finite‐iteration tracking control is investigated for discrete‐time linear systems in repetitive process setting with external disturbances. First, the concept of finite‐iteration tracking is defined. Then by utilizing the lifted‐vector‐matrix technique, the discrete‐time linear system can be reformulated as an input–output transmission equation. Moreover, a P‐type ILC scheme is employed, and then the finite‐iteration tracking of the resultant system is guaranteed with the designed iterative learning controller. Meanwhile, the settling iteration can be explicitly obtained. Particularly, the case of data loss occurred during information transmission is also studied, and sufficient conditions are presented such that the finite‐iteration tracking can be achieved in a finite interval. Lastly, the effectiveness and applicability of the presented method are validated via a numerical simulation. [ABSTRACT FROM AUTHOR]

This article studies the robust state agreement problem for nonlinear multi‐agent systems subject to measurement and actuator disturbances. Under a standard connectivity condition, it is shown that global robust agreement is achievable as long as the interaction functions between the multi‐agent system satisfy a sector bound condition. In addition, a result on local robust state agreement is also given under a relaxed sector bound condition. An interesting lesson drawn from the study is that stronger interactions may destroy the robustness of global state agreement of nonlinear multi‐agent systems with direct and switching topology. [ABSTRACT FROM AUTHOR]

Summary: In this article, a novel output‐feedback control scheme is proposed for nonlinear systems involving unknown input saturation, control gain, and unmeasurable disturbances under the condition of an output constraint. First, a proper barrier Lyapunov function and an opportune backstepping are used to alleviate the control burdens caused by output constraint. Then, a novel auxiliary system is introduced with appropriate coordinate transformation, which can create extra freedoms to attenuate the effects brought by input saturation. As a remarkable feature, a composite observer with the estimate of unknown control gain is constructed on the basis of disturbance observer‐based control and state observer control. It can deal with the unmeasurable disturbances and states simultaneously. According to the proposed scheme, it is proven that all the signals in the closed‐loop system are uniformly ultimately bounded, and the tracking error is bounded by the design parameters and saturated input error without the violation of the output constraint. Finally, the effectiveness of the proposed control is verified by two simulation examples. [ABSTRACT FROM AUTHOR]

Summary: This paper studies the problem of quantized output feedback stabilization for a disturbed discrete‐time switched system. With the quantized output measurement, an extended state current estimator is constructed to estimate the state and disturbance. In the presence of switches and disturbances, the design of quantization scheme becomes a big challenge to avoid the quantizer saturation and guarantee the control precision. In this setup, the well‐applied time‐triggered method to design the update policy of dynamic quantization parameter is hard to implement. We solve the above problem by proposing a novel event‐triggered update policy of quantization parameter, by which the quantizer update is adaptive to the switching signal and the bound of disturbance difference. Consequently, the quantizer saturation is avoided and, combined with the designed dwell‐time switching law, the system state can converge to the origin. The proposed method is illustrated by a numerical example. [ABSTRACT FROM AUTHOR]