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In this paper, an adaptive output feedback tracking control scheme is proposed for a class of uncertain nonlinear systems where unknown parameters appear in the form of nonlinear parameterisation. Specific filters are constructed with the output signal and parameter estimates to make state estimation. The nonlinearly parameterised uncertainties are approximated by the Taylor expansion technique and compensation for remainder terms is realised with a series of high-order derivable functions to play the role of sign functions. A smooth positive function and parameter adaption technique are combined to deal with the effect made by state estimation error in the process of stability analysis of the closed-loop system. It is proved that all the signals are guaranteed to be bounded and the tracking error will converge to a small bounded set which is adjustable by tuning certain design constants. Numerical simulation is conducted to verify the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

Summary: In this article, considering actuator constraints and possible failures, an adaptive compensation control scheme is developed to realize tracking control for a class of uncertain nonlinear systems with quantized inputs. A new variable is generated to evaluate the effect of actuator saturation and is used in the process of controller design to compensate for the influence of actuator saturation constraint. Moreover, the controller is able to show certain accommodation capability to tolerate possible actuator failures and input quantization error via integrating parameter update process of unknown fault constants into adaption of parametric uncertainties under the backstepping procedure. Specifically, actuator saturation effect and possible actuator failures as well as input quantization error can be dealt with uniformly under the framework of the proposed scheme and the control system has certain robustness to external disturbances. It is proved that all the signals of the closed‐loop system are ensured to be bounded and the tracking error is enabled to converge toward a compact set, which is adjustable by tuning design parameters. Finally, experiments are carried out on an active suspension plant to illustrate the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

Objective: To assess and compare fetal loss rates before 28 weeks of singleton and twin pregnancies after mid-trimester amniocentesis.Method: This historic cohort study included 13 773 women with singletons and 426 women with twins undergoing mid-trimester amniocentesis from 1/2015 to 3/2017. Pregnancies resulting in termination or selective reduction before 28 weeks were excluded, as well as twin gestations undergoing single-puncture amniocentesis. Fetal loss rates were compared between singleton and twins taking into account maternal characteristics, amniocentesis procedure, and fetal chromosomal abnormalities.Results: The rates of fetal chromosomal abnormalities were similar in singleton and twin gestations (1.13% vs 0.70%, P = .253). No difference was found in maternal or fetal characteristics, or amniocentesis procedure between the two groups. The fetal loss rate was significantly higher in twin compared with singleton pregnancies (1.91% vs 0.24%, P < .001, RR = 8.25 [95% CI: 4.51 to 15.09]). The fetal loss rate between monochorionic twins and dichorionic twins was similar (1.80% vs 1.78%, P = 1.000).Conclusions: Twin pregnancies have higher risk of fetal loss after mid-trimester amniocentesis, which cannot be explained by differences in rates of fetal chromosomal abnormalities, maternal characteristic, or amniocentesis technique. [ABSTRACT FROM AUTHOR]

In this paper, a cooperative region reconnaissance problem is investigated where a group of agents are required to fly across and detect events occur in an environment with static obstacles until an effective coverage is achieved. First, the region reconnaissance is formulated as a non-convex optimization problem. A coverage performance index with additional collision and obstacle avoidance constraints is given. Since the optimization index is an implicit function of state variables and cannot be used to compute gradients on state variables directly, an approximate optimization index is selected. Then, a non-convex optimization-based coverage algorithm is proposed to find the optimal reconnaissance location for each agent and guarantee no collisions trajectories among agents and obstacles. Finally, simulation experiments are performed to verify the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

To investigate the topological structure of finite games, various decomposions of finite games have been proposed. The inner product of vectors plays a key role in the decomposition of finite games. This paper considers the effect of different inner products on the orthogonal decomposition of finite games. We found that only when the compatible condition is satisfied, a common decomposition can be induced by the standard inner product and the weighted inner product simultaneously. To explain the result, we studied the existing decompositions, including potential based decomposition, zero‐sum based decomposition, and normalization based decomposition. For zero‐sum based decomposition and normalization based decomposition, we redefine their subspaces in a linear algebraic framework, which shows their physical meanings clearly. Bases of subspaces in these two decompositions are constructed. [ABSTRACT FROM AUTHOR]

Suspension operation reliability is one of the most significant performance indexes that concerns maneuvering stability and drive safety. In this paper, in order to guarantee good suspension reliability, an adaptive fault detection and isolation scheme is proposed for quarter-car active suspension systems with parametric and nonlinear uncertainties. To realize fault diagnosis for active suspensions, an adaptive fault detection estimator and several fault isolation estimators are designed to generate state residuals. Corresponding adaptive thresholds are developed to help judge the occurrence and type of possible faults. In the process of constructing state estimators, the uncertain parameter is updated online so that good sensitivity of fault detection can be achieved. Illustrative simulation is carried out to validate the effectiveness of the fault diagnosis scheme, and results indicate that the proposed method is sensible to sudden faults and maintain robustness to model uncertainties appearing in suspension systems. [ABSTRACT FROM AUTHOR]

This paper proposes a coverage problem of multi-agent systems, in which a group of agents enter a given region at different times and are required to cover the given region cooperatively. The focus of this paper is to solve the coverage problem of multi-agent systems with a non-convex optimization approach. By introducing appropriate assumptions, a gradient-based control law is designed based on the information of the previous stage agents. However, the performance index of each stage is nonlinear and generally non-convex and may have multiple local optima to which a gradient may converge. Thus, an effective boosting function, which is used to prevent the non-convex optimization problem getting into local optimum, is shown. It is proved in the sense of Lyapunov that the global coverage for the multi-agent systems with different entry time for coming into the given region can be achieved. Numerical simulations with cooperative control of industries subsystems show the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Considering an aircraft threatened by an interceptor, one of the effective penetration strategies is to release a Defender from the aircraft to confront the interceptor. In this case, the aircraft, the Defender, and the interceptor constitute the three-body guidance relationship, and the cooperation of the aircraft and its Defender to achieve the best tactical effects turns into a concerned problem. This paper studies the triangle interception guidance problem via the finite-time theory. The paper presents linear system Input-Output Finite-Time Stabilization (IO-FTS) method. The sufficient conditions of the linear system, being IO-FTS, under Finite-Time Boundedness (FTB) constraint are proposed, by which the state feedback controllers design method is obtained, via Linear Matrix Inequalities (LMIs). The triangle interception guidance problems are studied in three different cases, where the proposed methods are applied to the guidance design. The simulation results illustrate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]