准噶尔盆地侏罗系三工河组层序界面结构分析

通过对露头，钻井测井和地震资料的研究，认为在准噶尔盆地侏罗系三工河组J1s^22砂体之中从反旋回的转折点上发育一侏罗系内部层序界面，该界面的识别标志明显，在露头，钻井，测井以及地震剖面中具有较好的反映，由于J1s^22砂体的组合关系在盆地不同部位具有较大的差别，因而导致该界面的表现样式具有极大的差别，主要表现为层序底界具有上下岩性接触关系复杂，沿层地球物理参数变化多端以及多端以及界面上下地震反射结构差异较大等特征，因此该界面在全盆范围内非均一性特征突出，而形成该界面均一性的主控因素为构造活动特别是盆地内的局部构造活动的差异性导致的不同区域可容空间的变化，此外沉积供给和气候的变化也是主要影响因素之一。     

Approximate finite-dimensional filtering for polynomial states over polynomial observations

In this article, the mean-square filtering problem for polynomial system states over polynomial observations is studied proceeding from the general expression for the stochastic Ito differentials of the mean-square estimate and the error variance. In contrast to the previously obtained results, this article deals with the general case of nonlinear polynomial states and observations. As a result, the Ito differentials for the mean-square estimate and error variance corresponding to the stated filtering problem are first derived. The procedure for obtaining an approximate closed-form finite-dimensional system of the filtering equations for any polynomial state over observations with any polynomial drift is then established. In the example, the obtained closed-form filter is applied to solve the third-order sensor filtering problem for a quadratic state, assuming a conditionally Gaussian initial condition for the extended third-order state vector. The simulation results show that the designed filter yields a reliable and rapidly converging estimate.     

Continuous Fixed‐Time Convergent Super‐Twisting Algorithm in Case of Unknown State and Disturbance Initial Conditions

This paper presents a fixed‐time convergent super‐twisting‐like algorithm designed to provide a direct extension, without any additional terms, of the conventional super‐twisting control system, whose state initial condition is unknown and the disturbance initial condition is bounded by a known constant or even completely unknown. The fixed‐time convergent super‐twisting‐like algorithm is first designed for a scalar system and then generalized to a multivariable one. An upper estimate of its convergence (settling) time is calculated in each case. Several examples are provided to illustrate the obtained theoretical results.     

Nonstationary H∞ dynamic output feedback control for discrete‐time Markov jump linear systems with actuator and sensor saturations

This paper is concerned with the nonstationary dynamic output feedback control problem for a class of discrete‐time Markov jump linear systems (MJLSs) under simultaneous consideration of actuator and sensor saturations. The so‐called nonstationary controllers dominated by two other different piecewise‐stationary Markov chains are introduced, making the designed controllers not only mode‐dependent but also dependent on other variations associated with the mode transitions in the original MJLSs. The sufficient conditions formulated in terms of bilinear matrix inequalities for the H_∞ control problem are established such that the resulting closed‐loop system is stochastically stable and achieves a prescribed H_∞ noise attenuation level. A suboptimal algorithm with line search is exploited to solve for the associated controller gains. Effectiveness of the developed theoretical results is verified via a numerical example. Copyright © 2015 John Wiley & Sons, Ltd.     

Adaptive uniform finite-/fixed-time convergent second-order sliding-mode control

ABSTRACT

This paper presents an adaptive gain algorithm for second-order sliding-mode control (2-SMC), specifically a super-twisting (STW)-like controller, with uniform finite/fixed convergence time, that is robust to perturbations with unknown bounds. It is shown that a second-order sliding mode is established as exact finite-time convergence to the origin if the adaptive gain does not have the ability to get reduced and converge to a small vicinity of the origin if the adaptation algorithm does not overestimate the control gain. The estimate of fixed convergence time of the studied adaptive STW-like controller is derived based on the Lyapunov analysis. The efficacy of the proposed adaptive algorithm is illustrated in a tutorial example, where the adaptive STW-like controller with uniform finite/fixed convergence time is compared to the adaptive STW controller with non-uniform finite convergence time.     

Discrete-time optimal control for stochastic nonlinear polynomial systems

This paper presents a solution to the discrete-time optimal control problem for stochastic nonlinear polynomial systems over linear observations and a quadratic criterion. The solution is obtained in two steps: the optimal control algorithm is developed for nonlinear polynomial systems by considering complete information when generating a control law. Then, the state estimate equations for discrete-time stochastic nonlinear polynomial system over linear observations are employed. The closed-form solution is finally obtained substituting the state estimates into the obtained control law. The designed optimal control algorithm can be applied to both distributed and lumped systems. To show effectiveness of the proposed controller, an illustrative example is presented for a second degree polynomial system. The obtained results are compared to the optimal control for the linearized system.     

Resilient Time-Varying Formation-Tracking of Multi-UAV Systems Against Composite Attacks: A Two-Layered Framework

This paper studies the countermeasure design problems of distributed resilient time-varying formation-tracking control for multi-UAV systems with single-way communications against composite attacks,including denial-of-services(DoS)attacks,false-data injection attacks,camouflage attacks,and actuation attacks(AAs).Inspired by the concept of digital twin,a new two-layered protocol equipped with a safe and private twin layer(TL) is proposed,which decouples the above problems into the defense scheme ...