共查询到6条相似文献,搜索用时 0 毫秒
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Bao-Lin Zhang Zhihui Cai Shouwan Gao Gong-You Tang 《Journal of The Franklin Institute》2019,356(12):6373-6387
This paper is concerned with the problem of delayed proportional-integral control of an offshore platform subject to self-excited nonlinear hydrodynamic force. By using current and distributed delayed states, a delayed proportional-integral controller is designed to stabilize the offshore platform. Under such a controller, the closed-loop system of the offshore platform is modeled as a nonlinear system with discrete and distributed delays, which allows us to employ the Lyapnov–Krasovskii functional method to analyze its asymptotic stability. Since an affine Wirtinger-based inequality is exploited to estimate the derivative of the Lyapunov–Krasovskii functional, a new stability criterion for the closed-loop system is derived, based on which, suitable control gains can be designed provided that a set of linear matrix inequalities are feasible. It is found through simulation results that the proposed control scheme can improve the control performance remarkably. Moreover, (i) compared with the existing delay-free controllers, the proposed controller can reduce the required control force and the oscillation amplitudes of the platform significantly; and (ii) compared with several delayed controllers, the proposed controller requires less control cost. 相似文献
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针对一类不确定多时滞中立型非线性系统,在其非线性不确定项的范数有界,但其上界未知的情况下,论证了自适应鲁棒控制器存在的条件,并给出了能适应未知参数变化且使得最终闭环系统一致最终有界的鲁棒控制律的设计方法。最后,具体算例的仿真结果说明了此法的有效性。 相似文献
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Hossein Shokouhi-Nejad Amir Rikhtehgar Ghiasi Mohammad Ali Badamchizadeh 《Journal of The Franklin Institute》2017,354(12):4801-4825
This paper concerns the simultaneous fault detection and control (SFDC) problem for a class of nonlinear stochastic switched systems with time-varying state delay and parameter uncertainties. The switching signal of detector/controller unit (DCU) is assumed to be with switching delay, which results in the asynchronous switching between the subsystems and DCU. By constructing a switching strategy depending on the state and switching delays, new sufficient conditions expressed by a set of linear matrix inequalities (LMIs) is derived to design DCU gains. This problem is formulated as an H∞ optimization problem and both mean square exponential stability and fault detection of augmented system are considered. A numerical example is finally exploited to verify the effectiveness and potential of the achieved scheme. 相似文献
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The cell''s micro-environment plays an important role in various physiological and pathological phenomena. To better investigate in vivo cellular behaviors, researchers have expended great effort in building controlled in vitro biophysical and biochemical environments. Because a cell''s gaseous environment affects properties such as its division, metastasis, and differentiation, we developed a zero-flow based platform for studying mammalian cell chemotaxis behavior in different oxygen environments. This platform can construct a linear range of oxygen tensions within one chip (i.e., from 1.4% to 3.6% or 5.5% to 14.5%). To study cell chemotaxis behavior under varying oxygen environments, the chemical gradient direction is established perpendicularly to oxygen change within an observation area. Because the observation area is not subject to flow, shear force is of no concern. In addition, water flow around the cell chambers greatly reduces evaporation and makes long-term microscope imaging possible. In this study, we precisely measure the chemotaxis velocity of MCF-7 human breast cancer cells under different oxygen tension conditions towards CXCL12, which is a stromal cell-derived factor. We find that cell migration rates are not equivalent, even under two close oxygen tensions. We also observed that cells move faster towards high concentrations of chemoattractant when the oxygen tension is below 3% due to the increased expression of HIF-1 (hypoxia-inducible factor 1), which promotes a transition to the amoeboid rather than mesenchymal mode of movement. Our experiments demonstrate that this new microfluidic platform is useful for the quantitative study of mammalian cell chemotaxis under different oxygen conditions in the absence of shear force. We also shed light on the study of chemotaxis under other gaseous environments. 相似文献
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Vu N. Phat 《Journal of The Franklin Institute》2010,347(1):195-207
This paper deals with the problem of stabilization for a class of hybrid systems with time-varying delays. The system to be considered is with nonlinear perturbation and the delay is time varying in both the state and control. Using an improved Lyapunov–Krasovskii functional combined with Newton–Leibniz formula, a memoryless switched controller design for exponential stabilization of switched systems is proposed. The conditions for the exponential stabilization are presented in terms of the solution of matrix Riccati equations, which allow for an arbitrary prescribed stability degree. 相似文献