Delay-dependent robust stability criteria for uncertain neutral systems with mixed delays

This paper concerns the problem of the delay-dependent robust stability of neutral systems with mixed delays and time-varying structured uncertainties. A new method based on linear matrix inequalities is presented that makes it easy to calculate both the upper stability bounds on the delays and the free weighting matrices. Since the criteria take the sizes of the neutral- and discrete-delays into account, it is less conservative than previous methods. Numerical examples illustrate both the improvement this approach provides over previous methods and the reciprocal influences between the neutral- and discrete-delays.     

一类不确定非线性系统的状态参考自适应滑模控制

针对一类非匹配不确定非线性系统。基于状态参考自适应控制算法和滑模控制策略。提出了状态参考自适应反演滑模控制方案，实现了不确定非线性系统的鲁棒输出跟踪。与现有的控制器设计相比，大大降低了控制系统阶次，允许系统存在非参数化的不确定性和未知扰动，增强了控制系统鲁棒性。仿真算例证明了理论研究成果的正确性和鲁棒性。     

Delay-dependent criteria for robust stability of time-varying delay systems

This paper deals with the problem of delay-dependent robust stability for systems with time-varying structured uncertainties and time-varying delays. Some new delay-dependent stability criteria are devised by taking the relationship between the terms in the Leibniz-Newton formula into account. Since free weighting matrices are used to express this relationship and since appropriate ones are selected by means of linear matrix inequalities, the new criteria are less conservative than existing ones. Numerical examples suggest that the proposed criteria are effective and are an improvement over previous ones.     

考虑风电与高载能负荷调度不确定性的鲁棒机组组合

为缓解弃风问题,甘肃等电网开展了高载能负荷与风电的协调调度。然而,以电弧炉为代表的冶炼类高载能负荷在运行时存在有功功率波动,会对电网的自动发电控制(AGC)系统产生影响。为研究高载能负荷功率波动对负荷与风电协调调度的影响,文中提出一种考虑高载能负荷功率波动以及风电不确定性的鲁棒机组组合方法。该方法充分考虑高载能负荷有功功率波动与设备运行状态的关系,对负荷有功功率的不确定性进行建模。接着,考虑高载能负荷与风电协调调度时,负荷不确定性与风电不确定性对电力系统共同作用的特点,构建最小化弃风与切负荷风险的鲁棒机组组合模型,使电网对高载能负荷进行调控时,可充分考虑高载能负荷不确定性的影响。最后,在IEEE RTS-79系统中对所提方法进行了验证,并分析了高载能负荷不确定性对协调调度的影响。     

Adaptive backstepping control for an n-degree of freedom robotic manipulator based on combined state augmentation

The aim of this paper is to improve the tracking performance of a robotic manipulator by designing an adaptive controller and implementing it on the system. The proposed controller guarantees the system stability as well as good tracking performance in existence of nonlinearity and parameter uncertainties. The requirement to decrease the system response overshoot and steady state error as well as increasing speed of tracking for manipulators is essential to many manufacturers. To this mean, in this paper, the tracking error equations for an n-DOF manipulator are derived and the response characteristics are improved by augmenting a new state to the system equations. The stability of the closed-loop system is guaranteed based on the Lyapunov theory via backstepping control approach. The robotic manipulator model contains parametric uncertainties and many of the parameter values are unknown. To solve the problem, an adaption law is proposed via adaptive backstepping mechanism. Different experiments are carried out for a 2-DOF manipulator to show the effectiveness of the proposed approach and the results are compared with four of the recently revealed researches on control. Experimental results present the superiority of the state augmented adaptive backstepping in tracking the desired joint angles. Moreover, in order to present the industrial application of the proposed control method, it is simulated for a large industrial Scara manipulator.     

Long-time simulation of water distribution systems for the design of small hydropower systems

The implementation of small hydropower systems (SHPS) in existing Alpine Water distribution systems (WDS) is a meaningful strategy for the reduction of CO₂ emissions. Typically, the water consumption patterns of one or several representative days are used for the design procedure of these systems. For the design of the SHPS in WDS, the most important issue is to preserve the water supply without constraints. However, regarding water quality issues (especially related to water age), SHPS can exert a positive influence on the WDS performance. In this study, a long-time simulation model (10 years) is established for a WDS model and is subsequently used for the design of the SHPS. This study is performed to establish a more efficient design of these systems and to evaluate the long-term effects on the pressure and water quality issues, i.e., water age. With a simulation time over one decade on an hourly basis, full load hours and water flows for different turbine sizes are determined in detail. Based on that information, the detailed design and optimisation of the SHPS were performed, and the most cost-efficient device size was determined.     

Buoyancy effects on the laminar boundary layer heat transfer along vertically moving cylinders

Abstract

The effects of buoyancy forces on the laminar boundary layer flow and heat transfer along vertically moving cylinders are analyzed for the cases of prescribed surface temperature and prescribed wall heat flux in power of streamwise distance. Local similarity solutions are obtained to show the effects of buoyancy parameters and the transverse curvature of the cylinder on the surface friction and heat transfer rate.     

An adaptive control scheme using multiple reference models

This paper develops an extended model reference adaptive control scheme to expand the capacity of state feedback state tracking adaptive control to handle the plant‐model matching uncertainties for single‐input LTI systems. The extended scheme is developed, using multiple reference model systems (only one of which is required to be able to match the controlled plant), and multiple controllers (which are updated from adaptive laws generated from multiple reference model systems based estimation errors), as two key features of such design to relax a plant‐model matching condition. A switching mechanism is constructed using those multiple estimation errors, capable of selecting the suitable control input from the multiple control signals, to achieve the desired system performance. An aircraft flight control example is presented to show the capacity of such design in relaxing a practical design condition. Copyright © 2013 John Wiley & Sons, Ltd.     

Taguchi-factorial type-2 fuzzy random optimization model for planning conjunctive water management with compound uncertainties

In this study, a type-2 fuzzy random optimization (TFRO) method is developed for planning conjunctive water management system associated with compound uncertainties. TFRO can effectively address compound uncertainties expressed as type-2 fuzzy sets, probability distributions, and type-2 fuzzy random variables. Solution algorithm based on the degree of probability and the information of plausibility is proposed to transform nonlinear objective function and constraints into their linear equivalents. A real case of water-resources allocation problem in Zhangweinan River Basin (China) is employed to demonstrate the applicability of the proposed method. A Taguchi-factorial type-2 fuzzy random model is also formulated through introducing Taguchi design and ANOVA technique into the TFRO framework. Results obtained can help reveal the relationship among multiple impact factors of economic, environmental and resource (water conveyance efficiency, water delivery cost, and system violation risk), as well as quantify their contributions to the variability of system benefit and water allocation schemes.     

Reduced-order model based active disturbance rejection control of hydraulic servo system with singular value perturbation theory

Hydraulic servomechanism is the typical mechanical/hydraulic double-dynamics coupling system with the high stiffness control and mismatched uncertainties input problems, which hinder direct applications of many advanced control approaches in the hydraulic servo fields. In this paper, by introducing the singular value perturbation theory, the original double-dynamics coupling model of the hydraulic servomechanism was reduced to a integral chain system. So that, the popular ADRC (active disturbance rejection control) technology could be directly applied to the reduced system. In addition, the high stiffness control and mismatched uncertainties input problems are avoided. The validity of the simplified model is analyzed and proven theoretically. The standard linear ADRC algorithm is then developed based on the obtained reduced-order model. Extensive comparative co-simulations and experiments are carried out to illustrate the effectiveness of the proposed method.