基于新修正偶应力理论的Reddy型层合板的热稳定性分析

基于新修正偶应力理论,对微尺度下Reddy层合板进行了热稳定性分析。模型只含有一个材料尺度参数,便于工程应用。通过虚功原理推导出了控制方程和边界条件,以四边简支方板为例,应用纳维叶解法得到解析解。结果表明:考虑热载荷作用下的失稳临界载荷大于经典理论下的结果。随着材料尺度参数的增加,临界温度升高,尺度效应增强,捕捉到了尺度效应;当跨厚比增大时,临界温度下降,尺度效应减弱;温度变化量越大,尺度效应越明显;尺度效应会随着板几何参数的增大而逐渐消失,模型将退化为宏观模型。

Design of decentralized robust H_∞ state feedback controller

The design of decentralized robust H_∞ state feedback controller for large-scale interconnected systems with value bounded uncertainties existing in the state, control input and interconnected matrices was investigated. Based on the bounded real lemma a sufficient condition for the existence of a decentralized robust H_∞ state feedback controller was derived. This condition is expressed as the feasibility problem of a certain nonlinear matrix inequality. The controller, which makes the closed-loop large-scale system robust stable and satisfies the given H_∞ performance, is obtained by the offered homotopy iterative linear matrix inequality method. A numerical example is given to demonstrate the effectiveness of the proposed method.

Trajectory tracking control for underactuated unmanned surface vehicles with dynamic uncertainties

The trajectory tracking control problem for underactuated unmanned surface vehicles(USV) was addressed, and the control system took account of the uncertain influences induced by model perturbation, external disturbance, etc. By introducing the reference, trajectory was generated by a virtual USV, and the error equation of trajectory tracking for USV was obtained, which transformed the tracking problem of underactuated USV into the stabilization problem of the trajectory tracking error equation. A backstepping adaptive sliding mode controller was proposed based on backstepping technology and method of dynamic slide model control. By means of theoretical analysis, it is proved that the proposed controller ensures that the solutions of closed loop system have the ultimate boundedness property. Simulation results are presented to illustrate the effectiveness of the proposed controller.

Numerical simulation of steady flow past a liquid sphere immersed in simple shear flow at low and moderate Re

This work presents a numerical investigation on steady internal, external and surface flows of a liquid sphere immersed in a simple shear flow at low and intermediate Reynolds numbers. The control volume formulation is adopted to solve the governing equations of two-phase flow in a 3-D spherical coordinate system. Numerical results show that the streamlines for Re = 0 are closed Jeffery orbits on the surface of the liquid sphere, and also closed curves outside and inside the liquid sphere. However, the streamlines have intricate and non-closed structures for Re ≠ 0. The flow structure is dependent on the values of Reynolds number and interior-to-exterior viscosity ratio.

Multi-domain modeling and simulation of proportional solenoid valve

A multi-domain nonlinear dynamic model of a proportional solenoid valve was presented.The electro-magnetic,mechanical and fluid subsystems of the valve were investigated,including their interactions.Governing equations of the valve were derived in the form of nonlinear state equations.By comparing the simulated and measured data,the simulation model is validated with a deviation less than 15%,which can be used for the structural design and control algorithm optimization of proportional solenoid valves.

Assessment of Model Predictive Control Performance Criteria

The current highly competitive environment has driven industries to operate with increasingly restricted profit margins. Thus, it is imperative to optimize production processes. Faced with this scenario, multivariable predictive control of processes has been presented as a powerful alternative to achieve these goals. Moreover, the rationale for implementation of advanced control and subsequent analysis of its post-match performance also focus on the benefits that this tool brings to the plant. It is therefore essential to establish a methodology for analysis, based on clear and measurable criteria. Currently, there are different methodologies available in the market to assist with such analysis. These tools can have a quantitative or qualitative focus. The aim of this study is to evaluate three of the best current main performance assessment technologies： Minimum Variance Control-Harris Index; Statistical Process Control （Cp and Cpk）; and the Qin and Yu Index. These indexes were studied for an alumina plant controlled by three MPC （model predictive control） algorithms （GPC （generalized predictive control）, RMPCT （robust multivariable predictive control technology） and ESSMPC （extended state space model predictive controller）） with different results.

Impulsive orbit control for spacecraft around asteroid

An impulse feedback control law to change the mean orbit elements of spacecraft around asteroid is presented. First, the mean orbit elements are transferred to the osculating orbit elements at the burning time. Then, the feedback control law based on Gauss’s perturbation equations of motion is given. And the impulse control for targeting from the higher circulation orbit to the specified periapsis is developed. Finally, the numerical simulation is performed and the simulation results show that the presented impulse control law is effective.

Bending analysis and control of rolled plate during snake hot rolling

In order to study the bending behavior of aluminum alloy 7050 thick plate during snake hot rolling, several coupled thermo-mechanical finite element(FE) models were established. Effects of different initial thicknesses, pass reductions, speed ratios and offset distances on the bending value of the plate were analyzed. ‘Quasi smooth plate' and optimum offset distance were defined and quasi smooth plate could be acquired by adjusting offset distance, and then bending control equation was fitted. The results show that bending value of the plate as well as the extent of the increase grows with the increase of pass reduction and decrease of initial thickness; the bending value firstly increases and then keeps steady with the ascending speed ratio; the bending value can be reduced by enlarging the offset distance. The optimum offset distance varies for different rolling parameters and it is augmented with the increase of pass reduction and speed ratio and the decrease of initial thickness. A proper offset distance for different rolling parameters can be calculated by the bending control equation and this equation can be a guidance to acquire a quasi smooth plate. The FEM results agree well with experimental results.

Research and Application of Construction Project Cost Control in Engineering Bidding Stage

In order to strengthen cost control in construction project bidding stage, this paper takes the price control in bidding stage as the main line, dedicated to determine the key point in the stage of cost control, and establishes the more objective and reasonable evaluation in view of the comprehensive evaluation method, and combined with the practical application of engineering to demonstrate. This paper not only improved the tendering and bidding stage method of cost control in construction project in our country, and improves the method system of engineering cost control.

From phenomena of synchronization to exact synchronization and approximate synchronization for hyperbolic systems

In this survey paper, the synchronization will be initially studied for infinite dimensional dynamical systems of partial differential equations instead of finite dimensional systems of ordinary differential equations,and will be connected with the control theory via boundary controls in a finite time interval. More precisely,various kinds of exact boundary synchronization and approximate boundary synchronization will be introduced and realized by means of fewer boundary controls for a coupled system of wave equations with Dirichlet boundary controls. Moreover, as necessary conditions for various kinds of approximate boundary synchronization, criteria of Kalman's type are obtained. Finally, some prospects will be given.

RAPID EXACT CONTROLLABILITY OF THE WAVE EQUATION BY CONTROLS DISTRIBUTED ON A TIME-VARIANT SUBDOMAIN

Consider the wave equation with distributed controls supported on a subdomain, calledcontrol subdomain, which is allowed to be variant in time. For any prescribed time duration,the authors work out a scheme for changing the control subdomain such that the wave equationis exactly controllable on this time duration, where the control subdomain at any time is allowedto have arbitrarily small measure and relatively simple shape.

Orbit control strategy for Lagrange point orbits based on an analytical method

The periodic or quasi-periodic orbits around collinear Lagrange points present many properties that are advantageous for space missions. These Lagrange point orbits are exponentially unstable. On the basis of an analytical method, an orbit control strategy that is designed to eliminate the dominant unstable components of Lagrange point orbits is developed. The proposed strategy enables the derivation of the analytical expression of nonlinear control force. The control parameter of this strategy can be arbitrarily selected provided that the parameter is considerably lower than the negative eigenvalue of motion equations, and that the energy required keeps the same order of magnitude. The periodic or quasi-periodic orbit of controlled equations remains near the periodic or quasi-periodic orbit of uncontrolled equations.

SOLVXBILITY OF FORWARD－BACKWARD SDES AND THE NODAL SET OF HAMILTON－JACOBI－BELLMAN EQUATIONS

The solvability of a class of forward-backward stochastic differential differential equations(SDEs for short)over an arbitrarily prescribed time duration is studied. The authors design a stochastic relaxed control problem, with both drift and diffusion all being controlled, so that the solvability problem is converted to a problem of finding the nodal set of the viscosity solution to a certain Hamilton-Jacobi-Bellman equation.This method overcomes the fatal difficulty encountered in the traditional contraction mapping approach to the existence theorem of such SDEs.

VARIATIONAL DISCRETIZATION FOR PARABOLIC OPTIMAL CONTROL PROBLEMS WITH CONTROL CONSTRAINTS

This paper studies variational discretization for the optimal control problem governed by parabolic equations with control constraints. First of all, the authors derive a priori error estimates where｜｜｜u - Uh｜｜｜L∞（J;L2（Ω）） = O（h2 ＋ k）. It is much better than a priori error estimates of standard finite element and backward Euler method where ｜｜｜u- Uh｜｜｜L∞（J;L2（Ω）） = O（h ＋ k）. Secondly, the authors obtain a posteriori error estimates of residual type. Finally, the authors present some numerical algorithms for the optimal control problem and do some numerical experiments to illustrate their theoretical results.

THE MAXIMUM PRINCIPLE FOR PARTIALLY OBSERVED OPTIMAL CONTROL OF FORWARD-BACKWARD STOCHASTIC SYSTEMS WITH RANDOM JUMPS

This paper studies the problem of partially observed optimal control for forward-backward stochastic systems which are driven both by Brownian motions and an independent Poisson random measure. Combining forward-backward stochastic differential equation theory with certain classical convex variational techniques, the necessary maximum principle is proved for the partially observed optimal control, where the control domain is a nonempty convex set. Under certain convexity assumptions, the author also gives the sufficient conditions of an optimal control for the aforementioned optimal optimal problem. To illustrate the theoretical result, the author also works out an example of partial information linear-quadratic optimal control, and finds an explicit expression of the corresponding optimal control by applying the necessary and sufficient maximum principle.

RAPID EXACT CONTROLLABILITY OFTHE SEMILINEAR WAVE EQUATION

In this paper the semilinear wave equation with homogeneous Dirichlet boundary condition having a locally distributed controller is considered, and the rapid exact controllability of this system is obtained by changing the shape and/or the location of the controller under proper conditions. For this purpose, the author derives an (rapid) observability inequality for wave equations with linear time-variant potential by means of the energy estimate. The main difference of the method from the previous ones is that any unique continuation property of the corresponding linear time-variant wave equations is not needed.

Three-dimensional Numerical Simulation of the Movement of the Flexible Body under Different Constraints

For the large deformation of the flexible body may cause the fluid grid distortion,which will make the numerical calculation tedious,even to end,the numerical simulation of the flexible body coupling with the fluid is always a tough problem.In this paper,the flexible body is under two kinds of constrained conditions and the ratio of length-diameter is 1:30.The Reynolds number of the airflow is 513,belonging to the area of low Reynolds number.The control equations of the coupling of flexible body with airflow are built and the adaptive grid control method is adopted to conduct the three-dimensional numerical simulation of the movement of the flexible body.The numerical results show that it is possible to simulate the characteristics of the flexible body's movement in the low Reynolds number airflow when the appropriate control equations are modeled and suitable equation-solving method is adopted.Unconstrained flexible body would turn over forward along the airflow's diffusion direction,while constrained flexible body in the flow field will make periodic rotation motion along the axis of the flexible body,and the bending deformation is more obvious than that of unconstrained flexible body.The preliminary three-dimensional numerical simulation can provide references for further research on the characteristics of the yam movement in high Reynolds number airflow.

The Effects of Redundant Control Inputs in Finite-Time Optimal Control

This paper is concerned with the effects of redundant control inputs on the quadratic optimal performance index in finite-time optimal control.Actually,the effects of redundant control input on quadratic performance index is equal to study the effects of the redundant control input on the solution of Riccati differential equation(RDE).Hence,some sufficient conditions are presented to strictly decrease the solution of RDE with the column of input matrix increased.Especially,a necessary and sufficient condition is derived to strictly decrease the solution of the homogeneous RDE after control input extensions.Moreover,one sufficient condition is obtained,which guarantees that the minimum control energy index strictly decreases with input extension.It is shown that redundant control inputs can improve the system performance based on these results.Some examples are taken to illustrate the effectiveness of related problems.