供应链环境下库存控制策略研究

库存控制与管理是现代企业生产经营管理过程中不可或缺的组成部分,也是供应链管理的主要活动之一。传统的库存管理仅将注意力放在对自身库存物资进行控制与管理上,但在供应链环境下,库存管理需将视野从自身扩大到整个供应链网络上来,相互协调共同管理库存,实现整个供应链库存的优化,达到供应链上各节点企业的共赢。     

Vessel motion control using rope tension control strategy

In this paper, the problem of designing a Position Mooring (PM) system for a barge ship is addressed. A mathematical model of a system comprising a barge ship and mooring system is derived. Hydrodynamic coefficients of the low speed model for PM ship are identified by suitable experiments. A PID control scheme is implemented to achieve PM for the vessel by changing the tension of the mooring ropes. The proposed strategy is finally tested on station keeping, and desired positions of a 1/50 scale model ship are obtained.     

自适应仿人智能控制控制策略研究

在分析自适应仿人智能控制结构的基础上,重点研究了多模态控制策略,充分利用系统误差、误差的变化、被控对象的输入量的变化和模型误差四个信息,并以被控对象的输入量的变化和模型误差作为仿人智能控制器和内模控制器之间的协调参数,使控制器的快速性、平稳性、鲁棒性和抗扰性得到极大改善。仿真试验证明在该控制结构下的控制策略非常有效。     

On Shortest Linear Recurrences

This is an expository account of a constructive theorem on the shortest linear recurrences of a finite sequence over an arbitrary integral domainR. A generalization of rational approximation, which we call “realization”, plays a key role throughout the paper.We also give the associated “minimal realization” algorithm, which has a simple control structure and is division-free. It is easy to show that the number ofR-multiplications required isO(n²), wherenis the length of the input sequence.Our approach is algebraic and independent of any particular application. We view a linear recurring sequence as a torsion element in a naturalR[X]-module. The standardR[X]-module of Laurent polynomials overRunderlies our approach to finite sequences. The prerequisites are nominal and we use short Fibonacci sequences as running examples.     

Bioreactor control using a probing feeding strategy and mid-ranging control

The paper presents a fed-batch fermentation technique for bioreactors operating close to their maximum oxygen transfer capacity. The method combines the advantages of the probing feeding strategy and the temperature limited fed-batch technique. When the maximum oxygen transfer capacity of the reactor is reached, the temperature is decreased to lower the oxygen demand. To achieve a good control of the dissolved oxygen a mid-ranging controller manipulating the stirrer speed and the temperature is used. The feeding strategy is analysed and it is also illustrated by simulations and an experiment.     

A scalable correlation aware aggregation strategy for wireless sensor networks

Sensors-to-sink data in wireless sensor networks (WSNs) are typically characterized by correlation along the spatial, semantic, and/or temporal dimensions. Exploiting such correlation when performing data aggregation can result in considerable improvements in the bandwidth and energy performance of WSNs. In this paper, we first identify that most of the existing upstream routing approaches in WSNs can be translated to a correlation-unaware data aggregation structure – the shortest-path tree. Although by using a shortest-path tree, some implicit benefits due to correlation are possible, we show that explicitly constructing a correlation-aware structure can result in considerable performance improvement. Toward this end, we present a simple, scalable and distributed correlation-aware aggregation structure that addresses the practical challenges in the context of aggregation in WSNs. Through simulations and analysis, we evaluate the performance of the proposed approach with centralized and distributed correlation-aware and -unaware structures.     

Shortest Path Geometric Rounding

Exact implementations of algorithms of computational geometry are subject to exponential growth in running time and space. In particular, coordinate bit-complexity can grow exponentially when algorithms are cascaded : the output of one algorithm becomes the input to the next. Cascading is a significant problem in practice. We propose a geometric rounding technique: shortest path rounding . Shortest path rounding trades accuracy for space and time and eliminates the exponential cost introduced by cascading. It can be applied to all algorithms which operate on planar polygonal regions, for example, set operations, transformations, convex hull, triangulation, and Minkowski sum. Unlike other geometric rounding techniques, shortest path rounding can round vertices to arbitrary lattices, even in polar coordinates, as long as the rounding cells are connected. (Other rounding techniques can only round to the integer grid.) On the integer grid, shortest path rounding introduces less combinatorial change and geometric error than the other rounding methods. Three algorithms are given for shortest path rounding, one of which we have used in industrial application software since 1992. In combination with recent advances in exact floating point evaluation of numerical primitives, shortest path geometric rounding yields a practical solution to numerical issues in computational geometry. Geometric algorithms can be implemented exactly on floating point input coordinates; the exact output coordinates can be rounded to accurate floating point approximations; and the cost of each arithmetic operation is only a little more than if it were implemented as a single hardware floating point operation. Received February 7, 1997; revised September 9, 1998.     

Nonlinear control strategy development for asymmetric actuators

We develop a nonlinear control method for asymmetric actuators. Asymmetric actuators do not generate symmetric power during an application. Thrusters and shape memory alloy wires are examples of this class of actuators that produce only unidirectional forces. Hydraulic and pneumatic cylinders are generally asymmetric because, under constant pressure, the generated force in the forward direction is different than that in the reverse direction. Existing control methods assume a symmetric actuation, and therefore, application of asymmetric actuators calls for new control schemes. Current control techniques implement a bias in utilizing asymmetric actuators. However, the amount of the bias depends on the control effort and is not constant. Also, the use of a bias changes the system equilibrium point and introduces a steady-state error. We propose a control scheme capable of producing any biased input. The controller is a second-order system coupled to the system through quadratic terms. The application of quadratic terms for the control input enables us to generate any biased control input, which can be utilized by asymmetric actuators     

On-line optimization for a flow control strategy

We consider the problem of optimizing a threshold-dependent flow control strategy by using state information available on-line. It is assumed that a sample realization of a queueing system using this strategy is available, for which the threshold parameter is fixed. In contrast to earlier work, perturbation analysis in this case requires tracking queue lengths in addition to event times, in order to obtain performance sensitivity estimates. In this note we formally derive perturbation equations and describe their algorithmic implementation, which requires partial state memory in the form of arrival time information. Because this may impose serious storage limitations (unless the arrival process is deterministic), a capacity constraint is imposed. The effect of this constraint on our approach is finally investigated and experimental results are included.     

A new control strategy for IKN-type coolers

This paper presents a new system for the optimized control of IKN-type cement coolers based on adaptive predictive methodology. The new system introduces the concepts of ’layer on grate’ and ’thickness of slope’, which allow a decoupled multivariable control of the layer of clinker over the grate, and the flow rate of the cooler fans, solving a fundamental control problem for this type of process and maximizing the heat transfer from the cooling process to the kiln. The experimental results obtained in the Gador mill of Holcim, in Almeria (Spain), are analyzed.     

A cyclic switching strategy for parameter-adaptive control

This paper introduces a new strategy, called “cyclic switching,” to deal with the well-known certainty equivalence control synthesis problem which arises in the design of identifier-based adaptive controllers because of the existence of points in parameter space where the design model Σ_D, upon which certainty equivalence synthesis is based, loses stabilizability. Unlike most previously suggested methods for handling this problem, the technique proposed here can be employed with or without process excitation. For the technique to work it is not necessary for there to be a mechanism for moving tuned parameters away from values at which Σ_D loses stabilizability, and no such mechanism is used     

An adaptive control strategy for mechanical manipulators

This paper focuses on the study of an adaptive perturbation control which tracks a desired time-based trajectory as close as possible for all times over a wide range of manipulator motion and payloads. The proposed adaptive control is based on the linearized perturbation equations in the vicinity of a nominal trajectory. The controlled system is characterized by feedforward and feedback components which can be computed separately and simultaneously. The feedforward component computes the nominal torques from the Newton-Euler equations of motion to compensate all the interaction forces among the various joints. The feedback component consisting of recursive least-square identification and an optimal adaptive self-tuning control algorithm for the linearized system computes the perturbation torques which reduce the position and velocity errors of the manipulator along the nominal trajectory. A computer simulation study was conducted to evaluate the performance of the proposed adaptive control.     

Active steering control strategy for articulated vehicles

To improve maneuverability and stability of articulated vehicles, we design an active steering controller, including tractor and trailer controllers, based on linear quadratic regulator (LQR) theory. First, a three-degree-of-freedom (3-DOF) model of the tractor-trailer with steered trailer axles is built. The simulated annealing particle swarm optimization (SAPSO) algorithm is applied to identify the key parameters of the model under specified vehicle speed and steering wheel angle. Thus, the key parameters of the simplified model can be obtained according to the vehicle conditions using an online look-up table and interpolation. Simulation results show that vehicle parameter outputs of the simplified model and TruckSim agree well, thus providing the ideal reference yaw rate for the controller. Then the active steering controller of the tractor and trailer based on LQR is designed to follow the desired yaw rate and minimize their side-slip angle of the center of gravity (CG) at the same time. Finally, simulation tests at both low speed and high speed are conducted based on the TruckSim-Simulink program. The results show significant effects on the active steering controller on improving maneuverability at low speed and lateral stability at high speed for the articulated vehicle. The control strategy is applicable for steering not only along gentle curves but also along sharp curves.     

模块化多电平逆变器预充电控制策略

针对矿井提升机运行特点,采用由模块化多电平整流器和模块化多电平逆变器构成的背靠背模块化多电平变流器用于矿井提升机控制;针对目前通过直流侧对模块化多电平逆变器进行预充电的控制研究较少的问题,提出了一种模块化多电平逆变器预充电控制策略。该控制策略通过控制充电电流来控制子模块充电状态,使子模块电容充电至模块化多电平变流器稳定运行时的电压要求,同时将充电电流和充电过程中产生的过电压限定在安全范围内,使充电时间最短。仿真结果验证了该控制策略的有效性。     

楼字供水系统控制策略研究

以变频调速和多泵技术为核心,对变压变流量供水系统进行了设计。根据楼宇供水系统的特性,分析了变压变流量供水的优点。建立了控制系统仿真模型,设计了逻辑控制器与过程控制器以满足多泵控制系统不同需要。提出了两种最新的模糊PID控制器,能明显改善供水系统的控制性能,并给出了仿真的结果。     

An intelligent control strategy for computer consultation

Expert consultant systems often perform computations on a directed graph of associated propositions. Each proposition is represented by a node. Edges connecting these nodes are associated with rules which organize the propositions into antecedent/consequent relationships. A node may be assigned a value through the edges that bind it to its antecedents. Various strategies are employed to determine assignment sequences that result in efficient computer consultation. One such strategy, the merit system, has been successfully implemented in Battle, an expert consultant system for the Marine Corps. The merit strategy enables Battle to focus the consultation process on the most appropriate questions. The merit system, originally defined for logical functions in the Multiple program, has been extended to the Mycin style of propagation and to the method of subjective Bayesian assignments used by Prospector. A procedure for merit calculations with any differentiable, real-valued assignment function is presented. Our experience has shown that merit values provide an efficient flow of control for expert consultation.     

RPN tuning strategy for model predictive control

A novel tuning strategy based on RPN for MIMO MPC is presented. The RPN indicates how potentially difficult it is for a given system to achieve the desired performance robustly. It reflects both the attainable performance of a system and its degree of directionality. These system's properties are the basis of the proposed RPN-MPC tuning strategy, which is applied in the controller design of an air separation plant and a CSTR with the Van de Vusse's reaction. Although it was only used a linear nominal model, the results can also be applied at least at some extent for nonlinear systems with uncertainties.     

三能级原子系统中量子态相干保持的控制策略

研究光与物质的相互作用并利用其性质设计新型的量子器件,以实现光信息存储及其消相干抑制.分析了以单色激光场为控制场的A型三能级原子系统的主方程模型,借助于无消相干子空间的构造方法,通过改变耦合激光场Rabi频率的方式,设计了实现系统中量子态相干保持的控制策略.