宇宙飞行器相遇问题中最大控制距离的研究

以相遇误差为判定准则来解算出飞行器的最大飞行时间,从而求出最大控制距离方程,并给出了在特定条件下相遇误差与最大控制距离的变化关系曲线。根据仿真结果可以看出以相遇误差作为评定最大控制距离的标准是合理的。

最大控制律的多面体不变集鲁棒模型预测控制

为实现线性变参数系统的快速稳定控制,提出一种最大控制律的多面体不变集鲁棒模型预测控制算法。离线时,通过设定一组渐近趋向于稳定点的给定值,按照状态变量到稳定点距离大致相同的原则,构建一系列状态变量值集合,通过优化得到每个集合中较大的控制律,然后采用反推的方式优化得到一系列最大的控制律,并结合系统的输入输出约束得到离线多面体不变集。在线时,根据每个采样周期状态变量在多面体不变集中的位置,通过线性插值优化得到系统的实际控制律。给出离线在线算法的详细步骤和系统的闭环稳定性证明。通过仿真比较验证所提算法的有效性,表明所提算法使系统响应更为快速和稳定。

近距离星间相对姿轨耦合动力学建模与控制

针对在轨服务过程中近距离星间相对位置以及相对姿态精确控制的问题,考虑相对姿态与相对轨道之间的耦合作用,建立星间相对姿轨耦合动力学模型.提出编队星相对基准星进行接近绕飞的任务需求,给出相对姿态以及相对轨道的期望状态.设计相对姿态轨道联合控制算法对相对姿态和轨道进行联合控制.仿真结果表明,所设计的控制算法能够很好地抑制相对姿态与相对轨道的相互影响作用,最终实现编队星对基准星的精确指向绕飞运动.

电动汽车用IPMSM矢量控制策略研究

针对电动汽车用内置式永磁同步电机(IPMSM)采取不同矢量控制策略时优化效果不同现状,首先进行了电动车用IPMSM数学模型以及不同矢量控制策略的原理阐述和研究。在仿真平台上分别采用id=0控制策略、转矩/电流比最大控制策略(MTPA)和弱磁控制策略进行IPMSM矢量控制系统仿真模型的搭建,仿真结果表明,不同控制策略具有不同特点,得出基速以下IPMSM采用MTPA比采用id=0控制策略具有更优效果,基速以上采用弱磁控制控制策略能够拓宽IPMSM的转速范围的结论。

Optimal Control for Age Distribution and Weighted Size Competitive Species in a Polluted Environment

In the paper,we study an optimal control for a system representing a competitive species model with fertility and mortality depending on a weighted size in a polluted environment.A fixed point theorem is applied to obtain the existence and uniqueness exhibited by a non-negative solution of above mentioned model.A maximum principle helps to carefully verify the existence of the optimal control policy,and tangent-normal cone techniques help to obtain the optimal condition specific to control issue.

Metro passenger flow control with station-to-station cooperation based on stop-skipping and boarding limiting

Metro passenger flow control problem is studied under given total inbound demand in this work,which considers passenger demand control and train capacity supply.Relevant connotations are analyzed and a mathematical model is developed.The decision variables are boarding limiting and stop-skipping strategies and the objective is the maximal passenger profit.And a passenger original station choice model based on utility theory is built to modify the inbound passenger distribution among stations.Algorithm of metro passenger flow control scheme is designed,where two key technologies of stopping-station choice and headway adjustment are given and boarding limiting and train stopping-station scheme are optimized.Finally,a real case of Beijing metro is taken for example to verify validity.The results show that in the three scenarios with different ratios of normal trains to stop-skipping trains,the total limited passenger volume is the smallest and the systematic profit is the largest in scenario 3.

Controller design based on viscoelasticity dynamics model and experiment for flexible drive unit

In order to ensure that the system has the advantage of light weight and vibration absorption, the steel rope is used as a flexible transmission part. A flexible drive unit(FDU) is developed, whose features are guided by steel rope, increasing force by the movable pulley group, modular, convenient and flexible. Dynamics model for controller is deduced based on the constitutive equation of viscoelasticity. Controller is designed for position control and is based on the viscoelasticity dynamics model compensation control strategy proposed. The control system is based on the TURBO PMAC multi-axis motion control card.Prototype loading experiments and velocity experiments results show that the FDU can reach 2 Hz with no load and the max speed of 30(°)/s. The FDU has the capability of the load torque 11.2 N·m and the speed of 24(°)/s simultaneously, and the frequency response is 1.3 Hz. The FDU can be used to be the pitch joint of hip for biped robot whose walking speed is 0.144 km/h theoretically.

Adaptive robust output force tracking control of pneumatic cylinder while maximizing/minimizing its stiffness

The system considered in this work consists of a cylinder which is controlled by a pair of three-way servo valves rather than a four-way one.Therefore,the cylinder output stiffness is independently controllable of the output force.A discontinuous projection based adaptive robust controller (ARC) was constructed to achieve high-accuracy output force trajectory tracking for the system.In ARC,on-line parameter adaptation method was adopted to reduce the extent of parametric uncertainties due to the variation of friction parameters,and sliding mode control method was utilized to attenuate the effects of parameter estimation errors,unmodelled dynamics and disturbance.Furthermore,output stiffness maximization/minimization was introduced to fulfill the requirement of many robotic applications.Extensive experimental results were presented to illustrate the effectiveness and the achievable performance of the proposed scheme.For tracking a 0.5 Hz sinusoidal trajectory,maximum tracking error is 4.1 N and average tracking error is 2.2 N.Meanwhile,the output stiffness can be made and maintained near its maximum/minimum.

Performance enhancement of IMC-PID controller design for stable and unstable second-order time delay processes

An IMC-PID controller was proposed for unstable second-order time delay system which shows the characteristics of inverse response(RHP zero). A plot of Ms versus λ was suggested to calculate the suitable tuning parameter λ, which provides a trade-off between performance and robustness. Six different forms of process models were selected from literature to show the applicability of the present method. Performance of controller was calculated by ITAE and total variation TV and compared with recently published tuning rules. Undesirable overshoot was removed by using a set-point weighting parameter. Robustness was tested by introducing a perturbation into the various model parameters and closed-loop results show that the designed controller is robust in the case of model uncertainty. The proposed method shows an overall better closed-loop response as compared to other recently reported methods.

Arterial traffic signal coordination model considering buses and social vehicles

Considering the difference in driving parameters of buses and social vehicles on the arterial,an arterial traffic signal coordination model that takes into account social vehicles and buses on the basis of the maximum bandwidth is proposed.By using the pre-set parameters of a common cycle,green/red duration and known parameters of bus dwell time distribution,link length and vehicle speed and solving the mixed-integer-linear programming and optimizing the signal offsets,the model obtains the signal control parameters of the green bands both of social vehicles and buses.Finally,taking Wangjiang Road in Hefei as an example,simulation and evaluation are carried out by VISSIM.The results show that the new model has 15.2%and 13.2%reduction in average person delay and number of stops,respectively,compared with the traditional coordinated control method.

Despreader for Direct Sequence Spread Spectrum System and Its Performance Analysis

A new type of despreader for direct sequence spread spectrum signal is proposed. Compared with traditional despreaders, the new despreader does not contain hard decision ware or handle binary sequence any more, and the locally stored spread spectrum signals are pre-modulated baseband signals (such as Gaussian minimum shift keying (GMSK) signals), which are much more similar to the received spread spectrum signals. Moreover, the missed detection probability of the despreader is about one order of magnitude lower than that of traditional ones. Based on the maximum likelihood criterion and phase probability density function of demodulated signal, a new method of ana- lyzing the despreaders’ performance is put forward, which is proved to be more accurate than traditional methods according to the numerical results. Finally, an adaptive despreader under different signal-to-noise ratios is given.

Chaotic Control of Network Traffic

This paper presents a chaotic control method on network traffic. By this method, the chaotic network traffic can be controlled to pre-assigned equifibrium point according to chaotic prediction and the Largest Lyapunov Exponent （LLE） of the traffic on congested link is reduced, thereby the probability of traffic burst and network congestion can be reduced. Numerical examples show that this method is effective.

High Efficiency PCS with Scan-Type MPPT Control for a Grid-Connected PV Power Generation System

For a standalone PV （photovoltaic） power generation system, the author previously proposed a new MPPT （maximum power point tracking） control method in which the I-V characteristics are scanned with a detection interval control that operates at specified intervals and monitors the maximum power point. The author has obtained satisfactory results using this new MPPT control method. This paper investigates the application of the new MPPT control method for a PCS （power conditioning system） in a grid-connected type PV power generation system. The experimental results clearly demonstrate that the developed PCS offers outstanding effectiveness in tracking the maximum power point in partially shaded environments.

A Fuzzy Logic Controller for Maximum Power Point Tracking with 8-Bit Microcontroller

This paper presents the implementation of maximum power point tracking （MPPT） with fuzzy logic controller. For cost consideration, an inexpensive 8-bit microcontroller, PIC 16F877A, is selected and programmed with C language and integer variables For evaluation, the implemented fuzzy logic controller （FLC） is compared with the MPPT controller of using perturbation and observation （P＆O）. Both types of MPPT controllers are tested on the same voltage source with a series-connected resistor. Experimental results show that the implemented FLC with appropriate design meets the control requirements of MPPT. The FLC based on linguistic fuzzy rules has more flexibility and intelligence than conventional P＆O controller, but the FLC spends more RAM and ROM spaces than the P＆O tracker does.

Relevance of the P ＆ O MPPT Technique in an Original PV-Powered Water Pumping Application

Many papers exploiting the various MPPT （maximum power point tracking） techniques in PV （photovoltaic） applications, from the simple to the most complicated, can be found in literature. However, these techniques may not always be easy to implement in industrial applications. The main challenge of this paper is to model and implement the P ＆ O （perturb and observe） algorithm in a low-cost PV-powered pumping system. To that end, a comparative investigation of the performance characteristics of the most popular MPPT methods, such as FOCV （fractional open circuit voltage）, FSCC （fractional short circuit current）, FLC （fuzzy logic control）, ANN （artificial neural network） and INC （incremental conductance） is presented. This analysis is helpful to highlight the relevance of the P ＆ O technique taking better account of complexity, difficulty of implementation and cost considerations in water pumping applications. The targeted PV-powered pumping system is based on a single-phase induction motor supplied by a three-phase inverter controlled by the DTC （direct torque control） technique. This stand-alone PV system is dedicated to water pumping, especially in rural areas that have no access to national grids but have sufficient amount of solar radiation. Simulation modeling （Matlab/Simulink） and experimental results are presented to demonstrate the relevance of the system.

Analysis and Control of a Three-Phase Switched Reluctance Wind Generator

This paper deals with various aspects of modeling, simulation, analysis, and control ofa SRG （switched reluctance generator） in different modes of operation. Excitation method of such a generator is shortly described. The output power of the SRG is controlled so that it can track the maximum output power of a wind turbine drive applications. Also, the output generator voltage is stabilized under either load or wind speed variations. Basic operational characteristics of a three-phase 6/4 SRG are developed through experimental observation. Meanwhile, the real-time operation was implemented in a DSP （digital signal processor） environment. The simulation of the complete system model has been obtained using the Matlab/Simulink software. A good agreement between experimental and simulation results has been observed which supports the validity of the proposed analysis.

PKPM连梁在不同输入方法下计算结果分析与对比

在目前使用比较普遍的多高层空间有限元结构分析软件PKPM-SATWE中,连梁的建模方法可以采用按框架梁输入和按剪力墙开洞方式输入,在两种输入方式情况下,连梁内力计算结果有所不同。经过计算分析对比可知,按剪力墙开洞模拟连梁,其受力结果更接近工程实际受力状态;在剪力墙开洞输入方式下,不同墙元细分最大控制长度对计算结果的影响不可忽略;墙元细分控制长度取值越小,计算越精确,但计算所需时间也会越长。

Stochastic Maximum Principle for Optimal Control Problems of Forward-Backward Delay Systems Involving Impulse Controls

This paper is concerned with the optimal control problems of forward-backward delay systems involving impulse controls. The authors establish a stochastic maximum principle for this kind of systems. The most distinguishing features of the proposed problem are that the control variables consist of regular and impulsive controls, both with time delay, and that the domain of regular control is not necessarily convex. The authors obtain the necessary and sufficient conditions for optimal controls,which have potential applications in mathematical finance.

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.

STOCHASTIC MAXIMUM PRINCIPLE FOR MIXED REGULAR-SINGULAR CONTROL PROBLEMS OF FORWARD-BACKWARD SYSTEMS

This paper considers a stochastic optimal control problem of a forward-backward system with regular-singular controls where the set of regular controls is not necessarily convex and the regular control enters the diffusion coefficient.This control problem is difficult to solve with the classical method of spike variation.The authors use the approach of relaxed controls to establish maximum principle for this stochastic optimal control problem.Sufficient optimality conditions are also investigated.