基于电气阻尼-刚度控制的双馈风电机组轴系扭振抑制策略

针对现有扭振控制中,难以平衡抑振效果和响应速度的关系,以及高、低速轴的阻尼比变化速率不同导致整体阻尼比难以调节的问题,提出了一种双馈风电机组轴系扭振抑制策略。首先推导了机械扭转角与电磁转矩的传递函数,通过引入等效阻尼和刚度分析了高低速轴机电耦合阻尼比的差异。其次对电气刚度抑制轴系扭振的机理进行分析,根据阻尼和刚度的协调作用,提出基于电气阻尼-刚度控制的轴系扭振抑制策略,得到电气阻尼-刚度控制下的轴系阻尼比变化趋势。最后在搭建FAST-MATLAB/Simulink联合仿真双馈风电机组模块的基础上,引入湍流风与电网暂降激励,对所提策略的抑振效果进行仿真验证。结果表明,相较于传统的阻尼控制,所提策略能够充分发挥传动链的机电强耦合作用,在保证响应速度的同时具有更好的抑振能力。

高校共青团改革背景下高职学生就业服务体系构建研究

以习近平为代表的国家领导人关注青少年的发展和共青团的建设,带动共青团改革的全面深化。改革坚持用现先进的思想吸引青年,用整体的思维方法指导其行为,实现青少年群体主体利益的凸显和自我需求的满足。而高职院校在发展中致力于产学结合,结合共青团改革的内容,必须建立完整的学生就业服务体系,有重点且更全面地实现高职学生的就业。本文主要就高校共青团改革背景下的高职学生就业服务体系构建进行研究。

基于精英族系遗传算法的AUV集群路径规划

针对传统路径规划算法仅能规划单一最短路径且不能调节路径宽度而难以适用于自主式水下航行器(autonomous underwater vehicle,AUV)集群航路规划的缺陷,提出了精英族系遗传算法(elite family genetic algorithm,EFGA)。该算法将基因适应度加入适应度评价函数中,同时在进化过程中标记精英个体作为多路径规划结果,并在该算法基础上针对AUV集群路径规划问题设计了一种多智能体路径规划(multi-agent path planning,MAPP)方法。仿真结果表明,该算法可以求解无冲突路径集合实现MAPP,通过实现AUV集群的最优多路径航行方案减少集群的航行耗时,且能够满足不同AUV编队规模对可调路径宽度的需求。

极点极线背景试题的计算策略

以极点极线为背景的试题计算困难.本文总结了解决此类问题的五种计算策略:设线策略、设点策略、向量策略、几何策略、曲线系策略.其中设线策略中又分为同构方程策略、非对称式消元策略、非对称式对称化策略.

A Geometric Process Repair Model for the Repairable System Consisting of One Component

This paper considers the optimal replacement problem of a repairable system consisting of one component and a single repairman, assume that the system after repair is not 'as good as new', by using the geometric process, we consider a placement policy T based on the age of the system. The problem is to determine the optimal replacement policy T * such that the long_run expected benefit per unit time is maximized. Also, the explicit expression of the long_run expected benefit per unit time can be found. In some conditions, the existence and uniqueness of the optimal policy T * can be proved, finally, we prove that the policy T * is better than the policy T * in .

Optimal configuration of firewall, IDS and vulnerability scan by game theory

The integrated linkage control problem based on attack detection is solved with the analyses of the security model including firewall, intrusion detection system （IDS） and vulnerability scan by game theory. The Nash equilibrium for two portfolios of only deploying IDS and vulnerability scan and deploying all the technologies is investigated by backward induction. The results show that when the detection rates of IDS and vulnerability scan are low, the firm will not only inspect every user who raises an alarm, but also a fraction of users that do not raise an alarm; when the detection rates of IDS and vulnerability scan are sufficiently high, the firm will not inspect any user who does not raise an alarm, but only inspect a fraction of users that raise an alarm. Adding firewall into the information system impacts on the benefits of firms and hackers, but does not change the optimal strategies of hackers, and the optimal investigation strategies of IDS are only changed in certain cases. Moreover, the interactions between IDS ＆ vulnerability scan and firewall ＆ IDS are discussed in detail.

Research on a simulated 60 kW PEMFC cogeneration system for domestic application

The electrical and thermal performances of a simulated 60 kW Proton Exchange Membrane Fuel Cell (PEMFC) cogeneration system are first analyzed and then strategies to make the system operation stable and efficient are developed. The system configuration is described first, and then the power response and coordination strategy are presented on the basis of the electricity model. Two different thermal models are used to estimate the thermal performance of this cogeneration system, and heat management is discussed. Based on these system designs, the 60 kW PEMFC cogeneration system is analyzed in detail. The analysis results will be useful for further study and development of the system.

Disturbance decoupled fault diagnosis for sensor fault of maglev suspension system

A disturbance decoupled fault diagnosis strategy is proposed.This disturbance decoupled fault diagnosis is both robust to disturbances and sensitive to sensor faults of magnetic levitation control system.First,a robust controller based on a novel disturbance observer is devised to improve the disturbance attenuation ability,which greatly enhances the robustness of the system.Second,a fault reconstruction technique with adaptive method is presented,along with a strict verification for guaranteeing the robustness of fault.This fault reconstruction technique provides an accurate sensor fault reconstruction.From the results of simulation and experiments conducted on the CMS-04 maglev train,the integrated strategy is robust to model uncertainties of the system and the fault reconstruction algorithm is able to reconstruct the dynamic uncertain faults.

Application of generalized predictive control in networked control system

A new framework for networked control system based on Generalized Predictive Control (GPC) is proposed in this paper. Clock-driven sensors, event-driven controller, and clock-driven actuators are required in this framework. A queuing strategy is proposed to overcome the network induced delay. Without redesigning, the proposed framework enables the existing GPC controller to be used in a network environment. It also does not require clock synchronization and is only slightly affected by bad network condition such as package loss. Various experiments are designed over the real network to test the proposed approach, which verify that the proposed approach can stabilize the Networked Control System (NCS) and is robust.

Fuzzy robust path tracking strategy of an active pelagic trawl system with coordinated ship and winch regulation

A fuzzy robust path tracking strategy of an active pelagic trawl system with ship and winch regulation is proposed.First,nonlinear mathematic model of the pelagic trawl system was derived using Lagrange equation and further simplified as a low order model for the convenience of controller design.Then,an active path tracking strategy of pelagic trawl system was investigated to improve the catching efficiency of the target fish near the sea bottom.By means of the active tracking control,the pelagic trawl net can be positioned dynamically to follow a specified trajectory via the coordinated winch and ship regulation.In addition,considering the system nonlinearities,modeling uncertainties and the unknown exogenous disturbance of the trawl system model,a nonlinear robust H2 /H∞ controller based on Takagi-Sugeno(T-S) fuzzy model was presented,and the simulation comparison with linear robust H2 /H∞ controller and PID method was conducted for the validation of the nonlinear fuzzy robust controller.The nonlinear simulation results show that the average tracking error is 0.4 m for the fuzzy robust H2 /H∞ control and 125.8 m for the vertical and horizontal displacement,respectively,which is much smaller than linear H2 /H∞ controller and the PID controller.The investigation results illustrate that the fuzzy robust controller is effective for the active path tracking control of the pelagic trawl system.

A novel coordinated control strategy considering power smoothing for a hybrid photovoltaic/battery energy storage system

This work presents a novel coordinated control strategy of a hybrid photovoltaic/battery energy storage(PV/BES) system. Different controller operation modes are simulated considering normal, high fluctuation and emergency conditions. When the system is grid-connected, BES regulates the fluctuated power output which ensures smooth net injected power from the PV/BES system. In islanded operation, BES system is transferred to single master operation during which the frequency and voltage of the islanded microgrid are regulated at the desired level. PSCAD/EMTDC simulation validates the proposed method and obtained favorable results on power set-point tracking strategies with very small deviations of net output power compared to the power set-point. The state-of-charge regulation scheme also very effective with SOC has been regulated between 32% and 79% range.

Investment decision optimization for delayed product differentiation based on queuing theory

To balance inventory cost with diverse demand,an optimal investment decision on necessary process improvement for delayed product differentiation is studied. A two-stage flexible manufacturing system is modeled as a continuous time Markov chain. The first production stage manufactures semifinished products based on a make-to-stock policy. The second production stage customizes semi-finished products from the first production stage on a make-to-order policy. Various performance measures for this flexible manufacturing system are evaluated by using matrix geometric methods. An optimization model to determine the level of investment on process improvement that minimizes the manufacturer ’s total cost is established. The results show that,a higher investment level can reduce both the expected customer order fulfillment delay and the expected semi-finished products inventory. When the initial order penetration point is 0. 4,the manufacturer ’s total cost is reduced by 15. 89% through process investment. In addition, the optimal investment level increases with the increase in the unit time cost of customer order fulfillment delay,and decreases with the increase in the product value and the initial order penetration point.

Control strategy for an intelligent shearer height adjusting system

An intelligent shearer height adjusting system is a key technology for mining at a man-less working face. A control strategy for a shearer height adjusting system based on a mathematical model of the height adjusting mechanism is proposed. It considers the non-linearity and time variations in the control process and uses Dynamic Fuzzy Neural Networks （D-FNN）. The inverse characteristics of the system are studied. An adaptive on-line learning and error compensation mechanism guarantees sys- tem real-time performance and reliability. Parameters from a German Eickhoff SL500 shearer were used with Maflab/Simulink to simulate a height adjusting control system. Simulation shows that the trace error of a D-FNN controller is smaller than that of a PID controller. Also, the D-FNN control scheme has good generalization and tracking performance, which allow it to satisfy the needs of a shearer height adjusting system.

A new semi-active suspension control strategy through mixed H_2/H_∞ robust technique

A new semi-active suspension control strategy through mixed H2/H∞ robust technique was developed due to its flexibility and robustness to model uncertainties.A full car model with seven degrees of freedom was established to demonstrate the effectiveness of the new control approach.Magneto-rheological(MR) dampers were designed,manufactured and characterized as available semi-active actuators in the developed semi-active suspension system.The four independent mixed H2/H∞ controllers were devised in order to perform a distributed semi-active control system in the vehicle by which the response velocity and reliability can be improved significantly.The performance of the proposed new approach was investigated in time and frequency domains.A good balance between vehicle's comfort and road holding was achieved.An effective and practical control strategy for semi-active suspension system was thus obtained.This new approach exhibits some advantages in implementation,performance flexibility and robustness compared to existing methods.

Impact of social relationship on firms' sharing reward program

In order to make strategic decision on firms’ sharing reward program( SRP), a nested Stackelberg game is developed. The sharing behavior among users and the rewarding strategy of firms are modeled. The optimal sharing bonus is worked out and the impact of social relationships among customers is discussed. The results show that the higher the bonus,the more efforts the inductor is willing to make to persuade the inductee into buying. In addition,the firms should take the social relationship into consideration when setting the optimal sharing bonus. If the social relationship is weak,there is no need to adopt the SRP. Otherwise,there are two ways to reward the inductors. Also,the stronger the social relationship,the fewer the sharing bonuses that should be offered to the inductors,and the higher the expected profits. As a result,it is reasonable for the firms to implement SRPs on the social media where users are familiar with each other.

New code match strategy for wideband code division multiple access code tree management

Orthogonal variable spreading factor channelization codes are widely used to provide variable data rates for supporting different bandwidth requirements in wideband code division multiple access (WCDMA) systems. A new code match scheme for WCDMA code tree management was proposed. The code match scheme is similar to the existing crowed-first scheme. When choosing a code for a user, the code match scheme only compares the one up layer of the allocated codes, unlike the crowed-first scheme which perhaps compares all up layers. So the operation of code match scheme is simple, and the average time delay is decreased by 5.1%. The simulation results also show that the code match strategy can decrease the average code blocking probability by 8.4%.

Model-based trajectory tracking control for an electrohydraulic lifting system with valve compensation strategy

The natural frequency of the electrohydraulic system in mobile machinery is always very low,which brings difficulties to the controller design.To improve the tracking performance of the hydraulic system,mathematical modeling of the electrohydraulic lifting system and the rubber hose was accomplished according to an electrohydraulic lifting test rig built in the laboratory.Then,valve compensation strategy,including spool opening compensation (SOC) and dead zone compensation (DZC),was designed based on the flow-pressure characteristic of a closed-centered proportional valve.Comparative experiments on point-to-point trajectory tracking between a proportional controller with the proposed compensations and a traditional PI controller were conducted.Experiment results show that the maximal absolute values of the tracking error are reduced from 0.039 m to 0.019 m for the slow point-to-point motion trajectory and from 0.085 m to 0.054 m for the fast point-to-point motion trajectory with the proposed compensations.Moreover,tracking error of the proposed controller was analyzed and corresponding suggestions to reduce the tracking error were put forward.

Firm review revelation policy considering social ties among consumers

An optimization model is proposed to analyze the optimal review revelation policies and consumer online social network management strategies of e-commerce firms.The results show that displaying friend reviews to consumers does not necessarily increase firms profits.Only when positive reviews account for a large proportion of all the reviews and when the cost of showing friend reviews is not high,can showing friend reviews be more profitable than not showing such information.The distribution of social ties among consumers can affect firms profits.Even in the case that showing friend reviews to consumers is more profitable,an increase in the proportion of strong ties is not necessarily beneficial to firms.Only when the proportion of positive reviews is large enough,can firms profits increase with the increase in the proportion of strong ties among consumers.Moreover,the degree of consumer distrust in the average quality rating can also affect firms strategies for managing consumer online social networks.As the degree of consumer distrust in the average quality rating rises,firms are more likely to obtain higher profits by taking measures to increase the proportion of strong ties among consumers on their websites.

An adaptive ant colony system algorithm for continuous-space optimization problems

Ant colony algorithms comprise a novel category of evolutionary computation methods for optimization problems, especially for sequencing-type combinatorial optimization problems. An adaptive ant colony algorithm is proposed in this paper to tackle continuous-space optimization problems, using a new objective-function-based heuristic pheromone assignment approach for pheromone update to filtrate solution candidates.Global optimal solutions can be reached more rapidly by self-adjusting the path searching behaviors of the ants according to objective values. The performance of the proposed algorithm is compared with a basic ant colony algorithm and a Square Quadratic Programming approach in solving two benchmark problems with multiple extremes. The results indicated that the efficiency and reliability of the proposed algorithm were greatly improved.

Adaptive Optimal Control of Space Tether System for Payload Capture via Policy Iteration

The libration control problem of space tether system(STS)for post-capture of payload is studied.The process of payload capture will cause tether swing and deviation from the nominal position,resulting in the failure of capture mission.Due to unknown inertial parameters after capturing the payload,an adaptive optimal control based on policy iteration is developed to stabilize the uncertain dynamic system in the post-capture phase.By introducing integral reinforcement learning(IRL)scheme,the algebraic Riccati equation(ARE)can be online solved without known dynamics.To avoid computational burden from iteration equations,the online implementation of policy iteration algorithm is provided by the least-squares solution method.Finally,the effectiveness of the algorithm is validated by numerical simulations.