A Stroke-Limitation AMD Control System with Variable Gain and Limited Area for High-Rise Buildings

Collisions between a moving mass and an anti-collision device increase structural responses and threaten structural safety.An active mass damper(AMD)with stroke limitations is often used to avoid collisions.However,a strokelimited AMD control system with a fixed limited area shortens the available AMD stroke and leads to significant control power.To solve this problem,the design approach with variable gain and limited area(VGLA)is proposed in this study.First,the boundary of variable-limited areas is calculated based on the real-time status of the moving mass.The variable gain(VG)expression at the variable limited area is deduced by considering the saturation of AMD stroke.Then,numerical simulations of a stroke-limited AMD control system with VGLA are conducted on a high-rise building structure.These numerical simulations show that the proposed approach has superior strokelimitation performance compared with a stroke-limited AMD control system with a fixed limited area.Finally,the proposed approach is validated through experiments on a four-story steel frame.

A Multi-mode Electronic Load Sensing Control Scheme with Power Limitation and Pressure Cut-off for Mobile Machinery

In mobile machinery,hydro-mechanical pumps are increasingly replaced by electronically controlled pumps to improve the automation level,but diversified control functions(e.g.,power limitation and pressure cut-off)are integrated into the electronic controller only from the pump level,leading to the potential instability of the overall system.To solve this problem,a multi-mode electrohydraulic load sensing(MELS)control scheme is proposed especially considering the switching stability from the system level,which includes four working modes of flow control,load sensing,power limitation,and pressure control.Depending on the actual working requirements,the switching rules for the different modes and the switching direction(i.e.,the modes can be switched bilaterally or unilaterally)are defined.The priority of different modes is also defined,from high to low:pressure control,power limitation,load sensing,and flow control.When multiple switching rules are satisfied at the same time,the system switches to the control mode with the highest priority.In addition,the switching stability between flow control and pressure control modes is analyzed,and the controller parameters that guarantee the switching stability are obtained.A comparative study is carried out based on a test rig with a 2-ton hydraulic excavator.The results show that the MELS controller can achieve the control functions of proper flow supplement,power limitation,and pressure cut-off,which has good stability performance when switching between different control modes.This research proposes the MELS control method that realizes the stability of multi-mode switching of the hydraulic system of mobile machinery under different working conditions.

Effects of Oxygen Transfer Limitation and Kinetic Control on Biomimetic Catalytic Oxidation of Toluene

Under oxygen transfer limitation and kinetic control, liquid-phase catalytic oxidation of toluene over metalloporphyrin was studied. An improved technique of measuring dissolved oxygen levels for gas-liquid reaction at the elevated temperature and pressure was used to take the sequential data in the oxidation of toluene catalyzed by metalloporphyrin. By this technique the corresponding control step of toluene oxidation could be obtained by varying reaction conditions. When the partial pressure of oxygen in the feed is lower than or equal to 0.070 MPa at463 K, the oxidation of toluene would be controlled by oxygen transfer, otherwise the reaction would be controlled by kinetics. The effects of both oxygen transfer and kinetic control on the toluene conversion and the selectivity of benzaldehyde and benzyl alcohol in biomimetic catalytic oxidation of toluene were systematically investigated.Three conclusions have been made from the experimental results. Firstly, under the oxygen transfer limitation the toluene conversion is lower than that under kinetic control at the same oxidation conditions. Secondly, under the oxygen transfer limitation the total selectivity of benzaldehyde and benzyl alcohol is lower than that under kinetic control with the same conversion of toluene. Finally, under the kinetics control the oxidation rate of toluene is zero-order with respect to oxygen. The experimental results are identical with the biomimetic catalytic mechanism of toluene oxidation over metalloporphyrins.

Integrated design and control technology of liner completion and drilling for horizontal wells

Aiming at the problems of large load of rotation drive system,low efficiency of torque transmission and high cost for operation and maintenance of liner steering drilling system for the horizontal well,a new method of liner differential rotary drilling with double tubular strings in the horizontal well is proposed.The technical principle of this method is revealed,supporting tools such as the differential rotation transducer,composite rotary steering system and the hanger are designed,and technological process is optimized.A tool face control technique of steering drilling assembly is proposed and the calculation model of extension limit of liner differential rotary drilling with double tubular strings in horizontal well is established.These results show that the liner differential rotary drilling with double tubular strings is equipped with measurement while drilling(MWD)and positive displacement motor(PDM),and directional drilling of horizontal well is realized by adjusting rotary speed of drill pipe to control the tool face of PDM.Based on the engineering case of deep coalbed methane horizontal well in the eastern margin of Ordos Basin,the extension limit of horizontal drilling with double tubular strings is calculated.Compared with the conventional liner drilling method,the liner differential rotary drilling with double tubular strings increases the extension limit value of horizontal well significantly.The research findings provide useful reference for the integrated design and control of liner completion and drilling of horizontal wells.

Predictive Control Model Based on the MPC Algorithm on Three Different Road Sections

Predictive control is an advanced control algorithm,which is widely used in industrial process control.Among them,model predictive control(MPC)is an important branch of predictive control.Its basic principle is to use the system model to predict future behavior and determine the current control action by optimizing the objective function.This paper discusses the application of MPC in the prediction and control of the speed of vehicles to optimize traffic flow.It is a valuable reference for alleviating traffic congestion and improving travel efficiency and smoothness and provides scientific basis and technical support for future highway traffic management.

H_∞ Design for Sampled-Data Systems via Lifting Technique: Conditions and Limitation

The initial motivation of the lifting technique is to solve the H∞control problems. However, the conventional weighted H∞design does not meet the conditions required by lifting, so the result often leads to a misjudgement of the design. Two conditions required by using the lifting technique are presented based on the basic formulae of the lifting. It is pointed out that only the H∞disturbance attenuation problem with no weighting functions can meet these conditions, hence, the application of the lifting technique is quite limited.

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.

Amplitude control of limit cycle in a van der Pol Duffing system

This paper applies washout filter technology to amplitude control of limit cycles emerging from Hopf bifurcation of the van der Pol-Duffing system. The controlling parameters for the appearance of Hopf bifurcation are given by the Routh-Hurwitz criteria. Noticeably, numerical simulation indicates that the controllers control the amplitude of limit cycles not only of the weakly nonlinear van der Pol-Duffing system but also of the strongly nonlinear van der Pol-Duffing system. In particular, the emergence of Hopf bifurcation can be controlled by a suitable choice of controlling parameters. Gain-amplitude curves of controlled systems are also drawn.

H-infinity performance optimization for networked control systems with limited communication channels

This paper studies the problems of H-infinity performance optimization and controller design for continuous-time NCSs with both sensor-to-controller and controller-to-actuator communication constraints （limited communication channels）. By taking the derivative character of network-induced delay into full consideration and defining new Lyapunov functions, linear matrix inequalities （LMIs）-based H-infinity performance optimization and controller design are presented for NCSs with limited communication channels. If there do not exist any constraints on the communication channels, the proposed design methods are also applicable. The merit of the proposed methods lies in their Jess conservativeness, which is achieved by avoiding the utilization of bounding inequalities for cross products of vectors. The simulation results illustrate the merit and effectiveness of the proposed H-infinity controller design for NCSs with limited communication channels.

Analysis and design of over-current limit control strategies applied in aeronautical power supplies

Some Over-Current Limit Control strategies are analyzed and designed to meet the demands of high reliability and rapid dynamic response in the aeronautical power supply applications. The control schemes are both effective in DC-DC converters and DC-AC converters. Controller models are set up, and the over-current limit operation principles of analogy and digital control are analyzed too. An 800VA aeronautical power supply bas been constructed to verify the performance of the proposed control strategy in various cases such as the sudden load change and the constant load. The analysis and experiments confirm the advantages of the proposed over-current limit strategies as follows： simple,effective and reliable.

Quantum speed limit time of a two-level atom under different quantum feedback control

We investigate the quantum speed limit time （QSLT） of a two-level atom under quantum-jump-based feedback control or homodyne-based feedback control. Our results show that the two different feedback control schemes have different influences on the evolutionary speed. By adjusting the feedback parameters, the quantum-jump-based feedback control can induce speedup of the atomic evolution from an excited state, but the homodyne-based feedback control cannot change the evolutionary speed. Additionally, the QSLT for the whole dynamical process is explored. Under the quantum-jump-based feedback control, the QSLT displays oscillatory behaviors, which implies multiple speed-up and speed-down processes during the evolution. While, the homodyne-based feedback control can accelerate the speed-up process and improve the uniform speed in the uniform evolution process.

An Active Inrush Current Limiter Based on SCR Phase Shift Control for EV Charging Systems

This article gives an overview of the main passive solutions and active techniques, based on AC switches to limit inrush currents in medium power AC-DC converters （up to 3.7 kW） for electric vehicle charging systems. In particular, a strategy, based on SCR （silicon controlled rectifier） phase, shift control in a mixed rectifier bridge with diodes and thyristors, is proposed. The challenge is to help designers optimize the triggering delay of SCRs to both limit the peak value of inrush current spikes and optimize the charge duration of the DC-link capacitor. A mathematical model （Mathcad engineering tool） has been defined to point out, the interest of a variable triggering delay to control SCRs to meet the expectations described previously. Experimental measurements using an industrial evaluation board of the AC-DC converter demonstrate the robustness of the method.

Hybrid Operation of Fault Current Limiter and Thyristor Controlled Braking Resistor

The effectiveness of a combination of fault current limiter and thyristor controlled braking resistor on power system stability enhancement and damping turbine shaft torsional oscillations has been studied. If both devices operate at the same bus, the stabilization control scheme can be carried out continuously and with flexibility. As a result, the fault currents are limited, and the generator disturbances and the turbine shaft torsional oscillations are converged quickly. In this paper, the effectiveness of the combination of both devices has been demonstrated by considering 3LG （three-lines-to-ground） fault in a two-machine infinite bus system. Also, temperature rise effect of both devices with various resistance values and weights has been demonstrated. Simulation results indicate a significant power system stability enhancement and damping turbine shaft torsional oscillations as well as with allowable temperature rise.

PREDICTION AND CONTROL OF BOTH WRINKLE AND FRACTURE LIMITS ON CYLINDRICAL CUP MULTI DEEP DRAWING

Based on the superfluous triangle material wrinkle model,the no wrinkle limit criterion of cylindrical cup multi deep drawing is calculated as the prediction and control of the wrinkle limit.According to fracture model,the no fracture limit criterion of cylindrical cup multi deep drawing is calculated as the prediction and control of the fracture limit.Combining the no wrinkle limit criterion with the no fracture limit criterion,the no wrinkle and no fracture limit criterion and diagram on cylindrecal cup multi deep drawing are given as the prediction and control of both wrinkle and fracture limits.In accordance with this can determine the limit deep drawing coefficient and minimum deep drawing coefficient,and can choose the deep drawing coefficient of multi deep drawing,blank holder force and deformation force by optimization choice method.Theory calculation and test data are highly consistent,and suitable for no flange multi deep drawing,flange multi deep drawing and rigid punch expanding

Feedback control and quantum error correction assisted quantum multi-parameter estimation

Quantum metrology provides a fundamental limit on the precision of multi-parameter estimation,called the Heisenberg limit,which has been achieved in noiseless quantum systems.However,for systems subject to noises,it is hard to achieve this limit since noises are inclined to destroy quantum coherence and entanglement.In this paper,a combined control scheme with feedback and quantum error correction(QEC)is proposed to achieve the Heisenberg limit in the presence of spontaneous emission,where the feedback control is used to protect a stabilizer code space containing an optimal probe state and an additional control is applied to eliminate the measurement incompatibility among three parameters.Although an ancilla system is necessary for the preparation of the optimal probe state,our scheme does not require the ancilla system to be noiseless.In addition,the control scheme in this paper has a low-dimensional code space.For the three components of a magnetic field,it can achieve the highest estimation precision with only a 2-dimensional code space,while at least a4-dimensional code space is required in the common optimal error correction protocols.

Generation of Optimal Voltage Reference for Limit Cycle Oscillation in Digital Control-Based Switching Power Supply

Digital control of a general-purpose switching power supply is one of the key technologies to perform the high reliability and the intelligent function demanded for the next generation. The contribution of this paper is the development of a digital control-based switching power supply. In the developed system, the generation method of the optimal voltage reference to eliminate the limit cycle oscillation of output voltage due to the AD/DA resolution is proposed. In the proposed method, the variation of the input power source voltage can be also compensated. The effectiveness of the proposed optimal reference generation method is experimentally verified.

深层、超深层定向钻井中若干基础研究进展与展望

深层、超深层定向钻井具有“垂深大与水平延伸远”的双重特征,受到复杂地层、高温高压、超长裸眼等多重因素约束,其安全高效作业面临着更大的全方位技术挑战。为此,着眼于深层、超深层定向钻井的提速提效问题,系统总结了定向钻井的发展概况与技术特点,选取了深层、超深层定向钻井中力学方面的几个重要基础问题,分析了国内外专家学者的相关研究进展和最新研究成果,最后展望了深层、超深层定向钻井基础理论研究发展趋势并提出相关建议。研究结果表明:①大小偏差融合控制算法兼顾了井眼轨迹的控制精度、光滑度等多目标约束,适应于深层、超深层条件下井眼轨迹实时控制要求;②合理优化振动减阻工具个数、安放位置及其激励力幅值,可显著降低井下管柱摩阻,并有效提高机械钻速;③基于误差补偿机制的机械钻速融合预测模型既保留了机理模型的可解释性,又具有较高的预测精度;④套管复合磨损预测模型突破了经典“单月牙”模式的局限性,实现了复合模式下套管磨损形状与深度的同步预测。结论认为,深层、超深层定向井和水平井是未来油气井工程的重要发展方向之一,需要加强多因素耦合机理、钻井延伸极限、机理与数据融合驱动等方面的基础研究,以推动复杂油气井工程基础理论的创新与发展,为深层、超深层钻井工程技术进步提供必要的基础理论支撑。

虚拟同步机电流受限暂态电压支撑机理与改进故障穿越控制研究

针对虚拟同步机在电网低、过电压故障下所面临的无功电压支撑不足、特性差等问题,建立考虑电流限幅特性的虚拟同步机等效电路模型,并基于拓扑同伦原理,给出不同无功电压控制在等效电路相量图上的几何表征方法。利用该方法,揭示几种常见无功电压控制下的虚拟同步机电流受限暂态电压支撑机理,并由此提出一种改进的故障穿越控制策略,有效改善电网低电压、过电压故障下的暂态电压控制能力和支撑特性,进而缓解故障期间的暂态功角稳定问题。基于PSCAD/EMTDC仿真对所提机理和故障穿越控制方法进行详细验证,最后,在3机9节点系统中对其在近、远区电网故障下的支撑特性进行仿真验证。

自动驾驶汽车避撞极限研究

精确计算不同避撞控制策略的极限避撞距离是自动驾驶汽车避撞决策与控制的基础。为厘清差动制动控制对避撞距离的影响,探究转向和差动制动集成控制的极限避撞能力,提高极限避撞距离的计算精度,本研究基于非线性车辆集成动力学和最优控制理论提出一种自动驾驶汽车极限避撞距离计算方法。首先,建立了非线性7自由度车辆动力学模型和复合滑移工况的Pacejka轮胎模型。进一步地,基于上述模型构建了极限避撞距离求解问题,并将其转化为最优控制问题。然后,设计了高斯伪谱法将最优控制问题转化为非线性规划问题并求解。最后,分析了转向控制、制动控制、转向和制动集成控制、转向和差动制动集成控制的极限避撞距离,并与基于质点模型计算和CarSim测试的结果进行了对比。结果表明:转向和差动制动集成控制能够进一步减少自动驾驶汽车的避撞距离,显著提高其避撞能力;本研究所提方法能够显著提高极限避撞距离的计算精度和避撞决策结果的可靠性。

基于钳位型断路器的柔直系统控保协同技术

柔性直流系统以其在输电领域的巨大优势而获得广泛应用.但在直流系统中,短路故障的强冲击性与电力电子器件的脆弱性之间的矛盾异常尖锐,现有保护策略难以同时满足高速动性与高可靠性的要求.本文从控保协同思想出发,基于一种电压钳位原理的直流断路器,提出一种新的故障处理模式,初步探究在柔直系统中控制与保护深度融合的可能性.当发生短路故障时,投入断路器和换流器相配合的限流功能,一方面限制电力电子器件的过流,解决其脆弱性问题;另一方面为保护提供边界,辅助实现故障的快速定位.在甄别出故障线路后,利用断路器的故障切除功能将故障隔离.此方案同时实现了故障限流、保护边界和故障切除3项功能,可有效缓减由于模块化多电平换流器(modular multilevel converter,MMC)器件脆弱性所带来的一系列保护问题.在PSCAD/EMTDC中搭建四端双极柔性直流电网模型,仿真结果表明,本控保协同方案能在5 ms内准确识别并隔离故障线路,而且具有较强的耐受过渡电阻能力.