DGN液压加载控制器的闭环动态控制特性分析

DGN液压加载控制器是用于岩土工程测试的仪器。文章首先介绍DGN液压加载控制器的原理,然后对DGN液压加载控制器闭环动态控制特性进行了的分析。推导出应力控制时的线性动态系统(恒压输出控制系统)的相关传递函数和伯德图。最后,通过实验对理论分析进行了验证。

Characteristic of Intelligent Air Bag Venting Structure Actuating by Electrostrictive Stack Actuator

In this paper the conception of smart materials and structures is firstly combined with research of air bag,and the main theory of self adapting cushioning of intelligent air bag is expatiated.The intelligent venting structure is the main part affecting the cushioning result.Electrostrictive material was found having big force,high response speed and wide linearity,and it is fit to utilize in intelligent venting structure. The characteristic of the dynamic response and cushioning actuating of an electrostrictive stack actuator is analyzed,and the result of the computer simulation of the fuzzy control to intelligent venting structure is given.It is concluded that intelligent venting structure has good actuating characteristic and can satisfy the need of intelligent air bag.

Dynamic characteristics of hydraulic power steering system with accumulator in load-haul-dump vehicle

Using hydraulic power steering system of model EIMCO 922 load-haul-dump vehicle as a simulation example, the dynamic characteristics of hydraulic power steering system in load-haul-dump vehicle were simulated and discussed with SIMULINK software and hydraulic control theory. The results show that the dynamic characteristics of hydraulic power steering system are improved obviously by using bladder accumulator, the hydraulic power steering system of model EIMCO 922 load-haul-dump vehicle generates vibration at the initial stage under the normal steering condition of pulse input, and its static response time is 0.25 s shorter than that without bladder accumulator. Under the normal steering working condition, the capacity of steering accumulator for absorbing pulse is directly proportional to the cross section area of connecting pipeline, and inversely proportional to the length of connecting pipeline. At the same time, the precharge pressure of nitrogen in steering accumulator should be 60%80% of the rated minimum working pressure of hydraulic power steering system. Under the abnormal steering working condition, the steering cylinder piston may obtain higher motion velocity, and the dynamic response velocity of hydraulic power steering system can be increased by reducing the pressure drop of hydraulic pipelines between the accumulator and steering cylinder and by increasing the rated pressure of hydraulic power steering system, but the dynamic characteristics of hydraulic power steering system in load-haul-dump vehicle have nothing to do with the precharge pressure of nitrogen in steering accumulator.

Dynamic characteristics of cold rolling mill and strip based on flatness and thickness control in rolling process

The dynamic model of cold rolling mill based on strip flatness and thickness integrated control was proposed,containing the following sub-models:the rolling process model,the dynamic model of rolls along axial direction,and the compensation model.Based on the rule of volume flow rate,the dynamic rolling process model was built.The work roll and backup roll were taken as elastic continuous bodies,the effect of shear and moment of inertia were taken into consideration,and then the dynamic model of rolls was built.The two models were coupled together,and the dynamic model of rolling mill was built.In the dynamic model,the thermal expansion of the rolls,the wear of the rolls and other related parameters can not be considered.In order to compensate the dynamic model,the coupled static model of rolls and strip was applied.Then,according to the inner relationship of these models,the dynamic model and the compensation model were coupled,and the dynamic model of rolling mill based on the strip flatness and thickness integrated control was built.The dynamic simulation of the rolling process was made,and the dynamic thickness and the dynamic flatness information were obtained.This model not only provides a theory basis for the virtual rolling,but also provides a platform for the application of advanced control theory.

A wideband CMOS variable gain low noise amplifier

In this paper, a novel structure of linear-in-dB gain control is introduced. Based on this structure, a wideband variable gain low noise amplifier （VGLNA） has been designed and implemented in 0.18μm RF CMOS technology. The measured resuhs show a good linear-in-dB gain control characteristic with 15 dB dynamic range. It can operate in the frequency range of MHz and consumes 30mW from 1.8V power supply. The minimum noise figure is 4.1 dB at the 48 - 860 maximum gain and the input P1dB is greater than - 16.5dBm.

Multi-model Predictive Control of Ultra-supercritical Coal-fired Power Unit

The control of ultra-supercritical(USC) power unit is a difficult issue for its characteristic of the nonlinearity, large dead time and coupling of the unit. In this paper, model predictive control(MPC) based on multi-model and double layered optimization is introduced for coordinated control of USC unit. The linear programming(LP) combined with quadratic programming(QP) is used in steady optimization for computation of the ideal value of dynamic optimization. Three inputs(i.e. valve opening, coal flow and feedwater flow) are employed to control three outputs(i.e. load, main steam temperature and main steam pressure). The step response models for the dynamic matrix control(DMC) are constructed using the three inputs and the three outputs. Piecewise models are built at selected operation points. Double-layered multi-model predictive controller is implemented in simulation with satisfactory performance.

Optimal energy-efficient power control for cognitive radio based on static and dynamic features of primary users

In this paper, the energy-efficient power control problem in cognitive radio （CR） networks is studied not only to provide energy-efficient transmission, but also to guarantee the normal operation of primary users （PUs）. Moreover, the static energy-efficient power control （SEPC） algorithm is proposed in static scenario to maximize the capacity of secondary users （SUs） and to reduce the power consumption according to the interference from PU to SU. Furthermore, based on the analysis of PU＇s dynamic feature with Markov chain and SEPC algorithm,the dynamic energy-efficient power control （DEPC） algorithm is proposed taking into account the probability of detection and false alarm caused by sensing errors. Extensive simulation results show that the performance of the proposed algorithms is significantly improved compared with the existing algorithm.

Cavity flow regime for spillway aerators

It is well known that the effect of air entrainment for cavitation damage controls is related not only to the air discharge into aerator devices but also the flow regime of the cavity below them.On the basis of the hydraulic characteristics of the flow,the aerator devices were for the first time classified.The theoretical considerations were performed about the jet length and cavity flow regime with the influencing factors.Comparing with the behavior of the flow through the aerator of discharge tunnels,the flow regimes of the cavity below spillway aerators were experimentally investigated,and the empirical expressions were presented to identify the conversions of the cavity flow regimes,including fully filled cavity,partially filled cavity,and net air cavity.Some issues of the design of the aerator devices were suggested in the present work.

Development and application of a neural network based coating weight control system for a hot-dip galvanizing line

The hot-dip galvanizing line(HDGL) is a typical order-driven discrete-event process in steelmaking. It has some complicated dynamic characteristics such as a large time-varying delay, strong nonlinearity, and unmeasured disturbance, all of which lead to the difficulty of an online coating weight controller design. We propose a novel neural network based control system to solve these problems. The proposed method has been successfully applied to a real production line at Va Lin LY Steel Co., Loudi, China. The industrial application results show the effectiveness and efficiency of the proposed method, including significant reductions in the variance of the coating weight and the transition time.