一类G-M系统轮胎吊自动控制系统设计

本文结合某港口G-M系统轮胎吊的技术改造实例,在保持原有供电调速方案不变的基础上,采用PLC综合控制替代原有的继电器逻辑控制,以及数字式直流调速器替代原有的直流发电机励磁电流发生器,并利用两者之间的协调配合构成数字式调节器以替代原有的模拟式调节器。同时,就直流调速器控制方式的设置、运行机构预提力矩的控制和速度环积分分离PID闭环控制等几个与本系统自动化控制有关的核心问题进行了详细阐述。

应用Matlab分析PID控制器对G-M直流调速系统的影响

PID控制器是最早发展起来的控制策略之一,广泛应用于工业过程控制及运动控制中。Matlab软件的使用使得自动控制系统的分析与设计的视化程序设计更加方便。以控制系统中常用的PID控制器在G-M直流调速系统中的应用为对象,分析了其数学模型,借助Matlab软件分别分析了比例P、比例积分PI、比例积分微分PID控制器参数变化对系统中对稳定性、快速性及准确性的影响。

基于电枢电流模糊反馈原理的直流电机机组负荷均衡控制方法

以大功率G M系统为对象 ,提出了电枢电流模糊反馈和电机负荷均衡控制的问题。通过电动机组电枢电流检测量的模糊处理 ,对二台发电机励磁电压进行同步控制 ,实现了电机机组并联运行时电动机电流负载、转矩负载的均衡控制。该方法应用于起重机起升机构驱动系统 ,使机组上升时负荷差值ΔTs=(0 6～ 0 9) %TN,下降时负荷差值ΔTg=(1～ 3) %TN,稳态时不均衡负载波动率ULR下降了 70 %～ 80 %。

Single Server Queueing Models and Birth-Death Process

A transition diagram is used to describe the behavior of systems. Birth-death equations were derived from transition diagram depicting the state of the birth-death processes. Queue models and characteristics of queue models are also derivable from birth-death processes. These queue models consist of mathematical formulas and relationships that can be used to determine the operating characteristics （performance measures） for a waiting line. Schematic and transition diagrams of different single server queue models were shown. Relationships between birth-death processes, waiting lines （queues） and transition diagrams were given. While M/M/I/K queue model states was limited by K customers and had （K＋I） states, M/M/1/1 queue model had only two states. M/G/1/∝/∝ and M/M/1/∝/∝ shared similar characteristics. Many ideal queuing situations employ M/M/1 queueing model.

Time-dependent analysis for a queue modeled by an infinite system of partial differential equations

By studying the spectrum of the underlying operator corresponding to the exhaustive-service M/G/1 queueing model with single vacations we prove that the time-dependent solution of the model strongly converges to its steady-state solution.