文献翻译-适应性控制系统

适应性控制系统适应性控制系统是一种自动调整其参数以补偿过程特性的相应变化的系统。简而言之，该系统可以“适应”过程的需要。当然，必须有一些作为适应程序依据的原则。为被调量规定一个数值（即设定值）是不够的，因为要满足这一指标。不仅需要适应性控制。还必须另外规定被调量的某种“目标函数” 。这是一个决定需要何种特殊形式的适应性控制的函数。一个给定过程的目标函数可能是被调量的衰减度。因而，实质上有两个回路，一个回路靠被调量操作，另一个则依赖其衰减度。由于衰减度标志着回路动态增益，因此这种系统被称为动态适应性系统。也有可能为一个过程规定一个静态增益的目标函数。为这种指标而设计的控制系统就是静态适应性系统。实际上，这两种系统之间几乎不存在相似，以至它们在同一名称“适应性”之下，它们的分类已经引起了许多混淆。要指出的是，第二个区别并非是目标函数，而是关于如何实现适应性控制的机理问题。如果对于过程有充分的了解，使得参数的调整能够与那些引起过程性质变化的变量有关系，那么适应性控制就可以程序化了。然而，如果必须根据目标函数的测量值来调整参数，则要利用反馈回路实现适应性控制。这种系统称为自适应系统。可编程控制器20 世纪 60 年代，在控制器受到关注以前，电机装置一直是这个年代的流行产品。这些通常被称为继电器的装置被数以千记的系统用来控制许多制造过程和单独的机器。许多这样的继电器被应用于运输工业，更明确的说，应用于汽车工业。这些继电器使用成百上千的金属导线，他们的相互联系将影响控制的解决方案。至少作为一个单个的装置，继电器的性能是基本稳定的。但是，继电器盒通常需要安装三百甚至更多的继电器，于是可靠性及维修和保养问题就不可避免地摆到了我们面前。成本问题成为另一问题，尽管继电器成本很底；但是继电器盒的安装成本很高，每个继电器总的成本，其中包括购买零件、配线和安装工作的成本，大体在 30 美元到 50 美元之间不等。更糟糕的事情是，控制面板需要经常不断的更改。对于继电器来说，这是一个昂贵的事实。因为这一更改过程需要大量的劳动在控制面板上重新接线。此外，这些变化有时很少备有证明文件的。这就使以后的再次维护工作成为很头疼的事。按照这样考虑，丢弃整个旧的控制面板，同意使用一个适合的新的控制过程方式的相匹配的接线元件的控制面板，也是很常见的事情。这就给这些系统的维护成本增加了不可预知的、潜在的高成本。正如在昂贵的电动车生产线上一样。越来越清楚地认识到要使系统更可靠，更容易排除故障，更适合不断变化的控制过程需要，就必须改进控制过程。在 20 世纪 60 年代，出现了第一个可编程控制器。这是第一个“革命性”的系统，这个系统是按照美国汽车制造工业的特定要求开发研制出来的。这些早期的控制器，即可编程逻辑控制器（PLC）是能应用于工厂车间的最早系统。这些控制器再不需要大量重新接线或改变元件的情况下能够作“逻辑”变化，一旦出现问题，它能够很轻易地诊断和修补。观察可编程控制器在最近 15 年取得的进步是很有趣的事情，在 20 世纪 60 年代末期早期的产品或许会使很多人感到惊恐和迷惑不解，例如，维修人员习惯手动工具，那么对于电子仪器的部件和机电设备将会发生什么呢？改装过的计算机代替这些设备，正如电子器件代替继电器，甚至设计出了工具来作为继电器的替代品。我们现在有机会来审视一下前景，回顾过去，可编程控制器带给制造业的是什么？开关传感器 照明行程开关模拟量 电磁装置光电耦合 电机输入 输出 接触器可编程控制起都包含了基本的功能模块，为了理解控制系统的关系，我们将检查一下每一个模块。首先，我们看一下中心，它是系统的心脏。中心包括微处理器、存储当前控制逻辑的逻辑存储器、存储常变量数据的变量存储器，中西部分具有控制程序执行和为微处理器与存储器提供电力的功能。接着是 I/O模块，它的功能是为 CPU 提供控制水平信号，并把他们转化为适合连接工厂级别的传感器和调节器的标准电压和电流。I/O 类型可以是数字信号、模拟信号或是应用于某一定特定应用的“智能”I/O。程序员通常仅需编写程序，而不需要考虑程序在系统中的运行。他也可以用来发现并修理系统故障，在检查系统故障的确切原因发面是个很有用的设备。在这里提到的设备代表了与 I/O 连接的各种传感器和调节器，它门是系统的手臂、腿、眼睛和耳朵，其中包括按钮、输 入 端 口中央处理器（CPU）逻辑存储器变量存储器动力供应输 出 端 口编程设备限制开关、行程开关、光敏元件、热电偶、位置传感器，作为输入的读卡机、标灯、显示设备、发动机、DC 和 AD 驱动器、螺线管和作为输出的打印机。Adaptive Control SystemsAn adaptive control system is one whose parameters are automatically adjusted to compensate for corresponding variations in the properties of the process. The system is, in a word, “adapted” to the needs of the process. Naturally there must be some criteria on which to base an adaptive program. To specify a value for the controlled variable is not enough-adaption is not required to meet this specification. Some “objective function” of the controlled variable must be specified in addition. It is this function that determines the particular form of adaption required.The objective function for a given process may be the damping of the controlled variable. In essence, there are then two loops, one operating on the controlled variable, the other on its damping. Because damping identifies the dynamic loop gain, this system is designated as a dynamic adaptive system.It is also possible to stipulate an objective function of the steady-state gain of the process. A control system designed to this specification is then steady-state adaptive.There is, in practice, so little resemblance between these two systems that their classification under a single title “adaptive” has led to, much confusion.A second distinction is to be made, this not on the objective function, but rather on the mechanism through which adaption is introduced, if enough is known on a process that parameter adjustments can be related to the variables which cause its properties to change, adoption may be programmed. However, if it is necessary to base parameter means of a feedback loop. This is known as a self adaptive system.Programmable Logic ControllersIn the 1960s,electromechanical devices were the order of the day as far as control was concerned. These devices, commonly known as relays, were being used by the thousands to control many sequential-type manufacturing processes and stand-alone machines. Many of these relays were in use in the transportation industry, more specifically, the automotive industry. These relays used hundreds of wires and their interconnections to affect a control solution. The performance of a relay was basically reliable-at least as a single device. But the common applications for relay panels called for 300 to 500or more relays, and the reliability and maintenance issues associated with supporting these panels became a very great challenge. Cost became another issue, for in spite of the low cost of the relay itself, the installed cost of the panel could be quite high. The total cost including purchased parts, wiring, and installation labor, could range from 30 50 per relay. To make matters worse, the constantly changing needs of a process called for recurring modifications of a control panel. With relays, this was a costly prospect, as it was accomplished by a major rewiring effort on the panel. In addition, these changes were sometimes poorly documented, causing a second-shift maintenance nightmare months later. In light of this, it was not uncommon to discard an entire control panel in favor of a new one with the appropriate components wired in a manner suited for the new process. Add to this the unpredictable, and potentially high, cost of maintaining these systems as on high-volume motor vehicle production lines. And it became clear that something was needed to improve the control process-to make it more reliable, easier to troubleshoot, and more adaptable to changing control needs.That something, in the late 1960s, was the first programmable controller. This first ”revolutionary” system was developed as a specific response to the needs of the major automotive manufacturers in the United States. These early controllers, or Programmable Logic Controllers(PLC), represented the first systems that could be used on the factory floor, could have there “logic” change without extensive rewiring or component changes, and were easy to diagnose and repair when problems occurred. It is interesting to observe the progress that has been made in the past 15years in the programmable controller area. The pioneer products of the late 1960s must have been confusing and frightening to a great number of people. For example, what happened to the hardwired and electromechanical devices that maintenance personnel were used to repairing with hand tools ? They were replaced with “computers” disguised as electronics designed to replace relays. Even the programming tools were designed to appear as relay equivalent presentations. We have the opportunity now to examine the promise, in retrospect, what the programmable controller brought manufacturing ?开关传感器 照明行程开关模拟量 电磁装置光电耦合电机INPUT CENTER OUTPUT 接触器All programmable controllers consist of the basic functional blocks shown in Figure 10.1. We will examine each block to understand the relationship to the control system. First we looked at the center, as it is the heart of the system. It consists of a microprocessor, logic memory for the storage of the actual control logic, storage or variable memory for use with data that will ordinarily change as a function of the control program execution, and a power supply to provide electrical power for the processor and memory. Next comes the I/O bloke. This function takes the control level signals for the CPU and converts them to voltage and current levels suitable for connection with factory grade sensors and actuators. The I/O type can range from digital, analog, or a variety