复杂过程的最佳操作点是在若干约束条件下的。DMCplus多变量控制软件提供一套工具以允许存在一些约束的情况下控制强耦合多变量系统。在适当情况下,相关的DMCplus工具在任务后的括号中列出。
当过程单元被确定为DMCplus的潜在应用后,控制器的实施需要经过以下项目控制步骤:
制定控制器初步设计方案
进行初步工厂测试或预测试(使用Advanced Control Collect)
进行工厂测试(使用Advanced Control Collect)
辨识过程模型(使用DMCplus Model)
制定稳态变动成本
建立控制器配置文件(CCF),并进行离线仿真/Tuning(使用DMCplus Build and Simulate)
配置在线控制器(使用DMCplus Manage and View)
委托在线控制
举办正规操作培训
维护DMCplus控制器
在Step 1之前,您需要安装或升级现有的DMCplus软件,以及其它任何相关软件(如数据库系统)。详情请参见相应的安装说明。
每个步骤都将在下面的章节中讨论。
Step 1:制定控制器初步设计方案
在对流程应用DMCplus时,控制工程师必须对流程非常熟悉。在控制器初步设计步骤,控制工程师需要审查流程图纸,会见操作和技术人员,并制定控制器初步设计方案。
同时你需要安装或升级现有的DMCplus软件,以及其它任何相关软件(如数据库系统)。
Step 2:进行初步工厂测试(预测试)
在初步工厂测试时,控制工程师需要花费数天时间在控制室检查仪表和管理控制系统是否正常运转。任何有故障的transmitters、粘滞阀等都将被修复并对数据采集系统进行测试。这两个步骤为控制工程师更好地熟悉流程提供了机会。
您可以使用Aspen Advanced Control Collect帮助收集并提取工厂初步测试数据。请参阅Advanced Control Collect Help了解详细信息。
Step 3:进行工厂测试
当仪表故障得到修复并且对管理控制器的性能进行了评估和改进,就可以开始工厂测试。对每个自变量执行一系列阶跃移动(扰动),并采集动作后的流程数据。
测试时间可能持续几天到几周不等。在持续的测试时间里,控制工程人员在控制室里与操作员一起全天候工作。
工厂测试是整个控制项目中最关键的一步。如果测试得到正确的执行,所得到的过程模型将是准确的。有了准确的模型,花在调试控制器的时间将大大减少,并保证了长期成功投用控制器。
然而,如果测试未正确执行,调试将无法顺利进行,十有八九将重新进行测试。
您可以使用Aspen Advanced Control Collect帮助收集和提取工厂测试数据。请参阅Advanced Control Collect Help了解详细信息。
Step 4:辨识过程模型
在下一步中,使用采集到的工厂测试流程数据进行模型辨识。工厂测试收集的流程数据被移到PC环境下,用于DMCplus Model使用。
您将使用DMCplus Model软件检查和分析数据,然后构建过程模型。请参阅DMCplus Model Help了解详细信息。
Step 5:制定稳态变动成本
另一重要的步骤是制定稳态变动成本。这些成本信息是稳态求解器选择最佳操作点背后的驱动力。计算这些成本需要提供各种产品和公用工程流股较自变量的稳态增益。
如果存在过程离线稳态模型,该模型可用于计算这些稳态增益。如果没有离线模型,这些增益可以通过产品及公用工程流股DMCplus分析得到。
成本计算还需要计算公用工程和产品流股价值成本。当公用工程成本或产品价值发生改变时,明智的做法是使用电子表格或相关方案推动这些计算更新以实现稳态变动成本。
您可能需要使用电子表格程序来记录这些数据,以便在DMCplus仿真调整控制器时使用(第6步)。
Step 6:建立控制器配置文件(CCF),并进行离线仿真/Tuning
下一步涉及到使用过程模型构建一个控制器配置文件(CCF)。你运用DMCplus Build构建CCF,然后使用DMCplus Simulate进行控制器离线仿真和Tuning。
DMCplus Build可使用预定义模板(可通过简单的自定义构建)让你快速创建一个CCF。当你创建了CCF,可以使用Simulate测试关键tuning参数,如Move Suppression因子(MV参数)和同样受人关注的Ranking错误或限制参数(CV参数)。
你可以使用Simulate测试DV变化、CV的设定值、稳态可变成本、MV和CV约束等。在评估控制器性能后,你可以根据提供的需求性能进行修改调整。然后存储包含新值的CCF文件。
CCF及其相关联的模型文件准备好后,开始下一步:在线配置。
请参阅DMCplus Build Help和DMCplus Simulate Help了解详细信息。
Step 7:配置在线控制器
下一步是配置在线控制器。这一任务的详细过程是连接特定的过程控制计算机、过程基础控制数据以及集散控制系统(DCS)从而连接需要控制的过程。
这一步包括配置合适的数据库标签,搭建操作员和工程师显示界面,并通过连接数据库标签将控制器配置文件(CCF)载入实际控制器。
方案应对过程控制数据库进行适当的数据读写测试。控制器的正确执行需要很好的验证。
附原文:
The optimum operating point for a complex process is atseveral constraints.The DMCplus Multivariable Control Software provides a set of tools to allow control of highly interactive multivariable systems at several constraints simultaneously. Where appropriate,the relevant DMCplus tool is listed after the task in parentheses.
Once a process unit is identified as a potential DMCplus application, the following control project steps are required to implement the controller:
Formulate a preliminary controller design.
Conduct the preliminary plant test, or pretest (using Advanced Control Collect).
Conduct the plant test (also using Collect).
Identify a process model (using DMCplus Model).
Develop steady-state variable costs.
Build the Controller Configuration File (CCF) and perform off-line simulation/tuning (using DMCplus Build and Simulate).
Configure the online controller (using DMCplus Manage and View).
Commission the online controller.
Hold formal operator training.
Maintain the DMCplus controller.
During Step 1, you should also install or upgrade your existing DMCplus software, along with any other relevant software (such as a database system). Refer to the appropriate installation instructions for details.
Each of these steps is discussed in the following sections.
Step 1: Formulate a preliminary controller design
In applying DMCplus to a process, the control engineer must become very familiar with that process. In the preliminary controller
design step, the control engineer reviews drawings of the process,meets with operations and technical personnel, and formulates a preliminary controller design.
You should install or upgrade your DMCplus software at thispoint, along with any other relevant software (such as a database).
Step 2: Conduct the preliminary planttest (pre-test)
In the preliminary plant test, the control engineer spends several days in the control room checking for proper functioning of instrumentation and regulatory controls.Any faulty transmitters, sticking valves, and so on are repaired and thedata collection system is tested. Both of these steps provide opportunities forthe control engineer to gain greater familiarity with the process.
You can use Aspen Advanced Control Collect to help collect andextract preliminary plant test data.Refer to the Advanced Control Collect Help for details.
Step 3: Conduct the plant test
Once faulty instrumentation has been repaired and regulatory controller performance has been evaluated and improved, the plant test can be performed. This is done by performing a series of step moves(perturbations) in each independent variable and collecting the process dataduring these moves.
The test lasts anywhere from a few days to a several weeks.Control engineering personnel work with the operators in the control room around the clock for the duration of the test.
This plant test is absolutely the MOST CRITICAL step in a control project. If the test is performed correctly, the resulting process models will be accurate. With accurate models, the time spent commissioning the controller will be greatly reduced, assuring the long term success of the controller.
If, however, the test is not done correctly, the commissioning will not proceed smoothly, and in all likelihood, the test will have to be repeated.
You can use Aspen Advanced Control Collect to help collect andextract plant test data. Refer to the Advanced Control Collect Help for details.
Step 4: Identify a process model
In the next step,model identification is performed using the process data recorded in the plant test. Data collected during the plant test is moved to a PC environment, for use with DMCplus Model.
You will use the DMCplus Model software to inspect and analyze the data, then build the process model. Refer to the DMCplus Model Help for details.
Step 5: Develop Steady-State Variable Costs
Another vital step is to develop the steady-state variable costs.These costs are the driving force behind the Steady-Statesolver’s choice of the optimum operating point. Calculation of these costs requires that the steady-state gains for various product and utility flows against the independent variables be provided.
If an off-line steady-state model of the process exists, this model can be used to calculate these steady-state gains. If there is no off-line model, these gains can be obtained from DMCplus analysis on the product and utility flows.
Also required in the cost calculation are the costs of utilitiesand product stream values. It is advisable to implement the steady-state variable costs using a spread sheet or related program to facilitate the update of these calculations when utility costs or product values change.
You may want to use a spreadsheet program to record this data,which can then be used in DMCplus Simulate when performing controller tuning(Step 6).
Step 6: Build a Controller Configuration File (CCF) and perform off-line controller simulation/tuning
The next step involves building a Controller Configuration file (or CCF) using the process model. You build the CCF using DMCplus Build, then performing off-line simulation and tuning of the controller using DMCplus Simulate.
Build allows you to quickly create a CCF, using pre-defined templates that you can easily customize.Onceyou have created a CCF, you can use Simulate to test key tuning parameters suchas Move Suppression Factors (for manipulated variables) and Equal ConcernErrors or Limit Ranking (for controlled variables).
Using Simulate, you can test changes in disturbance variables,CV setpoints, steady-state variable costs, MV and CV limits, etc. After evaluating the controller performance, you can make tuning changes to provide the desired performance. You then store the CCF with its new values.
The CCF and its associated model file are then ready for the next step, online configuration.
Refer to the DMCplus Build Help and DMCplus Simulate Help for details.
Step 7: Configure the online controller
The next step is to configure the online controller.The details of this task are specific to the type of process control computer,process control data base, and Distributed Control System (DCS) that are connected to the process which will be controlled.
This step involves building the appropriate database tags,building operator and engineer displays, and loading the controller configuration file (CCF) to connect the database tags to the actual controller.
The program should be tested for proper data transfer to and from the process control database. Proper execution of the controller should be verified as well.
2015.9.14