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vensim

中文介绍:

Vensim是由美国Ventana Systems, Inc.所开发，为一可观

念化、文件化、模拟、分析、与最佳化动态系统模型之图形接口

软件。Vensim可提供一种简易而具有弹性的方式，以建立包括因

果循环(casual loop)、存货(stock)与流程图等相关模型。

使用Vensim建立动态模型，我们只要用图形化的各式箭头记

号连接各式变量记号，并将各变量之间的关系以适当方式写入模

型，各变量之间的因果关系便随之记录完成。而各变量、参数间

之数量关系以方程式功能写入模型。透过建立模型的过程，我们

可以了解变量间的因果关系与回路，并可透过程序中的特殊功能

了解各变量的输入与输出间的关系，便于使用者了解模型架构，

也便于模型建立者修改模型的内容。

英文介绍:

Version 5.7 is now available. This adds Unchangeable

Constants, considerable performance improvements during o

ptimization and a new VECTOR SELECT function that simp

lifies subscript relationship management.

Version 5.6b is now available. This version adds in the

capability to apply the Graph, Strip Graph, Table, Sensitivi

ty Graph, Stats and Document tool to multiple variable sele

ctions making it easier to look at a collection of variables t

ogether.

Version 5.6a is now available. This version supports U

nicode and increases the functionality of the Vensim Model

Reader to be able to open Venapps and Vensim DLL bas

ed applications. PLE Plus also supports hiding in this relea

se.

Version 5.5d of Vensim is now available making it sim

pler to share your models with others and to control the w

ay others can access your work. The new package publicat

ion feature allows you to send everything needed to run a

model in a single file making sure the people you send it t

o see what you see. It also allows you to mark models so

that they can’t be changed by the people receiving them.

In addition there are a number of smaller changes, new fu

nctions and problem corrections. See the readme notes for

more details.

Version 5.4 - Vensim PLE now supports input output o

bjects and allows you to override behavior in SyntheSim. T

hese changes are aimed at making PLE more effective an

all teaching environments.

Vensim 5.3a is now available for downloading. A numb

er of small improvements have been made to 5.3 which in

cluded new navigation capabilities, more hide levels with la

yered simulation, better pasting and improved performance

with nonstandard character sets.

We have also increased the functionality of Vensim PL

E to support the creation of models with multiple views an

d make use of data.

VensimPLE即Vensim系统动力学模拟环境个人学习版，是

Vensim软件的一种，是为了更便于学习系统动力学而设计的。V

ensimPLE主要有以下几个特点:

①利用图示化编程建立模型。Vensim的用户界面是标准的W

indows应用程序界面，除支持菜单和快捷键外，还提供多个工具

条或图标，这使用户使用非常方便。在Vensim中，“编辑”实际上

并不存在，只有建模的概念。只要在启动VensimPLE系统后得到

的主窗口中，依据操作按钮(画图工具)画出简化流率基本流图，再

通过Equation Editor输入方程和参数，就可以直接进行模拟了。

在Vensim中，方程及变量不带时标，模型建立是围绕着变量间的

因果关系展开。

②对模型提供多种分析方法。VENSIM所提供的分析工具可

以分为两类:一类是结构分析工具，如cause tree功能可以将所有

工作变量之间的因果关系用树状的图形形式表示出来;loops功能

可以将模型中所有反馈环以列表的形式表示出来。另一类是数据

集分析工具，如graph功能可以将各变量在整个模拟周期内的数

值以图形的形式直观的给出，causes strip graph功能则将有直接

因果关系的工作变量在模拟周期内的数值变化并列出来，一以追

踪系统变量间的影响关系。

Vensim V5.4a 系统动力学_系统思考软件 下载及基础教程

Posted in 极客分享 on 四月 15th, 2008 by 00 – 13 Comments

下载地址列表

Box | Rayfile | 纳米盘

软件介绍

Vensim是由美国Ventana Systems, Inc.所开发，为一可观念化、文

件化、模拟、分析、与最佳化动态系统模型之图形接口软件。Vensim

可提供一种简易而具有弹性的方式，以建立包括因果循环(casual

loop)、存货(stock)与流程图等相关模型。

使用Vensim建立动态模型，我们只要用图形化的各式箭头记号连接

各式变量记号，并将各变量之间的关系以适当方式写入模型，各变量

之间的因果关系便随之记录完成。而各变量、参数间之数量关系以方

程式功能写入模型。透过建立模型的过程，我们可以了解变量间的因

果关系与回路，并可透过程序中的特殊功能了解各变量的输入与输出

间的关系，便于使用者了解模型架构，也便于模型建立者修改模型的

内容。

如何画出自己的系统分析图？

先让我们熟悉一下界面

1、输入变量

2、加入箭头

单击一个变量，拖动到所流向的变量，拖动箭头中间的小圆圈可以改

变箭头的弧度

3、因果关系正负号的表示

右击箭头，出现箭头选项如下图：Polarity选择类型，

择放置在箭头处还是线上，在环内还是环外。

4、正负反馈符号的表示

选择Sketch comment工具

Position选

在Graphics处选择符号，或在Comment处输入字母，在

择顺时针或逆时针

5、加入delay符号

右击箭头，选中Delay mark前的复选框

6、删除变量或其他要素

点击删除工具，对要删除的要素单击

这样最简单的系统分析图就画好了~

当然这是最初步的应用，进一步的功能还在探索中。

Shape处选

系统动力学应用于社会经济复杂动态问题建模模拟，以及系统思考。

近年来由于系统动力学软件工具的进展，使系统动力学建模与模拟分

析变得更加规范与简单易学。

发源于美国麻省理工学院的Vensim软件，是由Ventana公司开

发，在全球和国内获得最广泛使用系统动力学建模软件。它具有图形

化的建模方法，除具有一般的模型模拟功能外，还具有复合模拟、数

组变量、真实性检验、灵敏性测试、模型最优化等强大功能。Vensim

有Vensim PLE, PLE Plus, Professional和 DSS版本，适合不同的

用户。

软件特点：

一、利用图示化编程建立模型。在Vensim中，“编程”实际上并

不存在，只有建模的概念。只要在模型建立窗口(Building)画出流图，

再通过Equation Editor输入方程和参数，就可以直接进行模拟了。

如果用户需要查看有关方程和参数，可使用Mode Document工具条。

另外，Vensim提供两种模型文件保存方式，一种是二进制文件，后

缀为.vmf；另一种是文本文件，后缀为.mdf，这种文件可以用于模型

的建立和修改，但这并不是Vensim推荐的方法。

二、运行于Windows下，数据共享性强，提供丰富的输出信息

和灵活的输出方式。由于采用了多种分析方法，因此Vensim的输出

信息是非常丰富的。其输出兼容性较强。一般的模拟结果，除了即时

显示外，还提供保存文件和copy到剪切板。例如建立好的模型可以

copy到剪贴板，再由剪贴板转到MS Word的编辑文件中。

三、对模型的多种分析方法

Vensim提供对于模型的结构分析和数据集分析。其中结构分析包括

原因树分析(逐层列举作用于指定变量的变量)、结果树分析(逐层列举

该变量对于其它变量的作用)和反馈列表。模型运行后，可进行数据

集分析。对指定变量，可以给出它随时间的变化图，列出数据表；可

以给出原因图分析，列出所有作用于该变量的其它变量随时间变化的

比较图；可以给出结果图分析，列出该变量与所有它作用的变量随时

间变化的比较图；同时可以将多次运行的结果进行比较。作为最终结

果的图形分析和输出，可使用Custom Graph，它不但可以列举多个

变量随时间的变化图，而且可以列举变量之间的关系图。

四、真实性检验对于我们所研究的系统，对于模型中的一些重要

变量，依据常识和一些基本原则，我们可以预先提出对其正确性的基

本要求。这些假设是真实性约束。将这些约束加到建好的模型中，专

门模拟现有模型在运行时对于这些约束的遵守情况或违反情况，就可

以判断模型的合理性与真实性，从而调整结构或参数。真实性检验是

Ventana公司的专利方法，是一种非常有效的建模工具。

此外，Vensim软件还可以对您的模型进行优化等.

系统工程学是研究分析有关复杂信息反馈系统的动态趋势的学科。系

统工程学以控制论、控制工程、系统工程、信息处理和计算机仿真技

术为基础 ，研究复杂系统随时间推移而产生的行为模式。

系统工程学把系统的行为模式看成是由系统内部的信息反馈机

制决定的。通过建立 系统工程学模型，可以研究系统的结构、功能

和行为之间的动态关系，以便寻求较优的系统结构和功能。

第二次世界大战以后，随着工业化的进展，城市人口、就业、环

境污染和资源等各种社会问题日趋严重，迫切需要用新的方法对这些

问题进行综合研究。

1955年以后，计算机技术渐趋成熟和普及，于是 系统工程学应

运而生。美国麻省理工学院的福雷斯特于1957年首次提出工业动力

学，后来研究对象从工程系统发展到社会系统，运用这一方法建立了

世界模型和美国国家模型。但各个领域的研究方法在本质上并没有什

么区别，故于1972年定名为 系统工程学。

系统工程学研究的对象是复杂的系统。除了一般大系统所具有的

结构复杂、因素众多、系统行为有时滞现象 ，以及系统内部诸参数

随时间而变化等特征外。系统工程学认为的复杂系统还有一些其他特

征，比如系统都是高阶数、多回路、非线性的信息反馈系统；系统的

行为具有“反直观”性，即其行为方式往往与多数人们所预期的结果

相反；系统内部诸反馈回路中存在一些主要回路；系统的非线性多次

反馈以后，呈现出对外部扰动反映迟钝的倾向，对系统参数变化不敏

感 等。

从系统方法论来说， 系统工程学是结构方法、功能方法和历史

方法的统一。它有一套独特的解决复杂系统问题的工具和技巧，如双

向因果环、反馈、流位和速率等概念。

系统工程学模型中能容纳大量的变量，一般可达数千个以上；它

是一种结构模型，通过它可以充分认识系统结构，并以此来把握系统

的行为，而不只是依赖数据来研究系统行为；它是实际系统的实验室。

系统工程学通过人和计算机的配合，既能充分发挥人的理解、分

析、推理、评价、创造等能力的优势，又能利用计算机高速计算和跟

踪能力。以此来实验和剖析系统，从而获得丰富的信息，为选择最优

的或次优的系统方案提供有力工具。

系统动力学模型主要是通过仿真实验进行分析计算，主要计算结

果都是未来一定时期内各种变量随时间而变化的曲线。也就是说，模

型能处理高阶次、非线性、多重反馈的复杂时变系统(如社会经济系

统)的有关问题。

建立系统工程学模型首先是确定系统分析目的；其次是确定系统

边界，即系统分析涉及的对象和范围；之后是建立因果关系图和流图；

然后写出 系统工程学方程；最后进行仿真试验和计算。

常用的系统工程学模型有世界动力学模型，用于研究全球性的发

展战略；国家动力学模型，用以研究国家政治、经济、军事、对外关

系等；城市动力学模型，研究城市发展战略；区域动力学模型，研究

特定地理区域的发展战略；工业动力学模型，研究工业企业发展战略；

生长型动力学模型，包括研究疾病发生、发展及防治策略的医疗动力

学模型；研究作物、园艺、家禽饲养、虫害防治和生态保护等的 系

统工程学模型等。

What are the limitations on Vensim PLE?

Vensim PLE has no built-in limitations. It it a simplified

version of Vensim designed for learning how to build and

analyze models. We removed all functionality not relevant

to learning modeling skills. Very few settings or options

can be changed making the software behave the same for

everyone. Vensim PLE is a serious tool for building and

using system dynamics models. For many people it will be

completely sufficient. Back to top

Why is Vensim PLE free?

Vensim PLE is free for academic use because we want to

make it easier for more people to learn system

dynamics. We especially want to lower the barriers of entry

for students. We also hope that people who learn with

Vensim PLE will start to use the modeling approach

seriously in their work and therefore pay the shareware

license fee, or choose to purchase a more advanced version

of Vensim. Back to top

What are the differences among PLE, PLE Plus,

Professional and DSS?

All the products share essentially the same interface and

each is a superset of the one that precedes it. Vensim PLE

Plus adds to PLE easier use of data, and Monte Carlo or

sensitivity simulation capabilities. Professional allows you

to use subscripts to represent more detail with less effort,

and also supports optimization. Vensim DSS include the

ability to construct management flight simulators and also

to use external functions and compiled simulations. There is

a comparison chart here. Back to top

What are the hardware requirements?

The Vensim family of software runs on Windows

98/NT/2000/XP/Vista/7. Vensim is a 32 bit progam but will

run fine on 64 bit versions of Windows. The Macintosh

version is curently in Beta and requires OSX version 10.4 or

higher. The Windows Version will run on the Macintosh using

Crossover, or with a Windows virtual/alternate boot

installation. Vensim requires about 20 megabytes of disk

space for a full installation and will run with any reasonable

amount of memory. For very large models more memory

and disk space will be required as a single run can easily

take 100 megabytes of disk space. Generally it is a good

idea to have at least as much memory as the size of the

largest .vdf file you are creating.

How soon can I get the software?

We normally ship products within one day of receiving the

order, online order are processed in real time. If you select

electronic delivery an email is sent with download and

install instructions and you can start using the product right

away. In the US we ship CDs via priority mail and it normally

takes 2 days. For international orders, shipment times

vary. More information on purchasing. Back to top

How does Vensim compare to other system dynamics

software?

For model building, Vensim and other system dynamics

languages have a great deal in common. The available

functions and default graphical presentations are

similar. Vensim is more flexible than most in the

appearance of the model diagram, allowing you to easily

mix stock and flow and causal loop elements.

On the analysis side, Vensim is unique. It contains a set of

Analysis tools that use the structure of the model to present

information to quickly find problems and investigate

sources of behavior. Our patented Causal Tracing

®

capabilities allow you to instantly see the behavior of a

variable and the variables that connect to it.

Vensim is also very strong in terms of capacity, performance

and functionality. Simulation speed is fast, the

optimization capabilities are powerful. The sensitivity

analysis is both fast and powerful, there are no practical

limits on model size, and it is easy to extend the base

capabilities using external functions of the Vensim

DLL. Back to top

What is an External Function?

Vensim has a large number of built in functions, but these

are not always enough. Suppose, for example, you would

like to allocate production among different facilities at each

time in a simulation. If the best way to do this is to use a

Linear Program, then an external function can be

constructed to do this. The external function is written in a

programming language (usually C or C++) and then

compiled into a dynamic link library (DLL) which is loaded

by Vensim. Back to top

What is a Compiled Simulation?

Compiled simulation is a technique for speeding up

simulation. The model equations are written out as a C

program which is then compiled and linked with Vensim as a

DLL. Fast simulation is especially important for

optimization. Back to top

How does Subscripting work?

Subscripting allows you to create a piece of model structure

and equations (for example, a store) then "subscript" it to

produce multiple stores, all with the same structure but with

their own constant values, inputs, and outputs. Read more

about subscripting Back to top

How does Optimization work?

Optimization can be used in several ways in Vensim. Model

calibration allows you to take external "real world" data

and then optimize model parameters (constants) so that

the model best fits the external data. Policy optimization

allows you to maximize (or minimize) one or many policy

parameters. For example, you might optimize multiple

parameters such as worker numbers, capital spending, etc.,

to maximize profit while minimizing production time, and all

constrained by certain limits. Optimization is performed

using a modified Powell hill climbing algorithm. Read more

about optimization Back to top

Will you include a genetic algorithm based

optimization?

We have experimented extensively with genetic algorithm

optimization and found that the results are very poor. We

will be making it easier to add in alternative search

algorithms in the future for people who want to pursue this

line of research. Back to top

How can I get a matrix of values into Vensim from a

spreadsheet?

Vensim (except PLE) supports the importation of times

series data from spreadsheets, but if you are just looking at

one time (either for initial conditions or constants) this is

not efficient. To set for, for example, initial population from

a spreadsheet, set the spreadsheet up in the form:

USA MEX CAN

initial population[country,male] 1 2 3

initial population[country,female] 2 3 4

Save the spreadsheet as a CSV (comma delimited)

file. The first row, because it contains no values in the first

column, is treated as a comment. Then in the model just

enter an equation such as:

initial population[country,sex]=1 ~Person~|

Then enter the CSV file you created from the spreadsheet as

a changes file in the simulation control dialog. Note that it

is important to be sure that the order of subscripts in the

subscript definition

country: USA,MEX,CAN ~~|

is the same as the order in the spreadsheet. Back to top

How can Vensim communicate with other programs?

There are a number of options for communication, starting

with the clipboard. Vensim can also easily import or export

data and constants from other sources. For dynamic

control of Vensim's behavior, the Vensim DLL allows you to

control Vensim from Visual Basic, Delphi or any other

programming language. Back to top

How can I get Vensim graphics into other

applications?

In almost all cases just use Edit>Copy in Vensim (or Ctrl+C)

and then paste them into your other application. For tool

output Vensim also has a little button you can click on to do

this. Back to top

How big can a Vensim model be?

With the exception of Vensim for Windows 3.1, there are no

limitations to the size of models. Some people have

models with excess of 1 million variables when all subscript

dimensions are expanded. Such models take a long time to

simulate and create very large output datasets, and

therefore need to be treated with care. Back to top

What are Analysis tools?

Analysis tools act on a selected variable to show something:

a graph of behavior, a tree diagram of connected variables,

the variable's equation, all the feedback loops passing

through it, and other information. Back to top

What is Causal Tracing®?

Several analysis tools allow you to perform Causal

Tracing® A Causes Tree diagram shows a selected variable

and the variables that "cause" it to change (up to 3

connections distant — this is adjustable). Selecting a

variable in this tree and clicking the Causes Tree tool again

creates a tree diagram of that variable. In this way, you

can trace the causes (or uses) of a variable throughout a

model. A Causes Strip Graph displays behavior for the

selected variable and all the variables directly connected to

it so that you can see which variables contribute which

types of behavior. Selecting one of these variables and

clicking the Causes Strip Graph again traces the behavior

for that variable and variables directly connected to it. You

can continue to trace sources of behavior throughout your

model. This is useful for discovering which feedback loops

contribute certain types of behavior in a model (growth,

decay, etc.). Read more about Causal Tracing Back to

top

What is a Dataset?

Simulations produce a "dataset" of output values for every

variable in the model. This allows you to do "scientific

experiments" on the model, saving each simulation as a

different named experiment for later comparison. No need

to perform repeated simulations just to look at other

variable's behaviors. Graph showing multiple

experiments Back to top

How can I get variable names to appear on a single

line?

By default, variables are entered in clear boxes. For

variables already created, right click (or control click) on the

variable name and select the shape "None" For variables

you are putting onto the sketch using the Variable tool,

change the option for the tool to Shape "None". Or go to

Tools>Options>Sketch and uncheck "Start Words in Clear

Box." Back to top

How do I draw bent or split rate pipes?

Bent Pipes: Start the rate as usual (select the Rate tool

and click once on a blank part of the sketch or on a level),

then move the cursor to a place you want the pipe bent,

hold down the shift key and click once on the sketch. This

drops a "corner". If you want more bends/corners, keep

holding down the shift key and click on the sketch. Finish

the rate by clicking without holding the shift key down.

Split Pipes: Rate pipes can start or stop at three places: at

a cloud on the sketch, at a level, and at a valve. If, for

example, you want a single rate to come out of one level

and then to split and feed into two levels, this is how you do

it. Create the three levels. Join two together with a

rate. Again with the Rate tool, click on the valve of the first

rate, then hold the shift key and click on a blank part of the

sketch near the third level, then click on the third

level. (This makes Vensim put the rate pipe on the sketch

and bend it near the third level. If you don't do this, you

might find that Vensim draws the pipe with its bend through

the second level, because pipes can only be horizontal or

vertical.)

You can also make the illusion of a pipe splitting off

somewhere other than a valve (see page 22 of the Vensim

Modeling Guide) by clicking on the valve, then creating a

bend on top of the existing pipe, then making another bend

near the level and finishing on the level. The two pipes will

be drawn exactly on top of each other, creating the illusion

of a single pipe at that point.

How do I delete an arrow?

The packman icon deletes things — just click on the

arrowhead with it (clicking on the handle no longer deletes

the arrow).

How do I connect a box variable to the cloud end of a

previously-inserted rate?

1) If you are wanting to join the arrowhead end of a rate

(that drops into a cloud), using the Hand tool, drag the

arrowhead of the rate onto your box variable, or

2) If you don't have an arrowhead (pipe comes out of a

cloud), or even if you do have an arrowhead, using the

Merge tool, drag and drop the box variable onto the

arrowhead or cloud.

3) PLE and PLE Plus do not have a Merge tool. To connect a

box variable to the cloud of a previously inserted rate, select

the Rate tool, click on the box variable and then click on the

valve of the rate (not on the cloud). Then use the Delete tool

to delete the cloud.

本文标签： 模型系统变量研究建立