Amesim 气压元件设计
AMESim机械库中元件的介绍
MechanicalAMESIM机械库包含了用于构建一维平动和转动机械系统的元件模块,可独立用于完整的一维机械系统建模。
在AMESim中,为子模型设置参数的时候,可以使用表达式来表示,尤其是对于表达式计算结果不是有限数的时候。
AMESim所使用的外部变量的符号约定也很重要:对于自身有方向的变量,正号表示与箭头方向一致。
(下面通过质量块进行详细讲解)sets the gravity如何设定重力方向?可在质量块的参数里面设置角度。
系统认为向下是正方向,默认重力加速度是9.80665 m/s/s。
通常情况下是不使用该图标的,除非是想改变重力加速的g。
在下图模型中(弹簧自由伸长),当设置质量块的初始角度为0时,仿真完成后质量块的速度一直为0;如果设置初始角度为90度,则速度成正弦波变化。
null to force units子模型:FORC - conversion of signal input into a force in N将无单位的信号转换为同等大小的、以N为单位的力。
null to linear speed unitsnull to linear velocity with calculation of displacement信号转换为线性速度,并计算出位移。
null to linear displacement with calculation of velocity信号转换为线性位移,并计算出速度。
2 nulls to linear velocity in m/s and displacement in mconversion between linear variables and signal variables输入速度信号,返回力信号。
与上一个相反略……force transducer 力传感器信号的形成:用力减去某一数值offset(用户自己设定,单位:m/s)后所得结果乘上一个增益gain(放大倍数,单位:s/m),就得到了一个没有单位的信号在端口2输出。
AMESim热气动库资料
dt
dt
©IMAGINE SA 1998-2006
Training
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阻性元件
17
计算质量流量(可压)
Pu
Pd
Tu
Td
m
m
dmh
dmh
Flow
m ACqCm Pu Tu
2
Cm r1
2
1
Pd Pu
Pd Pu
Pd
Pu
Pcr
(subsonic
)
1
1
r
211
r21 211
Pd Pu
Training
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热气动库
3
库图标
热气动库元件:
©IMAGINE SA 1998-2006
Training
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主要元件
气体热力学属性: 容性元件(绝热或传热): 阻性元件(压力损失): 容性 – 阻性元件(绝热或传热)
摩擦 + 可压 + 对流
©IMAGINE SA 1998-2006
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©IMAGINE SA 1998-2006
Training
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气体热力学属性- 混合气
10
通过‘Gas Mixt.’图标可以定义混合气
通过气体质量组分定义混合气组成: 例如空气
©IMAGINE SA 1998-2006
Training
10
气体热力学属性- 混合气
11
空气组成(% 体积比 = 摩尔组分):
©IMAGINE SA 1998-2006
Training
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容性元件
16
压力为状态变量,通过理想气体状态方程计算:
dp 1 [
根据AMESim的气动系统建模与仿真技术研究
基于AMESim的气动系统建模与仿真技术研究(版本A)本文主要内容如下(1)推导气体的流量、温度和压力方程。
(2)基于AMESim对普通气动回路进行仿真分析。
并推导气动系统常用元件的数学方程,在此基础上对气动元件及系统进行模型仿真分析。
(3)对气动比例位置系统进行建模与仿真研究,在系统仿真模型基础上进行故障仿真研究。
最后探讨基于 AMESim 的气动比例位置系统实时仿真研究。
1.气动系统建模的理论基础气动系统和元件建模的首要任务就是要充分的明确空气的物理性质和空气的热力学性质,为准确的元件建模和系统仿真奠定基础。
气动元件的结构是十分复杂的,但其中的基本规律和数学描述一般还是比较清楚的。
经过前人的大量研究发现,气动系统的动态特性从本质上讲可以抽象为由一些基本环节所组成,比如放气环节、惯性环节和气容充气环节等等。
而它们之间又是通过压力、力、位移、容积等参数相互关联相互影响的。
1.1 流量方程流量特性表示元件的空气流通能力,将直接影响气动系统的动态特性。
所有的压力降取决于下面两个基本参数:a)声速流导 C(Sonic Conductance)——[null]b)临界压力比b(Critical Pressure Ratio)[S*m4/kg]ISO6358标准孔口——标准体积流量设绝对温度T ,绝对压力p的工况下的体积流量为Q,基准状态和标准状态下的体积流量可表示为:空气压缩机的输出流量通常用换算到吸入口的大气状态下的体积流量来表示。
以上公式同样适用于从吸入口的大气状态到基准或标准状态的换算。
气动孔口流量在气动系统中,一般需要计算通过节流口的气体压力、流量、温度等参数,但是由于气体的可压缩性,气体在通过节流口时是个很复杂的过程,节流口前后的流道突然收缩或扩张,气体在孔口前后均会形成涡流,产生强烈的摩擦,因而机械能变成热能具有不可逆过程。
同时,由于流体运动的极不规则,同一界面上的各点参数极不均匀。
为了研究气体的流量特性,基本上可将阀中的节流口理想地等价为一个小孔或收缩喷嘴,并用小孔或者收缩喷嘴的流量特性来表示其流量特性。
基于AMESim的气动系统建模与仿真技术研究
基于AMESim的气动系统建模与仿真技术研究(版本A) 本文主要内容如下(1)推导气体的流量、温度与压力方程。
(2)基于AMESim对普通气动回路进行仿真分析。
并推导气动系统常用元件的数学方程,在此基础上对气动元件及系统进行模型仿真分析。
(3)对气动比例位置系统进行建模与仿真研究,在系统仿真模型基础上进行故障仿真研究。
最后探讨基于 AMESim 的气动比例位置系统实时仿真研究。
1、气动系统建模的理论基础气动系统与元件建模的首要任务就就是要充分的明确空气的物理性质与空气的热力学性质,为准确的元件建模与系统仿真奠定基础。
气动元件的结构就是十分复杂的,但其中的基本规律与数学描述一般还就是比较清楚的。
经过前人的大量研究发现,气动系统的动态特性从本质上讲可以抽象为由一些基本环节所组成,比如放气环节、惯性环节与气容充气环节等等。
而它们之间又就是通过压力、力、位移、容积等参数相互关联相互影响的。
1、1 流量方程流量特性表示元件的空气流通能力,将直接影响气动系统的动态特性。
所有的压力降取决于下面两个基本参数:a)声速流导 C(Sonic Conductance)——[null]b)临界压力比b(Critical Pressure Ratio)[S*m4/kg]ISO6358标准孔口——标准体积流量设绝对温度T ,绝对压力p的工况下的体积流量为Q,基准状态与标准状态下的体积流量可表示为:空气压缩机的输出流量通常用换算到吸入口的大气状态下的体积流量来表示。
以上公式同样适用于从吸入口的大气状态到基准或标准状态的换算。
气动孔口流量在气动系统中,一般需要计算通过节流口的气体压力、流量、温度等参数,但就是由于气体的可压缩性,气体在通过节流口时就是个很复杂的过程,节流口前后的流道突然收缩或扩张,气体在孔口前后均会形成涡流,产生强烈的摩擦,因而机械能变成热能具有不可逆过程。
同时,由于流体运动的极不规则,同一界面上的各点参数极不均匀。
根据AMESim的气动系统建模与仿真技术研究
基于AMESim的气动系统建模与仿真技术研究(版本A)本文主要内容如下(1)推导气体的流量、温度和压力方程。
(2)基于AMESim对普通气动回路进行仿真分析。
并推导气动系统常用元件的数学方程,在此基础上对气动元件及系统进行模型仿真分析。
(3)对气动比例位置系统进行建模与仿真研究,在系统仿真模型基础上进行故障仿真研究。
最后探讨基于 AMESim 的气动比例位置系统实时仿真研究。
1.气动系统建模的理论基础气动系统和元件建模的首要任务就是要充分的明确空气的物理性质和空气的热力学性质,为准确的元件建模和系统仿真奠定基础。
气动元件的结构是十分复杂的,但其中的基本规律和数学描述一般还是比较清楚的。
经过前人的大量研究发现,气动系统的动态特性从本质上讲可以抽象为由一些基本环节所组成,比如放气环节、惯性环节和气容充气环节等等。
而它们之间又是通过压力、力、位移、容积等参数相互关联相互影响的。
1.1 流量方程流量特性表示元件的空气流通能力,将直接影响气动系统的动态特性。
所有的压力降取决于下面两个基本参数:a)声速流导 C(Sonic Conductance)——[null]b)临界压力比b(Critical Pressure Ratio)[S*m4/kg]ISO6358标准孔口——标准体积流量设绝对温度T ,绝对压力p的工况下的体积流量为Q,基准状态和标准状态下的体积流量可表示为:空气压缩机的输出流量通常用换算到吸入口的大气状态下的体积流量来表示。
以上公式同样适用于从吸入口的大气状态到基准或标准状态的换算。
气动孔口流量在气动系统中,一般需要计算通过节流口的气体压力、流量、温度等参数,但是由于气体的可压缩性,气体在通过节流口时是个很复杂的过程,节流口前后的流道突然收缩或扩张,气体在孔口前后均会形成涡流,产生强烈的摩擦,因而机械能变成热能具有不可逆过程。
同时,由于流体运动的极不规则,同一界面上的各点参数极不均匀。
为了研究气体的流量特性,基本上可将阀中的节流口理想地等价为一个小孔或收缩喷嘴,并用小孔或者收缩喷嘴的流量特性来表示其流量特性。
基于AMESim双筒叠加阀片式充气减振器建模与仿真_马天飞
密度; ε 为小孔的流量系数; h1 为带孔节流阀片厚 度; lA 为孔的宽度。 1.2.2 减振器复原阀初次开阀
随着活塞相对工作缸运动速度的增加,减振器
上腔的压力也随之增大,当作用在复原阀片的压力
Fup 达到弹性阀片预紧力时,复原阀打开。此时有
Fup = pud1 + pud 2
(6)
与开阀前相似,油液经活塞孔、开阀后形成的
活塞上下压差 pud (t) 可看成由两部分组成:① 活塞孔的节流作用产生的压差 pud1(t) ;②复原阀上 的常通节流孔产生的压差 pud 2 (t) ,即
pud (t) = pud1(t) + pud 2 (t)
(3)
测量得活塞孔长与孔径的比值大于 4,故减振
器油液在此孔中的流动可视为细长孔中的流动,而
关键词:减振器 AMESim 气体反弹力 叠加阀片 阻尼特性
中图分类号:U463
Modeling and Simulating of the Gas-precharged Dual-sleeve Shock Absorber with Multiple Valve Plates Using AMESim
(吉林大学汽车仿真与控制国家重点实验室 长春 130022)
摘要:以某乘用车前悬架双筒叠加阀片式充气液压减振器为研究对象,通过对其工作原理进行分析,建立该减振器在各种工 况下的数学模型。基于该减振器的数学模型,在多领域系统仿真分析软件 AMESim 中搭建其详细的仿真草图模型。考虑到 叠加阀片的非线性弹性特性,根据叠加阀片的等效厚度计算公式,在有限元分析软件 Abaqus 中建立阀片的有限元模型,仿 真得出阀片受力与变形曲线,再将曲线数据导入 AMESim 模型中进行系统仿真。仿真结果表明,减振器速度特性曲线和示 功图与试验数据吻合良好,符合工程实际要求,证明所建 AMESim 模型的正确性。基于 AMESim 模型研究该减振器的气体 反弹力、活塞缝隙和常通节流孔等几个关键设计参数对减振器阻尼特性的影响,并得出几个重要的结论。仿真模型可用于指 导减振器的关键参数的设计与性能预测。
AMESim热气动库资料
不同类型的元件
15
容性元件:
被视为气体容腔,腔内压力、温度为状态变量
阻性元件:
通过输入的温度和压力计算焓流量和质量流量
©IMAGINE SA 1998-2006
Training
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容性元件
压力为状态变量,通过理想气体状态方程计算:
dp 1 dT dV i r T m r [i m p ] dt V dt dt
m dmh
m dmh
Flow
计算焓流量
h m C p dT dmh m
©IMAGINE SA 1998-2006
Training
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换热器模型
基于effectiveness – NTU 模型:
广泛应用于换热器计算
18
入口温度必须已知
3个元件:
9
AMESim提供了gasgen.exe用于计算多 项式系数 :
©IMAGINE SA 1998-2006
Training
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气体热力学属性- 混合气
10
通过‘Gas Mixt.’图标可以定义混合气
通过气体质量组分定义混合气组成: 例如空气
©IMAGINE SA 1998-2006
Training
THPN
Chapter 4
热气动库
©IMAGINE SA 1998-2006 Updated: October 2005
Training
简介
2
模拟热气动系统管网 计算系统压力、温度、质量流量和焓流量 系统可以由多种气体组成 研究气体与壁面之间换热(热端口) 与热库兼容
©IMAGINE SA 1998-2006
AMESIM介绍资料讲解
A M E S I M介绍第二章AMESim的应用方法2.1 AMESim简介AMESim表示系统工程高级建模和仿真平台(Advanced Modeling Environment for Simulations of engineering systems)。
它能够从元件设计出发,可以考虑摩擦、油液、和气体的本身特性、环境温度等非常难以建模的部分,直到组成部件和系统进行功能性能仿真和优化,并能够联合其他优秀软件进行联合仿真和优化,还可以考虑控制器在环构成闭环系统进行仿真,使设计出的产品完全满足实际应用环境的要求。
AMESim软件共由四个功能模块组成:AMESim、AMESet、AMECustom、AMERun,另外还有软件帮助模块AMEHelp。
其中,AMESim用于面向对象的系统建模、参数设置、仿真运行和结果分析,是该工具软件的主功能模块,主要工作模式为:按系统原理图建模一确定元件子模型一设定元件参数一仿真运行一结果观测和分析。
AMEest用于构建符合用户个人需求的元件子模型,主要通过两步进行:先设定子模型外部参数情况,系统自动生成元件代码框架,再通过用户的算法编程实现满足用户需要的元件,程序使用C或Fortnar77实现;AMECustom用于对软件提供的元件库中的元件进行改造,但不能深入到元件代码层次,只适用于元件的外部参数特性的改造;AMERun是提供给最终用户的只运行模块,最终用户可以修改模型的参数和仿真参数,执行稳态或动态仿真,输出结果图形和分析仿真结果,但不能够修改模型结构,不能够访问或修改元件代码等涉及技术敏感性的信息。
2.2AMESim的特点1.多学科的建模平台AMESim在统一的平台上实现了多学科领域的系统工程的建模和仿真,模型库丰富,涵盖了机械、液压、控制、液压管路、液压元件设计、液压阻力、气动、热流体、冷却、动力传动等领域,且采用易于识别的标准ISO图标和简单直观的多端口框图,方便用户建立复杂系统及用户所需的特定应用实例。
基于AMESim的气动系统建模与仿真技术研究
基于AMESim的气动系统建模与仿真技术研究基于AMESim的气动系统建模与仿真技术研究(版本A)本文主要内容如下(1)推导气体的流量、温度和压力方程。
(2)基于AMESim对普通气动回路进行仿真分析。
并推导气动系统常用元件的数学方程,在此基础上对气动元件及系统进行模型仿真分析。
(3)对气动比例位置系统进行建模与仿真研究,在系统仿真模型基础上进行故障仿真研究。
最后探讨基于 AMESim 的气动比例位置系统实时仿真研究。
1. 气动系统建模的理论基础气动系统和元件建模的首要任务就是要充分的明确空气的物理性质和空气的热力学性质,为准确的元件建模和系统仿真奠定基础。
气动元件的结构是十分复杂的,但其中的基本规律和数学描述一般还是比较清楚的。
经过前人的大量研究发现,气动系统的动态特性从本质上讲可以抽象为由一些基本环节所组成,比如放气环节、惯性环节和气容充气环节等等。
而它们之间又是通过压力、力、位移、容积等参数相互关联相互影响的。
1.1 流量方程流量特性表示元件的空气流通能力,将直接影响气动系统的动态特性。
所有的压力降取决于下面两个基本参数:a) 声速流导 C(Sonic Conductance)——[null] b) 临界压力比b(Critical Pressure Ratio)[S*m/kg]4ISO6358标准孔口——标准体积流量设绝对温度T ,绝对压力p的工况下的体积流量为Q,基准状态和标准状态下的体积流量可表示为:空气压缩机的输出流量通常用换算到吸入口的大气状态下的体积流量来表示。
以上公式同样适用于从吸入口的大气状态到基准或标准状态的换算。
气动孔口流量在气动系统中,一般需要计算通过节流口的气体压力、流量、温度等参数,但是由于气体的可压缩性,气体在通过节流口时是个很复杂的过程,节流口前后的流道突然收缩或扩张,气体在孔口前后均会形成涡流,产生强烈的摩擦,因而机械能变成热能具有不可逆过程。
同时,由于流体运动的极不规则,同一界面上的各点参数极不均匀。
基于AMESim的气压式车用主动辅助制动能量回收系统研究
的是 为 了减少 制动 系统 磨损 , 提 高车 辆动 力性 , 降低油 耗 和 排放 。采 用 的制 动 能量 回收方 案 主要 有 三 类 : 机
参考文献 :
[ 3 ] 赵静一 , 王智勇 , 覃 艳 明, 王金 祥. T L C 9  ̄ 型运 梁车 电液
摘
要: 提 出一种 气压 式 能量 回收 方案 , 基 于 多学科 领域 复杂 系统建 模 仿 真 平 台 A ME S i m软件 , 建 立 气
压 式 车用制 动 能量 回收 系统 的仿真模 型 。针 对 车辆 下坡 和超 速 情 况 , 通 过 分析 系统 工作 过 程 中车速 变化 及 系统储 气罐 中气压 变化 来研 究 系统 的可 行性及 其 能量 回收 效 率。仿 真结 果表 明 : 在 车辆 下 长坡 时 , 系统 可 以
能减 排及 现代 车辆 设计 对安 全性 的要求 。
收 稿 日期 : 2 0 1 3  ̄3 — 1 2
基金项 目: 山西省 高等学校科技 项 目( 2 0 1 2  ̄2 0 ) 作者简介 : 岳喜凯 ( 1 9 8 8 一) , 男, 山东聊城人 , 硕 士研究生 , 研 究方 向为液压技术和车用轮胎 主动 防护技术 。
岳喜凯 ,李晓杰 , 董小瑞 , 王 龙
S t u d y o f P n e u ma t i c Ac t i v e l y Au x i l i a r y Br a k i n g En e r g y Re c o v e r y S y s t e m
关键 词 : 能量 回收 ; 气压 ; A ME S i m; 建模 ; 仿 真 中 图分类 号 : T H1 3 8 ; U 4 6 3 . 5 文 献标 志码 : B 文章 编 号 : 1 0 0 0 48 5 8 ( 2 0 1 3 ) 0 9 - ( ) 0 1 9 - ( ) 4
AMESim-HCD液压元件设计库教程-完整版.
表示该活动区域,为更清楚起见,还有箭头指向该区域。这些图标通常通
过线性轴端口连接起来,以组成一实体,可能是滑阀、液压执行器,也可
以是单向阀。然而,其它的实体像液压制动元件,自动变速箱或燃油注射
系统等也可以以相同的方式来构造。
最常使用的液压图标则是具有压缩性的液压容腔,其与所计算液压压力的子模
型相关。该模型有四个液压端口,用以接收来流的流量和体积,可据此计算总
体积和总流量。如果流量为正,则压力升高;如果流量为负,则压力降低。
最简单的单向阀包含在有限位移内自由移动的钢球,在极限位置完全关闭阻断
通流,而在另一位置则完全打开。平衡状态时,钢球位置取决于两液压端口的液压力。
HCD包含两个液压流道中阀芯为球形的图标,一个
压力作用下的液压流体;
环形可变容腔;
机械弹簧;
由压力和面积产生作用力的活塞;
以上表明,这将是一个很好使用的划分。与基于标准ISO符号的划分相比较,可以清楚地看到基本模块会少很多。每一元素都是工程师眼中有形的实体,因此可以将这样的划分描述为技术单元。用户可以到工程模块库中,寻找物理模型对应的图标,使用他们组装成需要的组件。
位于平面圆形阀座,另一个则位于锥形阀座,与平
面圆形阀座相关联的子模型如图5所示。请注意:
有两个液压流量端口,任一端口接受压力作为输入;
如果钢球在最右位置,流道会被阻塞;
如果钢球在最左位置,流道开口最大;
子模型中与钢球相连的杆默认直径为零;
钢球受压力支配,如果不平衡,钢球将会移动。这意味着,我
们必须考虑钢球的惯性。由于单向阀钢球的运动受限,我们需
要如图所示右手侧的图标,详细外部变量如图6所示。
amesim压缩气体案例
amesim压缩气体案例AMESim压缩气体案例1. 案例概述本案例以AMESim软件为工具,研究压缩气体系统的性能和特性。
通过建立系统模型,分析压缩机、冷却器和储气罐等组件之间的相互作用,探究压缩气体在不同条件下的工作状态和能量转换过程。
2. 压缩气体系统组成压缩气体系统主要由压缩机、冷却器、储气罐和管道等组件构成。
其中,压缩机负责将气体压缩,冷却器用于降低气体温度,储气罐用于储存压缩气体,管道则负责输送气体。
3. 压缩机的工作原理压缩机通过转子或活塞等机械装置将气体进行压缩,提高气体的密度和压力。
在压缩过程中,气体的温度也会升高,因此需要冷却器来降低气体温度,以保证压缩机的工作效率和稳定性。
4. 冷却器的作用冷却器通过传热的方式,将压缩气体的温度降低到可接受范围。
常见的冷却方式包括空气冷却和水冷却,通过冷却器的作用,可以有效地降低气体的温度,提高系统的效率和稳定性。
5. 储气罐的功能储气罐用于储存压缩气体,起到平衡系统压力和稳定气体供应的作用。
储气罐的容积越大,储存的气体量越大,系统的稳定性也会更好。
同时,储气罐还可以用于缓冲压力峰值,减少系统的压力波动。
6. 管道的输送特性管道在压缩气体系统中起到输送气体的作用,其输送特性对系统的性能有着重要影响。
管道的直径、长度和材料等因素都会影响气体的流动速度和压力损失,因此需要合理设计管道系统,以提高系统的效率。
7. 压缩气体的能量转换过程在压缩气体系统中,气体的能量会发生转换。
压缩机通过机械转换将电能转化为气体的压力和动能,冷却器则通过传热将气体的热能散发出去,储气罐则储存了气体的压力能。
整个系统的能量转换过程需要合理协调各组件之间的工作状态。
8. 压缩气体系统的优化通过对压缩气体系统进行建模和仿真分析,可以优化系统的性能和特性。
例如,可以调整压缩机的工作参数,选用合适的冷却器和储气罐,以及设计合理的管道系统,来提高系统的效率和稳定性。
9. 压缩气体系统的应用领域压缩气体系统广泛应用于工业生产、能源领域和汽车工程等领域。
AMESim液压手册
AMESim液压手册1.1 介绍AMESim液压手册包括:*通常组成的元件包括泵,马达,孔口,以及其他,也包括特别的阀门*小管和软管的子模型*压力和流动比率的源头*压力和流动比率的检测计*流体种类的组成压力系统孤独的存在完全是没用的,它离不开流体和过程控制。
这意味着手册必须能和其他AMESim手册相兼容。
以下的手册是经常和压力手册一起并用:机械手册应用于流体压力装置当水压能量转化为机械能量信号,控制,检测手册应用于控制和水压系统水压元件设计手册从非常基本的液压和机械单元应用于建造特别的的元件液压组成手册这是一个组成包括弯曲,丁字接头,弯头以及其他,它被用于典型的诸如冷却和润滑系统的低压装置第一节个别的案例注释*在液压手册里尽可能的用多余一种的流体,这是非常重要的因为你能够做出模型关于冷却和润滑系统的手册*液压手册假设一个统一的温度贯穿于整个系统,如果热量影响被考虑到很重要,热量液压和热量液压元件设计手册应该使用*有许多气穴和空气释放的模型在液压手册。
注释有一种特别的二相流体手册,一种典型的关于这种空气调节系统的装置第一节手册包括一系列个别的例子。
我们强烈的建议你认真的对待这些个别的例子。
这些假定你有一个基本的使用AMESim的水平。
作为一个完全最小的工作量你应该做些第三节关于AMESim手册的例子和第五节第一个关于描述如何使用一组的第一个例子1.2案例1:一个简单的液压系统目标*组建一个非常简单的液压系统*介绍一个简单的小管/软管子系统*解释一个结果使用一个特别的参考关于空气释放和空穴图形1.1 一个非常简单的液压系统在这个练习中你将要构造图形1.1中的系统,这可能是最简单具有意义的液压系统。
它是由部分液压种类(通常是蓝色)和部分机械种类元件建造液压部分由用于液压系统的标准符号组成。
主要的原动力提供泵的力量,从水槽拉动液压流体。
这种流体在压力下提供给一个驱动旋转负载液压马达,当压力达到某个值的时候一个解除阀门打开,一个马达和解除阀门的输出流回水槽,图标显示了三个水槽却非常像是仅仅一个水槽被利用了。
AMESim仿真技术及其在液压元件设计和性能分析中的应用
第29卷增刊12007年舰 船 科 学 技 术SH I P SC I E NCE AND TECHNOLOGY Vol .29,Supp le ment 12007文章编号:1672-7649(2007)S1-0142-04A MESi m 仿真技术及其在液压元件设计和性能分析中的应用肖岱宗(郑州机电工程研究所,河南郑州450015)摘 要: AM ESi m 是法国IM AGI N E 公司推出的一种基于键合图的高级系统建模、仿真及动态性能分析软件,它以强大的仿真和分析能力在各个领域得到了广泛的应用。
简要介绍了AMESi m 软件及其建模方法和主要特点,并在AM ESi m 仿真环境下,运用AMESi m 提供的液压元件设计库、液阻库和其他子模型库,构建了弹库防火防爆安全系统自动快速喷淋分系统中安全阀喷头组合的仿真模型。
通过调节仿真模型的各项参数对安全阀喷头组合的喷淋性能进行了分析,绘制了流量曲线等仿真结果图。
关键词: AMESi m ;仿真;液压元件设计中图分类号: T H13715 文献标识码: AS i m ul a ti on techn i que of AM ES i m and its appli ca ti on i n desi gn andperformance ana lysis of hydrauli c com ponen tX I A O Dai 2z ong(Zhengzhou Electr omechanical Engineering Research I nstitute,Zhengzhou 450015,China )Abstract: AMESi m is one kind of s oft w are for modeling,si m ulati on and dyna m ic perfor mance analy 2sis of advanced engineering syste m s based on bond graph,which is a p r oducti on of I M AGI N E Cor porati on of France .It obtained wides p read use in different fields with its powerful si m ulati on and analysis .AMESi m s oft w are,its modeling method and main features are briefly intr oduced in this paper .And under the AMES 2i m si m ulati on envir onment,using hydraulic component design library,hydraulic resistance library and other sub model libraries p r ovided by AMESi m s oft w are,the si m ulati on model of the asse mbly safety s p rinkler valve is constructed,which is one kind of hydraulic component of the a mmuniti on depot fire and exp l osi on safety syste m aut omatic rap id s p rinkler subsyste m.By changing the para meters of the si m ulati on model,the s p ray perf or mance of the hydraulic component is analyzed,and the si m ulati on result graphs,such as fl ow curves etc,are als o p l otted .Key words: AMESi m ;si m ulati on;hydraulic component design收稿日期:2007-03-07作者简介:肖岱宗(1974-),男,工程师,从事液压系统的设计工作。
基于AMEsim的气压制动系统分析与优化
基于AMEsim的气压制动系统分析与优化摘要:本文基于AMEsim对气压制动系统建模,并对压力响应时间影响因素进行分析与优化。
结果表明:优化后的前制动气室压力响应时间减少了0.14s,后气室减少了0.15s。
关键词:制动响应时间;气压制动;AMESim;制动性能Analysis and optimization of pneumatic brake system based on AMEsimRUAN shuai ZHANG zhu-lin ZOU yan-ran JIANG de-fei(1.School of Automotive Engineering,shandongjiaotong university,Jinan 250357,China.)Abstract: In this paper, the pneumatic braking system is modeled based on AMEsim, and the influencing factors of pressure response time are analyzed and optimized. The results show that the optimizedpressure response time of the front brake chamber is reduced by 0.14s, and that of the rear brake chamber is reduced by 0.15s.Key words: Pressure response time;air brake;AMEsim;brake performance中图分类号:U463.55 文献标志码:A0 引言气压制动系统存在制动响应时间长的弊端,对其制动响应时间进行优化十分必要。
赵夜城[1]等研究了制动阀动态响应特性,分析了平衡弹簧刚度等对制动阀响应特性的影响;方桂花[2]等分析了继动阀响应特性影响因素;以上研究大多针对于单一元件进行分析,基于完整的气压制动动态特性研究较少。
amesim液压元件设计库教程
Chapter 2
1
液压元件设计库
Hydraulic Component Design (HCD)
世冠工程(北京)有限公司 丁强博士
2007世冠AMESim液压、气动系统及其元件设计专题培训
液压元件设计库(HCD)
目录 1. 2. 3. 4. 5. HCD库简介:为什么? 如何做? 应用实例 设计一个单向阀 超模块工具 设计一个三通阀
HCD: 可变容积 假设活塞移动的速度 0.1m/s, 我们可以计算 出产生0.1L/min的流量需要的活塞面积
A= Q 0.1 1 1 100 = = m2 = mm 2 . V 60000 0.1 60000 6
14
对应的活塞直径为
Dp = 4A
π
=
20 mm ≈ 4.607 mm 6π
2007世冠AMESim液压、气动系统及其元件设计专题培训
HCD: 可变容积
让我们看看右腔的体积变化
26
我们看到体积在0.1cm3饱和了,为什么?
为了在AMESim中避免0或者负的体积出现,有一个饱和设定 为 V0/100,其中V0 = 在液压容腔中定义的Dead volume 这种情况本不应该出现, 只是我们参数设置不当造成的
2007世冠AMESim液压、气动系统及其元件设计专题培训
2
2007世冠AMESim液压、气动系统及其元件设计专题培训
AMESim中的标准液压库
3
2007世冠AMESim液压、气动系统及其元件设计专题培训
为什么需要液压元件设计库 ?
想一想 : 世界上有多种类型的液压缸?
4
在此我们假设液压缸的缸体是固定的。 如果液压缸的缸体是可动的话, 那么液压缸类型的数目就要翻一倍!有时对同一种类型还需要考虑端口不 同的因果规则 (C 或 R)
基于AMESim的气动系统建模及仿真技术研究报告
基于AMESim的气动系统建模与仿真技术研究〔版本A〕本文主要容如下(1)推导气体的流量、温度和压力方程。
(2)基于AMESim对普通气动回路进展仿真分析。
并推导气动系统常用元件的数学方程,在此根底上对气动元件及系统进展模型仿真分析。
(3)对气动比例位置系统进展建模与仿真研究,在系统仿真模型根底上进展故障仿真研究。
最后探讨基于AMESim 的气动比例位置系统实时仿真研究。
1. 气动系统建模的理论根底气动系统和元件建模的首要任务就是要充分的明确空气的物理性质和空气的热力学性质,为准确的元件建模和系统仿真奠定根底。
气动元件的构造是十分复杂的,但其中的根本规律和数学描述一般还是比拟清楚的。
经过前人的大量研究发现,气动系统的动态特性从本质上讲可以抽象为由一些根本环节所组成,比方放气环节、惯性环节和气容充气环节等等。
而它们之间又是通过压力、力、位移、容积等参数相互关联相互影响的。
1.1 流量方程流量特性表示元件的空气流通能力,将直接影响气动系统的动态特性。
所有的压力降取决于下面两个根本参数:a)声速流导C(Sonic Conductance)——[null]b)临界压力比b(Critical Pressure Ratio)[S*m4/kg]ISO6358标准孔口——标准体积流量设绝对温度T ,绝对压力p的工况下的体积流量为Q,基准状态和标准状态下的体积流量可表示为:空气压缩机的输出流量通常用换算到吸入口的大气状态下的体积流量来表示。
以上公式同样适用于从吸入口的大气状态到基准或标准状态的换算。
气动孔口流量在气动系统中,一般需要计算通过节流口的气体压力、流量、温度等参数,但是由于气体的可压缩性,气体在通过节流口时是个很复杂的过程,节流口前后的流道突然收缩或扩,气体在孔口前后均会形成涡流,产生强烈的摩擦,因而机械能变成热能具有不可逆过程。
同时,由于流体运动的极不规那么,同一界面上的各点参数极不均匀。
为了研究气体的流量特性,根本上可将阀中的节流口理想地等价为一个小孔或收缩喷嘴,并用小孔或者收缩喷嘴的流量特性来表示其流量特性。
AMESim液压手册例子讲解
AMESim液压手册例子讲解1.1 介绍AMESim液压手册包括:*通常组成的元件包括泵,马达,孔口,以及其他,也包括特别的阀门*小管和软管的子模型*压力和流动比率的源头*压力和流动比率的检测计*流体种类的组成压力系统孤独的存在完全是没用的,它离不开流体和过程控制。
这意味着手册必须能和其他AMESim手册相兼容。
以下的手册是经常和压力手册一起并用:机械手册应用于流体压力装置当水压能量转化为机械能量信号,控制,检测手册应用于控制和水压系统水压元件设计手册从非常基本的液压和机械单元应用于建造特别的的元件液压组成手册这是一个组成包括弯曲,丁字接头,弯头以及其他,它被用于典型的诸如冷却和润滑系统的低压装置第一节个别的案例注释*在液压手册里尽可能的用多余一种的流体,这是非常重要的因为你能够做出模型关于冷却和润滑系统的手册*液压手册假设一个统一的温度贯穿于整个系统,如果热量影响被考虑到很重要,热量液压和热量液压元件设计手册应该使用*有许多气穴和空气释放的模型在液压手册。
注释有一种特别的二相流体手册,一种典型的关于这种空气调节系统的装置第一节手册包括一系列个别的例子。
我们强烈的建议你认真的对待这些个别的例子。
这些假定你有一个基本的使用AMESim的水平。
作为一个完全最小的工作量你应该做些第三节关于AMESim手册的例子和第五节第一个关于描述如何使用一组的第一个例子1.2案例1:一个简单的液压系统目标*组建一个非常简单的液压系统*介绍一个简单的小管/软管子系统*解释一个结果使用一个特别的参考关于空气释放和空穴图形1.1 一个非常简单的液压系统在这个练习中你将要构造图形1.1中的系统,这可能是最简单具有意义的液压系统。
它是由部分液压种类(通常是蓝色)和部分机械种类元件建造液压部分由用于液压系统的标准符号组成。
主要的原动力提供泵的力量,从水槽拉动液压流体。
这种流体在压力下提供给一个驱动旋转负载液压马达,当压力达到某个值的时候一个解除阀门打开,一个马达和解除阀门的输出流回水槽,图标显示了三个水槽却非常像是仅仅一个水槽被利用了。
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Pneumatic Component Design LibraryRev 9 - November 2009Copyright © LMS IMAGINE S.A. 1995-2009AMESim® is the registered trademark of LMS IMAGINE S.A.AMESet® is the registered trademark of LMS IMAGINE S.A.AMERun® is the registered trademark of LMS IMAGINE S.A.AMECustom® is the registered trademark of LMS IMAGINE S.A.LMS b is a registered trademark of LMS International N.V.LMS b Motion is a registered trademark of LMS International N.V.ADAMS® is a registered United States trademark of MSC.Software Corporation.MATLAB and SIMULINK are registered trademarks of the Math Works, Inc.Modelica is a registered trademark of the Modelica Association.UNIX is a registered trademark in the United States and other countries exclusively licensed by X / Open Company Ltd.Python is a registered trademark ofthe Python Software Foundation.Windows is the registered trademark of the Microsoft Corporation.All other product names are trademarks or registered trademarks of their respective companies.TABLE OF CONTENTS1. Introduction (1)2. Tutorial examples (2)2.1. Constructing pneumatic check valves using PCD (2)2.2. Constructing a pneumatic jack using PCD (11)2.3. A 3 position 3 port pneumatic directional control valve (16)2.4. A pneumatic jack with a moving body (21)3. A Few General Rules (22)3.1. Introduction (22)3.2. Causality (22)3.3. Use of special facilities for setting parameters (23)3.4. Use of the mass dynamics blocks (24)3.5. Absolute pressure and gauge pressure (24)3.6. Setting chamber length at zero displacement (25)3.7. Interfacing with the Thermal-Pneumatic library (25)3.8. Major reconstructions (25)3.9. Using variable volume chambers (27)Using thePCD Library1. IntroductionPCD stands for Pneumatic Component Design. The PCD library enables to construct a submodel of a pneumatic component from a collection of very basic blocks. PCD greatly increases the power of AMESim pneumatic library. It is a good idea to be thoroughly familiar with the standard AMESim pneumatic library before you start using PCD.Why was it necessary to create this library? This question will be answered in this section. After this, four examples of the use of PCD are presented. In the last section a few general rules are established to enable you to use PCD effectively.The first three examples are concerned with absolute motion. It is likely that the majority of applications of PCD that you will use will fall into this category. The fourth example is concerned with relative motion. It is recommended that you reproduce the first THREE examples using AMESim.When you use AMESim, you build a model of an engineering system from a collection of components. Originally AMESim used for these components graphical symbols or icons that were based on standard representations (such as ISO symbols for pneumatic components). For an engineer working in a particular field, this makes the final system sketch look very standard and very easy to understand. However, there are two problems associated with this approach:diversity of components,diversity of skills.The diversity of components problem can be stated quite simply: ‘no matter how many components you have, it is never enough’. As an example think of a pneumatic jack. Here are some possibilitiesthe jack can have one or two pneumatic chambers,it can have one or two rods,it can incorporate one, two or zero springs.This gives 12 combinations and each would need a separate icon. Behind each icon must be at least one submodel. For many AMESim icons, one submodel is enough. In this case, we would have 12 submodels. If we consider telescopic jacks, the number of possibilities doubles. Sometimes it is useful to allow different causalities on the ports. With all the possible combinations of causality on ports there could be well over a hundred submodels of jacks.It is not possible to provide within the standard AMESim libraries huge numbers of icons and submodels. Hence only the more common component icons and submodels are provided. The expert AMESim users can of course create extensions by using AMESet to add both new icons and new submodels but at this point we encounter the second diversity problem.What skills are necessary to produce good submodels of components in AMESim or any other software? Here is a list:- an understanding of the construction and operation of the component;- an understanding of the physics governing the operation of the component;- an ability to translate the physics into a mathematical algorithm to determine theoutputs of the submodel from its inputs;- an ability to translate this algorithm into a working piece of code.Implicit within these skills are also the ability to test, debug and correct the submodel. This means that the submodel developer requires ability in engineering, physics, mathematics and computer science. This is the problem of diversity of skills. People having all these skills are relatively rare - constructing good submodels is a specialist activity.PCD was developed to overcome these diversity problems. Remember the traditional AMESim library uses symbols, where possible, based on standard ISO symbols. These symbols impose a subdivision of the model into submodels. Clearly this subdivision is not the only one possible; neither is it necessarily the best. We could use subdivision based on larger units or smaller units.PCD uses a subdivision that enables us to build the greatest number of engineering system models from the smallest number of icons and submodels. Returning to the case of the pneumatic jack, we can easily see that all possible jacks can be built up from various combinations of the following elements:- pneumatic gas under pressure- annular variable volume chamber- mechanical spring- piston generating force due to differential pressures and areasThis suggests that this is a good subdivision to use. Comparing this with subdivision based on standard ISO symbols it is clear that the basic blocks are much smaller. We could describe them as technological units since each element is a tangible object for an engineer. With most PCD icons, you could almost go to the engineering store, collect the corresponding physical objects and use them to make a component.Shopping List1 piston2 annular variable volumes2 mechanical springsWe will return to this example in the next Chapter 2 were we introduce a series of examples which progressively introduce features of PCD.2. Tutorial examples2.1. Constructing pneumatic check valves using PCDIn this section you will create the pneumatic check valvesshown in Figure 1. These components were chosen becausetheir method of working is clear, even to the non-specialist.Figure 1The standard AMESim pneumatic library already supplies submodels for these components and they are useful for general simulation of pneumatic systems. They do not include any dynamics since it is assumed they react sufficiently fast, compared with the rest of the system.Figure 2:PCD category icon Figure 3: special iconsFigure 2 the category icon for PCD is shown. The components in this category are shown in Figure 4. The first 14 components are used as for absolute motion. The three icons shown in Figure 3 are special. They are purely pneumatic components. The other components are used for relative motion. With the relative motion icons there is one body inside another and both are capable of motion. With the absolute motion icons, if there is an outer body, it is considered fixed. We will concentrate first on the absolute motion icons.Figure 4: the PCD libraryFor most of the remaining absolute motion icons there are two linear shaftports and at least one pneumatic port which supplies a pressure. Of verygreat importance is the active area on which pressure acts. The iconindicates this by the use of thicker lines or curves on the concerned part and,to make it even clearer, arrows also indicate the active area. These icons are normally joined together by their linear shaft ports to form an object which might be a spool valve, a pneumatic actuator or, as in the present case, a check valveThe most commonly used pneumatic icon is the pneumatic volume withcompressibility which is associated with a submodel which computes pneumaticpressure and temperature. This icon has provision for 4 pneumatic flow ports which receive a mass flow rate, an enthalpy flow rate, a volume and a derivative of volume. From this, the total volume, the total derivative of volume and the total inflow can be calculated. If this total inflow is positive the pressure rises, if it is negative the pressure falls.The simplest possible check valve consists in a ball which is free to move over a limited displacement. In one extreme position it is fully closed and completely blocks the flow, and in the other extreme position it is fully open. In equilibrium, the position depends on the pressures at the two pneumatic ports.Figure 5: ball poppet with sharp edge seatPCD contains two icons of a ball in a pneumatic flow path. Onehas the ball on a plain circular seat and the other on a conicalseat. A submodel associated with the plain seat icon is shown inFigure 5. Note that :- Six variables are exchanged at Pneumatic ports :T [K]Temperaturep [Pa]Pressureratedmh [J/s]flowEnthalpyrate dm[g/s]flowMassvolume dV[L/min]ofDerivativeVolume V [cm**3]- The pressure at ports is a gauge pressure in Pa. A more commonly used unit for the pressure in pneumatic system is the absolute pressure in barA (absolute pressure = gauge pressure + atmospheric pressure). Verify that the conversion from Pa to barA is selected in the menu Option ►Preferred Units ►hyd/pneu pressures and bulk modulus. All pressures will then be displayed in barA.- if the ball is in the extreme right position, the flow path will be blocked whereas if it is in the extreme left position the flow path is at its maximum opening;- the rods attached to the ball are optional and have a default diameter of zero in the submodels.s arehown in Figure 6.The ball will be subject to forces due to the pressure and, if theydo not balance, the ball will move. This means we must take intoaccount the inertia of the ball. Since the movement of the ball inthe check valve is limited, we need the icon at the right handamong the two inertia shown. Details of its external variable sFigure 6: mass with endstopsree mechanical ports, and that a submodel PNGD001 is used to define the gas properties.Figure 7 shows two possible versions of the system we are building. Each contains the check valve and two pressure and temperature sources to perform a simple test on it. Why two versions? The reason is simple. In order to make PCD as easy to use as possible, many PCD icons are associated with two submodels. Looking again at Figure 5, you will see the external variables of submodel PNAP021. The external variables of PNAP022 are a mirror image of these. You will get essentially the same results from either of these systems but, to make the example easier to follow the example, build the system shown in Figure 7(a). Note that there are zero force sources (F000) plugged in the fFigure 7: two versions of the same system In Submodels mode it is easier to set submodels by selecting Premier Submodel . However, if you set the submodel for the inertia manually, you will find there are two possible submodels which differ only in the way they treat the limitations in the displacement. These are often referred to as end stops. The two methods of modeling differ in the way they deal with the contact at an end stop :- a perfect inelastic collision with the velocity coming instantaneously to rest or- a mechanical spring and damper.Both methods are valuable but the problem with the second method is to know how to set the spring and damper rates. MAS005 uses the first method.In Parameters mode for the submodel MAS005 set the mass to 10 g (0.01 kg ), the lower displacement limit to 0 mm , the upper displacement limit to 1 mm (0.001 m ). The submodel takes the weight into account and hence an angle can be set. In our case the weight force is probably insignificant compared with the pressure force so the value set for the angle is not critical. It is probably not appropriate to set Coulomb friction and stiction. A non-zero viscous friction would make the unit more stable but in practice it is normally fully open or fully shut. Set the viscous friction to 0. The other parameters refer to Stribeck friction. This was introduced because it gives a smoother transition from stiction to Coulomb friction. Normally the Stribeck friction parameters can be left at their default value. Since we set Coulomb friction and stiction to zero they will not be effective in any case.In the submodel PNAP022 both rod diameters must be set to zero. The flow coefficient is set to a constant value of 0.72 by default , but it can be expressed as a function of the pressure ratio up downP P pr = and the poppet lift x , using a table or an expression. For sharpedge orifice, one can use for example the Perry’s flow coefficient, which can be approximated by a polynomial function of the pressure ratio :54326827.16001.49.38415.01002.08414.0pr pr pr pr pr C q −+−+−= or)cos(12.072.0pr C q ⋅⋅+=πFor this example, let this parameter to its default value. Set the seat diameter to 6mm .The total force on the ball is calculated from the pressures acting on the ball and from the external forces. The pressure force is calculated on the assumption that, referring to Figure 7(a), the right hand port pressure acts on an area adjacent to the orifice and the left hand port pressure acts on the rest of the ball. This assumption is satisfactory under most circumstances but there is provision for a correction term which is known as a jet force. This force tends to close the ball valve. A coefficient, the jet force coefficient, is used to disable or enable this term. It is defaulted to 0 to disable the term and when set to 1 will enable it computed with incompressible considerations. It can be set to other values if experimental data is available and fine-tuning of the submodel is desired.In submodels PNCS001, set the pressure to 5barA. In submodel CONS0, set the constant value to 293.15, and in submodel UD00, set a ramp from 0 to 10 in 1second and back to 0 in a further 1 second. These signals will be converted into a temperature and a pressure by submodel PNVS001. Perform a simulation over 2seconds with a communication interval equal to 0.01second. Figure 8 shows a typical plot of the mass flow rate through the check valve plotted against the differential pressure. Remember this is a dynamic submodel and the flow rate can be non-zero even when the differential pressure is negative. Even though the steady state characteristic for a particular pressure drop is for the valve to be closed, the inertia causes a ball position to lag behind the steady state position resulting in a reverse flow. Note that for similar reasons the opening and closing curves are not the same.Figure 8 mass flow rateTo get the steady-state characteristic, ramp the pressure much more slowly and increase the simulation time accordingly.Note that the ball submodels compute some volumes and derivatives of volume which are external variables at the two flow ports. The explanation of these will be deferred to the next section on pneumatic jacks where they are of great importance.Figure 9: check valve with a springNext you will add a spring (SPR000A) to convert the check valve to a spring-loaded unit. The modified system is shown in Figure 9. Attach a zero velocity source (V000) to the other port of the spring.Note that :- The spring is always in compression.- There are two ways of constructing the valve shown as (a) and (b) in the Figure9. It does not matter which side of the ball the inertia effect is positioned.However, the spring must be to the left or else it will be tending to open the valveinstead of closing it.- The spring supplies a force at both ports and so the left spring port must beclosed with a zero velocity source rather than a zero force source.We must adjust the spring rate and preload to give a desired characteristic. By appropriatechoice of these values, we can set the flow characteristic of this valve.Figure 10: external variables of SPR000AThe basic displacement and the corresponding velocity are calculated within the mass submodel MAS005. As shown in Figure 5 and Figure 6, these values are passed through the submodel PNAP021. Figure 10 shows the external variables of the spring submodel. SPR000A will accept the displacement and velocity from PNAP021, and another displacement and velocity (which are always zero) from V001.Figure 11: parameters for the springWhen setting the parameters for the spring, we will try to set a cracking pressure of 1 bar to the check valve. Set the parameters of the spring as shown on Figure 11.Figure 12: flow rate pressure characteristicRerun the simulation with the same pressure and temperature sources as in the previous example. Figure 12 shows the mass flow rate versus the differential pressure. With these parameters, the cracking pressure is about 0.7bar. The change in the slope of the curve at about 2bar is caused by the ball reaching the limit of its travel. Figure 13 shows the velocity of the ball. Note that there are signs of instability in the unit when it is partially open. (It is better to reduce the communication interval to 0.001 seconds to see this more clearly.) This can be cured by including a damping orifice.Figure 13: ball velocity2.2. Constructing a pneumatic jack using PCD(b)(a)Figure 14: standard PN jack and equivalent PCD jackIn this section we will return to pneumatic jacks discussed in the introduction. We will consider the simple jack shown in Figure 14(a). Note this has a mass included and is one of the standard AMESim pneumatic jacks. The simplest PCD construction for this is shown in Figure 14(b).Begin by constructing the double system shown in Figure 15 so that the results using PCD can be compared with those using the standard AMESim pneumatic library equivalent. Note that inertia icon has been mirrored. This gives a sign convention for displacement that is in agreement with that used in the pneumatic jack submodel PNJ011. Use the Premier Submodel to select as many submodels as possible automatically. Select the mass submodel with ideal end stops. In Parameters mode set the parameters so as to make the two systems as nearly the same as possible. This does require some care so here is a little advice.Figure 15: systems for the PN/PCD comparisonThe submodels PNAP011 and PNAP012 represent the piston and the two volumes either side of the piston. There are not two pistons but one. Each submodel deals with the pressure force on one side of the piston. The arrows and the thick line indicate the area to which the pressure is applied. Note that the mass submodel could be placed on the left or even between the two halves of the piston. The rod diameter must be set to 0 in the left submodel. In both these submodels the piston diameter must be set to 25mm to agree with the pneumatic jack submodel PNJ011. In the right submodel the rod diameter must be set to 12 mm.Note that with PCD submodels when setting parameters it can be very useful to use the following features:Global parametersCopy parametersCommon parametersThus for the diameters of pistons we could introduce a global parameter named pdiam set to 25 mm. This could then be manually set once and copied to the other submodel. Alternatively it could be set with the Common parameters facility.In PNJ011, set the mass to 100 kg , and let the stroke to its default value 0.3 m . In the mass with ideal end stops submodel MAS005 we set the mass to 100 kg , the lower limit to 0 m and the upper limit to 0.3 m .In submodel PNJ011, when the displacement of the mass is zero, the piston is at the extreme left position. This means that the length of the right pneumatic chamber is 0.3 m or 300 mm and of the left chamber is 0. Hence set the parameter labeled chamber length at zero displacement in PNPA002 to 300 mm and the corresponding parameter in PNPA001 to 0 mm.We will consider that there is no heat exchange with the exterior. To achieve that, set all parameters thermal exchange coefficient to 0.Finally, the supply pressure will be set to 7 barA , the input signal amplitude to 10 and its frequency to 1 Hz .The parameters that have to be changed are summarized in the following table:Submodel name and typeBelongs to category Main simulation parameters SIN0Sine signalsourceSignal, controls and observers sine wave amplitude = 10 PNCS001pneumaticpressure andtemperaturesourcePneumatic # pressure at port 1 = 7barA PNJ011Pneumatic total mass beeing moved = 100 kg thermal exchange coefficient = 0 J/m**2/K/s PNPA001PCD piston diameter = 25 mm rod diameter = 0 mmPNPA002PCDpiston diameter = 25 mm rod diameter = 12 mm chamber length at zero displacement = 300 mm MAS005PCD mass = 100 kg viscous friction = 0 N/(m/s) lower displacement limit = 0mhigher displacement limit = 0.3 mFigure 16 shows some typical results for the displacement.Figure 16: comparison of the displacements of PN and PCD modelsWhy are the results so different? The answer is quite simple. In the upper system (Figure 15(a)) there are DIRECT (direct connections) submodels between the valve and the jack. This means that there is no dynamics in the lines at all. This is equivalent to saying the valve is attached directly to the jack. The pressure dynamics is due solely to the pneumatic volumes within the jack and these volumes vary with the piston position. In contrast, in the lower system (Figure 15(b)), there are no pneumatic volumes within the jack but there are PNL000 pneumatic pipe submodels between the valve and the jack. These have pressure and temperature dynamics but based on a fixed volume. This assumption is clearly false, as the volumes within the jack vary as the jack moves. The lower system has therefore to be modified. It is easy to add pressure and temperature dynamics corresponding to the pneumatic volumes within the jack. Figure 17 shows the modified system.Figure 17: modified PCD jack.The crucial icon here is the pneumatic chamber which is connected to the pneumatic flow ports of the two halves of the piston. The corresponding submodel is PNCH012 and this is used to model the pressure and temperature dynamics. There are 4 ports and each requires as input an enthalpy flow in J/s, a mass flow in g/s, and also a derivative of volume in L/min and a volume in cm**3. The submodel PNCH012 sums all these 4 values. It also adds the chamber dead volume to the 4 passed volumes. From these values the derivatives of the pressure and the temperature can be calculated.The submodel can be used in complex situations involving several separate pneumatic volumes and can also accommodate leakage flows. In the current situation only 2 ports are really required and so 2 ports are plugged with the the zero enthalpy flow, mass flow, derivative of volume and volume source shown in Figure 17. Note that the chambers and the connections between the chamber and the valve are now direct.Make the changes to produce the system shown in Figure 17. Set the dead volumes in PNCH012 to 50 cm**3 to agree with the values in PNJ011.Figure 18: comparison between standard pneumatic and modified PCD models Figure 18 shows a comparison of the displacements produced using our PCD jack and PNJ011. Now the two models return the same results.You can also examine to the volumes in the two pneumatic chambers PNCH012 as shown in Figure 19.Figure 19: volumes of the two pneumatic chambersOne option that we have not yet included in our PCD jack is leakage past the piston. This is easily remedied by inserting the leakage icon between the two halves of the piston as shown in Figure 20. The corresponding submodel, PNAF011 (and its mirror image PNAF012), computes leakage flow rates which are outputs on ports 1 and 2 and in addition supplies a volume and a derivative of volume which are always zero. This means that these ports can be connected to the pneumatic chamber submodel PNCH012.The leakage flow rate is calculated based on the piston diameter, clearance, and length of piston and viscosity. A viscous friction term is also calculated.Figure 20: PCD jack with leakage flow rateWe now consider the jack shown in Figure 21. This jack is not included in the standard AMESim library . By now it should be clear that this can be constructed using the system shown in Figure 22.Figure 22: corresponding PCD model Note that with PCD submodels, it is very easy to see the assumptions on which the model is based. It is clear from Figure 22 that the pressure and temperature dynamics are taken into account, that there is leakage and that the end stops are modeled. With Figure 21, the assumptions are not clear at all.2.3. A 3 position 3 port pneumatic directional control valveFigure 23: 3 position 3 port pneumatic valve In this section you will construct a directional control valve. Figure 23 shows a 3 position 3 port unit. Note the absence of any actuating force, the unit is held in the central position by springs. If the spool moves to the left, the pressure supply P will be connected to port A . If the spool moves to the right, A is connected to tank T . If the spring is very light, even a very small applied force will open the unit fully in one direction or the other and hence the valve tends to be either in the fully open position or fully closed. A stronger spring will mean that the force required to fully open the valve is much bigger than the force required to begin opening the valve. This makes it possible to hold the valve in intermediate position neither fully open nor fully closed provided it is sufficiently stable.Figure 23 does not show any form of actuation. Units may be operated manually, electrically or by a pilot pneumatic pressure.Figure 24 shows a simple mechanical operated valve constructed using PCD .Figure 24: model of the 3 position 3 port pneumatic valveNote that:- The submodel representing the mass of the spool is placed in the center.- The two-spring/piston submodels are connected to the central chamber. Theone on the left is connected through a damping orifice.- One of the pneumatic chambers requires five flow rate/volume pairs as input. Inorder to do this a pneumatic node is attached.- A representative load is used in the form of a variable orifice.- The supply is represented by a simple temperature and pressure source PNCS001 (293.15K, 7barA).- Manual actuation is provided by a force source.Figure 25: parameters for pistons PNPA003Construct the system and set submodels using the Premier Submodel facility. Note that all the piston/spool diameters and rod diameters have consistent default values which are suitable for this example. In the mass submodel MAS005, set the mass to 50g and the lower and upper limits of displacement to -0.002m and 0.002m respectively. This gives a total movement of 4 mm and gives 0 m displacement in the central position. Set the parameters of both instances of PNPA003 to the values shown in Figure 25. Ensure the signal source connected to that variable orifice is a constant value of 1. Set the damping orifice to 1 mm2. Set the duty cycle for the actuating force to the values in Figure 26 and the pressure source to a constant value of 7 barA.。