重大自动化 过程控制_process_control_中文_翻译_第六章

14
Design& Tuning of Single Loop Systems
Controller settings Based on PRC
Example: What would be the PID controller settings for the
dye mixing problem?燃料混合问题
13
Design& Tuning of Single Loop Systems
Controller settings Based on PRC
Comments
on the minimum error integral (cont.)
PID controller with I=10 D=10,
Calculating计算
Minimizing极小化的
The
forms of integral积分的 error
Why so many forms?
11
Design& Tuning of Single Loop Systems
Controller settings Based on PRC
Comments Integral
Note that注意 we assume that the process is self-regulating
8
Design& Tuning of Single Loop Systems
Controller settings Based on PRC
Example:
figure belowFra Baidu bibliotek
thus, the approximation
Reminder提示:
works in reality
there is no underdamped response due to the taking
out of拿出 the controller in the step test
The
empirical relations such as Z-N, C-C, C-M, and IAE are
延迟时间模型
Systems is supposed to被期望 be self-regulating自动调节的 Dead time can approximate multi-stage process, or measuring lag延迟时间可以近似的多 阶段过程，或测量滞后
Some
tuning relations, e.g., Cohn and Coon
Process Control
College of Automaton Chongqing University 重庆大学自动化学院
1
Design &Tuning of Single Loop Systems
Outline
Tuning
controller Based on PRC基于脉冲比控制的调优控制器 Relation科恩 - 库恩的关系
The
Using
GPRC for
of the required controller if the process models are
Design
not known in advance预先
A
reduced order model降阶模型 for the product乘积 of Ga,
Gp, and Gm
Cohen-Coon
Ziegler-Nichols Relation,齐格勒 - 尼科尔斯关系、
ITAE
relation, relation
Ciancone-Marlin
Direct
Synthesis直接合成 Model Control内模控制
2
Internal
Design &Tuning of Single Loop Systems
A self-regulating multi-capacity process Step test is shown in the
一个自我调节的多容量的过程测试步骤如下图所示
Open loop test data 1st order with dead time sigmoidal form S形
1. It puts a heavy penalty on errors persisting for long periods of time 很大的误差将持续很长一段时间 1. Resulting controller allows for得到 low settling times建立时间
12
Design& Tuning of Single Loop Systems
being developed（ in term of在……方面） ¼ decay ratio衰退率 in handling disturbance
being not suitable for适合 servo problems (why?)
5
Design& Tuning of Single Loop Systems
Time constant decided by the initial slope and a visual estimation of dead time td 时间常数由最初的斜坡和目测的延迟时间TD决定
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Design& Tuning of Single Loop Systems
Controller settings Based on PRC
on the minimum error integral 积分过程(cont.)
of the absolute error绝对误差
IAE puts the equal weight重要性 to large and small error
Integral
time-weighted加权的 absolute error
the controller gains
the fitting curve拟合曲线 (empirical model经验模型)
3. ITAE relation, 4. Ciancone-Marlin relation
Following
some em pirical relations
Empirical
PID Tuning协调 trial实验
P(t)
3
Design &Tuning of Single Loop Systems
Tuning Controllers with Empirical Relations
A
practice of designing the controller settings设置
Measuring
the open loop step response, resulting in导致 PRC
6
Design& Tuning of Single Loop Systems
Controller settings Based on PRC
In
this open loop step test开环阶跃测试 lumped总的 response can be represented表现 by
an open (or closed) loop experiment
1. Cohen-Coon Relation
Making Fitting
Calculating计算
using
the system response to a model拟合模型的系统响应2. Ziegler-Nichols Relation,
Controller settings Based on PRC
Obtaining获取
Disabling
process reaction curve过程响应曲线 (PRC)
the controller
禁用控制器 Introducing
a step change to the actuator执行机构引入阶跃变化
4
Design &Tuning of Single Loop Systems
Two Remarks评论 on Empirical Tuning经验调整 Tuning relations调整关系 are based on
Fitting
open loop data to the 1st order with dead time model拟合一阶开环数据的
Solution:
Remember that we have already obtained获得
Making the open loop experiment实验 using GPRC, the well-fitted合适的 model is
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Design& Tuning of Single Loop Systems
Controller settings Based on PRC
Comments
Integral
on the minimum error integral (cont.)
of the square error平方误差
Squaring e makes it even smaller when e<1, thus 1. Suppressing抑制 the large, initial初始的 errors 2. Resulting controller tends to have a high proportional gain 3. The system is very underdamped
Example
The
(cont.):
Why does FOPDT纯滞后过程work?
real time data usually takes the sigmoidal form
S形
Process
unit operations are generally open-loop stable过程单元操作通常都是开环稳定,
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Design& Tuning of Single Loop Systems
Controller settings Based on PRC
Example
(cont.): The dye mixing problem
Because PRC does not represent the process exactly, we assume that the model has 25% errors in process 1. Gain, 2. Time constant 3. Dead time
Controller settings Based on PRC
Example
(cont.): The dye mixing problem
Cohen-Coon Tuning
However, the 1st order approximation may look like
The PID controller settings by different tuning relations
usually be used in this case这种情况下
10
Design& Tuning of Single Loop Systems
Controller settings Based on PRC
Comments
on评论 the minimum error最小误差 integral criteria 积分标准 the error by E = R-C, where C is based GPRC the error over time超时 (e.g., by Lagrange Multiplier)
Though
tuning gives a quick starting point
it doesn’t dictate system dynamic specifications尽管它不能决定系统动
态参数
It
is seldom optimal最佳的, involving包括 field tuning现场调试
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Design& Tuning of Single Loop Systems
Controller settings Based on PRC
Example:
Step
A self-regulating自调整 capacity process
test is shown in the figure below阶跃测试结果如下表