重庆大学-过程控制-process-control-中文-翻译-第五章(1)

A General SISO System 一般的单输入单输出系统
Transfer function with process model过程模型的传递函数 Signal transmitter信号变送器 Controller Actuator (control valves)执行器(控制阀)
Closed-Loop Response闭环响应
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Analysis of Single Loop Systems
PID Controllers: P-control:
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Analysis of Single Loop Systems
PID Controllers
In the sense（传感器） of proportional gain Kc
Purchasing a vlave where a lowered signal means opening the valve降 低的信号，意味着打开阀门 with the negative steady state gain (-Kv)
The controller is written as
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where I is the integral time constant (reset time)
1/I is called the reset rate, used in commercial devices 1/I被称为复位率，商用设备中使用
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Analysis of Single Loop Systems
Proportional control（比例控制） (P-control): Proportional Mode The compensation（补偿） signal (actual controller output) is proportional to（与..成比例） the error（误差）, e(t)
Analysis of Single Loop Systems
PID Controllers
e(t) = hs(t)-h(t)
P-control
The error is es=0 at t =0
The deviation variable is defined as e’(t) = e(t)-es
All commercial devices （商业设备） has positive gain
The controller output moves in the reverse direction of the controlled variable 控制器的输出向控制变量的反向变化
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Analysis of Single Loop Systemsຫໍສະໝຸດ S-Domain10
Analysis of Single Loop Systems
PID Controllers
P-control:
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Analysis of Single Loop Systems
PID Controllers
P-control:
Modern Level Sensor现代液位传感器
Seven examples Choice of controllers
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Analysis of Single Loop Systems
PID Controllers
An example
Monitoring the liquid leve in a vessel Adjusting the opening of the affluent valve 监测容器液体高度，调整阀门开度
(they are the same in SISO system)
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Analysis of Single Loop Systems
PID Controllers
An example
Objective（目的）: Keeping h at hs 维持h在hs
Situation: A sudden surge at the inlet flow qi increases h在入口流量qi骤增增 重h
PID Controllers
From practical perspective, define a new quantity 从实际应用的角度,定义一个新的量
The Proportional Band (PB)（比例范围） is the inverse of the Gain.负增益
In the sense of proportional band PB ➢ The higher PB, the slower (and more stable) control. ➢ 越高的PB，越慢越稳定的控制 ➢ The lower PB, the faster (and less stable) control.
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Analysis of Single Loop Systems
PID Controllers: PI control
PID Controllers
e(t) = hs(t)-h(t)
P-control
In the liquid level problem液位平衡问题,
if the disturbation in the inlet makes h rise over h’, thus
e < 0 p < ps
The controller output is decreased
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Analysis of Single Loop Systems
PID Controllers
The Percent Proportional Band 百分比例带 From Practical perspective:
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Analysis of Single Loop Systems
PID Controllers
where Kc is the proportional gain of the controller, determing the controller sensitivity（灵敏度）
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Analysis of Single Loop Systems
PID Controllers
P-control
The control system is saturated at the physical limits 该控制系统是饱和的物理极限
▪ Controller can only deliver（传送） so much voltage or current（电压和电流）
▪ A valve can only deliver so much fluid when fully opened ▪ 阀门完全打开只能提供了这么多1流7 体
➢The higher gain, the faster (less stable) control ➢Kc 越大，响应速度快越不稳定. ➢The lower gain, the slower (more stable) control ➢. Kc 越小，响应速度慢越稳定.
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Analysis of Single Loop Systems
Transfer function
The percent proportional band (PB)
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Analysis of Single Loop Systems
PID Controllers
P-control:
p' (t) Kce' (t)
p' (t) Kce' (t)
p' (t)
TimeDomain
PID Controllers
Proportional-integral (PI) control
Time Domain
p'(t) 1
t
e' (t )dt
I 0
p' (t)
Slope=E/I
S-Domain P(s) 1 E(s) Is
Controller Behaviour when e(t) is constant
What is the difference Compared with P-control
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Analysis of Single Loop Systems
PID Controllers: PI control
1. The integral action may overcompensate（过度补偿） (oscillation振荡), thus exhibiting the underdamped response因此展示了过阻尼响应
2. In practice, integral action is never used by itself不单独应用
3. Integral action makes the process saturation（饱和）, reset windup（积分饱和）
Integral term takes on a final nonzero value, thus Permitting（允许） es to stay at zero, as time progresses
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Analysis of Single Loop Systems
PID Controllers
An example
Defining an error signal due to the use of negative feedback 由于负反馈的使用定义一个误差信号
e(t) = hs(t)-h(t) The actual control output 实际控制输出
Qualitative features of p-control P控制器的定性特点