重庆大学-过程控制-process-control-中文-翻译-第八章

Digital calculation
Digital calc.& communication
11
Practical Issues of Process Control
Digital Control: Progress in Process Control
Manual
Mechanical devices
Electronic
Simplified Diagram of Taylor transcope electronic controller
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Practical Issues of Process Control
Digital Control: Progress in Process Control
Manual
Mechanical devices
Pneumatic devices
Electronic devices
Pneumatic
Digital calculation
Digital calc.& communication
8
Practical Issues of Process Control
Process Control systems
陈刚 自动化学院
1
Practical Issues of Process Control
Outline:
Digital Control 数字控制
Progress in在……有进展 Process Control Sampling the measurement测量采样
Digital Calculation and Communication
• transmission by local network 通过本地网络传递 • sensor and valve have microprocessor微处理器
Pneumatic devices
Electronic devices
Digital Control: Progress in Process Control
Manual
Mechanical devices
Digital Calculation for Electronic Device电子设备的数字计算
Pneumatic devices
Electronic devices
3
Practical Issues of Process Control
Digital Control: Progress in Process Control控制领域的进步
Manual 手工的
Mechanical 机械的 devices
Pneumatic气动 的 devices
Electronic 电子 的devices
Use & tune various industrial PID algorithms使用&调整各种工业PID算法
Improve performance of “simple” PID 提高简单PID的性能
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Practical Issues of Process Control
Digital Control: Progress in Process Control
Digital PID calculation and execution performance 数字PID计算和执行的性能
Make PID work （in practice在实践中）
Select proper field instrumentation选择适当量程的仪表 Validate 验证and correct 调整measurements测量值
Pneumatic devices
样和计算
Electronic devices
Digital calculation
Digital calc.& communication
16
Practical Issues of Process Control
Digital Control: Sampling Times采样时间
Pneumatic devices
Electronic devices
Digital calculation
Digital calc.& communication
5
Practical Issues of Process Control
Digital Control: Progress in Process Control
The control loop控制回路 sample time
how often controller samples the process variable (PV)采样频率
compute & transmit传输 a new
controller output (p) signal
The p-PV rate, at which
Practical Issues of Process Control
Digital Control: Progress in Process Control
Distributed computing network
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Practical Issues of Process Control
Digital Control: Progress in Process Control
Digital calculation数字 计算
Digital calc.&
communication
4
Practical Issues of Process Control
Digital Control: Progress in Process Control
Manual
Mechanical devices
Aliasing欠采样: Sampling much slower than the measurement changes causes significant loss of information.采样比测量慢得多会造成重大损失的信息
Sampling slow
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Practical Issues of Process Control
Digital Control: Sampling Times
Sampling too slow: negative impact on performance
Aliasing: Sampling much slower than the measurement changes causes significant loss of information Zero-order hold零阶保持器
Manual
Mechanical devices
Pneumatic devices
Electronic devices
Digital calculation
Digital calc.& communication
6
Practical Issues of Process Control
Digital Control: Progress in Process Control
22
Practical Issues of Process Control
Practical Issues of Process Control
Digital Control: Sampling Times
Sampling too fast
（not necessarily不一定） provide better performance性能,
spend more than necessary on high-end高端 instrumentation 仪表
A rough indication of the progress in大致方面的进步在 process
control
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Practical Issues of Process Control
Digital Control: Progress in Process Control
Manual
Mechanical devices
spend more computing resources计算资源
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Practical Issues of Process Control
Digital Control: Sampling Times
“Fast and slow”
Being defined by the process time constant定义过程时间常数,
How to choose sampling time, t
Best Practice 1:
Sample time should be 10 times per process time constant or faster
采样时间应是每个过程时间常数的10倍或更快, i.e.,
t ≤ 0.1
This rule applies for应用于 both control loop sample time and bump test data collection颠簸试验数据采集are the same
Applicable for适用于 digital sampling采样 and calculation计算
• Transmission can be electronic or digital.传输可以电子的或数字的
• Measurement is periodically sampled for calcution测量是定期的采
The （steam engine蒸汽机） works all the time
control the （boiler pressure 锅炉压力） the speed of the device设备的速度
People experienced人们靠经验控制
Explosions 易爆炸 unstable behavior 不稳定 Control engineering控制工程 was born
Digital calculation
Digital calc.& communication
12
Practical Issues of Process Control
Digital Control: Progress in Process Control
Distributed computing network 分布式计算网络 13
Digital Control: Progress in Process Control
Manual
Mechanical devices
Pneumatic devices
Electronic devices
Digital calculation
Digital ቤተ መጻሕፍቲ ባይዱalc.& communication
Manual
Mechanical devices
Pneumatic
P(t)
devices
Electronic devices
Digital calculation
Digital calc.& communication
7
Practical Issues of Process Control
Digital Control: Progress in Process Control
19
Practical Issues of Process Control
Digital Control: Sampling Times
Sampling too slow: negative impact on performance Introducing介绍 dead-time
Td=T/2
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Manual
Electronic Device电子设备
Mechanical devices
Pneumatic devices
Electronic devices
Digital calculation
Digital calc.& communication
10
Practical Issues of Process Control
p-PV data are sampled and
recorded during a bump test 颠簸试验
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Practical Issues of Process Control
Digital Control: Sampling Times
Sampling too slow: negative impact on performance负面响应