上海交通大学：《自动化仪表与过程控制》课程学习资料——过程控制的基本概念 Process Control

Chapter 1 Process Control Li Shaoyuan E-mail:syli@sjtu.edu.cn

Chapter 1 Process Control Li Shaoyuan E-mail: syli@sjtu.edu.cn

Basic concepts

Basic Concepts

Control of industrial process

Control of Industrial Process

Temperature control of steam Heating Transmitter Controller vPCurrent-to-pressure Ps — Steam temperature controller set-point valve stirred Tank (pressure) Transducer Thermocouple

Temperature control of Steam Heating

emperature control of Electric Heating Thermocouple Heater L L 2Controller Heater人 Process B Thermocouple and Transmitter

Temperature control of Electric Heating

Level control an L℃ h Liquid-level control systen

Level Control

Closed-Loop Transfer Functions R≠0L=0 R=0L≠0 Set point change, load is constant oad change, constant set point C(s) KmGG Gp R(s 1+GCGYGPGM L(S) 1+GCGGPG

Closed-Loop Transfer Functions R  0 L  0 ( ) ( ) 1 M C V P C V P M C s K G G G R s G G G G   Set point change, load is constant Load change, constant set point R  0 L  0 ( ) ( ) 1 L C V P M C s G L s G G G G  

PId Control

PID Control

Why pid control ° Simple, easy to use Wide application: Petrochemical, Pharmaceuticals, Food, Chemical. Aerospace and Semiconductor, etc Robust: Insensitive to changes to plant parameter and disturbance Over 90% control loops are pid with two exceptions 1. On/off control for those with low control requirement loops 2. Advanced control for those difficult systems and with high control quality

• Simple, easy to use • Wide Application: Petrochemical, Pharmaceuticals, Food, Chemical, Aerospace and Semiconductor, etc. • Robust: Insensitive to changes to plant parameter and disturbance. Why PID Control Over 90% control loops are PID with two exceptions: 1. On/off control for those with low control requirement loops 2. Advanced control for those difficult systems and with high control quality

Proportional function The controller output u is proportional to error signal e K where 8 is proportional band P control has steady state error

u K e e c  1    Proportional Function The controller output u is proportional to error signal e: where is proportional band P control has steady state error