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