Cascade control
Цель: Изучить тему «Cascade control» и закрепить её практическими заданиями и самопроверкой.
2 акад. часа чтение и разбор теории, решение задач, работа со схемой или виртуальным стендом и проверка понимания.
Основной материал
Cascade uses primary and secondary loops. Primary controller output becomes secondary setpoint. Secondary loop must be significantly faster and measure disturbance earlier.
Heat exchanger example
Primary TIC measures outlet temperature. Its output sets steam flow SP for secondary FIC. If steam supply pressure changes, FIC corrects flow quickly before outlet temperature significantly changes.
Tuning order
Tune inner/secondary loop first. Then place it Auto/Remote and tune outer loop. Poor inner loop makes cascade worse.
Практическая работа
Draw cascade and label SP1, PV1, OUT1=SP2, PV2, OUT2. Explain why secondary should be faster.
Самопроверка
• What is cascade?
• Which loop faster?
• What becomes secondary SP?
• Why tune inner first?
• What disturbance does flow loop catch in heat exchanger?
Что нужно запомнить
- Secondary loop must be significantly faster and measure disturbance earlier.
- If steam supply pressure changes, FIC corrects flow quickly before outlet temperature significantly changes.