Basics of Cascade Control EMEC 125 Lab 02

Basics of Cascade Control EMEC 125 – Lab 02

Basic Feedback Control • Feedback control incorporates feedback that assists in controlling a process. Disturbance Set Point + - Controller Measurement Output

Basic Concepts • Only heating is needed. • Heat provided by steam radiator and forced air. • Temperature xmitter is a conventional thermostat. • Conventional feedback. • Disturbances: • Inlet air temperature. • Flow rate of steam. • Flow rate of air in the room. • Variations of heat load in the room. • External affects. • Temperature of the radiator.

Basic Feedback Cascade Control • Cascade control is a control loop within a control loop. http: //controlguru. com/wp-content/uploads/2015/08//cas-blockdia-big. jpg http: //controlguru. com/the-cascade-control-architecture/

Basic Concepts • Only heating is needed. • Heat provided by steam radiator and forced air. • Temperature xmitter is a conventional thermostat. • Cascade control secondary loop monitors the incoming air temperture. • Disturbances: • Inlet air temperature. • Flow rate of steam. • Flow rate of air in the room. • Variations of heat load in the room.

Simple Level Feedback System • Several streams of liquid flowing into the surge tank. • Surge tank is feed into a distillation column. • Simple feedback system senses tank level and adjusts valve opening. • Disturbances can include: • Variations in inlet flow. • Changes in pressure in the distillation column. • Changes in distillation pressure cause pressure drop across the valve which affects flow.

Cascade Level Feedback System • Several streams of liquid flowing into the surge tank. • Surge tank is feed into a distillation column. • Monitors feed flow rate and can respond to changes in pressure without waiting for level changes • The flow is providing a set point for the valve and can modify the flow rate before the level change in the surge tank is detected.

References Control Guru Practical Process Control. (n. d. ). Cascade Control For Improved Disturbance Rejection. Retrieved October 27, 2016, from Control Guru Practical Process Control: http: //controlguru. com/the-cascadecontrol-architecture/: Image URL: http: //controlguru. com/wp-content/uploads/2015/08//cas-blockdiabig. jpg