Non-minimum phase systems are difficult to understand and even difficult to tune manually. The understanding of non-minimum phase system and control strategies explain in this blog.

The response of a non-minimum phase system to a step input has an "undershoot". This means, if the output was initially zero and the steady-state output is positive, the output becomes negative before changing direction and converging to its positive steady-state value.These systemsare difficult to control due towaiting time until the initial undershoot for a positive gain system or overshoot for a negative gain system.

Steam drum is a vital part of boiler system in chemical industries. Proper and safe functioning of boiler depends on various parameters such as level of steam drum, flow of feedwater and flow of steam. The pressure, temperature and level of boiler system cannot be regulated directly but depends on the feed-water flow. The pressure or temperature in a boiler system can be maintained by controlling the flow of fuel and air whereas the level can be maintained by regulating the flow of feed water. The purpose of drum level controller is to keep the level at desired value, optimal interface level requires between steam and water within the steam drum. It is essential that the level of liquid must be low enough to assure that there is appropriate separation between steam and water and high enough to guarantee that the water exists in every steam generating tube. 

In this blog we will show the 3 most common drum level control schemes and what tuning strategy you should adopt for every strategy.