DESIGN OF DISCRETE TIME ADAPTIVE LEVEL CONTROL SYSTEMS

The main purpose of this Paper is to design adaptive control laws for a particular class of hydraulic systems. Considered hydraulic systems belong to a class of level systems, which were so farmostly considered with the aim of level control, i.e. keeping the level of a liquid in a reservoir at desiredconstant value. This control aim could be achieved by linear feedback gain control system. Mentioned hydraulic level-systems are now considered from a different point of view, which demands nonlinearadaptive control system introducing. Namely, if the control aim is to make the level of a liquid in areservoir change according to a specified function, then the parameters of the system under control are variable due to variable liquid level, which demands adaptive control. The case when the systemparameters are unknown is also considered. Regarding adaptive control design, different approaches wereapplied. The paper considers gradient approach (MIT rule for parameter adaptation), reference model adaptive systems based on hyper stability theory and self tuning regulators. Design procedures wereconsidered in discrete form which enables their implementation as a part of a digital system controlled bycomputer. As a result discrete control laws, which provide accomplishing of the control aim, wereobtained. Simulations were performed for different types of reference input and compared. On the basis of simulation results appropriate conclusions were made.

Keywords:

Adaptive control , hydraulic level control systems , gradient approach , reference model adaptive control , self tuning regulator