Step input analysis of turbidostat shows that the present system is highly nonlinear such that the response is dependent on starting input value, direction and magnitude of input change. Moreover, the unsteady state is very long and some-times permanently oscillatory in a sense. Thus the design of controller with classical PID control method produces somewhat oscillatory difficulties and it requires advanced digital control technique using microprocessor.
Recently adaptive control established a mathematical formulation and resulted in good performance applied to process control. Thus experiments were carried out with three algorithms : classical PID control, and ELS-STR which is representative adaptive control and SBBAC which is reformulated with adaptive technique and characteristics of this system.
The result shows that SBBAC is the best choice of three algorithms in several aspects when applied to this particular system.
