A unified approach to hysteretic and ramp-comparison current controllers

Sliding mode controller theory is used to develop a unified perspective on the operation of hysteretic controllers (HCs) and ramp-comparison controllers (RCCs). It is shown that additional insight into the operation and tracking ability of the conventional controllers is possible by treating them as special cases of the sliding mode based controller (SMBC) and applying sliding mode control theory. This is accomplished by resisting the HC and the RCC in terms of their operation inside and outside a boundary layer. In particular, it was shown that, with the proper choice of parameters, the SMBC and the RCC differ solely in their region of nominal operation. Whereas the RCC is typically operated within its boundary layer (linear region), the SMBC is designed for operation both inside (linear region) and outside (switched region) its boundary layer. A SMBC was developed with a performance that is superior to the conventional HC and RCC controllers. The transition between nonlinear and linear control is handled quite naturally by the SMBC. The current controller analysis is performed on a DC motor.<>