A new IM vector control scheme with two fuzzy logic controllers

This paper deals with the design of two fuzzy logic controllers (FLCs) for vector-controlled induction motor (IM) drives. Industrial vector drives employ the cascade control scheme, with four PI controllers, to improve dynamic performances. A suitable design of two FLCs permits one to achieve the performances of the cascaded control without using subordinated control loops. FLCs can operate with nonhomogeneous inputs therefore they can regulate more than one variable at the same time: the first FLC regulates both speed and stator current generating torque, the second FLC regulates both flux and stator current generating flux. Original criteria based on physical considerations, to determine the input and output gains instead of using the trial and error procedure, are presented. The simplicity of the new FLC-based scheme, together with the given design formulas, reduce the control system development time. The control scheme has been implemented on both a floating point 400 MHz Motorola PPC and on a fixed point 20 MHz Infineon C167 μcontroller. The computation power in the former case and the use of the fired-rules-hyper-cube (FRHC) approach in the latter one have allowed the μcontrollers to execute the code of two FLCs in a time comparable with that needed by four PI controllers. Details about the μcontroller implementation together with experimental results that prove the effectiveness of the novel IM vector control scheme are given.