Control of induction motor using polytopic LPV models

A Gain scheduled control design for the stator current is presented, the approach is novel in that the gain scheduled design does not involve linearization about operating points. Instead the motor dynamics are brought to linear parameter varying form via state transformation. A linear parameter varying system is defined as a linear system whose dynamics depends on unknown but measurable exogeneous parameter. The current equations in the (α,β) frame have a particular structure, allowing to be written as an LPV system because of affine dependence of rotational speed which is taken as time varying parameter. This varying parameter values can be measured on line during control operations. The LMI based gain scheduled controller using H-infinity synthesis and polytopic representation is designed such that the robust quadratic stability and robust quadratic performance can be assured along the reference trajectory of the varying parameter.