Abstract
A permanent magnet synchronous motor (PMSM) is a non-linear system in which the d- and q-axis systems interact with one another. Generally a state feedback control law which allows the systems to be simultaneouly decoupled and liniearised has been adopted. This paper describes a quantitative evaluation for robust stability and robust performance of an ILQ optimal current-control system including the state feedback control law for PMSMs via μ-analysis method. The μ-analysis is carried out by introducing a unique cost-function for robust performance and formulating a general servo-system which enables us to treat both ILQ and PI servo-systems evenly. By comparing with conventional PI control, it is quantitatively confirmed that the ILQ control is excellent in both robust stability and robust performance for variations of the motor parameters. The results give an extension for the robust analysis in the linearised system of the PMSM, which we had already reported.
