Nonlinear H2 control for position tracking of permanent magnet stepper motors

In this paper we propose nonlinear H₂ control for position tracking of permanent magnet stepper motors. The nonlinear H₂ control based on linear parameter-varying (LPV) synthesis for permanent magnet stepper motors (PMSM) is formulated to improve transient response in the position control and to reduce energy consumption. The proposed method consists of a new nonlinear torque modulation with a commutation scheme and LPV gain scheduling current controller. The position control problem for PMSMs is reformulated into the LPV system optimal problem. PMSM, nonlinear system, is analyzed as LPV systems which depend on online accessible time-varying parameters which provide real-time information. The control gain scheduling is determined using H₂ control based on linear matrix inequality (LMI) approach. Since the proposed method is designed based on optimal control with gain scheduling based on LPV synthesis, the proposed method obtains both improved transient response in the position control and reduced energy consumption. The performance of the proposed method was validated by the comparison with previous method via simulations.