Decoupling Control of the Bearingless Induction Motor Based on Differential Geometry Variable-structure Method

A decoupling control approach based on differential geometry has been developed for the bearingless induction motor, which is multi-variable, nonlinear and high coupling system. To start with, the mathematical equations of the bearingless induction motor describing the dynamic behavior of the radial force model have been transformed. Also the state equations of the motor are set up. Secondly, the theory of differential geometry is given and the suspension spring with variable stiffness instead of conventional one is used in the model. So the nonlinear model is transferred into a linear one. Last but not least, sliding model control theory has been applied to these subsystems to obtain the desired response. The simulation results have showed that the whole control system has good dynamic and static performance.