Flatness-based MIMO control of hybrid stepper motors - design and implementation

Hybrid stepper motors are often used as actuators in automation and handling. To overcome their main drawbacks, step-wise motion and poor robustness against load disturbances, closed loop control can be applied. The concept of differential flatness offers powerful tools for a wide range of linear and nonlinear systems. The differential flatness property of the nonlinear MIMO model of a hybrid stepper motor is proven and a flat output is determined constructively as solution to a set of partial differential equations. By use of the flat output, an asymptotic tracking control is designed and evaluated in simulation and experiments.