Quantitative and robust direct digital control for an LBDCM driven positioning stage

The direct digital positioning control for a linear brushless DC motor (LBDCM) driven positioning stage with quantitative and robust performance is studied in this paper. An experimental LBDCM drive is first established, and its dynamic model is estimated from measurements. To handle the command tracking and load regulation position control problems simultaneously, a two-degrees-of-freedom (2DOF) position controller with cascade configuration is proposed. In making the quantitative positioning control, the discrete tracking and regulation performance transfer functions are first generated. Then the controllers of the 2DOF control scheme are designed according to the estimated dynamic model and the generated performance transfer functions. When the changes of system parameters occur, a simple robust control is added to reduce the tracking response trajectory deviation from the prescribed one, and the load regulation response can be further improved.