Reference Profile Alteration and Optimization

In precision motion control systems, the 2-DOF control structure is widely utilized, but the control performance is often deteriorated due to various forms of disturbances. In prior works, it is common to compensate the disturbances by directly modifying the control input with the disturbance observer. However, in many industrial applications, such approaches may not be suitable, as the commercial controllers are often proprietary with a closed architecture. To address this practical difficulty, in this chapter, we propose a disturbance compensation scheme which alters the reference profile instead of the control input. The non-causality problem incurred by the altered reference profile is then solved by using a predictive feedforward approach. In addition, a general offsetting mechanism is developed to eliminate the effect of the prediction error within finite sampling intervals. To further enhance the performance, data-based optimization procedures are proposed. Moreover, simulations and experiments are conducted to further illustrate the effectiveness of the proposed method.