Iterative super-twisting sliding mode control: A case study on tray indexing

Continuous technological advancement in motion control enables the use of lightweight stages to achieve high precision with less development cost. However, these motion systems with higher flexible modes are rather difficult to identify accurately. Even though several methods have been addressed in the literature to approximate the model, the uncertainty and unmodeled terms will influence the performance inevitably with the use of model-based control methods. This paper presents a novel model-free control methodology to improve the position tracking performance of the lightweight motion systems and reduce the influence of uncertain flexible modes. A super-twisting sliding mode control approach is designed with an iterative learning law. A case study on the timing-belt tray indexing application is used for validation purposes. This proposed methodology is fully model-free without the need for any prior knowledge of the flexible motion systems. The potential of the proposed methodology can be further exploited and deployed in various motion control systems, especially those are difficult to obtain an accurate model.