Robust and fast visual tracking for a ball and plate control system: design, implementation and experimental verification

Abstract

The ball and plate System (BPS) is a two-dimensional electromechanical system with multiple variables, non-linearity and strong coupling. The BPS control problem is to hold the rolling ball in a specific position on the plate by adjusting the plate inclination. Ball tracking is therefore the fundamental step in BPS control, which can largely influence the control effectiveness and efficiency. The segmented path planning based on the sequential thinning algorithm is one popular tracking technology. However, it suffers from high dependence on the operating environment, complex operation and slow speed. This paper innovatively proposes a robust and fast visual tracking solution for BPS. A novel hardware structure has been designed. The sensing camera is rigidly connected to the plate, which avoids the coordinate transformation and thus reduces the complexity. In path recognition, a parallel thinning algorithm is used to improve the processing speed. Additionally, in path planning, a window searching algorithm combining the slope order matching method is proposed to establish the linked list that describes the movement path. A cascaded structure of the BPS tracking controller is also designed. Experiments have shown the effectiveness of the whole system, exhibiting shorter travelling time, smaller tracking errors as well as better stability compared to conventional systems.