Sliding mode control of multi-axis leveling system based on
the reaching law of the hyperbolic secant function

Cai Wen-jie¹, Chen Shu-mei¹, Tian Shu-qing², Du Heng¹, Chen Hui¹

                                       (1. School of Mechanical Engineering and Automation, Fuzhou University, Fuzhou 350116, China;
                                       2. Fujian Haiyuan Automation Equipments Co., Ltd., Fuzhou 350101, China)

Abstract: In order to solve the problem that the control precision is not high, the sliding mode variable structure control algorithm was applied to the multi-axis leveling system. After the analysis of the unbalance mechanism, the leveling control strategy and algorithm of the multi-axis leveling system, the mathematical model of the multi-axis leveling system was established. The sliding mode variable structure control algorithm was proposed with the improvement of the index reaching law which is based on the hyperbolic secant function. The controller design method was proposed and applied to the level control of the slider. The effectiveness of the algorithm was verified by simulation analysis and experiment. The results indicate that the proposed controller can reduce the chattering and restrain the disturbance and unmodeled dynamics to improve the robustness of the system. It is simple and easy to implement to make the multi-axis leveling system fast and accurate.
Key words: multi-axis leveling system; reaching law; sliding mode variable; buffeting; robustness