Dual-channel event-triggered practical predefined-time formation controller for multi space transport robot system

This paper proposes a dual-channel event-triggered practical predefined-time formation controller (PPFC) for multi space transport robot system (MSRS) by combining sliding mode control theory with dual-channel event-triggering mechanism (ETM). Firstly, a novel practical predefined-time stability criterion is proposed in the form of composite Lyapunov function, which can simplify the determination of invariant set for practical predefined-time stable systems. Secondly, based on the criterion, a practical predefined-time sliding mode surface (PPSMF) is proposed for second-order systems, which provides a foundation for the design of PPFC. Owing to properties of the proposed PPSMF, the PPFC can reduce control inputs and avoid exponential explosion problem effectively. What is more, an independent parameter is introduced into the PPSMF, which can simplify the adjustment of convergent speed and improve the control precision of the MSRS greatly. Thirdly, in order to reduce triggering frequencies of sensors and actuators, a dual-channel ETM is proposed and integrated into the PPFC. Different form the traditional ETM, the novel ETM treats sliding variable error as a special control input error and introduces it into input channel. As a result, the input channel of the dual-channel ETM contains two different event-triggering conditions based on control input errors and sliding variable errors respectively. The proposed dual-channel ETM can help the closed-loop system to achieve a better balance between control precision and triggering frequency. Finally, simulations are provided to verify the performance of the proposed PPFC and dual-channel ETM.