GPIO-Based Continuous Sliding Mode Control for Networked Control Systems Under Communication Delays with Experiments on Servo Motors

To handle input and output time delays that com-monly exist in many networked control systems (NCSs), a new robust continuous sliding mode control (CSMC) scheme is proposed for the output tracking in uncertain single input-single-out-put (SISO) networked control systems. This scheme consists of three consecutive steps. First, although the network-induced delay in those systems can be effectively handled by using Pade approximation (PA), the unmatched disturbance cames out as another difficulty in the control design. Second, to actively estimate this unmatched disturbance, a generalized proportional integral observer (GPIO) technique is utilized based on only one measured state. Third, by constructing a new sliding manifold with the aid of the estimated unmatched disturbance and states, a GPIO-based CSMC is synthesized, which is employed to cope with not only matched and unmatched disturbances, but also net-work-induced delays. The stability of the entire closed-loop system under the proposed GPIO-based CSMC is detailedly analyzed. The promising tracking efficiency and feasibility of the proposed control methodology are verified through simulations and experiments on Quanser's servo module for motion control under various test conditions.