Event-triggered adaptive sliding mode control for robotic manipulators with disturbance compensation

In this paper, we present a trajectory tracking control for uncertain robotic manipulator systems with global robustness based on an event-triggered sliding mode strategy. In order to achieve the minimum cost of network transmission and the number of control updating instants while ensuring the global stability of the closed-loop system, we design a novel global triggering rule, which the triggering threshold is dependent on trigger parameters and sampled position tracking errors such that the sequence of the triggering instants is generated in the whole state space. Moreover, since different types of uncertain disturbances in the robotic manipulator system, the traditional sliding mode controller require a higher gain of the switching term to ensure the system performance, but it is achieved at the cost of high-frequency chattering. Therefore, we add a nonlinear disturbance observer to provide compensation for the sliding mode controller to mitigate chattering effects. We also construct an adaptive law as adaptive compensation for uncertain disturbance observing error. The robustness of the uncertain robotic system is achieved globally by using the proposed control strategy. In event-triggered control, the system cannot execute the control updating instant since Zeno behavior, which affects the stability of the system. The proposed triggering rule can ensure Zeno free execution of control inputs. Finally, a simulation is presented for a two-link robotic manipulator to verify the effectiveness of the proposed control scheme.