Dual prescribed terminal sliding mode trajectory tracking control of a robotic arm based on extended state observer

To address the trajectory tracking control problem of robotic arm with uncertain internal models and external random disturbances, a prescribed performance and predefined-time nonsingular fast terminal sliding mode control (PPPTNFTSMC) based on a sliding mode nonlinear extended state observer (SMNESO) is proposed. Firstly, an improved prescribed performance function is proposed to transform the tracking error to satisfy the state constraint requirements of error steady-state accuracy and transient performance, which ensures that that the system tracking error always remain within predefined bounds. Then, a predefined-time nonsingular fast terminal sliding mode control (PTNFTSMC) is designed, which enables the sliding mode surface and the tracking error to achieve predefined-time convergence without relying on the initial state of the system and the controller parameters. Secondly, a SMNESO is developed using sliding mode control methods to estimate the system’s uncertain parameters and the external random disturbances in real time, thereby providing feedforward compensation for the control system. Finally, the Lyapunov stability theory is utilized to demonstrate that the trajectory tracking error can be stabilized at a predefined time while satisfying the set prescribed performance. The proposed control strategy is verified through simulations to have better dynamic and steady state performance.