Finite-time tracking control for robot manipulators with actuator saturation

• A saturated PD plus feedforward dynamics (SPD+) controller is proposed for finite-time tracking of robot manipulators with actuator saturation.
• The proposed controller ensures finite-time tracking stability featuring fast transient and high-precision and the actuator constraints are not violated.
• This is accomplished by selecting control gains a priori, removing the possibility of actuator failure due to excessive inputs.
• Lyapunov's direct method and finite-time stability are employed to prove semi-global finite-time tracking.
• Simulations on a three-DOF manipulator demonstrate the effectiveness and the improved performance of the proposed controller.

This paper addresses the finite-time tracking of robot manipulators in the presence of actuator saturation. The commonly-used proportional-derivative (PD) plus dynamics compensation (PD+) scheme is extended by replacing the linear errors in the PD+ scheme with saturated non-smooth but continuous exponential-like ones. Advantages of the proposed controller include semi-global finite-time tracking stability featuring faster transient and high-precision performances and the ability to ensure that actuator constraints are not violated. This is accomplished by selecting control gains a priori, removing the possibility of actuator failure due to excessive torque input levels. Lyapunov's direct method and finite-time stability are employed to prove semi-global finite-time tracking. Simulations performed on a three degree-of-freedom (DOF) manipulator are provided to illustrate the effectiveness and the improved performance of the formulated algorithm.