Nonsingular fast terminal second-order sliding mode for robotic manipulators based on feedback linearization

In this manuscript, a new robust nonsingular fast terminal second-order sliding mode based on input/output feedback linearization is developed for high precision joint position tracking of robotic manipulators subject to perturbations and unknown dynamics. The proposed approach reduces chattering, eliminates the problem of singularity in classical terminal sliding mode and allows fast convergence during the so-called sliding phase, which is suitable for real robot applications. Moreover, since a simple linear equivalent system is derived using feedback linearization, the design procedure doesn't require anymore the computation of the time derivative of the dynamics. Thus, the real-time implementation is simplified, and the control torque inputs that are fed into the system will not be risky for the controlled system. Simulation and experimental results are respectively conducted on a two rigid arm robot and on an industrial 7-DOF robot arm to demonstrate the effectiveness of the developed control scheme, its simplicity and superiority over other nonlinear controller based on second-order sliding mode.