Dynamic Fractional-Order Nonsingular Terminal Super-Twisting Sliding Mode Control for a Low-Cost Humanoid Manipulator

Abstract

Prosthetic humanoid manipulators manufacturing requires light overall weight, small size, compact structure, and low cost to realize wearing purpose. These requirements constrain hardware configuration conditions and aggravate the nonlinearity and coupling effects of manipulators. A dynamic fractional-order nonsingular terminal super-twisting sliding mode (DFONTSM-STA) control is proposed to realize multi-joints coordination for a low-cost humanoid manipulator. This method combines a dynamic fractional-order nonsingular terminal sliding mode (DFONTSM) manifold with the super-twisting reaching law, which can enhance the entire control performance by dynamically changing the position of the sliding mode manifold. By hiding the sign function in a higher-order term, chattering can be effectively suppressed. The stability of the low-cost humanoid manipulator system has been proven based on the Lyapunov stability theory. Experimental results show that the terminal trajectory tracking accuracy of DFONTSM-STA control was promoted by 53.3% and 23.7% respectively compared with FONTSM control and FONTSM-STA control. Thus, the DFONTSM-STA controller is superior in error convergence speed, chattering suppression, and accurate position tracking performance.

Sliding Mode Control in Dynamic Systems

“…Also, the original schemes of controllers do not need to be changed for realizing the proposed algorithms. R. Hu et al in [8] investigate coupling effects and nonlinearity in manipulators by realizing multi-joints coordination in the robot. The main objective here is to exploit the benefits offered by dynamically combining two control techniques namely; supertwisting SMC and fractional-order non-singular terminal SMC.…”