Robust adaptive control for robotic manipulator based on chattering free variable structure system

In robotic manipulators there are many uncertainties such as dynamic parameters (eg., inertia and payload conditions), dynamical effects (e.g., complex nonlinear frictions), and unmodeled dynamics. Traditional linear controllers have many difficulties in treating these uncertainties. To overcome this problem, a robust adaptive control for robotic manipulator based on chattering free variable structure system is proposed. Conventional variable structure control (VSC) has important drawbacks limiting its practical applicability, such as chattering and excessive control energy. To alleviate the problems, the discontinuous part of the control signals in the conventional VSC are substituted by adaptive gain. Within this scheme, the adaptive gain are employed to approximate the unknown system´s uncertainties. The key feature of the controller is that prior knowledge of the system uncertainties is not required to guarantee the stability. Moreover, a theoretical proof of the stability and convergence of the proposed scheme using Lyapunov method is presented. To demonstrate the effectiveness of the proposed approach, a practical situation in robot control is simulated.