Non-singular terminal sliding mode control for redundantly actuated parallel mechanism

Haiqiang Zhang,Hairong Fang,Qi Zou

doi:10.1177/1729881420919548

Abstract

In this article, the trajectory tracking control is developed by implementing a non-singular terminal sliding mode control for the redundantly actuated parallel mechanism system. The proposed control scheme could guarantee that the tracking errors converge to zero asymptotically. The problem of singularity with regard to conventional terminal sliding mode control scheme can be eliminated with the presented novel non-singular terminal sliding mode surface as well. The corresponding stability of the proposed control scheme has also been proved theoretically in terms of Lyapunov method. In addition, simulations and experiments are conducted for trajectory tracking to validate the effectiveness of the proposed scheme. The illustrative results demonstrate that the proposed scheme is available to solve the uncertainties and external disturbances with self-tuning in real time. Furthermore, the prominent characteristics of the presented control scheme are quick convergence, high accuracy, and high robustness, which can achieve excellent tracking performance as compared with computed torque control scheme and conventional sliding mode control scheme.

Highlights

Parallel mechanisms have some inherent advantages such as high stiffness, high precision, high load-carrying capacity, high force to weight ratio, and fast response speed over alternative serial robots.[1,2] the small workspace and abundant singular configurations within the workspace limit their wide applications.[3]
The existence of singularity may be prone to get out of control so as to improve the control problem of terminal sliding mode control (TSMC); we proposed a novel non-singular terminal sliding mode control (NTSMC)
We proposed a novel NTSMC scheme to improve the tracking performance

Summary

Introduction

Parallel mechanisms have some inherent advantages such as high stiffness, high precision, high load-carrying capacity, high force to weight ratio, and fast response speed over alternative serial robots.[1,2] the small workspace and abundant singular configurations within the workspace limit their wide applications.[3]. The simulation results demonstrated that the parallel mechanism can achieve trajectory tracking control with good robustness characteristic with consideration of the uncertainties and disturbances. The main contribution of this article is to propose a novel NTSMC scheme for the redundantly actuated parallel mechanism system, with a view of achieving an excellent tracking performance in the presence of uncertainties and external disturbances. It can be observed that the above control law (15) can guarantee the sliding mode surface to converge to zero within finite time, that is, to say, e_ þ !e , m=n!0 the actual state X of the parallel mechanism system can approach the desired value Xd, that is, e % 0. NTSMC for the trajectory tracking performance, the comparative analysis compared with the computed torque control (CTC),[47] and traditional SMC48 have been implemented on the parallel mechanism system, respectively. The version sensor technology utilized in the proposed control scheme demonstrated the simplicity and significant advantages for trajectory tracking control in task space

Discussion

Conclusions