Some studies on SMC applied to a robotic manipulator

Robotic manipulator is a multi-input multi-output (MIMO), highly nonlinear and coupled system. Controlling this system always has been a challenging task for control engineers. In this paper, sliding mode control (SMC) technique utilizing Proportional and Derivative (PD) surface with different reaching laws has been applied on a two-link planar rigid robotic manipulator. Performance of PD sliding surface has been investigated with three different control laws namely, constant rate, exponential and power rate reaching law. Stability of the studied controller configurations have been demonstrated using Lyapunov theory. One of the major problems in SMC, “chattering” is reduced by introducing boundary layer in the controller. Genetic Algorithm optimization technique is used for tuning of parameters of SMC and boundary layer in all the cases for minimum Integral Absolute Error and chattering. Simulation results revealed that all the investigated laws performed equally for set-point tracking and the constant rate reaching law outperforms the other two laws for noise suppression. Also, all three reaching control laws of SMC offered significantly enhanced trajectory tracking and chattering performance as compared to recent literature.

I. Introduction

Robotic manipulators are extensively used in several industrial applications because of their accuracy and repeatability.Accurate positioning and tracking are the few of major challenges for robotic manipulators requiring proper control mechanism. Due tointeracting and nonlinear dynamics of the manipulator, controlling becomes a challenging task and therefore many researchers have reported various techniques for it.Different control schemes have been followed in order to cope up with these issues. Some of the recently reported techniques are advanced versions of PID controller [1], [2] and fuzzy controller [2].