Robust interaction control via first and second order sliding modes of planar robotic manipulators

This paper presents an interaction control scheme for planar anthropomorphic robotic manipulators. Before starting the control phase, an a-priori trajectory is designed. The task is to follow the a-priori trajectory until a collision between the tip of the robot and an obstacle occurs. After the collision, once measured the contact force, the local properties of the obstacle surface in a vicinity of the contact point are estimated. The proposed hybrid control scheme makes the tip of the robot follow the shape of the obstacle until the goal point is reached or the a-priori trajectory is crossed so that this latter can be followed until the goal point or the next contact with the obstacle happens. Robustness to noise presence can be guaranteed by using conventional (first order) and second order sliding mode control laws. Experiments are made on a COMAU SMART3-S2 anthropomorphic rigid manipulator. They allow one to make a comparison among the three choices of the position/force controllers discussed in the paper.

I. Introduction

A fundamental topic in robotics is represented by the possibility of making easier the definition of the robot task, as well as more efficient its accomplishment, by taking into account information which may be captured by additional sensors mounted on the system or in the workspace. In the case of robotic manipulators, a typical task which can be made less critical from the definition point of view is the manufacturing in the vicinity of objects or with interaction with these latter [1]. The possible approaches to accomplish this task depend on the features of the sensors which are employed to acquire information from the environment and the obstacles near the robot [2]–[4].