Intelligent visual servoing using space variant vision with application for rehabilitation robots

Abstract

The wheelchair-based robotic arm system, which is one of rehabilitation robotic systems, consists of a powered wheelchair and a robotic arm. It has not only a mobile capability through the motorized wheelchair but also a manipulatory function with the robotic arm. Since a user and a robot are in the same environment, safe and comfortable interaction with the robots is important. It has been reported that many difficulties exist in human-robot interactions in existing rehabilitation robots. For example, manual control of the robotic arm takes a high cognitive load on the user part while physically disabled persons may have difficulties in operating joysticks dexterously or pushing buttons for delicate movements. Human-robot interaction is one of essential technologies to be developed in using the robotic system. Two factors are essential in intelligent human-robot interaction technology: one is autonomous capability of the robot, and the other is intention reading capability of the user. These factors are dealt with in the framework of visual servoing of the robotic arm.

Visual servoing is often introduced to control the pose, i.e., the position and orientation, of the end-effector of a robotic arm relative to a target using visual feedback. According to the careful analysis of predefined tasks of the wheelchair-based robotic arm, we construct the essential scenario of visual servoing, which is serving a beverage to a user including approaching the user`s face. The overall problem in our study can be described as follows: Given image sequences taken by the camera(s) of an eye-in-hand camera configuration, find the effective visual information of a single static or moving target to control the robotic arm in real-time. Specifically, visual servoing of a wheelchair-based robotic arm system usually renders many difficulties: to mention a few, it is difficult to process visual information in real-time, to be robust for varying illumination, and to process data u...