Visual control of a multi-robot coupled system: Application to collision avoidance in human-robot interaction

The use of visual systems to guide robots in manipulation tasks fails when the grasping tool is close to the target, mainly due to the occlusions produced by the robot tool or by the object geometry. Moreover, the robot controller must take into account the presence of human operators within the workspace who can interact in the robot manipulation task. The scheme proposed in this paper solves this problem by using a mini-robot to locate the camera in order to observe the grasping scene without occlusions. This mini-robot is coupled at the end of a Mitsubishi PA10 manipulator (main robot). The new technical solution proposed for this scheme is composed of two parts. On the one hand, a direct hybrid visual servoing approach to control the position of the mini-robot is proposed. The hybrid behaviour of the controller permits the mini-robot to share its workspace with human operators. On the other hand, a control scheme based on a virtual camera is implemented to guide the main robot with the images acquired by the camera located at the mini-robot. Both approaches, together with the mini-robot building, are described throughout this paper.