Vision-based closed-loop control of mobile microrobots for microhandling tasks

Abstract

As part of a European Union ESPRIT funded research project a flexible microrobot system has been developed which can operate under an optical microscope as well as in the chamber of a scanning electron microscope. The system is highly flexible and configurable and uses a wide range of sensors in a closed-loop control strategy. This paper presents an overview of the vision system and its architecture for vision-controlled micro-manipulation. The range of different applications, e.g. assembly of hybrid microsystems, handling of biological cells and manipulation tasks inside an SEM, imposes great demands on the vision system. Fast and reliable object recognition algorithms have been developed and implemented to provide for two modes of operation: automated and semi-automated robot control. The vision system has a modular design, comprising modules for object recognition, tracking and depth estimation. Communication between the vision modules and the control system takes place via a shared memory system embedding an object database. This database holds information about the appearance and the location of all known objects. A depth estimation method based on a modified sheet-of-light triangulation method is also described. Furthermore, the novel approach of electron beam triangulation in the SEM is described.