Ferdinand Schmoeckel

Flexible microrobots for micro assembly tasks

A wide range of microcomponents can today be produced using various microfabrication techniques, The assembly of complex microsystems consisting of several single components (i.e., hybrid microsystems) is, however, a difficult task that is seen to be a real challenge for the robotic research community. It is necessary to conceive flexible, highly precise and fast microassembly methods. In this paper, the development of a microrobot-based microassembly station is presented. Mobile piezoelectric microrobots with dimensions of some cm/sup 3/ and with at least 5 DOF can perform various manipulations either under a light microscope or inside the vacuum chamber of a scanning electron microscope. The components of the station developed and its control system are described. The latter comprises a vision-based sensor system for automatic robot control and user interfaces for semi-automated control and teleoperation. First results of the SEM-based micro assembly, handling of biological cells and integration of force microsensors into our microrobots are presented as well.

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

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.

Smart flexible microrobots for scanning electron microscope (SEM) applications

In the scanning electron microscope (SEM), specially designed microrobots can act as a flexible assembly facility for hybrid microsystems, as probing devices for in-situ tests on IC structures or just as a helpful teleoperated tool for the SEM operator when examining samples. Several flexible microrobots of this kind have been developed and tested. Driven by piezoactuators, these few cubic centimeters small mobile robots can perform manipulations with a precision of up to 10 nm and transport the gripped objects at speeds of up to 30 mm/s. In accuracy, flexibility and price they are superior to conventional precision robots. A new SEM-suited microrobot prototype is described in this paper. The SEM’s vacuum chamber has been equipped with various elements like flanges and CCD cameras to enable the robot to operate. In order to use the SEM image for the automatic real-time control of the robots, the SEM’s electron beam is actively controlled by a PC. The latter submits the images to the robots’ control computer system. For obtaining three-dimensional information in real time, especially for the closed-loop control of a robot endeffector, e.g., microgripper, a triangulation method with the luminescent spot of the SEM’s electron beam is being investigated.

A versatile vision system for micromanipulation tasks

Semi-autonomous and fully autonomous assembly and manipulation of micro-objects is a complex process. To this purpose, flexible microrobot systems have been designed and developed. These robots are generally required to operate in a wide range of environments to perform tasks such as microassembly, cell manipulation and particle grasping. As part of the MINIMAN project, a flexible microrobot system has been developed which can operate under a light microscope as well as in the chamber of a scanning electron microscope (SEM). This system is highly flexible, reconfigurable and uses a wide range of sensor information (force, tactile and vision) in a closed-loop controlled strategy. The paper presents an overview of the vision system and its architecture for vision-controlled micromanipulation. The different modules of the vision system and the communication interface to the control system are herewith described in detail.

The scanning electron microscope as sensor system for mobile microrobots

The presented mobile microrobots are employed inside the vacuum chamber of a scanning electron microscope (SEM). Very often more than one robot is required even for simple handling tasks due to the unfamiliar force ratios in the micro world. This paper describes how the SEM is used as a position sensor system that is a presupposition of the automatic coordination of microrobots. For depth measurements a triangulation principle with the help of the electron beam is used. First results and the required calibration methods are presented.

Kubikzentimeter-große autonome Mikroroboter für die Mikro- und Nanowelt

Um die wachsende Kluft zwischen den Mikro- und Nanotechnologien zu uberbrucken, erforscht derzeit ein europaisches Konsortium den Einsatz von mobilen, drahtlosen Kubikzentimeter-grosen Mikrorobotern, die in kleinen Gruppen zum Einsatz kommen. Die Probleme, die bei der Regelung und Sensorik fur ein solches Robotersystem zu losen sind, sind gros. Dieser Artikel beschreibt die Arbeiten der Karlsruher Forschungsgruppe im Rahmen dieses Projekts. Das Positioniersystem basiert auf einem sogenannten „mechanischen“ interferometrischen Prinzip, dem Moire-Effekt. Dieses System erreicht eine Auflosung von einem Mikrometer auf einem Arbeitsbereich von 500x500 mm2. Weitere Sensorsysteme basieren auf „Jokalen“ Kameras, welche zur Extraktion von Tiefeninforrnationen herangezogen werden. Um Bewegungsbefehle fur die Roboter zu generieren, muss das Steuerungssystem der Roboter dann in der Lage sein, die nur asynchron verfugbaren Sensordaten zu fusionieren. Hierfur wird eine zweistufige Regelungsarchitektur vorgestellt, die zwischen Grob- und Feinbewegungjedes einzelnen Roboters unterscheidet.

Das Rasterelektronenmikroskop als Sensorsystem für die Automation mobiler Mikroroboter

Die vorgestellten mobilen Mikroroboter arbeiten in der Vakuumkammer eines Rasterelektronenmikroskops. Um den ungewohnten Kraftverhaltnissen in der Mikroweit zu begegnen, ist oft auch fur einfache Handhabungsaufgaben der Einsatz zweiter Roboter notwendig. Dieser Artikel beschreibt den Einsatz des REMs als Positionssensorsystem, das Voraussetzung fur eine automatisierte Koordination der Mikroroboter ist. Zur Hohenmessung wird ein Triangulationsverfahren mit Hilfe des Elektronenstrahls eingesetzt. Es werden erste Ergebnisse und die notwendigen Kalibrierungsmethoden gezeigt.

Flexible Mobile Microrobots for Various Remote-Controlled Micro-Manipulating Tasks

Abstract The handling of objects smaller than 1 mm is a great challenge for the robotics research community. Applications are the handling of biological cells, teleoperation under vacuum conditions (e.g. inside a scanning electron microscope - SEM) or the manufacture of prototypes of microsystems. In this paper, some aspects of the control of small mobile microrobots by teleoperation are addressed. The employed 6D-mouse proves satisfactory as an intuitive user interface. A distributed control and planning architecture is presented as well as a closed-loop control approach basing on a sensor system that mainly consists of a standard SEM.