Workshop on "Control issues in the micro / nano - world".

International audienceDuring the last decade, the need of systems with micro/nanometers accuracy and fast dynamics has been growing rapidly. Such systems occur in applications including 1) micromanipulation of biological cells, 2) micrassembly of MEMS/MOEMS, 3) micro/nanosensors for environmental monitoring, 4) nanometer resolution imaging and metrology (AFM and SEM). The scale and requirement of such systems present a number of challenges to the control system design that will be addressed in this workshop. Working in the micro/nano-world involves displacements from nanometers to tens of microns. Because of this precision requirement, environmental conditions such as temperature, humidity, vibration, could generate noise and disturbance that are in the same range as the displacements of interest. The so-called smart materials, e.g., piezoceramics, magnetostrictive, shape memory, electroactive polymer, have been used for actuation or sensing in the micro/nano-world. They allow high resolution positioning as compared to hinges based systems. However, these materials exhibit hysteresis nonlinearity, and in the case of piezoelectric materials, drifts (called creep) in response to constant inputs In the case of oscillating micro/nano-structures (cantilever, tube), these nonlinearities and vibrations strongly decrease their performances. Many MEMS and NEMS applications involve gripping, feeding, or sorting, operations, where sensor feedback is necessary for their execution. Sensors that are readily available, e.g., interferometer, triangulation laser, and machine vision, are bulky and expensive. Sensors that are compact in size and convenient for packaging, e.g., strain gage, piezoceramic charge sensor, etc., have limited performance or robustness. To account for these difficulties, new control oriented techniques are emerging, such as[d the combination of two or more ‘packageable' sensors , the use of feedforward control technique which does not require sensors, and the use of robust controllers which account the sensor characteristics. The aim of this workshop is to provide a forum for specialists to present and overview the different approaches of control system design for the micro/nano-world and to initiate collaborations and joint projects

Visual Servoing-Based approach for efficient autofocusing in Scanning Electron Microscope.

International audienceFast and reliable autofocusing methods are essential for performing automatic nano-objects positioning tasks using a scanning electron microscope (SEM). So far in the literature, various autofocusing algorithms have been proposed utilizing a sharpness measure to compute the best focus. Most of them are based on iterative search approaches; applying the sharpness function over the total range of focus to find an image in-focus. In this paper, a new, fast and direct method of autofocusing has been presented based on the idea of traditional visual servoing to control the focus step using an adaptive gain. The visual control law is validated using a normalized variance sharpness function. The obtained experimental results demonstrate the performance of the proposed autofocusing method in terms of accuracy, speed and robustness

Vision-based haptic feedback for remote micromanipulation in-SEM environment.

International audienceThis paper presents an intuitive environment for remote micromanipulation composed of both haptic feedback and virtual reconstruction of the scene. To enable non expert users to perform complex teleoperated micromanipulation tasks it is of utmost importance to provide them with information about the 3D relative positions of the objects and the tools. Haptic feedback is an intuitive way to transmit such information. Since position sensors are not available at this scale, visual feedback is used to derive information about the scene. In this work, three different techniques are implemented, evaluated and compared to derive the object positions from scanning electron microscope images. The modified correlation matching with generated template algorithm is accurate and provides reliable detection of objects. To track the tool, a marker based approach is chosen since fast detection is required for stable haptic feedback. Information derived from these algorithms is used to propose an intuitive remote manipulation system, that enables users situated in geographically distant sites to benefit from specific equipments such as SEMs. Stability of the haptic feedback is ensured by the minimization of the delays, the computational efficiency of vision algorithms and the proper tuning of the haptic coupling. Virtual guides are proposed to avoid any involuntary collisions between the tool and the objects. This approach is validated by a teleoperation involving melamine microspheres with a diameter of less than 2 m between Paris, France and Oldenburg, Germany

Robotic Micromanipulation and Microassembly using Mono-view and Multi-scale visual servoing.

International audienceThis paper investigates sequential robotic micromanipulation and microassembly in order to build 3-D microsystems and devices. A mono-view and multiple scale 2-D visual control scheme is implemented for that purpose. The imaging system used is a photon video microscope endowed with an active zoom enabling to work at multiple scales. It is modelled by a non-linear projective method where the relation between the focal length and the zoom factor is explicitly established. A distributed robotic system (xy system, z system) with a twofingers gripping system is used in conjunction with the imaging system. The results of experiments demonstrate the relevance of the proposed approaches. The tasks were performed with the following accuracy: 1.4 m for the positioning error, and 0.5 for the orientation error

Haptic feedback in teleoperation in Micro-and Nano-Worlds.

International audienceRobotic systems have been developed to handle very small objects, but their use remains complex and necessitates long-duration training. Simulators, such as molecular simulators, can provide access to large amounts of raw data, but only highly trained users can interpret the results of such systems. Haptic feedback in teleoperation, which provides force-feedback to an operator, appears to be a promising solution for interaction with such systems, as it allows intuitiveness and flexibility. However several issues arise while implementing teleoperation schemes at the micro-nanoscale, owing to complex force-fields that must be transmitted to users, and scaling differences between the haptic device and the manipulated objects. Major advances in such technology have been made in recent years. This chapter reviews the main systems in this area and highlights how some fundamental issues in teleoperation for micro- and nano-scale applications have been addressed. The chapter considers three types of teleoperation, including: (1) direct (manipulation of real objects); (2) virtual (use of simulators); and (3) augmented (combining real robotic systems and simulators). Remaining issues that must be addressed for further advances in teleoperation for micro-nanoworlds are also discussed, including: (1) comprehension of phenomena that dictate very small object (< 500 micrometers) behavior; and (2) design of intuitive 3-D manipulation systems. Design guidelines to realize an intuitive haptic feedback teleoperation system at the micro-nanoscale level are proposed

Characterization and control of a monolithically fabricated bistable module for microrobotic applications.

International audienceMicrorobots are widely used for microassembly and micromanipulation. However achieving performances compatible with the work in the microworld requires the use of bulky and expensive systems for measurement, signal processing and real time control. In this paper, we present the characterization and the control of a bistable module that can be used to build microrobots. This bistable module is fabricated monolithically using microfabrication technology. It offers two stable and blocked positions. High resolutions can be reached using this approach. Static and dynamic characteristics of the bistable module are studied and an open-loop control strategy is proposed in order to switch smoothly from one position to the other. The presented bistable module is the basic module for building digital microrobots

A trifocal transfer based virtual microscope for robotic manipulation of MEMS components.

International audienceThe paper deals with the problem of imaging at the microscale. The trifocal transfer based novel view synthesis approach is developed and applied to the images from two photon microscopes mounted in a stereoscopic configuration and observing vertically the work scene. The final result is a lateral virtual microscope working up to 6 frames per second with a resolution up to that of the real microscopes. Visual feedback, accurate measurements and control have been performed with, showing it ability to be used for robotic manipulation of MEMS parts. Keywords: Novel view synthesis, trifocal tensor, photon microscope, microassembly, micromanipulation, MEMS

Flexible micro-assembly system equiped with an automated tool changer.

International audienceThis paper deals with the design, fabrication and experimental validation of several modules of a micro-assembly system. On one hand, a microgripper is integrated in a four degrees of freedom system. On the other hand, a tool changer is designed. It enables to exchange automatically the tip part of the microgripper and then dedicated tools can be used to achieve specific tasks. The principle of this tool changer relies on a thermal glue whose phase (liquid or solid) is controlled by heat generators. This system is based on the modeling of thermal phenomena in the tools during a cycle of tool exchange. A compliant system is added to limit micromanipulation forces applied during assembly tasks like insertions. Finally, the successful assembly of several microcomponents is detailed, highlighting the capabilities and benefits of the whole system