Nadine Le Fort-Piat

Safe Task Planning Integrating Uncertainties and Local Maps Federations

This paper deals with the generation of safe tasks for displacement missions of a nonholonomic mobile robot in a mapped indoor environment. The goal of this study is to plan safe actions (path-following) as well as observations (we call it local maps federation [LMF]), leading the robot to configurations where pertinent features can be sensed, thus attaining best localization relative to its environment. A path-planning method dealing with uncertainties is proposed, where both uncertainties in localization and in control of a nonholonomic mobile robot are managed. Maps uncertainties are handled using the local map concept, which is introduced as a set of the best landmarks used for planning and executing robust motion movements. The safeness of the proposed method is due to the mixing between the planning phase and the navigation phase.

Reward function and initial values: better choices for accelerated goal-directed reinforcement learning

An important issue in Reinforcement Learning (RL) is to accelerate or improve the learning process. In this paper, we study the influence of some RL parameters over the learning speed. Indeed, although RL convergence properties have been widely studied, no precise rules exist to correctly choose the reward function and initial Q-values. Our method helps the choice of these RL parameters within the context of reaching a goal in a minimal time. We develop a theoretical study and also provide experimental justifications for choosing on the one hand the reward function, and on the other hand particular initial Q-values based on a goal bias function.

Designing Decentralized Controllers for Distributed-Air-Jet MEMS-Based Micromanipulators by Reinforcement Learning

Distributed-air-jet MEMS-based systems have been proposed to manipulate small parts with high velocities and without any friction problems. The control of such distributed systems is very challenging and usual approaches for contact arrayed system don’t produce satisfactory results. In this paper, we investigate reinforcement learning control approaches in order to position and convey an object. Reinforcement learning is a popular approach to find controllers that are tailored exactly to the system without any prior model. We show how to apply reinforcement learning in a decentralized perspective and in order to address the global-local trade-off. The simulation results demonstrate that the reinforcement learning method is a promising way to design control laws for such distributed systems.

Real-time vision-based microassembly of 3D MEMS

Robotic microassembly is a promising way to fabricate micrometric components based three dimensions (3D) compound products where the materials or the technologies are incompatible: structures, devices, Micro Electro Mechanical Systems (MEMS), Micro Opto Electro Mechanical Systems (MOEMS), etc. To date, solutions proposed in the literature are based on 2D visual control because of the lack of accurate and robust 3D measures from the work scene. In this paper the relevance of the real-time 3D visual tracking and control is demonstrated. The 3D poses of the MEMS is supplied by a model-based tracking algorithm in real-time. It is accurate and robust enough to enable a precise regulation toward zero of a 3D error using a visual servoing approach. The assembly of 400 µm × 400 µm × 100 µm parts by their 100 µm × 100 µm × 100 µm notches with a mechanical play of 3 µm is achieved with a rate of 41 seconds per assembly. The control accuracy reaches 0.3 µm in position and 0.2° in orientation.

2-DOF contactless distributed manipulation using superposition of induced air flows

Many industries require contactless transport and positioning of delicate or clean objects such as silicon wafers, glass sheets, solar cell or flat foodstuffs. The authors have presented a new form of contactless distributed manipulation using induced air flow. Previous works concerned the evaluation of the maximal velocity of transported objects and one degree-of-freedom position control of objects. This paper introduces an analytic model of the velocity field of the induced air flow according to the spatial configuration of vertical air jets. Then two degrees-of-freedom position control is investigated by exploiting the linearity property of the model. Finally the model is validated under closed-loop control and the performances of the position control are evaluated.

A new contactless conveyor system for handling clean and delicate products using induced air flows

In this paper, a new contactless conveyor system based on an original aerodynamic traction principle is described and experimented. This device is able to convey without any contact flat objects like silicon wafer, glass sheets or foodstufff thanks to an air cushion and induced air flows. A model of the system is established and the identification of the parameters is carried out. A closed-loop control is proposed for one dimension position control and position tracking. The PID-controller gives good performances for different reference signals. Its robustness to object change and perturbation rejection are also tested.

Microassembly of complex and solid 3D MEMS by 3D vision-based control

This paper describes the vision-based methods developed for assembly of complex and solid 3D MEMS (micro electromechanical systems) structures. The microassembly process is based on sequential robotic operations such as planar positioning, gripping, orientation in space and insertion tasks. Each of these microassembly tasks is performed using a pose-based visual control. To be able to control the microassembly process, a 3D model-based tracker is used. This tracker is able to directly provide the 3D micro-object pose at real-time and from only a single view of the scene. The methods proposed in this paper are validated on an automatic assembly of fives silicon microparts of 400 ¿m × 400 ¿m × 100 ¿m on 3-levels. The insertion tolerance (mechanical play) is estimated to 3 ¿m. The precision of this insertion tolerance allows us to obtain solid and complex micro electromechanical structures without any external joining (glue, wending. Promising positioning and orientation accuracies are obtained who can reach 0.3 ¿m in position and 0.2° in orientation.

Micropositioning and Fast Transport Using a Contactless Micro-Conveyor

Guillaume J. Laurent *, Anne Delettre, Rabah Zeggari, Reda Yahiaoui, Jean-Franc¸ois Manceauand Nadine Le Fort-PiatFEMTO-ST Institute, UFC-ENSMM-UTBM-CNRS, Universite de Franche-Comt´ e,´Besanc¸on 25000, France; E-Mails: anne.delettre@femto-st.fr (A.D.); rabah.zeggari@femto-st.fr (R.Z.);reda.yahiaoui@femto-st.fr (R.Y.); jfmanceau@femto-st.fr (J.-F.M.); nadine.piat@ens2m.fr (N.L.F.-P.)* Author to whom correspondence should be addressed; E-Mail: guillaume.laurent@ens2m.fr;Tel.: +33-3-8140-2808; Fax: +33-3-8140-2809.Received: 28 November 2013; in revised form: 16 December 2013 / Accepted: 6 February 2014 /Published: 12 February 2014Abstract: The micro-conveyor is a 9 9 mm

3-DOF potential air flow manipulation by inverse modeling control

Potential air flows can be used to perform non-prehensile contactless manipulations of objects gliding on air-hockey table. In this paper, we introduce a general method able to perform 3-DOF position control of an object with potential air flow manipulators. This approach is based on an inverse modeling control scheme to perform closed-loop position servoing. We propose to use a linear programming algorithm to determine which sinks have to be activated in order to produce the suitable potential air flow to obtain the desired object motion. This approach is then validated on an experimental manipulator.

Magnification-continuous static calibration model of a scanning-electron microscope

Abstract. We present a new calibration model of both static distortion and projection for a scanning-electron microscope (SEM). The proposed calibration model depends continuously on the magnification factor. State-of-the-art methods have proposed models to solve the static distortion and projection model but for a discrete set of low and high magnifications: at low magnifications, existing models assume static distortion and perspective projection. At high magnifications, existing models assume an orthogonal projection without presence of static distortion. However, a magnification-continuous model which defines continuous switch from low to high magnifications has not yet been proposed. We propose a magnification-continuous static calibration model of the SEM. The static distortion and intrinsics of the projection matrix are modeled by partial differential equations (PDEs) with respect to magnification. The approach is applied with success to the JEOL-JSM 820 in a secondary electron imaging mode for magnification ranging from 100× to 10k×. The final RMS reprojection error is about 0.9 pixels. This result together with two application-based experiments: the consistent measurements of the bending of a cantilever and a 3-D reconstruction of a nano-ball emphasize the relevance of the proposed approach.