Mechanical characterization of human oocytes holds great promise for improving the chances of pregnancy in assisted reproduction programs. However, the development of a high-performance device comes up against the numerous biological and normative constraints of medically Assisted Reproduction Technology (ART). The patented EggSense platform overcomes these difficulties and enables the mechanical characterization of human oocytes under clinical conditions. In this article, the focus is on the significant improvements achieved in EggSense by deploying advanced control techniques, based on Virtual Input Rejection COntrol (VIRCO). This approach is used to control the position of the force-sensing element in contact with the oocyte. Its implementation is fully described and experimentally validated. A comparison with a conventional controller is also provided to illustrate some of the benefits of VIRCO.

Nanoforce sensors using passive magnetic springs associated to a macroscopic seismic mass are known to be a possible alternative to force sensors based on elastic microstructures like Atomic Force Microscopes if the nanoforces that have to be measured are characterized by a bandwidth limited to a few Hertz. The estimation of the unknown force applied to the seismic mass is based on the deconvolution of the noisy measurement of the mass displacement which has an under-damped dynamic. Despite their high performances in terms of linearity, resolution and measurement range, such force sensors are extremely sensitive to low frequency environmental mechanical disturbances. They are also sensitive to the temperature evolution of the ambient air. The evaluation, modeling and compensation of such environmental disturbances have to be specifically studied in the context of magnetic springs associated to a macroscopic seismic mass. This article presents an estimation and a passive compensation strategy of the low frequency and non-stationary mechanical disturbances that is based on a differential principle. This approach is applied to a nanoforce sensor based on diamagnetic levitation developed in the last decade and gives an uncertainty below the nanonewton level.

This paper presents a new control method devoted to improve the performances of 2-DOF piezoelectric actuator for precise positioning tasks. The piezoelectric actuator exhibits strong cross-couplings between its two axes and strong hysteresis and creep nonlinearities. These unwanted phenomena undeniably compromised therefore the final precision of the targeted tasks (micromanipulation) and should be conveniently accounted during the controller synthesis. In this paper, we proposed a combination of the discrete linear Kalman filtering with a closed-loop scheme to suppress the effects of the couplings and of the nonlinearities. The suggested method permits to improve the performances of the piezoelectric actuator without specific and detailed characterization and knowledges on the hysteresis and on the creep models. Extensive experiments were carried out with complex desired trajectories and demonstrate the efficiency of the novel approach.

Nanoforce sensors based on passive diamagnetic levitation with a macroscopic seismic mass are a possible alternative to classical Atomic Force Microscopes when the force bandwidth to be measured is limited to a few Hertz. When an external unknown force is applied to the levitating seismic mass, this one acts as a transducer that converts this unknown input into a displacement that is the measured output signal. Because the inertia effect due to the mass of such macroscopic transducers can not be neglected for time-varying force measurement, it is necessary to deconvolve the displacement to correctly estimate the unknown input force. A deconvolution approach based on a Kalman filter and controlled by a scalar parameter has been recently proposed. The adjustment of this parameter leads to a trade-off that is analysed in this paper in term of resolution and bandwidth of the estimated force. Associated tools to help the end-user to set this parameter are also described.

Nano force sensors based on passive diamagnetic levitation with a macroscopic seismic mass are a possible alternative to classical Atomic Force Microscopes when the force bandwidth to be measured is limited to a few Hertz. When an external unknown force is applied to the levitating seismic mass, this one acts as a transducer that converts this unknown input into a displacement that is the measured output signal. Because the little damped and long transient response of this kind of macroscopic transducer can not be neglected, it is then necessary to deconvolve the output to correctly estimate the unknown input force. The deconvolution approach proposed in this article is based on a Kalman filter that use an uncertain a priori model to represent the unknown nanoforce to be estimated. The main advantage of this approach is that the end-user can directly control the unavoidable trade-off that exists between the wished resolution on the estimatedforce and the response time of the estimation.

In this paper, we present the design of a new magnetic nano and microforce sensor for microbiological applications. The sensing part of the sensor presents a naturally stable six degrees of freedom equilibrium state using the combination of upthrust buoyancy and magnetic force. The sensor allows force measurement without deformation of the sensing element using a feedback control loop and is able to measure the components, in the horizontal plan, of the external force applied. The measurement range varies between around plusmn100 muN with a resolution of 20 nN and a linear output. The mechanical stiffness of the passive system is about 0.018 Nm-1(same order of magnitude than an AFM micro-cantilever). A complete static study and experimental validation of the used principle are presented in this paper.

This paper presents the dynamic behaviour modelling of a horizontal triangular platform, used as the sensing part of a microforce sensor. This sensor is based on a magnetic and a buoyancy principle. A particular configuration used to obtain a linear model is presented. This linear model will be essential for the future control of the system, in order to achieve force measurement without displacement of the platform. The determination of the platform position and orientation in the horizontal plane is done thanks to three laser range sensors. Sensors configuration provide a linear transformation between the three measured ranges and the position and orientation of the platform. Finally, an open loop result comparison is done between the linear state model and a more complex 3D non linear model.

Biological research requires new tools for cell micromanipulations. Currently, biological cell sizes range from a few to hundreds of micrometers, their manipulation therefore belonging to the field of microrobotics. This paper presents a new wireless micromanipulation system which allows cells placed in a droplet of liquid to be pushed on a glass slide. The cell micropusher is a ferromagnetic object which follows the movement of a permanent magnet located under the glass slide. It has been proved in previous works that two kinds of micropusher movements can induce a movement of the pushed object: turning the micropusher around the contact point (rotation), or moving the micropusher in translation. Rotation allows an object to be placed with a precision below 1 /spl mu/m, but acts within a narrow range. Translation allows placement of an object with lower accuracy, but within a wide range. We propose a specific coarse-fine control strategy to push an object, with good precision, within a wide range. Furthermore, experimentation on polystyrene balls of 50 /spl mu/m in diameter, and immature human oocytes of 150 /spl mu/m in diameter are presented. Note to Practitioners-Biological research requires new tools for cell micromanipulations. Currently, biological cell sizes range from a few hundred micrometers; their manipulation, therefore, belongs to the field of microrobotics. This paper presents a new wireless micromanipulation system which allows cells placed in a droplet of liquid to be pushed on a glass slide. The cell micropusher is a ferromagnetic object which follows the movement of a permanent magnet located under the glass slide. It has been proven in previous works that two kinds of micropusher movements can induce a movement of the pushed object: turning the micropusher around the contact point (rotation), or moving the micropusher in translation. Rotation allows an object to be placed with a precision below 1 /spl mu/m, but acts within a narrow range. Translation allows placement of an object with lower accuracy, but within a wide range. We propose a specific coarse-fine control strategy to push an object, with good precision, within a wide range. Furthermore, experimentation on polystyrene balls of 50 /spl mu/m in diameter, and immature human oocytes of 150 /spl mu/m in diameter are presented.

This paper deals with a magnet cell transport system designed to supply test and treatment modules (e.g. units of a bio-microfactory). Our cell transport system is based on magnetic micro-actuation. Cells are pushed by a ferromagnetic microparticle (diameter 200 /spl mu/, thickness 25/spl mu/). The motion of the microparticle is performed and controlled by an external magnetic field. In this paper, we present the modelling of the pusher behavior. Our model is composed of a magnetic block (internal magnetic micropusher behaviour), strain block (torque and force applied on the micropusher by the magnet) and dynamic block (dynamic micropusher behaviour). This paper also presents some results like computation of static equilibrium position, comparison with experimental results and size influence study comparison.

Under suitable conditions, diamagnetic materials allow to achieve stable levitation of permanent magnets in entirely passive configuration. Using NdFeB magnets and diamagnetic materials such as graphite in a particular configuration, we build a passive levitated force sensor with a variable stiffness and linear output. The suspended part is used as the sensing device and two directions of force measurement are possible. The absence of friction makes the sensor highly sensitive and forces around nN can be measured. The established model of both magnetic and diamagnetic forces allows to calculate the applied force on the end point of the levitating device after measuring the position of the levitating part. This paper presents the description of the levitated sensor, force calculation and experimental results.

We present in this paper the development of a new kind of force sensing manipulator and use it to design a teleoperated micromanipulation station. The micromanipulation tasks are the two-dimensional positioning and forces interaction measurement of micrometer-size particles (50 /spl mu/m radius) in ambient condition. The manipulator used consists of a levitated glass probe with a tip of 20 /spl mu/m size. Since the levitation is achieved with totally passive approach, no control loop is then needed. Passive levitation is possible, under suitable conditions, using permanent magnets and diamagnetic materials. The established model of both magnetic and diamagnetic forces allows to calculate the applied force on the end-effector of the levitating device after measuring the position of the levitating part. The absence of friction forces and design configuration make the manipulator highly sensitive and forces around nN can be measured. This paper reports the description of the levitated sensing manipulator, model force calculation and experimental results of micromanipulation tasks.

Mechanical friction and more generally adhesion forces are some problems, which can severely limit the performances of micromechanical devices. One way to avoid friction problem, is to use levitation methods. Levitation in static magnetic field is very easy to achieve by the use of diamagnetic materials. Thus, it is possible to freely suspend a light magnet and let it in a stable equilibrium state. We have developed a prototype of a micro-nano force sensor using a passive levitation approach. This paper explains diamagnetic levitation in the simple case of a small cylindrical magnet with a mass and volume of 11 mg and 1.65 mm/sup 3/ respectively. The forces applied to the suspended magnet are presented and the natural stability of the diamagnetic levitation is explained. Finally, we present the design of our micro-nano force sensor using diamagnetic levitation.

Deals with manipulation of biological objects in an extremely confined space with a magnetic microactuator. Objects are pushed with a small magnetic particle (100/spl times/100/spl times/20 /spl mu/m/sup 3/) which is moved thanks to a permanent magnet. This device allows us to push micro-objects located in water between two glass panes. The distance between both glass panes is few hundred microns. The precision (1 /spl mu/m) is limited by the pixel size of the camera. We define the dynamic behavior of the manipulator. We also describe the control strategy used to achieve a good precision despite the "stick slip effect".

The device whose control is presented here allows to push micro-objects located in a drop of water between two glass panes. The distance between both glass panes is a few hundred micrometers. Objects are pushed with a small ferromagnetic particle whose size is 100 /spl times/ 100 /spl times/ 20 /spl mu/m/sup 3/, and which is moved thanks to a permanent magnet. The authors previously (2002) presented the dynamic behavior of this micromanipulation device. We present here an original control strategy which use the manipulator orientation to achieve a good precision despite the "stick slip effect". The position precision obtained is 1 /spl mu/m and is limited by the camera resolution.

The development of the biological research requires the implementation of new micromanipulation devices of single cell. The device presented here allows the manipulation of micro-objects where diameter varies from 20 /spl mu/m to 1 mm, in a drop of water between two glass slides. Micro-objects are moved thanks to a magnetic micromanipulator. Although magnetic force is a volumic force, we prove that it is still important in the microworld compared to adhesion forces, or weight. Magnetic micromanipulators are small nickel pieces whose sizes varies from 10 /spl times/ 10 /spl times/ 5 /spl mu/m/sup 3/ to 400 /spl times/ 400 /spl times/ 20 /spl mu/m/sup 3/. We present an original microfabrication process to fabricate and to isolate the microscopic nickel pieces.

This paper presents a reinforcement learning algorithm based on a parallel approach of the Watkins's Q-learning. This algorithm is used to control a two axis micro-manipulator system. The aim is to learn complex behaviour such as reaching target positions and avoiding obstacles at the same time. The simulations and the tests with the real manipulator show that this algorithm is able to learn simultaneously opposite behaviours and that it generates interesting action policies with regard to global path optimization.

We present a survey of fish-like propulsion at millimeter scale in order to build high efficiency swimming microrobots. We begin with a mechanical study of the fish-like propulsion. The mechanical model we used shows that undulatory motions are more efficient than oscillatory motions. We applied these theoretical results to the design and the realization of a microrobot propelled by the beating of two fins. Fins are moved by a transducer material called IPNC (ionic polymer composite metal). The experimental results allow us to check our theoretical model of the microrobot. Finally, we propose an improved microrobot which would have a better efficiency.

This paper presents an application of reinforcement learning to a block-pushing problem. The manipulator system we used is able to push millimeter size objects on a glass slide under a CCD camera. The objective is to automate high level tasks of pushing. Our approach is based on reinforcement learning algorithm (Q-learning) because the models of the manipulator and of the dynamics of objects are unknown. The system is too complex for a classic algorithm, so we propose an original architecture which realizes several learning processes at the same time. This method produces an almost optimal policy whatever the number of manipulated objects may be. Some simulations allowed us to optimize every parameter of the learning process. In particular, they show that the more objects there are, the faster the controller learns. The experimental tests show that, after the learning process, the controller fills his part perfectly.

We consider the case of a robot that must find ways in an initially unknown and often complex cross-country environment. Our approach relies on a particular model of the environment built from 3D data: the environment is represented by a hierarchical polygonal structure, in which the probabilities of terrain classes are updated as the robot moves. We describe how to define traversability costs within such a structure, taking into account the label probabilities, and explain how a shortest path search can produce a sequence of polygonal cells that must be crossed.

In order to perform occupancy grid building of in-door environmental for autonomous mobile robot, this paper presents a methodology allowing the merging of beliefs associated to hypotheses represented by binary proposition H like "this particular element belongs to this particular set". In this paper, elements processed are vectors representing points which belong to obstacles. Belief notion is introduced in the combined framework of logic and probability theory and the problem is posed as follows: if different sensors give their own belief in an hypotheses H, how is it possible to merge these believes? Two cases necessary to solve formally occupancy grid building are developed: either sensors characterize different points or sensors characterize the same point. Obtained results are applied to ultrasonic range data fusion.

In order to perform sensor-based map building of an indoor environment for autonomous mobile robots, this paper presents a methodology allowing the merging of degrees of confidence associated to beliefs represented by binary propositions. Such a belief is, by hypothesis, the membership of an element to a given set. The degree of confidence notion is introduced in the combined framework of logic and probability theory. The problem is posed as follows: if different experts give their own degrees of confidence in a belief H, how is it possible to merge these degrees? This paper develops only the case in which experts characterize different elements belonging to the same set. Obtained results are applied to ultrasonic range data fusion.