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.

It has been demonstrated that magnetic fields are relevant for manipulating an untethered magnet, either using fixed coils or mobile permanent magnets. This paper shows however, that any magnetic manipulation method is prone to singular configurations and that the simple numerical analysis of the rank of the “manipulation matrix” is not enough to detect them. Alternatively, we propose a geometrical analysis to interpret and detect the singularities as well as to decide on the acceptability of a reference trajectory. Then, we present results obtained by simulating a planar manipulation system including a multiple mobile coils and a Helmholtz like set-up.

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.

Magnetic shape memory alloys (MSMA) are relatively new active materials but at this time they are not actually very used as actuators despite a high strain and a small response time. This is probably due in part to a large hysteresis and a strong non-linear behaviour. In this paper, an original hybrid control is designed taking into account dynamical effects and hysteretic behaviour in order to increase static gain of the system. After a short presentation of MSMA behaviour, a modelling is proposed to obtain two different control strategies. Some experimental results are also given.

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.