The digital microrobot, called DiMiBot, opened a new paradigm in the design of microrobots by using mechanical stability instead of complex control strategies. Current DiMiBot robots are based on the use of bistable modules to reach discrete stable positions. However, the number of stable positions depends on the number of bistable modules. As a consequence, the mechanism size increases rapidly and its miniaturization becomes complex and non-intuitive. To tackle this issue, a new multistable module has been developed to reach several stable positions within a miniaturized structure. In this paper, we focus on the reapitability and the reproducibility analysis of the developed multistable module in terms of displacement. This study is mandatory to demonstrate the effectiveness of the module as it is expected to be an elementary component of the next generation of DiMiBot. To this end, a series of experimental measurements are conducted on individual and multiple modules. The results analysis show a good agreement between the theoretical and the experimental displacements. In other words, the multistable prototype is able to reach 13 stable positions linearly in one dimensional direction with a step of about 10 μm. These capabilities open a promising perspectives and applications of this module to achieve microrobotics tasks. For example, it can be integrated in complex systems devoted to advanced tasks or accurate positioning in MEMS devices.

In this work we show that implementation of closed-loop control to silicon nanotweezers improves the sensitivity of the tool for mechanical characterization of biological molecules. Micromachined tweezers have already been used for the characterization of mechanical properties of DNA molecules [1] as well as for the sensing of enzymatic reactions on DNA bundle [2], [3]. However the resolution of the experiments does not allow the sensing on single molecules. Hereafter we show theoretically and experimentally that, reducing the resonance frequency of the system by the implementation of a state feedback, the sensitivity to stiffness variation is enhanced. Such improvement leads to better resolution for detection of enzymatic reactions on DNA [4].

Size reduction is a constant objective in new technologies for which very accurate devices are needed when manipulating submillimetric objects. A new kind of microfabricated microrobot based on the use of bistable modules is designed to perform open-loop controlled micropositioning tasks. The DiMiBot (a specific digital microrobot) opens a new paradigm in the design of microrobots by using mechanical stability instead of complex control strategies. We propose a new architecture of digital microrobot for which forward and inverse kinematics models are easy to use. These kinematic models are validated with finite-element-analysis simulations before the fabrication of a real DiMiBot prototype. Tests and characterization of the prototype are made and compared with the desired behavior. Thanks to its submicrometric resolution and to its small dimensions (~ 400-μm thickness), it is able to manipulate microobjects in confined environments, where no other robot can be used.

This paper presents a study about the effects of environmental noise on millimeter sized grippers in cantilever configuration. The study is motivated and conducted aiming at assessing the level of accuracy loss when performing micromanipulation/microassembly tasks in noisy environments as well in typical microrobotics laboratories as in industrial locations or operating rooms. Ground motion and acoustic noises within a typical microrobotic laboratory are characterized in the frequency domain and their effects on cantilevers of different lengths are inspected. The relevance of a typical vibration isolation table is evaluated and the effects of low and high acoustic noises are assessed. A modeling of a cantilever with base excitation is thereafter conducted in the state space using finite difference formulation and a stabilization of a disturbed cantilever is obtained at the nanometer level in noisy environments allowing perspectives to high precision micromanipulation tasks in hostile locations.

High precision manipulation becomes a recurrent need in micro or nanoscale. Microrobots based on active material were designed to perform micromanipulation tasks in various environments such as microrobotic stations or electronic microscopes (SEM, TEM). These active materials are used to generate proportional actuation, but show some drawbacks we want to avoid (non linearity, integration of sensors, ...). In this paper we propose a new type of microrobot, called digital microrobot. It is based on the use of bistable modules (Fig. 1), and generates a discrete workspace. This microrobot can be used in open-loop mode and gets rid of bulky and expensive instruments and sensor integration. Moreover, no external energy is required to maintain the microrobot in a given position. The study presented in this paper is dedicated to the design of the robotic structure in order to generate a desired workspace.

MEMS-based microgrippers with integrated force sensor have proved their efficiency to perform dexterous micromanipulation tasks through gripping forces sensing and control. For force control, knowledge based models are more relevant and gives better physical significance than the use of black box models. However this approach is often limited by many problems commonly encountered in the MEMS (micro electromechanical systems) structures such as: complex architectures, nonlinear behaviors and parameters uncertainties due to fabrication process at the micrometer scale. For these reasons theoretical approaches must be compared with experiments. This paper describes a modelling approach of a MEMS-based microgripper with integrated force sensor while handling micro-glass balls of 80μm diameter. Therefore, a state space representation is developed to couple both the dynamics of the actuation and sensing subsystems of the gripper through the stiffness of the manipulated object. A knowledge based model is obtained for small displacements at the tip of the gripper arms (small gripping forces) and is compared with experimental approaches. Good agreements are observed allowing interesting perspectives for the control.

Microrobots 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.

This paper deals with the description of a method for the measurement of friction force between a very small object (80 to 300 mum) and a support. The goal is to design a feeder based on controlled mechanical vibrations in order to drive microcomponents by breaking the friction force. The contact model is based on the Hertz theory and the Greenwood-Williamson multi-asperity model. The amplitude of the static friction force is measured in a clean environment with an AFM (atomic force microscope) whose cantilever is placed in the vertical position. Using this setup and the modeling, we have estimated the interfacial shear stress between the microcomponent and the support.

A new control type for stick-slip microsystems is proposed in this paper: the voltage/frequency (U/f) proportional control. It gives a best resolution relatively to the classical control algorithm. It is also an englobalization of three classical controllers: the sign controller, the classical proportional controller and the frequency proportional controller. A high stroke model of a stick-slip microsystem is first given. Then, we theoretically analyze the performances of the closed loop process with the U/f controller. Finally, we give some experimental results obtained with different values of the proportional gains.

During a micromanipulation, it is important to have the same performances whatever the manipulated object is. We present in this paper the control of the force applied to flexible and rigid micro-objects by a piezoelectric cantilever. First, the voltage-force transfer function is modeled. The hysteresis and creep phenomena are taken into account. The reliance of the model on the characteristics of the micro-objects is clearly detailed. Then, in order to reject disturbances and maintain tracking performances required in micromanipulation, a Hinfincontroller is designed. Finally, the experimental results end the paper.

First, we present a survey on modeling and control of bending piezoelectric microactuators. Second, a simple model for nonlinear piezoelectric actuators (hysteresis and creep) is presented. It is based on the multilinear approximation. This model requires low computing power and is well adapted for embedded systems. Finally, a μ-synthesis controller is implemented. Experiments show that the obtained performances are compatible with the requirements of micromanipulation tasks

This paper presents the design, the development and the experiments on a two degrees of freedom (2DoF) microsystem. The originality of the microsystem is its ability to do angular and linear motions independently with a very high stroke and a submicrometric precision. The target performances are first presented. Afterwards the stick-slip piezoelectric microactuators that are used are presented. Then, their integration inside the microsystem is detailed. Finally, results of experiments are given

In this paper, a new type of microsystem is presented : a system able to perform linear and angular motion. First, the microactuator used is studied. An approximation of the working equations is proposed in accordance with Finite-Element simulation. The microactuator used is inserted in the microsystem and a separated modelling of the whole system in linear and in angular motion is given. Stick and skid phases of each motion are independently studied.

The manipulation of very small objects is one of the most important tasks in microrobotics. Micromanipulators are required in all fields where precise manipulation of very small objects must be performed like microsurgery or assembly of MEMS. It is well known that downsizing the tools used in the macroworld is not appropriate to achieve tasks in the microworld. In this paper we present a prototype of a microgripper made up of piezoelectric bending unimorphs. A dynamic model of the piezoelectric unimorphs is developed. Various identification methods have been applied in order to verify the validity of the model. An observer has been built in order to estimate the forces applied at the tip of the fingers. Knowing these forces is very important to avoid destruction of objects during manipulation. The microgripper is able to handle microobjects in a wide range of size by changing the initial distance between the fingers. The resolution of positioning obtained is better than 10 nm for each finger. Every finger can be actuated individually so that dexterous handling can be achieved. This system allows us to perform precise micromanipulation tasks.