Overview of microgrippers and design of a micro-manipulation station based on a MMOC microgripper

International audienceThis paper deals with an overview of recent microgrippers. As the end-effectors of micromanipulation systems, microgrippers are crucial point of such systems for their efficiency and their reliability. The performances of current microgrippers are presented and offer a stroke extending from 50 m to approximately 2mm and a maximum forces varying from 0,1mN to 600 mN. Then, micromanipulation system based on a piezoelectric microgripper and a SCARA robot is presented

Redesign of the MMOC microgripper piezoactuator using a new topological optimization method.

International audienceThis paper presents a new method developed for the optimal design of piezoactive compliant mechanisms. It is based on a flexible building blocks method, called FlexIn, which uses an evolutionary approach, to optimize a truss-like structure made of passive and active piezoelectric building blocks. An electromechanical approach, based on a mixed finite element method, is used to establish the model of the piezoelectric blocks. A planar monolithic compliant microactuator is synthetized by the optimization method, based on the specifications drawn from a piezoelectric microgripper prototype (MMOC). Finally, some performances comparisons between the optimally FlexIn synthetized gripper and the previous gripping system demonstrate the interests of the proposed optimization method for the design of microactuators, microrobots, and more generally for adaptronic structrures

Modular robotic platform for silicon micromechanical assembly.

International audienceAs no reliable methods is available to manipulate component whose typical size is up to 100μm, current industrial assembled products contained only components down to this physical limit. In that scale, micro-assembly requires specific handling strategies to overcome adhesion and high precision robots. This paper deals with an original robotic system able to perform reliable micro-assembly of silicon microobjects whose sizes are tens of micrometers. Original hybrid handling strategies between gripping and adhesion handling are proposed. An experimental robotic structure composed of micropositionning stages, videomicroscopes, piezogripper, and silicon end-effectors is presented. A modular control architecture is proposed to easily design and modify the robotic structure. Some experimental teleoperated micromanipulations and micro-assemblies have validated the proposed methods and the reliability of the principles. Future works will be focused on micro-assembly automation

Robotic Micro-assembly of microparts using a piezogripper.

International audienceThis paper deals with robotic micro-assembly of silicon micro-objects whose sizes are tens of micrometers. This production means is one of a more promising approach to realize 3D and/or hybrid microsystems. Current works in robotic micro-assembly are focused on the assembly of microobjects on a large substrate. We are focusing in the study of micro-parts assembly to build microscopic subsystems usable in larger products. This approach requires specific functionalities like a ‘micro-vise' required to block the first object during assembly. Original strategies are proposed and applied on an experimental robotic structure composed of micropositionning stages, videomicroscopes, piezogripper, and silicon endeffectors. Some experimental teleoperated micro-assemblies has validated the proposed methods and the reliability of the principles. Future works will be focused on micro-assembly automation

Overview of out of plane MEMS assembly techniques.

International audienceThis paper deals with a synthesis of the activities of the French FEMTO-ST institute in the field of robotic microassembly. It deals with the tridimensional assembly of objects whose typical size is from 10 microns to 400 microns. We are especially focusing on the automation of micro-assembly based on several principles. Closed loop control based on microvision has been studied and applied on the fully automatic assembly of several 400 microns objects. Force control has been also analyzed and is proposed for optical Microsystems assembly. At least, open loop trajectories of 40 microns objects with a throughput of 1800 unit per hour have been achieved. Scientific and technological aspects and industrial relevance will be presented

Development of novel micropneumatic grippers for biomanipulation

Microbjects with dimensions from 1 μm to 1 mm have been developed recently for different aspects and purposes. Consequently, the development of handling and manipulation tools to fulfil this need is urgently required. Micromanipulation techniques could be generally categorized according to their actuation method such as electrostatic, thermal, shape memory alloy, piezoelectric, magnetic, and fluidic actuation. Each of which has its advantage and disadvantage. The fluidic actuation has been overlooked in MEMS despite its satisfactory output in the micro-scale. This thesis presents different families of pneumatically driven, low cost, compatible with biological environment, scalable, and controllable microgrippers. The first family demonstrated a polymeric microgripper that was laser cut and actuated pneumatically. It was tested to manipulate microparticles down to 200 microns. To overcome the assembly challenges that arise in this family, the second family was proposed. The second family was a micro-cantilever based microgripper, where the device was assembled layer by layer to form a 3D structure. The microcantilevers were fabricated using photo-etching technique, and demonstrated the applicability to manipulate micro-particles down to 200 microns using automated pick-and-place procedure. In addition, this family was used as a tactile-detector as well. Due to the angular gripping scheme followed by the above mentioned families, gripping smaller objects becomes a challenging task. A third family following a parallel gripping scheme was proposed allowing the gripping of smaller objects to be visible. It comprises a compliant structure microgripper actuated pneumatically and fabricated using picosecond laser technology, and demonstrated the capability of gripping microobject as small as 100 μm microbeads. An FEA modelling was employed to validate the experimental and analytical results, and excellent matching was achieved

Improving rotation behaviour of robotic structures for micro-assembly.

International audienceSerial micro-assembly requires high precision robots able to produce translations and rotations to position and orient objects during assembly. In micro-scale, the translation ranges required are typically up to the millimeter and can be obtained with smart devices (piezomotor, etc...). In the other hand, the rotation ranges stay identical to the macroscale (eg. 90°) and require standard guidings like ball bearings which induce disturbances on the linear position. Thus, the ability to produce high precision robots where translations and rotations are découpled is currently one of the major stake in microassembly. This paper deals with an original modeling of the coupling between rotation and linear position. The geometrical model is presented and two calibration methods are discussed. Our method were tested on a 3 DOF planar robotic systems and the coupling was reduced by 93 %

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

Modeling and robust control strategy for a control-optimized piezoelectric microgripper.

International audienceIn this paper, modeling and robust control strategy for a new control-optimized piezoelectric microgripper are presented. The device to be controlled is a piezoelectric flexible mechanism dedicated to micromanipulation. It has been previously designed with an emphasis to control strategy, using a new topological optimization method, by considering innovative frequency-based criteria. A complete non-linear model relating the voltage and the resulting deflection is established taking into account hysteresis as a plurilinear model subjected to uncertainties. The approach used for controlling the actuator tip is based on a mixed High Authority Control (HAC) / Low Authority Control (LAC) strategy for designing a wide-band regulator. It consists of a Positive Position Feedback (PPF) damping controller approach combined with a low-frequency integral controller which is shown to have robustness performances as good as a RST-based robust pole placement approach for the microgripper. The rejection of the vibrations, naturally induced by the flexible structure, and the control of the tip displacement have been successfully performed. Because we had taken into account frequency-based criteria from the first designing step of our device, we demonstrate that the tuning of the HAC/LAC can be easily performed and leads to low regulator order