Automated Guiding Task of a Flexible Micropart Using a Two-Sensing-Finger Microgripper.

International audienceThis paper studies automated tasks based on hybrid force/position control of a flexible object at the microscale. A guiding task of a flexible micropart is the case of the study and is achieved by a two-sensing-finger microgripper. An experimental model of the behavior of the microgripper is given and the interaction forces are studied. Based on grasp stability, a guiding strategy taking into account the pull off forces is proposed. A specific control strategy using an external hybrid force/position control and taking into account microscale specificities is proposed. The experimental results of automated guiding task are presented

Active force control for Robotic Micro-Assembly : Application to guiding tasks.

International audienceThis paper presents an analytical model and experimental results from a study of guiding tasks in microassembly. This work is focused on the use of two fingers for gripping microparts. The stability of the grasp when the contact appears is investigated and strategies during the guiding task are discussed. The contact side detection and the contact force estimation are studied. The incremental control in static mode is then investigated for controlling the guiding task. Experimental setups are proposed and some experimental results are presented

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

Automatic Microassembly of Tissue Engineering Scaffold

Ph.DDOCTOR OF PHILOSOPH

Explicit force control V.S. impedance control for micromanipulation.

International audienceThis paper presents a study of different force control schemes for controlling contact during manipulation tasks at the microscale. Explicit force control and impedance control are compared in a contact transition scenario consisting of a compliant microforce sensor mounted on a microrobotic positioner, and a compliant microstructure fabricated using Silicon MEMS. A traditional double mass-spring-damper model of the overall robot is employed to develop the closed-loop force controllers. Specific differences between the two control schemes due to the microscale nature of contact are highlighted in this paper from the experimental results obtained. The limitations and tradeoffs of the two control laws at the microscale due to the presence of backlash are discussed. A simple method to deal with the pull-off force effects specific to the microscale is proposed. Future improvements of the impedance control schemes to include adaptation are discussed in order to handle objects with unknown stiffness

Positioning accuracy characterization of assembled microscale components for micro-optical benches

International audienceThis paper deals with the measurement of microscale components' positioning accuracies used in the assembly of Micro-Optical Benches (MOB). The concept of MOB is presented to explain how to build optical MEMS based on out-of-plane micro-assembly of microcomponents. The micro-assembly platform is then presented and used to successfully assemble MOB. This micro-assembly platform includes a laser sensor that enables the measure of the microcomponent's position after its assembly. The measurement set-up and procedure is displayed and applied on several micro-assembly sets. The measurement system provides results with a maximum deviation less than +/- 0.005°. Based on this measurement system and micro-assembly procedure, the article shows that it is possible to obtain a positioning errors down to 0.009°. These results clearly state that micro-assembly is a possible way to manufacture complex, heterogeneous and 3D optical MEMS with very good optical performances

Contact force sensing and control for inserting operation during precise assembly using a micromanipulator integrated with force sensors

This paper proposes a novel contact force sensing and control method for the inserting operation during precise assembly process, which is based on a micromanipulator integrated with force sensors. At first, theoretical analysis is carried out to calculate the admissible contact force between the gripped holes and the pegs. The contact force thresholds which are smaller than the admissible contact forces are adopted in the control algorithm to avoid the rotating of the gripped holes during assembly process. The force sensors are calibrated using an ATI force sensor and the conversing coefficients are calculated. The admissible contact forces are tested when different contact distance and preload force are adopted. The performance of the proposed contact force sensing and control method is verified by carrying out the task of applying contact force on the surface of the gripped holes with different contacting speeds. The results indicate that the contact force can be adjusted to be smaller than the threshold 1 and the peg-in-hole assembly can be completed successfully. Note to Practitioners—This paper proposes a novel contact force sensing method during the inserting operation. Compared with the traditional contact force sensing method, this paper adopts the force sensor integrated into the micromanipulator instead of commercial force sensor to detect the contact force between two parts. To ensure the assembling precision, the theoretical analysis is conducted to calculated the admissible contact force to avoid the sliding and rotating of the gripped micro part during assembling. This work efficiently simplifies the contact force sensing and control process, where complex calibration process needn’t to be carried out to eliminate the influence of the mass of the micromanipulator on the testing results. In addition, the assembling costs are reduced by replacing commercial force sensors with strain gauges

Prototyping of a highly performant and integrated piezoresistive force sensor for microscale applications

International audienceIn this paper, the prototyping of a new piezoresistive microforce sensor is presented. An original design taking advantage on both mechanical and bulk piezoresistive properties of silicon is presented and enables to easily fabricate a very small, large range, high sensitivity with high integration potential sensor. The sensor is made of two silicon strain gages for which widespread and known microfabrication processes are used. The strain gages present a high gage factor which allow a good sensitivity of this force sensor. The dimensions of this sensor are 700mm in length, 100mm in width and 12mm in thickness. These dimensions make its use convenient with many microscale applications notably its integration in a microgripper. The fabricated sensor is calibrated using an industrial force sensor. The design, microfabrication process, and performances of the fabricated piezoresistive force sensor are innovative thanks to its resolution of 100nN and its measurement range of 2mN. This force sensor presents also a high signal to noise ratio, typically 50dB when a 2mN force is applied at the tip of the force sensor

Force Tracking Impedance Control with Unknown Environment at the Microscale.

International audienceA new method to estimate the environment parameters is proposed in order to perform force tracking in impedance control despite the presence of an unknown environment. In impedance force tracking, the location of the environment relative to the robot and the stiffness of the environment should be known. The proposed method estimates the environment location and stiffness using only force and position measurements. The study is done for microscale taking into consideration microscale specificities, especially pull-off force. The impedance control formulation is tested experimentally in a contact transition scenario consisting of a compliant microforce sensor mounted on a microrobotic positioner, and three compliant microstructures with different stiffness. A traditional double mass-spring-damper model of the overall robot is employed to develop the closed-loop impedance control

International Workshop on MicroFactories (IWMF 2012): 17th-20th June 2012 Tampere Hall Tampere, Finland

This Workshop provides a forum for researchers and practitioners in industry working on the diverse issues of micro and desktop factories, as well as technologies and processes applicable for micro and desktop factories. Micro and desktop factories decrease the need of factory floor space, and reduce energy consumption and improve material and resource utilization thus strongly supporting the new sustainable manufacturing paradigm. They can be seen also as a proper solution to point-of-need manufacturing of customized and personalized products near the point of need