Robotic micromanipulation for microassembly : modelling by sequencial function chart and achievement by multiple scale visual servoings.

International audienceThe paper investigates robotic assembly by focusing on the manipulation of microparts. This task is formalized through the notion of basic tasks which are organized in a logical sequence represented by a function chart and interpreted as the model of the behavior of the experimental setup. The latter includes a robotic system, a gripping system, an imaging system, and a clean environment. The imaging system is a photon videomicroscope able to work at multiple scales. It is modelled by a linear projective model where the relation between the scale factor and the magnification or zoom is explicitly established. So, the usual visual control law is modified in order to take into account this relation. The manipulation of some silicon microparts (400 μm×400 μm×100 μm) by means of a distributed robotic system (xyθ system, ϕz system), a two-finger gripping system and a controllable zoom and focus videomicroscope shows the relevance of the concepts. The 30 % of failure rate comes mainly from the physical phenomena (electrostatic and capillary forces) instead of the accuracy of control or the occultations of microparts

Workshop on "Robotic assembly of 3D MEMS".

Proceedings of a workshop proposed in IEEE IROS'2007.The increase of MEMS' functionalities often requires the integration of various technologies used for mechanical, optical and electronic subsystems in order to achieve a unique system. These different technologies have usually process incompatibilities and the whole microsystem can not be obtained monolithically and then requires microassembly steps. Microassembly of MEMS based on micrometric components is one of the most promising approaches to achieve high-performance MEMS. Moreover, microassembly also permits to develop suitable MEMS packaging as well as 3D components although microfabrication technologies are usually able to create 2D and "2.5D" components. The study of microassembly methods is consequently a high stake for MEMS technologies growth. Two approaches are currently developped for microassembly: self-assembly and robotic microassembly. In the first one, the assembly is highly parallel but the efficiency and the flexibility still stay low. The robotic approach has the potential to reach precise and reliable assembly with high flexibility. The proposed workshop focuses on this second approach and will take a bearing of the corresponding microrobotic issues. Beyond the microfabrication technologies, performing MEMS microassembly requires, micromanipulation strategies, microworld dynamics and attachment technologies. The design and the fabrication of the microrobot end-effectors as well as the assembled micro-parts require the use of microfabrication technologies. Moreover new micromanipulation strategies are necessary to handle and position micro-parts with sufficiently high accuracy during assembly. The dynamic behaviour of micrometric objects has also to be studied and controlled. Finally, after positioning the micro-part, attachment technologies are necessary

Automatic Microassembly System for tissue engineering- Assisted with top-view and force control

Master'sMASTER OF ENGINEERIN

A micromanipulation setup for comparative tests of microgrippers

A micromanipulation setup allowing comparative tests of manipulation micro tools has been developed. Repeatability measurements of positioning as well as optimization of manipulation conditions can be run with parts of typically 5 to 50μm over a large set of parameters including environment conditions, substrate and tip specifications, and different strategies (robot trajectories at picking and releasing time). The workstation consists of a high precise parallel robot, the Delta3, to position the gripper, linear stages to place the parts in the field of view and two microscopes for the visual feedback and position measurement. The setup is placed in a chamber for controlling relative humidity and temperature. An interface was developed to integrate every kind of tool on the robot. Automated operations and measurement have been carried out based on localization and tracking of micro objects and gripper. Integration of micro tools was successfully accomplished and comparative tests were executed with micro tweezers. Sub micrometer position repeatability was achieved with a success rate of pick and pick operations of 95%

Design and realization of a microassembly workstation

With the miniaturization of products to the levels of micrometers and the recent developments in microsystem fabrication technologies, there is a great need for an assembly process for the formation of complex hybrid microsystems. Integration of microcomponents made up of different materials and manufactured using different micro fabrication techniques is still a primary challenge since some of the fundamental problems originating from the small size of parts to be manipulated, high precision necessity and specific problems of the microworld in that field are still not fully investigated. In this thesis, design and development of an open-architecture and reconfigurable microassembly workstation for efficient and reliable assembly of micromachined parts is presented. The workstation is designed to be used as a research tool for investigation of the problems in microassembly. The development of such a workstation includes the design of: (i) a manipulation system consisting of motion stages providing necessary travel range and precision for the realization of assembly tasks, (ii) a vision system to visualize the microworld and the determination of the position and orientation of micro components to be assembled, (iii) a robust control system and necessary fixtures for the end effectors that allow easy change of manipulation tools and make the system ready for the desired task. In addition tele-operated and semi-automated assembly concepts are implemented. The design is verified by implementing tasks in various ranges for micro-parts manipulation. The versatility of the workstation is demonstrated and high accuracy of positioning is shown

Automatic Microassembly of Tissue Engineering Scaffold

Ph.DDOCTOR OF PHILOSOPH

A Review of Haptic Feedback Teleoperation Systems for Micromanipulation and Microassembly

International audienceThis paper presents a review of the major haptic feedback teleoperation systems for micromanipulation. During the last decade, the handling of micrometer-sized objects has become a critical issue. Fields of application from material science to electronics demonstrate an urgent need for intuitive and flexible manipulation systems able to deal with small-scale industrial projects and assembly tasks. Two main approaches have been considered: fully automated tasks and manual operation. The first one require fully pre determined tasks, while the later necessitates highly trained operators. To overcome these issues the use of haptic feedback teleoperation where the user manipulates the tool through a joystick whilst feeling a force feedback, appears to be a promising solution as it allows high intuitiveness and flexibility. Major advances have been achieved during this last decade, starting with systems that enable the operator to feel the substrate topology, to the current state-of-the-art where 3D haptic feedback is provided to aid manipulation tasks. This paper details the major achievements and the solutions that have been developed to propose 3D haptic feedback for tools that often lack 3D force measurements. The use of virtual reality to enhance the immersion is also addressed. The strategies developed provide haptic feedback teleoperation systems with a high degree of assistance and for a wide range of micromanipulation tools. Based on this expertise on haptic for micromanipulation and virtual reality assistance it is now possible to propose microassembly systems for objects as small as 1 to 10 micrometers. This is a mature field and will benefit small-scale industrial projects where precision and flexibility in microassembly are required

Haptic feedback in teleoperation in Micro-and Nano-Worlds.

International audienceRobotic systems have been developed to handle very small objects, but their use remains complex and necessitates long-duration training. Simulators, such as molecular simulators, can provide access to large amounts of raw data, but only highly trained users can interpret the results of such systems. Haptic feedback in teleoperation, which provides force-feedback to an operator, appears to be a promising solution for interaction with such systems, as it allows intuitiveness and flexibility. However several issues arise while implementing teleoperation schemes at the micro-nanoscale, owing to complex force-fields that must be transmitted to users, and scaling differences between the haptic device and the manipulated objects. Major advances in such technology have been made in recent years. This chapter reviews the main systems in this area and highlights how some fundamental issues in teleoperation for micro- and nano-scale applications have been addressed. The chapter considers three types of teleoperation, including: (1) direct (manipulation of real objects); (2) virtual (use of simulators); and (3) augmented (combining real robotic systems and simulators). Remaining issues that must be addressed for further advances in teleoperation for micro-nanoworlds are also discussed, including: (1) comprehension of phenomena that dictate very small object (< 500 micrometers) behavior; and (2) design of intuitive 3-D manipulation systems. Design guidelines to realize an intuitive haptic feedback teleoperation system at the micro-nanoscale level are proposed

Design, characterisation and testing of SU8 polymer based electrothermal microgrippers

Microassembly systems are designed to combine micro-component parts with high accuracy. These micro-components are fabricated using different manufacturing processes in sizes of several micrometers. This technology is essential to produce miniaturised devices and equipment, especially those built from parts requiring different fabrication procedures. The most important task in microassembly systems is the manipulator, which should have the ability to handle and control micro-particles. Different techniques have been developed to carry out this task depending on the application, required accuracy, and cost. In this thesis, the most common methods are identified and briefly presented, and some advantages and disadvantages are outlined. A microgripper is the most important device utilized to handle micro-objects with high accuracy. However, it is a device that can be used only in sequential microassembly techniques. It has the potential to become the most important tool in the field of micro-robotics, research and development, and assembly of parts with custom requirements. Different actuation mechanisms are employed to design microgrippers such as electromagnetic force, electrostatic force, piezoelectric effect, and electrothermal expansions. Also, different materials are used to fabricate these microgrippers, for example metals, silicon, and polymers such as SU-8. To investigate the limitation and disadvantages of the conventional SU-8 electrothermal based microgrippers, different devices designed and fabricated at IMT, Romania, were studied. The results of these tests showed a small end-effector displacement and short cycling on/off (lifetime). In addition, the actuator part of these microgrippers was deformed after each operation, which results in reduced displacement and inconsistent openings at off state every time it was operated in a power ON/OFF cycle. One of these limitations was caused by the existence of conductors in arms of the end-effectors. These conductor designs have two disadvantages: firstly, it raises temperature in the arms and causing an expansion in the opposite direction of the desired displacement. Secondly, since the conductors pass through the hinges, they should be designed wide enough to reduce the conductor resistance as much as possible. Therefore, the wider the hinges are, the higher the in-plane stiffness and the less out of plane deflection. As a result, it increases the reaction force of the arm reducing the effect of deformation. Based on these limitations a new actuatorstructure of L-shape was proposed to reduce the effects of these drawbacks. This actuator has no conductor in the hinges or the arms of the end-effectors which reduce limitation on the hinge width. . In addition, a further development of this actuator was proposed to increase the stiffness of the actuator by doubling its thickness compared with the other parts of the griper. The results of this actuator proved the improvement in performance and reduction of the actuator deformation. This new actuator structure was used to design several different microgrippers with large displacement and suitable for a wide range of applications. Demonstrations of the capabilities of the microgrippers to be used in microassembly are presented. In addition, a novel tri-directional microactuator is proposed in this thesis. This actuator’s end-effector is capable of displacements in three different directions. This actuator was used with the other designs to develop a novel three-arm (three fingers) multidirectional microgripper. To study the microgripper displacement as a function to the heater temperature, the TCR of the conductor layer of each device was measured. Because different configurations of conductor layers were studied, a significant effect of the metal layer structure on TCR was discovered. The TCR value of gold film is reduced significantly by adding the chromium layers below and about it which were used to improve the adhesion between the gold film and the SU layers. In this thesis, a new method based on a robotic system was developed to characterise these microgrippers and to study the steady state, dynamic response, and reliability (lifetime cycling on/off). An electronic interface was developed and integrated to the robotic system to control and drive the microgrippers. This new system was necessary to carry out automated testing of the microgrippers with accurate and reliable results. Four different new groups of microgrippers were designed and studied. The first group was indirectly actuated using an L-Shaped actuator and two different actuator widths. The initial opening was 120 μm for both designs. The maximum displacement was about 140 μm for both designs. However, the actuator in the wider heater width showed more stable behavior during the cycling and the dynamic tests. The second group was based on direct actuation approach using the L-Shaped actuator. There were eight different designs based on this method with different heater conductor shape, actuator width, and arm thickness. The initial opening was 100 μm and there were different displacements for the eight designs. The study of these microgrippers proved that the actuator stiffness has a significant effect on the microgripper displacement. In addition, the shape of the heater conductor has less effect. The largest displacement achieved using this method of design was about 70 μm. The third group was designed for dual mode operation and has three different designs. The initial openings were 90 μm and 250 μm. The displacement was about 170 μm in both modes. The last microgripper design was a tri-arm design for multi-mode operation. The lifetime study of SU8 based microgrippers in this thesis was the first time such an investigation was carried out. The results of IMT designs showed that the larger is the displacement the less stable is the gripper design because of the high rection force acting on the actuators. The L-shape based microgrippers had better performance and they did not break after more than 400 cycles. In addition, the studies of static displacement and dynamic response of different designed microgripper proved that better performance of the proposed actuator can be obtained by using double thickness for the actuator as compared to the arm thickness

Micromanipulation-force feedback pushing

In micromanipulation applications, it is often desirable to position and orient polygonal micro-objects lying on a planar surface. Pushing micro-objects using point contact provides more flexibility and less complexity compared to pick and place operation. Due to the fact that in micro-world surface forces are much more dominant than inertial forces and these forces are distributed unevenly, pushing through the center of mass of the micro-object will not yield a pure translational motion. In order to translate a micro-object, the line of pushing should pass through the center of friction. Moreover, due to unexpected nature of the frictional forces between the micro-object and substrate, the maximum force applied to the micro-object needs to be limited to prevent any damage either to the probe or micro-object. In this dissertation, a semi-autonomous manipulation scheme is proposed to push microobjects with human assistance using a custom built tele-micromanipulation setup to achieve pure translational motion. The pushing operation can be divided into two concurrent processes: In one process human operator who acts as an impedance controller to switch between force-position controllers and alters the velocity of the pusher while in contact with the micro-object through scaled bilateral teleoperation with force feedback. In the other process, the desired line of pushing for the micro-object is determined continuously so that it always passes through the varying center of friction. Visual feedback procedures are adopted to align the resultant velocity vector at the contact point to pass through the center of friction in order to achieve pure translational motion of the micro-object. Experimental results are demonstrated to prove the effectiveness of the proposed controller along with nanometer scale position control, nano-Newton range force sensing, scaled bilateral teleoperation with force feedback