Design, development and experiments of a high stroke-precision 2DoF (linear-angular) microsystem

International audienceThis 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

Development, modelling and control of a micro/nano positioning 2DoF stick-slip device.

International audienceThe works presented in this article are motivated by the high performances required in micromanipulation/ microassembly tasks. For that, this paper presents the developement, the modelling and the control of a 2 degrees of freedom (in linear and angular motion) micropositioning device. Based on the stick-slip motion principle, the device is characterized by unlimited strokes and submicrometric resolutions. First, experiments were carried out to characterize the performances of the micropositioning device in resolution and in speed. After that, a state-space model was developed for the sub-step functioning. Such functioning is interesting for a highly accurate task like nanopositioning. The model is validated experimentally. Finally, a controller was designed and applied to the micropositioning device. The results show good robustness margins and a response time of the closed-loop system

High-Stroke Motion Modelling and Voltage/Frequency Proportional Control of a Stick-Slip Microsystem

International audienceA 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 analyse 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

Voltage/frequency proportional control of stick-slip micropositioning systems.

International audienceA new control type for stick-slip micropositioning system is proposed in this paper : the voltage/frequency (U/f) proportional control. It gives more precise results relatively to the classical control algorithm. It is also an assembly of two classical controllers : the sign and the classical proportional controllers. A high stroke model of a stick-slip micropositioning system is first given. Then, we will theoretically analyse the performances of the closed loop process with the U/f controller. Finally, we will give some experimental results obtained with different values of the proportional gains

Data representation for the control of full-automated microfactories.

International audienceThe increase greater than ever in the developments of microproducts leads us to consider the design of an automatic, flexible, reconfigurable and upgradeable microfactory. Thus defined, the microfactory has the ability to implement an infrastructure of automated manufacture in small or average batches, and will be able to prove the feasibility of automated production in greater quantity. Two main difficulties have been identified. First, the operator in charge of the production setting has accessibility problem in the microworld. Second, the permanent adaptation of the production system to the variations of the intrinsic parameters of the microworld. Consequently, such a concept of microfactory must assist the operator by the capitalization of last experiments and the restitution of acquired know-how. Taking into account the importance and diversity of information, our approach consists in defining all this technical information system. Our method went on a modeling of the microfactory under UML, using the “use-cases” and “classes” diagrams. The technical information system resulting from our work is the spinal cord of the microfactory, it will constitute the base of the piloting structure

Towards automatic control for microfactories.

International audienceMicrofactories are new specific and flexible systems to produce and assemble micrometric products. These systems are different of standard production platforms because they are confronted with a lot of constraints without influence at human-scale systems. This approach will lead to the development of an architecture of the technical information system adapted to a modular, reconfigurable and evolutionary microfactory. In such a context of production of microproducts, the technical information system is the spinal cord of the microfactory. The definition of the data, their architecture and their organization will build up the base of the control structure. To efficiently and surely control the set of cells, the traditional control scheme must be integrated in a global information model. This paper presents the design of an information model dedicated to microfactories and its advantages

Spatially-varying multi-degree-of-freedom electromagnetic energy harvesting

This work presents the theoretical modelling of a novel spatially varying multi-degree of freedom electromagnetic vibration energy harvester(EMVEH) that integrates two novel strategies of energy harvesting - the spatial variation of the magnetic field and the design of multi-degree of freedom energy harvesters thus making a very versatile electromagnetic energy harvester model. The EMVEH models were theoretically formulated using analytical and numerical simulation and then followed by experimental validation

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

Robot Manipulators

Robot manipulators are developing more in the direction of industrial robots than of human workers. Recently, the applications of robot manipulators are spreading their focus, for example Da Vinci as a medical robot, ASIMO as a humanoid robot and so on. There are many research topics within the field of robot manipulators, e.g. motion planning, cooperation with a human, and fusion with external sensors like vision, haptic and force, etc. Moreover, these include both technical problems in the industry and theoretical problems in the academic fields. This book is a collection of papers presenting the latest research issues from around the world