Microassembly for complex and solid 3D MEMS by 3D Vision-based control.

International audienceThis paper describes the vision-based methods developed for assembly of complex and solid 3D MEMS (micro electromechanical systems) structures. The microassembly process is based on sequential robotic operations such as planar positioning, gripping, orientation in space and insertion tasks. Each of these microassembly tasks is performed using a posebased visual control. To be able to control the microassembly process, a 3D model-based tracker is used. This tracker able to directly provides the 3D micro-object pose at real-time and from only a single view of the scene. The methods proposed in this paper are validated by an automatic assembly of fives silicon microparts of 400 µm 400 µm 100 µm on 3- levels. The insertion tolerance (mechanical play) is estimated to 3 µm. The weakness of this insertion tolerance allows to obtain solid and complex micro electromechanical structures without any external joining (glue, wending). Promising positioning and orientation accuracies are obtained who can reach 0.3 µm in position and 0.2° in orientation

Affordable flexible hybrid manipulator for miniaturised product assembly

Miniaturised assembly systems are capable of assembling parts of a few millimetres in size with an accuracy of a few micrometres. Reducing the size and the cost of such a system while increasing its flexibility and accuracy is a challenging issue. The introduction of hybrid manipulation, also called coarse/fine manipulation, within an assembly system is the solution investigated in this thesis. A micro-motion stage (MMS) is designed to be used as the fine positioning mechanism of the hybrid assembly system. MMSs often integrate compliant micro-motion stages (CMMSs) to achieve higher performances than the conventional MMSs. CMMSs are mechanisms that transmit an output force and displacement through the deformation of their structure. Although widely studied, the design and modelling techniques of these mechanisms still need to be improved and simplified. Firstly, the linear modelling of CMMSs is evaluated and two polymer prototypes are fabricated and characterised. It is found that polymer based designs have a low fabrication cost but not suitable for construction of a micro-assembly system. A simplified nonlinear model is then derived and integrated within an analytical model, allowing for the full characterisation of the CMMS in terms of stiffness and range of motion. An aluminium CMMS is fabricated based on the optimisation results from the analytical model and is integrated within an MMS. The MMS is controlled using dual-range positioning to achieve a low-cost positioning accuracy better than 2µm within a workspace of 4.4×4.4mm2. Finally, a hybrid manipulator is designed to assemble mobile-phone cameras and sensors automatically. A conventional robot manipulator is used to pick and place the parts in coarse mode while the aluminium CMMS based MMS is used for fine alignment of the parts. A high-resolution vision system is used to locate the parts on the substrate and to measure the relative position of the manipulator above MMS using a calibration grid with square patterns. The overall placement accuracy of the assembly system is ±24µm at 3σ and can reach 2µm, for a total cost of less than £50k, thus demonstrating the suitability of hybrid manipulation for desktop-size miniaturised assembly systems. The precision of the existing system could be significantly improved by making the manipulator stiffer (i.e. preloaded bearings…) and adjustable to compensate for misalignment. Further improvement could also be made on the calibration of the vision system. The system could be either scaled up or down using the same architecture while adapting the controllers to the scale.Engineering and Physical Sciences Research Council (EPSRC

Microassembly for complex and solid 3D MEMS by 3D Vision-based control. Microassembly of Complex and Solid 3D MEMS by 3D Vision-based Control

To cite this version: Brahim Tamadazte, Nadine Le Fort-Piat, Eric Marchand, Sounkalo Dembélé. Abstract-This paper describes the vision-based methods developed for assembly of complex and solid 3D MEMS (micro electromechanical systems) structures. The microassembly process is based on sequential robotic operations such as planar positioning, gripping, orientation in space and insertion tasks. Each of these microassembly tasks is performed using a posebased visual control. To be able to control the microassembly process, a 3D model-based tracker is used. This tracker is able to directly provide the 3D micro-object pose at real-time and from only a single view of the scene. The methods proposed in this paper are validated on an automatic assembly of fives silicon microparts of 400 µm × 400 µm × 100 µm on 3-levels. The insertion tolerance (mechanical play) is estimated to 3 µm. The precision of this insertion tolerance allows us to obtain solid and complex micro electromechanical structures without any external joining (glue, wending. Promising positioning and orientation accuracies are obtained who can reach 0.3 µm in position and 0.2 • in orientation