Robotic microassembly for meso-scale application

Purpose – The purpose of this paper is to design and develop 14-degree of freedom (DOF) robotic micromanipulator with which LIGA devices and axle hole part can be both manipulated and assembled. Design/methodology/approach – The in-house robotic microassembly system is composed of a 6-DOF large motion serial robot with microgrippers, a hexapod six-DOF precision alignment worktable and a vision system whose optical axis of the microscope is parallel with the horizontal plane. A prism with special coating is fixed in front of the objective lens, thus, two-part figures can be acquired simultaneously by the microscope with 1.67 to 9.26 micron optical resolution. The relative discrepancy between the two parts can be calculated from image plane coordinate instead of calculating the space transformation matrix. A modified microgripper was designed to clamp meso-scale parts and its effectiveness was confirmed experimentally. Through the use of the other vision system, the insert action can be successfully manipulated. A laser ranger finder was integrated in this micro-assembly system to measure the assembly result. Findings – A new 14-DOF robotic micromanipulator, including eight axes automatically and six axes manually, has been developed for the assembly of LIGA meso-scale flat parts and axle hole parts. The microassembly system with coaxial alignment function (MSCA) system is able to concurrently manipulate all eight axes automatically and six axes manually. Originality/value – The robotic microassembly is applied in the assembly of meso-scale parts. The new capabilities of the MSCA will allow for the assembly of microsystems more efficiently and more precisely.

Development of a High Sensitivity Three-Axis Force/Torque Sensor for Microassembly

There is a growing need for multi-axis force torque (F/T) sensors to aid in the assembly of micro-scale devices. Many current generation robotic microassembly systems lack the force-feedback needed to facilitate automating common assembly tasks, such as peg-in-hole insertions. Currently, most microassembly operations use vision systems to align components being assembled. However, it is difficult to view high aspect ratio component assemblies under high magnification due to the resulting limited depth-of-field. In addition, this difficulty is compounded as assembly tolerances approach dimensions resolvable with optics or if the mating parts are delicate. This paper describes the development of a high sensitivity F/T sensor. Optimal design theory was applied to determine the configuration that would result in the most sensitive and accurate sensor. Calibration experiments demonstrated that the sensor can resolve down to 200μN and possibly less.

Construction of a 3D MEMS Microcoil Using Sequential Robotic Microassembly Operations

This paper describes the contruction of an out-of-plane MEMS (Micro-Electro Mechanical System) microcoil, by assembling together multiple surface micromachined microparts. A microgripper, which is bonded to the end-effector of a robotic workstation, is able to remove a micro-part from a MEMS chip, reorient the micro-part in space, move it to a secondary location, and join it to another micro-part. In this way, complex 3D microstructures can be assembled from a set of initially planar and parallel micro-parts. The microcoil is built from four loop elements, each 200 μm tall by 140 μm wide. The loop is closed by a base structure on the substrate, and the loops are spaced 50 μm apart. This four-loop microcoil is 200 × 140 × 200 μm in size. Using the described microassembly method, it is possible to fabricate microcoils with many loop elements of various sizes, spaced as closely as 25 μm apart.