A flexible joints microassembly robot with metamorphic gripper

ISSN： 0144-5154

Source： Assembly Automation, Vol.30, Iss.3, 2010-01, pp. : 240-247

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Abstract

Purpose ‐ The purpose of this paper is to report research which led to the realization of a robot for miniaturized assembly endowed with high-accuracy and high-operative flexibility. Design/methodology/approach ‐ The proposed solution is a microassembly system composed of a Cartesian parallel robot with flexure revolute joints and a modular gripper with metamorphic fingertips, capable of adapting their shape to different micro-objects. The fingertips are realized by electro-discharge machining from a sheet of superelastic alloy. Thanks to its modularity, the gripper can be arranged with two opposite fingers or three fingers placed at 120°. The fingers are actuated by a piezoelectric linear motor with nanometric accuracy. Findings ‐ The experimental results on the prototype are very interesting. The measured positioning accuracy of the linear motors is 0.5?µm; the end-effector positioning accuracy is lower, due to the non-perfect kinematics and hysteresis of the flexure joints; however, these effects can be compensated by the direct measurement of the end effector position or by visual feedback. The metamorphic design of the fingertips remarkably increases the grasping force; moreover, the grasping is more stable and reliable. Practical implications ‐ The introduction of this microassembly system can fulfil the needs of a wide range of industrial applications, thanks to its accurate positioning in a relatively large workspace. The cost of the machine is relatively low, thanks to its modularity. Originality/value ‐ The combination of Cartesian parallel kinematics, cog-free linear motors and superelastic flexure revolute joints allows one to obtain high-positioning accuracy; the metamorphic fingertips enhance the grasping effectiveness and flexibility.